Ecological issues

Ecological issues http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues Ecological issues facing Australia and Australians today Ecological issues http://www.natsoc.org.au/logo.png Water issues in Australia http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/water-issues-in-australia Water flows, water in cities, water reform

Nicky Grigg

Contents
Water flowing through Australian history
Land clearing can alter rivers irreversibly
Interlinked water stories: cities and agriculture
Water Reform in Australia

Water in Australia is a contentious topic; mentioning it in any social or professional context invariable uncovers a rich array of opinions, usually expressed with plenty of emotion.

Water flowing through Australian history

Water has been at the centre of nation-building projects such as the massive Snowy Mountains Hydroelectric Scheme (construction dates from 1949 and 1974), the Ord River Irrigation Scheme (constructed from 1963 to 1972) and C.Y. O’Conner’s Coolgardie Goldfields Water Scheme (constructed from 1989 to 1903) with its famous pipeline carrying water from the hills near Perth to Kalgoorlie.

An attempt to dam Tasmania’s Franklin River (Gordon-below-Franklin Dam project, proposed in 1978) sparked one of the most passionate and high-profile environmental movements yet seen in this country and contributed to the change of government in the 1983 Federal election. A proposed canal to transport water from the Fitzroy River in the Kimberly to Perth played a prominent role in the 2005 Western Australian State election.

Australian rivers in pre-European times were very different from the rivers we are now familiar with. For example, in south-eastern Australia, rivers had wider, shallower bed forms (rather than steep-sided channels), and were more likely to exist as chains of disconnected ponds during dry times. The flow through these rivers was highly episodic, characterised by long dry periods punctuated with bursts of higher flow. Floodplain vegetation was adapted to thrive in these conditions, experiencing occasional inundation during infrequent flood events.

Land clearing can alter rivers irreversibly

Expansion of European settlement in Australia marked the beginning of widespread land clearing, construction of dams and weirs, and the diversion of water for agricultural, domestic and industrial purposes. These have triggered changes to the quantity of water available in different locations and the speed with which water moves through the landscape.

Land clearing has been extensive in Australia. For example, the Western Australian wheatbelt has had approximately 85% of its native vegetation cleared for agriculture. Land clearing affects water in several ways. Rainfall landing on cleared land is more likely to move rapidly across the land surface, eroding valuable topsoil in its path and eventually creating erosion gullies. These processes have also seen the formation of steep-sided channels in river beds where once there were wide, shallow valley-bottoms that were able to retain more water in the landscape. The long-term ecological consequences of these changes are profound, and have greatly affected the diversity of plants and animals in these areas (e.g. floodplain plants, fish species, frogs, birds). Furthermore, good plant cover is vital for the delivery of high-quality drinking water (see box inset).

Why do we need healthy ecosystems for our water supply?

Before the Canberra bushfires, Canberra’s water was primarily sourced from the Cotter Catchment, located in Namadgi National Park. Water from this catchment was high quality drinking water that required very little treatment. By contrast, water from the ACT's source in NSW, the Googong catchment, required far more treatment before drinking. Unlike the storages in the Cotter catchment, Googong reservoir occupies a working agricultural catchment. Water drains agricultural and cleared land, and is more susceptible to pollution from nutrient and sediment runoff. In 2002, Googong water was ten times more expensive to treat than Cotter water. The bushfires in 2003 stripped the Cotter catchment of vegetation, and triggered an urgent need for new water treatment facilities to handle the increased runoff of topsoil into the dams. This higher level of water treatment will be required to treat Cotter water until the vegetation recovers.

The episodic and unpredictable nature of natural flows were not conducive to the water needs of European agriculture, domestic and industrial uses. Consequently many Australian rivers have been dammed or regulated in the name of water security, ensuring greater predictability of supply. In regulating rivers we have altered the ecology of both aquatic and terrestrial species in a myriad of ways. An extensive river assessment from the National Land and Water Resources Audit found that over 85% of river length is significantly modified from its original condition, and approximately one third of river length is impaired (substantial loss of river species when compared to undisturbed river reaches) .

Water quality has also been affected by clearing, irrigation and agricultural practices; water running off agricultural land carries fertilisers and pesticides, and where vegetation has been cleared, water runoff carries away valuable topsoil. Fertilisers and soil contain nutrients needed for plant growth, but in waterways the nutrients fuel algal problems in inland waters. If rivers deliver these nutrients to coastal regions they pose a threat to sensitive and highly valuable coastal ecosystems such as the Great Barrier Reef. Where land clearing has exacerbated salinity problems, the rivers draining these areas have experienced increased salt levels.

Ecosystems that have evolved over millennia have been transformed utterly within the space of two centuries, in many cases irreversibly. Recognition of this fact has driven the call for more ‘environmental flows’, that is, for the flow patterns in our rivers to be managed to bring them closer to pre-European patterns.

Interlinked water stories: cities and agriculture

What was the motivation for these profound human-induced changes to our landscapes and rivers? Overwhelmingly, the changes occurred to support agricultural production. Food and fibre production has driven the vast majority of land clearing decisions, and the regulation and diversion of rivers. Rivers have also been dammed for domestic and industrial supply, but this component comprises a very small part of the big picture. By far the largest demand on Australia’s water resources – 75% of all surface water use – comes from irrigated agriculture.

Nevertheless, domestic and industrial water uses are also important. Most capital cities and many towns are now approaching the limits of their local water supplies, and are actively enforcing water restrictions. The construction of new dams is highly unpopular and impractical, given that the best dam sites have already been taken. Alternative approaches are needed to supply a growing population with water. ‘Demand management’ is the name given to programs and policies aimed at reducing domestic water consumption. This can include incentive programs to install low-flush toilets, water-saving showerheads, front-loading washing machines, native (xerophytic) gardens, domestic water tanks and grey-water recycling facilities.

The contrast between the domestic and rural experience of water lies at the heart of many of the water issues in this country. Demand management in the city is promoted as saving money as well as saving water. But the relatively low price of water means that pay-back times for the installation of domestic rainwater tanks and grey-water recycling facilities are long indeed. However, even if suburban households were to invest in all water-saving measures, and conscientiously reduce their direct water use, they can remain blind to their indirect water use, for example, via the foods they buy.

The amount of water used in agricultural production means that our food choices can have much more impact on the water cycle than our domestic water use. It remains a surprisingly poorly researched area, but work that has been conducted in this field has demonstrated that the ‘embodied’ water in our daily purchases can far outweigh the direct water use in our households. For example, studies have estimated that approximately 700L of water are embodied in a typical one-litre carton of milk, attributable to the water requirements to grow pasture for dairy cattle. This is greater than the amount of water required to wash 10 loads of laundry in a front-loading washing machine!

Summarising, much damage to our landscapes and waterways has been in the name of agriculture, which is primarily driven by the purchasing choices of city-dwellers. In cities we are encouraged to use less water, and governments are spending money on imposing water restrictions and providing incentive programs for households to adopt more water-wise measures. In the meantime, the water use embodied in the food and material items we purchase, remains hidden to us. Historically the price of water in rural areas has been far below city prices, resulting in little price incentive to use less water in agricultural systems. Water has recently been brought into focus by prolonged drought which has triggered distress and lost production in agricultural regions, and the enforcement of water restrictions in most capital cities.

Water Reform in Australia

All these factors have combined to drive a suite of profound changes to water management in this country. We are in the midst of exciting times, where water is a hot political topic and real changes are being made. These changes have been a long time coming, and have important historical roots, including Council of Australian Governments (CoAG) agreements on water dating from 1994, the introduction of ‘The Cap’ in allocating water within the Murray-Darling in 1995, and a group of influential scientists (The Wentworth Group) who promoted a ‘Blueprint for a National Water Plan’ in 2003.

In 2004 an Intergovernmental Agreement was signed on a National Water Initiative, which is administered by the newly formed National Water Commission. The National Water Commission is an independent statutory body in the Prime Minister’s portfolio, and it reports to the Council of Australian Governments. The National Water Initiative seeks to consolidate all former water reforms, and form a shared, national approach to water. This includes the development of robust water accounting methods, the establishment of national markets for trading water and water planning processes so that different parties can reconcile competing water uses (e.g. urban vs rural, the environment vs agricultural production). The Chairman of the National Water Commission, Ken Matthews, warns that "there are no silver bullets … water reform is a complex, hard slog".

Further interesting challenges ahead include: the very real potential to reuse sewage and stormwater (possibilities that currently meet a lot of resistance in Australian cities); the future of Australia’s northern rivers, which will be under increasing pressure to be developed due to their large, currently unregulated flows; and how to prepare for the unknown impacts that global climate change will have on the Australian water cycle.

The recent developments in water policy demonstrate that ideas on water in Australia are becoming more sophisticated, informed and less blinded by populist myths (e.g. ‘turn the rivers inland and make the desert bloom’). Droughts bring out calls for simplistic ‘silver bullet’ solutions to ‘drought-proof’ the nation. In 2003 John Williams (then chief of CSIRO Land and Water) wrote an eloquent plea to ‘myth-proof’ the nation, asking us to once and for all abandon naïve faith in large infrastructure plans to divert rivers or build massive dams. The infrastructure needed to tackle these problems is more subtle and complex; we need social, economic, legal and democratic infrastructure that allows us to consider the needs of communities, agriculture, industries and the environment, and allocate water effectively in times of drought or plenty.

This paper as a [136KB pdf]

2012-06-18T14:56:39+10:00 2012-06-18T14:56:39+10:00 roba Nuclear weapons, nature and society http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/nuclear-weapons-nature-and-society

Dr Sue Wareham

Nuclear weapons represent mankind’s ultimate confrontation with the natural environment that sustains us. The purpose of these weapons is wholesale destruction on a massive scale, which affects most forms of life. No other single human creation has such potential for harm.

Such is the threat to life posed by nuclear weapons that the International Court of Justice, the world’s highest legal authority, in its 1996 landmark ruling on the general illegality of these weapons, stated:

"The destructive power of nuclear weapons cannot be contained in either space or time. They have the potential to destroy all civilisation and the entire ecosystem of the planet.”

There are two overwhelming threats to life on earth as we know it. They are climate change and nuclear weapons.
The Governor of California Arnold Schwarznegger said in October 2007:

“The attention focused on nuclear weapons should be as prominent as that of global climate change…..A nuclear disaster will not hit at the speed of a glacier melting. It will hit with a blast. It will not hit with the speed of the atmosphere warming but of a city burning.”

It is certainly not Schwarznegger’s intention, nor mine, to divert attention from the need to avert further climate change. That must remain an urgent imperative. However we must also recognise the gravity of the threat posed by the world’s 26,000 nuclear weapons, and respond with a similar sense of urgency. If we do not, these weapons will be used again, with catastrophic consequences.

Some of the human and environmental implications of the following will now be briefly addressed:

1. The raw material - uranium

2. Nuclear weapons testing

3. Nuclear weapons facilities and their environs

4. The biological effects of radiation exposure

5. The use of nuclear weapons

6. Climatic effects of nuclear weapons use

7. Nuclear waste

8. The role of human error, human malevolence and human wisdom.

1. The raw material – uranium

Nuclear weapons require either enriched uranium or plutonium as their fuel. As plutonium is found in only minute quantities in nature, virtually all the plutonium in the world is derived from nuclear reactors, with uranium as the original reactor fuel. Therefore uranium is the starting point for all nuclear weapons.

Uranium mining and milling produces enormous volumes of tailings, or waste, which contain over 85% of the radioactivity of the original ore. (This is because they contain radioactive breakdown products of uranium that have accumulated over many thousands of years.) One of the major products is thorium-230, whose half-life (the time taken for half of a radioactive substance to decay) is 75,000 years. Theoretically, tailings dams contain this waste, but claims that they will do so for tens or hundreds of thousands of years are not credible.

A severe example of the impact of uranium mine tailings is at the Jadugoda mine in India. A study conducted in 2007 by Indian Doctors for Peace and Development found increased rates of congenital deformities, cancers and sterility in those living in the vicinity of the mine.

One of the lesser-known problems of uranium mining (and in fact the whole of the nuclear industry) is its enormous water requirements. The Olympic Dam uranium and copper mine at Roxby Downs in South Australia currently uses 35 million litres of water from the Great Artesian Basin every day (for which BHP Billiton pays nothing), and an expansion is planned.

Uranium mining also requires large amounts of electricity. It was reported in March 2008 that the greatly expanded Olympic Dam mine would need nearly half of SA’s current electricity supply when it reaches full production in 10 years time, a staggering statistic for an industry that claims to be part of the solution to our energy crisis.

2. Nuclear weapons testing

Approximately 1,900 nuclear tests have been conducted, of which just over 500 were in the atmosphere, underwater or in space, and the remaining 1,400 were underground. Radioisotopes produced by nuclear tests, such as carbon-14, caesium-137, strontium-90 and plutonium-239 (half-lives 5,730 years, 30 years, 28 years and 24,400 years respectively), pose risks to current and future generations by ingestion, inhalation and external radiation. Test sites around the world remain contaminated, including the Maralinga site in South Australia.

In 1991, International Physicians for the Prevention of Nuclear War and the Institute for Energy and Environmental Research published “Radioactive Heaven and Earth: The health and environmental effects of nuclear weapons testing in, on and above the earth”. This study estimated that the radiation exposure from carbon-14 (integrated over infinity) would result in a total of 2.4 million human cancer deaths. The study concluded that “Many aspects of nuclear weapons testing have been characterised by a disregard, sometimes willful, of public health and environment”.

In the US, in 1997, the National Cancer Institute revealed that atmospheric tests at the Nevada site resulted in significant contamination of the nation’s milk supply with iodine-131, with estimates of 11,000 to 212,000 excess thyroid cancers as a result.

3. Nuclear weapons facilities and their environs

Evidence has accumulated of major health, safety and environmental problems at nuclear weapons complexes around the world. This is most apparent in the two nations that are responsible for approximately 96% of the world’s nuclear weapons, the USA and Russia.

In the US, Physicians for Social Responsibility has reported on the task of dealing with the toxic and radioactive legacy of 50 years of nuclear weapons production, which “is said to be the most technologically challenging and costly public works project ever conceived”. The US Department of Energy has estimated that minimal remediation of the nuclear weapons complex will cost $230 billion over 75 years. Even at this level of expenditure, many sites and buildings will remain out-of-bounds for human access for the foreseeable future.

At Hanford, the former plutonium production complex in Washington state, approximately 800 billion litres of low-level liquid radioactive waste were discharged directly into the soil over a 50-year period. Groundwater at Hanford has been contaminated with cesium-137, iodine-129, plutonium-239, heavy metals and other radioactive or toxic substances. High-level radioactive waste at Hanford is stored in 177 underground tanks, 70 of which have leaked. Hanford is possibly the most contaminated site in the US nuclear weapons complex.

In Russia, the situation is probably worse than in the US. Vast quantities of radioactive waste, including nuclear reactors, from Soviet and Russian nuclear-powered ships and submarines were dumped into the Pacific and Arctic Oceans.

The Mayak complex in the eastern Ural mountains (also called Chelyabinsk-65, or Kyshtym) is the largest of the former Soviet Union’s three plutonium production centres. The Chelyabinsk-65 military complex covered as much as 2,700 square kms in the 1950s. The highly contaminated site lies on a region of interconnecting lakes, marshes and waterways at the headwaters of the Techa River.

Between 1948 and 1956 radioactive waste from the Mayak nuclear complex was poured straight into the river, the source of drinking water for many villages. Cesium, strontium and other liquid radioactive waste that had been dumped was detected in the Arctic Ocean nearly 1,000 miles away. The waste discharge point at Lake Karachay in the Ural Mountains remains so radioactive that a person standing there would receive a lethal dose of radiation in less than one hour.

In 1957 there was an explosion of high-level liquid nuclear waste at Kyshtym, contaminating 20,000 square kms. Some villagers were evacuated, but many were not.

While the USA and the former Soviet Union, due to the sheer number of nuclear weapons produced, present by far the most disturbing pictures of radioactive contamination from weapons production , the problem is not confined to those two countries. Radioactive contamination globally from nuclear weapons production will take an incalculable but heavy human and environmental toll for a very long time.

4. The biological effects of radiation exposure

Studies on both plants and animals have repeatedly shown that exposure to ionising radiation causes genetic mutations, and we know that mutations can lead to the development of cancers. Cancer rates among Hiroshima and Nagaskai survivors are significantly increased, and, over 60 years after the bombings, they have not yet reached their peak. Rates of microcephaly and intellectual disability were also increased among those who were in utero at the time of the bombings.

It is important however to understand the difficulties encountered in assessing the biological effects of radioactivity, especially low-level radioactivity. Attributing with certainty a specific cancer to a specific episode of radiation exposure is generally not possible, for a number of reasons:

cancers may occur decades after the exposure;

there is no way of distinguishing a cancer caused by radiation from any other cancer;
cancer is a common illness, with many other possible triggers;
individuals’ susceptibility to cancer will vary according to their health and genetic inheritance;
radiation can spread over large distances, depending on weather patterns, and be dispersed in such a fashion that determining the dose received by specific people or animals is extraordinarily difficult.

Hard statistical evidence of genetic damage from radiation exposure being passed on to progeny in humans has long been lacking, despite overwhelming evidence of radiation-induced mutations in plant and animal experiments. Specifically, such damage in the descendants of Hiroshima and Nagasaki survivors has not been demonstrated thus far. However new evidence from New Zealand on survivors of the 1957-58 UK Operation Grapple nuclear tests in the Pacific shows three times the frequency of total chromosome changes (translocations) in the test veterans as in a control group. Statistically, this is very significant, and indicates the potential to result in intergenerational effects. More research in this area is needed.

5. The use of nuclear weapons

Nuclear weapons are indiscriminate in every sense, and the ultimate weapon of mass destruction. Their effects cannot be contained in time or space, nor do these weapons discriminate between children and adults, humans and any other species, combatants and non-combatants or according to any other criteria.

The weapons that destroyed Hiroshima and Nagasaki were approximately 15 and 21 kilotons respectively (a kiloton being 1,000 tons of TNT equivalent). The two cities were destroyed. Nuclear weapons built since then have been up to many megatons (million tons of TNT equivalent). The largest US and Soviet nuclear tests were, respectively, a 15 megaton test (codenamed Bravo) in 1954, and a 50 megaton test in 1961.

Nuclear weapons cause an initial intense (often blinding) flash of light, then an enormous fireball, which generates heat in the order of tens of millions of degrees centigrade. The fireball rises and cools, forming the characteristic mushroom cloud appearance. A powerful blast wave causes the collapse of buildings and flying debris. Firestorms, fanned by hurricane force winds, break out. In addition, there is an electromagnetic pulse that destroys electrical equipment. Initial radiation is emitted at the moment of the explosion, and causes radiation sickness.

Radioactive particles called fallout will be present immediately, but they can also travel the globe and have very delayed effects, causing increased cancer rates and genetic changes, as explained above.

6. Climatic effects of nuclear weapons use

Recent studies have resurrected the “nuclear winter” fears of the 1980s. It is estimated that the use of just 100 Hiroshima-sized weapons in urban areas, for example a war between India and Pakistan where each side used 50 weapons, could cause severe global climatic consequences. Fires ignited would release copious amounts of light-absorbing smoke and debris into the upper atmosphere, causing persistent surface cooling even a decade later. In such a scenario, there would be decreases in growing seasons in many of the most important grain producing parts of the world, with severe reductions in food production.

A scenario of this magnitude could lead to a total global death toll of one billion from starvation alone, major epidemics of infectious disease, and immense potential for war and civil conflict.

7. Nuclear waste

Not a single country, anywhere, has in place a satisfactory long term solution to the problem of nuclear waste. Unless a solution is developed, all future generations of humans will inherit this problem.

In the US alone, nuclear waste has accumulated at 120 sites around the country. This includes approximately 55,000 tons of high level waste from civilian reactors, and 15,000 tons from nuclear weapons production. All of them are intended as temporary sites, but there is currently nowhere for the waste to go. The proposed Yucca Mountain site has experienced prolonged delays, and is still not approved, despite many billions of dollars of research.

Because the nuclear waste problem is not resolved, some eyes scan the globe for a place that is less densely populated, in which it could be dumped, and look to Australia as a possibility. While both the previous and current governments have ruled out Australia accepting high-level waste from other countries, it is likely that pressure for such a facility will surface from time to time. Australia already has an unresolved problem of what to do with our low and medium level nuclear waste, including reprocessed waste that will return here from France and Scotland (Dounreay) from about 2011.

8. The role of human error, human malevolence and human wisdom

Nuclear weapons have not been used (except as a political tool) since 1945. Some commentators attribute this to the role of “deterrence”, the notion that nuclear devastation is so unthinkable, and the threat of nuclear retaliation so unacceptable, that the weapons will remain forever unused. These assumptions are flawed.

They assume that leaders will always, without exception, care what happens to their own country and all its people. We can think of instances where this is not the case. And they assume that no major errors of judgement will be made, nor accidents in the monitoring and oversight of nuclear weapons will occur. This is contrary to what we know of human nature, which is that people make errors, especially when working under intense pressure. There are well-documented instances where the world has come frighteningly close to nuclear conflict.

During the 1962 Cuban Missile Crisis, there were huge miscalculations on both sides. Former US Defense Secretary Robert McNamara says of those 13 days, “We were a hair’s breadth from absolute disaster.”

The 1996 report of the Canberra Commission on the Elimination of Nuclear Weapons stated, “The proposition that nuclear weapons can be retained in perpetuity and never used – accidentally or by decision – defies credibility.”

We also know however that humans have profound capacity for wisdom and discernment. Jonathan Schell reminds us that our past need not determine our future:

“Whether [nuclear weapons] are merely a monstrous leftover from a frightful era that has ended, and will soon follow it into history, or whether, on the contrary, they are seeds of a new, more virulent era, in which nuclear weapons are held more widely and rooted more deeply, is not a matter of prediction; it is a matter of choice.”

November 2008

Notes:

1. http://www.nuwinfo.se/black-magic-at-jadugoda2007idpd.html

2. www.foe.org.au/campaigns/anti-nuclear/issues

3. BHP to use half of state’s electricity. The Australian, March 27, 2008

4. Apex Press, New York, and Zed Books, London

5. Steven L Simon, Andre Bouville, Charles E Land. Fallout from nuclear weapons tests and cancer risks. American Scientists online, Vol 94, No 1, p 48

6. http:www.psr.org/site/PageServer?pagename=security_legacy_military_weaponscomplex
MGS, March 1995, page 28

7. Nuclear Wastelands: A Global Guide to Nuclear Weapons Production and its Health and Environmental Effects. MIT Press 1995. p 2.

8. R E Rowland et al. Elevated chromosome translocation frequencies in New Zealand nuclear test veterans. Cytogenetics and Genome Research 121:79-87 (2008)

9. Nuclear pursuits. Bull At Scientists. Sept/Oct 2003, p72

10. Robock A et al. Climatic consequences of regional nuclear conflicts. Atmospheric Chemistry and Physics Discussion 2006; 6 :11817 - 11843

11. I Helfand. An Assessment of the Extent of Projected Global Famine Resulting from Limited, Regional Nuclear War. Presented at “Nuclear Weapons: The Final Pandemic” conference. October 3-4, 2007, London.

12. A Macfarlane. Stuck on a solution. Bull At Scientists. May/June 2006.

Top

President, Medical Association for Prevention of War (Australia)

2012-06-18T14:55:00 2012-06-22T09:23:58+10:00 roba Soils - sodic and acidic http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/soils-sodic-and-acidic Soil sodicity, soil acidity

Alice Thompson

Contents
Sodicity

Processes
Impacts
Management

Soil acidity

Processes
Impacts
Management

Further reading

For further information see:

The Australian Academy of Science’s Nova websites

(1) www science.org.nova/071/071box01.htm
(2) www science.org.nova/035/035key.htm
(3) www.science.org.au/nova/035/quirk.htm

Also a website of the Australia State of the Environment Report 2001

(4) www.deh.gov.au/soe/2001/land/land04-3.html

Born and raised in Canberra, Alice Thompson was brought up with an appreciation of, and interest in the environment, leading her to study at the Australian National University, majoring in Geography/Human Ecology and Population Studies, and her involvement in the Nature and Society Forum (NSF). She now lives in Sydney where she currently pursues a career in Government working for the NSW Office of the Australian Bureau of Statistics (ABS). Before joining ABS Alice was employed by NSF as a Research Officer to prepare reports on important ecological issues in Australia.

This paper as a [109KB pdf]

2012-06-18T14:55:00 2012-06-20T15:42:36+10:00 roba Soils - salinity http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/soils-salinity Soil salinity, dryland salinity

Alice Thompson

Contents
Introduction
What is salinity and salinisation?
Impacts of salinity
Extent and costs of salinity in Australia
Management

Introduction

Salt is an inherent part of the Australian landscape, occurring naturally in many environments. Enormous stores of salt have accumulated in the soil, groundwater and surface waters through the long-term influence of natural processes. Over hundreds of thousands of years, the native vegetation has evolved to successfully cope with the low rainfall and high salinity levels characteristic of the Australian environment. During the past 200 years, however, human activities have dramatically disrupted the natural hydrological balance in many areas, with significant consequences for the distribution of salt in the landscape. This has led to severe degradation of both natural and agricultural environments.

The salinisation of the land and water is now seen as a very serious threat to the health and utility of Australia’s rivers, soil and vegetation. Human-induced salinisation is also of concern in many other countries around the world.

On the basis of current predictions, the total area of land affected by human-induced salinity in Australia is expected to increase dramatically over the next few decades, unless effective solutions are developed and implemented. These solutions would involve significant changes to our present systems of land use and management, as well as a major shift in approach, from one that focuses on the symptoms of salinisation to one that addresses the causes. The damage caused by human-induced salinisation is already creating serious economic and social impacts in rural and urban communities around Australia, and these will worsen unless effective remedial action is taken.

What is salinity and salinisation?

Salinisation is a process that results in an increased concentration of soluble salts in soil and water. Of these salts, sodium chloride, or table salt, is the most common. Salinity is the state of soils that have a high concentration of such salts.

All continents have a wide distribution of what is known as primary salt-affected soils. Primary salinisation is when salts accumulate in the soil and groundwater of an area over a long period of time due to natural processes. For example, salt is released, re-deposited, and gradually concentrated in soils and surface and sub-surface waters through the weathering of rocks and sediments in which salts were incorporated at the time of deposition. In Australia, the weathering of sediments that have been periodically inundated or deposited by rising sea levels has been a major source of salt. Salt can also be caught in sea-spray and carried on wind as dust or rain and deposited inland, where it steadily accumulates over many thousands of years.

These natural processes create substantial concentrations of salt in the landscape, stored either in the groundwater, or in the soil just above the watertable. Many factors influence where the salt is accumulated and stored, including the nature of the parent material and the climate. In arid regions, where rates of evaporation exceed rainfall, there is enough sub-surface water percolating through the soil to dissolve and concentrate salts, but not enough to leach them from the soil profile below the root zone of vegetation. This situation is exacerbated by the flatness of the Australian continent and subsequent sluggish nature of its largely inland drainage system, resulting in the formation of extensive natural salt deposits across much of the arid and semi-arid interior.

Over time, through the processes of biological evolution, the native vegetation of Australia has adapted to the dry and salty conditions. This has involved the development of perennial trees, woody shrubs and grasses with deep and dense root systems which allow only a little water to leak past the root zone into the groundwater. In healthy ecosystems, naturally occurring salt in the soil or sub-surface waters is concentrated by plants through evaporation and transpiration. These salts are then slowly leached downwards and stored beneath the root zone. These processes maintain the hydraulic and salt balance of catchments – where the gradual discharge of salt and water from the deeper soils of the landscape is roughly equal to the input of salt and water to the catchment.

Various human activities have disrupted this natural hydrological balance, changing the distribution of salt in the landscape. Salinity problems occur when more water is added to the groundwater system than is discharged under natural conditions, as often occurs when the natural vegetation has been removed. This causes the level of the watertable to rise, bringing stored salts to the soil surface and waterways. Evaporation then draws the rising waters to the soil surface through capillary action, which concentrates the salts at or near the surface, affecting the root zone of native and introduced vegetation. This process is known as secondary salinisation (Figure 6.1)

Figure 7.1 Model of catchment hydrology demonstrating salinisation process

soil salinity1a

soil salinity1b

Diagram 1
A basic model of catchment hydrology showing how the destruction of deep-rooted perennial native vegetation in one area can bring about salinisation quite some distance away. The precise picture of disturbed groundwater systems, waterlogging and salinity varies across Australia, but the basic cause of dryland salinity - land clearing - remains the same.

Source: http://www.acfonline.org.au/docs/salt/salt_chapter1.pdf

Human activities, in particular agriculture, are largely responsible for these changes to the hydraulic and salt balance of catchments. Both dryland and irrigated agricultural practices and their associated activities have greatly contributed to the excessive recharge of groundwater and concentration of salts in the soil and surface water (see Box 6.1).

Box 7.1

Human activities that contribute to salinisation of soil and water

SOIL

Activities that alter movement of water through soil

clearance of deep-rooted vegetation
replacement of native vegetation with shallow rooted crop and pasture species
compaction and disruption of soil structure
storage, conveyance and disposal of surface waters
addition of impediments to natural drainage patterns

Activities that increase salinity levels in soil

application of saline irrigation waters
disposal of saline wastewaters on land
upward movement of water due to excessive additions to the watertable

GROUNDWATER

Activities that disrupt natural recharge rates

clearance of deep-rooted vegetation
urban development
paving of surfaces
irrigation with surface water
leakage from irrigation channels
leakage from farm dams and other surface reservoirs

Activities that increase salinity levels in groundwater

disposal of saline or liquid wastes in basins or wells
disposal of solid wastes that contain soluble salts in landfill that can be leached by rainfall into the groundwater, or buried beneath watertable
extraction of groundwater, causing intrusion of saline water from another aquifer, and disrupting the saline/freshwater interface
pumping of groundwater, or the use of saline surface water for irrigation- salinity of groundwater is increased if water returns to aquifer as recharge

SURFACE WATERS-

Activities that alter the flow of water

diversion of water for consumption or inter-basin transfer resulting in decreased flow
loss of water through evaporation of reservoirs
changes in land use, soil and vegetation resulting in increased stream flow
modification of instantaneous flows of water through the construction of reservoirs, weirs, dams and other changes to channels

Activities that increase salinity levels in surface waters

changes to diversions and return flows, in addition to the gains and losses from groundwater in adjoining strata, especially in irrigation areas can increase salinity load of rivers and streams
changes to management of soil and vegetation in non-irrigated areas can increase recharge of groundwater and discharge of salt into rivers and streams
construction of weirs and reservoirs can increase leaching of salts downstream, and displace saline groundwater from underlying strata into rivers and streams

The telltale signs of land affected by salinity are dead or dying trees and declining vegetation. It can also be accompanied by the appearance of plants that are especially tolerant to salts. In areas of low rainfall, where vegetation loss results in soil erosion, dry saline scalds can appear as bare patches with little or no vegetation or topsoil. In areas of irrigation, saline soils develop where the watertable is within 2 metres of the surface, and waterlogging and saline seepages can appear if the watertable breaches the surface. Seepages occur where the saline groundwater intercepts the surface, usually on the break-of-slope, or in valleys, flats, creekbeds and lower areas in the landscape. This causes waterlogging of these areas and the death of vegetation, often accompanied by an increase in salt-tolerant vegetation.

Impacts of salinity

The salinisation of soils and surface water and groundwater has significant effects on the surrounding environment, and also creates serious economic and social problems for both rural and urban communities.

High soil salinity adversely affects plant growth of both native and introduced crop and pasture species. This is due to the toxicity of the salt ions, as well as the general osmotic effect of the soil around the roots of the plant, which reduces the ability of the plant to absorb water from the soil. As noted above, high soil salinity can prompt the appearance of salt-tolerant species, which, like Sea Barley Grass and Spiny Rush, are often weed-like and unpalatable to stock.

Increased salinity poses a significant threat to the health and wellbeing of many ecosystems, and to biodiversity as a whole. It can destroy remnant vegetation, leading to the disappearance of animal species that are dependent upon this vegetation for habitat. It also impacts upon the vegetation along river banks that is critical to bank stability, and that provides wildlife corridors. It also threatens the integrity of wetland areas. All of these impacts have serious flow-on effects on the growing industry of eco-tourism.

High salinity not only makes the soil chemically toxic for plants, but it also affects the soil’s physical properties. Saline soils are often associated with a secondary process of alkalinisation, a condition referred to as sodicity. This causes soil to swell and disperse into fine particles that block soil pores when dry. Sodic soils are often hard-setting, susceptible to erosion, water-logging and poor aeration, and the absorption of rain is reduced. They will be discussed in the next chapter.

Saline soils are also prone to erosion as a result of the death of vegetation that would otherwise have stabilised them. If left untreated, saline areas generally become bare and compact, and create conditions that lead to sheet and gully erosion. This results in huge salt and sediment loads in watercourses, degrading lower lands and reducing water quality downstream.

Highly saline water is quite unpalatable for humans and stock. It can also be toxic, due to the presence of particular ions (manganese and sulphate ions) causing gastro-intestinal irritation in livestock, and it can interfere with reproduction and contaminate milk products. Increasing concentrations of salt in streams and basins also have significant impacts on aquatic ecosystems like wetlands, and on other users who extract water from the environment, including for domestic consumption, mining, manufacturing and irrigation purposes.

Salinity causes the loss of productive land area, loss of production, and increased costs faced by landholders in protecting land and surface waters from salinisation, and in changing to alternative, more sustainable land uses. It is also causing significant impacts and costs to regional infrastructure. Rising watertables damage roads, and 34 per cent of state roads and 21 per cent of national highways in NSW are currently affected by increasing salinity. Rising saline damp affects many buildings and other structures by eroding bricks, mortar and concrete. Saline water corrodes the foundations and materials used in the construction of bridges, sewerage pipes and water maintenance equipment, and it sometimes results in the loss of local water supplies.

Salinisation can cause a general reduction of income and expenditure of rural families and communities, with significant social and economic implications for regions as a whole. These impacts are more notable in small rural towns, where opportunities for adjustment of the local economic base are limited.

Urban areas, for example Wagga-Wagga and some outer suburbs of Sydney, are also beginning to be seriously affected, as saline soils and waters are causing the decay of house and building foundations, and structural damage from rust in motor vehicles. Salty water can damage and corrode hot water systems, household appliances, plumbing and septic systems, and require an increased use of soaps and detergents. Gardens and lawns suffer from the effects of salinity, and become difficult to maintain. Other effects of increasing salinity on urban areas include damage to ovals, parks, footpaths, cemeteries, sewerage pipes and industry. Ultimately, it results in a reduction of public and private property value.

Extent and Costs of Salinity in Australia

Although awareness of increasing salinisation of land and waters has increased considerably over the past few decades, the problem has also worsened. Some scientists maintain that salinity, particularly dryland-induced salinity, will prove to be an almost intractable problem.

Saline soils account for 6 per cent of the land area in Australia, with over 2.5 million hectares of land currently affected by dryland salinity. Without effective treatment, the area of land affected by dryland salinity is predicted to increase to 15 million hectares in the next fifty years. Around 4.5 per cent of presently cultivated land has problems with salinity, some of it in the potentially most productive agricultural regions in the country.

Over 70 per cent of Australia’s saline soils are in Western Australia, with 1.8 million hectares of land currently affected. Most of this salt originated from the ocean, and was brought in via the atmosphere and deposited inland as rain or dry fall-out. The removal of native vegetation for dryland agriculture has considerably increased the recharge of the saline groundwater, bringing salt to the surface soils and streams. Over half of the State’s waterways are already saline, brackish, or of marginal quality. It is estimated that the area in WA affected by dryland salinity will double over the next twenty years before equilibrium is reached.

In South Australia, over 400 000 hectares of land are showing the effects of dryland salinity, and it is now present to a degree in all agricultural districts in the State. The area affected could potentially increase to around 600 000 hectares. Twenty percent of surface waters are already above desirable salinity levels for human consumption. According to a recent audit, 900 000 hectares of the small area of South Australia that is contained in the Murray-Darling Basin is experiencing rising groundwater, with 116 000 hectares likely to be affected by salinity by 2050.

Irrigated and dryland-induced salinity cover an area of approximately 120 000 hectares in both Victoria and New South Wales. If effective action is not taken, this area is expected to increase to 1.2 million hectares in Victoria, and 5 to 7.5 million hectares in NSW. In Tasmania 18 000 hectares, or 2 per cent of cleared agricultural lands, are affected by salinity, with significant risks of further areas becoming affected. Salinity is also a growing problem in Queensland as a result of the rapid rates of clearance over the past 60 years. Already 10 000 hectares of land are affected by dryland salinity.

Across the Murray-Darling Basin, it has been estimated that salt mobilised to the land surface will increase from 5 million tonnes a year in 1998 to 10 million tonnes in 2010. The movement of salt is likely to shift from irrigation-induced sources to dryland catchment sources, as irrigation-induced salinity can stabilise itself over time while dryland salinity processes tend to operate over longer periods.

The salinity levels in rivers and surface streams within the Basin are also increasing. It has been predicted that within 50-100 years the average salinity of the lower river Murray, Macquarie, Namoi and Bogan rivers will probably exceed the World Health Organisation’s threshold for desirable drinking water quality.

The full economic costs of land salinisation are difficult to calculate due to the often indirect nature of impacts, but it has been suggested that it costs the nation as a whole more than $150 million per year. Some estimates have been even higher; placing the overall cost of dryland salinity alone at $700 million in lost capital value of land; $130 million annually in lost agricultural production; $100 million annually in damage to infrastructure; and at least $40 million in loss of environmental assets.

Management

Current approaches to the management of salinity in Australia concentrate on the need to minimise the mobilisation of salt by restoring the water balance and ensuring catchments are not "leaking" water in ways which mobilise salt. This has largely been addressed through the development of engineering schemes and drainage programs, of which a wide range of technical options over various scales is available. Many of these have been quite effective in reducing accessions to groundwater, lowering water tables, and reducing the discharge of saline water into rivers and streams. However, these technical solutions often require considerable initial outlays of finance, and tend to focus on the symptoms rather than the causes of salinity. Many of these techniques involve the interception of saline water that then needs to be disposed of, displacing the problem elsewhere. The scale of the problem calls for more effective and long-term approaches.

Increasing concern and evidence of the serious threats that dryland and irrigated salinity represent to land and water quality have led to a number of government initiatives within and between the states in Australia.

Water pricing has evolved from the need to make users pay the true cost of their water resources. Previously, as in most other countries, water for irrigation, has been underpriced, and often heavily subsidised by governments. This has led to the inefficient use of water supplies, and the development of such problems as waterlogging and salinity. Through policies of ‘user pays’, direct charges on, for example, volume of water used or area of land irrigated, water pricing can potentially increase irrigation efficiency, reducing the artificial recharge of groundwater.

The inefficient use of water resources has also led to the development of policies like transferable water entitlements (TWE), which aims to allocate water resources more effectively. TWE is a mechanism through which a market for water can operate by allowing water entitlements to be bought and sold without any attachment to land. It is hoped that this will transfer water resources to higher value uses and decrease use of water on land not suited to irrigation. TWE should result in the increased adoption of water-saving technologies, as water that can be saved, can be sold.

Salinity, along with other catchment-based issues in which the underlying processes are complex and the impacts occur some distance away from the cause of the problem, has highlighted the need for a more integrated approach by State and Federal Governments.

A number of catchment management models have been developed and implemented. Probably the most well-known catchment management entity in Australia is the Murray Darling Basin Commission, which covers an area of 1.6 million square kilometres across four states and the Australian Capital Territory, making up the largest integrated catchment management program in the world (SOE 1996:36). It is a structure where the Commonwealth Government, and the four state Governments within the basin (NSW, Vic, SA, Qld), along with the local and regional communities, work together to maintain and improve water quality. This aim is achieved through research, control and reversal of land degradation including salinity, the protection and rehabilitation of the natural environment, and the conservation of natural heritage.

In 1998, the Murray Darling Basin Ministerial Council adopted the Salinity and Drainage Strategy, which set out specific targets against benchmark conditions for the reduction of salinity. This strategy is set within a framework of joint action between all the governments within the basin, except Queensland. It defines the rights and responsibilities of all governments involved, as each state is responsible for actions significantly affecting river salinity within its jurisdiction. It aims to improve the water quality of the river Murray for all beneficial uses, including the environment, and to control and minimise land degradation. It also aims to conserve the natural environment of catchment valleys and to protect sensitive ecosystems from salinity. Major actions under the management plans include drainage programs, reduction of seepage losses from irrigation, re-use systems for drainage from farms, land forming, adoption of farm plans using best practice, groundwater control by pumping, improved water management of wetlands, tree and deep-rooted vegetation planning. The most significant achievement of the strategy so far has been the reduction of river salinity without limiting the rehabilitation of degraded lands, and the undertaking of drainage programs to control the rise of groundwater.

Although engineering solutions, policy tools, and the integrated catchment management approaches of the State and Federal Governments have made significant headway in addressing the salinisation of land and water resources, ultimately salinisation will not be manageable without substantial changes to our existing dominant farming systems. This will require significant shifts in land use, as management priorities evolve from focussing on the symptoms to dealing with the causes. In some circumstances, it will need to be recognised that amelioration may be impractical or too expensive, and changed land use to manage and live with salted lands and saline rivers is the only option.

There are many agricultural practices that actively reduce the rate of recharge to groundwater systems, including the replacement of shallow rooted pastures and crops with deep rooted varieties, changing cropping and irrigation strategies, improved grazing management systems, use of suitable improved pasture species and maintenance of pasture quality, and the use of perennial pastures. There are new forms of cereals, pulses, oilseeds and forages selected or bred for characteristics that reduce deep drainage. There are also assessment tools for the placement of trees and other vegetation for optimal effect, and tools for land managers to monitor leakage. Revegetation of recharge areas and saline lands, and the development of agricultural production systems utilising salt-tolerant plants has been a major area of research in recent years. Tree-based land management strategies can reduce recharge of groundwater and the spread of salinity, providing a productive use of salt-affected land, and potential for use in saline drainage water reuse schemes.

Dryland and irrigated-induced salinity together pose considerable threats to the integrity of our natural ecosystems, and to human social and economic systems as well. The time scales over which salinity establishes itself, spreads and has effects can be long and very difficult to contain or reverse. Although the impacts and costs of secondary salinity have been considerable, these issues have provided a necessary ‘spur’ for the development of more sustainable farming systems.

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2012-06-18T14:50:52+10:00 2012-06-18T14:50:52+10:00 roba Soils - erosion http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/soils-erosion Wind erosion, water erosion (add table)

Alice Thompson

Processes and types of soil erosion

Water erosion

The extent of erosion

Management of erosion

Further reading

Soil erosion is defined as the dislodgement of soil particles and their removal from their original position. It is a natural process and has been fundamental in the shaping of the Australian landscape over geological timescales. Places like the Kimberley Ranges are a dramatic testimony to the effects of erosion over long periods of time. However, human activities, and in particular agriculture, have greatly accelerated the rates of soil erosion.

Soil erosion is a major issue for Australian agriculture and catchment management. The rate of soil production in Australia is very low, and in many areas it is greatly exceeded by the rate of soil loss. Managing soil erosion can be difficult and costly.

This paper discusses the different types of water and wind erosion, the causes of accelerated erosion, and the extent and impacts of erosion on human and natural systems. It also touches on the management and prevention of erosion.

Processes and types of erosion

The susceptibility of soil to erosion and the rate at which it occurs are dependant upon a number of factors, including geology, climate, soil type, and density of vegetation.

Erosion can be broadly grouped into two forms, wind and water erosion. Accelerated water and wind erosion can occur where the soil surface is bare and exposed to intense rainfall and wind events. Human activities such as the clearance of vegetation, inappropriate cultivation practices and overgrazing can cause the disruption of the soil surface and increase its susceptibility erosion. The 2001 State of the Environment Report identified features that distinguish natural erosion processes from human-induced erosion.

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Most wind erosion occurs in semi-arid and arid lands, and it has natural as well as human-induced components. The erosion and deposition of soil by wind has played a big role in the shaping of landforms across large parts of this continent, especially in the dune fields in the interior. However, over the past 150 years dune fields that were covered with natural vegetation have been cleared or grazed for agricultural purposes, leading to a greater rate of dust storms than would occur naturally.

Wind erosion results in the removal of large quantities of fertile topsoil containing organic matter, reducing the productive value of affected lands. Significant quantities of this dust are deposited off-shore, and on many occasions over the past century dust originating in Australia has been deposited as far away as New Zealand.

Dust storms are a useful indicator of wind erosion. The 1996 State of the Environment Report noted that since the 1970s there had actually been an overall decrease in the annual frequency of dust storms across. While some of this change is thought to be the result of increased rainfall spurring widespread vegetation recovery, it appears that the change is greater than can be explained by climatic conditions. This has been attributed to reduced rabbit populations through the release of the calicivirus, improvements in agricultural management practices resulting in increased vegetation cover and the spread of ‘woody weeds’.

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Water erosion

There are several types of water erosion, the most important in Australia being sheet and rill erosion, tunnel erosion, gully erosion and stream channel erosion..

Sheet erosion occurs when a relatively uniform layer of topsoil is removed by raindrop splash or water run-off, and it can occur during severe storm events. It often affects areas where the soil is lacking in a protective vegetation cover. Rill erosion results from the concentration of surface water and runoff into deeper, faster moving channels, or rills, which follow low points through paddocks. The rills may be as deep as 30cm. Rill erosion can occur with sheet erosion, and it is commonly seen in paddocks that have been recently cultivated prior to intense rainfall.

Sheet and rill erosion result in the loss of topsoil and nutrients, with significant impacts on productivity. They can also have considerable off-site effects through the deposition of soil in streams, dams and reservoirs, reducing water quality and altering aquatic habitats.

Tunnel erosion occurs when water scouring or seeping through dispersive subsoils forms underground tunnels. These tunnels are often initiated by water accumulating and moving along cracks and channels, or into rabbit burrows or old tree root cavities. Sheet erosion can initiate tunnel erosion, by concentrating water in the subsoils or in low areas where there are rabbit burrows and tree root cavities.

When underground tunnels caused by this movement of water increase in size, parts of the tunnel roof may collapse, resulting in gullies and potholes. In fact, tunnel erosion is often not detected until tunnels begin to collapse and gullies are formed. The appearance of fine sediment downhill of a developing tunnel outlet point or hole, or even water seepage at the base of a slope, can indicate the early signs of tunnel erosion. Tunnel erosion can lead to a general loss of production, and can deposit infertile subsoils in lower, more productive areas. Its can also result in increased sediment loads in rivers and streams. In serious cases, tunnel erosion may , by causing gully erosion, restrict access across properties.

Gully erosion is one of the most visible and severe forms of water erosion. Gullies are steep-sided watercourses which experience ephemeral flows during heavy or extended rainfall. Advanced rill erosion may develop into gully erosion. Gully depth is, of course, limited by the depth of the underlying rock, so that most gullies are normally less than two metres deep. However, in deep alluvial and colluvial soils, they can reach depths of up to 15 metres.

The formation of erosion gullies can be triggered by various human activities, including cultivation and grazing leading to the loss of vegetation cover on soils susceptible to erosion. The concentration of run-off through furrows, contour banks, stock tracks, fences and roads can also lead to gully formation. Or it may be triggered when drainage lines are disrupted, through clearance of vegetation, diversion, or the construction of residential areas.

Gully erosion affects soil productivity, restricts land use, and can cause damage to fences, roads and even buildings. Its immediate impacts include the build-up of siltation along fence lines, waterways, road culverts, and in dams and water reservoirs. It can also result in water with high sediment loads reaching creeks and rivers, where nutrients and pesticides attached to soil particles can cause damage aquatic life.

Streambank erosion occurs when there is degradation of riparian vegetation. The 2001 National Land and Water Resources Audit estimates that it has been common for creeks and rivers cleared since European settlement to increase fourfold in depth and twofold in width. As in the case of gully erosion, streambank erosion can be a significant source of excess sediment in waterways, causing damage to floodplain land and infrastructure.

Extent of erosion

The maps shown in Figures 9.1 and 9.2 illustrate that large areas in Australia are highly susceptible to wind and water erosion. The 2001 National Land and Water Resources Audit estimated that almost 40% of the continent experiences low sheet and rill erosion (<0.5 t/ha/yr), 11 % experiences a high erosion risk and 50% experiences a medium erosion risk. The Audit found that the semi-arid woodlands and grazing lands in the Northern regions make the biggest total contribution to these kinds of soil erosion, although the highest rates of erosion were from tropical croplands.

With regard to gully and streambank erosion, the Audit estimated that around 30% of the Murray-Darling Basin was affected by moderate or high density erosion. Gully and streambank erosion were reported as being the dominant sources of sediment in waterways in southern Australia. The Audit found that 325 000 km of gullies across the area assessed had eroded about 4.4 billions tonnes of soil since European settlement. However, the Audit concluded that gully erosion in southern Australia had largely been stabilised, although gullies were still actively forming in northern Queensland and in some agricultural regions of Western Australia.

The Audit estimated that gully, streambank and sheetwash erosion deliver over 120 million tonnes of sediment to streams each year.

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Management

Ultimately, vegetation cover is the most critical factor in the protection of soils from water and wind erosion. Any action that reduces the protective cover of vegetation increases the risk of soil loss. In the case of streambank erosion, access by stock to waterways can cause damage to riparian vegetation, increasing the risk of soil loss.

Vegetation should be encouraged in eroded areas, although it may be difficult to establish it in exposed, infertile soils. Indigenous plant species can be considered, but a number of exotic grasses and other plant species have been used with success in the control of erosion. In some cases, an initial application of fertilisers helps in the establishment of vegetation on degraded soils, and irrigation can also assist in the revegetation process. Stock should be excluded from eroded areas.

Other management techniques include contour banks, reduced or low tillage, low frequency of cropping, strip cropping and using windbreaks to reduce wind speeds.

The key to the management of erosion on grazing lands is control of grazing pressures. On all agricultural land, soil management to increase organic matter and to promote water infiltration and evapotranspiration by plants is vital to the management of soils degraded through erosion.

In the case of gully erosion, there are significant engineering approaches that can assist in the control of the problem, including gully reshaping and filling, and the construction of diversion banks and structures that minimise the impact of run-off.

The management of erosion can be very difficult and costly, and in many cases once erosion has started, it can only be minimised, but not stopped. The control of erosion over large areas of poor soils may be impractical.

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The production and destruction of ozone

The ozone layer in the stratosphere is produced through a process known as ‘photodissociation’ in which oxygen (O2) filtering up from the top of the troposphere is transformed, under the influence of sunlight, to ozone (O3) (see Box 1). Although ozone is produced (and destroyed) at all altitudes, the process of dissociation of oxygen is greatest above the equator and the tropics, simply because that is where solar radiation is strongest. However, as a result of atmospheric circulation patterns, the highest concentrations of ozone are above the North and South Poles.

There are also processes that destroy ozone, preventing the overall loss of oxygen and build up of ozone in the atmosphere over time. Under the influence of ultraviolet radiation some ozone molecules photodissociate and break apart into ‘ordinary’ oxygen (O2) and a single oxygen atom (O) (Box 2).

Ozone is thus constantly being produced and destroyed in the stratosphere in a dynamic balance. The total amount of the gas in the stratosphere has remained more or less constant over a very long period of time, and it is estimated that photodissociation creates about one gigatonne of ozone annually, and that around one gigatonne is destroyed every year through natural processes.

Human activities are now interfering with the balance of these reactions by increasing the rate of ozone destruction, while the rate of stratospheric production remains the same. The result is a progressive and significant decline in the concentration of stratospheric ozone.

Box 1
The natural production of ozone Ozone is formed when a molecule of ‘ordinary’ oxygen (O2) breaks up into two free oxygen atoms under the influence of ultraviolet radiation (with wavelengths below 242 nanometres), a process known as photodissociation: O2 + UV radiation → O + O Solitary atoms of oxygen are rare because they are highly reactive chemically, and tend quickly to recombine with other molecules. Most oxygen atoms that result from photodissociation rapidly recombine to form new oxygen (O2) molecules, establishing an equilibrium between the breaking up of oxygen molecules and the recombining of atoms into oxygen molecules. Occasionally, a free oxygen atom produced by photodissociation combines with an oxygen molecule (O2) to form ozone (O3), but this requires the involvement of another molecule – a mediator or ‘third body’ molecule – to take up the energy released in the reaction. This molecule is usually nitrogen (N2), but many other molecules can play this role as a catalyst for this reaction, so it is convenient to label it M: O2 + O + M → O3 + M While the main outcome of this process is the production of ozone, these reactions provide enough energy to the molecule M to cause it to move faster, thus warming the surrounding atmosphere.

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Box 2
The natural destruction of ozone There are also processes that destroy ozone, preventing the overall loss of oxygen and build up of ozone in the atmosphere over time. Under the influence of ultraviolet radiation some ozone molecules photodissociate and break apart into ‘ordinary’ oxygen (O2) and a single oxygen atom (O): O3 + UV radiation → O2 + O Most of the single atoms of oxygen produced in this reaction recombine with molecular oxygen (O2) to form ozone again. However, some of them combine with ozone molecules to form two oxygen molecules: O3 + O → O2 + O2 However, the most significant loss of ozone is through catalytic cycles in which, in the presence of a mediator or ‘third body’ molecule, ozone is converted to molecular oxygen. The catalytic substance could be a free radical of the nitrogen, hydrogen, chlorine or bromine families. For example: NO + O3 → NO2 + O2 and NO2 + O → NO + O2 With the net effect: O3 + O → O2 + O2

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Concern about ozone

Concern that human activities may alter the concentrations of ozone in the stratosphere was first raised in the late 1960s, following proposals for fleets of Supersonic Transport Aircraft (SST) that would fly higher than current aircraft, releasing hydrogen and nitrogen compounds directly into the stratosphere at rates. Initially, the main impact was envisaged as climate change due to the effect of vapour trails on the penetration of ultraviolet (UV) radiation, but it was soon realised that emissions from SSTs had the potential to destroy ozone and so reduce its concentration in the stratosphere.

A report was ordered by the US Congress in 1971 to investigate the scientific evidence for the likely impact of the proposed SST fleet on the environment. This three year research program concluded that a fleet of 500 Boeing SSTs would cause a 16 per cent reduction in stratospheric ozone in the northern hemisphere and a loss of around 8 per cent in the southern hemisphere. But by the time the final report was released, programs to develop SST fleets had already been scrapped due largely to economic considerations.

Chlorofluorocarbons - Chlorofluorocarbons (CFCs) were the next compounds to figure prominently in the history of concern about the ozone layer. They are a class of synthetic chemicals invented in the late 1920s that have multiple industrial and commercial applications. They are non-toxic, non-corrosive and chemically relatively inert. By the 1970s they were widely used for refrigerant, solvent and other purposes, although over 75 per cent of the CFC emissions came from spray cans in which they were used as propellants.

In 1974 Mario Molina and Sherwood Rowland suggested the possibility that CFCs might be an important source of chlorine that could serve as a catalyst to destroy ozone in the stratosphere. Their work sent shock waves through scientific and political communities and gave rise to a highly contentious debate, especially since the hypothesis was based on very few hard data and only limited laboratory observations.

The debate stimulated further scientific research, and in 1979 NASA published a report that highlighted the significance of the CFC-ozone link and predicted an eventual loss of 16.5 per cent of stratospheric ozone. NASA suggested a degree of urgency about the CFC issue. However, disagreements within the scientific and political communities initially impeded the development of effective national policies and international negotiations addressing these concerns.

There are certain other substances entering the atmosphere as a result of human activities that also contribute to the breakdown of ozone in the stratosphere. Methyl bromide and the halons are particularly important. Methyl bromide is used as a biocide for the control of insect pests in the soil and in grain products, and the main source of the halons is fire extinguishers.

The ozone hole - It was in the early 1980s that the first conclusive evidence for the loss of stratospheric ozone was produced. A group of scientists, members of the British Antarctic Survey group, had been measuring ozone levels above Halley Bay for almost 25 years. During the spring of 1981, they noted significant decreases in ozone levels over the Bay, although these levels recovered a few months later. The same phenomenon occurred the following year, but to a greater extent. Unsure of the significance of these data, the group did not publish their findings at the time. They believed their equipment might have been faulty. However, new equipment was installed and measurements the following year from the new apparatus still showed low springtime ozone levels. These results were finally published in 1985, describing a loss of almost half the ozone over Antarctica during the spring months, with full recovery several months later.

The ozone hole over Antarctica has continued to occur seasonally every year since its discovery, but the early 1990s saw particularly pronounced losses of ozone. Record low levels were measured in 1992-1993, when the total column of ozone over the South Pole was reduced by around 60 per cent. These unusually low levels are partly attributable to the eruption of Mt Pinatubo in 1991, which resulted in the release of sulphate aerosols which increased the destruction of ozone by chlorine and bromine. Although the size of the ozone hole plateaued from the mid-1990s, as international agreements reducing emissions of ozone depleting substances came into effect (see below), the hole then covered around 26 million square kilometres – an area nearly three times as large as Australia.

The 1999 Antarctic ozone event was the second largest and strongest to that time, when low ozone values occurred over an area greater than 10 million square kilometres for 98 days.

It has been estimated that, despite increased control of emissions of ozone-depleting substances, a substantial hole in the ozone over Antarctica will continue to appear each spring for several more decades, as atmospheric concentrations of chlorine and bromine slowly return to the levels of the 1970s.

Other ozone losses - Recent measures of stratospheric ozone have suggested that the ozone layer over the Arctic is also depleted at certain times of the year, but not as dramatically as over Antarctica.

In addition to the ozone hole above Antarctica, ground-based and satellite measurements have revealed a general thinning of stratospheric ozone over much of the globe during the past few decades. On average, the concentration of stratospheric ozone has decreased by around 4-5% per decade in both the northern and southern hemispheres. Cumulative losses of around 10% during winter and spring, and 5% during summer and autumn, have been noted over locations in Europe, North America and Australia.

The future of the ozone layer is very uncertain. Soon after the turn of the millennium it was thought that global ozone loss had peaked in the late 1990s, and was responding to the reductions in ozone-depleting substances resulting from international compliance with the Montreal Protocol and its Amendments and Adjustments (see below). This led to predictions that the ozone layer would be back to normal by the middle of this century. However, in 2005 the hole over the Antarctic was the biggest ever (29.5 million square kilometres), and recently significant loss of stratospheric ozone has been recorded in the northern hemisphere.

The situation is indeed extremely complicated. For example, while it seems clear that there has been a substantial decline in the concentrations of the ozone-destroying pollutants, there has also been a significant increase in the formation of ice clouds in the stratosphere in winter time in the northern hemisphere, which make it easier for the chemical reactions that destroy ozone to take place. These clouds may be the result of global warming due to the enhanced greenhouse effect.

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UV penetration and its effects on living systems

Evidence for the loss of stratospheric ozone has generated a great deal of concern throughout the international scientific community, because any thinning of the ozone layer will result in increases in UV radiation at ground level. It has been estimated that for every 1% loss of stratospheric ozone, there is a 2% increase in the amount of UV radiation allowed through the atmosphere.

Increases in levels of clear sky UV radiation were detected in both hemispheres over the period 1979-1993, a trend consistent with the gradual thinning of the ozone layer over this period. These increases in radiation were greatest in the southern hemisphere. A NASA study found an average increase in damaging UV radiation of around 5% per decade, with maximums of nearly 10% in South Chile and Argentina.

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UV effects on plants

In field and laboratory experiments it has been found that increasing the exposure of plants to UV-B (wavelength 320 nm - 290 nm) disrupts photosynthesis, reduces growth rates and increases susceptibility to disease. These studies have also suggested that increased exposure to UV-B may alter the functioning of plants through decreasing leaf expansion and stem elongation, altering flowering time and changing chemical composition.

In non-agricultural ecosystems, like grasslands and forests, increased UV-B radiation is likely to have a number of detrimental effects, including interference with the timing of flowering and pollination, and changes in the competitive balance of species. Trees are especially vulnerable to exposure to UV-B when they have been previously weakened through disease, predation, drought or acid rain.

The impacts of increases in UV radiation on agricultural yields and forest growth are not yet clear, because of deficiencies in data collection and uncertainty about the influences of climates and micro-climates and of air pollutants. But experiments with several hundred plant species and crop strains indicate that as many as two thirds are sensitive to UV radiation. The most sensitive types include peas, beans, melons, cabbages and mustard, although growth was also adversely affected in maize, rye and sunflower seedlings.

There are uncertainties surrounding the combined impacts of increased UV exposure and global warming on plant systems.

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UV effects on humans

Increased UV levels as a result of the thinning of the ozone layer would have major impacts on humans.

One estimate suggests that a 1% decrease in stratospheric ozone is likely to lead to a 2-5% increase in incidence of skin cancers.

For Australia, which already has one of the highest rates of skin cancer in the world, the changes that have taken place in UV radiation are predicted to lead to a 3-4.5% increase in non-melanoma skin cancer (compared to the projected global increase of 2-2.5%). Estimates for malignant melanoma are less certain, although they are projected to increase over the next few decades. They have increased worldwide in white populations by 3-7% since the early 1960s

Basal cell carcinoma (BCC), is predicted to increase by 13-15% in the northern hemisphere and by up to 20-30% in the southern hemisphere. The increase in the less common squamous cell carcinoma (SCC) is likely to be double that of BCC.

Our eyes are constantly absorbing ultraviolet radiation Excessive UV exposure can cause serious damage to ocular cells, leading to melanomas of the eye or blindness. Exposure to UV-A (wavelength 400 nm - 320 nm) has also been associated with the formation of cataracts. It has been estimated that for every 1% depletion of stratospheric ozone, cataract incidence would increase by 0.6-0.8%. Overall, a 10% reduction in stratospheric ozone could result in an additional 1.75 million cases of cataract a year world wide.

Research in humans and other animals has demonstrated that UV radiation, even at normal levels, can lead to suppression of the body’s immune response, both locally and systemically, and hence reduce resistance to infectious disease. It is also thought that increased UV radiation may reduce the effectiveness of vaccinations.

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UV and other species

The effects of increased UV radiation on other terrestrial animals are predicted to be similar to those experienced by humans, with high levels of UV radiation causing damage to the chromosomes and DNA replication. Current evidence suggests a significant increase in eye complaints of livestock, notably corneal irritations (pink eye), cataracts and eye cancer. Other predicted effects include changes in immune functioning, and even in reproduction.

UV and aquatic species

Much of the concern about increased ground levels of UV radiation, especially UV-B, has focused on the likely effects on phytoplankton. Commonly referred to as ‘the grass of the sea’, phytoplankton are the largest single group of photosynthetic primary producers. They are found close to the surface in all aquatic environments and they form the base of aquatic food webs. Phytoplankton make up 75% of the marine plant mass and are the main food source for most marine life, as well as being important producers of oxygen.

Many hundreds of types of phytoplankton exist, and they vary in sensitivity to UV exposure. However, most of them are vulnerable to damage by increased UV radiation because they live close to the water’s surface. Studies have shown that UV radiation can inhibit the movement and reproduction of phytoplankton, bleach their cellular pigments and impair their capacity to photosynthesise.

It has been estimated that a 10% decrease in marine phytoplankton population would result in a decrease in the oceans’ annual carbon uptake by around five gigatonnes (i.e. 5,000 million tonnes), which is about equal to annual CO2 emissions from fossil fuel use by humans.

Increased UV-B radiation is also likely to interfere with reproduction in amphibians and fish, the eggs of which are generally UV sensitive. Increased UV exposure can also damage fish, shrimps, and other marine life in the early stages of development.

Wildlife in Antarctica is already starting to show the effects of ozone depletion, with the embryos of limpets and starfish and other invertebrates failing to develop properly due to the higher levels of UV experienced during the annual springtime ozone depletion event.

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The Montreal protocol

The discovery of the hole in the ozone layer over Antarctica during the mid-1980s, coupled with the growing body of scientific evidence demonstrating the role of human activities in this development, gave rise to serious concern at the international level. It was recognised that the thinning of the ozone layer represented a very real and serious threat to humans and natural systems, calling for immediate action on a global scale.

This concern led to an international treaty, the Vienna Convention for the Protection of the Ozone Layer of 1985, through which governments around the world committed themselves to the protection of the ozone layer and agreed to cooperate in scientific research aimed at improving understanding of the processes behind the ozone depletion. Further negotiations resulted in the development of the Montreal Protocol on Substances that Deplete the Ozone Layer, which was finalised in September 1987. This Protocol set mandatory targets for phasing out the production and consumption of ozone depleting substances. It was originally ratified by 57 countries, but has since been signed by over 160 countries, including Australia, all of which are committed to taking steps to actively reduce, and eventually cease, the production, use and emission of ozone depleting substances.

Box 3
The Australian response Australia’s commitments to the Montreal Protocol are met through complementary legislation and controls enacted by Commonwealth, State and Territory Governments. The Australian Strategy for Ozone Protection, written in 1989 and revised in 1994, outlines the national approach. The Department of the Environment, Water, Heritage and the Arts is the Commonwealth agency presently responsible for the coordination of national ozone protection measures and the administration of the Ozone Protection Act 1989. This department controls the manufacture, import and export of ozone depleting substances, the issuing of licences permitting these activities and the prosecution of breaches of the Ozone Protection Act. State and Territory Environmental Protection Agencies (EPAs) and environment departments are mainly responsible for controlling the sale and use of ozone depleting substances, but also ensure proper training and accreditation of people who service equipment containing such substances.

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In the years since the Montreal Protocol was first ratified, improvements in scientific understanding of the extent and mechanisms of ozone depletion and advances in ozone-benign technology have led to the strengthening of control provisions and to the acceleration of phase-out dates for several ozone depleting substances. Other ozone depleting chemicals have since been recognised and added to the list of controlled substances that the Protocol aims to reduce and eventually eliminate. These findings have been taken into account at a number of international Conventions held from 1990 onwards.

The Convention of London in 1990 resulted in the establishment of a Multilateral Fund that develops and implements cost-effective mechanisms to assist developing countries meet their Montreal Protocol commitments. A key component of this fund supports the transfer of ozone-friendly technology from developed to developing countries. Australia’s contribution to this fund involves financial contributions as well as undertaking a number of bilateral projects in developing countries.

As a consequence of these international agreements, emissions of ozone depleting substances arising from human activities are being reduced, and it is hoped that they will eventually be eliminated, allowing the recovery of the ozone layer by around 2065.

HCFCs and HFCs - Hydrochlorofluorocarbons (HCFCs) and Hydrofluorocarbons (HFCs) are currently the most popular replacements for CFC chemicals, and have shorter atmospheric lifetimes. Although the ozone depleting potential of these compounds is much lower than that of CFCs, they still have the capacity to cause some destruction of ozone because of the traces of halogens they release into the atmosphere. Increased use of these substances could result in significantly greater contributions to stratospheric ozone depletion than currently suggested. They are also potent greenhouse gases. There is currently little information on the potential toxicity of replacement chemicals, or of the safety of by-products of chemical processes used in the production of CFC replacements.

There has been a substantial drop in the use of methyl bromide as a biocide, although the United States and some other countries are still using it for certain ‘critical’ uses.

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What individuals can do

Individuals can play their part in the reduction of emissions of ozone depleting substances like CFCs and halons in various ways.

Leakages of CFCs from car air conditioners should be minimised. This can be done by running the car air conditioning for 10 minutes every week to keep seals lubricated, and to reduce cracking and leakage. When these air conditioners are serviced it is important to check that the refrigerant is recycled.

CFC emissions from refrigerators can also be reduced. Old refrigerators should be taken to CFC recycling depots or to an accredited service person to remove the refrigerant prior to the disposal of the appliance. It is important that air conditioners and refrigerators are serviced by persons accredited with the CFC Registration Board.

To reduce halon emissions, BCF fire extinguishers, which contain halons, should be replaced. Fixed halon fire suppression systems in buildings must also be phased out and replaced. All of these must be taken to an authorised storer of halons.

Further reading

For further information on the thinning of the ozone layer see:

(1) The Australian Academy of Science’s Nova website: www.science.org.au/nova/004/004box04.htm

(2) http://www.epa.gov/Ozone/strathome.html

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Born and raised in Canberra, Alice Thompson was brought up with an appreciation of, and interest in the environment, leading her to study at the Australian National University, majoring in Geography/Human Ecology and Population Studies, and her involvement in the Nature and Society Forum (NSF). She now lives in Sydney where she currently pursues a career in Government working for the NSW Office of the Australian Bureau of Statistics (ABS). Before joining ABS Alice was employed by NSF as a Research Officer to prepare reports on important ecological issues in Australia.

2012-06-18T14:45:00 2012-06-20T15:36:42+10:00 roba Ocean processes http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/ocean-processes and greenhouse warming

David Tranter

Summary

Earth is a fine-tuned ecosystem, warmed by the sun, the global greenhouse and the ocean. The alternating advance and retreat of polar ice and snow over the past 600,000 years (ice ages) were initiated by orbitally induced variations in the angle of the summer sun above the polar horizon (orbital effect). So much fresh water was returned to the ocean each inter-glacial phase by the melting of continental ice that, combined with thermal expansion of the water column, sea level rose by as much as 120m.

The orbital effect was reinforced by greenhouse warming. This, in turn, was further reinforced by ocean processes that limited how much aerial carbon dioxide (CO₂) could dissolve in the ocean and be stored in the ocean interior; and how much dissolved CO₂ could be removed from the ocean by photosynthesis or returned to the air at upwellings.

Man-made fossil fuel emissions have now increased the atmospheric concentration of CO₂ from the ice age maximum (~280 ppm) to ~390 ppm and the ocean has become more acid. As fossil fuel emissions continue to increase, greenhouse warming will raise sea levels high enough to inundate low-lying coastal places such as coral atolls, deltas and those densely populated foreshores where many of the largest cities and airports in the world have been built. That scenario is a matter of choice, not necessity, and it can be limited by governmental intervention.

1. Introduction

Science is driven by curiosity, observation, experiment and pattern recognition. Experiments in 1859 by Irish scientist John Tyndall, Professor of Natural Philosophy at the Royal Institution in London, showed that CO₂ is a powerful greenhouse gas. It dissolves less readily in warm water than cold, a fact you can confirm yourself by observing how much gas is released from a bottle of fizzy drink that’s been sitting in the sun compared with one that’s been kept in the refrigerator.

But there is only one earth, so despite the prevailing habit of using its atmosphere as a rubbish dump for fossil fuel wastes, it would be logistically impossible and socially irresponsible to experiment with it. The recent erosion of the ozone layer that protects life on Earth from harmful ultraviolet radiation has confirmed that small traces of chemical can have a big effect, most of those that did the damage coming from small cooling tubes at the back of man-made refrigerators.

A useful scientific tool is pattern recognition, where correlations of observations lead us to the ultimate identification of the mechanism involved. That’s how Darwin and Wallace arrived at the theory of evolution by natural selection; how Wallace and Wegener came up with the theory of continental drift; how Milankovich conceived the theory that recent ice age cycles were due to variability in Earth’s orbit around the sun [1]; each theory with a global dimension and each now verified by further observation. So too it is with the current theory that fossil fuel emissions warm the earth.

2. Air-Sea Interaction

The ocean is a giant solar-heated cauldron, whose ingredients are temperature, salinity, currents, winds, sea-ice and living organisms. It is now absorbing more than 80% of the heat that Earth receives from the sun [2], the sea-air interface acting as a busy transit station for heat, moisture and CO₂; and as the source of clouds, cyclones, and tornados. The oceanic equivalent of atmospheric pressure is density, a blend of temperature and salinity that, in concert with the wind, drives the surface circulation of the sea.

An example of a transient air-sea circulation pattern is the El Nino Southern Oscillation (ENSO). Cool, high-latitude Pacific air, converging from each hemisphere towards the equator, is deflected westward in the wake of the earth’s rotation to form the trade winds that drive equatorial surface water towards Australasia. Contained by this barrier, that wedge of warm surface water becomes the heat engine that generates what we in Australia regard as normal weather.

When the trades lose their clout, that vast body of warm surface water surges back towards the Americas leaving Australia in drought - a fairly regular 3-4 year cycle that is sometimes confused with climate change. It is not; it is a normal pan-Pacific weather pattern. Climate is weather averaged over time, the period adopted by climatologists being ~30 years. It follows that weather at any particular point in time might have little to do with climate; it could well be little more than “noise” or “static” rather than a genuine climate signal.

3. Evolution of “Air”

The fact that air contains so little CO₂ (less than 0.1%) might appear to be at odds with the fact that it is a powerful greenhouse warming agent; however such apparent contradictions are fairly common in nature: For example, the nutrient resources that sustain the luxuriance of a coral reef or tropical rainforest are so scarce in the immediate environment they are barely detectable; their recycling rate is so rapid, or a mere 0.05% of alcohol in our blood stream can so severely impact our decision processes.

Primeval air had little oxygen and a lot of CO₂ (of volcanic origin), whereas today’s air has a lot of oxygen (21%) and only enough CO₂ to warm the earth. This apparent “anomaly” is due to the evolution of life on a lifeless planet. The primaeval forms of life were bacteria that used chemical energy for their metabolism, generating methane (natural gas) as a by-product, some of which is now imprisoned within icy matrices on the sea floor at depths greater than 300m. In today’s oxygen-rich world, such anaerobic bacteria are confined to smelly refuges, superseded by green photosynthetic bacteria that draw their energy from sunlight. Extracting hydrogen and dissolved carbon dioxide from the surrounding water, they produce carbohydrates, yielding oxygen (O₂) as a by-product. Over the ages, this oxygen accumulated in the air in pace with the decline of CO₂, shaping and fine-tuning the composition of the air.

Descendants of those primaeval green bacteria are the phytoplankton, a community of unicellular algae that inhabit the sunlit layer of the ocean, collectively withdrawing as much CO₂ from the sea each year as land vegetation withdraws from the air. Another favoured habitat is polar sea-ice at the interface between snow and ice, fed by a rich supply of nutrients from the underlying sea and continually sunlit for a few months of the year. In that brief period, as much CO₂ is withdrawn from the ocean [3] as the Amazon rain forest removes from the air in a year.

There are hundreds of different kinds of phytoplankton. They are dust-sized particles of spectacular beauty, some radially symmetrical like minute snowflakes, some encased in shells of glass, chitin or calcium carbonate. The ocean floor is littered with their remains, which are ultimately recycled in the earth’s interior, surfacing later on as limestone or chalk, a cycle thought to regulate the global climate on a geological time scale. What those species have in common are structures to keep them up in the sunlight, their nemesis the stratification of the water column that isolates them from their sub-surface nutrient supply, their saviour winter mixing.

4. Sea-ice

The axis of Earth’s rotation is so inclined to the plane of its orbit around the sun that the poles receive less heat than the equator and become covered in sea-ice every winter. An alien intelligence studying Earth from afar in fast forward mode might think Earth was breathing as its polar sea-ice frontier advances and retreats with the seasons and the ice-age cycles - an image that is more than metaphor.

Sea-ice sheds brine as it forms and the underlying cold, saline, aerated seawater, enriched with carbon dioxide of atmospheric origin, sinks under its own weight into the abyss as a gigantic sub-surface waterfall. Without such ventilation, bottom-living animals would suffocate and rot for want of oxygen, generating clouds of poisonous, buoyant, hydrogen sulphide gas that are thought to have wiped out life on Earth at least once in the distant past.

This bottom water weaves its tenuous way across the sea floor, ultimately surfacing a millennium later at upwelling sites, such as those off the west coasts of continents and along the equator. Under the climate regimes that prevailed over the past 600,000 years (Figure 1), when the CO₂ concentration of the air was always less than 280ppm , those (low latitude) upwellings would have released their load of super-saturated CO₂ into the air like bubbles from a newly opened soda water bottle

Figure 1: Warming-cooling cycles (the “Ice Ages”) in the last 600,000 years. - Le Page 2007

5. Continental Ice

Whereas today’s sea-ice advances and retreats with the seasons, continental ice has been accumulating, layer by layer for at least a million years, each layer containing bubbles of air from the atmosphere of the day [RD1]. This historic archive of temperature and CO₂ (Figure 1), which has been accessed by coring through the permanent Antarctic ice sheet, covers the past 600,000 years (six ice age cycles). Compiled by Michael Le Page [1] from the 2004 work of Royer et al, with a shorter, independent record of sea level, those data confirm the orbital cycle that Milankovich had predicted from astronomical calculations. Among its most interesting features are the following:

Temperature and CO₂ cycled up and down with a period of about 100,000 years.
Those periods were fairly regular and their amplitude limited.
Temperature and carbon dioxide were closely correlated, temperature leading with CO₂ close behind.
Reversals of temperature and carbon dioxide trends were swifter after each minimum than each maximum.

Those phenomena raise the following interesting questions:

How could so weak a signal as the orbital effect have generated such severe global climate consequences, its warming influence (as calculated from astronomical observations) being only 10 Watts/m², which is about the same as a 100 Watt globe in a closed room 3m square? [4]
Where did all the CO₂ go that was lost from the atmosphere each glaciation (when most high latitude vegetation would have been covered in snow and ice and unable to withdraw much CO₂ from the atmosphere for want of light)?
Why did temperature lead and CO₂ lag?

The answer to the first question is that the orbital effect was reinforced by greenhouse warming. Although less at any one point on the earth than the orbital effect (which is limited to polar ice in the polar summer), CO₂ induced warming (~1.7 W/m²) influences the entire cloud-free surface of the earth every day of the year, land and sea alike. Answers to the other questions are to be found in the working principles of the ocean:

Most of the CO₂ that was lost during the glacial phase of each ice age went directly into the ocean when the sea was cold and CO₂ solubility high [5].That’s why the ocean now contains about 90% of all the free CO₂ on earth, making it a major global climate force.
Because CO2 is less soluble in warm water than cold, global warming releases dissolved CO₂ into the air, amplifying pre-existing greenhouse warming. This draws even more CO₂ from the ocean (and so on) until a new balance is reached. That’s why CO₂ is considered to be the main mechanism reinforcing global swings in temperature.
The most likely reason why the ice age warming trend was faster than the subsequent cooling trend is because the flow of CO₂ across the air-sea interface is more effective in colder seas (when the water column is well mixed) than in warmer seas (when surface waters become isolated from the interior of the ocean by a sharp temperature gradient known as the thermocline.
Current acidification of the ocean is most likely due to the current retention of CO₂ by upwelled water, constrained as it now is by the stronger CO₂ gradient that has developed across the air-sea interface since that upwelled water left the surface ~ 1000 years earlier.

6. Ocean Amplifiers of Greenhouse Warming

In the centre of the conceptual warming spiral illustrated in Figure 2 is what I have called a stable temperature cycle - for example the seasons of the year or the annual advance and retreat of Antarctic sea-ice.

Tranter2 amplifiers

Figure 2: Global Warming Amplifiers: Oceanic and Social Feedback Loops. - Tranter, 2009

These are cycles, rather than trends, and by definition reversible. By contrast, if you follow the spiral clockwise you will notice the following series of gains in global temperature, labelled G1-G5, which amplify the previous greenhouse warming trend:

Sea-ice albedo (G1). Imagine how much hotter it would be standing in your bare feet in summer on black bitumen compared with white pavement. This phenomenon (albedo) has a strong influence on global temperature because sea-ice is a mirror, which reflects the warmth of incident sunlight back to space. When sea-ice melts each summer, that part of the ocean absorbs heat instead of cooling and, as more sea-ice melts, warming gains momentum like a locomotive gaining speed. Should the sea-ice frontier recede each successive winter, albedo warming would become a long term trend until it was reined in by orbital cooling.
Sea-ice habitat (G2): The winter extent of Antarctic sea-ice, which is 50% greater than the whole Antarctic mainland, is a powerful seasonal bio-sequestration agent by virtue of the CO₂ uptake of the algae that live within its interstices. When sea-ice melts, that algal biomass empties into the underlying sea and sinks rapidly to the deep sea floor. Should the sea-ice frontier retreat year by year due to global warming (as predicted by IPCC2), this valuable cooling agent would weaken; and the organic carbon that would otherwise end up on the sea floor would accumulate in the air as CO₂, reinforcing pre-existing greenhouse warming.
Temperature Induced stratification (G3). Most of the global ocean is located in low latitudes, where the thermocline isolates surface phytoplankton from their sub-surface nutrient source, limiting their capacity to transform dissolved CO₂ into particulate matter. The immediate result is a reduced flow of CO₂ from air to sea, reinforcing greenhouse warming, ultimately strengthening the thermocline and extending its areal expanse.
CO₂ solubility (G4). As the earth warms up, so too does the ocean, which then accepts less CO₂ from the air, reinforcing pre-existing greenhouse warming, an effect calculated to account for ~ 20% of the warming that brings the glacial phase of each ice age cycle to a close [2].
Methane hydrate release (G5). Methane hydrate exists in abundance in frozen cages on the sea floor at depths greater than 300m. Should bottom temperatures warm, methane molecules are likely to escape into the water column and eventually the air above. Since methane is an even more powerful greenhouse gas than CO₂, the consequence of its release would be to dramatically reinforce pre-existing global warming.

7. Man-made Amplifiers of Greenhouse Warming

All of the above amplifiers are elements of natural climate change - a card that humanity has been dealt by nature. That constraint does not apply to man-made warming, driven as it is by “social” rather than natural feedbacks, such as those shown on the left in Figure 2. They are matters of choice not necessity and, since neither the greenhouse layer nor any of its reinforcing agents discriminate between natural and man-made molecules of CO₂, the consequence is the same, namely further greenhouse warming. The difference is that each molecule added to an atmosphere that already contains more CO₂ than at any previous time during the ice ages is a molecule that takes Earth into uncharted territory whose main symptom is fever.

The Intergovernmental Panel on Climate Change (IPCC) has identified the likely impacts of man-made global warming [2]. However changes are now happening at the high end of IPCC projections, due to the combined influence of the oceanic and social feedbacks illustrated in Figure 2. Although such non-linear effects are difficult to model, they are nonetheless real, present and significant. Amplified by increasing fossil fuel emissions, they could easily carry the global climate towards some rather nasty tipping points much sooner than most of us would wish.

Figure 3 illustrates the warming consequence of doubling the CO₂ concentration of the air (the current trend). It shows that that independent reinforcing feedbacks, such as those identified in Figure 2, have a cumulative effect whose ultimate consequence is irreversibility. Figure 4 shows that CO₂ stayed below 280 ppm throughout the past millennium until the Industrial Revolution, when it rose rapidly towards 400 ppm, a trend that may have begun as far back as 8000 years ago (Figure 5) when natural forests were cleared and burnt for agriculture [5].

Tranter3 overheating

Figure 3: The Cumulative Global Warming Effect of Multiple Feedback Gains. - Paltridge, 2009

Tranter4 CO2

Figure 4: Exponential rise of Atmospheric CO2 since 1800 A.D. – Internet

Figure 5: The CO₂ “anomaly” (deviation from the norm) over the past 8000 years. - Ruddiman 2005

8. Sea Level Rise

Only 20,000 years ago, at the peak of the last glaciation, when ice sheets 1000m thick covered Canada and Northern Europe, global sea levels were 120m lower than they are today (Figure 1) and the straits separating the Australian mainland from New Guinea and Tasmania were dry land. Sea level is now rising at about 3mm per year, half of which is due to thermal expansion caused by fossil fuel emissions [6]. During the previous inter-glacial era (125,000 years ago), when polar regions were significantly warmer than now for an extended period, sea levels rose a further 4-6m [2]. Should that happen again in the current inter-glacial era, when man-made warming is adding its weight to natural warming, the consequences could well be dire. Continental ice-sheets on Greenland and the Antarctic mainland, which contain most of the world’s fresh water, would start to melt and discharge into the global ocean elevating the sea level. The social impact of rising seas would be greater than in earlier inter-glacials because large cities and airports have since developed along the sea shore and they would be swamped by rising seas, as well as densely populated deltas and low lying islands, such as Boigu and Saibai in Torres Strait, and all the coral atolls in the world. The resulting influx of refugees to Australia from Bangladesh alone would dwarf the current influx, which already concerns so many Australians.

9. Climate Action

There is always more to learn, but the fundamental processes and consequences are clear-cut. Now is the time for action and that’s the job of society, not climate science. "We live", as the Chinese are wont to say, “in interesting times”. Perhaps future historians will recall the (paraphrased) words of Charles Dickens a century and a half ago:

“It was the best of times, it was the worst of times, it was the age of wisdom, it was the age of foolishness, it was the epoch of belief, it was the epoch of incredulity, it was the season of light, it was the season of darkness, it was the spring of hope, it was the winter of despair, we had nothing before us, we had everything before us.”

Sources

1. Le Page, M. 2007 New Scientist May 19, 34-42, After Royer, D.L. et al, CO2 as a primary driver of Phanerozoic climate, GSA Today, 14, 3, 4-10, (2004).

2. Intergovernmental Panel on Climate Change (IPCC) 2007, Climate change 2007. The physical science basis, 21pp.

3. Lizotte 2001. American Zoologist 41 (1), 57-73.   Back to text

4. Godfrey 2008 (Retired CSIRO Physicist). Personal communication.   Back to text

5. Ruddiman 2005. Plows, Plagues and Petroleum, Princeton University Press, N.J. USA   Back to text

6. Church 2009 (CSIRO Physicist). Personal communication.   Back to text

7. Paltridge 2009. (Retired CSIRO Climatologist). The Climate Caper, Connor Court, Vic. Aust.

[RD1] The continental ice has also been increasing and decreasing with the ice-ages. Only in the coldest places (Greenland, Antarctica) is the accumulation continuous, balanced by a flow of ice to the coast and the creation of glaciers.

2012-06-18T14:45:00 2012-06-20T15:20:37+10:00 roba Pollutants (POPs) http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/pollutants-pops Persistent organic pollutants (POPs), their health and environmental effects

Alice Thompson

Contents
Introduction
What are POPs?
The movement of POPs
Present global distribution
Exposure
Health and environmental effects
Action
Further reading

Introduction

The twentieth century was a time of chemical revolution, and the production of synthetic compounds world-wide escalated from less than 150 000 tonnes in 1935 to more than 150 million tonnes in 1995. In fact, some reports have estimated that by the late 1980s the annual global production of synthetic chemicals was as high as 300 million tonnes, approximately one-third of which is believed to have eventually reached the environment. There are now over 75 000 different synthetic chemicals used in pesticides, pharmaceuticals, plastics, and other industrial and consumer products.

Among the chemical products of industrial society there is a group of substances which have come to be known as Persistent Organic Pollutants, or POPs, which share the characteristic that they are toxic to humans and other living organisms, and persist in the environment for long periods of time. Estimates of the number of substances with this property range from a dozen or so to several hundred.

There is a growing body of evidence that these chemicals are having adverse effects on the health of humans and other organisms, even in regions where they have not been produced or used, and their management is now recognised as a critically important issue for the international community.

What are POPs?

POPs are carbon-containing compounds and they share the following common characteristics: they persist in the environment; they can be transported long distances from their source; and they accumulate in the tissues of living organisms.

POPs compounds are mostly halogenated – that is, they contain chlorine, bromine or fluorine. There are two major sub-groups of POPs: (1) polycyclic aromatic hydrocarbons (2) other hydrocarbons.

An initial list of twelve chemicals has been identified by the United Nations Environment Program (UNEP) for special attention, because there is ample evidence of their serious effects on the environment. They are sometimes referred to as the ‘dirty dozen’(see Box 5.1). Nine of the twelve UNEP listed POPs are pesticides used on agricultural crops and for public health disease vector control. Some POPs are industrial chemicals, while others are unintentional by-products of manufacturing and combustion processes.

Box 1 UNEP’s "Dirty Dozen" POPs listed for international action

The initial twelve POPs
aldrin¹	toxaphene¹
chlordane¹	mirex¹
DDT¹	hexachlorobenzene (HCB)^1,2,3
dieldrin¹	polychlorinated biphenyls (PCBs)^2,3
endrin¹	polychlorinated dibenzo-p-dioxins (dioxins)³
heptachlor¹	polychlorinated dibenzofurans (furans)³
¹Pesticide chemical ²Industrial chemical ³By-product

Source: http://www.dfat.gov.au/environment/haz_chem.html#pop

POPs dissolve readily in lipids (fats and oils), but not in water. As a consequence, when they are taken in by living animals, they tend to accumulate in fatty tissues where they can reach concentrations up to 70 000 times higher than in the surrounding environment.

POPs are largely resistant to natural forms of degradation, including photolytic (by light), biological and chemical degradation. This is the reason why some of them persist in the environment for a very long time. They are also semi-volatile, and they have a high degree of mobility through the atmosphere, either as vapour or adsorbed onto atmospheric particles. This means that relatively large amounts of POPs enter the atmosphere, often to be transported over great distances before coming down to earth.

The movement of POPs

The physico-chemical properties of POPs have resulted in their transportation, by evaporation and atmospheric processes, to almost all parts of the world, often far from the area of initial use and release.

The movement and deposition of POPs is affected by local environmental conditions. While there are many uncertainties, it seems that temperature is an especially important factor. The natural processes of degradation (photolytic, biological and chemical), slow as they are, are even less effective in the cooler parts of the world, leading to the net accumulation and persistence of POPs in polar regions. Lower temperatures also encourage the transformation of POPs compounds from the vapour phase to adsorption onto particles in the atmosphere, increasing the likelihood of their deposition on the Earth’s surface in rain or snow.

In more temperate regions of the world the movement of POPs is primarily from the atmosphere to the oceans, while their movement in tropical regions is mainly from the oceans to the atmosphere. The residence time for POPs in tropical aquatic environments is relatively short

Movement of POPs between the northern and southern hemispheres depends partly on the specific properties of the different compounds. For example, because of the high molecular weight and low volatility of DDT and PCBs, movement of these compounds between hemispheres is relatively slow compared to some other POPs, such as HCB, which are more readily transported long distances away from the point source of use.

Present global distribution

While there are many difficulties in attempting to estimate the global distribution of POPs, sufficient information has been gathered to indicate that their levels in organic, aquatic and sediment samples are generally higher in the northern hemisphere than the southern hemisphere. This can be partly explained by the high rates of usage of POPs compounds in developed countries in Europe and North America and in Japan. There has, however, been a significant decline in recent years in POPs concentrations in mid-latitude oceans of the northern hemisphere and in Arctic lake sediments, reflecting changes in patterns of usage.

On the other hand, the contribution of tropical regions to global levels of POPs is currently increasing. Tropical Asia is now a major source, and in the northern hemisphere POPs levels in areas adjacent to tropical countries tend to be higher than in those close to developed countries. This pattern is the result of recent restrictions and bans on DDT and certain other POPs in developed countries, while their use is increasing in many tropical areas.

Although concentrations of POPs are generally higher in the northern hemisphere than in the southern hemisphere, recent measurements in Australia indicate that concentrations of some POPs exceed acceptable levels. For example, unacceptable levels of DDT and dieldrin have been recorded in fish and other aquatic organisms in Australian oceans, and elevated levels of PCB emissions have been reported in Sydney. However, recent work shows that, with these exceptions, current levels of most POPs compounds lie at acceptable levels in Australia. Most contamination in this country has originated from our own usage rather than from global transportation from other areas.

Exposure

Animals can be exposed to POPs compounds in a number of ways. POPs can be taken up directly by organisms in contact with contaminated water. Chlordane, for example, is taken up directly from water, to be concentrated in the organs of aquatic species like minnows. POPs can also be taken up indirectly through the food chain, and they enter land animals mainly through the consumption of contaminated food.

Data from many countries have shown that POPs have become widely distributed in the food supply of humans. Around 90% of the total human intake of POPs is received through the consumption of foods of animal origin – mostly fatty foods, including meat, fish and dairy products including ice-cream. The use of organochlorine pesticides on agricultural crops is also an important route of exposure. While many toxic pesticides have been banned from use, a significant amount of POPs are still being released into the environment as a result of unauthorised use of certain chemicals on crops.

In Europe and the US, the levels of dioxins in breast milk are several times higher than that which is permitted in cows’ milk. Even higher concentrations of POPs are found in the breast milk of Canadian Inuit, who are among the most exposed people in the world. This is because they sit at the top of the food chain in the Arctic regions where they live, consuming a high fat diet of fish and marine mammals. The breast milk of Inuit women contains 2 to 10 times as much PCBs, and 10 times as much chlordane, as the breast milk of women in southern Canada, even though they are thousands of kilometres from the nearest agricultural area.

While most exposure to POPs is at low levels over long periods of time, humans can also be exposed to high concentrations of POPs compounds accidentally, or through their occupations. People working in agricultural industries are at greatest risk of such exposure, especially in developing countries in tropical areas where the use of pesticides containing POPs has resulted in a large number of deaths and injuries. Exposure to dioxins and furans often occurs in an occupational setting, for example during herbicide production. People can also be exposed to acute levels of these substances through industrial accidents and chemical fires.

Another source of high level, acute exposure to POPs is through the contamination of food. PCBs have been linked to several episodes of mass food contamination. In Taiwan in 1978 thousands of people consumed rice bran cooking oil that had been contaminated with a mixture of PCBs and furans. The intake of PCBs from this oil was estimated to be 1000 times higher than the average for Americans, and nearly 10 000 times higher than the average intake of furans. By 1983, over 2000 cases of ‘Yucheng’ or ‘oil disease’ had been recorded by health authorities, all showing signs of acute chemical toxicity.

Finally, people can become exposed to acute levels of POPs compounds under specific circumstances in warfare. One of the best known incidences occurred during the Vietnam war, with the spraying of the defoliant Agent Orang, which was contaminated with the dioxin TCDD.

Health and environmental effects

The impact of these chemical residues in the environment on living organisms and ecosystems is hard to assess, partly because it is difficult to be certain that a specific substance or group of POPs is a direct cause of disease. However, available evidence strongly suggests that POPs are causing disturbances to health in wildlife, in some domesticated species and in humankind. It has been shown experimentally that the feeding of minks with food containing PCB at a concentration of 0.64 parts per million (ppm) leads to a concentration of this chemical in their livers of 1.2 per cent, and to almost complete reproductive failure. Sea otters off the coast of central California have high concentrations of PCB in their livers, which also contain DDT related compounds and other POPs. It is believed that POPs are interfering with reproduction in these animals and in many other forms of wildlife.

There is much suggestive evidence that exposure to POPs as contaminants of human food may result in various forms of ill health, including diabetes, cancer and interference with the immune system and mental processes. As mentioned above, we all have POPs in our tissues. Epidemiological evidence suggests that there may be a relationship between breast cancer and the presence of organochlorine compounds in the body. The incidence of breast cancer has been steadily increasing over the past ten or twenty years in both developed and developing countries. In the USA it has risen 8 per cent in women under 50 years old, and just over 32 percent in women 50 years and older.

Action

As in the case of other environmental problems that traverse geographical and political boundaries, approaches to the control of POPs and other hazardous chemicals over the past couple of decades have been piecemeal, and largely restricted to individual countries. The measures taken have mainly involved the banning of certain POPs and limits on imports. Many countries, but mostly developed nations, have now banned most of the POPs on UNEP’s initial list of 12 compounds. A complete international ban of some POPs, like DDT, would be particularly problematic for developing countries which rely upon this substance for the control of malaria-spreading mosquitos. The World Health Organisation (WHO) is currently taking steps designed to encourage other measures for controlling mosquitos, thereby reducing reliance on DDT.

Before 1992, international actions to control POPs largely involved the development of tools for the assessment of risk, and the identification of priority POPs for management by agencies such has WHO, UNEP and the Food and Agriculture Organisation (FAO). These three agencies formed a joint committee as early as 1963 to evaluate safe levels of pesticides in foods. More recently, in 1989, FAO established an International Code of Conduct for the Distribution and Use of Pesticides, which included certain POPs.

The first major regional agreement was the 1979 Convention on Long-Range Transboundary Air Pollution, but this was not actually completed until 1998. It contains a specific protocol aimed at the control, reduction and prevention of the release of POPs into the atmosphere, and it includes specific criteria for the further identification of POPs. Sixteen POPs are covered in this convention. Thirty six countries have now signed the agreement (no developing nations are included), and it entered into force in October 2003. While this treaty deals with POPs in the atmosphere, other treaties, have addressed the threat and control of toxic chemical substances, including POPs, in the marine environment.

Following initiatives by UNEP, a Diplomatic Conference was held in Stockholm in 2001, leading to .the Stockholm Convention that entered into force in May 2004. This Convention sets out control measures for the initial list of 12 chemicals, covering the production, import, export, disposal and use of POPs. The governments of individual countries are required to develop national legislation and action plans in order to fulfil their commitments. They must also promote the best available technologies and practices for replacing existing POPs, while prohibiting the development of new POPs. There is also the provision of a financial mechanism, the POPs Club, through which the international community help developing countries to meet their obligations to minimise and eliminate POPs.

There are now several international and national registers containing data on chemical stocks, and details on emissions, including POPs. These are known as Pollutant Release and Transfer Registers (PRTRs). This kind of database also helps communities identify the worst polluters, and bring public attention to the issues of hazardous chemicals, waste management and the threats these place on public health. Details of Australia’s National Pollutant Inventory can be found at www.npi.gov.au. Consumers play a vital role in reducing the use of POPs, as can be seen in the growth of the organic food industry in response to community concern over the health effects of the use of chemical pesticides and fertilisers in foods.

These efforts to reduce the production, use and emissions of POPs are currently hindered by the slow development of cost-effective alternatives to these chemicals. Although a variety of chemical and non-chemical alternatives to POPs exist, there are many barriers preventing the widespread adoption of such technologies, foremost their high cost. Financial mechanisms in the Stockholm Convention and other agreements attempt to address this problem, especially by providing assistance to developing countries.

There is still a shortage of data the amount of POPs still used, the reasons for use, available alternatives and impediments to the adoption of alternatives in different countries. However, several industries and communities have begun to implement new technologies, especially for waste management and pest control, and these play a crucial part in the broad shift away from harmful chemicals to alternative practices and cleaner production methods.

Further reading

For further information see

www.chem.unep.ch/pops
www.pops.int/documents/convtext/convtext_en.pdf

Alice Thompson was brought up with an appreciation of, and interest in the environment, leading her to study at the Australian National University, majoring in Geography/Human Ecology and Population Studies, and her involvement in the Nature and Society Forum (NSF). She now lives in Sydney where she currently pursues a career in Government working for the NSW Office of the Australian Bureau of Statistics (ABS). Before joining ABS Alice was employed by NSF as a Research Officer to prepare reports on important ecological issues in Australia.

This paper as a [103 kb pdf]

2012-06-18T14:44:24+10:00 2012-06-18T14:44:24+10:00 roba Climate change http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/climate-change Enhanced greenhouse effect, Earth's atmosphere

Alice Thompson

The evolution of the Earth’s atmosphere
What is the greenhouse effect?
History of concern
Recent debates
Facts
Climate predictions
Action
Australian emissions
Summary

The evolution of the Earth’s atmosphere

The atmosphere - When our planet was very young it did not have an atmosphere. But as time went by gases emitted from the Earth’s crust and from volcanoes accumulated at the surface. These gases were probably similar to those emitted from volcanoes today, and when the earliest forms of life came into existence the atmosphere probably consisted mainly of nitrogen and carbon dioxide, but without any oxygen.

The first living things were single-celled bacterium-like organisms. Except for sub-cellular viruses, these were the only form of life on the planet for a thousand million years. Their immediate sources of energy are believed to have been energy-containing chemical compounds formed through the action of UV radiation and of electrical discharges in storms.

Photosynthesis - It was the emergence, in evolution, of photosynthesis that resulted in the eventual accumulation of oxygen in the atmosphere, and that made possible the evolution of more complex forms of life, including the plants and animals of the present day. Single-celled organisms capable of photosynthesis, cyanobacteria, are thought to have been in existence by around 2 800 million years ago.

Some of the oxygen released into the atmosphere in photosynthesis was converted to ozone, and accumulated in the layer of the upper atmosphere known as the stratosphere, where it acted as a filter, absorbing much of the ultraviolet radiation from the Sun. As a result, by the time that humans appeared on Earth, and probably by two thousand million years before that, only about half of the total solar ultraviolet radiation, and a much smaller fraction of the short-wave UV-B rays, penetrated to the surface of the planet. Life as it exists on land today would not have been possible had it not been for this development.

Atmosphere changes - Evidence from ancient rocks indicates that there have been big changes in the composition of the atmosphere over time. Early in the history of the planet there was a very high concentration of carbon dioxide, and other gases like hydrogen, sulphur dioxide, carbon monoxide, ammonia, methane and hydrogen sulphide were also present. Later, the concentration of carbon dioxide was greatly reduced, and oxygen became abundant. Nitrogen has probably always been present in a concentration similar to that in today’s atmosphere.

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What is the greenhouse effect?

The atmosphere allows light energy from the sun to penetrate to the Earth’s surface, where it is converted to heat energy. This causes the surface of the Earth to warm up, but much of this heat is re-radiated towards the highest parts of the atmosphere and back into space. Some of this outgoing radiation is absorbed by certain gases in the atmosphere, and then re-radiated in all directions. Thus some of it is directed back to the surface of the Earth, and because of this effect the average temperature at the surface of the planet is some 34° C higher than it would otherwise be. The gases which cause this so-called greenhouse effect are called greenhouse gases.

The natural greenhouse gases include: water vapour (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O) and ozone (O3). Other gases, like carbon monoxide (CO), sulphur dioxide (SO2) and nitrogen oxides (NOx), play an indirect role by influencing the levels of other greenhouse gases.

Figure 1 The Greenhouse Effect

Greenhouse fig2 1

That the greenhouse effect exists has been well accepted in scientific circles for over a century. It is a natural phenomenon, and without it our planet would be much too cold to support life as we know it.

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History of concern

The first scientific papers suggesting that continued combustion of fossil fuels could lead to global warming were published in the 1890s. In the late 1950s it was calculated that about half the carbon dioxide from the burning of fossil fuels was remaining in the atmosphere, and during the 1960s and 1970s, many studies confirmed the potential for climate change due to rising carbon dioxide levels. Various other trace gases were also identified as greenhouse gases. The first multi-dimensional climate models were being developed at this time.
It was not until the late 1980s that the issue of long-term global warming due to increasing emissions of greenhouse gases came to widespread public notice, leading eventually to the development of various international initiatives, including the establishment of the Intergovernmental Panel on Climate Change (IPCC) in 1988, and the Kyoto conference in 1997. These developments are discussed below.

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Recent controversies

Human activities The main debate over recent years has focused on the degree to which the release of greenhouse gases as a result of human activities, are causing, or are likely to cause, global climate change.

At present the great majority of atmospheric scientists agree that we are already beginning to live with the effects of an enhanced greenhouse effect resulting from human activities, experiencing warmer temperatures, rising sea levels and significant changes in weather patterns. There are still uncertainties, however, about the precise nature of these changes, especially at regional and local levels.

According to the prevailing view, whatever actions might be taken in the future to reduce greenhouse gas emissions, we are already committed to significant climate change due to the greenhouse gases that have already been released into the atmosphere. However, there is some disagreement about the degree to which climate changes that have occurred in recent decades are attributable to the increasing concentrations of greenhouse gases in the atmosphere. This uncertainty has led to confusion among the general public about the urgency of the problem, and has impeded the introduction of policies aimed at effectively reducing greenhouse gas emissions.

The information presented here is based largely on reports of the IPCC and of Australia’s CSIRO Division of Atmospheric Science. As in most areas of environmental concern, there are other viewpoints, although there is no disagreement about the fact carbon dioxide concentrations in the atmosphere are rising significantly as a result of human activities.

Greenhouse gases and growth - The greenhouse gases produced by human society include the naturally occurring gases carbon dioxide and methane, as well as some synthetic compounds like CFCs and HFCs. The increasing production of greenhouse gases is a function not only of population growth, but also, and more importantly, of our current economic arrangements and lifestyles associated with exceptionally high rates of resource and energy use and technological waste production. Thus the quantities of these gases released by different countries are closely correlated with levels of consumerism and economic growth.

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Facts

The concentration of carbon dioxide in the atmosphere has increased over 30% since the beginning of the industrial revolution phase of human history. Towards the end of the last century the concentration increased on average by 0.4% per year (Table 1 - source).

Table 1

	Carbon dioxide	Methane	Nitrous oxide	CFC-11
Current concentration	370 ppmv	1720 ppbv	312 ppbv	260 pptv
Pre-industrial concentration (~1700s)	288 ppmv	850 ppbv	285 ppbv	0
Annual rate of increase	0.4%	0.6%	0.25%	0*
Atmospheric lifetime	50-200 years	12 years	120 years	50 years

According to CSIRO Marine and Atmospheric Research scientist, Dr Mike Raupach, who is the co-Chair of the Global Carbon Project, the growth rate of carbon dioxide emissions is accelerating. He writes:

‘From 2000 to 2005, the growth rate of carbon dioxide emissions was more than 2.5 per cent per year, whereas in the 1990s it was less than one per cent per year’.

The atmospheric concentrations of carbon dioxide, methane and nitrous oxide over the past 1000 years are shown in Figure.2, which nicely illustrates the increasing impact of human activities since the industrial revolution.

Figure 2

fig2 climate change

The global average surface temperature has increased during the 20th century by approximately 0.6°C. Temperatures in Australia have risen over this period by 0.5ºC to 0.9ºC which, on average, is higher than mean global trends. The 1990s have been the warmest decade globally, and 2005 has been the warmest year on record. Longer term observations from tree rings, corals and ice cores suggest that the rate of warming during the 20th century was greater than that seen in any century of the past 1000 years, and the trend is continuing (Figure.3).

Figure .3

Greenhouse fig2 3
Ice and snow - Corresponding with the increase in average surface temperatures globally, there has been a general decrease in snow cover and ice extent around the world. Observations in the Northern hemisphere suggest that there has been a diminution of 10% in the extent of snow cover since the 1960s. The extent of seasonal sea-ice has also decreased by between 10-15% over the past 100 years and mountain glaciers in non-polar regions have retreated considerably.

Sea level - The past century also experienced an increase in average sea levels around the globe in the order of 0.1 to 0.2 metres. Sea level measurements in the Australasian region reflect this general mean trend, and appear to have risen about 2mm per year over the past 50 years.

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Climate predictions

A range of climate models and climate change scenarios have been developed by different scientific organisations. The scenarios project future climatic conditions based on different estimations of greenhouse gas emissions, taking account of a range of assumptions regarding economic growth, emissions controls, the availability and use of energy, patterns of agriculture and land use, the use of halocarbons and CFCs and levels of population.

According to the IPCC, the average surface temperature globally is projected to increase by 1.4 to 5.8ºC by the year 2100. This rate of increase in temperature is greater than any seen in the last 10 000 years.

In regional scenarios developed by CSIRO, it is projected that by 2030 Australia will experience warming in the order of 0.4 to 1.4ºC in inland areas, 0.3 to 1.0ºC in northern coastal areas, and 0.3 to 1.3ºC in southern coastal areas.

Extreme weather - All global models predict an increase in the frequency of high temperatures coupled with a decrease in the frequency of extremely low temperatures. In addition, precipitation will be affected, with projected increases in high rainfall events over the next century. Some regions may experience more severe floods and droughts, while in other areas such extreme weather events may be reduced. There is greater uncertainty about the extent to which other extreme weather events – like cyclones and tornadoes – will be affected, although they are likely to increase.

Ice and snow - It is projected that snow cover and sea-ice extent will continue to decrease over the coming century in northern regions of the world, along with the widespread retreat of glaciers and icecaps. Paradoxically, the influx of cold fresh water into the North Atlantic Ocean could shut down that Ocean’s circulation, cutting off the Gulf Stream and plunging western Europe into an ice age. It is possible that the ice sheet in the Antarctic may actually gain mass, due to an increase in precipitation.

The loss of mass from glaciers and icecaps around the world, as well as the increased thermal expansion of oceans, are predicted to lead to an overall increase in global mean sea level of 0.09 to 0.88 metres between 1990 and 2100.

Temperature rise - Even if concentrations of greenhouse gases could be stabilised by 2100, it is likely that global temperature will keep rising beyond that time due to thermal inertia of oceans and the continued presence of emissions in the atmosphere.

Although the great majority of climate scientists agree that global warming is taking place, there is much uncertainty about the actual degree of temperature change. This is because the situation really is extraordinarily complicated. For example, some recent evidence suggests that an increase in certain human-induced aerosols in the atmosphere may be causing a decrease in solar radiation reaching the Earth’s surface, resulting in a certain cooling effect and a reduction in the rates of evaporation of water.

Biological adaptation - Given the complexity of ecosystem interactions, it is very difficult to predict how different life forms will be affected by long-term climatic variations. However, the ecological changes are likely to be beyond the adaptive capacity of many species, leading to widespread extinctions.

Soil moisture levels are likely to be affected by changes in temperature and precipitation, with disruption of established water and nutrient cycles. Plant productivity and species interactions, such as competition, predation and parasitism are also likely to be affected. Increases in the occurrence of fire and outbreaks of insects would have further impacts.

Human wellbeing - Human health and wellbeing will be significantly affected by climate change. It is likely that a greater frequency of high temperature events will result in higher levels of heat stress mortality across populations. Warmer temperatures will also extend the range of disease-carrying vectors, like mosquitoes, exposing greater numbers of populations to tropical vector-borne diseases such as malaria and dengue.

Rising sea levels will threaten the homes and livelihoods of millions of people living in low lying, fertile and densely populated coastal areas – for instance, in Bangladesh and the South Pacific Islands.

Significant impacts on agricultural production are predicted. Any increase in crop production due to higher CO2 levels is likely to be offset by greater variability in precipitation.

Greenhouse or ice age? - An argument put forth by the business-as-usual school of thought is that increasing global temperature will be a good thing, or at least better than global cooling, and that the enhanced greenhouse effect may be protecting us from the onset of another ice age. A contrary viewpoint is that if fossil fuels really have the potential to prevent another ice age – then surely we should be saving them up until there is clear evidence that the planet is, in fact, entering such an ice age.

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Action

International climate action - The concern expressed by scientists about the enhanced greenhouse effect over the past couple of decades has resulted in a considerable amount of discussion and debate internationally. One of the most significant developments was the establishment in 1988 by the United Nations Environment Program and the World Meteorological Organisation of the Intergovernmental Panel on Climate Change (IPCC). The role of the IPCC is to assess information related to climate change issues and to formulate realistic response strategies for the management of climate change issues.

Another important development was the United Nations Framework Convention on Climate Change, which was signed by 155 States at the Rio Earth Summit in 1992, and entered into force in 1994. It provides the overall policy framework for addressing the climate change issue. The ultimate goal of this Convention is to:

‘achieve....stabilisation of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system...Such a level should be achieved within a timeframe sufficient.....to enable economic development to proceed in a sustainable manner.’

Signatory parties are committed to taking steps to achieve this objective under the Convention. Since developed countries have been largely responsible for past and current emissions, some of them have agreed to take the lead in stabilising and reducing emissions. Developing countries are also committed to taking action, but this will depend on the provision of assistance by developed countries. Action to be taken by all parties includes the provision of information and promotion of educational programs about climate change, as well as the adoption of policies and measures that aim to reduce emissions of greenhouse gases.

Kyoto Protocol - The Framework Convention provided for signatories to meet annually to discuss and review the latest in climate change science, and assess the adequacy of the policy response at a series of Conferences of the Parties (COP). These meetings led to negotiations aimed at strengthening commitments to the Framework Convention, resulting in the development of the Kyoto Protocol. The text of the Kyoto Protocol was agreed to at the third COP in 1997. The most important feature of the protocol is the emissions targets for OECD and Eastern European countries. These parties agreed to reduce aggregate CO2 emissions by 5.2% of 1990 levels by 2008-2012. The Protocol allows for specific targets to be set for individual countries that take into account differing economic circumstances and capacity for change, and also includes several flexibility mechanisms along with options for carbon sequestration.

The pact could not come into force until it was ratified by countries accounting for at least 55 per cent of the greenhouse gas emissions of developed nations. It finally became law in February 2005 after eventual ratification by Russia. The Protocol was ratified by Australia in December 2007. The United States of America has so far refused to ratify the treaty.

In July 2005 the United States, China, India, Japan, South Korea and Australia agreed to form an Asia-Pacific Partnership on Clean Development and Climate. These six countries are responsible for about 50 per cent of global greenhouse emissions. The first meeting of ministers met in Sydney in January 2006. The group says it complements, but does not replace the Kyoto Protocol, and that they ‘will work together to develop, deploy and transfer cleaner, more efficient technologies and to meet national pollution reduction, energy security and climate change concerns’. So far there are apparently no commitments among the members of the group to meet any target or to take any specific action.

Contraction and convergence - An alternative plan for reducing carbon emissions has recently been proposed. It is known as the ‘contraction and convergence, or ‘C and C’. Essentially, this proposal suggests that all countries aim for the same rate of carbon emissions on a per capita basis – say 0.3 tonnes per year (the average today is about one tonne per year per person). This would mean a very substantial drop in carbon dioxide emissions in the developed countries, but would allow an increase in some developing regions.

Geosequestration - Finally, reference must be made to the proposal that the carbon dioxide produced, for example, in coal or petroleum-powered electricity generating plants, should be sequestered below ground. The idea is that the CO2 would be separated and then compressed to a dense ‘supercritical state’. If this material is injected underground, at a depth of 800m or more, it will remain in that dense state for thousands of years or longer. Proponents of this idea believe that the technology is available to do this, although other scientists are doubtful about its practicability. Much research is underway and the technique is being trialled in some countries.

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Australian emissions

Australia has an unusual emissions profile in comparison with other industrialised nations. While this country is a relatively small producer of greenhouse gases, accounting for only 1.4% of total global emissions, our emissions per capita rank third among all nations. This has been attributed to the abundance of fossil fuel resources in Australia which has influenced the Australian economy and trade profile, and to our high dependence on fossil fuel based transport.

Although energy production and use is a major source of greenhouse gases, accounting for almost 65% of our total emissions, non-energy sectors are more significant in the Australian inventory than for most other OECD countries. Emissions from the agricultural sector result in an unusually large proportion of methane in the national emissions profile, although, CO2 still dominates total emissions.

Another distinctive feature of Australia’s emissions profile is that certain activities in the forestry sector, such as clearing, are an important source greenhouse gas. It has been estimated that in 1990 carbon dioxide emissions resulting from forest clearance amounted to 156 million tonnes, or 27.3 per cent of this country’s net emissions: and the rate of clearance has increase considerably since that time.

Despite all current measures, and being signatory to the Framework Convention on Climate Change, Australia’s total emissions are projected to increase by 18% from 1990 to 2010.

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Summary

Globally, the situation can be summarised as follows:

1. Human technological activities involving the combustion of fossil fuels are resulting in progressive increase in the concentration of carbon dioxide in the atmosphere of our planet. The concentration is still increasing, at a rate of 0.4% per year.The concentrations of two other greenhouse gases, methane and the CFCs, which were increasing until recently, seem to have stabilised.

2. Most atmospheric scientists, including members of Australia’s CSIRO Division of Atmospheric Science, predict that this increase in carbon dioxide in the atmosphere will result in progressive global warming, with uncertain consequences for humankind.

3. Climate change due to the release of greenhouse gases by human society is an issue that calls for governmental decision-making on a scale and of a kind not seen before in human history. Given the progressive and cumulative nature of the problem, the longer effective action is postponed, the greater the problem will become, and the more difficult it will be to address.

Further reading

For further information see:

(1) the various reports of the Intergovernmental Panel on Climate Change (IPCC)

(2) The Nova website of the Australian Academy of Science

(3) The United Nations Environment Program

Notes

The stratosphere - The stratosphere is the zone in the atmosphere that exists between an average of 15 and 50 km above the surface of the planet, lying between the lowest layer (the troposphere), and the mesosphere. In the stratosphere temperature increases with altitude.

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Author

This paper as a 155KB PDF

2012-06-18T14:40:00 2013-10-21T15:49:53+11:00 roba Biodiversity http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/biodiversity Paper 1.8 - Part 1B - Ecological issues

by Alice Thompson

Contents
The value of biodiversity
Explaining patterns of diversification
Current Concerns
Endangered Australia
Threats to biodiversity
Action – responses to the loss of biodiversity
Further Reading

The word biodiversity is a very recent addition to our vocabulary. Originating from the National Forum on BioDiversity, hosted by the US National Academy of Sciences and the Smithsonian Institute in 1986, the concept of biodiversity has spread beyond scientific circles and is now recognised by many people and cultures around the world.

The term is really self-explanatory, being simply a contraction of the words ‘biological diversity’, and it is used to refer to the variability and complexity among living organisms and ecosystems on the Earth. The fact that the word has spread so quickly reflects our sudden appreciation that biodiversity is now rapidly declining worldwide as a result of human activities.

Biodiversity is generally considered on three levels: genetic diversity (diversity within species), species diversity (diversity between species) and ecosystem diversity.

The value of biodiversity

The reasons put forward for protecting biodiversity can be grouped under two headings: use-values and non-use values.

Use values

The biological success of the humankind, especially since the introduction of farming, has involved the exploitation of biodiversity. Consider the amazing range of different species and varieties of plants and animals that are grown to provide food for human populations, to say nothing of the trees used for paper products and building materials and the plants used for medicines, fibres, dyes, pesticides, flavouring agents and oils. Fungi, yeasts and bacteria play essential roles in bread making, brewing, and the production of dairy products like yoghurt and cheese. And insects, as well as some birds and mammals, play a vital part as pollinators in our agricultural systems.

There are also other less direct ways that different plants, animals and microbes are useful to humankind – for example in the maintenance of atmospheric quality, the disposal of wastes, the recycling of nutrients, the generation of soils and the control of pests. It is also often pointed out that biologically diverse ecosystems harbour rich gene pools, many components of which might well be found to be beneficial for humans in one way or another at some time in the future.

Non-use values

The non-use reasons for protecting biodiversity are essentially ethical and aesthetic. There is a strong body of opinion that it is morally wrong to cause the extinction of other forms of life unnecessarily. And for many people biodiversity provides an endless source of interest, enjoyment and wonderment, and it is a great source of inspiration for different kinds of creativity.

Explaining patterns of diversification

Over evolutionary time there has been a clear trend of increasing biodiversity, in both marine and terrestrial environments. Over the past 500 million years this increase has proceeded in a somewhat punctuated fashion. Periods of great diversification have been followed by periods of relative stability, and sometimes even decline in biodiversity.

Not all groups of organisms have diversified at the same time. For example, the extraordinary diversification of mammals over the past 60 million years has been far more spectacular than the diversification among reptiles in the same period.

The fossil record indicates that all species have a finite span of existence over geological time, and it is believed that roughly 99% of all species that ever existed on Earth have become extinct. The Global Biodiversity Assessment estimates the average life span of fossil species to be between 1 million and 10 million years. This would mean that on average around two to three species would be likely to become extinct each year from natural processes worldwide.

Rates of extinction have varied greatly over time, ranging from mass extinctions where many species have been lost in a relatively short period, to background rates of extinction, with a gradual loss of species over time. There have been five periods of mass extinctions. The most severe episode occurred around 250 million years ago, when around 96% of marine animal species disappeared, with terrestrial organisms also significantly affected. The latest mass extinction took place about 65 million years ago when all the dinosaur species disappeared, as well as 10% of families of terrestrial organisms and 15% of families of marine organisms.

Even so, over the past 66 million years mass extinction has accounted for only around 4% of total extinctions. Seventy five to 95% of animal species alive at the beginning of the period are believed to have become extinct.

On a geological timescale, the rates of recovery of biodiversity following mass extinction are comparably rapid, although it takes around 5-10 million years for some communities to properly recover and re-establish, and when this happens the pattern of biodiversity is often quite different from that which prevailed before the extinction event.

The rate of background extinctions has not been constant either. At present the average rate of background extinction is very low. In fact it is so low that there is no documented case over the past hundred years of the extinction of any plant or animal species caused by non-human agencies like competition, disease or environmental factors.

Current Concerns

There are now believed to be some 7 million to 15 million species of animals, plants, fungi and micro-organisms (excluding bacteria and viruses) on Earth. Of these, around 400 000 are plant species and around 50 000 are vertebrates.

Since 1600, around 484 animals and 654 plant species are recorded as having become extinct, and it is certain that countless other species have also disappeared without being documented. Within this period, the actual recorded rate of extinctions has dramatically increased, with three times as many species of birds and mammals recorded as becoming extinct since 1810 as were recorded between 1600 and 1810. Over half of the known extinctions of the past 200 years occurred worldwide in the 20th century. They have been particularly numerous on islands, island archipelagos, and in fresh water ecosystems. About 75% of extinctions among animals occurred on islands.

Even when we take into account the many uncertainties surrounding the comparison of past and recent rates of extinction, current rates far exceed the natural background rates that appear in the fossil record. Over the past 250 million years, approximately 1 species became extinct per year. It has been estimated that around 50 species are now being lost every day, some of which have never been described. According to one estimate 140 000 species are now becoming extinct every year. At this rate we will wipe out half the existing species in 70 years. Over 34 000 species of plants face extinction, and among animals, mammals are now recognised to be much more endangered than birds

It is feared that climate change resulting from an enhanced greenhouse effect will further increase the rate of extinction.

Endangered Australia

Australia is one of the twelve most biologically diverse countries in the world, due to its size, lengthy isolation and many climatic zones. However, there is still limited knowledge about the level and extent of this biodiversity, and it has been suggested that only about 15 per cent of Australian species have been described.

At present the Australian continent has the highest record of recent mammal extinctions in the world, with 10 out of 144 species of marsupial and 8 out of 53 species of native rodent becoming extinct over the past 200 years. Two hundred and sixty four of Australia’s 1247 bird species and subspecies are estimated to be extinct or at risk.

The 1996 State of the Environment Report found that the loss of biodiversity was perhaps the most serious local environmental problem facing Australia today.

Threats to biodiversity

Species decline can result from a number of factors and it is difficult to identify the primary cause in individual cases, partly because there are usually several threatening processes operating simultaneously. Box 12.1 describes the major categories of threats and causes of species decline and extinction.

Box 12.1

Main categories of species decline

Habitat destruction

Loss of habitat is a key factor in population extinction, especially on small spatial scales. It is largely a result of vegetation clearance for pastoral development, cultivation and settlement, although forestry and mining operations, fire and pollution also significantly contribute to loss of habitats around the world.

Changes in habitat quality

This is a less extreme form of environmental change, although it can lead to significant decline in animal and plant populations. An example is loss of biodiversity as a result of climate change, which in the near future may well be too rapid to allow adaptation in many species. Alteration of habitats by chemical pollution is another major factor leading to the decline of species around the world.

Changes in the Australian landscape through the repeated and deliberate firing of vegetation by Aboriginals is considered by some to have contributed to the extinction of several large vertebrate species (megafauna).

Habitat fragmentation

The fragmentation of habitats through rural and urban developments can cause a previously continuous and stable population structure to disintegrate, with local populations becoming so small that they are at risk of extinction. The disruption of habitats interferes with the usual foraging and breeding behaviour of species that are adapted through evolution to a more continuous habitat.

Together, these three habitat changes account for over 90% of cases of species decline and extinction

Persecution and overexploitation – This can result from commercial or subsistence activities, and it represents a significant threat to many species of animals, particularly large vertebrates. It includes hunting for meat, hides or fur and collecting wild species for the pet trade and plants for horticulture.

During the Pleistocene epoch (from 1.8 million to 12 000 years ago), the extinction of large mammals (megafauna) and flightless birds closely coincided with the arrival of humans in North America, Madagascar, Australia and New Zealand. While climate change is likely to have been a significant factor in the extinction of some of these species, most authorities believe that predation and overexploitation by humans greatly contributed to their demise. This category of threat also includes the deliberate eradication of species considered to be pests, as well as species killed as incidental catches in aquatic environments.

The introduction of exotic species

The spread of exotic, or non-indigenous, species is second only to habitat destruction in harming native communities. They can reduce biodiversity in an area by competing with, or preying upon native species, The human-enhanced spread of infectious diseases and parasites is also a major threat to many animal and plant species.

It is noteworthy that while human activities have resulted in the extinction of large number of species of animals and plants, they have also actually brought about an increase in biodiversity within some species. A whole range of novel genetic forms of life have come into existence that would never have seen the light of day were it not for humankind, and this happened long before the development of the genetic engineering of the modern era.

In the case of animals, selective breeding has given rise to a fantastic range of varieties of cattle, sheep, goats, pigs and poultry. The effects are particularly striking in the case of dogs, in which the criteria for selection have not usually been related to the animal’s food value. It is true that some breeds of dog, such as sheep and cattle dogs, are the result of deliberate selection for behaviour of practical value to humans. But many others, like the Pekinese, Chihuahua, Toy Poodle and Great Dane, simply reflect the frivolous whims of generations of dog-fanciers.

The number of new genetic varieties of plant species brought into being through human activities as sources of food and as garden plants is astronomical.

Most of these novel genetic forms both of plants and animals are not only the product of human cultural intervention, but they are also dependent on human culture for their continued survival. They would quickly disappear if humankind were suddenly to vacate the scene.

Action – responses to the loss of biodiversity

In the face of declining species and rapidly degrading habitats around the world, numerous multi-lateral treaties and international agreements have arisen over the past three decades. While many of these treaties have been commended for their global coverage and innovative approaches, most only deal with biodiversity in part, and they have evolved in a piecemeal and uncoordinated manner.

It was not until 1992 that international negotiations for a legally binding instrument to conserve the components of biological diversity were initiated. The Convention on Biological Diversity, opened for signature on 5 June 1992 at the United Nations Conference on Environment and Development, was developed in response to global concern over the loss of genes, species and ecosystems, and to the growing recognition of the immeasurable value of biological diversity to present and future generations. This was the first comprehensive international agreement to address the loss of biodiversity. The primary objectives of the Convention are the conservation of biological diversity, the sustainable use of its components, and the fair and equitable sharing of benefits arising out of the utilisation of genetic resources.

The Convention entered into force on 29 December, 1993, with 168 signatory countries. All signatory countries take responsibility for the conservation and sustainable use of their own biological diversity, and are also required to cooperate in matters of mutual or shared interest. The Convention promotes partnerships between countries, through scientific, technical and financial transfers. A financial mechanism requires developed countries to provide new and additional financial resources to assist developing countries meet their obligations under the Convention.

Australia is a signatory to this Convention and is party to many other international and regional agreements that are relevant to the conservation of biodiversity.

At a national level, the protection of biodiversity and maintenance of essential ecological processes and life-support systems is one of three core objectives of the National Strategy for Ecologically Sustainable Development (1992).

However, until recently there was no broad legislation in Australia to conserve and maintain biodiversity. Instead, many laws relating to the management of flora and fauna have been passed over the past century, but like early international conservation attempts, they have occurred in a piecemeal manner, with few specifically targeting biodiversity. The States and Territories have been largely responsible for the management of species and protected areas, and are party to a number of state and national strategies for the conservation of natural biological resources.

The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) has provided a single national scheme for the protection of the environment and the conservation of biodiversity. Most importantly, this Act aims to promote a partnership approach to environmental protection and biodiversity conservation through bilateral agreements with States and Territories, conservation agreements with landholders, recognition and promotion of the role of indigenous people and involvement of local communities the community in management planning.

Largely as an outcome of the activities of community-based environmental groups, public awareness of the biodiversity issue has gained momentum over the past few decades, and it has now emerged as an issue of key concern for many Australians. These groups include large international organisations, like Greenpeace and World Wide Fund for Nature (WWF) and national organisations such as the Australian Conservation Foundation (ACF) and the National Parks Associations.

Many groups regularly monitor the environment providing information that has contributed to our knowledge and understanding of the diversity of organisms and ecosystems. Unfortunately the activities undertaken by these community groups are often costly and time consuming, and most of the input is on a voluntary basis.

There are now several community-government initiatives involving collaboration between community groups, conservation organisations and government bodies. Examples are Greening Australia, and the One Billion Trees campaign, which arose in response to the loss of native vegetation. There have also been many community networks established, like the Community Biodiversity Network and the National Threatened Species Network, which aim to achieve increased community support and involvement in the protection of threatened species and their habitats. Landcare has been a crucial community-government initiative that has provided a mechanism for the conservation of biodiversity alongside agricultural and pastoral production.

It remains to be seen whether these encouraging developments in Australia and overseas will be sufficient to stem the tide of human-induced extinction of animal and plant species.

Introduction

Energy provided naturally at no economic cost, by thermonuclear reactions in the sun, by gravitational forces near the core and mantle and by radioactive decay of uranium and thorium in the crust, sustains life on this Earth. But Earth’s population is rapidly rising to levels too high for its resources to support and the very existence of the human race is under challenge. The variability of the sun’s emission together with changes to the earth’s orbital parameters has resulted in huge shifts in climate and hence in the biosphere over past aeons. During the rise of the human species these shifts have produced many destructive periods which have threatened survival but the adjustment of behaviour to live through those challenges has assisted the development of speech, thought and with them, our culture and society.

Competition for natural resources and the innate drive within the human psyche for the individual to want a "fair" share of those resources was a driver for advancement when the population was largely sustainable. The choice of a particular energy resource was determined by availability, abundance and technology. Coal and later oil became the obvious choices to replace wood and made possible the industrial revolution, the capitalist culture and the rise of consumerism. While a few people foresaw that mankind’s striving for growth and wealth may not be sustainable, the governing paradigm did not allow for the huge increase in the demand for energy, the environmental costs or the eventual depletion of resources. The need to sustain a viable population well into the future, requires society to recognise that each member must live within certain energy and resource limits consistent with the availability of those resources on this planet.

Energy criteria

The essential characteristics of the new bio-sensitive society will determine the criteria which any energy option must satisfy for sustaining that society through the various natural events which will affect its existence in regional areas and ensure the health and well being of the global community. The criteria listed below, necessary for achieving and sustaining a bio-sensitive society presume the characteristics in the PAN paper "Our place in Nature".

No harmful pressures on the ecosystems of the biosphere through the influence of pollutants of all types.
Sufficient resources to sustain the population in a manner that allows adequate food, health, and shelter for all.
Maintenance of all fields of education, creativity and research.
Support for technological enterprises and development consistent with maintaining the ideals of the society.
Maintenance of local and global communications systems, to ensure the free exchange of ideas.
Maintenance of a sustainable local and global transport system that allows free interchange of personnel and ideas within and between nations.

These criteria imply a static global population at a level at which every individual has a sufficient share of resources to maintain a satisfying lifestyle. Each person will have to consume less energy in such a situation than the majority consume in the present consumer-capitalist society.

The current view amongst the governing few that technology can maintain a growing global society in the style enjoyed by the rich and developed nations, predicates that the resources required for its sustainability will far exceed those available on Earth. The present rise in oil prices reflects the fact that the ‘peak’ in oil production is here now or only a decade away. It is the most important, and the first, of the fossil fuels to reach production levels that threaten widespread economic and political disruption in the future unless drastic measures are taken to provide alternative solutions.

The bio-sensitive society then appears to mirror many of the attributes considered by Ted Trainer in his "simpler way" ¹,

"a society based on non-affluent but adequate living standards, high levels of self-sufficiency, in small scale localised economies with little trade and no growth, to basically co-operative and participatory communities, to an economy that’s not driven by market forces and profit, and most difficult of all, a society that’s not motivated by competition, individualism, and acquisitiveness. Many have argued that this general vision is the only way out of the mess we’re in."

This may well be an unachievable ideal, particularly when one considers that even within a bio-sensitive society there will still be a distribution of personal character traits with the more disruptive elements of all types at the two extremes. These will have demands and behaviours counter to the ideal peaceful existence of the majority. The narrower that distribution the better but the possibility of extreme elements attempting to disrupt energy sources and distribution systems requires that they be distributed and robust against attack. However the above ‘simpler way small scale’ societies cannot exist in isolation from their neighbours. A high degree of interaction will be essential between these groups to satisfy their transport, education, health and cultural needs. Unless these societies are close enough to avoid large scale energy requirements for that interaction to proceed, then the concept becomes questionable.

Fred Pearce², shows that very large cities achieve economies of scale despite the serious impacts they are presently having on the environment. Certainly in energy terms the distribution of energy to a large population is far more efficient in a large metropolis than to a similar sized population scattered in small-localised urban communities. However the provision of that energy via large centralised power stations and all-encompassing grids covering many large cities is not the most efficient, whatever the type of generation employed. The production of energy from all available local sources (a high degree of distributed and co-generation) feeding through local grids or pipelines to users, ensures greater efficiency and equity. Also communication, health, educational, cultural, manufacturing and technological facilities can be provided to large conurbations at much lower energy cost than to large groupings of separated small communities.

Pearce points out that the most significant technology that mitigates against maintaining both a large metropolis and alternatively, distributed small villages, as bio-sensitive societies is the motor vehicle and its associated road infrastructure. Significant also are the energy costs of food and goods transport within and between nations via sea and particularly air. For the metropolis, provision of adequate food and water supplies from local sources, disposal of waste of all types, and inefficient transport, together with the "heat island’ effects, are serious problems requiring solution before a megacity can achieve the advantages of a closely knit coherent and bio-sensitive society . On the other hand if those problems can be solved while maintaining the bio-sensitive criteria then the megacity does offer economies of scale that can minimise the energy needs compared to Trainer’s localised small villages. In the present context therefore a megacity will consist of a very large and high-density population with an overall design that minimises its energy requirements while maintaining a satisfying lifestyle consistent with the themes of this paper.

Technology has provided spectacular growth for the more privileged sectors of society over the last 100 years, but at huge energy and environmental costs. However the enemy has not been technology per se, but its misuse in the scramble for wealth and economic growth. Research and development with their application through technology in all areas will be essential to the global societies’ overall needs and to perhaps changing the present dysfunctional megacities into viable communities for the future.

Energy Options

A major factor in the success of any future society will be the ability to supply the majority if not all, of its total needs from local and sustainable sources. Recycling of all wastes and materials will be essential while the sources of overall energy requirements must be greenhouse-gas neutral. This latter condition assumes that the global greenhouse gas concentrations are contained at a level consistent with a stable climate influenced only by natural events. It also assumes that greenhouse gas emissions are still possible but balanced by sequestration techniques that do not cause other environmental problems. In this balance it will be essential to take into account the lifetimes that the various gases take to circulate through the atmosphere. For example a sudden large emission which spikes the global carbon dioxide concentration can take 100 years to decay back to normal levels.

The energy sources available locally to all communities are solar, wind, methane (from anaerobic human and animal waste digestion), and plant biomass. A secondary source is local geothermal energy via geothermal heat pumps (GHP) which use electricity to pump heat between the surrounding ground some 100 metres or so deep and the local buildings.

They are more efficient than air conditioners and generally transfer an amount of heat energy some three times the operational energy. Other sources depend on the particular locality of the city, e.g run-of-river hydro, tidal and or wave.

Large infrastructure high power sources such as hydro, geothermal and hot rock facilities are source localised and require high power grids for delivery. Their usefulness depends on their locality to major centres and to any adverse environmental effects. Local environmental impacts of dam construction followed by water management issues with hydro are well known and may not be consistent with the overall requirements of a bio-sensitive society. Nuclear fission and fusion both fit into the large infrastructure category and are considered further below.

Solar, both small thermal, photovoltaic and to a lesser extent wind may be sourced from roof tops for heat and power. Electricity generated can be interconnected through the local grid. Small wind turbines of a few kilowatts each are being touted as suitable for roof tops within present urban areas. However annual efficiency factors are not encouraging when compared to those obtainable from a wind farm of the same overall rated power. Also, as with roof-top and other surfaces suitable for pv solar, there will be a trade off between the need for high density housing to reduce the energy requirements for transport while maintaining the over all power needs of the population. It is likely therefore that roof-top systems will need to be supplemented with local wind and solar farms. The latter comprise large solar thermal plants of types consistent with the locality and/or photovoltaic systems depending on efficiencies and also on the local environment. Biological photosystems using various applications of photosynthesis under research at present, may also be a factor in future energy options. Siting of the city will also change the mix of viable renewable options and introduce others such as less solar, more wind, wave and tide, more biomass etc.

However solar, wind, wave and tidal systems cannot achieve their full potential to become major sources for domestic, school and office power without the ability to store energy and so smooth out their variability. The principal options at present are hydrogen with fuel cells, ammonia, various redox battery systems presently under development, for example zinc oxide, vanadium and vanadium bromide. The latter offer kW to MW electrical storage capability with application to transport as well as stand alone systems. Hydrogen can be produced directly from water by electrolysis and the fuel cell reverses the process with the usual loss due to efficiency and entropy production. Hydrogen in this case is a ‘carrier’ for solar power. The practical difficulties of storing hydrogen in a manner and volume that ensures its rapid recovery and in useful quantities are major handicaps to its present wide-spread use but are under such intense research and development that solutions may well be found in the near future. If solar and wind power with storage can cover residential, school and office needs then hydrogen production from methane may provide a source for some transport requirements, but may not be the best option for the megacity (see below).

Presently hydrogen is mainly produced in large quantities from mined natural gas (methane CH₄) with good yields due to the high number of hydrogen atoms per molecule. The alcohols, such as methanol and ethanol also provide a source and are being used in small fuel cells under development for powering devices such as music players and laptop computers. A steam reforming two-step process in methane produces hydrogen and finally carbon dioxide, and is otherwise "clean" provided the original methane has no impurities. All biological wastes from the megacity could be decomposed to produce methane that may then be used either for hydrogen production, or as a direct fuel source for co-generation of heat and power. The end product of course is CO_2, but the other alternative, namely aerobic decomposition of the waste, which may seem to be more friendly to the environment, produces the same amount of CO₂ per kilogram of waste. Both also produce fertiliser for use with food production so it is far more efficient from the energy standpoint to go anaerobic and fully use methane either as a direct fuel or for hydrogen production. This is a case of necessary production of a greenhouse gas. However methane itself is some twenty one times more potent than carbon dioxide as a direct greenhouse gas. Consequently it is far better to use it as an energy source and sequester the equivalent carbon dioxide by biomass planting.

An essential requirement for any society will be oil, even if not used for transport. Oil is essential for lubricants, as a feedstock for chemicals, plastics, and a wide variety of products in use every day. Without direct fossil supplies, oil can be produced from biomass, various wastes, and coal. Germany developed the Fischer-Tropsch process during the second world war and it is being used and further developed in South Africa. However the process for coal uses a finite fossil resource, produces a number of impurities already present in coal and of course, carbon dioxide. If the transport requirements for oil can be minimised then renewable sources may be sufficient to sustain society’s needs. A major difficulty will be the maintenance of a viable air transport system, at present heavily reliant on cheap oil. Hydrogen as an aircraft fuel may be possible well into the future but to become viable requires major advances in storage and technology beyond those required for land transport. Air transport will therefore become a major problem unless an alternative non-polluting fuel can be found. Even if sufficient oil from renewable sources can provide a basic service, the problems of carbon emissions will remain. Ocean transport will need to become highly efficient by vessels increasing in size. Diesel engines can be made more efficient and clean but to maintain sufficient supply from renewable resources remains a problem together with emissions. Small nuclear reactors could easily solve the ocean energy problem but the waste disposal then becomes an environmental problem not consistent with the criteria.

It is possible that local solar, wind, small geothermal and methane with co-generation will satisfy the megacity’s basic residential, school, health, commercial and cultural needs provided energy efficiency is paramount. However there is a question concerning the power requirements for a robust industrial and manufacturing sector, which may also include food production. At present a ‘base load’ or an unchanging quantity of power is provided by power generating technologies for all societies and this base is supplemented by a fluctuating peak as demand changes. A bio-sensitive society will certainly reduce its overall power load compared to today’s developed societies, and one can expect that the local renewable sources will cover all peak loads and substantially lower the base load requirements. However a certain base load would seem necessary to ensure the entire power needs are met. Intra- and inter-city transport requirements (see below) imply also that high capacity power sources for those systems will be required.

The large infrastructure high power sources become necessary to satisfy a base load, and with questions concerning new large hydro schemes, hot rock geothermal sources come into consideration. Being locality specific, one might argue that large industrial and manufacturing complexes may well coexist. This may be feasible if the power source is reasonably close to the megacity, if not transport issues would favour location of the industries close to the city and transport of the power via the grid. Nuclear power and ‘clean coal’ are considered answers to our present emission problems but both present dilemmas to the bio-sensitive society. Both are finite fossil resources and both have environmental problems. Coal can never be ‘clean’ even if carbon sequestration into underground ‘safe’ reservoirs becomes feasible. Coal contains a large number of metallic impurities and radioactive elements such as uranium and thorium. While the quantity of these impurities varies with the particular coal deposits, the process of turning that coal into useful heat or oil concentrates them into the ash and fly ash. The carbon dioxide and sulphur oxides can be removed and sequestered or used, but the remaining ash has much higher concentrations of impurities and needs disposal. To date most has been used as a filler for bricks, concrete and included in road fill material. Likewise while nuclear fission is in wide spread use and is a mature technology with recent high safety standards, it is a fossil source and waste storage remains a major problem at present. Future technology will broaden the fuel sources and may solve waste problems but it is unlikely that coal or nuclear fission will be considered options for the bio-sensitive society. Nuclear fusion does not have any of the environmental impacts of fission and it is presently at a stage where the international Tokomak experimental reactor (ITER) should be operational by 2017. It is designed to produce more power than it consumes, but to go from an experimental device to a commercially viable generator, will take many more years of development. It is therefore an option but one which is still too far into the future to predict what its final role might be.

In the megacity the ‘heat island’ effect will need addressing. The options appear to involve minimising roads and to assist with cooling, having residences interspersed with ‘breeze corridors’ of treed parks, recreation areas etc. and areas for intense food production. This in turn puts stress on the types of intracity transport. Advanced internet style communications including voice, image and script may assist in allowing many employment tasks to be home based, or within walk or cycling distances, and so minimise the necessity for "travel to work" except for very specific work areas involving hospitals, museums, research centres, etc where concentrated facilities are necessary for the efficient delivery of services. Privately owned vehicles are inefficient and power hungry whatever the energy source. It would seem therefore that private vehicle ownership would be unlikely and where transport is necessary, public electric light rail or similar vehicles interconnecting centres would be available at population centres. These may vary in capacity, be entirely automatically controlled and be either on call for specific journeys or immediately available for small groups over well-defined routes. They would need to draw no power while idle. While the necessity for transport between megacities would be minimised there would still be a need for the transfer of specific foods and manufactured items and to provide transport for vacations and family visits. An automated electric rail, highly controlled to ensure efficient operation, could again satisfy these. These transport issues again point to the need for a large infrastructure high power source.

Conclusions

The definition of a bio-sensitive society and the limitations that imposes on the criteria for its energy options restrict those to renewable sources of all types using as much distributive and co-generation as possible and supplemented by high power facilities from hot rock geothermal sources. Nuclear fusion may be a "far into the future" possible high power energy option. Efficiency in the use of energy in all sectors will be paramount to the success of the society as will comprehensive recycling. Energy for transport will prove a major issue and will be the driver determining the design of cities and their interconnection in all aspects. Ships and particularly aircraft present real problems in finding a non-polluting and safe energy source, which can satisfy the demands of modern travel. Renewable oil supplies may be insufficient while still presenting emission issue

References;

1. "What is our biggest problem?" Ockham’s Razor, Radio National Sunday 27 November 2005, and see http://socialwork.arts.unsw.edu.au/tsw/.

2. "Ecopolis Now" and "Master Plan" , Fred Pearce, New Scientist 17 June 2006.

[Further Reading list to be added ]

John Sandeman joined the Department of Physics, School of General Studies, ANU in 1966 and retired as head of the Department in 1993. His interests began in shock wave physics and various techniques of diagnostics. On retirement he was Chairman of the Australian Consortium for Interferometric Gravitational Wave Astronomy and a member of the Gravitational Wave international Committee. He has been associated with the National Youth Science Forum (NYSF) since its inception in 1983 and the Chairman of its Council since 1999. He was awarded the OAM in 2004 for services to education and the NYSF. His recent interests are in the science of global warming and the technologies for reducing greenhouse emissions.

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Comment:

A way to get investment in renewables

Posted by Kevin Cox at 2008-06-11 15:34

As John Sandeman points out there are solutions to the Energy needs of our modern society the question is how to mobilise our resources (make investments) to build a renewable energy future.

There is a remarkably simple way to achieve this and that is to put a surcharge on polluting energy (which we already have in excise and other taxes) and to direct the money collected to building the renewable infrastructure. The difficulty is in directing the resources. We cannot trust the government to do it as their record is abysmal, we cannot trust the energy companies to do it because they want to maximize their existing investments. The only ones who can do it are the people themselves. However, we need governments to put in place the framework for us to do it.

Here is one way that it can be done.

Give all the extra money collected from the sale of polluting energy (that is money over and above the money collected to produce it and to give a return on investment to the existing producers) to those in society who make the fewest demands on resources as Rewards money. However, require them to spend the Rewards they receive on renewable infrastructure or on ways to save energy.

The problem now becomes where are the ways to spend Rewards? These will arise if we say to suppliers - tell us what you want to do and you then ask people to invest in your products and services using their Rewards. The ideas must meet broad criteria such as they must either generate clean energy or save energy or research into ways of building a sustainable future. If suppliers are found trying to abuse the system by telling lies or not delivering then they cannot participate because buyers are prevented from using their Rewards to buy their goods and services.

If buyers knowingly participate in fraud then they too no longer receive any Rewards.

This approach will rapidly bring about the most economically efficient way of building a renewable energy future.

See writings on this at http://cscoxk.wordpress.com/2008/06/08/a-solution-to-the-tragedy-of-the-commons-chapter-1/

To see how to implement this approach see http://rewards.edentiti.com

Comment:

energy and population

Posted by Bryan Furnass at 2008-06-11 15:42

John
What an excellent overview of the biosensitive city's energy needs, particularly in industrialised societies. No mention was made about the growth of megacities in the developing world, including their needs for major infrastructures for public health, city farms, transport, etc. Cuba has provided a good example of adaptation following the collapse of the Soviet Union and its supply of oil, fertilisers, farm machinery, etc.They re-tooled their economy towards organic city farms (requiring minimal fossil-fuelled transport)and re-introduced human and animal power, as in pre-industrialised societies. Their authoritarian government may not be everyone's cup of tea, but Cuba enjoys one of the best profiles of health (low infant mortality, high life expectancy and universally available medical care) in the developing world, and is prominent for supplying medical aid for overseas disaster areas.
Why do governments fail to address the scientifically correct but politically incorrect basic equation: environmental impact = population x resource use? The exponential sixfold increase in human population since the industrial revolution has parallelled the forty-fold (I think) increase in fossil fuel consumption. Something has to give. Perhaps the Malthusian nightmare of population collapse will come sooner than we think!
On a lighter note on wind power for transport. A German container company has fitted one of their ships with a large sail, which has cut 20% off diesel requirements for the Atlantic crossing.A wine company in SW France has switched to exporting Bordeaux wine to Ireland by sailing ship, a journey which takes 5 days, compared to a few hours by plane. They claim that their main aim is "to slow things down" - an objective surely to be desired in other aspects of a biosensitive society, such as slow food, and could be applied to the working week, such as Kevin's 24/7. (As following the transmission of a nerve impulse, which requires a latent period to re-arrange the chemistry before re-firing).

2012-06-18T14:37:58+10:00 2012-06-18T14:37:58+10:00 roba Oceans http://www.natsoc.org.au/our-projects/biosensitivefutures/part-4-facts-and-principles/ecological-issues/oceans Ocean dynamics, overfishing

David Tranter

Contents
Ocean dynamics
Environmental impact
Overfishing
Ocean potential
Glossary

(a) Ocean Dynamics

Accustomed as we are to life on land, we tend to forget that it is the ocean, not the land, which occupies the greater part of the earth’s surface - the restless, mobile ocean - and the land is in its way! Exposed by day to the full force of the sun, the surface of the sea absorbs enough energy to set the winds in motion and the ocean follows suit.

Cool air is drawn from high latitudes to low to form the trade winds and as the seasons change they follow the sun across the equator. Combining with the eastward spin of the earth, the trades drive equatorial currents westward toward continental shores where poleward western boundary currents such as the Gulf Stream and East Australian Current are formed. Hugging the continental shelf, these currents distribute warmth to higher latitudes and spawn large warm and cold-core eddies which chase their tails for months at speeds of several knots until they are swallowed up by the surrounding sea.

Closer to the coast, nearshore currents pick up sand and deposit it on beaches and river mouths to form coastal lagoons, while tidal currents rush through narrow straits drawn by the pull of moon and sun. In ways like these, the global ocean discharges and recharges its batteries, interacting feverishly at times with the atmosphere to form cyclones and tornados that make light work of the feeble handiworks of man.

Ice ages - As cold eras alternated with warm during the ice ages, ocean and atmosphere reversed their respective roles as source and sink for carbon dioxide in response to such factors as: the advance and retreat of snow and ice across land and sea; the pace of deep-sea circulation; and the higher solubility of carbon dioxide in cold seawater.

During glacial periods carbon dioxide flows from land and atmosphere into the freezing ocean where it is now more soluble. As sea-ice forms it extrudes brine, leaving matrices within the ice that are colonised by siliceous algae and bacteria. In summer, when the sea-ice melts, sticky algal aggregates released into the water column sink quickly to the bottom, the habitat of a rich, recently-discovered sea-floor fauna.

Salt-enriched by the formation of (low-salinity) sea-ice, cold, saline waters at the sea-ice edge become so dense and heavy that they sink like a gigantic waterfall in slow motion carrying their load of dissolved carbon dioxide into the ocean deeps and across the ocean floor, ventilating the abyss. This "suction pump" draws carbon dioxide into the ocean through the air-sea interface, depleting the level in the global greenhouse and reinforcing the pace of ice-age advance.

Conversely, during inter-glacial periods, the deep-sea circulation weakens and, as carbon dioxide becomes less soluble in the warming ocean, it flows back into the atmosphere through the sea-air interface reinforcing the pace of global warming.

Global thermostat - Yet it is this same violent ocean that, over the ages, has combined with the atmosphere, the "placenta of the earth", to keep global temperatures at levels fit for life, providing animals with oxygen to breathe, water to drink and a great deal of their food.

Hidden beneath the surface of the sea are food chains based on microscopic algae with glassy, cellulose and calcareous shells, which draw nutrients and carbon dioxide from the surrounding water and energy from the sun to synthesize organic matter. So many calcareous shells have been produced since life began that a great deal of the ocean floor is now covered in calcareous ooze.

The destiny of this calcareous material is to be buried in the bowels of the earth and there transformed by heat and pressure into calcareous rock, or carbon dioxide which is eventually released into the atmosphere by volcanos. Thus begins the first phase of a long-term global thermostat cycle based on calcium carbonate.

Just as the bloodstream of mammals maintains their bodies at an even temperature, aerates their tissues and transmits information back and forth by way of hormones, so the ocean functions as an external milieu for its plant and animal inhabitants. Its pH and inorganic constituents are so much like blood that it was once thought the two were closely linked. As land plants rely on winds to disseminate their seed, so marine animals shed their eggs and larvae into the sea to be carried away by the currents to distant places.

Thermocline and nutrients - It is the fate of all open ocean animals and plants when they die to sink towards the bottom where their remains are decomposed. Consequently, bottom water is the main nutrient source for ocean productivity. However the same sunlight that phytoplankton in the upper layer requires to synthesize organic matter also has the effect of stratifying the water column.

The intervening thermocline inhibits nutrient influx from below, isolating sunlit algae from their nutrients; and because they are nutrient-impoverished their carbon dioxide uptake is limited. As a consequence, the most fertile areas of the ocean are where the thermocline is shallow, where deep waters upwell, or on the continental shelf. In high latitudes, the thermocline breaks down in winter, initiating a spring bloom which sustains the food chain for the greater part of the year.

Food chains - Feeding on phytoplankton is a wide diversity of small, planktonic grazers whose common characteristic is their ability to filter particulate food; and so the story goes, from one link in the food chain to the next, each grazer and each predator somewhat larger than the one it has consumed until the ultimate morsel is large enough to attract the leviathans of the sea. Those shellfish, crustaceans, molluscs, fish and whales that we harvest for food are the end-product of this cycle of organic production.

While all this eat-and-be-eaten activity takes place in sunlit surface waters, the main site of primary production, deeper-living animals feed on detrital sediment or migrate upward once a day to forage. Meanwhile, down in the abyss, other animals aggregate near the sea floor in places where hydrogen sulphide emanating from the bowels of the earth provides an alternative energy source to sustain organic production.

Human seafarers - People are drawn to the edges of the sea to search for food, ancient adventurers crossing the Mediterranean in rowing boats to find new lands to conquer. With the dawning of the Renaissance, a little bit of Western Europe jutting out into the Atlantic sent men out in sailing ships to find new lands, their successors colonising the New World with the help of "guns, germs and steel".

In the course of time, ports developed along the coast where trading ships could safely anchor. Today the greater part of the world’s population is concentrated there, both for trade and amenity, burning fossil fuels at an escalating rate, oblivious to the danger of rising sea level. Australia, the island continent, lies well away from the main shipping lanes and one can work at sea for months and never see another ship; by contrast, the Straits of Malacca, the North Sea and the Gulf of Maine are alive with ships; there are frequent traffic jams and their lights at night look like a city.

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(b) Environmental Impact

Ice melt - The Arctic ice-cap is melting much faster than expected. Should this melting extend to Greenland and the Antarctic mainland, the liberated melt-water would raise global sea levels so high that low-lying lands around the world would be inundated.

As people are driven from their native lands in search of refuge they tend to leave in small, unseaworthy boats and face a miserable death at sea. To date, the stream of refugees has not been very great, but the flow would surely escalate should the low-lying areas of heavily-populated nations like Bangladesh be swamped. If the continental ice-cap does retain its integrity, the level of the sea will still rise, due to temperature-induced expansion, but the rise is unlikely to exceed one metre.

Feedback effects - We tend to think in a linear kind of way, some more linearly than others. The ocean doesn’t work that way; its processes are highly interactive. It is common in the ocean and the atmosphere, its partner, for effects to influence their cause. Such feedbacks come in two different forms: negative (where the effect moderates the cause) and positive (where the effect reinforces the cause).

The problem with positive feedback is that it carries a sting in the tail: its destabilizing consequences are sometimes irreversible. The combustion of fossil fuels, for example, is gradually acidifying the sea and dissolving the shells of calcareous organisms, plant and animal alike, compromising the ocean’s capacity for long-term regulation of the earth’s temperature.

Another example is the sea-ice factor: Sea-ice reflects back to space a great deal of the heat it receives from the sun, reinforcing the freezing rate; conversely, when the sea-ice begins to melt, the dark-blue sea that it exposes absorbs the heat of the sun reinforcing the melting rate.

A third example is the reinforcing effect of the thermocline on global warming: as the thermocline becomes stronger under the influence of global warming, and its oceanic expanse becomes wider, phytoplankton capacity to take up carbon dioxide decreases and the surface layer of the ocean changes from a carbon dioxide sink to a carbon dioxide source; the consequence is reinforced global warming. It is therefore of some concern that few quantitative data on such feedbacks have been available to the Intergovernmental Panel on Climate Change to include in their models. Their Report (IPCC 2007) is consequently conservative; the real situation could be worse.

Ballast water - From time to time, an oil tanker comes to grief and spills its load into the sea, as in Torres Strait in 1970 when the Oceanic Grandeur skimmed a reef at low tide. The oil that is lost suffocates the fauna on the sea floor and coats seabirds with oil they can’t remove. But there are worse pollutants than oil. The seawater that tankers use for ballast contains larvae of exotic species which, when released nearshore in virgin habitats, can proliferate like weeds wiping out valuable local species. Tankers should be required to empty their ballast water out in the open ocean where their unwelcome cargos are less likely to survive.

Bottom trawling - Not so long ago it was said that we knew more about the far side of the moon than the deep-sea floor. Bottom trawling is much like sending a probe from an orbiting satellite through an opaque atmosphere to sample life on the surface of an unknown planet. For centuries, that has been the way that bottom fish have been caught. Inevitably the trawl takes everything in its path except for animals smaller than the mesh. The catch is then dumped on the deck and sorted into catch and by-catch, the latter unceremoniously returned to the sea with little chance of survival.

Bottom trawling scours the sea floor and damages the community of animals from which the catch was taken. It is therefore not surprising that continued bottom trawling has resulted in diminished catches. The first attempt to assess the extent of this damage was by CSIRO ecologist Keith Sainsbury, who persuaded the Australian Government to set aside a virgin area of the Northwest Shelf as a control by which to judge the effect of trawling on an adjacent fishing area. Underwater photography of both test and control demonstrated the impact of trawling for the first time, for which research he was awarded the Japan Prize, the most distinguished international award in ecology.

Long-line fishing - The long-lining technique for catching fish such as tuna, which forage in the water column rather than on the sea floor, was pioneered by the Japanese. More than 500 longline boats from more than 30 nations are at sea each year, chiefly in Alaskan waters and the Southern Ocean.

Fifty miles or more of line with several thousand baited hooks are fed out by each ship across the surface of the sea and hauled in again a few hours later. Some 5 million hooks are set each year.

Hungry sea birds like albatross, whose habit is to target any fish they see, cannot discriminate between live squid and squid on baited hooks, so they get impaled. Secured by their beak or throat they are unable to escape and are drowned. Thousands die in this way each year, including the large Wandering Albatross, which has a wing span of up to eleven feet. The consequent mortality is greater than most conservation-minded countries are prepared to accept, particularly since it can be avoided by weighting the longline so the baited hooks sink more rapidly out of reach of foraging sea birds.

Dynamite fishing - Those without the wherewithal to fish at sea, particularly in Southeast Asia, frequently use dynamite to take fish from coral reefs, where the pickings are more accessible. As with bottom trawling, the impact does not discriminate between target fish and bycatch, destroying both the inhabitants of the reef and the reef itself.

(c) Overfishing

Fishery collapse - It is not without reason that each generation of fisher folk believe fishing to be not as good as it once was. In the early part of the 20th century, the nations of Western Europe set up the International Council for the Exploration of the Sea (ICES) to monitor the catches and control the yield, treating each target fish in turn as an isolated entity and studying its population dynamics to identify a maximum sustainable yield. The most vulnerable fish of all are those that forage on the sea floor such as Atlantic Cod. Canadian stocks of cod collapsed after 20 years and, of the North Sea stocks estimated at about 50,000 tonnes, less than one third of the sustainable minimum still remains.

As more and more boats were built and their technology improved, each target fishery declined until it became more economic to abandon the overfished in favour of a virgin population. Right now, about one-third of the world’s commercial stocks have collapsed and the decline is accelerating. The practice of sampling the catch to study a target population is flawed at the outset, externalizing as it does the community from which the target catch is taken - a practice not unknown in economics.

Tuna fisheries - The Southern Bluefin Tuna is an Australian icon. A magnificent fish, it roams the Southern Ocean feeding on small fish and squid, migrating north to breed in an area south of Java where periodic upwellings generate food of smaller size to sustain their offspring. Drifting south with the El Nino-driven Leeuwin Current, the young are carried around Cape Leeuwin, getting bigger as they go, across the Great Australian Bight, up the southeast Australian coast a way, then out into the Tasman Sea, providing pole-fishing opportunities for coastal tuna boats operating out of such ports as Port Lincoln and Eden. While Australia harvests the juveniles, Japanese and Taiwanese long-liners patrol the Southern Ocean taking the adults. Despite continuous monitoring of fishing pressure, the population has declined from about 75,000 tonnes to about 15,000 tonnes over the past 45 years and there are real concerns that the fishery is endangered.

Whaling - By the time Australia was colonized, American whalers and sealers were already wandering the oceans of the world searching for animal oil. Early explorers across the Nullarbor were astounded to find large whaling fleets at anchor in what is now Albany. Before long, enterprising Australians were harvesting whales from long-boats in the Eden area.

Immediately after World War I, open-ocean whaling got into top gear in the Antarctic, taking one whale species after another, starting with the Blue Whale, the largest animal that the world has ever seen. As stocks declined, whalers moved to smaller species, taking each species to its economic limits, then moving on to even smaller species. Now their target is the Minke Whale, the smallest whale of all.

Ongoing British studies at the main Antarctic whaling base in South Georgia have revealed a surprising phenomenon: as whale stocks declined to the brink of extinction, those seals that feed on the same food source (Antarctic krill) began to multiply, demonstrating how closely the components of Antarctic ecosystems are interlinked.

As a result, the International Commission that was set up in Tasmania to manage Antarctic stocks began to consider the Antarctic ecosystem as a whole rather than by species. The limitations of population dynamics in fisheries management led ultimately to the alternative strategy of "adaptive ecosystem management" in which Australian scientists led by CSIRO played a major role.

Immediately after World War II, whaling bases were established at Northwest Cape and Tangalooma (South Queensland), to take humpback whales on their annual northward migration from the Antarctic; by then their populations were already in decline. Before long, countries like Australia began to ban further whaling. Soon there were signs of recovery, starting with the smaller, faster growing species. But some nations such as Japan and Norway have ignored the ban, continuing to take Minke Whales for scientific purposes. Meanwhile, whale-watching has begun to flourish throughout the world, boosting the tourist industry.

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(d) Ocean potential

Nowhere else are interactivity and feedback as keenly appreciated as in oceanography, meteorology and ecology. The term ecology was coined by the German planktologist Ernst Haeckel to describe studies of the household of nature. It took a meteorologist (Albert Wegener) to challenge the fundamental geological wisdom of the day that continents are fixed in position on the face of the earth; and it took oceanographers to explain the dynamics of inter-annual (El Nino) drought.

As the world’s resources, such as land, water, food and fossil fuel are stretched to their limits, a phase change is required in our understanding of Nature if we are to survive and prosper. The ocean is a storehouse of such information and a source of new opportunities.

El Nino - LaNina - It is the ocean, rather than atmosphere, that is the better predictor of long-term weather. Nowhere is this better illustrated than with the El Nino Southern Oscillation (ENSO) which drives the pan-Pacific drought cycle. When the equatorial thermocline in the Eastern Pacific is too deep for diving birds to reach their prey, they starve in their millions, at which time Australasia is in drought; conversely, when the prevailing trades pile warm equatorial waters up against Australia and the East Indies, the resultant heat engine lifts humid air on high and the rains returns to our part of the world. This (ENSO) cycle lasts from 3-7 years, its passage evident month by month across the equatorial Pacific in sea surface temperature and thermocline depth, early warning signals of the climate just ahead.

Gulf stream- The sciences of oceanography and meteorology are inter-twined, their weather satellites monitoring the sea surface, their anchored buoys monitoring the water column. Should the Arctic ice cap melt much more, the freshwater that would be released would dilute the sea so much that it would slow down the density-driven circulation that drives the Gulf Stream, the system that keeps the greater part of Western Europe much warmer than like latitudes elsewhere.

Sustainable energy - There are opportunities for reclaiming sustainable energy from the ocean which would otherwise dissipate in turbulence. The ocean is a gigantic powerhouse, converting heat from the sun into a variety of fluid motions which could readily be harnessed, particularly in Australia where the population is concentrated near the coast.

Immediately offshore from Sydney, where there is plenty of open space, batteries of interlinked wind and current farms could be built across the continental shelf to harvest energy from land-sea breezes and longshore currents, feeding power by high-voltage DC cable on the sea floor to the main state power grids. Similar opportunities exist in remote places such as Torres Strait and the Northwest Shelf where tidal currents race back and forth by night and day at speeds of up to seven knots.

In places like Christmas Island and Kiribati, where there are deep, cold waters close to shore, there is scope for ocean thermal energy conversion (OTEC). There is also energy in the waves that break incessantly upon exposed coastlines and energy in the winds which could be used to fill the computerised, rotatable sails of the next generation of ocean liners and tankers. Large maritime cities like New York, Rio, Tokyo and Sydney could recirculate nearby seawater to reduce their air-conditioning costs.

Mariculture - Nowadays, just as agriculture has replaced hunting and gathering, mariculture is overtaking wild fishing in importance. Here in Australia, the culture of pearls and prawns in warm waters currently leads the field followed, in cooler waters, by abalone, salmon, bluefin tuna and oysters.

Perhaps the time has come for calcareous ocean phytoplankton (coccolithophores) to be cultivated en masse at coal-fired power stations to fix their carbon dioxide emissions in a particulate form for disposal in the open ocean where it would sediment out on the deep-sea floor as in nature.

Many attempts have been made to extract pharmaceuticals from marine plants and animals, particularly on the Great Barrier Reef (Roche), but so far without a great deal of success.

Iron-seeding the oceans - Some scientists believe that the greater productivity of continental shelves is related to the influx of wind-blown iron from the land, iron being one of the three main prerequisites for primary production. Since large areas of the global ocean are deficient in iron, particularly subtropical areas, the proposal to seed unproductive expanses of the ocean from the air with particulate iron to enhance carbon dioxide uptake may have some merit, particularly if it leads to the production and sedimentation of calcareous organisms.

Coral reefs - Nowhere is the diversity of ocean life so well displayed in shallow waters for the world to see as on coral reefs, particularly in Indonesia, the Philippines and Australia. Because of its luxuriance and extent, the Great Barrier Reef is recognized as a World Heritage Area, attracting so many tourists from near and far that it has become a key part of the Queensland economy. Indeed, the east coast of Australia, with its coral reefs, glorious sandy beaches, coastal lagoons and rocky shores is without equal anywhere in the world.

Glossary

Detritus: Dead organic matter such as carcases and faeces

El Nino: An Equatorial Pacific climate phenomenon first noticed in Spanish Peru

ENSO: El Nino-Southern Oscillation; interannual alternation of Pacific Trade Winds and Equatorial Currents which controls the drought cycles in Australasia and Peru

Krill: Shrimp-like grazers about an inch in length; the main food of many kinds of whales, penguins, seals and Antarctic flying birds

Nutrients: Chemicals needed to sustain phytoplankton production

Mariculture: Controlled farming of marine plants and animals

Phytoplankton: Microscopic sized algal plankton

Plankton: Small creatures that drift with the currents

Primary production: Synthesis of organic matter by phytoplankton

Thermocline: Interface between the warm, nutrient-poor surface layer and the cooler, nutrient- rich layer underneath

Dr Sue Wareham

1. The raw material – uranium

2. Nuclear weapons testing

3. Nuclear weapons facilities and their environs

4. The biological effects of radiation exposure

5. The use of nuclear weapons

6. Climatic effects of nuclear weapons use

7. Nuclear waste

8. The role of human error, human malevolence and human wisdom

Notes:

Introduction

What is salinity and salinisation?

Impacts of salinity

Extent and Costs of Salinity in Australia

Management

Processes and types of erosion

Water erosion

Extent of erosion

Management

Further reading

Ozone layer

The production and destruction of ozone

The natural production of ozone

The natural destruction of ozone

Concern about ozone

UV penetration and its effects on living systems

UV effects on plants

UV effects on humans

UV and other species

UV and aquatic species

The Montreal protocol

The Australian response

What individuals can do

David Tranter

Summary

1. Introduction

2. Air-Sea Interaction

3. Evolution of “Air”

4. Sea-ice

Figure 1: Warming-cooling cycles (the “Ice Ages”) in the last 600,000 years. - Le Page 2007

5. Continental Ice

6. Ocean Amplifiers of Greenhouse Warming

Figure 2: Global Warming Amplifiers: Oceanic and Social Feedback Loops. - Tranter, 2009

7. Man-made Amplifiers of Greenhouse Warming

Figure 3: The Cumulative Global Warming Effect of Multiple Feedback Gains. - Paltridge, 2009

Figure 4: Exponential rise of Atmospheric CO2 since 1800 A.D. – Internet

Figure 5: The CO2 “anomaly” (deviation from the norm) over the past 8000 years. - Ruddiman 2005

8. Sea Level Rise

9. Climate Action

Sources

Contents

The evolution of the Earth’s atmosphere

What is the greenhouse effect?

Figure 1 The Greenhouse Effect

History of concern

Recent controversies

Facts

Figure 2

Climate predictions

Action

Australian emissions

Summary

The value of biodiversity

Explaining patterns of diversification

Current Concerns

Endangered Australia

Threats to biodiversity

Action – responses to the loss of biodiversity

Further Reading

Introduction

Energy criteria

Energy Options

Conclusions

References;

A way to get investment in renewables

energy and population

(a) Ocean Dynamics

(b) Environmental Impact

(c) Overfishing

(d) Ocean potential

Figure 5: The CO₂ “anomaly” (deviation from the norm) over the past 8000 years. - Ruddiman 2005