1. The human situation in the biosphere: an overview
- Energy and food chains
- The soil
- Nutrient cycles
- The health needs of ecosystems
- The health needs of individual organisms
- Biological conditions of life
- Social conditions
- Biological conditions of life
- Biological conditions of life
- Social conditions
- Bological conditions of life
- Social conditions
Australia and global ecology
Humans physically like us, and classified as Homo sapiens sapiens, have probably been in existence for at least 100,000 years.
Like all other animals, humans are a product, and a part, of the living world or biosphere, and are ultimately completely dependent on plants for their energy and nutrients. Plants, in turn, are dependent on rays from the sun for their energy, and on the soil, water and atmosphere for their nutrients. The effective functioning of the biosphere also requires the activities of decomposers, consisting of various microbes and fungi, which break down dead plant and animal tissues, so returning the nutrient elements to the soil, water and atmosphere.
The human species has a number of characteristics which are not shared with other animals (or at least which are not developed to the same extent in other species). These specifically human characteristics include the capacity to invent symbols and then use these for the purpose of communication - from individual to individual, group to group and generation to generation. The earliest application of this attribute was in the development of spoken languages. It was later applied in writing, musical notation, mathematics and computer technology.
Humans also have a highly developed potential for inventing new techniques, and then communicating this technological know-how to other humans (both by simple demonstration and through the use of spoken or written language).
These particular characteristics of our species led to the development of an abstract dimension of human situations which we call culture (Figure 1). Culture is a society�s accumulated knowledge, understanding, assumptions, beliefs, values and technological know-how. It is an extremely important determinant of what people actually do.
Fig. 1 Humans in the biosphere: evolutionary sequence
Fig.2 Culture-nature interplay
From the beginning, human culture was a new kind of force in the biosphere, leading eventually to big changes in the interrelationships both between humans and the other living organisms in their environment and between humans themselves. In fact, all human situations, past and present, are characterised by continual interplay between culture and nature2 (Figures 2 and 3).
The interplay between human culture and nature has intensified greatly in recent times. Cultural processes have resulted, for example, in a massive increase in the human population, and there are now about 1000 times as many people alive on this planet as there were when our forebears first started farming around 12000 years ago.
Cultural evolution eventually led to the industrial transition, which began about 8 generations ago3 and which has resulted a phenomenal increase in the rate of resource and energy use and of waste production by humankind.
Despite the spectacular advances in technology, humans are. of course, still, and for ever will be, entirely dependent on the underlying processes of nature for their well-being and survival.
|Note: The term 'biosphere' in this diagram refers to all aspects of the biosphere other than those incorporated under the general heading 'human society'. In reality, of course, humans and their artefacts are all part of the biosphere.|
Fig. 3 Conceptual model of culture-nature interplay
Life as we know it today is totally dependent on photosynthesis - the process which takes place in the leaves of green plants and algae converting light energy from the sun into chemical energy which is stored in the form of complex organic molecules in the plant tissues. These organic molecules provide the source of energy and substance for the processes of life in the plants themselves, in animals and in most microorganisms.
The key role in photosynthesis is played by the large magnesium-containing organic molecule, chlorophyll, which is responsible for the green colour of vegetation. In its dominant form, photosynthesis involves the uptake of carbon dioxide (CO2) and water (H2O) from the environment to form energy-containing organic molecules, and the release of free oxygen.
Photosynthesis first came into being in the oceans around 3500 million years ago in the single-celled blue-green algae. Ultimately it was to have far-reaching evolutionary consequences. For example, because the photosynthetic process caused the accumulation of oxygen (O2) in the atmosphere, it eventually led to the evolution of organisms which, unlike earlier forms, were able to tolerate this gas in their environment. Eventually cells evolved which not only tolerated oxygen, but which actually needed it for their metabolism and growth.
Also of great evolutionary significance was the fact that some of the oxygen released into the air became converted into ozone (O3), which then accumulated as a layer in the upper atmosphere, or stratosphere. This layer of ozone acted as a filter, absorbing much of the ultraviolet radiation from the sun. Had it not been for the consequent reduction in the intensity of UV radiation reaching the surface of the Earth, the eventual evolution of life forms on land would not have been possible.
For the first 90% of the history of life on Earth, all biological evolution was taking place in water. For about half this time the most complex organisms were single cells. However, by around 500 million years ago a fantastic array of much more complex organisms had come into existence, including sea weeds, sponges, jelly fish, corals, worms, molluscs, sea urchins, crustacea, jawless fishes (like modern lampreys), cartilaginous fishes (sharks and rays are the surviving representatives) and �true fishes� (the group to which the great majority of modern fishes belong).
It was about 400 million years ago that some forms of life began to colonise the land. Between that time and now the processes of evolution have produced a great diversity of different plants and animals - from the early mosses, horse-tails and amphibians, through to the later conifers, flowering plants and myriads different kinds of insects, spiders, reptiles, birds and mammals.
During the past several hundred million years many forms of life came into existence, flourished or a while, and then disappeared entirely. These included all the trilobites and ammonites in the oceans and the dinosaurs on land. In fact, the vast majority of animal species that existed in the past eventually became extinct without leaving descendents.
Energy and food chains
While the sun provides the energy that fuels the processes of life, it also plays other roles in the functioning of the biosphere. It is mainly responsible for the two great thermally-powered circulatory systems on the Earth�s surface - those of the atmosphere and the oceans.
Of the total solar radiation falling on the atmosphere about 35% is reflected before reaching the Earth�s surface, 17.5% is absorbed by the atmosphere itself and 47.5% reaches the surface. Of the solar radiation penetrating to the surface of the Earth about 30% is reflected as heat, 49% is involved in the evaporation and condensation of water and 21% drives the winds (Figure 4).
Fig. 4 Overall flows of solar energy
Estimates of the proportion of the solar energy reaching the Earth�s surface which is converted to chemical energy in plants range from 0.2 to 1.0%. Half to two-thirds of this photosynthesis takes place on land, and the rest in the upper part of the oceans.
More than half of the energy fixed in the leaves of plants through photosynthesis is used by the plants themselves in their respiratory processes (and reradiated to the environment in the form of heat). The rest is used by herbivorous animals that consume the plants, by carnivores that consume the herbivores (or that consume other carnivores), and by microbial and fungal decomposers.
At each stage in these food chains some of the chemical energy is coverted to heat, which then disperses into the environment (Figure 5).
Fig. 5 Food chain in Nature
The term �ecosystem� has been defined as a recognisable ecological system, comprising both living organisms and the non-living environment, defined over a particular area - for example, a forest, grassland or lake.
Thus, within the great global ecosystem, the biosphere, there are countless smaller ecosytems within ecosystems, ranging from islands, rainforests and chains of mountains, to farms, village ponds, backyards and aquariums.
All terrestial ecosystems are, of course, exposed to the atmosphere, with which they exchange carbon, oxygen, water and other substances.
In all ecosystems there is an input of energy (mainly in the form of solar radiation) and output of energy (mainly in the form of heat). This one-way flow of energy through the system is one of the most fundamental and essential characteristics of living systems in general (ie. ecosystems, populations of particular animals and plants and individual organisms).
Apart from the obvious influence of climate, the kind and amount of vegetation that grows in a natural ecosystem, and therefore many of its other characteristics, are mainly a reflection of the properties of that crucially important part of the system known as �soil�.
Soil can be defined as any part of the unconsolidated portion of the Earth�s crust which supports plant growth. It is made up of debris resulting from the weathering of rocks, and some organic matter. The inorganic matter can be regarded as a transient stage in the transportation of rock fragments and minerals from their source of origin to the oceans.
The organic matter in soil consists of decomposing plant and animal matter, as well as microorganisms (some involved in the decomposition process, others playing other vital roles in the life of the ecosystem) and various animals, including nematodes, millipedes, mites, insects, earthworms and burrowing mammals, amphibia and reptiles. The living organisms in the soil play an essential role in the nutrient cycles on which all terrestial life depends. Although the organic component of soil usually represents less than 0.1% of the total soil mass, it may still amount to many tonnes per hectare.
Some components of the decaying organic matter, like waxes and lignins, are relatively resistant to decomposition, and together they form a colloidal substance called humus. Humus improves the structure of soil and has an important positive influence on its capacity to support plant life.
Topsoil is the uppermost layer of soil which contains most of the living organisms, the humus and most of the roots of plants.
The characteristics of soil differ a great deal from one region to another. For example, where there is a relatively high and reliable rainfall, the topsoil is likely to be much deeper than in regions where precipitation is low or sporadic. In many parts of North America and Europe the topsoil is several metres deep, whereas in much of Australia it is no more than few centimetres.
The processes of life involve and depend not only on the supply of solar energy through the system, but also on the continual cycling of inorganic chemical elements, or nutrients, through the system. These nutrients, which are required for the growth and functioning of organisms, are taken up from the environment (mainly by plants) and incorporated into living tissue. Eventually they are returned to the environment where they are then available again for the building up of new plant tissue. This applies to all the numerous elements required for the processes of life. In quantitative terms, the cycles of carbon and oxygen (Figure 6), nitrogen, phosphorus and sulphur are the most important.
Fig. 6 Carbon and oxygen cycles
Some of the nutrient cycles are quite complicated and involve the essential participation of different kinds of microorganisms in key stages in the process.
The health of ecosytems and of the organisms within them requires that these nutrient cycles remain intact, ensuring a continual supply of nutrients for new growth. Consequently any development that interferes with them also interferes with the processes of life.
The health needs of ecosystems
A healthy ecosystem can be defined as one which is in a state of ecological balance. That is, it is in a state such that the rate of plant growth, or bioproduction, is more or less constant from year to year. An unhealthy ecosystem is one in which annual bioproduction is progessively declining.
It is essential for human well-being that the ecosystems on which we depend for our food remain healthy. This applies to local ecosystems providing food for nearby populations and it applies to the total global ecosystem, the biosphere.
We will consider below the ways by which the activities of human populations have affected, or are affecting, the health of ecosystems, locally and globally. In anticipation of this discussion, Table 1 summarises the basic health needs of the ecosystems of the biosphere - that is, the conditions that must be satisfied for present levels of bioproduction to be maintained or improved upon.
Table 1 Basic health needs of terrestial ecosystems
- A rate of soil loss no greater than the rate of soil formation
- The absence of polluting gases or particles in the atmosphere that can interfere with living processes or significantly modify the climate
- The maintenance of an intact ozone layer in the stratosphere protecting the Earth�s surface from ultraviolet radiation from the Sun
- The absence, in the oceans, lakes, rivers and soil of concentrations of chemical compounds likely to be harmful to living organisms
- The absence of levels of ionizing or electromagnetic radiation that can interfere with the normal processes of life and photosynthesis
- The maintenance of biodiversity
The health needs of individual organisms
As a result of the processes of evolution, animal species become well suited to the conditions prevailing in their natural habitat - that is, the habitat in which they have evolved. Consequently, if an animal is exposed to conditions which differ significantly from those of its natural habitat, the likelihood is that it will be less well suited to the new conditions, and so will show signs of maladjustment or ill-health.
This principle applies to all form of animal life, including humankind. Of course, sometimes animals experience ill-health in their natural environment. But most of the time, most members of an animal population living in the natural habitat of the species are in a state of good health.
Consequently, if we wish to identify the health needs of any particular kind of animal, the first thing to do is to study the conditions prevailing in its natural habitat, because we can be sure that these conditions are capable of providing all the essential prerequisites for good health. This principle can usefully be applied to the human species, and Table 2 presents a list of universal health needs of humans based on this approach.
Table 2 Conditions favouring health in Homo sapiens
- Clean water (free of contamination with harmful chemicals or pathogenic micro-organisms)
- Clean air (not contaminated with hydrocarbons, oxides of sulphur and nitrogen, lead etc)
- A natural diet (that is: a diet that contains the full range of nutritional requirements of the human species, such as would be provided by a diet consisting of a broad range of foods of plant origin and a small amount of cooked lean meat; a food calorie intake neither much less than, nor in excess of, metabolic requirements; a diet which is balanced, in the sense that it does not contain an excess of any particular chemical constituent or food source; foodstufs with a physical consistency of natural foods and containing fibre; foods devoid of potentially noxious biological or chemical contaminants)
- Absence of harmful levels of ionising or electromagnetic radiation (eg. alpha, beta, gamma, ultraviolet and X rays)
- Minimal contact with parasitic or pathogenic microbes or metazoa
- Dwellings that provide adequate protection from extremes of climate
- An emotional support network, providing a framework for care-giving and care-receiving behaviour, and for exchange of information on matters of mutual interest and concern
- Opportunities for cooperative small-group interaction
- A pattern of physical exercise which involves regular periods of moderately vigorous and varied muscular activity, but also periods of rest
- Opportunities and incentives for creative behaviour
- Opportunities and incentives for learning and practising manual skills
- Moderate levels of sensory stimulation, and an environment which has interest value and in which changes of interest to the individual are taking place
- Opportunities for spontaneity in behaviour
- Variety in daily experience
- Satisfactory outlets for common behavioural tendencies
- Short goal-achievement cycles and aspirations of a kind likely to be fulfilled
- An environment and lifestyle conducive to: a sense of personal involvement or purpose, of belonging, of responsibilty, of challenge, of self esteem; of comradeship and love
- An environment and lifestyle which do not promote: a sense of alienation, of anomie, of being deprived, of boredom, of loneliness, of chronic frustration
Note: with respect to many of the above postulated health-promoting aspects of life conditions, including some intangible aspects, the principle of optimum range is applicable. That is to say, either too little or too much of a given condition may be detrimental to health.
Some time between 15 and 8 million years ago an evolutionary event took place that was eventually to prove to be of immense significance for the biosphere as a whole. Somewhere in Africa or Asia a group of primates came into existence that preferred to live in open savannah country rather than up in the trees of forests. Among these animals were the ancestors of modern humankind.
Footprints left in volcanic ash in eastern Africa around 5 million years ago and some fossilised leg bones tell us that there were, by that time, primates walking around in an upright position, in much the same way as modern humans.
The earliest known remains of anatomically modern humans are dated at about 90,000 years ago and were found in Africa. They are classified, like us, as Homo sapiens sapiens (Figure 7).
|Note: The great increase in energy use in the last 150 years has been in part due to the growth in the human population (accounting for one tenth of the increase). The rest of the increase has been due to new technologies using extrasomatic energy as a source of power (mainly in the form of fossil fuels). The increase in energy use is approximately parallel to the increase in carbon dioxide production.|
Fig. 7 Human history
By 40,000 years ago, between the first and second phases of the Fourth or Würm glaciation, modern humans had made their appearance in Europe, where they replaced another form of humanity known as the Neanderthals, or Homo sapiens neanderthalensis. By the time that modern humans reached Europe they were already well established in Australia, where they had been living for at least 10,000 years.
Looking back through human history we can recognise four distinct ecological phases, which differ significantly from each other in regard both to the interrelationships between human societies and their surrounding ecosystems, and to the prevailing conditions of life of people.
The four ecological phases of human history are referred to as:
Phase 1 - the hunter-gatherer phase
Phase 2 - the early farming phase
Phase 3 - the early urban phase
Phase 4 - the modern high-energy phase
Although there is much variability within each of these phases, their main ecological characterisics are sufficiently distinct, and the differences betwen them sufficiently important, to make the four-phase concept both valid and useful. Societies representative of all four phases still exist in today�s world, although none are untouched by the impacts of the fourth, high-energy phase.
The basic characteristics of the four phases are as follows.
Phase 1 was by far the longest of the four phases, extending back at least several hundred thousand years (precisely how long depends on at what stage we choose to stop regarding our ancestors as human).
Biological conditions of life
The conditions of life during ecological Phase 1 were those which are �natural� to humans, in the sense that they were the conditions prevailing in the habitat in which the species evolved. Through the processes of evolution Homo sapiens sapiens had developed biological characteristics which rendered individuals and populations well suited to these conditions.
Since that time too few generations have been exposed to the new conditions of civilisation to bring about significant changes in the inherited biological characteristics of humankind. Basically, humans born today in modern Western society have the same innate, genetically-determined needs, sensitivities and behavioural characteristics as their hunter-gatherer ancestors of, say, 15,000 years ago.
A notable characteristic of ecological Phase 1 is the fact that all the members of any given society experienced very similar conditions of life. In this respect hunter-gatherer societies differ markedly from those of ecological Phases 3 and 4. (Phase 2 societies are variable in this respect).
Like other animals living under natural conditions, most of the time most of the people in hunter-gatherer societies are likely to have been in a state of good health. The main causes of death were probably physical injury and infection of wounds leading to septicaemia. In some regions large carnivorous predators may have made a significant contribution.
Again like other species in their natural habitats, hunter-gatherers would usually have been well-nourished. Their diet typically consisted of a broad range of different plant foods (nuts, roots, berries and other fruits and certain leaves) as well as a relatively small amount of cooked lean meat. The diet of infants in the natural habitat consisted of human milk.
Because of the built-in hazards of the hunter-gatherer lifestyle and the lack of medical facilities, life expectancy was considerably lower than in the modern high-energy societies, although some people reached old age. Severe illnesses are likely to have been short, leading either to early recovery or to early death. However, the death rates would not have been as high, for example, as in the cities of the preindustrial era. In general, birth rates were more or less balanced with death rates, although over tens of thousands of years the population certainly increased significantly, as humans spread to occupy new areas of the world. On average, most couples probably had around 4 children, two of whom would have survived to reproductive age.
People in Phase 1 societies lived in bands which were usually nomadic. The size of the bands varied from time to time and place to place according to conditions, but probably averaged between 20 and 30 individuals. Sometimes these bands would get together with other bands for various kinds of celebrations to form larger groups, or �clans�, made up, perhaps, of between 120 and 180 people.
Organised violence, or warfare, between human groups was not a feature of hunter-gatherer society, although no doubt hostilities sometimes erupted.
Hunter-gatherers usually spent, on average, 2 to 3 hours a day seeking food. Hunting large animals was almost exclusively a male responsibility.
Although there was a certain division of labour depending on gender, age and individual propensitites and skills, permanent hierarchies were not a feature of most hunter-gatherer societies. There were no permanent, or hereditary chiefs.
Except for one notable factor, humans in the hunter-gatherer phase fitted into their ecosystems in much the same way as any other large omnivorous species, receiving their energy from plants and animals, and contributing energy to predators, scavengers and decomposers.
The notable exception to this generalisation arose from the deliberate use of fire by human groups as a regular aspect of their lifestyle and economy. In taking this step, people were utilising energy in a new way. Apart from the somatic energy which came from their food and which was used in their bodies, they were now also using energy outside their bodies - that is, extrasomatic energy. The use of fire involved the rapid conversion of the chemical energy in wood, initially trapped from sunlight through photosynthesis, into heat.
The regular use of fire in ecological Phase 1 probably increased the total flow of energy (somatic and extrasomatic) about twofold. That is, the average total energy use by adult humans would have been about 2 Human Energy Equivalents (HEE) per day.5
The major ecological effects of the use of fire in hunter-gatherer society were restricted to the destructive effects of fire itself. The chemical products of the combustion of wood (mainly carbon dioxide) were easily absorbed into the system as a whole without causing any ecological disturbance.
Another ecologically significant feature of the human situation in ecological Phase 1 was the fact that the human species spread into all five habitable continents of the world, and into regions characterised by a wide variety of very different climatic conditions. These included dense tropical forests, semi-tropical savannahs, deserts, temperate forests and grasslands, and the ice-covered plateaus of the Arctic.
The early farming phase, which began around 12000 years (480 generations) ago, involved the deliberate and concious manipulation of the processes of nature for the purpose of providing a constant and reliable supply of food. Its most essential features were the domestication both of plant and animal food sources and of humans themselves.
Fig. 8 Food chain and technometabolism 20,000 years ago
Biological conditions of life
The daily conditions of life of the people of the early farming phase were clearly different in some ways from those typical of hunter-gatherers. Human groups became less nomadic, although the length of time that they stayed in one place depended to some extent on the kind of farming they practiced.
The new relatively sedentary life style had an important impact on the interrelationships between human populations and potentially disease-producing microbes and parasites. In some areas malaria and schistosomiasis became important causes of ill-health and death. The greater vulnerability to such diseases counteracted, to some extent, the protection the new conditions afforded against the hazards inherent in the hunter-gatherer lifestyle.
The diets of people in Phase 2 societies varied from place to place and from time to time. The main difference from the diet of humans living in the natural habitat was a tendency toward less variety in foodstuffs.
There were also important changes in the kind of human activities associated with the acquisition of food, including a trend toward more monotonous tasks, harder physical labour and less time for non-subsistence activities.
However, despite such differences, the conditions of life in the early farming phase were more like those of hunter-gatherers than they were like the conditions experienced by people living in the early urban and modern high-energy societies.
The following comments on the ecological relationships between human society and surrounding ecosystems apply to both the early farming phase and the early urban phase.
As domestication spread and farming techniques advanced, the total impact of human populations on ecosytems progressively increased. Vast areas of forest in the northern hemisphere disappeared as a result of human activities - to be replaced in some areas by productive farmland, in others areas by different forms of less luxuriant vegetation, and in others by eroded landscapes.
Another change, resulting from increasing human travel and the use of boats, was the transportation of numerous species of plants and animals from their natural habitats to different parts of the world.
Among the important ecological consequences of farming was the introduction of monocultures of various food crops, such as rice, rye, wheat, and potatoes, on which some human populations became almost entirely dependent. Consequently crop failure, from whatever cause, was a very serious matter (eg. the Irish Potato Famine). Moreover, monocultures are especially susceptible to diseases and attack by insect pests.
Fire was still used as the main source of source of extrasomatic energy in the early farming and early urban phases. It came to play an essential role in the manufacture of earthenware pots and of tools, weapons and ornaments made of metal. This additional use of fire may have increased the total use of energy by human populations to about 3 HEE per person.
With the invention of such devices as water-mills, windmills, and sailing ships, extrasomatic energy came also to be used for performing various kinds of work. However, compared with later developments, the ecological impact of these uses of extrasomatic energy was slight. It was restricted mainly to the part that ships played in the migratory movements of humankind, in the geographical redistribution of plant and animal species and in the spread of technologies.
Around 5500 years (220 generations) ago, the first cities of Mesopotamia came into existence. One of the outstanding social and ecological characteristics of these and other cities was the fact that most of the members of their populations did not gather or produce their own food. They were supported nutritionally by food surpluses produced by nearby farmers who worked, and usually lived, beyond the city walls.
Biological conditions of life
Although there was much variation in the political and economic structure of cities in different places and at different times, the human populations of all these urban settlements shared, right up until the time of the industrial transition, a distinct set of biological characteristics which set them apart from earlier or later societies.
The most obvious of the changes associated with urbanization was the great increase in the numbers of people living together in one place. This increase in population density had an important effect on the interrelationships between humans and potentially parasitic or pathogenic organisms, so that pestilence became one of the striking characteristics of Phase 3 societies. Typhus, typhoid, the plague, smallpox, infantile diarrhoea and many other infectious diseases were constant cause of fear and alarm, and were among the main causes of death in early urban populations.
Another characteristic of urban populations was their tendency to rely on a single staple food, typically a cereal grain such as rice, maize or wheat, resulting in a narrowing of the range of foodstuffs consumed by city dwellers. Consequently specific deficiency diseases, such as rickets, scurvy, beri beri and pellagra were common in different parts of the world in the early urban phase.
Another nutritional characteristic was the recurring threat of famine. The reliance of urban populations on single monocultures meant that when unusual weather conditions or infestation with pests resulted in the failure of a crop, widespread starvation was virtually inevitable. Unlike the situation in hunter-gather societies, populations did not have a wide range of alternative sources of food to turn to when one failed.
The formation of the early cities led to a series of important changes in social conditions which became firmly embedded in culture and many of which are today regarded as �normal�.
From the social point of view, one of the most significant of these changes associated with the early cities was the introduction of occupational specialisation.
Some degree of specialisation had existed in Phase 2, and even Phase 1 societies; but apart from the gender-based division of labour associated with the care of infants and with hunting, most people performed a wide variety of tasks in the community. It was in the early urban phase that specialisation really came into its own, and it has remained a hallmark of civilisation to the present day.
Part of the biological significance of this development lies in the fact that, for the first time in human history, different groups of people within a single society were experiencing quite different conditions of life. Consequently, they also experienced different patterns of health and disease and different levels of well-being.
Occupational specialisation led in turn to strong reinforcement of the otherwise rather weak tendency of human societies to form hierarchies. Instead of being relatively spontaneous, transient and dependent on the nature of the task at hand, the hierarchical structure of society became more rigid, more extreme and more permanent. It frequently came to be determined by heredity or the distribution of military power, rather than by common consent or perceived natural ability. This development further contributed to the variability in the life experience of people in different sub-populations within human settlements.
Urbanization was also associated with entirely new concepts of ownership. In hunter-gatherer society individuals usually �owned� only those possessions that they could easily carry when they moved from one camp site to another, most of which they had found or made themselves. Such possessions were also readily given away or exchanged. In the early cities individual and family ownership became important, and in many cities the concept of ownership was eventually extended so that some people were regarded as the property of others.
Very early on in the history of cities wide discrepancies came about in the material wealth of different sections of the population. This situation has persisted into Phase 4 society.
Associated with these developments, there was a significant change in the in-group out-group experience of individuals. In hunter-gatherer times, most people belonged to only one group - the small nomadic band to which they belonged. Except for populations of other species of animals in the environment, and perhaps in some cases perceived spirits or gods, there were few out-groups in the daily life experience of the average individual. The number of neighbouring groups of humans was small and encounters with them were not frequent. With urbanisation the situation changed dramatically. While animal out-groups largely disappeared from daily experience, they were replaced by human out-groups. The common tendency of humans to act with suspicion towards out-groups became an important influence of social behaviour in cities. Often this suspicion developed into overt hostility. Moreover, urban society offered individuals the opportunity for membership of more than one, and often several in-groups, sometimes with differing sets of values and expectations.
It was with urbanisation that warfare became institutionalised and accepted as a normal aspect of human affairs. By the middle of the 3rd millennium BC soldiery had become a profession and the city states in south-western Asia had their standing armies. Deliberately organised lethal combat became commonplace, and indeed was apparently regarded as a good thing (so long as it was in the name of one�s own god or gods) and warriors came to be regarded as heroes. The pattern was thus set for the rest of the early urban period, and aspects of it persist to the present day.
The early urban and the early farming phases of human history shared two important ecological characteristics which are not features of modern society. First, the rate of utilisation of extrasomatic energy (mainly in the use of fire) and of carbon dioxide production increased at about the same rate as did the human population. Second, the activities of humankind did not interfere significantly with the natural nutrient cycles, such as those of carbon, nitrogen and phosphorus.
The transition to the fourth, high-energy phase of human existence began in parts of Europe about 200 years (8 generations) ago, and it was well underway in western Europe and North America towards the end of the last century.
The high-energy phase has been associated with spectacular technological developments, a massive growth of the human population and far-reaching changes in the ecosystems of the biosphere.
Only about 1/4 of the world�s population lives in established high-energy societies. However, the technologies, economic arrangements and value systems of these societies have had profound and wide-ranging impacts on all the rest of humanity, and they are largely responsible for the major causes of ecological and humanitarian concern in the modern world.
Fig. 9 Food chain and technometabolism - today
Biological conditions of life
A characteristic of the high-energy phase of great ecological and human significance has been the control of many serious contagious diseases through improved understanding of their causes. These diseases, which became so prevalent in the early urban phase, are no longer important causes of death in the developed countries, and they are becoming decreasingly so in the Third World. This change has been associated with improved public health programs, improved nutrition and the development and widespread use of artificial immunisation and antibiotics.
Another characteristic of modern urban societies is the large number of viruses that are circulating in the human population causing, in the main, relatively mild illnesses, such as colds, influenza and gastro-intestinal disturbances. A recent development has been the appearance of the much more serious virus disease known as AIDS.
Improved understanding of human nutritional needs has resulted in the virtual disappearance in the high-energy societies of the deficiency diseases that were so common in the early urban phase. However, many of them are still apparent in populations in the developing world. The main diet-related disorders in the high-energy societies are associated with the over-consumption of food.
The chief causes of death in the high-energy societies are cancer and cardiovascular disease, usually occurring quite late in life.
These changes in patterns of health and disease have been associated with an increase in life expectancy at birth, which has now reached over 75 years in many developed countries. However, it is slightly lower in the USA, which has the highest per capita material standard of living in the world, than it is, for example, in Spain or Australia. In India and Ethiopia it is about 45 years.
Big differences also exist in the incidence of illness and in death rates in different socio-economic groups within both developed and developing countries.
In most of the developed countries the effect of death control on population growth has now been largely offset by birth control. This is not the case in many developing regions where birth rates are far in excess of death rates, and further massive population growth is inevitable.
The total human population has increased ten fold since 1650, and has doubled in the past 30 years.
The average material standard of living in the high-energy societies, in terms of levels and rates of use of material resources and extrasomatic energy, is higher by far than at any previous time in human history. For example, in the USA iron is being used at a rate about 3kg per person per day, and extrasomatic energy at rate of about 100 HEE per day. This is about 100 times the rate in Nepal, 20 to 30 times that in Shakespearian Britain and about 5 times that in Spain in 1985. There are, however, great disparities in the per capita rate of consumption of resources and energy between different socio-economic groups within the high-energy societies.
A outstanding feature of the high-energy societies, and one of great ecological and biosocial significance, is the existence of corporations. These are groups of humans who act together as a body or unit and who are organised in such a way that they collectively contribute to the attainment of a particular set of goals. These goals and the values which they reflect are not necessarily shared by the majority of individuals of which the corporations are made up.
Corporations, especially those of a commercial nature, have become an extremely powerful influence on the patterns of resource and energy use and on human behaviour in the modern world. A disturbing aspect of corporations is the fact that, depending on their origins and perceived goals, they may be completely lacking in compassion, aesthetic sensibilty or concern about the natural environment and about the well-being of future generations of humankind.
Fig. 10 Per capita extrasomatic energy use
The massive growth of the total human population resulting from the control of contagious diseases without concomitant control of birth rates is exerting severe pressures on ecosystems in many parts of the world, associated especially with the production of food, fibre and timber for human use. These pressures are resulting in serious land degradation and a consequent fall in bioproductivity.
Of even greater significance ecologically has been the explosive growth in the rate of use of extrasomatic energy to drive machines for performing various kinds of physical work. The main source of this energy has been the combustion of fossil fuels (coal, petroleum and natural gas). This development has been associated with a massive increase in the intensity of the technometabolism of human society (inputs of resources and energy and outputs of technological waste products), imposing heavy new pressures on the ecosystems of the biosphere - locally, regionally and globally. Especially important in this regard are the by-products of the combustion of fossil fuels, including particularly carbon dioxide and the oxides of sulphur and nitrogen (Figure 9).
The total amount of carbon dioxide released into the atmosphere by the human species each day is now about 12000 times what it was at the time that farming was introduced. 75% of this increase has occurred in the last 50 years, and 50% in the last 25 years. If present trends are allowed to continue, the amount will double again in the next 30 years.
Ninety per cent of the 27,000 million tonnes of carbon dioxide now produced by human society each year comes from the combustion of fossil fuels. Most of it is produced by the developed or high-energy societies (which represent about 1/4 of the world�s population). For example, the amount released into the atmosphere per person is about 100 times greater in North America than in Nepal and Kenya.
The Intergovernmental Panel on Climate Change predicts that the continuing release of carbon dioxide and other greenhouse gases as a result of human activities on this scale will lead to progressive changes in the global climate, involving especially a significant warming effect. There is uncertainty about the extent and precise nature of these climate changes, and therefore about the ultimate consequences for life on Earth and for humankind.
Industrial activities in the high-energy countries also result in the release into the environment of other chemical compounds, many of them in enormous quantities and many of them interfering in one way or another with the processes of life.
The chlorofluorocarbons (CFCs), for instance, are now causing the erosion of the stratosphere�s ozone layer, which has been protecting the Earth�s terrestial life forms from the ultra-violet rays of the sun for hundreds of millions of years. Other chemical pollutants are causing progressive ecological changes in the oceans.
Mention must also be made of the massive increase in the destructive power of weapons for use in warfare. Despite recent encouraging steps aimed at reducing the arsenal of nuclear weapons, the stockpile in existence is still more than sufficient to destroy the biosphere as a system capable of supporting humanity.
No one knows precisely how urgent the problem is. Late in 1992, a group of 1575 scientists (including 101 Nobel Laureates), representing the Union of Concerned Scientists, issued a statement entitled World scientists� warning to humanity. To quote from the press release that accompanied the publication of this document:
�The appeal focuses on the environmental and resource damage caused by overconsumption in the industrialized countries - the world�s largest polluters - and the pressures on the environment caused by poverty and spiralling populations in the developing world. The scientists emphasize the urgency of the problem. As they note in the appeal, �No more than one or a few decades remain before the chance to avert the threats that we now confront will be lost and the prospects for humanity immeasurably diminished�.�
As in all reform movements, these people are countered by others who call them alarmists, prophets of doom, Cassandras and Jeremiahs (possibly forgetting that both Cassandra and Jeremiah turned out to be right).
There are, of course, uncertainties. The scientists sounding the warnings may be mistaken. They may be mistaken in either direction. Ozone is disappearing from the stratosphere faster than was predicted a few years ago.
Four things, however, are certain:
1. There are limits to the absorptive capacity6, resilience and adaptability of living systems. This principle applies as much to the biosphere as a whole as it does to local ecosystems and individual living organisms.
2. The present pattern of resource and energy use and of waste production in high-energy societies is not sustainable ecologically. If it is not brought under control through deliberate societal action it will come to an end either as the result of exhaustion of resources or, more likely and more seriously, as the consequence of irreversible changes in the biosphere caused by the waste products of technological processes.
3. Significant changes in the biosphere due to human activities have recently become evident at regional and global levels. These include the depletion of the ozone layer, suggestive signs of the predicted greenhouse warming effect, the effects of acid rain in Europe and North America, extensive desertification in arid regions and widespread changes in the oceans.
4. Warnings that we are fast approaching the limits of tolerance of the biosphere as a system capable of supporting humankind are being sounded by an increasing number of people who are familiar with the relevant ecological facts and principles.
The uncertainties include:
1. How much longer the biosphere, as a system capable of supporting humankind, will be able to survive the increasing ecological load that is being imposed on it by modern human society. At one extreme there are those who believe that it is already too late to attempt evasive action, and that the human species will not last more than 50 to 150 years. Others are more optimistic and take the view that a rapid adaptive response to the ecological predicament, involving drastic reductions in fossil fuel use and effective control of CFCs and other harmful chemicals, could save the situation. And there are a few who are not convinced that a serious problem exists.
2. Which specific ecological change (or changes) represents (or represent) the greatest threat to the system. At present the effect of CFCs on UV radiation and the impact on climate of carbon dioxide and other greenhouse gases are the main contenders.
Broadly speaking, three possibilities exist for the future of humanity.
First, the biosphere may lose its capacity to support humans, bringing about the early extinction of our species.
Second, there might occur a major ecological catastrophe, or series of catatrophes, leaving a few pockets of surviving humans to eke out a living here or there in the biosphere.
The third possibility is that the dominant culture of the modern high-energy societies undergoes a rapid transformation, involving wide appreciation of the ecological impossibility of maintaining �business as usual� indefinitely. If this happens in time, a new ecological Phase 5 society might emerge, - a truly biosensitive society that satisfies the biological needs both of all sections of the human population and of the ecosystems of the biosphere on which thay depend.
Historically the ecology of humans in Australia has differed from that in other parts of the world in that a pure hunter-gatherer situation persisted here until only about two hundred years ago. Since then the economy has been transformed to that of a typical ecological Phase 4 society. These two centuries have seen major changes in the patterns of health and disease of humans living in Australia. Before Europeans came, the causes of ill health and death were those typical of hunter-gatherer populations - that is, mainly injuries and infected wounds.
Between the time of arrival of the first Europeans and the present there was a period when the health and disease patterns of the human population were more like those typical of early urban societies, in that the main cause of death was contagious disease, associated sometimes with malnutrition. At present, cardiovascular disease and cancer account for nearly three quarters of deaths, and mild virus infections are one of the main causes of sickness.
There are now around 20 times as many people living in Australia as there were 200 years ago. At present life expectancy at birth for the Australian population as a whole is higher than at any time in the past, at about 76 years. However, it is considerably lower than this in some socio-economic groups.
Before the arrival of Europeans the main ecological impact of the human species was probably that resulting from the use of fire, which is believed to have had some significant effects on vegetation and animal communities.
The impacts of human activities on regional ecosystems during the two centuries of European occupation have been immensely greater. Over 3000 species of plant are now considered threatened, with almost 100 of these presumed extinct. Close to 200 animal species are judged as rare or threatened, with 17 species, mostly mammals, presumed extinct. At the broader level of ecosystems, widespread changes are also evident. Many original vegetation communities have been significantly reduced in extent, giving rise in some cases to highly contentious debates in Australian society (eg. regarding the future of the surviving native forests)
Australian fishery stocks are under considerable pressure, both in fresh and salt water, and the major commercial marine fisheries are judged to be either fully exploited or nearly so, or already over-exploited.
Over half the continent has been assessed as requiring remedial treatment for various forms of land degradation, such as soil erosion, salination and structural and chemical decline of soil quality.
Water pollution problems are experienced in many areas, and declining water quality is a cause or concern, especially around urban settlements and in important farming areas.
Local air pollution, although reasonably controlled in some areas, continues to be a serious problem in others, with the accepted international limits of various pollutants often exceeded in the capital cities.
Australia and global ecology
Australian society is one of the high-energy economies of the developed world (Figure 11). On a per person basis, Australians are using energy at the rate of about 60 HEE per day and are producing 50 to 60 kg of carbon dioxide per day. The present per capita rates of energy use and carbon dioxide production in Australia are still on the increase. They are at present about 60% of those of North America, 1.5 times those of the United Kingdom, 3 times those of Spain and Israel, and 60 times those of Nepal and Kenya. Australians use twice as much energy per person and give off twice as much carbon dioxide as was the case in 1960, and 3 times as much as in 1940.
Iron is consumed in Australia at the rate of 2.3 kg per person per day (excluding exported, recycled and imported iron), and gravel at the rate of 25 kg per day.
Australia is thus a typical high-energy society. However, because its population is only 0.3% of the world total, its contribution to carbon dioxide pollution of the biosphere, for example, is only 1.4% of that of humankind as a whole (or 2.2% if we take into account our exports of fossil fuels).
It is sometimes argued that, because Australia�s contribution to global ecological change is relatively small, there is no point in initiating difficult reforms aimed at reducing the rates of resource and energy use and of industrial waste production.
Others put the opposite view. They point out that ecological constraints will demand major changes in patterns of resource and energy use the world over, and that Australia cannot expect to be an exception in this regard. Since these changes will ultimately be obligatory, the sooner we start moving in that direction, the smoother and less painful will be the transition to ecological sustainabilty.
Indeed some people take the view that Australia is in a favoured position to play a leading role internationally in the transition to a truly biosensitive society which satisfies the health needs both of all sections of the human community and of the ecosystems of the biosphere. Because this country has a relatively small population and is well endowed with natural resources, this societal transition could well be easier than in some other parts of the developed world. Our society also has a high level of literacy, facilitating the rapid dissemination of relevant information and new ideas. Furthermore, few countries would be better placed than Australia for the large scale development of solar power as a clean, biosphere-friendly, source of extrasomatic energy.
1. This paper is largely based on the following publication: Our biosphere under threat: ecological realities and Australia�s opportunities (S.Boyden, S.Dovers and M.Shirlow. Oxford University Press, Melbourne. 1990). Readers interested in following up the sources of the information discussed in the paper should consult this book. Other sources include the State of the world reports (L.R.Brown and colleagues. W.W.Norton, New York - annually from 1984).
2. Nature is defined here as things and processes of a kind that existed before human culture became a force in the biosphere.
3. In this paper one generation is taken to be 25 years.
4. This brief desription of the conditions of life of hunter-gatherers is based mainly on the observations of anthropologists working with hunter-gatherer groups in recent times.
5. One Human Energy Equivalent (HEE) is defined as 10 megajoules, which is about the amount of somatic energy used by an average adult human leading a physically active life.
6. ie. absorptive capacity with respect to technological waste products and toxic substances.