Appendix A: Ecosystems and their disruption

It is necessary to survey the essential features of the environment in order to understand how it is being affected by man's activities.

We can define the environment as a system which includes all living things and the air, water and soil which is their habitat. This system is often referred to as the ecosphere. To describe it as a system is to accentuate its unity; a system being something made up of interrelated parts in dynamic interaction with each other and capable, for certain purposes, of co-operating in a common behavioural programme.

Such a programme must be regarded as goal-directed and its goal the maintenance of stability. This appears to be the basic goal of all the self-regulating behavioural processes that make up the ecosphere.

Stability is best defined as a system's ability to maintain its basic features - in other words to survive in the face of environmental change. This means that, in a stable system, change will be minimised and will occur only as is necessary to ensure adaptation to a changing environment. In other words, as stability increases so the frequency of random changes will be correspondingly reduced.

It is easy to see how the ecosphere during the last few thousand million years of evolution has slowly become more stable.

Whereas the deserts, which once covered our planet, reflected the environmental pressures to which they were subjected, the forests that developed to replace them have a capacity to maintain a relatively stable situation in the face of internal and external change. For instance they ensure an optimum balance between the oxygen and carbon dioxide contents of the air by emitting one and absorbing the other. They provide good conditions for the run-off to rivers to be regulated. They periodically shed their leaves which build up humus and hence ensure the continued fertility of the soil. They provide a relatively constant ambient temperature to the wild animals that live within their shade, who, as they evolve also develop stabilising mechanisms ensuring the stability of what is sometimes called their 'internal environment'; the constant body temperature of warm blooded mammals being an obvious example.

Perhaps the most important feature of the ecosphere is its degree of organisation. It is made up of countless ecosystems, themselves organised into smaller ones, which are further organised into still smaller ones. Each of these is made up of populations of different species in close interaction with each other, some of which are usually organised into communities and families-further organised into cells, molecules and atoms etc.

The opposite of organisation is randomness or, what is often referred to as entropy. In fact it can be said that the ecosphere differs from the surface of the moon and probably from that of all the other planets in our solar system, in that randomness, or entropy, have been progressively reduced and organisation, or negative entropy, have been correspondingly increased. According to the second law of thermodynamics, there is a tendency in all systems towards increasing randomness, or entropy. This must be so, since to move in this direction is to take the line of least resistance and also because whenever energy is converted (and this must occur during all behavioural processes), waste, or random parts must be generated- from oxidation and friction if from nothing else.

The ecosphere has succeeded in counteracting this tendency by virtue of several unique features and because it is an open system from the point of view of energy, being continually bombarded with solar radiation.

This radiation is used by green plants during photosynthesis to organise nutrients in the soil into complex plant tissue, which are then eaten by herbivores, and hence reorganised into still more complex animal tissue.

In such processes waste or random parts must be generated. However, so long as the corresponding reduction in organisation is less than the increase in organisation achieved during the process, then entropy will have been reduced. Such increases will be limited by all sorts of factors including the availability of energy and materials, the environment's capacity to absorb waste and the organisational capacity of the system. Waste must therefore be kept down to a minimum. This can only be done by recycling it so as to ensure that the waste generated by one process serves as the materials for the next. This is essential for another reason:

Whereas the ecosphere is an open system as regards energy, it is a closed one as regards materials, which is another reason why all materials must be recycled, and why the waste products of one process must serve as materials for the next.

Also some of the more highly organised materials required for sophisticated processes have taken hundreds of millions of years to develop in the case of fossil fuels, for instance and thousands of millions of years in the case of the herbivorous animals required as food by carnivores. It is thus clear that to avoid increasing entropy, they cannot be used up faster than they are produced. Hence the essential cyclic nature of all ecological processes and the absolute necessity for recycling everything.

It is possible to trace just how all the resources, such as carbon, nitrogen, phosphorus, water, etc., made use of in behavioural processes, are recycled. The food cycle is particularly illustrative. Take the case of a marine ecosystem - fish excrete organic waste which is converted by bacteria to inorganic products. These provide nutrients, permitting the growth of algae which are eaten by fish, and the cycle is complete. In this way the wastes are eliminated, the water kept pure and, at the same time, the materials for the next stage of the process are made available.

One of the most important features of life processes is that they are automatic or self-regulating. Self regulation can only be ensured in one way: data must be detected by the system, transducted into the appropriate informational medium and organised so as to constitute a model or 'template' of its relationship with its environment. Whenever this relationship is modified in such a way that it deviates from the optimum, the model is correspondingly affected and it can be used to guide the appropriate course of action and monitor each new move, until a new position of equilibrium has been reached. This basic cybernetic model explains how all systems, regardless of their level of complexity, adapt to their respective environments. The fact that all the parts of the ecosphere are linked to each other in this way ensures that a general readjustment of the most subtle nature can occur to restore its basic structure after any disturbance.

To suppose that we can ensure the functioning of the ecosphere ourselves with the sole aid of technological devices thereby dispensing with the elaborate set of self-regulating mechanisms that has taken thousands of millions of years to evolve, is an absurd piece of anthropocentric presumption that belongs to the realm of pure fantasy.

It may be possible to replace certain natural controls locally and for a short while without any serious cataclysm occurring but if we push things too far, if for instance the insecticides we use to replace the self-regulating controls that normally ensure the stability of insect populations were to destroy nitrogen-fixing bacteria or pollinating insects, all the money and all the technology in the world would not suffice to replace them and thereby to prevent life processes from grinding to a halt. Yet this substitution is implicit in the aim of industrial society.

As this aim is progressively realised and as we become more and more dependent on technological devices, i.e. external controls, so must there be a corresponding increase in the instability of our social system and hence in our vulnerability to change. Imagine what it will be like when water supplies have been exhausted and we are dependent upon desalination plants for our drinking water; when traditional methods of agriculture have totally given way to ever more ingenious forms of factory farming; and when the natural mechanisms providing us with the air we breathe have been so completely disrupted that vast installations are needed to pump oxygen into the atmosphere and filter out the noxious gases emitted by our industrial installations.

Clearly under such conditions, the slightest technical hitch or industrial dispute, or shortage of some key resource, might be sufficient to deprive us of such basic necessities of life as water, food and air-and bring life to a halt.

If man wishes to survive, to ensure the proper functioning of the self-regulating mechanisms of the ecosphere must be his most basic endeavour. For this to be possible however the latter's essential structure must be respected. Deviations may be possible but only within acceptable limits.

One way of exceeding these limits is to supply the system with more waste than can be used to provide the materials for other processes. In such conditions the system is said to be 'overloaded'; the self-regulating mechanisms can no longer function and the waste simply accumulates. In other words entropy, or randomness, has increased and the surface of the earth resembles that much more that of the moon.

Thus, to return to our marine ecosystem, if the cycle is overloaded with too much sewage, detergents or artificial fertilisers which are nutrients to aquatic plant life, the amount of oxygen required to ensure the decomposition of these substances by the appropriate bacteria may be so high that other organisms will be deprived of an adequate supply.

If this goes on long enough the oxygen level will be reduced to zero. Without oxygen, the bacteria will die and a crucial phase in the cycle will have been interrupted, thereby bringing it rapidly to a halt. As a result, what was once an elaborate ecosystem, supporting countless forms of life in close interaction with each other, now becomes a random arrangement of waste matter.

Needless to say the cycle will also come to a halt if, on the contrary, there were a shortage of nutrients. In such conditions the algae could not survive, and the fish population deprived of its sustenance, would rapidly die off.

This illustrates an essential principle of organisation; there must be an optimum value to every variable in terms of which the system is described. When each variable has its correct value, then the system described can be regarded as having its correct structure. This means that there is no value that can be increased or reduced indefinitely without bringing about the system's eventual breakdown.

To cherish the illusion that the population and affluence of human social systems are exceptions to this law, is, as we shall see, to court the gravest possible calamities.

In order to maintain the system's structure, the actions of the self-regulating sub-systems not only seek to establish a stable relationship with another sub-system, but with their environment as a whole. In other words, they do not aim at satisfying a specific requirement, but at achieving a compromise between a whole set of often competing requirements; that which best satisfies the requirements of the environment as a whole.

Technological devices, of course, do precisely the opposite. They are geared to the achievement of specific short-term targets, regardless of environmental consequences. Since many requirements must be satisfied to maintain stability, such devices, by their very nature, must cause environmental problems and, as a result, they must inevitably tend towards achieving equilibrium positions which display lower rather than higher stability. This means that the probability that disequilibria will occur and their degrees of seriousness are both likely to increase as must the rate at which new devices will be required as well as the effectiveness required of them.

In other words, the role played by technology must increase by positive feedback and our society must become even more addicted to it.

In these circumstances, unless technological innovation can proceed indefinitely at an exponential rate, then it is only a question of time before a disequilibrium occurs for which there is no technological solution, which must spell the complete breakdown of the system.

Industrial society, when it reaches a certain stage of development, begins to affect its environment in yet another manner; it devises, and becomes correspondingly dependent upon, synthetic products of different sorts to replace ever-scarcer natural products. Thus plastics are developed to replace wood products; detergents to replace soaps made from natural fats, synthetic fibres to replace natural fibres; chemical fertilisers to replace organic manure. At the same time, nuclear energy slowly replaces that previously derived from fossil fuels.

It is probable that our ecosphere does not produce a single molecule for which there is not an enzyme capable of breaking it down, in order to perpetuate the essential cycle of life, growth, death and decay. This is not so with synthetic products. They cannot normally be broken down in this way - save in some cases by human manipulation, which is only practicable on a small scale and in specific conditions. It is thus no longer a question of overloading a system. Even the slightest amount of these products, when introduced into our ecosphere, constitutes pollution, while since by their very nature they must continue accumulating, to produce them methodically is to ensure the systematic replacement of the ecosphere with extraneous waste matter.

What is worse, many of these substances find their way into life processes with which they can seriously interfere. Thus strontium 90 gets into the bones of growing children and can give rise to bone cancer; Iodine 131 accumulates in the thyroid gland and can give rise to cancer of the thyroid; DDT accumulates in the fatty matter and in the liver and may cause cancer and other liver diseases; plastics and many other pollutants also accumulate in the liver and kidneys, etc.

It is not surprising that as industrialisation proceeds, so there is a very rapid increase in the so-called degenerative diseases. Carcinogenic agents also tend to be mutagens, and their proliferation must mean a gradual reduction in the adaptiveness of our species, a process that clearly cannot go on indefinitely. [2]

There is another way in which we are degrading the ecosphere. One of its most important features is its complexity. The greater the number of different plant and animal species that make up an ecosystem, the more likely it is to be stable. This is so because, as Elton points out, in such a system every ecological niche is filled. That is to say, every possible differentiated function for which there is a demand within the system is in fact fulfilled by a species that is specialised in fulfilling it. In this way it is extremely difficult for an ecological invasion to occur, i.e. for a species foreign to the system entering and establishing itself, or, worse still, proliferating and destroying the system's basic structure.

It also means that no species forming part of the system is likely to be able to expand beyond its optimum size. The availability and size of an ecological niche undoubtedly constitutes an effective population control. Thus the diet of a specialised member of a highly differentiated ecosystem will itself be of a specialised nature, which means that if the population of a particular species were to increase, or alternatively, to decrease, the food supply of the other species would not be affected. The opposite would be the case with species that normally form part of a simple ecosystem.

Thus goats are adapted to live in mountain areas, where ecological complexity is low, and in order to survive they have to be able to eat almost anything. The result is when they are brought down to the plains, they make short shrift of its vegetation and their proliferation compromises the food supply of many other species.

As industrial man destroys the last wildernesses, as herds of domesticated animals replace inter-related animal species, and vast expanses of crop monoculture supplant complex plant ecosystems, so complexity and hence stability are correspondingly reduced.

Industrial man is also reducing complexity in other ways. For instance, economic pressures force farmers to reduce the number of different strains of crops under cultivation. Only those that present short-term economic advantages tend to survive. This process has been accentuated with the so-called 'green revolution'. Special high yield strains of rice and wheat that respond particularly well to artificial fertilisers have been developed and introduced on a large scale in many parts of the third world. In these areas many other strains have been abandoned. In this way we are reducing complexity, in some cases irreversibly and if anything should happen to the surviving strains, essential crops like wheat and rice could well be jeopardised.

We are reducing complexity in still another way. The greater the number of trophic levels (in other words the greater the length of food chains), the more stable is an ecosystem likely to be. Thus the simplest marine ecosystem would consist of phytoplankton, capable of harnessing the sun's energy and micro-organisms capable of decomposing them. By introducing zooplankton into the system, another link has been introduced into the food chain. These, by preying on the phytoplankton, keep down their numbers and weed out the weak and unadaptive. In this way, they exert both quantitative and qualitative controls, and exert an important stabilising influence. If fish are then introduced to feed on the zooplankton, the system becomes correspondingly more stable.

Needless to say, man's activities are everywhere leading to a reduction in the length of food chains. The larger terrestrial predators have been virtually eliminated in industrial countries, and this process is now taking place in the seas. Man, by refusing to tolerate competitors for his food supply, is ultimately jeopardising the stability of this food supply and hence, its very availability.

Also, as SCEP points out, environmental stress appears to affect predators more radically than herbivores. In aquatic systems the top-level predators, which eat other predators, are the most sensitive of all. This appears to be the case with such disruptive situations as oxygen deficiency, thermal stress, and the introduction of toxic materials such as pesticides and fertilisers.

The effect must be to reduce the number of trophic levels in any ecosystem thereby increasing its instability. SCEP cites several examples:

"Over enrichment by sewage waste and fertiliser runoff of freshwaters, or pollution with industrial wastes, leads to the rapid loss of trout, salmon, pike, and bass. Spraying crops for insect pests has inadvertently killed off many predaceous mites, resulting in outbreaks of herbivorous mites that obviously suffered less. Forest spraying has similarly 'released' populations of scale insects after heavy damage to their wasp enemies."

In addition, SCEP points out that

"such fat-soluble pesticides as DDT are concentrated as they pass from one feeding level to the next. In the course of digestion a predator retains rather than eliminates the DDT content of its prey. The more it eats, the more DDT it accumulates. The process results in especially high concentrations of toxins in predaceous terrestrial vertebrates."

Predators also suffer from the destruction of their food supply. Severe damage to the lower levels in the food chain usually leads to the extinction of the predator before that of the species on which it preys.

There is yet another way in which we are reducing complexity. Populations at any given moment will be made up of individuals of every possible age group. We tend to replace such balanced populations with plantations of trees and other crops which are all of the same age and are particularly vulnerable to diseases affecting them at particular stages in their life cycle. This principle must apply equally well to intensive stock rearing units and especially factory farms. Once more the result is to reduce stability.

Technological devices must also reduce complexity. They constitute external controls exerted by precarious human manipulation. They invariably replace natural controls of a far more complex nature.

Thus, to replace the natural controls which ensure the stability of an insect population by a single chemical pesticide involves a drastic reduction in complexity. The same must be true when we replace the natural mechanisms ensuring soil fertility with nitrogen, phosphorus and potassium which are the main ingredients of artificial fertilisers.

In fact, most human activities are reducing the stability of the ecosphere, which is simply another way of saying that they are determining its systematic degradation.

For several thousand million years, the ecosphere has been developing into an extremely complex organisation of different forms of life in close interaction with each other. In doing this it has been counteracting the basic tendency of all systems towards randomness or entropy. The elaborate mechanisms that have enabled the ecosphere to develop in this manner have been disrupted by man's activities. In his gross presumption, he has sought to replace them with devices causing dereliction and confusion, which rather than seek to satisfy the countless competing requirements of the ecosphere, have been geared to the satisfaction of petty, short-term anthropocentric ends. As a result, the organisational process has been reversed; waste, or random parts, are accumulating faster than organisation is building up. Rather than counteract the inexorable trend towards entropy, industrial man's activities are accelerating it.

If these activities continue to increase exponentially at 6.5 percent per annum, or double every 13½ years, it cannot take many decades before our planet becomes incapable of supporting complex forms of life.

Pollution

Studies of the effects of pollutants on ecosystems have often yielded contradictory results. Rather than attempt to weigh these up, we have chosen to summarise some of the findings of what is almost certainly the most authoritative study: that undertaken in 1969 by an impressive group of scientists from many different disciplines under the auspices of MIT and referred to as The Study of Critical Environmental Problems or SCEP. This study is to be used as background material for the 1972 UN Conference on the Human Environment.

SCEP accentuates the necessity for adopting a holistic approach.

"The significant aspect of human action is man's total impact on ecological systems, not the particular contributions that arise from specific pollutants. Interaction among pollutants is more often present than absent. Furthermore, the total effect of a large number of minor pollutants may be as great as that of one major pollutant. Thus, the total pollution burden may be impossible to estimate except by direct observation of its overall effect on ecosystems."

The scale of human activity can be estimated by comparing specific man-induced processes with the natural rates of geological and ecological processes. It can be shown that in at least 12 cases man-induced rates are as large or larger than the natural rates. [See Table 1]

It is pointed out that with a 5 percent natural growth increment in the mining industries, this will apply to many more materials.

" ... these comparisons show that at least some of our actions are large enough to alter the distribution of materials in the biosphere. Whether these changes are problems, depends upon the toxicity of the material, its distribution in space and time and its persistence in ecological terms."

Most of the disruptive processes already described are well advanced however, and as they occur slowly the most visible effect is a gradual deterioration of ecosystems, "characterised by instability and species loss".

Many lakes and urban centres have severely deteriorated ecosystems. Less severe deteriorations occur more commonly, often as temporary afflictions in ecosystems that otherwise manage to survive intact. This general problem is labelled 'attrition' because it lacks discrete steps of change. Stability is lost more and more frequently, noxious organisms become more common, and the aesthetic aspects of waters and countryside become less pleasing. This process has already occurred many times in local areas. If it were to happen gradually on a global scale, it might be much less noticeable, since there would be no surrounding ecosystems against which to measure such slow changes. Each succeeding generation would accept the status quo as 'natural'.

Energy products

Present and future levels of energy consumption are particularly relevant to estimating our capacity to disrupt ecosystems. The best available calculation appears to be that made by the Battelle Memorial Institute in 1969. In 1968 energy consumption in the US was slightly over 60,000 trillion BTU. It appears to be rising at 3.2 percent per annum and is expected to be 170,000 trillion BTUs by the year 2000.

Over the last 50 years there has been a decreasing amount of energy used for each unit of GNP. The increased technical efficiency of energy used has tended to more than offset the more intense use of energy. The trend, however, appears to be changing. The present policy is to encourage energy use while the technical efficiency of new electric power plants and other energy conversion devices is no longer increasing and may even decrease over the next decades. If this is so, then it is possible that this and other projections have underrated future energy requirements. On the other hand conservation pressures might lead to a reduced usage and this has not been taken into account.

World wide energy consumption projection made by Joel Darmstadter of Resources for the Future has appeared in a work Energy and the World Economy. [See Table 2]

What are likely to be the emissions from power production and other forms of energy production?

It is estimated that in 1967 some 13.4 billion metric tons of CO2 were released from fossil fuel combustion and that emissions in 1980 (using Darmstadter's projection) would be 26 billion metric tons for the world .as a whole.

SCEP points out that the trend towards depleting the remaining stands of original forests, such as those in tropical Brazil, Indonesia and the Congo, will further reduce the capacity of the ecosphere to absorb CO2 and may release even more CO2 to the atmosphere. The CO2 content of the atmosphere is increasing at a rate of 0.2 percent per year since 1958. One can project, on the basis of these trends, an 18 percent increase by the year 2000, i.e. from 320 ppmm to 379 ppmm. SCEP considers that this might increase temperature of the earth by 0.5°C. A doubling of CO2 might increase mean annual surface temperatures by 2°C. [See Table 3]

Heat

Thermal waste energy is increasing at a rate of 5.7 percent per annum, which means that it is likely to increase by a factor of 6 before the end of the century. The total for 1970 was 5.5 million MW which is likely to increase to 9.6 by 1980 and 31.8 million MW by 2000. The effects on global climate are not known.

Emissions of pollutants such as sulphur oxides, nitrogen oxides, hydrocarbons, carbon monoxide and particulate matter, cannot be predicted with any assurance. The theoretical knowledge necessary to make these predictions does not yet exist nor are the relevant facts available.

As far as emissions of radionuclides are concerned the major source will be at the site of fuel reprocessing plants. One estimate is that 99.9 percent of all such emissions entering the environment are from such sources. Concern is expressed for emissions of 'potentially hazardous' radionuclides such as iodine 131, xenon 153, strontium 90, and caesium 137. Possible releases of tritium (hydrogen 3) and krypton 85 are also of concern.

Total emissions would not lead to anything like maximum permissible concentrations (MPC) if dispersal was assured. However, one must take into account the tendency of radionuclides to concentrate in certain organisms and to get into food chains. Concentration factors of 1,000 for caesium in the flesh of bass have been found, of 8,700 in the bones of the blue gills, of 350,000 for radioactivity content in caddis fly larvae, 40,000 for duck egg yolks and 75,000 for adult swallows. Table 4 shows estimated concentration factors for some radionuclides in aquatic organisms.

Phytoplankton also tend to concentrate activation products such as zinc 65, cobalt 67, iron 55 and manganese 54 to an even greater extent than fission products.

When breeder reactors are introduced, plutonium emissions will also become a concern.

The management of concentrated and highly radioactive wastes is a serious problem deserving far more study. Table 5 provides an estimate of accumulated wastes for 1970, 1980 and 2000.

Domestic and agricultural wastes

Dredged wastes from urban areas contain sediment, sewage solids, agricultural and industrial wastes. These also tend to be deposited in rivers or coastal waters. The total amount deposited in this way is estimated at between 150 and 220 million metric tonnes per years, and appears to be increasing at 4 percent per annum.

World production and consumption of chemical fertilisers (except during periods 1914-18 and 1940-45) have doubled or tripled in each decade. Total world use in 1963-64 exceeded 33 million metric tonnes, only 10 per which were used in developing countries. Their share, however, is increasing rapidly.

Present annual world production of pesticides is probably about 1 million metric tonnes. It is likely to go on increasing in view of the increasing world food shortage and because of diminishing returns on their use. Thus to double world food production which as we have seen is likely to be necessary, it will be necessary to increase consumption by no less than 6 times. [See Table 6]

In the industrialised countries there is likely to be a move away from DDT to less persistent but more toxic pesticides such as phorate, dimiton, parathion, etc. These require more frequent sprayings to make up for their reduced persistence. It is unlikely that the developing countries will able to afford them, so consumption of DDT is likely to continue growing.

SCEP points out the way in which agriculture becomes increasingly dependent on the use of these poisons:

"Realisation that the use of pesticides increases the need to continue their use is not new, nor is the awareness that the constant use of pesticides creates new pests. For many of our crops which pesticide use is heavy, the number of pests requiring control increases through time. In a very real sense, new herbivorous insects find shelter among our crops where their predator enemies cannot survive. Fifty years ago, most insect pests were exotic species, accidentally imported to a country lacking their natural enemies. More recently many of the pests, including especially the mites, leaf-rolling insects and a variety of aphid and scale insects, have been indigenous. Thus pesticides not only create the demand for future use (addiction), they also create the demand to use more pesticide more often (habituation). Our agricultural system is already heavily locked into this process, and it is now spreading to the developing countries, it is also spreading into forest management. Pesticides are becoming increasingly 'necessary' in more and more places. Before the entire biosphere is 'hooked' on pesticides, an alternative means of coping with pests should be developed."

Of all pesticides, DDT is the most commonly used, and is now present in the fatty tissue of animals in every part of the world. Its effects are well documented. SCEP summarises some of the implications:

"The oceans are an ultimate accumulation site of DDT and its residues. As much as 25 percent of the DDT compounds produced to date may have been transferred to the sea. The amount in the marine biota is estimated to be in the order of less than 0.1 percent of total production and has already produced a demonstrable impact upon the marine environment.

"Population of fish-eating birds have experienced reproductive failures and population declines, and with continued accumulation of DDT and its residues in the marine ecosystem, additional species will be threatened. The decline in productivity of marine food fish and the accumulation of levels of DDT in their tissues can only be accelerated by DDT's continued release to the environment.

"Certain risks in the utilisation of DDT are especially difficult to quantify, but they require most serious consideration. The rate at which it degrades to harmless products in the marine system is unknown. For some of its degradation products, half-lives are certainly of the order of years, perhaps even of decades. If most of the remaining DDT residues are presently in reservoirs which will in time transfer their contents to the sea, we may expect, quite independent of future manufacturing practices, an increased level of these substances in marine organisms. And if, in fact, these compounds degrade with half-lives of decades, there may be no opportunity to redress the consequences. The more the problems are studied, the more unexpected effects are identified. In view of the findings of the past decade, our prediction of the hazards may be vastly underestimated."

Heavy metals

Pollution by heavy metals also gives cause for concern.

"Some heavy metals are highly toxic to plants and animals including man. They are highly persistent and retain their toxicity for very long periods of time. Some have been used extensively as pesticides and have been dispersed into the environment as pesticides, as uncontrolled industrial wastes and emissions and other means."

Much enters natural water systems through sewage discharges and only a portion is removed by normal sewage treatment.

Those heavy metals that are most toxic, persistent and abundant in the' environment have been selected by SCEP for special review. These include mercury (Hg), lead (Pb), arsenic (As), cadmium (Cd), chromium (Cr), and nickel (Ni). Most heavy metals are biologically accumulated in the bodies of organisms, remain for long periods of time and function as cumulative poisons. Table 7 indicates world production of these metals beteen the years 1963 and 1968 and illustrates the rate at which it is increasing.

It may be worth looking more closely at the problem of mercury pollution which is particularly topical.

SCEP quotes Stocking:

"Elemental mercury and most compounds of mercury are protoplasmic poisons and therefore may be lethal to all forms of living matter. In general, the organic mercury compounds are more toxic than mercury vapour or the inorganic compounds. Even small amounts of mercury vapour or many mercury compounds can produce mercury intoxication when inhaled by man. Acute mercury poisoning, which can be fatal or cause permanent damage to the nervous system, has resulted from inhalation of 1,200 to 8,500 micrograms per cubic meter of mercury. The more common chronic poisoning (mercurialism) which also affects the nervous system is an insidious form in which the patient may exhibit no well-defined symptoms for months or sometimes years after exposure".

Mercury is also dangerous when ingested in food. In Japan 111 cases of mercury poisoning occurred (with 44 deaths) as a result of eating fish taken from Minamata Bay. Another outbreak occurred at Big Niigata City with 26 cases (and five deaths).

Mercury's toxicity is permanent. In addition when fish, shellfish, birds or mammals containing mercury are eaten by other animals the mercury may be absorbed and accumulated.

Industrial wastes and agricultural pesticides have caused severe mercury contamination in waters in Japan, Sweden and the US. Its use is increasing throughout the world and it "threatens to become critical in the world environment". Moreover, as SCEP points out, mercury is but one of approximately two dozen metals that are highly toxic to plants and animals.

Oil pollution

We tend to regard oil pollution of the seas as caused principally by accidental spills like that of the Torrey Canyon. Such accidents cause the most evident damage, "but they make up less than 10 percent of the estimated 2.1 million metric tons of oil that man introduces directly into the world's waters". At least 90 percent originates in the normal operations of tankers, other ships, refineries, petro-chemical plants and submarine oil-wells; from disposal of spent lubricants and other industrial and auto-motive oils; and by fall-out of airborne hydrocarbons emitted by vehicles and industry. [See Table 8]

The actual amount that goes directly into the seas must be taken as proportionate to production. It is normally estimated at 0.1 percent of production but if possible fall-out of airborne hydrocarbons on the sea surface is added it may be as much as 0.5 percent.

This is because estimated emissions of hydrocarbons of petroleum origin to the air is 90 million tons, 40 times that emitted to the seas. Nobody knows how much may finally settle in the seas. SCEP points out that if "10 percent does, then the total hydrocarbon contamination of the oceans could be almost five times the direct influx from ship and land sources".

The increase in the size of tankers must make things worse. The danger of large-scale accidents will increase with the scale of the tankers. 800,000 ton tankers are projected, and "A single spill from one of these would add 20 per cent to the amount of oil entering oceans in a single year". [SCEP] Cleaning up oil spills does more harm than good "even with a non-toxic dispersant, the dispersed oil is much more toxic to marine life than is an oil slick on the surface". [SCEP]

The effect of spills in shallow water is particularly damaging. Thus

"an accidental release of 240 to 280 tons of No. 2 fuel oil from a wrecked barge off West Falmouth, Massachusetts in 1969 caused an immediate massive kill of organisms of all kinds-lobsters, fish, marine worms and molluscs."

The difficulty of estimating biological effects in coastal waters is that

"many other pollutants are also present in this zone and it is hard to separate their different effects. Indeed, the effects may not be separable, but instead additive or mutually reinforcing".

One possible effect of oil dispersed over wide ocean areas could arise from the fact that

"chlorinated hydrocarbons such as DDT and Dieldrin are highly soluble in oil film. Measurements ... in Biscayne Bay, Florida showed that the concentration of a single chlorinated hydrocarbon (dieldrin) in the top 1 millimetre of water containing the slick was more than 10,000 times higher than in the underlying water ... We know that the small larval stages of fishes and both the plant and animal plankton in the food chain tend to spend part of the night hours quite near the surface and it is highly probably that they will extract and concentrate still further, the chlorinated hydrocarbons present in the surface layer. This could have seriously detrimental effects on these organisms and their predators."

Implicit throughout this study is the knowledge that these ecologically disruptive trends cannot be allowed to persist indefinitely. SCEP concludes

"In general, the expected losses from present impacts do not exceed or capacity to carry the burden; this leads us to the conclusion that an intractable crisis does not now seem to exist. Our growth rate, however, is frightening. The impact of two, four or eight times the present ecological demand will certainly incur greater losses in the environment. If the process of change were gradual, the present ecological advantage that is reflected in our 5 to 6 percent annual growth would taper off in the face of decreased environmental services and growth would be correspondingly slowed. Instead, the risk is very great that we shall overshoot in our environmental demands (as some ecologists claim we have already done), leading to cumulative collapse of our civilisation. It seems obvious that before the end of the century we must accomplish basic changes in our relations with ourselves and with nature. If this is to be done, we must begin now. A change system with a time lag of ten years can be disastrously ineffectual in a growth system that doubles in less than fifteen years."

References