James Lovelock
Indice
Gaia
New Look at Life on Earth
1979
Introductory
‘I’d look for an entropy reduction, since this must be a general characteristic of all forms of life.’ Understandably, this reply was taken to be at the best unpractical and at worst plain obfuscation, for few physical concepts can have caused as much confusion and misunderstanding as has that of entropy.
It is almost a synonym for disorder and yet, as a measure of the rate of dissipation of a system’s thermal energy, it can be precisely expressed in mathematical terms. It has been the bane of generations of students and is direfully associated in many minds with decline and decay, since its expression in the Second Law of Thermodynamics (indicating that all energy will eventually dissipate into heat universally distributed and will no longer be available for the performance of useful work) implies the predestined and inevitable run–down and death of the Universe.
Although my tentative suggestion had been rejected, the idea of looking for a reduction or reversal of entropy as a sign of life had implanted itself in my mind. It grew and waxed fruitful until, with the help of my colleagues, Dian Hitchcock, Sidney Epton, and especially Lynn Margulis, it evolved into the hypothesis which is the subject of this book.
Our recognition of living things, both animal and vegetable, is instant and automatic, and our fellow–creatures in the animal world appear to have the same facility. This powerful and effective but unconscious process of recognition no doubt originally evolved as a survival factor. Anything living may be edible, lethal, friendly, aggressive, or a potential mate, all questions of prime significance for our welfare and continued existence. However, our automatic recognition system appears to have paralysed our capacity for conscious thought about a definition of life.
During the present century a few physicists have tried to define life. Bernal, Schroedinger, and Wigner all came to the same general conclusion, that life is a member of the class of phenomena which are open or continuous systems able to decrease their internal entropy at the expense of substances or free energy taken in from the environment and subsequently rejected in a degraded form. This definition is not only difficult to grasp but is far too general to apply to the specific detection of life. A rough paraphrase might be that life is one of those processes which are found whenever there is an abundant flow of energy. It is characterized by a tendency to shape or form itself as it consumes, but to do so it must always excrete low–grade products to the surroundings.
We can now see that this definition would apply equally well to eddies in a flowing stream, to hurricanes, to flames, or even to refrigerators and many other man–made contrivances. A flame assumes a characteristic shape as it burns, and needs an adequate supply of fuel and air to keep going, and we are now only too well aware that the pleasant warmth and dancing flames of an open fire have to be paid for in the excretion of waste heat and pollutant gases. Entropy is reduced locally by the flame formation, but the overall total of entropy is increased during the fuel consumption.
Our findings and conclusions were, of course, very much out of step with conventional geochemical wisdom in the mid–sixties. With some exceptions, notably Rubey, Hutchinson, Bates, and Nicolet, most geochemists regarded the atmosphere as an end–product of planetary outgassing and held that subsequent reactions by abiological processes had determined its present state. Oxygen, for example, was thought to come solely from the breakdown of water vapour and the escape of hydrogen into space, leaving an excess of oxygen behind. Life merely borrowed gases from the atmosphere and returned them unchanged. Our contrasting view required an atmosphere which was a dynamic extension of the biosphere itself.
Working in a new intellectual environment, I was able to forget Mars and to concentrate on the Earth and the nature of its atmosphere. The result of this more single–minded approach was the development of the hypothesis that the entire range of living matter on Earth, from whales to viruses, and from oaks to algae, could be regarded as constituting a single living entity, capable of manipulating the Earth’s atmosphere to suit its overall needs and endowed with faculties and powers far beyond those of its constituent parts.
It is a long way from a plausible life–detection experiment to the hypothesis that the Earth’s atmosphere is actively maintained and regulated by life on the surface, that is, by the biosphere. Much of this book deals with more recent evidence in support of this view.
The chemical composition of the atmosphere bears no relation to the expectations of steady–state chemical equilibrium. The presence of methane, nitrous oxide, and even nitrogen in our present oxidizing atmosphere represents violation of the rules of chemistry to be measured in tens of orders of magnitude. Disequilibria on this scale suggest that the atmosphere is not merely a biological product, but more probably a biological construction: not living, but like a cat’s fur, a bird’s feathers, or the paper of a wasp’s nest, an extension of a living system designed to maintain a chosen environment. Thus the atmospheric concentration of gases such as oxygen and ammonia is found to be kept at an optimum value from which even small departures could have disastrous consequences for life.
We have since defined Gaia as a complex entity involving the Earth’s biosphere, atmosphere, oceans, and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet. The maintenance of relatively constant conditions by active control may be conveniently described by the term ‘homoeostasis’.
In the beginning
The history of the Earth’s climate is one of the more compelling arguments in favour of Gaia’s existence. We know from the record of the sedimentary rocks that for the past three and a half aeons the climate has never been, even for a short period, wholly unfavourable for life. Because of the unbroken record of life, we also know that the oceans can never have either frozen or boiled. Indeed, subtle evidence from the ratio of the different forms of oxygen atoms laid down in the rocks over the course of time strongly suggests that the climate has always been much as it is now, except during glacial periods or near the beginning of life when it was somewhat warmer. The glacial cold spells—Ice Ages, as they are called, often with exaggeration—affected only those parts of the Earth outside latitudes 45° North and 45° South. We are inclined to overlook the fact that 70 per cent of the Earth’s surface lies between these latitudes. The so–called Ice Ages only affected the plant and animal life which had colonized the remaining 30 per cent, which is often partially frozen even between glacial periods, as it is now.
We may at first think that there is nothing particularly odd about this picture of a stable climate over the past three and a half aeons. The Earth had no doubt long since settled down in orbit around that great and constant radiator, the sun, so why should we expect anything different? Yet it is odd, and for this reason: our sun, being a typical star, has evolved according to a standard and well established pattern. A consequence of this is that during the three and a half aeons of life’s existence on the Earth, the sun’s output of energy will have increased by twenty–five per cent. Twenty–five per cent less heat from the sun would imply a mean temperature for the Earth well below the freezing point of water. If the Earth’s climate were determined solely by the output from the sun, our planet would have been in a frozen state during the first one and a half aeons of life’s existence. We know from the record of the rocks and from the persistence of life itself that no such adverse conditions existed.
If we are prepared to consider Gaia as being able, like most living things, to adapt the environment to its needs, there are many ways in which these early critical climatic problems might have been solved. Most creatures can adapt their colouring for the purpose of camouflage, warning, or display. As carbon dioxide was depleted or as the continents drifted to unfavourable positions which raised the albedo, it may have been possible for the biosphere to have kept itself and the Earth warm simply by darkening.
Gaia’s first exercise in actively modifying its environment may have been concerned with climate and the cooler sun, but there are other important environmental properties which have to be kept in subtle balance if life is to persist. Some essential elements are required in bulk, others in trace quantities, and all may need rapid redeployment at times; poisonous wastes and litter must be dealt with and, if possible, put to good use; acidity must be kept in check and a neutral to alkaline overall environment maintained; the seas should stay salt, but not too salt; and so on. These are the main criteria, but there are many others involved.
As we have seen, when the first living system established itself, it was able to take advantage of the abundant supply of key components in its immediate environment, and subsequently the evolving system learned to synthesize these components from the basic raw materials of the air, sea, and the Earth’s crust. Another essential task, as life spread and diversified, would be to ensure a reliable supply of the trace elements needed for specific mechanisms and functions. All living creatures of cellular form employ a vast array of chemical processors, or catalytic agents, called enzymes.
Pollution is not, as we are so often told, a product of moral turpitude. It is an inevitable consequence of life at work. The second law of thermodynamics clearly states that the low entropy and intricate, dynamic organization of a living system can only function through the excretion of low–grade products and low–grade energy to the environment. Criticism is only justified if we fail to find neat and satisfactory solutions which eliminate the problem while turning it to advantage. To grass, beetles, and even farmers, the cow’s dung is not pollution but a valued gift. In a sensible world, industrial waste would not be banned but put to good use. The negative, unconstructive response of prohibition by law seems as idiotic as legislating against the emission of dung from cows.
The recognition of Gaia
At the end of the last century Boltzman made an elegant redefinition of entropy as a measure of the probability of a molecular distribution. It may seem at first obscure, but it leads directly to what we seek. It implies that wherever we find a highly improbable molecular assembly it is probably life or one of its products, and if we find such a distribution to be global in extent then perhaps we are seeing something of Gaia, the largest living creature on Earth.
The state of disequilibrium is one from which, in principle at least, it should be possible to extract some energy, as when a grain of sand falls from a high spot to a low one. At equilibrium, all is level and no more energy is available.
The distinguished Swedish chemist Sillen was the first to calculate what would be the result of bringing the substances of the Earth to thermodynamic equilibrium. Many others have done so since and have substantially confirmed his work. It is one of those exercises where the imagination can be set free through the assistance of a computer as a faithful and willing slave to perform the many tedious calculations.
| Principal components per cent | |||
|---|---|---|---|
| Substance | Present world | Equilibrium world | |
| Air | Carbon dioxide | 0.03 | 98 |
| Nitrogen | 78 | 1 | |
| Oxygen | 21 | 0 | |
| Argon | 1 | 1 | |
| Ocean | Water | 96 | 85 |
| Salt | 3.5 | 13 | |
The complete or partial removal of the ozone layer could have unpleasant consequences for life as we know it. Many species, including man, would be discomforted and some would be destroyed. Green plants, the primary producers of food and oxygen, might suffer but, as has been recently shown, some species of blue–green algae, the primary power transformers of ancient times and modern shores, are highly resistant to short–wave ultra–violet radiation. Life on this planet is a very tough, robust, and adaptable entity and we are but a small part of it. The most essential part is probably that which dwells on the floors of the continental shelves and in the soil below the surface. Large plants and animals are relatively unimportant. They are comparable rather to those elegant salesmen and glamorous models used to display a firm’s products, desirable perhaps, but not essential. The tough and reliable workers composing the microbial life of the soil and sea–beds are the ones who keep things moving, and they are protected against any conceivable level of ultra–violet light by the sheer opacity of their environment.
| Gas | Planet | |||
|---|---|---|---|---|
| Venus | Earth without life | Mars | Earth as it is | |
| Carbon dioxide | 98% | 98% | 95% | 0.03% |
| Nitrogen | 1.9% | 1.9% | 2.7% | 78% |
| Oxygen | trace | trace | 0.13% | 21% |
| Argon | 0.1% | 0.1% | 2% | 1% |
| Surface temperatures °C | 477 | 290±50 | -53 | 13 |
| Total pressure bars | 90 | 60 | 0.006 | 1.0 |
Cybernetics
The American mathematician Norbert Wiener first gave common use to the word ‘cybernetics’ (from the Greek word for ‘steersman’, ‘kubernetes’), to describe that branch of study which is concerned with self-regulating systems of communication and control in living organisms and machines. The derivation seems apt, since the primary function of many cybernetic systems is to steer an optimum course through changing conditions towards a predetermined goal.
What, you may be wondering, has all this to do with Gaia? Possibly a great deal. One of the most characteristic properties of all living organisms, from the smallest to the largest, is their capacity to develop, operate, and maintain systems which set a goal and then strive to achieve it through the cybernetic process of trial and error. The discovery of such a system, operating on a global scale and having as its goal the establishment and maintenance of optimum physical and chemical conditions for life, would surely provide us with convincing evidence of Gaia’s existence.
The distinguished American physiologist Walter B. Cannon has said: ‘The co–ordinated physiological processes which maintain most of the steady states in the organism are so complex and so peculiar to living things, involving, as they may, the brain and the nerves, the heart, lungs, kidneys and spleen, all working together co–operatively, that I have suggested a special designation for these states, homeo–stasis.’ We shall do well to bear these words in mind when seeking to discover whether there is indeed a process for regulating the planetary temperature, and to look for the exploitation by Gaia of a set of temperature control mechanisms, rather than some simple single means of regulation.
To come back to Gaia, how do we recognize an automatic control system when we encounter one? Do we look for the power supply, the regulatory device, or for some complex set of contrivances? As already pointed out, analysis of its parts is usually of little help in showing how a cybernetic system works; unless we know what to look for, recognition of automatic systems by using analytical methods is likely to be just as unsuccessful, whether the system is on a domestic or global scale.
Even though we may find evidence for a Gaian system of temperature regulation, the disentangling of its constituent loops is unlikely to be easy if they are entwined as deeply as in the bodily regulation of temperature. Just as important for Gaia and for all living systems is the regulation of chemical composition. Salinity control, for example, may be a key Gaian regulatory function. If its details are as intricate and complex as those of that amazing organ the kidney, then our quest will be a long one.
The contemporary atmospere
I first became interested in the possibility of the terrestrial atmosphere being part of a biological ensemble, rather than a mere catalogue of gases, when testing the theory that an analysis of the chemical composition of a planetary atmosphere would reveal the presence or absence of life. Our experiments confirmed the theory and at the same time convinced us that the composition of the Earth’s atmosphere was so curious and incompatible a mixture that it could not possibly have arisen or persisted by chance. Almost everything about it seemed to violate the rules of equilibrium chemistry, yet amidst apparent disorder relatively constant and favourable conditions for life were somehow maintained. When the unexpected occurs and cannot be explained as an accidental happening, it is worth seeking a rational explanation. We shall see if the Gaia hypothesis accounts for the strange composition of our atmosphere, with its proposition that the biosphere actively maintains and controls the composition of the air around us, so as to provide an optimum environment for terrestrial life. We shall therefore examine the atmosphere in much the same way that a physiologist might examine the contents of the blood, to see what function it serves in maintaining the living creature of which it is a part.
| Gas | Abundance % | Flux in megatons per year | Extent of disequilibrium | Possible function under the Gaia hypothesis |
|---|---|---|---|---|
| Nitrogen | 79 | 300 | 1010 | Pressure builder Fire extinguisher Alternative to nitrate in the sea |
| Oxygen | 21 | 100,000 | None. Taken as reference | Energy reference gas |
| Carbon dioxide | 0.03 | 140,000 | 103 | Photosynthesis Climate control |
| Methane | 10-4 | 500 | Infinite | Oxygen regulation Ventilation of the anaerobic zone |
| Nitrous oxide | 10-5 | 30 | 1013 | Oxygen regulation Ozone regulation |
| Ammonia | 10-6 | 300 | Infinite | pH control |
| Sulphur gases | 10-8 | 100 | Infinite | Transport gases of the sulphur cycle |
| Methyl chloride | 10-7 | 10 | Infinite | Ozone regulation |
| Methyl iodide | 10-10 | 1 | Infinite | Transport of iodine |
From a chemical viewpoint, although not in terms of abundance, the dominant gas of the air is oxygen. It establishes throughout our planet the reference level of chemical energy which makes it possible, given some combustible material, to light a fire anywhere on the Earth. It provides the chemical potential difference wide enough for birds to fly and for us to run and keep warm in winter; perhaps also to think. The present level of oxygen tension is to the contemporary biosphere what the high–voltage electricity supply is to our twentieth–century way of life. Things can go on without it, but the potentialities are substantially reduced. The comparison is a close one, since it is a convenience of chemistry to express the oxidizing power of an environment in terms of its reduction–oxidation (redox) potential, measured electrically and expressed in volts. It is in fact no more than the voltage of a hypothetical battery with one electrode in the oxygen and the other in the food.
Nearly all the oxygen produced by photosynthesis in green plants and algae is cycled through the atmosphere and used up in that other fundamental activity of life, respiration, in a relatively short space of time. This complementary process can obviously never yield a net increment of oxygen. How then has oxygen accumulated in the atmosphere?
It was thought until recently that the main source was the photolysis of water vapour in the upper layers, where water molecules are split and the hydrogen atoms are light enough to escape the Earth’s gravitational field, leaving the oxygen atoms to couple in molecules of gas or to bond triply in ozone. This process certainly produces a net increment of oxygen, but important though it may have been in the past, it is a negligible source of oxygen in the contemporary biosphere. There seems little doubt that the principal source of oxygen in the atmosphere is the one first proposed by Rubey in 1951, namely, the burial in sedimentary rocks of a small proportion of the carbon which is fixed by green plants and algae in the organic matter of their own tissues. Approximately 0.1 per cent of the carbon fixed annually is buried with the plant debris which is washed and blown down from the land surfaces into the seas and rivers, leaving one additional oxygen molecule in the air for each carbon atom thus removed from the cycle of photosynthesis and respiration. Were it not for this process, oxygen would be steadily withdrawn from the air by reaction with reducing materials exposed by weathering, earth movements, and volcanic outgassing.
Sources of high potential, whether chemical or electrical, are dangerous. Oxygen is particularly hazardous. Our present atmosphere, with an oxygen level of 21 per cent, is at the safe upper limit for life. Even a small increase in concentration would greatly add to the danger of fires. The probability of a forest fire being started by a lightning flash increases by 70 per cent for each 1 per cent rise in oxygen concentration above the present level. Above 25 per cent very little of our present land vegetation could survive the raging conflagrations which would destroy tropical rain forests and arctic tundra alike.
The present oxygen level is at a point where risk and benefit nicely balance. Forest fires do indeed take place, but not with sufficient frequency to interfere with the high productivity that a 21 per cent oxygen level permits.
The sea
We can see now why living organisms, deeply dependent on the operation of electrical forces, can survive only if the salinity of the environment is held within safe limits, and particularly within the critical upper limit of 6 per cent. In the light of this knowledge, we begin to lose interest in the original question: ‘Why is the sea salt?’ Continental run–off and sea–floor spreading easily account for the present level of salinity in the oceans. The more important question is: ‘Why isn’t the sea more salt?’ Catching a glimpse of Gaia, I would answer: ‘Because since life began, the salinity of the oceans has reflected the presence of marine organisms and avoided lethal levels.’ The next question is obviously: ‘But how?’ Which brings us to the crux of the matter, for what we really need to know and think about is not how salt is added to the sea but how it is removed. We are in fact back at the sink looking for a salt–removal process which must be in some way linked with the biology of the sea if our belief in the intervention of Gaia is well–founded.
Let us restate the problem. There is comparatively reliable evidence, both direct and indirect, that the salinity of sea–water has changed very little in hundreds of millions, if not thousands of millions, of years. Our knowledge of the level of salinity tolerated by living organisms of the type that have thrived in the sea over these vast periods suggests that in any event the salinity cannot have exceeded 6 per cent, compared with the present level of 3.4 per cent, and that even if it had risen as high as 4 per cent, life in the sea would have evolved through quite different organisms from those revealed by the fossil record. Yet the amount of salt washed off the land into the sea by rain and rivers during each 80–million–year period is equal to the present total salt content of the oceans. If this process had continued unchecked since their formation, all the oceans would be much too saline for main stream life.
A means must therefore exist for the removal of salt from the sea as fast as it is added. The need for such a device has long been recognized by oceanographers, and several attempts have been made to identify it. The various theories put forward have all relied essentially on non–living inorganic mechanisms, but none has found general acceptance. Broecker has stated that the way in which sodium and magnesium salts are withdrawn from the sea is one of the great unsolved mysteries of chemical oceanography. In fact, two problems need to be solved, for the removal of the positive sodium and magnesium ions and of the negative chloride and sulphate ions have to be treated separately, since positive and negative ions exist independently in a watery medium. To complicate matters further, more sodium and magnesium than chloride and sulphate ions are added to the sea by continental run–off, and to keep things electrically stable, the positive charge carried by the excess ions of sodium and magnesium has to be balanced by negatively charged ions of aluminium and silicon.
Broecker has tentatively suggested that sodium and magnesium are removed by being dropped in the rain of debris that falls constantly to the sea bed, thus becoming part of the sediment, or that they somehow combine with the minerals that constitute the ocean floor. Unfortunately no independent evidence to support either possibility has so far been obtained.
The time scale of these processes is of the order of hundreds of millions of years and is therefore consistent with the salinity record—except in one vital respect. If we assume that the formation of isolated arms of the sea and the upheavals of the Earth’s crust which lead to the burial of salt beds are due entirely to inorganic processes, we must also accept that they will occur entirely at random, both in time and space. They may account for the average level of salinity of the oceans staying within tolerable limits, but large and lethal fluctuations would inevitably have occurred as a result of the random nature of the control processes.
About half of the mass of the living matter in the world is to be found in the sea.
Diatoms, which assimilate silica and flourish in the sea but obviously not in the salt–saturated lakes, spend their brief lives in surface waters. When they die, they sink to the ocean floor and their opaline skeletons pile up as sediment, adding about 300 million tons of silica to the sedimentary rocks each year. Thus the life cycle of these microscopic organisms accounts for the silicon deficiency in the surface waters of the sea, and contributes to its vigorous departure from chemical equilibrium.
This biological process for the use and disposal of silica can be seen as an efficient mechanism for controlling its level in the sea.
From a planetary engineering point of view, the significance of the life cycle of diatoms and coccoliths is that when they die their soft parts dissolve and their intricate skeletons or shells sink to the bottom of the sea. A constant rain of these structures, which oceanographers call ‘tests’, almost as beautiful in death as in life, has fallen on the ocean floor through the aeons, building up great beds of chalk and limestone (from coccoliths) and silicate (from diatoms). This deluge of dead organisms is not so much a funeral procession as a conveyor belt constructed by Gaia to convey parts from the production zone at surface levels to the storage regions below the seas and continents. Some of the soft organic matter falls all the way with the inorganic skeletons and ultimately turns into buried fossil fuels, sulphide ores, and even free sulphur. The whole process has the advantage of built–in yet flexible control systems, based on the responsiveness of living organisms to changes in their environment and their capacity to restore, or adapt to, conditions which favour their own survival.
Now for some proposals about possible Gaian devices for controlling salinity. Although still conjecture, I believe these ideas are solid enough to serve as bases for detailed theoretical and experimental study.
In a lifeless sea, the sediment needed to set off this chain of events might never have lodged itself in the right place. Volcanoes are found on dead planets but, judging by the large one on Mars known as Nix Olympus, they are very unlike their terrestrial counterparts. If Gaia has modified the sea floor, it has been done by exploiting a natural tendency and turning it to her own advantage. I am not, of course, suggesting that all or even most volcanoes are caused by biological activity; but that we should consider the possibility that the tendency towards eruptions is exploited by the biota for their collective needs.
If the idea of major upheavals of the Earth’s crust being manipulated in the interests of the biosphere still offends common sense, it is worth reminding ourselves that man–made dams have occasionally started earthquakes by altering the weight distribution over the surrounding area. The disturbance potential of a mass of sediment or a coral reef is infinitely greater.
Gathering information about the sea, its chemistry, physics, and biology and their interacting mechanisms, should come right at the top of mankind’s list of priorities. The more we know, the better we shall understand how far we can safely go in availing ourselves of the sea’s resources, and the consequences of abusing our present powers as a dominant species and recklessly plundering or exploiting its most fruitful regions. Less than a third of the Earth’s surface is land. This may be why Gaia has been able to contend with the radical transformations wrought by agriculture and animal husbandry, and will probably continue to strike a balance as our numbers grow and farming becomes ever more intensive. We should not, however, assume that the sea, and especially the arable regions of the continental shelves, can be farmed with the same impunity. Indeed, no one knows what risks are run when we disturb this key area of the biosphere. That is why I believe that our best and most rewarding course is to sail with Gaia in view, to remind us throughout the voyage and in all our explorations that the sea is a vital part of her.
Gaia and Man: the problem of pollution
It is all too easily overlooked that Nature, apart from being red in tooth and claw, does not hesitate to use chemical warfare if more conventional weapons prove inadequate. How many of us recognize that the insecticide which is sprayed in the home to kill flies and wasps is a product of chrysanthemums? Natural pyrethrum is still one of the most effective substances for killing insects.
By far the most poisonous substances known are natural products. The Botulinus toxin produced by bacteria, or the deadly product of the algal dinoflagellates which cause the red tide at sea, or the polypeptide manufactured by the death–cap fungus: all three are entirely organic products and but for their toxicity would be suitable candidates for the shelves of the health food store. The African plant Dichapetalum toxicarium and some related species have learnt to perform fluorine chemistry. They incorporate the fiery element fluorine within natural substances such as acetic acid, and fill their leaves with the resulting salt compound. This deadly substance has been referred to by biochemists as a metabolic monkey–wrench, which graphically illustrates the havoc it causes at a molecular level when drawn into the gear wheels of the chemical cycles of almost any other living organism. If it were solely an industrial product, it would be cited as yet another example of man’s perverse and wicked use of chemical technology to hit below the belt and improve his position in the biosphere. Yet it is a natural product and only one of many highly toxic substances which are made organically and enable their possessors to take a mean advantage. There is no Geneva Convention to limit natural dirty tricks. One of the Aspergillus family of moulds has discovered how to make a substance called aflatoxin which is mutagenic, carcinogenic, and teratogenic; in other words it can cause mutations, tumours, and foetal abnormalities. It is known to have caused a vast amount of human misery through stomach and liver cancer resulting from the eating of food naturally polluted by this aggressive chemical.
Could it be that pollution is natural? If by pollution we mean the dumping of waste matter there is indeed ample evidence that pollution is as natural to Gaia as is breathing to ourselves and most other animals.
The very concept of pollution is anthropocentric and it may even be irrelevant in the Gaian context. Many so–called pollutants are naturally present and it becomes exceedingly difficult to know at what level the appellation ‘pollutant’ may be justified. Carbon monoxide, for example, which is poisonous to us and to most large mammals, is a product of incomplete combustion, a toxic agent from exhaust gases of cars, coke or coal–burning stoves, and cigarettes; a pollutant put into otherwise clean fresh air by man, you might think. However, if the air is analysed we find that carbon monoxide gas is to be found everywhere. It comes from the oxidation of methane gas in the atmosphere itself and as much as 1,000 million tons of it are so produced each year.
The parts of the Earth responsible for planetary control may still be those which carry the vast hordes of micro-organisms. The algae of the sea and of the soil surface use sunlight to perform the prime task of living chemistry, photosynthesis. They still turn over half of the Earth’s supply of carbon, in co-operation with the aerobic decomposers of the soil and the sea-bed, together with the anaerobic microflora in the great mud zones of the continental shelves, sea bottom, marshes, and wet lands. The large animals, plants, and seaweeds may have important specialist functions, but the greater part of Gaia’s self-regulating activity could still be conducted by micro-organisms.
Among the relatively few firm predictions about man’s future is the one that our present numbers will, within the next few decades, at least double. The problem of feeding a world population of 8,000 million without seriously damaging Gaia would seem more urgent than that of industrial pollution. It may be argued, yes, but what of the more subtle poisons? The pesticides and herbicides, to say nothing of the ozone depleters, are surely the greatest threat?
What of the fashionable contemporary doom by pollution, the erosion of the Earth’s fragile shield against the deadly ultra–violet radiation of the sun? We are indebted to Paul Crutzen and Sherry Rowland for having alerted us to the potential threat to the ozone layer arising from the nitrogen oxides and the chlorofluorocarbons.
At the time of writing, ozone in the stratosphere continues its wavering but obstinate increase in density, as if unaware that it is supposed to be decreasing. Yet the arguments presented for its eventual depletion by pollutants are so convincing and reasonable that both law–makers and atmospheric scientists are concerned and uncertain as to the best course of action. Here Gaian experience may point the way. If the calculations by aeronomists are correct, then many natural events in the past should have profoundly depleted the ozone layer. For example, a major volcanic eruption such as Krakatoa in 1895 is likely to have injected vast quantities of chlorine compounds into the stratosphere which it is estimated could have depleted ozone by as much as 30 per cent. This figure represents at least twice the extent of depletion which is expected to take place by the year 2010 if chlorofluorocarbons continue to be released into the air at their present rate. Other untoward events include solar flares, large meteoric collisions, magnetic field reversals of the Earth, the supernova explosions of nearby stars, and possibly even the pathological overproduction of nitrous oxide in the soil and the sea. Some or all of these incidents must have occurred with relative frequency in the past and will have generated in the stratosphere large volumes of the nitrogen oxides which are claimed to destroy the ozone. The survival of our own species and of the rich variety of life throughout Gaia seems conclusive evidence either that ozone depletion cannot be as lethal as it is often made out to be or that the theories are wrong and it never was depleted. Moreover, during the first 2,000 million years of life’s presence on Earth there was no ozone at all and surface life, the bacteria and blue–green algae, may have been exposed to the full unshielded flood of ultra–violet from the sun.
The continental shelves cover a vast area, at least that of the continent of Africa. As yet, the farming of these regions is on a negligible scale, but we must not forget how rapidly mineral exploration has led to the successful establishment of oil and gas extraction plants for mining the fuel fields beneath the continental shelves. Once a resource is recognized, it does not take our species long to exploit it to the full.
The ‘core’ regions of Gaia, those between latitudes 45° North and 45° South, include the tropical forests and scrub lands. We may also need to keep a close eye on these areas if we are to guard against unpleasant surprises. It is well recognized that the agriculture of the tropical belt is often inefficient and that large stretches are already worked out or are being devastated through the same sort of primitive farming methods which led to the Bad Lands of the United States. What is less well known is that this bad farming is also disturbing the atmosphere on a global scale and to an extent at least comparable with the effects of urban industrial activity.
It is a common practice to clear scrub and forest land by burning, and also to burn off grass each year. Fires of this type inject into the air, in addition to carbon dioxide, a vast range of organic chemicals and a huge burden of aerosol particles. Some of the chlorine now in the atmosphere is in the form of the gas methyl chloride, a direct product of tropical agriculture. Grass and forest fires generate at least five million tons of this gas each year, a far greater amount than is released by industry and probably also greater than the natural influx from the sea.
Methyl chloride is but one substance which we now know to be produced in abnormal quantities as a consequence of primitive agriculture. The brutal disturbance of natural ecosystems always involves the danger of upsetting the normal balance of atmospheric gases. Changes in the production rate of gases such as carbon dioxide or methane and of aerosol particles may all cause perturbations on a global scale. Moreover, even if Gaia is there to regulate and modify the consequences of our disruptive behaviour, we should remember that the devastation of the tropical ecosystems might diminish her capacity to do so.
It seems therefore that the principal dangers to our planet arising from man’s activities may not be the special and singular evils of his urbanized industrial existence. When urban industrial man does something ecologically bad he notices it and tends to put things right again. The really critical areas which need careful watching are more likely to be the tropics and the seas close to the continental shores. It is in these regions, where few do watch, that harmful practices may be pursued to the point of no–return before their dangers are recognized; and so it is from these regions that unpleasant surprises are most likely to emerge. Here man may sap the vitality of Gaia by reducing productivity and by deleting key species in her life–support system; and he may then exacerbate the situation by releasing into the air or the sea abnormal quantities of compounds which are potentially dangerous on a global scale.
In the long run we have to guard against the dismal possibility that Rachel Carson was right but for the wrong reason. There may well come a silent spring bereft of bird song with the birds victims of DDT and other pesticides. If this does happen it will not be a consequence of their direct poisoning by the pesticides but because the saving of human lives by these agents will have left no room, no habitat, on Earth for the birds. As Garrett Hardin has said, the optimum number of people is not as large as the maximum the Earth can support; or, as it has been more bluntly expressed, ‘There is only one pollution … People.’
Living within Gaia
It can perhaps now be seen why we have not previously discussed Gaia within the context of any branch of ecology. Whatever this science may have been originally, it has grown ever more associated in the public mind with human ecology. The Gaia hypothesis, on the other hand, started with observations of the Earth’s atmosphere and other inorganic properties. Where life is concerned, it focuses special attention on what most people consider to be the lowest part, that represented by the micro–organisms. The human species is of course a key development for Gaia, but we have appeared so late in her life that it hardly seemed appropriate to start our quest by discussing our own relationships within her.
Having assumed her existence, let us consider three of Gaia’s principal characteristics which could profoundly modify our interaction with the rest of the biosphere.
- The most important property of Gaia is the tendency to keep constant conditions for all terrestrial life. Provided that we have not seriously interfered with her state of homoeostatis, this tendency should be as predominant now as it was before man’s arrival on the scene.
- Gaia has vital organs at the core, as well as expendable or redundant ones mainly on the periphery. What we do to our planet may depend greatly on where we do it.
- Gaian responses to changes for the worse must obey the rules of cybernetics, where the time constant and the loop gain are important factors. Thus the regulation of oxygen has a time constant measured in thousands of years. Such slow processes give the least warning of undesirable trends. By the time it is realized that all is not well and action is taken, inertial drag will bring things to a worse state before an equally slow improvement can set in.
It therefore seems important in the context of Gaia to ask: ‘What has been the effect of all or any of these recent developments? Is technological man still a part of Gaia or are we in some or in many ways alienated from her?’
I am grateful to my colleague Lynn Margulis for demystifying these most difficult questions about Gaia by observing that: ‘Each species to a greater or lesser degree modifies its environment to optimize its reproduction rate. Gaia follows from this by being the sum total of all of these individual modifications and by the fact that all species are connected, for the production of gases, food and waste removal, however circuitously, to all others.’ In other words, like it or not, and whatever we may do to the total system, we shall continue to be drawn, albeit unawares, in to the Gaian process of regulation. Since we are not yet a completely social species, we may be participating on both the community and personal levels.
Coming to our second characteristic, what regions of the Earth are vital to Gaia’s well–being? Which ones could she do without? On this subject we already have some useful information. We know that the regions of the globe outside latitudes 45° North and 45° South are subject to glaciations, when vast overburdens of ice and snow all but sterilize the land and in places bulldoze the soil away down to the bedrock itself. Even though most of our industrial centres are in the northern temperate regions which are subject to glaciations, nothing we have done so far by way of industrial scarring and pollution in these areas can equal the natural devastations of the ice. It seems, therefore, that Gaia can tolerate the loss of these parts of her territory, about 30 per cent of the Earth’s surface, although her present losses are somewhat less, since in between glaciations there are still regions of ice and permafrost. However, in times past the fertile regions of the tropics were unaffected by man and could therefore have made good the losses suffered during ice ages. Can we be sure that another Ice Age could be endured, once the core regions of the Earth’s surface have been denuded of their forests, as they may well be in a few decades from now?
It will no doubt be decided in due course by natural selection which is the most fit to survive: a maximum population of humans living at bare subsistence level in a semi–desert—the ultimate welfare world—or some other less costly social system with fewer people. It could be argued that a world with tens of thousands of millions of human beings on its surface is not only possible but tolerable, through the continued development of technology. The amount of regimentation, self–discipline, and sacrifice of personal freedom that would of necessity be imposed on everyone in such a crowded world must make it unacceptable to many by our present standards.
If we are lucky we may find that the vital organs in the body of Gaia are not on the land surfaces but in the estuaries, wet lands, and muds on the continental shelves. There, the rate of carbon burial adjusts automatically to regulate the concentration of oxygen, and essential elements are returned to the atmosphere. Until we know much more about the Earth and the role of these regions, vital or otherwise, we had much better set them outside the limits for exploitation.
There may, of course, be other and unexpected vital areas. We do not know, for instance, how important is the output of methane to the air from anaerobic micro–organisms.
In his pioneering research into the biochemistry of the atmosphere, Hutchinson suggested that nearly all atmospheric methane might come from this source. It could just be true that at some time the additional amount of methane and other gases produced in our guts made all the difference.
A detailed examination of the cycles which regulate the atmospheric concentration of oxygen will reveal a network of intricate loops, one so complex as still to defy complete analysis. This brings us to the third property of Gaia, namely that she is a cybernetic system. The many pathways involved in regulation can have associated with them different time constants and different functional capacities, or as the engineer might say, variable loop gains. The larger the proportion of the Earth’s biomass occupied by mankind and the animals and crops required to nourish us, the more involved we become in the transfer of solar and other energy throughout the entire system. As the transfer of power to our species proceeds, our responsibility for maintaining planetary homoeostasis grows with it, whether we are conscious of the fact or not. Each time we significantly alter part of some natural process of regulation or introduce some new source of energy or information, we are increasing the probability that one of these changes will weaken the stability of the entire system, by cutting down the variety of response.
What is remarkable about man is not the size of his brain, no greater than that of a dolphin, nor his loose incomplete development as a social animal, nor even the faculty of speech or his ability to use tools. Man is remarkable because by the combination of all of these things he has created an entirely new entity. When socially organized and equipped with a technology even as rudimentary as that of a Stone Age tribal group, man has the novel capacity to collect, store, and process information, and then use it to manipulate the environment in a purposeful and anticipatory fashion.
If we scan backwards over the history of man as a collective species and direct our attention particularly to his relationships with the global environment, we discern a series of repetitions. There are periods of rapid technological development leading to what seems to be an environmental catastrophe. This is followed by a quite lengthy period of stability and coexistence with a new and modified ecosystem. Fire–drive hunting led to the destruction of forest ecosystems, but was followed by the establishment of the great grassland ecosystems, the savannahs, and a new period of coexistence.
It is a fact of life that new evolutionary developments cause distress to the established order. This is so at all levels of life. There is the example at the lowest level of the mutation of a virus from one which causes discomfort to one that is lethal.
Our continuing development as an intelligent social animal with an ever–increasing dependence upon technology has inevitably disturbed the other living things and will continue to do so. The mutation rate of man himself may be very slow but the rate of change of the collective association which constitutes mankind is increasing all the time. Richard Dawkins has observed that both major and minor technological advances can be regarded as analogous to mutations in this context.
To everything there is a season, and a time to every purpose under the heaven; a time to be born, and a time to die; a time to plant, and a time to pluck up that which is planted. I returned, and saw under the sun, that the race is not to the swift, nor the battle to the strong, neither yet bread to the wise, nor yet riches to men of understanding, nor yet favour to men of skill, but time and chance happeneth to them all.
Beauty is truth, truth beauty—that is all
Ye know on Earth, and all ye need to know.
There can be no prescription, no set of rules, for living within Gaia. For each of our different actions there are only consequences.
Epilogue
This chapter begins autobiographically so that I may bring us the more easily to consider the most speculative and intangible aspects of the Gaia hypothesis: those which concern thought and emotion in the interrelationship of man and Gaia.
Let us start by considering our sense of beauty. By this, I mean those complex feelings of pleasure, recognition, and fulfilment, of wonder, excitement, and yearning, which fill us when we see, feel, smell, or hear whatever heightens our self–awareness and at the same time deepens our perception of the true nature of things. It has often been said—and for some, ad nauseam—that these pleasurable sensations are inextricably bound up with that strange hyperaesthesia of romantic love. Even so, there seems no need inevitably to attribute the pleasure we feel on a country walk, as our gaze wanders over the downs, to our instinctive comparison of the smooth rounded hills with the contours of a woman’s breasts. The thought may indeed occur to us, but we could also explain our pleasure in Gaian terms.
Part of our reward for fulfilling our biological role of creating a home and raising a family is the underlying sense of satisfaction. However hard and disappointing at times the task may have been, we are still pleasurably aware at a deeper level of having played our proper part and stayed in the mainstream of life. We are equally and painfully aware of a sense of failure and loss if for some reason or other we have missed our way or made a mess of things.
It may be that we are also programmed to recognize instinctively our optimal role in relation to other forms of life around us. When we act according to this instinct in our dealings with our partners in Gaia, we are rewarded by finding that what seems right also looks good and arouses those pleasurable feelings which comprise our sense of beauty. When this relationship with our environment is spoilt or mishandled, we suffer from a sense of emptiness and deprivation. Many of us know the shock of finding that some peaceful rural haunt of our youth where once the wild thyme blew and where the hedges were thick with eglantine and may, has become a featureless expanse of pure weed–free barley.
Another of our instincts which probably favours survival is that which associates fitness and due proportion with beauty in individuals. Our bodies are formed of cell co–operatives. Each nucleus–containing body cell is an association of lesser entities in symbiosis. If the product of all this co–operative effort, a human being, seems beautiful when correctly and expertly assembled, is it too much to suggest that we may recognize by the same instinct the beauty and fittingness of an environment created by an assembly of creatures, including man, and by other forms of life? Where every prospect pleases, and man, accepting his role as a partner in Gaia, need not be vile.
The churches and the humanist movements have sensed the powerful emotional charge generated by the environmental campaign and have re–examined their tenets and beliefs so as to take account of it. There is, for example, a fresh awareness of the concept of Christian stewardship whereby man, while still allowed dominion over the fish and the fowl and every living thing, is accountable to God for the good management of the Earth.
From a Gaian viewpoint, all attempts to rationalize a subjugated Earth with man in charge are as doomed to failure as the similar concept of benevolent colonialism. They all assume that man is the possessor of this planet; if not the owner, then the tenant. The allegory of Orwell’s Animal Farm takes on a deeper significance when we realize that all human societies in one way or another regard the world as their farm. The Gaia hypothesis implies that the stable state of our planet includes man as a part of, or partner in, a very democratic entity.
Among several difficult concepts embodied in the Gaia hypothesis is that of intelligence. Like life itself, we can at present only categorize and cannot completely define it. Intelligence is a property of living systems and is concerned with the ability to answer questions correctly.
With creatures who possess the capacity of conscious thought and awareness, and no one as yet knows at what level of brain development this state exists, there is the additional possibility of cognitive anticipation. A tree prepares for winter by shedding its leaves and by modifying its internal chemistry to avoid damage from frost. This is all done automatically, drawing on a store of information handed down in the tree’s genetic set of instructions. We on the other hand may buy warm clothes in preparation for a journey to New Zealand in July. In this we use a store of information gathered by our species as a collective unit and which is available to us all at the conscious level. So far as is known, we are the only creatures on this planet with the capacity to gather and store information and use it in this complex way. If we are a part of Gaia it becomes interesting to ask: ‘To what extent is our collective intelligence also a part of Gaia? Do we as a species constitute a Gaian nervous system and a brain which can consciously anticipate environmental changes?’
Whether we like it or not, we are already beginning to function in this way. Consider, for example, one of those mini–planets, like Icarus, a mile or so in diameter and with an irregular orbit intersecting that of the Earth. Some day the astronomers may warn us that one of these is on a collision course with the Earth and that impact will occur within, say, a few weeks’ time. The potential damage from such a collision could be severe, even for Gaia. This kind of accident has probably happened to the Earth in the past and caused major devastation. With our present technology, it is just possible that we could save ourselves and our planet from disaster.
It might equally well happen that advances in climatology revealed the approach of a particularly severe glacial epoch. We saw in chapter 2 that although another Ice Age might be a disaster for us, it would be a relatively minor affair for Gaia. However, if we accept our role as an integral part of Gaia, our discomfort is hers and the threat of glaciation is shared as a common danger. One possible course of action within our industrial capacity would be the manufacture and release to the atmosphere of a large quantity of chlorofluorocarbons. When these controversial substances, now present in the air at one–tenth of a part per thousand million, are increased in concentration to several parts per thousand million, they would serve, like carbon dioxide, as greenhouse gases preventing the escape of heat from the Earth to space. Their presence might entirely reverse the onset of a glaciation, or at least greatly diminish its severity.
Still more important is the implication that the evolution of homo sapiens, with his technological inventiveness and his increasingly subtle communications network, has vastly increased Gaia’s range of perception. She is now through us awake and aware of herself.
