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THE AGES OF GAIA: A BIOGRAPHY OF OUR LIVING EARTH |
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7: Gaia and the Contemporary Environment
A rough, stony track led forward across the thin moorland grass and then dropped into the bare, rock-strewn bed of the River Lydd; straight ahead rose the small mountain of Widgery Tor, a sort of turret on the walls of that castle-like massif that was Dartmoor. On a clear, sunny day it was a grand and romantic prospect to reward the small effort of a country walk. The second day of August 1982 was just such a sunny day, but the moorland vision was all but lost in a dense and dirty brown haze. The air was corrupted by the fumes of Europe's teeming millions of cars and trucks. Their flatus oozed in a gentle easterly drift of wind from the continent; ineluctable chemistry driven by sunlight stewed the fumes into a witches' brew that seared the green leaves. Even my eyes, though washed by the flow of tears, began to smart; soon personal discomfort drew my attention from the contemplation of the mask of photo-chemical smog that obscured the jeweled brightness of the West Country scene. A visitor from Los Angeles would instantly have recognized it for what it was, but Europeans, still in the late stages of their honeymoon with personal transport, cannot admit to themselves that their beloved cars fart anything so foul as smog. This vision of a blighted summer's day somehow encapsulates the conflict between the flabby good intentions of the humanist dream and the awful consequences of its near realization. Let every family be free to drive into the countryside so that they can enjoy its fresh air and scenic beauty; but when they do, it all fades away in the foul haze that their collective motorized presence engenders. As I climbed the Tor and thought these thoughts I knew also that, in driving myself to the foothills at the start of the walk, I had added a small but culpable increment of hydrocarbons and of sulfur and nitrogen oxides to the over-laden air. I also knew that my dislike of this kind of air pollution was a value judgment, and a minority one at that. There can be very few who do not in some way add to the never-ceasing demolition of the natural environment. Characteristically, arrogantly, we blame technology rather than ourselves. We are guilty, but what is the offence? Many times in the Earth's history new species with some powerful capacity to change the environment have done as much, and more. Those simple bacteria that first used sunlight to make themselves and oxygen were the ancestors of the trees today but eventually, simply by living and by doing their photochemical trick, they so profoundly altered the environment that vast ranges of their fellow species were destroyed by the poisonous oxygen that accumulated in the air. Other simple microorganisms have in their communities acted so that mountain ranges formed and continents were set in motion over the surface of the Earth. Looked at from the time scale of our own brief lives, environmental change must seem haphazard, even malign. From the long Gaian view, the evolution of the environment is characterized by periods of stasis punctuated by abrupt and sudden change. The environment has never been so uncomfortable as to threaten the extinction of life on Earth, but during those abrupt changes the resident species suffered catastrophe whose scale was such as to make a total nuclear war seem, by comparison, as trivial as a summer breeze is to a hurricane. We are ourselves a product of one such catastrophe. Could it be that we are unwittingly precipitating another punctuation that will alter the environment to suit our successors? A group of scientists from all parts of the world met in 1984 at Sao Jose dos Campos in Brazil. The meeting, held at the request of the United Nations University, posed the question, "How does human intervention in the natural ecosystems of the human tropics affect the forest, the regions around it, and the whole world?" It soon became clear that, whatever their disciplines, the specialists had little to offer other than a frank and honest admission of ignorance. Asked, "When shall we know the consequences of removing the forest from Amazonia?" they could only answer, "Not before the forests have gone." It seemed as if we were at a stage in understanding the health of Gaia rather like that of a physician before scientific medicine existed. In The Youngest Science, Lewis Thomas lets us identify with a young medical practitioner whose first experiences were in the 1930s. Even for those who knew medicine then, it is astonishing to be reminded how little there was that a physician could do to cure a patient. The practice of medicine was largely a matter of administering symptomatic relief and trying to insure that the environment of the patient was that most favorable for the powerful natural processes of healing that we all possess. Early in its history, medical wisdom accumulated by shrewd observation and by trial and error. The discovery of the curative value of drugs like quinine, or of that wonderful panacea for pain and discomfort, opium, was not in some brightly lit laboratory. Rather, it was in the early experiments or observations of a village genius who realized that there were real benefits to be had from chewing that bitter bark of the cinchona tree or real comfort implicit in the dried latex of the poppy head. Physiology, the systems science of people and animals, was at first an unrecognized background, but later came to influence further progress. The recognition by Paracelsus that the poison is the dose is a physiological enlightenment still to be discovered by those who seek the unattainable and pointless goal of zero for pollutants.
The discovery by William Harvey of the circulation of the blood added to the wisdom of medicine, just as the discovery of meteorology added to our understanding of the Earth. The expert sciences of biochemistry and microbiology came much later, and it was a long time before their new knowledge could enhance the practice of medicine. Even as I write, a paper has appeared in Nature describing the molecular structure of the virus responsible for the acquired immune deficiency syndrome; but it will be a long time before this astonishing feat of biochemistry rescues those now dying of AIDS and comforts those who fear that strange and deadly malady. It seemed oddly appropriate to gather in Brazil; as if we were old-style clinicians conferring at the bedside of a patient with an untreatable disease. We recognized the inadequacy of our expertise and the need for a new profession: planetary medicine, a general practice for the diagnosis and treatment of planetary ailments. We thought that it would grow from experience and empiricism just as medicine had done. It also seemed to some of us that geophysiology, the systems science of the Earth, might serve as did physiology in the evolution of medicine, as a scientific guide for the development of this putative profession. This chapter, therefore, will be a look at the real and imaginary problems of Gaia through the eyes of a contemporary practitioner of planetary medicine. The scientific background, geophysiology, has already been touched on in the preceding chapters. So let us look at the physical signs, the clinical features, to see if anything can be diagnosed. It is true that, in the case of Gaia, the complaint comes not from the patient but rather from the intelligent fleas that infest her. There is nothing to stop us, however, from going through a routine examination of the temperature charts and the biochemical analyses of the body fluids.
So begins the first chapter of that splendid book, Carbon Dioxide Review 1982, edited by William Clark. Unless some significant new discoveries have been made between the time of its publication and your reading of this, I suspect that it will still be among the best sources of information on this complex subject. From the very beginning of life on Earth, carbon dioxide has had a contradictory role. It is the food of photosynthesizers and therefore of all life; the medium through which the energy of sunlight is transformed into living matter. At the same time it has served as the blanket that kept the Earth warm when the Sun was cool, a blanket that, now the Sun is hot, is becoming thin; yet one that must be worn, for it is also our sustenance as food. We have seen earlier how the biota everywhere on the land and sea are acting to pump carbon dioxide from the air so that the carbon dioxide which leaks into the atmosphere from volcanoes does not smother us. Without this never-ceasing pumping, the gas would rise in concentration within a hundred thousand years to levels that would make the Earth a torrid place, and unfit for almost all life here now. Carbon dioxide for Gaia is like salt for us. We cannot live without it, but too much is a poison.
For humans, a hundred thousand years is almost indistinguishable from infinity; to Gaia, who is about 3.6 eons old, it is equivalent to no more than three of our months. Gaia has cause for concern about the long-term decline of carbon dioxide, but the rise of carbon dioxide from burning fossil fuels is, for her, just a minor perturbation that lasts but an instant of time. She is, in any case, tending to offset the decline. Before we dismiss Gaia from our worries about carbon dioxide, we should bear in mind that among the things that can happen in an instant is the impact of a bullet in full flight. Small it may be, and short the time of contact, but disastrous are its consequences. So it could be with Gaia and carbon dioxide. Humans may have chosen a very inconvenient moment to add carbon dioxide to the air. I believe that the carbon dioxide regulation system is nearing the end of its capacity. The air in recent times has been uncomfortably thin in carbon dioxide for mainstream vegetation and, as was mentioned in the last chapter, new species with a different biochemistry are evolving. These new species, the C4 plants, can live at very low carbon dioxide levels and might at some future time replace the older obsolete C3 models, as the gas continues its progressive down-ward course. The progression is not a smooth one, but more like the trembling and jerky gait of the elderly. We know that carbon dioxide has fallen in abundance during the Earth's history, but it jumped from 180 to near 300 parts per million within a hundred years as the last glaciation ended. A rapid rise like this can have come only from the sudden failure of the pumps. It cannot be explained by the slow processes of geochemistry. The rate and the extent of the rise of carbon dioxide now under way as a result of our actions is comparable with that of the natural rise that terminated the last ice age. Some time in the next century it seems likely that the increment we add will be equal to that caused by the failure of the pumps some 12,000 years ago. The change of climate we need to think about, therefore, is possibly one as large as that from the last ice age until now; one that would make winter spring, spring summer, and summer always as hot as the hottest summer you can recall. To comprehend such a change at the personal level, imagine you are a citizen of a mid-continental town such as Chicago or Kiev. The change is as great as from the bitter cold of winter that has passed to the fierce heat of summer soon to come. In his book, William Clark compares the predictions that economists have made of growth from now until the middle of the next century. Among them is listed the prediction by Amory and Hunter Lovins, who argue plausibly that growth may be close to zero into the foreseeable future. This is a very different prediction from that of the late, great Herman Kahn, who saw the whole world in the next century as a vast and wealthy suburban development. Scarsdale writ large. There is strong objective evidence from the record of industrial production that the Lovins' prediction is nearer the truth. Since 1974 the turnover of energy and materials by the human world has been in steady state. Even so, unless we greatly decrease the rate of burning fossil fuel, the atmospheric carbon dioxide will continue to rise to its own steady state and will have doubled in concentration by between 2050 and 2100. I can only guess the details of the warm spell due. Will Boston, London, Venice, and the Netherlands vanish beneath the sea? Will the Sahara extend to cross the equator? The answers to these questions are likely to come from direct experience. There are no experts able to forecast the future global climate. Some wisdom comes from geophysiology, which reminds us that the Earth is an active and responsive system and not just a damp and misty sphere of rock. Systems in homeostasis are forgiving about perturbations, and work to keep the comfortable state. Maybe, if left to herself, Gaia could absorb the excess carbon dioxide and the heat that it brings. But Gaia is not left to herself; in addition to carbon dioxide increments, we are also busy removing that part of the plant life, the forests, that by responsive extra growth might serve to counteract the change. Much more serious than the direct and predictable effects of adding carbon dioxide to a stable system are the consequence of disturbing a system that is precariously balanced at the limits of stability. From control theory, and from physiology, we know that the perturbation of a system that is close to instability can lead to oscillations, chaotic change, or failure. Paradoxically, an animal close to death from exposure to cold, whose core temperature is below 25°C, will die if put into a warm bath. The well-intentioned attempt to restore heat succeeds only in warming the skin to the point where its oxygen consumption is greater than the slowly beating, still-cold heart and lungs can supply. In a vicious circle of positive feedback the blood vessels of the skin dilate; this so reduces blood pressure that death comes rapidly from the failure of the heart as a pump to circulate blood that is too depleted in oxygen for the system's needs. A hypothermic animal will recover if left to warm slowly, or if heat is supplied internally as by diathermy. We know too little about the carbon dioxide climate system to be able to provide a detailed forecast of the consequences of the current increase, but there are some solid facts of observation from which some general conclusions can be drawn. The Earth's mean temperature is well below the optimum temperature for plant life. There are periodic climatic oscillations as we cycle between the glaciations and their intermissions, and carbon dioxide is attenuated close to its lower possible limit. All these are physical signs of a system on the verge of failure. Like our latter-day physician, we find that diagnosis is easier than a cure. We are left with the uneasy feeling that to add carbon dioxide to the Earth now could be as unwise as warming the surface of our hypothetical hypothermic patient. It is not much comfort to know that, if we inadvertently precipitate a punctuation, life will go on in a new stable state. It is a near certainty that the new state will be less favorable for humans than the one we enjoy now. A Case of Acid Indigestion The greenhouse effect of carbon dioxide is not the only problem to arise from the burning of fossil fuels. In the northern temperate regions of the Earth there is an increased morbidity and mortality of the ecosystems. Trees, and the life in lakes and rivers, are particularly affected. The symptoms seem to be connected with an observed increase in the rate of deposition of acidic substances. Combustion is said to be the cause of acid deposition and of all the harm it does to forest ecosystems. Does geophysiology have any different view on this? It could be said that it is all the fault of oxygen. If those ancient godfathers, the cyanobacteria, had not polluted the Earth with this noxious gas there would be no oxides of nitrogen and of sulfur to trouble the air, and therefore no acid rain. Oxygen, the acid maker, the gaseous drug that both gives us life and kills us in the end, not for nothing did those French chemists of the eighteenth century call it the acidifying principle. In their time there were not many chemicals for them to experiment with; those they did have, such as sulfur, carbon, and phosphorus, all gave acids when combined with oxygen. It was only later, when the discovery of electricity allowed chemists to isolate elements like sodium and calcium, that combustion was found to produce alkalis as well. Later still, they realized that an acid was a substance that freely donated positively charged hydrogen atoms, and it was these protons that were the true principle of acidity. In addition that great chemist, G. N. Lewis, observed that it was the electric charge that mattered, not the atom that carried it. He showed that acids can be substances that attract electrons, the fundamental carriers of the negative charge. In some ways oxygen itself is one of these "Lewis" acids. It is not so surprising that there is free oxygen in the air from life's chemical transactions. The bundle of elements that form the chemicals that go to make up the Earth's crust have more oxygen than anything else; 49 percent of the elemental composition is oxygen. As Lavoisier observed, of all the principal light elements that go to make up living matter -- carbon, nitrogen, hydrogen, sulfur, and phosphorus -- only hydrogen does not give acids when combined with oxygen. Long before humans trod the planet, the rain that fell was acid. The natural acid in the rain were carbonic acid, the gentle acid of fizzy carbonated water; formic acid, one of the end products of methane oxidation; and nitric, sulfuric, methanesulfonic, and hydrochloric acids. Although the last four of these are strong and corrosive, the rain that fell did no harm, for the acids were present at great dilution. They came mostly from the oxidation of gases emitted by living things; some came also from the gases vented by volcanoes, or from high-energy processes, such as lightning and cosmic rays, that cause nitrogen and oxygen to react. The biological precursors of the acids -- for example methane, nitrous oxide, dimethyl sulfide, and methyl chloride -- are not acids, but they oxidize in the air to produce the catalog of acids listed above. Pollution by acid rain deposition is again a matter of dosage: pollution is due to an increase to intolerable levels of acids that previously were benign in their abundance. Quite separate from the demolition of ecosystems by acids and oxidants is the reduction of the quality of life by this kind of pollutant. The smog and haze that I complained of in the opening paragraphs of this chapter, and that masks so much of the Northern Hemisphere in summer, is for the most part a fog of sulfuric acid droplets. Any detached observer of the heated European or North American debate over acid rain might gather the impression that all acid rain was due to the burning of sulfur-rich fossil fuel in power stations, industrial furnaces, and domestic heating systems. Coal and oil both contain about one percent of sulfur. This element leaves the chimney stacks as sulfur dioxide gas, and soon this gas is oxidized to sulfuric acid which condenses as droplets that attract water vapor from the air to form an acid fog or haze. Eventually, this either settles out or is rained out. Where it falls on land that is rich in alkaline rocks like limestone, and particularly if there is a shortage of sulfur there, its fallout is welcome. But when it falls on land that is already acid, its addition is unwelcome and potentially destructive. Canada, Scandinavia, Scotland, and many other northern regions are on ancient rocks, the hard, soluble residue of eons of weathering. The ecosystems that survive on this unpromising, and often normally acidic, terrain have less capacity to resist the stress of acidification. It is from the countries of these regions that comes a justifiable complaint that their industrial neighbors are destroying them. To the Canadians and the Scandinavians it seems unarguable that the emission of sulfur dioxide by countries downwind should cease. Few can doubt the natural justice of their case, but naturally the offenders are reluctant to spend the very large sums needed to stop the escape of sulfur dioxide from their power stations and industries. The geophysiological contribution to this debate is to observe that this acid indigestion may have another source in addition to the sulfuric vinegar of neighbors. The fitting of sulfur dioxide removers to the chimneys might only alleviate, not cure, the problem. The neglected source of acid is the natural sulfur carrier, dimethyl sulfide. In the past two years, Meinrat Andreae and Peter Liss (ocean chemists based, respectively, in Florida and the United Kingdom) have shown that the emission of this gas from phytoplankton blooms at the surface of the oceans around western Europe is so large as to be comparable with the total emissions of sulfur from industry in this region. Moreover, the phytoplankton emissions are seasonal and seem to coincide with the maximum of acid deposition. It might be asked, with reason, that if this is the case, why was the pollution not observed until recently? If dimethyl sulfide from the sea is the source of sulfuric acid, then surely wouldn't Scandinavia always have suffered the ill effects of acid deposition? In fact, two changes in recent years may have made the natural transfer of sulfur from the sea to the land a curse instead of a benefit. Before Europe became intensively industrialized, dimethyl sulfide from the sea was probably carried far inland by the westerly wind drift, and slowly dropped its sulfur in dilute form over a vast area. Industrialization has not only increased the total burden of acid but also has greatly increased the abundance of oxides of nitrogen and other chemicals from combustion. In sunlight, these can react to make the powerful oxidant hydroxyl. Most important as a source of these agents is the internal combustion engine that powers personal and public transport. Hydroxyl radicals are now locally at least ten times more abundant than they used to be before private transport became ubiquitous. Because of this, dimethyl sulfide that used to oxidize slowly over all of Europe may now dump its burden of acid rapidly over the regions near the coast where the sea air encounters the polluted air. In addition to this increase in the rate of oxidation, and hence acid production, the output of dimethyl sulfide has itself probably increased in recent years. Patrick Holligan, of the Marine Biological Laboratory in Plymouth, tells me that satellite photographs have revealed dense algal blooms clustered around the outlets of the continental rivers of Europe. Peter Liss and his colleagues have found that these algal blooms emit dimethyl sulfide, apparently stimulated by the rich flow of nutrients down the rivers of Europe. The excessive use of nitrate fertilizer, and the increased output of sewage effluent into the rivers feeding the North Sea and the English Channel, have gone to overnourish the sea above the European continental shelf and to make it like a duck pond. The relative amount of acid from this source is not yet known. It might turn out to be insignificant. However, prudent legislators concerned over acid rain should urge their scientific advisers to investigate the relative importance of the various sources of acid. My personal sympathy is with those who ask for action on the basis that sulfur dioxide emissions are the prime culprit. I do wonder, though, what would happen if reducing these did not work. Would governments then have the will to tackle the very much more expensive acts, if these were the best way to prevent acid rain deposition, of sewage reform, or the control of nitrogen oxide emissions? The affair of acid rain is as much an issue of politics and economics as of environmental science. Before accepting as inevitable a long and costly battle involving national and commercial interests, it is useful to go back and re-examine the conduct of the ozone war. There are some interesting parallels and possibly some lessons to be learnt. The Dermatologists' Dilemma: Ozonemia In the late 1960s I developed a simple apparatus able to detect chlorofluorocarbons (CFCs) in the atmosphere down to parts per trillion by volume. This is an exquisite sensitivity; at such levels even the most toxic of chemicals could be breathed in or swallowed without harm, indefinitely. In 1972, I took this apparatus on the voyage to Antarctica and back of the RV Shackleton (see chapter 6). The measurements I made on that ship showed that the CFCs were distributed throughout the global environment. There was about 40 parts per trillion in the Southern Hemisphere and 50 to 70 in the Northern. When I reported these findings in a Nature paper in 1973, I was concerned that some enthusiast would use them as the basis of a doom story. As soon as numbers are attached to the presence of a substance, these numbers seem to confer a spurious significance. What previously was a mere trace becomes a potential hazard. The hypochondriac, on hearing that his blood pressure is 110/60, becomes worried: "Surely, doctor, isn't that too low?" As a putative planetary physician I felt the need to add at the beginning of my paper the sentence, "The presence of these compounds constitutes no conceivable hazard." This sentence has turned out to be one of my greatest blunders. Of course I should have said, "At their present level, these compounds constitute no conceivable hazard." Even then I knew that, if their emissions continued unchecked, they would accumulate until sometime near the end of the century they could be a hazard. I knew nothing of their threat to the ozone layer, but I did know that they were among the most potent of greenhouse gases and that by the time they reached the parts per billion level the climatic consequences of their presence could be serious. This opinion is recorded in the proceedings of a conference on fluorocarbons held at Andover, Massachusetts, in October 1972. At this time in the 1970s there was a fear of impending catastrophe. "Earth's fragile shield," the ozone layer, was said to be in imminent danger of demolition as a consequence of the release into the stratosphere of nitric oxide in the exhaust gases of supersonic aircraft. The atmospheric chemist Harold Johnson first alerted us to this particular threat. Then, tentatively at first, Ralph Cicerone and his colleague Richard Stolarski drew our attention to chlorine as an another danger to ozone. Then in 1974 there appeared in Nature a paper by Sherry Rowland and Mario Molina which argued with great clarity and force that the CFCs, as a result of stratospheric photochemistry, were a potent source of chlorine and hence a threat to ozone. This paper stands like a beacon, a natural successor to Rachel Carson's book Silent Spring. It heralded the start of the ozone war. In their enthusiasm with the science and the battle, scientists, somewhat uncharacteristically, convinced themselves and the public of the need for immediate action to ban the emission of CFCs. To me, wrong-footed by my earlier assertion that CFCs were harmless, it seemed to be a remote and hypothetical threat. But I was among a minority, and legislators in many parts of the world were persuaded to act precipitately and to enact legislation banning CFC gases as aerosol propellants. It is interesting to ask what is special about ozone that made legislators act this way. No one was dying of the effects of CFC emissions; crops and livestock were unharmed by their presence; the substances themselves were among the most benign of chemicals that enter our homes, neither toxic, corrosive, nor flammable. Indeed, they would have been imperceptible but for the sensitivity of the instrument that I used for their detection. Their presence at between 40 and 80 parts per trillion, even to the most committed environmentalist, was no threat to ozone. The concern came from the fact that the emissions were growing exponentially, and if the growth rate of the sixties continued until the end of the century, there would be an ozone depletion of between 20 and 30 percent. This would be disastrous. Ozone is a deep blue, explosive, and very poisonous gas. It is strange that so many have regarded it as if it were some beautiful endangered species. But it was the mood of the 1970s to respond to environmental hazards much as previous generations had responded to witchcraft. It was not easy to oppose the widely held belief that only immediate action by scientists and politicians could save us and our children from an otherwise ineluctable depletion of the ozone layer and the dire consequences of an ever-increasing flux of carcinogenic ultraviolet radiation. This was also the time when the word "chemical" became pejorative, and all products of the chemical industry were assumed to be bad unless proved harmless. In a more sensible environment, we might have regarded the predictions of doom in the next century due to a single industrial chemical as far fetched -- something to watch closely, but not something requiring immediate legislation. But the 1970s was not the time for a long, cool look at things. At a university in the small Rocky Mountain town of Logan, Utah, the principal scientists and lawyers concerned with the fluorocarbon affair met in 1976. Among those present were Ralph Cicerone, who had first hypothesized that chlorine in the stratosphere might catalyze the destruction of ozone, and Mario Molina and Sherry Rowland, who had developed the complex reaction sequence that explained how the CFCs could be the source of the chlorine and delineated the intricate details of the destruction mechanism. There were also scientists from industry and from the regulatory agencies, and there were, of course, lawyers and legislators. It could have been a reasoned debate leading to agreement about a safe upper limit for the CFCs in the light of current knowledge. It was instead a kind of tribal war council where the decision to fight was taken. Anyone who was not for the immediate banning of the CFCs was clearly a traitor to the cause. I shall never forget the adversarial encounter between Commissioner R. D. Pittle and Dr. Fred Kaufman, who was representing the National Academy of Sciences. The commissioner forgot he was not in a courtroom and demanded a yes or no answer to the question of whether CFCs should be banned. In certain ways it reminded me of another encounter, long ago: the one between Galileo and the authorities of his time. The processes of science are very different from those of the courtroom. Both have evolved to satisfy the needs of their practitioners. Scientific hypotheses are best tested by the accuracy of their predictions; the establishment of a fact of science does not greatly affect the Universe, only the wisdom of scientists. By contrast, facts in law are tested in an adversarial debate and established by judgment. The establishment of a legal fact alters society from then on. At the best of times, and even with near certainties, science and the law do not mix well. At Logan they tried to form legal judgments on plausible but untested scientific hypotheses. It is not so surprising that the result was of little credit to any of the participants. Once again the wisdom of Paracelsus that the poison is the dose was ignored, and in its place the "zero" shibboleth took charge. "There is no safe level of ultraviolet radiation," was the cry. "Ultraviolet, like other carcinogens, should be reduced to zero." In fact, ultraviolet radiation is part of our natural environment, and has been there as long as life itself. It is the nature of living things to be opportunistic. Ultraviolet, although potentially harmful, can also be used by living organisms for the photosynthesis of vitamin D. When it is a threat, it can be avoided by synthesizing such pigments as melanin to absorb it. There is still a lack of knowledge about the relationships between natural ecosystems and the ultraviolet to which they are exposed. But we do know that ultraviolet radiation varies sevenfold (700 percent) in intensity between the Arctic and the tropics, whereas visible light varies only 1.6 times (160 percent) over the same range of latitude. In spite of this large range of intensity, there is nowhere a region where the growth of vegetation is limited by ultraviolet. In contrast, a sevenfold change of rainfall makes the difference between forests and deserts. There are no ultraviolet deserts on Earth, and life seems well adapted to the radiation over this wide range of intensity. Damage does occur but seems to be limited to recent migrants from high to low latitudes. There is also evidence that a lack of ultraviolet can be harmful to migrants from the tropics to the temperate regions. Exposure to any radiation with a high quantum energy that penetrates the skin can damage the genetic material of our cells and corrupt their program of instructions. Among the adverse effects is the conversion from normal to malignant growth. This is frightening stuff, but we can keep our cool by remembering that these carcinogenic consequences are no different from those of breathing oxygen, which is also a carcinogen. Breathing oxygen may be what sets a limit to the life span of most animals, but not breathing it is even more rapidly lethal. There is a right level of oxygen, namely 21 percent; more or less than this can be harmful. To set a level of zero for oxygen in the interests of preventing cancer would be most unwise. Wars do not usually start from a single isolated incident, and so it was with the ozone war. The historical basis was, as mentioned in chapter 4, the proposal by Berkner and Marshall that the colonization of the land surfaces of the Earth did not take place until oxygen and its allotrope, ozone, first entered the atmosphere. Ozone, they said, prevents the penetration of hard ultraviolet radiation that otherwise would keep the land sterilized and uninhabitable by life. This was a decent scientific hypothesis and a very testable one at that. Indeed it was tested by my colleague Lynn Margulis, who challenged it by showing that photosynthetic algae could survive exposure to ultraviolet radiation equivalent in intensity to that of sunlight unfiltered by the atmosphere. But this did not stop the hypothesis from becoming one of the truly great scientific myths of the century; it is almost certainly untrue, and it survives only because of the apartheid that separates the sciences. Physical scientists regard biology as extraterritorial and biologists reciprocate. The members of each discipline tend to accept uncritically the conclusions of the other. This apartheid is a triumph of expertise over science, and it is expressed with great innocence when scientists try to explain the separation of their findings into physical and biological parts as a necessary consequence of expertise. Biologists concerned with the effects of ultraviolet know it to be beneficial as well as harmful. But until recently they had no reason to doubt the expertise of their physical science colleagues, and therefore thought only of the consequences of ozone depletion. As a counterpoint, most physical scientists are unaware that ultraviolet might in any way have benefits. Consequently, they tend to think of ozone accretion as a benefice. However, the diseases of vitamin D deficiency -- rickets and osteomalacia -- are associated with a reduced exposure to solar ultraviolet. Also it seems that the incidence of multiple sclerosis varies with latitude reciprocally to that of skin cancer. The variation of skin color with latitude suggests that we have, in the absence of migration, adapted to the ultraviolet levels of our habitats. Once more ozone is news. J. C. Farman and B. G. Gardiner, of the British Antarctic Survey, have discovered a thinning of the ozone layer over the south polar regions, moreover a thinning that has grown rapidly each year until now it is almost a hole. This event is entirely unexpected and in great contrast to the fact that over most of the world the level of ozone is either unchanged or even slightly increased. But this is exciting and fearful stuff. What if the hole should spread and threaten populated regions? Before we become too deeply involved, it seems worth asking what were the benefits of the first ozone conflict? Who won and who lost? The only clear losers were those small industries, and their employees, dependent upon the use of CFCs in the products that were banned. For various and complex reasons, the manufacturers of CFCs were not much affected. The loss of the doubtfully profitable CFC-propellant section of their market, together with the rationalization of their industry, did little to change their economy. Politicians and the environmental movement lost some of their credibility, but public memory tends to be short. The clear winners were science and the scientists. Vast sums have been disbursed for atmospheric research, which would never have been available but for the ozone war. We now know much more about our atmosphere, and this knowledge will be essential in the understanding of other atmospheric problems. Among them is the greenhouse warming effect of minor atmospheric gases. Three key properties of the CFCs make them dangerous. First is their long atmospheric life times, which allow them to accumulate unchecked, second their ability to carry their burden of chlorine directly and without loss to the stratosphere, and third the intensity with which they absorb long-wavelength infrared radiation. Their presence in the atmosphere adds to the carbon dioxide greenhouse effect. This is a danger that is potentially more serious than that of ozone depletion. We have reason to be glad that one of the pioneers of the original concern about CFCs, Ralph Cicerone, has turned his attention to the graver and more certain dangers of their greenhouse effect. It may turn out that I was very wrong to have opposed those who sought instant legislation to stop the emission of CFCs. I regard the strange phenomenon over the south polar regions as a warning of other more serious surprises yet to come. It seems possible that other changes, including the concomitant increase of CO2 and methane from human industry and agriculture, are responsible for the extra effect of chlorine compounds in polar regions, but there is little doubt in my mind that without the chlorine from industrial gases there would be no thinning of the ozone layer at the South Pole. The CFCs and other industrial halocarbons have increased by 500 percent since I first measured them in 1971. They were harmless then, but now there is too much halocarbon gas in the air. The first symptoms of poisoning are now felt. I now join with those who would regulate the emissions of the CFCs and other carriers of chlorine to the stratosphere. To return to our clinical analogy, we could say that the fear of skin cancer as a consequence of ozone depletion led at first to a global hypochondria -- something all too easily acquired by identifying our fears with the plausible account of symptoms described in a textbook. Good physicians know that hypochondria can be a cry for help and mask the existence of a real malady; perhaps the same is true of the global state of health. Could fears about the CFCs and the ozone layer have presaged discovery of the ozone hole and the climate-threatening greenhouse effect of CFCs? A Dose of Nuclear Radiation Carl Sagan once observed that if an alien astronomer were to look at the Solar System in the radio-frequency part of the spectrum, it would see a truly remarkable object. Two stars eclipsing one another: one of them a normal, small, main-sequence star and the other a very small, but intensely luminous body with an apparent surface temperature of millions of degrees, our Earth. Were that distant observer a scientist, it might speculate on the nature of the energy source that powered, what seemed to be, one of the hottest objects in the Galaxy. I wonder how high on the list of probable sources it would place chemical energy. Would it include energy coming from the reaction between fossil fuels and oxygen from plants? It is easy to ignore the fact that we are the anomalous ones. The natural energy of the Universe, the power that lights the stars in the sky, is nuclear. Chemical energy, wind, and water wheels: such sources of energy are, from the viewpoint of a manager of the Universe, almost as rare as a coal-burning star. If this is so, and if God's Universe is nuclear-powered, why then are so many of us prepared to march in protest against its use to provide us with electricity? Fear feeds on ignorance, and a great niche was opened for fear when science became incomprehensible to those who were not its practitioners. When X rays and nuclear phenomena were discovered at the end of the last century, they were seen as great benefits to medicine -- the near-magic sight of the living skeleton and the first means to palliate, even sometimes cure, cancer. Roentgen, Becquerel, and the Curies are remembered with affection for the good their discoveries did. Sure enough, there was a dark side also, and too much radiation is a slow and nasty poison. But even water can kill if too much is taken. It is usually assumed that the change in attitude towards radiation came from our revulsion at that first misuse of nuclear energy at Hiroshima and Nagasaki. But it is not that simple. I well remember how the first nuclear power stations were a source of national pride as they quietly delivered their benefice of energy without the vast pollution of the coal burners they replaced. There was a long spell of innocence between the end of the Second World War and the start of the protest movements of the 1960s. So what went wrong? Nothing really went wrong, it just happens that nuclear radiation, pesticides, and ozone depleters share in common the property that they are easily measured and monitored. The attachment of a number to anything or anyone bestows a significance that previously was missing. Sometimes, as with a telephone number, it is real and valuable. But some observations -- for example, that the atmospheric abundance of perfluoromethyl cyclohexane is 5.6 x 10-15, or that as you read this line of text at least one hundred thousand of the atoms within you will have disintegrated -- while scientifically interesting, neither confer benefit nor have significance for your health. They are of no concern to the public. But once numbers are attached to an environmental property the means will soon be found to justify their recording, and before long a data bank of information about the distribution of substance X or radiation Y will exist. It is a small step to compare the contents of different data banks and, in the nature of statistical distributions, there will be a correlation between the distribution of substance X and the incidence of the disease Z. It is no exaggeration to observe that once some curious investigator pries open such a niche, it will be filled by the opportunistic growth of hungry professionals and their predators. A new subset of society will be occupied in the business of monitoring substance X and disease Z, to say nothing of those who make the instruments to do it. Then there will be the lawyers who make the legislation for the bureaucrats to administer, and so on. Consider the size and intricacy of the radiation-monitoring agencies, of the industry that builds monitoring and protective devices, and of the academic community that has radiation biology as its subject. If the strong public fear of radiation were dispelled, it would not be helpful to their continued employment. We see that there is a very biological, Gaian, feedback in our community relationship with the environment. It is not a conspiracy or a selfishly motivated activity. Nothing like that is needed to maintain the ceaseless curiosity of explorers and investigators, and there are always opportunists waiting to feed on their discoveries. If this alone were not enough, there are the media, ready to entertain us. They have in the nuclear industry a permanent soap opera that costs them nothing. Why, we can even experience the excitement of a real disaster, like Chernobyl, but in which, as in fiction, only a few heroes died. It is true that calculations have been made of the cancer deaths across Europe that might come from Chernobyl, but if we were consistent, we might wonder also about the cancer deaths from breathing the coal smoke smogs of London and look on a piece of coal with the same fear now reserved for uranium. How different is the fear of death from nuclear accidents from the commonplace and boring death toll of the roads, of cigarette smoking, or of mining -- which when taken together are equivalent to thousands of Chernobyls a day. It was Rachel Carson, with her timely and seminal book, Silent Spring, who started the Green Movement and made us aware of the damage we can so easily do to the world around us. But I do not think that she could have made her case against pesticide poisoning without the prior discovery that agricultural pesticides were distributed ubiquitously throughout the whole biosphere. Numbers could even be attached to the wholly insignificant quantities of pesticide in the milk of nursing mothers or in the fat of penguins in the Antarctic. In Rachel Carson's time, pesticides were a real threat, and the blind exponential increase of their use put all our futures in hazard. But we have responded in a fashion, and that one experience ought not be extrapolated to all environment hazards real or imagined. The foregoing paragraphs are not intended as support for the nuclear industry, nor to imply that I am enamoured of nuclear power. My concern is that the hype about it, both for and against, diverts us from the real and serious problem of living in harmony with ourselves and the rest of the biota. I am far from being an uncritical supporter of nuclear power. I often have a nightmare vision of the invention of a simple, lightweight nuclear fusion power source. It would be a small box, about the size of a telephone directory, with four ordinary electricity outlets embedded in its surface. The box would breathe in air and extract, from its content of moisture, hydrogen that would fuel a miniature nuclear fusion power source rated to supply a maximum of 100 kilowatts. It would be cheap, reliable, manufactured in Japan, and available everywhere. It would be the perfect, clean, safe power source; no nuclear waste nor radiation would escape from it, and it could never fail dangerously. Life could be transformed. Free power for domestic use; no one need ever again be cold in winter or overheated in the summer. Simple, elegant pollution-free private transport would be available to everyone. We could colonize the planets and maybe even move on to explore the star systems of our Galaxy. That is how it might be sold, but the reality almost certainly is ominously expressed by Lord Acton's famous dictum, "Power tends to corrupt and absolute power corrupts absolutely." He was thinking of political power, but it could be just as true of electricity. Already we are displacing the habitats of our partners in Gaia with agricultural monocultures powered by cheap fossil fuel. We do it faster than we can think about the consequences. Just imagine what could happen with unlimited free power. If we cannot disinvent nuclear power, I hope that it stays as it is. The power sources are vast and slow to be built, and the low cost of the power itself is offset by the size of the capital investment required. Public fears, unreasoning though they sometimes are, act as an effective negative feedback on unbridled growth. No one, thank God, can invent a chain saw driven by a nuclear fission power source that could cut a forest as fast and heedlessly as now we cut down a tree. To my ecologist friends, many of whom have been at the sharp end of protest against nuclear power, these views must seem like a betrayal. In fact, I have never regarded nuclear radiation or nuclear power as anything other than a normal and inevitable part of the environment. Our prokaryotic forebears evolved on a planet-sized lump of fallout from a star-sized nuclear explosion, a supernova that synthesized the elements that go to make our planet and ourselves. That we are not the first species to experiment with nuclear reactors has been touched on earlier in this book. I am indebted to Dr. Thomas of Oak Ridge Associated Universities, who gave me a new insight on the nature of the biological consequences of nuclear radiation. As I listened to his words, spoken in the quiet privacy of his room, I felt an emotion like that described by Keats in his verses about first reading Chapman's Homer. What Dr. Thomas said may have been no more than hypothetical, but to me it was exciting stuff. Let's look at his proposition: "Suppose that the biological effects of exposure to nuclear radiation are no different from those of breathing oxygen." We have long known that the agents within the living cell that do damage after the passage of an X-ray photon, or a fast-moving atomic fragment, are an assortment of broken chemicals; things called free radicals that are reactive and destructive chemicals. As an X-ray photon passes through the cell, the radiation severs chemical bonds just as a bullet might sever blood vessels and nerves. By far the greater part of this destruction is of molecules of water, for they are the most abundant in living matter. The broken pieces of a water molecule form, in the presence of oxygen, a suite of destructive products including the hydrogen and hydroxyl radicals, the superoxide ion, and hydrogen peroxide. These are all capable of damaging, irreversibly, the genetic polymers that are the instructions of the cell. This is now conventional scientific wisdom; the novel insight from Dr. Thomas was to remind us that these same destructive chemicals are being made all the time, in the absence of radiation, by small inefficiencies in the normal process of oxidative metabolism. In other words, so far as our cells are concerned, damage by nuclear radiation and damage by breathing oxygen are almost indistinguishable. The special value of this hypothesis is that it suggests a rule of thumb for comparing these two damaging properties of the environment. If Dr. Thomas were right, then the damage done by breathing is equivalent to a whole body radiation dose of approximately 100 roentgens per year. I used to wonder about the risk-benefit ratio of a medical X-ray examination. A typical hospital X ray of the chest or abdomen could deliver 0.1 roentgen of radiation, enough to blacken the film of a personal radiation monitor and to have caused terror to the inhabitants of Three Mile Island. Now, thanks to Dr. Thomas, I look upon it as no more than one-thousandth of the effect of breathing for a year. Or to put it another way, breathing is fifty times more dangerous than the sum total of radiation we normally receive from all sources. The early battles at the end of the Archean against the planet-wide pollution by oxygen are still apparently with us. Living systems have invented ingenious countermeasures: antioxidants such as vitamin E to remove the hydroxyl radicals, superoxide dismutase to destroy the superoxide ion, catalase to inactivate hydrogen peroxide, and numerous other means to lessen the destructive effects of breathing. Nevertheless, it seems likely that the life span of most animals is set by a fixed upper limit of the quantity of oxygen that their cells can use before suffering irreversible damage. Small animals such as mice have a specific rate of metabolism much greater than we do; that is why they live only a year or so even if protected from predation and disease. Oxygen kills just as nuclear radiation does, by destroying the instructions within our cells about reproduction and repair. Oxygen is thus a mutagen and a carcinogen, and breathing it sets the limit of our life span. But oxygen also opened to life a vast range of opportunities that were denied to the lowly anoxic world. To mention just one of these: free molecular oxygen is needed for the biosynthesis of those special structure-building amino acids, hydroxylysine and hydroxyproline. From these are made the structural components that made possible the trees and animals. Paul Crutzen, an atmospheric chemist, was the first to draw our attention to the far-reaching geophysiological consequences of a major nuclear war, the "nuclear winter." We need to be reminded, often, just how bad that ultimate sanction can be so that it remains a deterrent. But, like oxygen, nuclear energy provides opportunities and challenges us to learn to live with it. The Real Malady When things are bad, or if we witness some particularly depressing piece of environmental demolition, we often say that people are like a cancer on the planet; they grow in numbers unchecked and they destroy all that comes in contact with them. Was it fear of cancer, that great standby of all environmentalist demagogues, that stirred our worries about the Earth? If it was, we can cease worrying on that account. Life exists in many forms, and of these, neither organisms living as single cells nor Gaia suffer the unique rebellion of cancer. That is limited to the metaphyta and metazoa -- those life forms, such as trees and horses, that consist of vast but intensely organized cell communities. People are not in any way like a tumor. Malignant growth in an animal requires the transformation of instructions encoded in the genes of a cell. The descendants of the transformed cell then grow independently of the animal system. The independence is never complete; the cancerous cells still, to some extent, respond and contribute to the system. To be like a cancer we should need first to become a different species and then to be a part of something far more intensively organized than Gaia. The longevity and strength of Gaia comes from the informality of the association of her constituent ecosystems and species. She operated for nearly a third of her life populated with no more than prokaryotic bacteria. She still is largely run by these, the most primitive part of life on Earth. The consequences for Gaia of the environmental changes that we have made are as nothing compared with those that you or I would experience from unfettered growth of a community of malignant cells. Although Gaia may be immune to the eccentricities of some wayward species like us or the oxygen bearers, this does not mean that we as a species are also protected from the consequences of our collective folly. When I wrote the first Gaia book, nearly ten years ago, it seemed that there might be critical ecosystems whose damage or removal might have serious consequences for the present collection of organisms which inhabit the Earth and find it comfortable. The forests of the humid tropics and the ecosystems of the waters of the continental shelves seemed at that time to be those most likely to be crucial for keeping the environmental status quo. Already we see the beginnings of malfunction, in the form of rain that is too acid as a consequence of the proliferation of algae in the overnourished waters off the European coast. Also, the general decline of the ecosystems in several parts of Africa may be a consequence of removing the trees that once grew there. The maladies of Gaia do not last long in terms of her life span. Anything that makes the world uncomfortable to live in tends to induce the evolution of those species that can achieve a new and more comfortable environment. It follows that, if the world is made unfit by what we do, there is the probability of a change in regime to one that will be better for life but not necessarily better for us. In the past, changes of this kind, like the jump from a glaciation to an interglacial, have tended to be revolutionary punctuations rather than gradual evolutions. The things we do to the planet are not offensive nor do they pose a geophysiological threat, unless we do them on a large enough scale. If there were only 500 million people on Earth, almost nothing that we are now doing to the environment would perturb Gaia. Unfortunately for our freedom of action, we are moving towards eight billion people with more than ten billion sheep and cattle, and six billion poultry. We use much of the productive soil to grow a very limited range of crop plants, and process far too much of this food inefficiently through cattle. Moreover, our capacity to modify the environment is greatly increased by the use of fertilizers, ecocidal chemicals, and earth-moving and tree-cutting machinery. When all this is taken into account we are indeed in danger of changing the Earth away from the comfortable state it was once in. It is not just a matter of population; dense population in the northern temperate regions may be less a perturbation than in the humid tropics. There is no way for us to survive without agriculture, but there seems to be a vast difference between good and bad farming. Bad farming is probably the greatest threat to Gaia's health. We use close to 75 percent of the fertile land of the temperate and tropical regions for agriculture. To my mind this is the largest and most irreversible geophysiological change that we have made. Could we use this land to feed us and yet sustain its climatic and chemical geophysiological roles? Could trees provide us with our needs and still serve to keep the tropics wet with rain? Could our crops serve to pump carbon dioxide as well as the natural ecosystems they replace? It should be possible, but not without a drastic change of heart and habits. I wonder if our great-grandchildren will be vegetarian and if cattle will live only in zoos and in tame life parks. As understanding about the dangers inherent in farming grows, it reinforces the insight from conventional modeling. Thus large-scale changes of land use, even in one region alone, will not be limited in their effects to that region only. Geophysiology also reminds us that the climatic effects of forest clearance are likely to be additive to those of carbon dioxide and other greenhouse gases. Even the most intricate climate models of the present type cannot predict the consequences of these changes. A complete model requires the biota to be included in a way that recognizes its very active presence and its preference for a narrow range of environmental variables. Putting the biota in a box with inputs and outputs, as in a biogeochemical model, does not do this. By analogy, we need physiology to understand how we sustain a constant personal temperature when exposed to heat or cold, biochemistry can only tell us what reactions produce heat in our bodies, not how we regulate our temperature. There is as yet no answer as to what proportion of the land of a region can be developed as open farmland or forest without significantly perturbing either the local or the global environment. It is like asking what proportion of the skin can be burnt without causing death. This physiological question has been answered by the direct observations of the consequences of accidental burns. It has not been modeled, so far as I am aware. It may be that detailed geophysiological modeling can answer the parallel environmental question, but, if human physiology is a guide, empirical conclusions drawn from a close study of the local climatic consequences of regional changes of land use are more likely to yield the information we seek. In some ways the ecosystem of, for example, a forest in the humid tropics is like a human colony in Antarctica or on the Moon. It is only self-supporting to a limited extent, and its continued existence depends upon the transport of nutrients and other essential ingredients from other parts of the world. At the same time, ecosystems and colonies try to minimize their losses by conserving water, heat, or essential nutrients; to this extent they are self-regulating. The tropical rain forest is well known to keep wet by modifying its environment so as to favor rainfall. Traditional ecology has tended to consider ecosystems in isolation. Geophysiology reminds us that all ecosystems are interconnected. As an analogy, an animal's liver has some capacity to regulate its internal environment, and the cells of the liver can be grown in isolation. But neither the animal without a liver, nor the liver itself, can live independently alone; each depends upon the interconnection between the two. We do not know if there are vital ecosystems on the Earth, although it would be difficult to imagine life continuing without the ubiquitous presence of those ancient bacteria who live in the dark and smelly places of mud and feces. Those bacteria found, 3.5 eons ago, that the perfect way of life for them was turning used carbon into methane gas, and they have done it ever since. The ecosystems of the waters of the continental shelves transfer essential elements like sulfur and iodine from the sea to the air and hence to the land. The forests of the humid tropics act on a global scale by pumping vast volumes of water back into the air (evapotranspiration); this has the potential to affect climate locally by causing the condensation of clouds. The white tops of the clouds reflect away the sunlight that otherwise would heat and dry the region. The evaporation of water from the liquid state absorbs a great deal of heat, and the climate of distant regions outside the tropics is considerably warmed when damp tropical air masses release their latent heat in the condensation of rain. The transfer of nutrients and the products of weathering by the tropical rivers are obviously part of their interconnection and must also have a global significance. If evapotranspiration, or the additions of the tropical rivers to the oceans, is vital to the maintenance of the present planetary homeostasis, then this suggests that its replacement with an agricultural surrogate or a desert not only would deny those regions to their surviving inhabitants but would threaten the rest of the system as well. We do not yet know; we can only guess that tropical forest systems are vital for the world ecology. It may be that they are like the temperate forests that seem to be expendable without serious harm to the system as a whole; temperate forests have suffered extensive destruction during glaciations as well as during the recent expansion of agriculture. It would seem, therefore, that the traditional ecological approach of examining the forest ecosystem in isolation is as important to our understanding as is the consideration of its interdependence with the whole system. Geophysiology is at the information-gathering stage, rather as was biology when Victorian scientists went forth to distant jungles to collect specimens. We do recognize the needs of the Earth, even if our response time is slow. We can be altruistic and selfish simultaneously in a kind of unconscious enlightened self-interest. We most certainly are not a cancer of the Earth, nor is the Earth some mechanical contraption needing the services of a mechanic. If it turns out that Gaia theory provides a fair description of the Earth's operating system, then most assuredly we have been visiting the wrong specialists for the diagnosis and cure of our global ills. These are the questions that must be answered: How stable is the present system? What will perturb it? Can the effects of perturbation be reversed? Without the natural ecosystems in their present form, can the world maintain its present climate and composition? These are all within the province of geophysiology. We need a general practitioner of planetary medicine. Is there a doctor out there?
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