Earth System Science: Gaia and the human impact

Today I want first to congratulate you on your centenary. I feel honoured to mark the occasion by giving the first in your new series of T. H. Huxley Lectures. You have described T. H. Huxley as the founding father of your work on biology and earth science. Today I want to focus on the combination of the two which is earth system science.

Earth system science is very old and very new. It goes back to before science as such was defined, and goes forward to examine how the physical and living elements on the surface of the Earth combine.

That surface is wafer thin. Everything in and on it connects, and cannot be understood except as parts of an integrated system. This unity has been recognized from the earliest days of human observation.

Indeed it was the stuff of religion. Gods and goddesses were seen to embody specific elements, ranging from the sky to the most local spring, and the notion that the Earth itself was alive came up regularly in Greek philosophy. Leonardo da Vinci saw the human body as the microcosm of the Earth, and the Earth as the macrocosm of the human body. He did not know as well as we now do that the human body is itself a macrocosm of tiny elements of life - bacteria, parasites, viruses - often at war with each other, and together constituting more than half our body cells.

Bruno was burnt at the stake just over 400 years ago for maintaining that the Earth was indeed alive, and that other planets could be so too. The geologist James Hutton saw the Earth as a self-regulating system in 1785, and T. H. Huxley saw it likewise in 1877. Vernadsky (1863-1945) saw the functioning of the biosphere as a geological force, moving, processing and recycling billions of tons of surface material every year. This created a disequilibrium which in turn promoted the evolution and diversity of life.

But it was James Lovelock who brought this all together into the Gaia hypothesis. It arose from his observation that the vital difference between the Earth and Mars was the chemical instability of the Earth's atmosphere, and that this instability was nonetheless constant within limits over billions of years. What established those limits? The answer was the role of living organisms, originally bacteria and later algae, operating through photosynthesis to help regulate the environment on the Earth's surface. In short there was a dynamic relationship between the physical and biological elements, each contributing to the other, a sort of symbiosis most clearly identifiable when seen from space.

Looking back it is strange how uncongenial the observation was to the practitioners of the conventional wisdom, particularly biologists, when it was put forward in its present form over a quarter of a century ago. Unfamiliar ways of looking at the familiar, or any rearrangement of the intellectual furniture, tend to arouse emotional opposition beyond rational argument: thus opposition to the idea of evolution by natural selection, of continental drift and tectonic plate movement, and more recently of cometary or asteroid impacts from space.

Gaia theory challenges current habits of reductionism, and the tendency of some to put their subjects into boxes, shut the lid, and ignore what is going on in other boxes. Most of us are better at looking at the constituent elements of problems than in seeing the connections between them and understanding how the resulting system works.

What is in a name? I remember a conversation with a distinguished scientist keen to rubbish "all that Gaia nonsense". When I protested and offered to rename it 'geophysiology', 'earth systems science' or something similar, he brightened up and eventually confessed that "most of it must be right".

The choice of the Greek goddess Gaia rather than of some Greek-derived scientific polysyllable, or worse some acronym, was a risk. On the one hand it was just too attractive for those in search of a new religion at a time when traditional religions were breaking down; on the other it was just too repulsive for those who liked to hide their science in coded vocabulary. The result was that some New Age travellers jumped aboard, and some otherwise sensible scientists jumped off. This is probably still the case. But as a theory, Gaia is now winning.

This has been well demonstrated by the remarkable success of James Lovelock's book The Revenge of Gaia in 2006. There he responded to some of the criticisms which had been made, particularly over the mechanisms by which Gaia, or the Earth System, regulates itself within broad limits. Those limits are of course constantly changing. Over the 3.8 billion years of life on Earth, Gaia has survived the great extinctions from outside the Earth, and the great catastrophes from within it. This has required a remarkable resilience whereby physical and biological mechanisms have adapted to new circumstances. Gaia is a lady who has remained broadly the same underneath, but can wear many clothes for many weathers and many fashions.

The problem is to establish how she does it, or more precisely, how individual organisms, evolving by natural selection on Darwinian principles, can combine with geological and other forces to bring about self regulation within limits which have never yet been breached. It was Lynn Margulis who described Gaia as "a tough bitch". So she is, fortunately for all living organisms, including ourselves.

One answer to the problem lay in the elaboration of models know as Daisyworld. In James Lovelock's own words:

"Daisyworld models a planet like the Earth, orbiting a star like our sun. On Daisyworld there are only the two plant species, and they both compete for living space as any plants would do. When the sun is younger and cooler, so is the model planet, and at that time the dark daisies flourish. Only at the hottest places near the equator are light daisies found. This is because dark daisies absorb sunlight and keep themselves, their region and the whole planet warm. As the star heats up, the dark daisies living in the tropics are displaced by light daisies, because the light ones reflect sunlight and so are cooler; they also cool their region and the whole planet. As the star continues to warm, the light daisies displace the dark, and through their competition for space the planet always stays near to the ideal temperature for life. Eventually, the star grows so hot that even light daisies can no longer survive and the planet becomes a lifeless ball of rock."

which of course it will eventually become.

This model was later improved on when ocean algal ecosystems were substituted for daisies, and work was begun to show in practical terms how self regulation actually worked.

The position was set out in a remarkable Declaration on Global Change following the Amsterdam conference of the four great international global research programmes in July 2001. The key sentence was:

"the Earth System behaves as a single, self-regulating system, comprised of physical, chemical, biological and human components. The interactions and feedbacks between the component parts are complex and exhibit multi-scale temporal and spatial variability."

This established - if it were necessary - that Gaia had at last moved from the fringe to the centre of Earth science.

Let us turn now to the human impact. Gaia has no particular tenderness for humans. We are no more than a small, albeit immodest, part of her. Only in the last tick of the clock of geological time did humans make their appearance, and only in the last fraction of it did they make any impact on the Earth system as a whole.

But that impact has been enormous. A periodical visitor from outer space would find more change in the last 200 years than in the preceding 2000, and more change in the last 20 years than in the preceding 200. The association between humans and their environment, including the micro-world in and around them, has changed at every change of human evolution: from vegetarians to meat eaters, from hunter gatherers to farmers, and from country to city dwellers.

But the most radical divide was the beginning of the industrial revolution in Britain some 250 years ago. Before then the effects of human activity were local, or at worse regional, rather than global. All the civilizations of the past cleared land for cultivation, introduced plants and animals from elsewhere, and caused a variety of changes. I should add that many of them collapsed for this and other reasons. But current changes are in a different category.

The eminent biologist E. O. Wilson has laid out some of these changes in his new book The Creation. In his words:

"We have, all by our bipedal, wobbly-headed selves, altered Earth's atmosphere and climate away from the norm. We have spread thousands of toxic chemicals worldwide, appropriated 40 percent of the solar energy available for photosynthesis, converted almost all of the easily arable land, dammed most of the rivers, raised the planet sea level, and now, in a manner likely to get everyone's attention like nothing else before it, we are close to running out of fresh water. A collateral effect of all this genetic activity is the continuing extinction of wild ecosystems, along with the species that compose them. This also happened to be the only human impact that is irreversible."

There has been some talk, notably among the religiously inclined about an alleged human obligation of 'stewardship' of the Earth. If so, the Earth has had to wait a long time for the arrival of the stewards. Certainly the trilobites managed for over 250 million years without them. Looking at the human record of predation, exploitation and extinction of other forms of life since the current version of hominins appeared less that 150,000 years ago, I am reminded of James Lovelock's remark that "humans are about as qualified as stewards of the earth, as goats are to be gardeners."

More specifically there are six main ways in which humans are affecting the Earth system. First there has been a giddy making increase in the numbers of one animal species: our own. There were around 1 billion of us at the time of Thomas Malthus at the end of the 18th century, then two billion in 1930 and over 6 billion now. The world population is increasing by over 80 million people each year. More than half our species now lives in cities, which are themselves like organisms drawing in resources and emitting wastes.

In short we are spreading like dandelions, or any other species on a bonanza. Indeed it has been suggested that human multiplication is a case of malignant maladaptation in which a species, like infected tissue in an organism, multiplies out of control, affecting everything else. In terms of factors of increase in the last century, air pollution rose by around 5, water use by 9, sulphur emissions by 13, energy use by 16, carbon dioxide emissions by 17, and industrial output by 40.

All this has profoundly affected the condition of the land surface. More people need more space and more resources. Soil degradation is currently estimated to affect some 10 percent of the world's current agricultural area. Although more and more land, whatever its quality, is used for human purposes, increase in food supplies has scarcely kept pace with increase in population. Today many of the problems are of distribution. But even countries generating food surpluses can see limits ahead. Application of bio-technology, itself with some dubious aspects, can never hope to meet likely shortfalls.

In the meantime industrial contamination of various kinds has greatly increased. To run our complex societies, we need copious amounts of energy, at present overwhelmingly derived from dwindling resources of fossil fuels laid down hundreds of millions of years ago. To illustrate this point, it took around 200 million years to lay down the coal, oil and gas on which our present society depends. We are consuming them over a period of around 200 years. Thus each single year we consume a million tons of fossil fuel deposit. We also have to deal with the consequences for the atmosphere, together with the mounting problems of waste disposal, including the toxic products of industry.

Next there has been increasing pollution of water, both salt and fresh. No resource is in greater demand than fresh water. At present such demand doubles every 21 years and seems to be accelerating. Yet supply in a world of over 6 billion people is the same as at the time of the Roman Empire in a world of little more than 300 million people. We are at present using some 160 billion tonnes more water every year than is replenished.

Then there have been changes in the chemistry of the atmosphere. Acidification from industry has affected wide areas downwind. There has been some depletion of the protective atmospheric ozone layer permitting more ultra-violet radiation to reach the surface of the Earth with so far unmeasured effects on organisms unused to it. This is an encouraging story. This year is the 20th anniversary of the Montreal Protocol in which global measures were taken to cope with this unexpected problem.

Climate change is much more serious and much more difficult. Greenhouse gases are increasing at a rate which could change average world temperature, with big resulting variations in climate and local weather as well as sea levels. Global dimming caused by pollution is another factor. According to the estimates of the Intergovernmental Panel on Climate Change, we could be altering the global climate at rates far greater than would have occurred naturally in the last ten thousand years with unforeseeable consequences. Carbon levels in the atmosphere are now the highest in the last 650,000 years, and rising fast.

Next as E. O. Wilson has pointed out, humans are causing extinction of other organisms at many times the normal rate. Indeed the rate of extinction is reminiscent of the dinosaur extinction of 65 million years ago. The rising damage to the natural services on which we, like all species depend, is immeasurable. There is no conceivable substitute for such services. At present there is a creeping impoverishment of the biosphere.

Lastly comes the still uncertain consequences of technology. Recently Lord Rees the current President of the Royal Society looked at the possible result of inadvertence, criminality, use of exotic weapons, nanotechnology, and excessive dependence on technology, and concluded that the chances of our civilization surviving this century were no more than 50 percent.

Change rarely proceeds in curves. It goes in steps and thresholds. Due perhaps to the shortness of our individual lives and our lack of imagination we tend to believe that what we know - the current diversity of life and the climate around us - will only change within narrow limits; and that if nature is allowed to take its course, things will revert to where they were. Unfortunately history gives no foundation for this belief. As was well said in the Amsterdam Declaration of July 2001.

"the nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change are unprecedented. The Earth is currently operating in a no-analogue state."

I repeat that Gaia has no special tenderness for our species. But we certainly need to have more tenderness for Gaia.

This raises fundamental questions of values. Some, fortunately not all of us, tend to believe that greater material prosperity and welfare are overriding human priorities, that resources can be indefinitely exploited, and that economic growth on the traditional definition is good in itself: in short ever upwards and onwards with freer markets, freer trade and continuously rising consumption. This is the philosophy of many economists and of most politicians, at least until recently. Last month even the US Secretary of State said (quoted in the Financial Times of 12 October 2007):

"If we stay on our present path, we face an unacceptable choice: either we sacrifice global economic growth to secure the health of our planet, or we sacrifice the health of our planet to continue with fossil fuelled growth."

Unfortunately there are still many, particularly in the United States, who see technology as the ultimate fix for whatever problems may arise. For example there is more talk about new energy technologies than about how to reduce consumption of energy and to use it more efficiently.

There is an accompanying spread of the culture of rising expectations, nourished by world wide use of information technology through radio, television, email, the internet and the press. One consequence is a drive towards industrialization as a synonym for 'development', and the catch-all answer to the world's manifest ills. With it has come globalization and an increasing homogenisation of human culture, and a widening gap between rich and sophisticated on one hand, and poor and unsophisticated on the other. As has been well said, globalization represents a kind of mutation in human civilization.

Another consequence is change in evolution itself. Human activity is changing the processes of natural selection, mutation and symbiosis, not just through genetic engineering and modification of organisms, but also through large scale extinction of species and the ecosystems in which they have a place. We have yet to see whether there is any realistic prospect of developing a subspecies of super-humans with genes tailored to specific requirements, but it is certainly not impossible in the long future.

In his fantasy The Time Machine of 1898, H. G. Wells foresaw a genetic division of humanity into Eloi (or upper worlders) and Morlocks (or lower worlders) in perpetual struggle against each other. Of course Gaia was still there, but, so far as humans were concerned, it was not a Gaia we would happily recognize.

In fact human damage to the current life system of the planet is not incurable. Most of the solutions to the problems we have created are already well known. Take human population increase. Overall population is still rising, but in several parts of the world it is levelling off. The main factors are improvement in the status of women, better provision for old age, wider availability of contraceptive devices, and better education, especially for girls and young women.

Take degradation of land and water. We know how to cope if we try. We do not have to exhaust top soils, watch them erode into the sea, rely upon artificial aids to nature, destroy the forests with their natural wealth of species, or poison the waters, fresh and salt. Take the atmosphere. We do not have to punch holes in the protective ozone layer. We do not have to rely on systems of energy generation which will affect climate and weather in such a fashion that change, even for the better, might put an over-crowded world at risk.

Take human relationships. We do not have to widen the gaps between rich and poor, or even to think of creating a genetically favoured master class. Take the way in which we conduct most scientific enquiry. We do not have to break down issues into compartments, and so miss the internal dynamics of the life system as a whole.

Moreover understanding of the Gaian approach is already spreading fast, whether it be labelled Gaian or not. I have already mentioned economics as an example of it. At present there is an astonishing failure to recognize true costs or so called externalities. Definition of costs requires a Gaian approach towards economics and towards measuring values. Here the Chinese have been pioneers with a new methodology of green accounting to measure what they call clean green growth with the objective of what they call xiao kung, or a long term, sustainable and well rounded society. But their problems, and the pressures driving them in the wrong direction, are at least as big as ours.

Sir Nicholas Stern's report on The Economics of Climate Change has been most helpful. We need a paradigm shift in which economists, politicians and ecologists alike recognize that humans are more than mere producers or mere consumers. Rather than talk about the consumer society, I prefer to call it 'the consumptive society'.

One of the key points in the Amsterdam Declaration was that a new ethical framework was urgently needed.

"The accelerating human transformation of the Earth's environment is not sustainable. Therefore the business-as-usual way of dealing with the Earth System is not an option."

But I am afraid business-as-usual will continue to guide us one way or another until we learn to think differently. As James Lovelock has pointed out, Gaia is currently trapped in a vicious circle of positive feedback. The human footprint is everywhere. What happens in one place very soon affects what happens in others. Information travels almost instantaneously world wide. Nation states exercise diminishing control while global institutions have yet to acquire accountability. There is a constant battle between short term private advantage and long term public interest. Here disasters like Hurricane Katrina or the Asian tsunami may eventually lead to a greater sense of global responsibility with action to match it.

Last week I attended a conference in Oslo entitled "Beyond Apocalypse" in which an interesting group of scientists, business people, and others, led by James Lovelock, explored how best to adapt to the changes likely to be imposed on us by climate change. I will not pretend that we came up with all - or indeed any - complete answers. Most felt that 2007 was in some sense a hinge year in which public understanding of at least climatic issues was greatly increasing, even if the talk so far enormously exceeded the action. You will have seen that the Intergovernmental Panel on Climate Change is to share a Nobel Prize with Al Gore. This represents a most welcome recognition of the scientific dimension in world politics.

Obviously the problem goes much wider than reducing carbon emissions, inventing new energy policies, and rethinking economics. We have unwittingly set in train processes that not only damage human society but push the limits within which Gaia has operated for so long. In The Revenge of Gaia James Lovelock examines some of the consequences. They do not make for happy reading.

Tonight I say simply that if we are eventually to achieve a human society in harmony with the rest of the natural world, of which we have become an awkward part, we must be guided by respect for it. No wonder that some have wanted to make a religion of Gaia. At least we need an ethical system in which the natural world has value not only for human welfare but also for and in itself. There is no greater value than recognition of the wonder of the world, and no greater wisdom than understanding our part in it. Long live Gaia.