Gaia Theory

James Lovelock

February 2003

James Lovelock is one of the world's truly extraordinary scientists. For the last 35 years, he has worked independently from home, where he has consistently produced world-class science. His electron capture detector was the first to show us that low levels of pesticides were present throughout the natural world. For this he is credited with inspiring the green movement of the 1960s. He also discovered that CFCs were accumulating in Earth's atmosphere. From this we learnt that we were putting the protective ozone layer in jeopardy. But most important is his revolutionary theory, Gaia. His metaphor that Earth behaves like a living organism couldn't be more profound in its implications for how we live on Earth. In January 2003, Lovelock was made a member of the Order of the Companions of Honour – a fitting tribute to a tireless worker. For Lovelock, this was confirmation that Gaia has made it through the establishment gates. Here, he tells us how his Gaia Theory was conceived.

Astronomers sometimes scare us by reminding that the Sun is due to swell up into a red giant star that will burn Earth to a cinder. This is true but it won't happen until another five billion years have passed. What astronomers rarely mention is that this inflammation is no sudden change but the inevitable end of a long, long fever. Our Sun started to warm up soon after its birth 4.5 billion years ago. So far it has only warmed by about 30% but the rate of warming will steadily increase until the red giant stage marks the end of its active life. A 30% warm up doesn't sound much until you realise that it's equivalent to about a 25ºC rise of temperature for the Earth's surface. Or to put it in more familiar terms, seven times the difference between an ice age and now. If the Sun was delivering a third less heat when life started four billion years ago how on earth was it warm enough for it to flourish? alternatively, if it was warm enough then why are we not now intolerably hot?

One answer to this puzzling question about Earth's temperature, and why it has always been comfortable for life, is that maybe our planet has the capacity to keep its temperature right for life. Just as we keep our core temperature close to 37ºC regardless of whether it is freezing outside or torridly hot. Temperature is not the only property of Earth that somehow or other stays right for life. Have you ever wondered about the air you breathe and why the oxygen is 21%, not 50% or 10%? It so happens that if the oxygen were above 25% fires would be so fierce that few if any trees would survive and if it were below 15% it would be impossible to start a fire. 21% is just right.

Many other properties of Earth, like the cloudiness of the skies and the abundance and quality of rain, are uncannily right for life. So many of them in fact that it's reasonable to ask if all these things can be right by chance?

Conventional view

Until quite recently, the conventional wisdom of science was that we were indeed very fortunate to have been born on a planet that by chance circled its star (the Sun) at exactly the right distance to be right for life. Moreover, most scientists believed that life adapts to the material world it finds and that the whole Earth environment including the air, the oceans and the surface rocks were all products of geological forces alone.

We are just beginning to realise how wrong is this view of Earth. I think it happened because we arbitrarily separated biology and geology – we teach the evolution of life and the evolution of Earth as separate subjects in separate buildings in our universities. It may be easier to teach this way but the price is that we lose sight of the whole planet while examining ever more minutely its details. Earth evolves as a single system, and its living organisms and their material environment are closely connected parts of the whole.

Atmospheric clues

My interest in Earth as a whole system began in 1965 when I was part of a Nasa team preparing the instruments for the search for life on Mars. I soon grew disenchanted with the approach of my biologist colleagues who planned instruments that would find the kind of life they knew about on Earth. They showed little concern about the possibility that Martian life might be quite different. I couldn't help wondering whether there might be a more general way to detect life whatever its form.

The great physicist Schrödinger in his book What is Life (1944) proposed that one characteristic of life was its ability to reduce its entropy, or in simpler but less accurate words, bring order from chaos. although it's not easy to understand or measure entropy directly, we can use Schrödinger's idea for recognising planetary life simply by chemically analysing the composition of a planet's atmosphere.

If life existed on a planet it would be obliged to use the atmosphere as a source of raw materials and a place to deposit wastes. Such use would reduce the entropy of the atmosphere and change the chemical composition into something easily recognised as different from the neutral equilibrium atmosphere of a dead planet.

When I compared the atmospheres of Mars and Venus with that of Earth it was immediately apparent that our atmosphere was far from a state of chemical equilibrium and therefore much lower in entropy. Whereas the atmospheres of the other two planets were close to equilibrium, high in entropy, and therefore, according to my ideas, bereft of life. My proposal is now part of Nasa's astrobiology program and they aim to use it in the search for life on extra solar planets.

Regulated planet

Anyone on a spacecraft far outside the solar system looking at Earth with an infrared telescope and spectrometer would see a planet that was unequivocally rich with life. They would detect an atmosphere that, apart from the noble gases, has a composition almost wholly determined by the organisms at the surface. So tightly coupled is life with the atmosphere, that if some catastrophe removed all life from Earth without changing anything else, the atmosphere and surface chemistry would rapidly – in geological terms – move to a state similar to Mars or Venus.

They are dry planets with atmospheres dominated by carbon dioxide and close to the chemical equilibrium state. By contrast, we have a cool, wet planet with an unstable atmosphere that somehow stays constant and always fit for life. The odds against such stability are close to infinity. Science is not concerned with such improbabilities, so we are forced to consider the difficult but more likely alternative – something regulates the atmosphere. What is it?

It has to be something connected with life at the surface because we know that some atmospheric gases (oxygen, methane and nitrous oxide) are almost wholly biological products, while others (nitrogen and carbon dioxide) have been massively changed in abundance by organisms.

Moreover, the climate depends on atmospheric composition and there is evidence that Earth has kept a comfortable climate ever since life began in spite of a 30% increase of solar luminosity. Together, these facts led me to propose in a 1969 paper in the Journal of the American Astronautical Society that the biosphere was regulating the atmosphere in its own interests. When I discussed this idea with my neighbour the novelist William Golding, he suggested that I call it Gaia, the name the ancient Greeks gave to their Earth goddess.

Two years later I started collaborating with the American biologist Lynn Margulis on what we called the Gaia hypothesis. We postulated the biosphere to be an active, adaptive control system, able to maintain Earth in homeostasis.

Scientific critique

Earth scientists found the hypothesis interesting, but evolutionary biologists regarded it with dislike and it was not long before Ford Doolittle, Richard Dawkins and other biologists challenged it. They pointed out that global regulation by the organisms could never have evolved because the organism itself was the unit of selection, not Earth. In time I found myself agreeing with them. They were right, there was no way for organisms by themselves to evolve so that they could regulate the global environment.

But I wondered if the whole system, organisms and environment together, could evolve self-regulation? In 1981, I redrafted the hypothesis as an evolutionary model, Daisyworld, that was intended to do no more than show that self-regulation can take place on a planet where organisms evolve by natural selection in a responsive environment. The model worked so well that I was able to restate Gaia as follows:

The evolution of organisms and their material environment proceeds as a single tightly coupled process from which self-regulation of the environment, at a habitable state, appears as an emergent phenomenon.

At about the same time, Andrew Watson, Mike Whitfield and I discovered the first mechanism for climate control by the Earth system. Namely, the biologically assisted reaction between atmospheric carbon dioxide and calcium silicate in soil and on rocks. This process can regulate both climate and carbon dioxide at a level comfortable for plants. Soon afterwards, in collaboration with Robert Charlson, Andi Andreae and Stephen Warren, I suggested another climate regulation mechanism – the connection between ocean algae (which produce the gas dimethyl sulphide) clouds and climate. The meteorological community took the suggestion seriously and awarded the four of us the Norbert Gerbier Prize in 1988. By the end of the 1980s there was sufficient evidence and models of the hypothetical system to justify calling it Gaia Theory.

Scientific acceptance

Like all new theories, Gaia had a hard time in its early days and most scientists scorned it. It's worth recalling that scientists rejected quantum theory for many years after its inception by Max Planck. That greatest of scientists, Einstein, found it nearly impossible to swallow and his put down that 'God does not play dice with the Universe' has lingered. It's right and proper for new theories to have to run the gauntlet of criticism, otherwise feeble and erroneous notions would clutter the wisdom of science. Gaia Theory is now past its time of trial and is becoming part of the conventional wisdom of science.

The turning point came in 1999 when the truly eminent biologist William Hamilton, previously a strong critic of Gaia, said that it made just as profound a change in our view of Earth as had Copernicus's discovery that Earth circled the Sun, not vice versa.

Through Gaia we are now aware that our planet is no longer just a ball of dead rock moistened by the sea and encapsulated in a film of air. It's a live planet able to control its own destiny or if you prefer science speak, it's the planet described by the Amsterdam Declaration made in 2001 by over a thousand scientists – 'The Earth system behaves as a single, self-regulating system comprised of physical, chemical, biological and human components.'

Timely theory

The acceptance of Gaia Theory by science is timely because we are now seriously changing the environment and the consequences predicted by the International Panel on Climate Change are serious. If we are to reverse these changes we need to understand Earth fully.

To give just one example of how whole system thinking changes our view, consider biodiversity. There is evidence that we are in the midst of a great extinction of our own making, but Gaia Theory suggests that biodiversity is not necessarily a measure of fitness. It can be a symptom of the perturbation of an ecosystem during a state of comparative health. What seems important for sustenance is not so much biodiversity as such, but potential biodiversity, the capacity of a healthy system to respond through diversification when the need arises. Rare species make forest and other ecosystems biodiverse and some of these rarities will flourish and sustain the ecosystem when the next large environmental change takes place.

Biodiversity is like insurance, not needed now, but required when disaster strikes. The loss of biodiversity seldom occurs alone, it's part of the destructive process of converting natural ecosystems to farmland. We have to keep in mind that any destruction of natural habitats weakens Earth's capacity to sustain a habitable world. As well as scientific understanding, we need a feeling for Earth as a living entity. Only then will we grasp that we cannot farm the whole planet to feed the growing population. If we try to do this we will disable Gaia, which has kept conditions favourable for life for four billion years

Civilization depends upon a proper recognition of human rights but the time has come to see that to care for human rights alone is not enough. We share our planet with all of the burgeoning forms of life and together with them we are a giant community that is the responsive part of the Earth system. If we want to sustain our civilisation we need to take care of Earth as much as we do humanity. There is no future for any of us on a dead planet.

Find out more

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Websites

Gaia Theory: Science of the living Earth
www.gaianet.fsbusiness.co.uk/gaiatheory.html
A brief introduction to Gaia theory by David Orrell.

Guide to Philosophy and the Environment
www.lancs.ac.uk/users/philosophy/
mave/guide/gaiath~1.htm
Looks at Gaia theory and presents the evidence, the criticisms, the Daisyworld model and the philosophical implications.

Origins – Channel 4
www.channel4.com/science/
microsites/O/origins/
Tells the story of our world from its violent birth 4.6 billion years ago to the emergence of modern man.

Books

Homage to Gaia: The life of an independent scientist by James Lovelock (Oxford University Press, 2001) £9.99
The fascinating story of his life as an independent scientist, James Lovelock tells us the history behind his famous Gaia Theory and talks us through his many inventions, including the electron capture detector, and his work for many organisations around the world.

Gaia in Action: Science of the living Earth edited by Peter Bunyard (Floris Books, 1996) £14.99
Comprises a collection of essays and presentations, based on the international conferences on Gaia held annually. The book seeks to define Gaia and translate the theory into practical ways of relating to the planet as a whole. Contributors include James Lovelock, Lynn Margulis, Brian Goodwin, Mae Wan Ho, Peter Saunders and Kate Rawles.

Lovelock and Gaia by J Turney (Icon Books, 2003) £9.99
Looks at Gaia Theory's long struggle to gain respectability and argues that its impact compares with the greatest of scientific revolutions.

What is Life by Erwin Schrodinger (Cambridge University Press, 1992) £10.95
Originally published in 1944, Nobel laureate Schrodinger has written one of the great science classics of the 20th century. A distinguished physicist's exploration of the question which lies at the heart of biology, it was written for the layman, but proved one of the spurs to the birth of molecular biology and the subsequent discovery of the structure of DNA.

Environmental Ethics: Duties to and values in the natural world by Holmes Rolston III (Temple University Press, 1989) £21.50
The US environmental philosopher discusses expanding the ethical circle to include the natural world.

The Symbiotic Planet: A new look at evolution by Lynn Margulis (Science Masters, 1999) £6.99
Gaia supporter Margulis examines Earth's evolution.

Microcosmos: Four billion years of evolution from our microbial ancestors by Lynn Margulis and Dorion Sagan (University of California Press, 1997) £8.95
Discusses the interdependancy and the interconnectedness of life on Earth.

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