Gaia Theory

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James Lovelock

February 2003

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.'

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