Once dismissed as heresy, Jim Lovelock's theory of earth as a single organism has become an accepted orthodoxy. Fred Pearce talks to the self-styled father of the environmental movement.

Jim Lovelock, in his final years, is contemplating the embrace of Gaia. His supreme creation, his scientific earth goddess, will finally claim him. In the words that concluded his recent autobiography Homage to Gaia : "It is comforting to think that I am part of her, and to know that my destiny is to merge with the chemistry of our living planet."

Lovelock, who will be interviewed on stage at the Edinburgh Festival next week, is an independent scientist extraordinaire, most famous as the inventor of the notion that our planet functions as a single, self-regulating organism. He says the earth's living forms have, for hundreds of millions of years, been altering their environment to make it - in the words of Goldilocks - "not too hot and not too cold, but just right". And, following a suggestion from a former neighbour, author William Golding, he called this living, breathing planet Gaia, after the Greek earth goddess.

But as Lovelock contemplates his career from his remote farmhouse-cum-laboratory on the edge of Bodmin Moor in Cornwall, it is clear that the biological heresy of Gaia is increasingly bedding down in modern science. You can find it underpinning some of the more alarming predictions for global warming from the United Nations' Intergovernmental Panel on Climate Change. And it found full expression at a UN conference on planetary science in Amsterdam last summer, which declared "the earth system behaves as a single, self-regulating system comprised of physical, chemical, biological and human components".

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Some biologists, always his harshest critics, still question the Gaia idea. What's in it for the individual organism itself? they ask. Why would a daisy go to the trouble of becoming white to reflect more of the sun's rays and help keep the planet cool? What Darwinian mechanism would make seaweed evolve to send chemicals into the air that can nucleate water droplets and make clouds?

But Lovelock can be pretty certain now that the science of Gaia will outlast him. For other biologists are coming up with answers to these hard questions. Daisies turn white because it is easier than adapting to the heat. It suits them as well as the rest of the planet. And the seaweed that creates clouds over a cloudless sea is also making the weather that will disperse its seeds more widely. All eminently Darwinian.

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Besides, something has to explain why, over hundreds of millions of years, our atmosphere's temperature has remained broadly steady even as the output of the sun has dramatically increased. Biology, now widely recognised as a fundamental factor in the atmosphere's chemical makeup, is the obvious candidate.

Faced with growing evidence that organisms can and will evolve to manipulate as well as to adapt to their environment, even arch foes such as evolutionist Richard Dawkins seem to have thrown in the towel. "I don't think he'll ever come out and say he was wrong, but he isn't throwing bricks any more," Lovelock says with some satisfaction.

A distant relative of the poet Thomas Chatterton, Lovelock was conceived on armistice night in 1918. Now in his 80s, he has largely handed on the Gaian flame to much younger acolytes, such as Tim Lenton of the Centre for Ecology and Hydrology in Edinburgh. But he still makes occasional public appearances, such as the Edinburgh Festival event, and he continues to experiment and ponder. "I've got a new infrared thermometer," he says with enthusiasm. "I can point it at things like trees, or even clouds, and gauge their temperature. Dark trees turn out to be cooler than the surrounding air, which was a surprise. Now I am looking at the difference that autumn colours make." Idle meanderings of an ageing scientist unwilling to give up the white coat? Don't believe it. If autumn colours change the temperature, he has another potential Gaian feedback.

And don't forget that Lovelock made his name - and a good living - out of inventing devices and clever things to do with them. He virtually conjured up the modern green movement with a widget called an electron capture detector that can sniff out the tiniest amounts of chemicals in the air - less than a part per trillion, in many cases. Without him, Rachel Carson would not have written her seminal Silent Spring in the 1960s and nobody would have had a clue why the ozone layer was disappearing in the 1980s.

In the 1970s, Lovelock advised Nasa how to check for life on Mars without the trouble of going there. Just look for signs of organic influences on the Martian environment, he said. "But even today, they don't want to believe me," he says with the sorrow of a prophet scorned. "They are more interested in a Boys' Own quest to the planet than doing good science. Gaia doesn't fit their plan at all."

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He had better luck with British intelligence. He reveals for the first time in his autobiography how in the 1960s he ran a secret lab at Holton Heath in Dorset, where he turned his electron capture detector into a device for tracking KGB agents. He laughs now at the idea of secret agent Lovelock devising the hardware for James Bond. But it was not so far from the truth.

A certain slipperiness, secretiveness and plain mischief underlies much of his work. Though a friend of Margaret Thatcher, Lovelock claims never to have voted Tory. Though a punctilious scientist, he has done much to promote the spiritual connotations of Gaia that so annoy fellow practitioners. ("Science and spirituality are, of course, opposites, but human beings are contradictory creatures," he says.) And though the self-styled father of the environment movement, he regularly crosses swords with it - most notably on nuclear power. "The greens have done great harm with their opposition to nuclear power. In terms of deaths per gigawatt-hour, nuclear power is ten times safer than any other fuel," he says. "Windmills are never going to take over our baseload power supply. But the French have shown that nuclear power can. It is the best way of cutting greenhouse gas emissions."

He thinks one of the best ways to protect the world's natural ecosystems - and with them the Gaian planetary regulatory systems - is to turn farming into a branch of biochemistry. "We could produce all our beef from tissue-culture using feedstock from the chemicals industry."

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In many ways, he is a forerunner of the Dane Bj?rn Lomborg, whose book The Skeptical Environmentalist has so angered the green community in the past two years by dissecting their nostrums. "I am a sceptical environmentalist," he agrees. "The greens have their hearts in the right place, but they do need bringing up short sometimes." But while he reckons that Lomborg rightly blew the whistle on some of our fears about nuclear and chemical perils, he thinks the Dane has elsewhere been misled by industrial lobbyists and their scientific lackeys - on global warming, for instance.

Changing climate, he believes, is the overwhelming issue of our time. It has real potential to overwhelm Gaia's powers of planetary regulation. "The biofeedbacks from global warming are mostly positive. They make it worse, not better," he says. Mankind may have found Gaia's Achilles' heel. "I see the western world as being like the passengers and crew on the Titanic . We know there are icebergs out there, but we believe we are on a ship that cannot sink. And that won't change until the first really nasty climatic event brings us to our senses."

Maybe true. But with Lovelock up on the bridge, his telescope in hand and his megaphone still by his side, nobody can say we haven't been warned.

Jim Lovelock will be "in conversation" at the Edinburgh Festival on August 17.

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