December 25, 1989 12:00 PM

The earth is a living organism.” That startling hypothesis, proposed 20 years ago by British chemist James Lovelock, moved to the center of public awareness in 1989. Named after Gaia, the earth goddess of ancient Greece from whom the gods were said to be descended, the theory states that earth is a single giant creature in which teeming millions of life-forms, as if directed by a collective intelligence, collaborate with inorganic forces to maintain the planet as a healthy habitat for living things. If verified, Lovelock’s vision would both enlarge and to some extent revise Darwin’s theory of evolution and at the same time require a radical reexamination of man’s role in the scheme of things.

Scientists at first snubbed Gaia as holistic humbug, but with the State of the Earth shaping up as the compelling human issue of the ’90s, even staunch opponents had to admit that the theory presented an ingenious new way of looking at the world and an irresistible impulse for fresh research.

Lovelock and his principal collaborator, microbiologist Lynn Margulis, muster evidence that life has set up massive feedback mechanisms to balance the biosphere. Fact: Though the sun’s output of energy has increased by 30 percent over the last 3.5 billion years, the earth’s average surface temperature has held steady between 50° F and 68° F. Explanation: CO2 retains heat in the atmosphere, but plants multiply as earth warms, absorbing enough CO2 to cool the planet off again. Without life, Gaians estimate, earth would be as much as 80 degrees warmer. Fact: For 200 million years earth’s oxygen level has held steady at about 21 percent of the atmosphere—a matter of some importance, since below 15 percent large animals would suffocate and above 25 percent the forests would ignite. Explanation: Vegetable life, which generates the oxygen that sustains animal life, also generates the methane that stabilizes the oxygen supply at optimal levels.

Human depredations, Lovelock believes, have gravely impaired Gaia’s equilibrium. What concerns him most are tail-pipe emissions, mass extinctions (“You cannot have a sparse planet any more than you can have half an animal”) and the destruction of tropical forests (“a worse threat to human life than a nuclear war”). Will the Gaia system survive such brutalization? Lovelock is optimistic. Will it survive in a form that can support human life? Lovelock is less confident. “Gaia is no doting mother. If a species screws up, she eliminates it.”

Lovelock’s theory is controversial; his credentials are not. Holder of a double doctorate (in chemistry and medicine), he is best known as a prolific inventor who came up with the electron capture detector and used it to sniff out chlorofluorocarbons (CFCs) in the atmosphere—a fateful discovery that sounded a global alarm about the depletion of the ozone layer. Now 70 and a widower with eight grandchildren, he lives in an 18th-century Devonshire cottage with a laboratory attached. On his 30-acre farm he has planted 20,000 trees, one man’s modest offering to the goddess. “One must practice,” he says firmly, “what one preaches.”

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