Gaia Revisited

Tim Beardsley - 1 August 1991

The Gaia hypothesis is still being debated in scientific circles, but has been enthusiastically embraced by the environmental movement. The question is, is it appropriate to propose a planetary consciousness for Gaia, the Earth Goddess, or is it of more interest as an ecological construct?

In the late 1960s, James E. Lovelock, an independent British researcher who works in his home laboratory, began to expand an idea that wove dawning public concern about the environment together with a benign mysticism. The original concept can be simply and appealingly stated: all of the animals and plants that inhabit the Earth can be regarded as a single vast organism capable of manipulating the atmosphere, geosphere and hydrosphere to suit its needs. Lovelock named this organism Gaia, the Greek goddess of the earth.

Lovelock, an accomplished inventor, was inspired by his experience designing life-detecting sensors for the Viking missions to Mars. Noticing that the Earth’s atmosphere (unlike that of Mars or Venus) has long been far from chemical equilibrium, he proposed that Gaia strives to maintain optimal conditions in the face of changing astronomical inputs, such as the Sun’s slowly increasing brightness.

Lovelock’s musings have had two consequences. They inspired a quasi-political movement based in London, complete with a publishing arm, that now includes thousands of adherents throughout the US and Western Europe. Indeed, Gaia has almost become the official ideology of Green parties in Europe: it appeals naturally to scientifically innocent individuals who worry about the environment.

“A lot of people who don’t believe in science really like Gaia,” comments one biologist, W. Ford Doolittle of Dalhousie University in Halifax, Nova Scotia.

Allergic Reaction

Gaia has also triggered an acute allergic reaction among mainstream biologists. Doolittle and Richard A. Dawkins of the University of Oxford spelled out the principal objection. Gaia seems to require that some organisms restrain their reproduction in order to benefit the larger community.

Yet natural selection favours genes that increase their frequency. Thus, there is no mechanism for the evolution of organisms that will altruistically sacrifice immediate advantage for some future benefit, unless life has foresight. It does not, Dawkins argued: selfish genes will therefore simply crowd out visionary genes.

In response to such criticism, Lovelock has modified Gaia. In his recent book The Ages of Gaia, he offers in place of the original “hard” Gaia, a softer version. The new soft Gaia “has the capacity to regulate the temperature and composition of the Earth’s surface and to keep it comfortable for living organisms,” but she does not globally optimise — a notion that evolutionists find meaningless. And Lovelock is careful to avoid endowing Gaia with foresight. Nonetheless, Lovelock’s 1988 version of Gaia still exhibits homeostasis (meaning that she tends, like a thermostat, to counteract imposed changes).

“The evolution of organisms and the evolution of their environment are tightly coupled as a single process,” Lovelock writes. “Self-regulation is an emergent property of this process.”

But even global homeostasis is hard for most biologists to accept. The difficulty lies in imagining how to bridge the gap between local effects and planetary changes. An organism that alters its environment to benefit its offspring is onto a good thing — that is why birds build nests. But it is hard to see how such Darwinian nepotism could operate over many generations at continental distances.

Daisyworld Model

In an attempt to answer Dawkins and Doolittle’s criticisms, Lovelock has devised an illustrative mathematical model called Daisyworld. The model demonstrates how “daisies” of different colours, subject to natural selection, can regulate the temperature of an imaginary planet even as the “sun” changes brightness. Dark-coloured daisies proliferate when the sun is cooler and, by absorbing heat, warm the planet: the reverse is true of light-coloured daisies.

Lovelock maintains that Daisyworld proves that Darwinian natural selection can produce global homeostasis. Others disagree.

“Daisyworld is an essentially arbitrary view of how the world works,” says James W. Kirchner of the University of California at Berkeley. The model regulates temperature only, he says, because the daisies have contrived and implausible properties. If more realistic daisies are allowed to spring up, then Daisyworld fails to achieve stability.

Lynn Margulis of the University of Massachusetts at Amherst, an outspoken champion of Lovelock’s ideas, dismisses the Doolittle-Dawkins criticism as reflecting an ignorance of chemical ecology. She maintains that Gaia can actively regulate conditions, whereas the standard Darwinian view holds that the conditions change by chance and that organisms adapt to them.

Margulis admits that the criticisms of the biological establishment persuaded her, as they persuaded Lovelock, to stop describing Gaia as optimising. She also dislikes describing Gaia as an organism (because organisms do not recycle their wastes). Moreover, Margulis disavows homeostasis because the regulated levels change over time.

“Gaia has caused the discrepancy between what you’d expect on chemical grounds alone and what you actually see,” she says.

Stability Vs Change

How might “active regulation” be distinguished from mere influence? One possibility is that it would produce stability. Yet some scientists who find Gaia interesting, such as Stephen H. Schneider of the National Centre for Atmospheric Research, have long maintained that some of the feedback loops that link living things and their environment are likely to be destabilising. Moreover, climate and the composition of the atmosphere have changed drastically since the Earth’s formation, and many of the changes were harmful to life. The fossil record is punctuated by mass extinctions.

Margulis acknowledges that there is a problem recognising stability when ecosystems are continually changing, but she offers no solution. So is Gaia just a metaphor or an aphorism like “nature red in tooth and claw”? Only insofar as all science is metaphor, Lovelock parries.

Gaia, now approaching her third decade, does not resemble a living organism: she no longer has foresight, she no longer optimises and (according to Margulis) she no longer maintains homeostasis. What is left to distinguish Gaia from a conventional view of evolution in which organisms generally make the best of what they can get? How could a nonhomeostatic Gaia ever be detected?

Is Gaia, then, anything more than the simple persistence of life? If so, she has yet to reveal herself. Her many lay followers, however, seem to be unwilling to hear that the goddess of their temple is nowhere to be found.

Tim Beardsley, Scientific American, December 1989