TIME: Almanac 1993/TIME Almanac 1993.iso/time/111389/11138900.062

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                                                                                IDEAS, Page 114

How the Earth Maintains Life


An intriguing scientific theory continues to win adherents

By Eugene Linden


    One of the greatest benefits of the Apollo space program
was the image in the rearview mirror as the astronauts rocketed
to the moon. It was the first time earthlings could see their
home as a whole, and NASA's pictures said with stunning force
what neither words nor theories could adequately convey: life
has radically transformed this numinous sphere. The
heart-stopping beauty of the earth set against the dark void of
space earned inventor-scientist James Lovelock the first
adherents to a theory that appears to reconcile science and
religion in the study of life on earth. Lovelock's idea, named
the Gaia hypothesis after the ancient earth goddess of the
Greeks, is that the planet is alive and functions as a
superorganism in which living things interact with geophysical
and chemical processes to maintain conditions suitable for life.

    Lovelock was not the first to argue that earth functions
like a giant organism; Scottish geologist James Hutton made the
same point in 1785. But Lovelock's formulation is compelling
because science now has the tools to explore some of the vast
interactions that govern global systems. Although Lovelock first
articulated his hypothesis in the early 1970s, in collaboration
with microbiologist Lynn Margulis, it has only recently begun
to have significant impact on the scientific world. Initially,
Gaia was only embraced by New Age types who responded to a
holistic view of nature that blurred the distinction between
life and death.

    Lovelock and Margulis have modified the theory over the
years to address scientists' criticism that Gaia implied that
the earth acted with a sense of purpose. In its newest form,
Gaia has inspired a flood of research into the interaction
between living systems and the atmosphere, earth and oceans. At
the first major scientific conference on Gaia, sponsored by the
American Geophysical Union in 1988, the austere group of
scientists ended their meeting by giving Lovelock an exuberant
standing ovation.

    Scientists have begun to regard Gaia more seriously because
the world has forced them to do so. If they are to understand
such pressing environmental problems as the greenhouse effect
or the consequences of mass extinctions, they will have to
overcome their reluctance to look beyond their own specialties:
nature does not necessarily respect the arbitrary boundaries
established for scientific disciplines. By focusing on entire
systems, Gaia provides a framework through which marine
biologists, geochemists and geophysicists can integrate their
work.

    According to the Gaia hypothesis, earth's atmosphere would
be unstable for life if it were not regulated by the biosphere,
the envelope of life surrounding earth. Oxygen levels have
remained at roughly 21% of the atmosphere for 200 million years,
Lovelock asserts, whereas they should have fluctuated wildly,
according to some geochemical models of the atmosphere. Were
oxygen levels to rise above 25%, spontaneous fires would break
out; if they dropped below 15%, many higher life-forms would
suffocate. Climatologist Tyler Volk of New York University
argues that life controls earth's temperature as well. In a
study recently published in the British journal Nature, he and
colleague David Schwartzman asserted that, without the cooling
effects of living things, earth would be 80 degrees F warmer.

    Lovelock originally thought that some purposeful design
organized living things to stabilize the atmosphere and
climate. Now he and Margulis believe this regulation is achieved
through the simple mechanism of feedback. For instance, in a
hypothetical scenario, Lovelock shows that a planet covered
simply by light- and dark-colored daisies could control the
sun's heat. In this self-regulating model, dark daisies would
absorb sunlight and warm the planet, until it became too warm
for the dark daisies and instead favored the proliferation of
light-reflecting daisies. That would have the effect of cooling
the planet until the cycle reversed itself again.

    Scientists have yet to uncover the actual mechanisms by
which life processes regulate earth's climate and atmosphere.
Lovelock maintains that this makes it all the more imperative
that man halt the mass extinctions threatened by the destruction
of tropical forests, because he does not know what creatures are
essential to his own survival. At the American Geophysical Union
conference on Gaia, Lovelock argued that diversity makes earth
both stable and habitable: "You cannot have a sparse planet any
more than you can have half an animal."

    Gaia's critics have by no means been silenced. Some dispute
the degree to which life-forms stabilize the atmosphere and
temper the climate. Others contend that the emergence of oxygen
in earth's atmosphere contradicts Gaia because it made the air
poisonous for anaerobic creatures of primordial times.
Evolutionary scholar Richard Dawkins argues that earth cannot
be considered an organism because it does not reproduce. Gaian
proponents respond that the increase of oxygen in the atmosphere
was slow enough to allow the mix of life-forms to adjust, and
physician-author Lewis Thomas answers Dawkins by coyly
suggesting that, through space exploration, mankind may be
acting as an inadvertent disseminator of earth's spore.

    Its critics notwithstanding, Gaia seems to be gaining in
influence among both scientists and theologians. To some,
Gaia's appeal is that it promises to end the long estrangement
of Western science and religion. Even if the biosphere regulates
the planet by feedback, Gaia still integrates living things and
inanimate forces into a unified system, allowing both science
and religion to look at life as something more than a mere
accident. Says James Parks Morton, dean of New York City's St.
John the Divine Episcopal Cathedral and a leading religious
advocate of Gaia's: "The very nature of this hypothesis shows
that we are now at a new moment when scientific and religious
inquiry is directed to the same reality and discussed in a
common language."