Gaia hypothesis: is the Earth really a living entity?
The so-called Gaia Hypothesis is as famous as it is controversial:
it proposes the entire planet is a kind of huge organism composed of elements (humans,
other animals, plants, bacteria, rocks, algae,
metals) interacting with each other in mostly invisible ways to maintain stable conditions.
It was proposed by James Lovelock in the 1970s and quickly gained the limelight,
scientific and otherwise. But what exactly is it all about?
Can there be any truth to what might seem like one of the many new-age legends of our time?
What is more, we ask this question just a few months after the passing of its
originator last July at the incredible age of 103!
One of the many impediments to full acceptance of the threat of global warming is the stubborn
notion that humans are not powerful enough to influence the climate of the entire planet.
In truth, we are not the only creatures with such power,
nor are we the first species to devastate the global ecosystem. Indeed, the story of
life on Earth is the story of life continually rebuilding the Earth. Try to think about it...
Trees, algae, and other photosynthetic organisms produce most of the world's breathable oxygen,
helping to keep it at a level high enough to support complex life, but not so high that the
Earth bursts into flames at the slightest spark. Ocean plankton drives the chemical cycles on which
all life depends and emits gases that increase cloud cover, altering the global climate.
Algae, coral reefs, and mollusks store enormous amounts of carbon, balance ocean
chemistry and defend coastlines from the elements. And a wide variety of animals, such as elephants,
earthworms, and termites continually scour the planet's crust, altering the flow of water,
air, and nutrients and improving the prospects for millions of other species.
Well ... it is precisely on these suggestions that the so-called Gaia Hypothesis is based.
Conceived by British chemist James Lovelock in the early 1970s and later developed with
American biologist Lynn Margulis, the Gaia Hypothesis (named after the ancient Greeks
after the goddess who represented the Earth) proposes that all the living and nonliving
elements of the Earth are "parts and partners of a great living being that in its entirety
has the power to maintain our planet as a suitable and comfortable habitat for life."
Although this bold idea has found an enthusiastic reception among the general public from the start,
many scientists have instead criticized and ridiculed it.
"I would rather the Gaia hypothesis be confined to its natural habitat of station book stands than
to polluting works of serious study," wrote evolutionary biologist Graham Bell in 1987.
Microbiologist John Postgate was particularly vehement: "Gaia - the Great Earth Mother! The
planetary organism! Am I the only biologist who suffers from a feeling of unreality when
the media once again invite me to take these silly conjectures seriously?"
Over time, however, the scientific establishment's opposition to Gaia has diminished.
In his early writings, Lovelock had perhaps gone a little too far, thereby encouraging the
misperception that the living Earth expressed its own will. Which is obviously not easy to accept.
But these exaggerations aside, the essence of his hypothesis-the idea that life transforms
and in many cases regulates the planet's transformations-has proven prescient
and profoundly true philosophically. We and all living creatures are not only
inhabitants of the Earth... WE ARE, the Earth! We are a consequence of its physical structure
and an engine of its global cycles. And although some scientists continue to keep away from Gaia,
these truths have somehow become part of official science as well.
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Click on the bell, you will help us to make products of ever-higher quality!"
Those who chafe at the idea of a living planet argue that the Earth cannot be alive because it
does not eat, reproduce or evolve. Yet science has never established a precise and universally
accepted definition of life, only a long list of its qualities. Like many living creatures, Earth
has a highly organized structure, a membrane, and daily rhythms; it consumes, stores, and transforms
energy; and if asteroid-attacking microbes or space-traveling humans colonize other worlds,
who is to say that planets cannot procreate? If the Earth breathes, sweats, and trembles-if
it gives birth to billions of organisms that incessantly devour, transfigure, and fill its air,
water, and rock-and if those creatures and their physical environments evolve in tandem, then
why shouldn't we think of our planet as alive? This is somewhat the position of those who support
the Gaia Hypothesis with their hearts--but what are the biological mechanisms behind
such a conjecture. Do they exist? Well...Did you know, for example,
that British scientist James Lovelock, the person most responsible for the Gaia hypothesis, was
working for NASA when he first reached his living system insight questioning "is the earth alive?"
Surprisingly, though, at the time he was creating tests to detect life on Mars!
At that time, it was 1965, NASA was planning to send automated missions to the Moon, Mars,
and Venus, and one of the goals was to test first whether those environments could harbor
living organisms of some kind. Therefore, it was necessary to have a method to find out, starting
with the examination of a few elements, in the very small part that could be explored from Earth.
Lovelock had taken the approach that, rather than have probes take minute
soil tests on the red planet (using what he described as “glorified flea detectors”),
scientists should look at Mars’ atmosphere to see if it has any concentrations of gasses that could
exist only if they were maintained by living organisms. To test that idea, Lovelock looked
at the atmosphere of our own planet. Sure enough, earth’s air contains large quantities of highly
reactive gasses — such as oxygen and methane — that naturally break down into other compounds.
“If chemical thermodynamics alone mattered,” he wrote, “almost all the oxygen and most of
the nitrogen in the atmosphere ought to have ended up in the sea combined as nitrate ion.”
This simple discovery later developed into one of Lovelock’s original arguments for Gaia:
Something is maintaining numerous reactive gasses in our atmosphere
in an equilibrium steady state. (Mars, by the way, flunked the “active atmosphere” test.)
The second, and even more compelling, argument was that over the millennia the Earth has somehow
regulated its own temperature. When life began on our planet four billion years ago, the sun was 30%
cooler than it is today. Yet, from then until now, the temperature of the earth’s surface has
remained within the critical life-supporting range of 15 degrees to 30 degrees Celsius.
The level of CO has dropped a hundred fold in those four billion years, reducing the
“greenhouse” heat-holding effect of the atmosphere even while the sun was radiating more heat. The
result? The earth has kept itself at a constant temperature . . . just as our own bodies do!
Temperature and a reactive atmosphere are just two of the factors kept in balance by the earth.
One must also notice that if — as Lovelock states — “humidity or salinity or acidity
or any one of a number of other variables had strayed outside a
narrow range of values for any length of time, life would have been annihilated.”
The interactive mechanisms that accomplish this self — regulation are too complex for
current science to quantify, so Lovelock often uses a simplified model of an imaginary “Daisy
World” to suggest how the system might work. Suppose there was a planet that supported only two
plant species, white daisies and black daisies. Since the white ones reflect more heat than black
ones, they would fare better when the planet was unusually hot. The reverse would also be true:
Black daisies, being better heat absorbers, could survive better during cool periods.
But what would happen if Daisy World was cool for an extended time? Black daisies would take over
more and more of the land surface, increasing the absorption capacity of the planet and
thereby warming it up. In time, the temperature would rise to the best range for white daisies.
Those would spread, and the black ones would largely die back. But that event
would increase the heat reflectiveness of the planet, thus eventually cooling its surface.
By such means, the black and white daisies would balance each other and keep the planet’s
temperature from ever getting too hot or too cold to support plant life. On a much more
complex level, the organisms on our own planet must work together to stabilize the earth.
In sum, the Gaia hypothesis sees the earth as a self-regulating system able to maintain the
climate, the atmosphere, the soil, and the ocean composition at a fixed state that’s favorable for
life. It’s often taken that the capacity for self regulation in the face of perturbation,
change, disasters, and so on is a very strong characteristic of living things and,
in that sense, the earth is a living thing.
But Really, is the Earth Alive? Lovelock is saying that the evolution
of life and the evolution of the planet have not been separate phenomena but one single, tightly
coupled process. Life does not simply adapt to its environment but, through various feedback loops,
coevolves with it. This unifying, whole systems view is beginning to gain ground with scientists.
And the fascinating search for Gaia’s mechanisms is already leading to new areas of exploration.
Biologist Lynn Margulis, who worked closely with Lovelock on the original hypothesis,
now studies the roles that hardy microorganisms may play in regulating the atmosphere.
She’s found 200 or so mostly dormant microorganisms in tiny culture samples,
each ready under the right conditions — to perform its function and give
off its particular gaseous emission, depending on surrounding conditions.
Atmospheric scientist Pat Zimmerman examined the intestinal bacteria of termites as a source
of atmospheric methane and learned that since there are about 700 kg of termites per human
being on earth, and since the wood nibblers go through the equivalent of one-third of the
new plant carbon created every year, they may produce half of the methane in the atmosphere!
But Lovelock’s words have at times suggested that the planet’s totality of life is deliberately
working to better its condition and increase itself. Adding such an aspect of purposefulness
(even consciousness) to Gaia grates on most otherwise sympathetic scientists.
Any hints that the whole system may indeed be alive are taboo to them — that’s talking
religion. And we should never forget that science and spirit are different realms.
They are not in conflict, but there’s no interface between the two. There’s no foresight or planning
involved on the part of life in regulating the planet. It’s just a kind of automatic process.
Life regulates the stability of the atmosphere so that it can survive. This is not an intentional
directive, but is the result of millions of years of interactions between life and
Earth's atmosphere; one cannot be seen without the other. Life and the Earth, says Lovelock, are one.
That hasn't stopped many non-scientists from
drawing their own conclusions about the implications of the Gaia hypothesis.
While the scientific community credits Gaia with providing ecologists and climatologists
with a new key to the study of the planet (linking things previously considered distant such as human
activities and ecosystems), it was and remains problematic both as a theory and as a hypothesis.
Impossible to put to the test, for critics Gaia has always been an idea at odds with
proven theories and paradigms such as, for example, Darwinian evolution, which ill fits
with the thought of an entire planet somehow managing to cooperate for the good of all.
Biogeochemical cycles do exist, as does the ability of ecosystems to resist change: but that
is not why we should infer that the planet is purpose-driven. Over the years, Stephen Jay
Gould and other evolutionary heavyweights have challenged Gaia on this very ground.
Outside the academy, Gaia is now instead a very strong,
very pop entity. Its message is so penetrating and ecumenical that, watered down and often skewed,
it has come to influence cult science fiction novels and movie blockbusters like Avatar, Zen
musings and popular essays, school curricula, and documentaries. It is a grand vision, once again
ousting human beings from the center of the universe, we live in a complex synergistic,
self-regulating system-perfect for conveying a certain kind of environmentalism.
So what can we say? Most likely we also need an emotional component to
trigger our scientific speculations--a fideistic and motivational drive that
can open a door in our minds. Even if with the wrong key.