Climate Science Lends Credence to Decades-Old Gaia Theory

Climate science has done more than just warn humankind about the future: it has also systematically enriched our understanding of the planet we call home.

Here’s one for fans of complexity: climate change driven by cyclic shifts in the Earth’s orbit has repeatedly shaped the pattern of life in oceans, according to a new study of plankton remains on the sea floor.

And there’s another surprise: the dramatic increase in marine micro-organisms driven by such climate shifts could, a very long time ago, have literally lubricated the birth of the mountain chains that now shape the terrestrial climate. Those first mountains were so vast and extensive that one team of scientists has argued that they played a role in creating the first oxygen in the atmosphere, and then the emergence of those organisms from which all modern plants and animals emerged.

And there’s yet another twist: life today could also owe something to the traffic in phosphorus in the ancient ocean 2.6 billion years ago, a process that launched the explosion of oxygen-emitting bacteria that had learned to exploit photosynthesis. That phenomenon created the only planetary atmosphere known to be rich in oxygen, and at the same time the only planet known to be home to life.

And researchers have unearthed yet more fresh evidence of the intricate interplay between rocks, water, atmosphere, and living things. They have found that the simple presence of iodine in the dust blown into the air from the world’s deserts may help clean up the atmosphere: it destroys ozone, a toxic version of oxygen. There is a downside to this benefit: the same process may extend the life of some of the greenhouse gases that are now warming the planet to potentially alarming levels.

But they have also confirmed that aerosol particles released by the pine, larch, fir, spruce, and birch trees of the world’s great boreal forests have the potency to change the properties of clouds: that is, to increase cloud reflectivity, and thus also cool the planet.

All six recent findings are a reminder that all life on Earth is caught up in a continuous, complex, and self-sustaining exchange with the rocks, the seas, and the air around it. This interconnectedness is so pronounced and so obvious that researchers have founded a new discipline. It’s called Earth System Science.

This, in turn, is little more than another name for a idea proposed five decades ago by two scientists, James Lovelock and Lynn Margulis, who argued that life itself could be considered as an unthinking set of forces that unconsciously cooperated to maintain the planet in ways that best suited the plants and animals that had made their home on it. This became more memorably known as Gaia Theory. Gaia was the ancient Greek name for Earth itself.

And while scientists argue about the substance and refinements of Gaia Theory, all climate science is now based on a better understanding of the intricate interaction between living things and rocks, water, and air. Life is indeed shaped by environment, but it also looks as though the environment is shaped by life This interaction is so rich and sustained and so vital that scientists have begun to ask even more profound questions.

One of these is: if a planet has a life of its own, can it also have a mind of its own? Could there be such a thing as planetary intelligence? The answer, by the way, is—maybe, but on the evidence of climate science so far, not yet. We’ll get to that reasoning later. But first, a closer look at some of the unexpected stories unearthed in the service of climate research.

There is an astronomical link between climate change and evolution. U.S. researchers report in the journal Nature that they looked at changes in the population of ocean-dwelling organisms called coccoliths: phytoplankton that build themselves little exoskeletons of calcium carbonate which end up in sedimentary rocks—think of limestone, and chalk—on the ocean floor. That is, they borrow life from the rocks, and return it again. The scientists looked at nine million coccolithophores from 8,000 samples spanning a geological record drilled from the ocean floor of 2.8 million years, to identify evidence of seasonal change over periods of 100,000 and 400,000 years.

These changes seemed to reflect cyclic shifts in the Earth’s orbit around its parent star, from elliptical to almost circular and back. These shifts turned out to be substantial enough to change the nature of tropical phytoplankton in identifiable ways. Changes in the eccentricity of the Earth’s orbit affected the climate in the tropics, which in turn played into natural selection of different species of coccoliths.

“The eccentricity cycles have multiple effects on the Earth,” said study lead Luc Beaufort of Rutgers University in New Jersey. “One of the little-known effects is the periodic appearance of seasons at the Equator. At the present time, when Earth follows an almost circular orbit, the Equator experiences a very weak change in seasons, but when the orbit is eccentric and shaped more like an ellipse than a circle, seasonal changes in tropical regions become stronger.”

But the relationship between rocks and life dates back to a much earlier time: two billion years ago, when early life began to enrich the atmosphere with vast quantities of oxygen — the source of the distinctive blue of the sky and the ocean — and the newly blue planet’s plankton population exploded. The little creatures lived out their short lives, died, and sank to the sea bottom to form beds of carbon-rich shales.

Carbon, in the form of graphite, serves as a lubricant, and this graphite in effect oiled the machinery of mountain-building. It lubricated the breaking of ocean bedrock into slabs under pressure from the movement of the planet’s tectonic plates, and helped stack these rocks to a great height across enormous distances. What may have been the planet’s first great mountain chains once extended across the first supercontinents between 2.1 and 1.8 billion years ago, according to Scottish scientists reporting in the journal Communications Earth & Environment.

In the chaste language of the study, this buried carbon “played a critical role on reducing frictional strength and lubricating compressive deformation, which allowed crustal thickening.” In other words, great slabs of rock began to stack up on each other, and although these mountain chains have long been eroded away, and the continents that bore them have fractured, dispersed and reformed, earth scientists have identified telltale evidence of this mountain-building machinery around two billion years ago, in five continents.

“Ultimately, what our research has shown is that the key to the formation of mountains was life, demonstrating that the Earth and its biosphere are intimately linked, in ways not understood,” said John Parnell, of the University of Aberdeen in Scotland.

Within weeks, new research in the journal Earth and Planetary Science Letters had delivered yet more geological evidence of interplay between life and mountains, and mountains and evolution, on the oldest-known supercontinent Nuna, sometimes also called Columbia, two billion years ago, and at least once again on the long-vanished supercontinent of Gondwana more than 500 million years ago. Such great mountain chains—think of the Himalayan heights, and then extend them to three or four times the length—create their own climates.

These include monsoon conditions, with heavy seasonal rain. And rain means erosion, which means river silt, which means nutrients washing in great quantities back into the ocean. This bonus of phosphorus and iron and other vital nutrient supplies to the ancient ocean coincided at first with the emergence eurkaryotes, those founder organisms that evolved into plant and animal life, and then much later, with the so-called “Cambrian explosion” when complex life emerged in bewildering variety.

“What’s stunning is the entire record of mountain building through time is so clear,” said study co-author Jochen Brooks of the Australian National University. “It shows these two huge spikes: one is linked to the emergence of animals and the other to the emergence of complex big cells.”

So life helped shape the atmosphere, which in turn fuelled yet more and more varied life, which played a part in reshaping the continental rocks more than once, to reshape evolution. The game of tag between the animate and inanimate worlds was already an old one: new research in the journal Nature Geoscience suggests that what geologists like to call “the Great Oxidation event”—that is, the arrival of an oxygen-rich atmosphere in the first place—may be linked with the massive build-up of chemical nutrients on the sea floor at around that time.

The still-tentative story goes like this. Cyanobacteria started producing oxygen as a form of excreta or gaseous waste. Drill samples from ancient bedrock suggest that as the oxygen reacted with the weathering rocks, the sulphate compounds in the ocean began to increase, and this in a complex chemical ballet involving oxygen and iron helped the recycling of phosphorus, an ingredient vital to life. This in turn stimulated more oxygenation. At some point around 2.5 billion years ago, the planet tipped into a new state, one with a permanently rich oxygen atmosphere, and new kinds of life evolved to exploit a resource that had, initially, been toxic to life. Such a process has galactic implications.

“It may be this process is key to a planet becoming oxygenated and therefore ultimately able to host complex life,” said Lewis Alcott, at the time of his research at the University of Leeds in the UK, but now at Yale in the U.S. “Untangling the recipe that leads to an oxygen-rich environment can help us assess the possibility of similar occurrences on other planets.”

Processes like these seem to confirm one of the core tenets of Gaia Theory: that life changes the environment and the environment changes life. But even without extra help from barracuda, bluebirds, butterflies, or birch trees, Earth and air are caught up in some kind of gavotte. Just as mountain chains encourage rainforests on the monsoon side, they also create the conditions for deserts and drylands on the other, and wind, too, is a weathering force. Dust from the North African desert has been identified as providing nutrients and trace elements to feed life in the Atlantic Ocean, and to even fertilize the rainforests of Brazil.

Now U.S. researchers have confirmed that dust—in its own way an atmospheric pollutant—can also clear the air in another sense: iodine carried by the dust has been found to reduce levels of atmospheric ozone. The same molecular form of oxygen that acts as a vital protective screen in the stratosphere notoriously makes the eyes sting in metropolitan smog at low altitude. Quite how iodine on a speck of dust does what it does to ozone has yet to be explained, according to a study in Science Advances.

Unexpectedly, too, that same iodine seems to slow the decay of greenhouse gases. “Our understanding of the iodine cycle is incomplete. There are land-bases sources and chemistry we didn’t know about, which we must now consider,” said Rainer Volkammer of the University of Colorado at Boulder, one of the authors. “The mechanism still remains elusive. That’s future work.”

There is rather more certainty about the role of what climate scientists call “biogenic emissions”. These are the often-aromatic aerosols emitted by growing foliage. These microscopic chemical droplets play a role in the way water vapour condenses, and then into the way clouds affect atmospheric temperatures. Clouds sometimes keep the warmth in, sometimes reflect the sun’s rays to cool the air below. European researchers report Nature Geoscience that they spent eight months monitoring the effect of a steady up-draught of aerosols and water vapour from the great forests of the northern hemisphere on the clouds above. And the evidence—it’s a confirmation of many previous such observations—is that forests indeed do moderate their own climate, in this case by making the clouds more reflective over periods of several days. Once again, the form such moderation takes is also affected by the things humans do: it’s not just up to the trees.

“Even small changes in aerosol precursor emissions, whether due to changing climatic or anthropogenic factors, may substantially modify the radiative properties of clouds in moderately polluted environments,” the scientists conclude.

Each small advance in research raises yet more precise puzzles. All fresh answers in climate research tend to beget yet more detailed questions. But somewhere in the fine detail of planet management there is a much bigger question: if life can evolve, and if life can evolve to manage its climate conditions, and if intelligent life can evolve, could a planet itself in some subtle way be considered to have evolved its own intelligence?

And if it could happen here, why has it not already happened somewhere far away and long ago in the galaxy? Adam Frank of the University of Rochester has grappled with intergalactic existential riddles of this kind: he and colleagues have already wondered aloud whether intelligent extraterrestrial civilizations could be sustainable enough to endure long enough to announce themselves to the universe at large, before they then destroyed themselves.

He has also asked the equally perplexing question: suppose some earlier intelligent species had evolved on Earth to create its own civilization, perhaps in the Silurian period, and then vanished. How would we ever know?

And now, he and colleagues advance the Gaia Theory to propose, in the International Journal of Astrobiology, what they call a thought experiment. Is human technological civilization—the technosphere for short—naturally self-sustaining? Right now, with the immediate potential hazard of global thermonuclear war, and the longer-term danger of catastrophic climate change coupled with global ecosystem disruption, the answer has to be no. A mature technosphere would be one that co-evolved with the biosphere in ways that would allow both to thrive. But how would that work? Don’t hold your breath.

“Planets evolved through immature and mature stages, and planetary intelligence is indicative of when you get to a mature planet,” said Professor Frank. “The million dollar question is figuring out what planetary intelligence looks like and means for us in practice because we don’t know how to move to a mature technosphere yet.”