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How James Lovelock introduced Gaia to an unsuspecting world

Once in a generation, perhaps, you get to read a book that will change the way we see the world. But it might take a whole generation to realise by how much.

My copy of Gaia is a first edition from 1979: hardback price £4.95 (and there were no discounts in those days). To re-read the original text is to be reminded, in all sorts of unexpected ways, how far we have come. Its author has since morphed from J E, an "independent scientist", to James Lovelock , the world-famous author and speaker. The once-tentative Gaia hypothesis has become part of scientific orthodoxy and has been formally enshrined as the Gaia Theory, although in the US it has been dubbed Earth System Science.

A new generation of telescopes will soon be sweeping the nearby stars for evidence of oxygen and methane in the atmospheres of the planets that orbit them: a simple idea proposed by Lovelock 40 years ago during the hunt for life on Mars, and at the time no doubt dismissed as a bit too simple.

The Gaia hypothesis, as it then was, is simply put. Life may be the product of blind chance and opportune circumstance, but once it has established itself on a planet, it takes over. It manages the planet in ways that continue to sustain life in more or less optimum circumstances. That is why it may be a mistake to call Earth the Goldilocks planet: not too hot, not too cold, but just right. In fact, Earth's average temperature may be just right because life, by unconsciously manipulating the planet's oceanic and atmospheric chemistry, sets the thermostat that keeps its Earthly home within a temperature range that is comfortable for life.

At the time of publication, this idea seemed either thrilling or preposterously New Age, and sometimes both. Biologists in particular were annoyed because they see evolutionary forms as having adapted to their environments through natural selection, blindly and without purpose or direction. This remains true, but it is also true that having found an ecological niche, all creatures – elephants, ants, orchids and economists – tend to maintain their environments to their own advantage, and it now looks as though collectively, the whole assortment that we call life has got a good grip on Earth, has dug in, so to speak, and made itself at home.

Lovelock won over first his readers and then his fellow scientists by asking questions that might not have been obvious to any of us at the time. Where did the nitrogen in the atmosphere come from? Why was the proportion of atmospheric oxygen just within the safety zone? Why wasn't the sea far more salty? Why hasn't all that water boiled off into space? From such questions, he patiently built up an argument that began to sound increasingly interesting: that life is an agent in its own survival. At the time, some of us admired the book enormously, and still do, for its provocation, for its daring, for the huge sweep of the ideas that unfold.

Only now, on rereading, have I realised how tentatively Lovelock put his argument. Of course it depended on reasoning, but good evidence had still to be established. The other thing that strikes me is how well written it is. Having invested a few paragraphs in rehearsing the improbability behind the assembly of sentient, self-replicating life from a chemical soup, in turbulent conditions, over immense timescales, Lovelock cheerfully resolves it all on page 14 by concluding, "Life on Earth was thus an almost utterly improbable event with almost infinite opportunities of happening. So it did."

I don't think I've ever seen a neater or more graceful summation.

The green movement gleefully embraced the metaphor of Gaia, but sometimes found Lovelock himself stubbornly unaccommodating: a chemist perfectly comfortable with the judicious release of pesticides, chlorofluorocarbons and atmospheric pollutants; a proselytiser for nuclear energy; a man who when he encountered a bandwagon, instinctively wanted to take its wheels off.

He cheerfully points out that the first great toxic pollution crisis for Gaia was the emergence of free oxygen in the atmosphere. Those microbial life forms that could not adapt thereafter survived only as anaerobic bacteria in swamps and in the intestines of animals.

He makes a case for the planet as a vast chemical apparatus. The natural oxidation of atmospheric methane produces a billion tonnes of carbon monoxide gas each year. Nature bubbles with sulphur dioxide, dimethyl mercury and a host of carcinogens, all part of Gaia's planetary management chemical kit.

On page 113 Lovelock reports, expressionlessly: "It has been predicted that the increase in carbon dioxide will act as a sort of gaseous blanket to keep the Earth warmer." On page 41, he addresses a different bubbling atmospheric anxiety by conceding: "There was of course at the time of the report a strange and disproportionate concern in America about stratospheric ozone. It might in the end prove to be prescient, but then as now it was a speculation based on very tenuous evidence."

It would be another six years before a British scientist identified the alarming hole in the ozone layer, and it was Lovelock himself who devised the instruments sensitive enough to detect levels of CFCs in the atmosphere. So at the time of writing the book he was right: ozone destruction was speculative, and the evidence was tenuous.

Similarly, it would be another nine years before global warming exploded as a political concern. In fact, on page 149, Lovelock is rather more concerned about the fate of the next ice age, suggesting that the presence of "a large quantity of chlorofluorocarbons" might entirely reverse the onset of glaciation, "or at least greatly diminish its severity".

To reread Gaia is to be reminded about how little we knew about our own planet in 1979, and how much of what we now know began to emerge as Lovelock and other scientists addressed some of the questions raised in this remarkable book: the first of a series of books that have developed, propagated and defended a remarkable and enduring idea.

Next month we will start to review, in no particular order, all six books shortlisted for the prestigious Royal Society Prize for Science Books . The winner will be announced on 21 October. The titles before the judges are:

A World Without Ice by Henry Pollack (Avery)

Everyday Practice of Science: Where Intuition and Passion Meet Objectivity and Logic by Frederick Grinnell (Oxford)

God's Philosophers: How the Medieval World Laid the Foundations of Modern Science by James Hannam (Icon)

Life Ascending by Nick Lane (Profile)

We Need to Talk about Kelvin by Marcus Chown (Faber)

Why Does E=mc 2 ? by Brian Cox and Jeff Forshaw (Da Capo Press)

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• BOOKS AND ARTS
• 25 June 2019

James Lovelock at 100: the Gaia saga continues

• Tim Radford 0

Tim Radford was science editor of The Guardian until 2005. As a science journalist, he met and got to know James Lovelock. His latest book is The Consolations of Physics .

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James Lovelock proposes that Earth will be saved by artificial intelligence. Credit: Tim Cuff/Alamy

Novacene: The Coming Age of Hyperintelligence James Lovelock Allen Lane (2019)

James Lovelock will always be associated with one big idea: Gaia. The Oxford English Dictionary defines this as “the global ecosystem, understood to function in the manner of a vast self-regulating organism, in the context of which all living things collectively define and maintain the conditions conducive for life on earth”. It cites the independent scientist as the first to use the term (ancient Greek for Earth) in this way, in 1972.

On 26 July, Lovelock will be 100; his long career has sparkled with ideas. His first solo letter to Nature — on a new formula for the wax pencils used to mark Petri dishes — was published in 1945. But, unusually for a scientist, books are his medium of choice. He has written or co-authored around a dozen; the latest, Novacene , is published this month.

As that book’s preface notes, Lovelock’s nomination to the Royal Society in 1974 listed his work on “respiratory infections, air sterilisation, blood-clotting, the freezing of living cells, artificial insemination, gas chromatography and so on”. The “and so on” briefly referred to climate science, and to the possibility of extraterrestrial life. The story of Gaia began with a question posed by NASA scientists while Lovelock was a consultant at the Jet Propulsion Laboratory in Pasadena, California. That is, how could you tell if a planet such as Mars harboured life?

Final warning from a sceptical prophet

With microbiologist Lynn Margulis, Lovelock published a series of papers on the subject. In 1974, they developed a view of Earth’s atmosphere as “a component part of the biosphere rather than as a mere environment for life” ( J. E. Lovelock and L. Margulis Tellus 26 , 2–10; 1974 ). Earth’s atmosphere contains oxygen and methane — reactive gases, constantly renewed. That disequilibrium radiates an infrared signal, which Lovelock later described as an “unceasing song of life” that is “audible to anyone with a receiver, even from outside the Solar System”. Thus, the answer to NASA’s question was already written in the static Martian atmosphere, composed almost entirely of non-reactive carbon dioxide.

That was the beginning of a sustained and developing argument, in the face of sometimes dismissive criticism, that recast Earth as, in effect, a superorganism. Lovelock’s Gaia theory states that, for much of the past 3.8 billion years, a holistic feedback system has played out in the biosphere, with life forms regulating temperature and proportions of gases in the atmosphere to life’s advantage. Earth system science is now firmly established as a valuable intellectual framework for understanding the only planet known to harbour life, and increasingly vulnerable to the unthinking actions of one species. Colleagues and co-authors acknowledge that the argument continues, but endorse the importance of Lovelock and Margulis.

Entwined evolution

“The insight that the oceans and the atmosphere are thoroughly entwined with the living biosphere, and must be understood as a coupled system, has been completely vindicated,” says marine and atmospheric scientist Andrew Watson of the University of Exeter, UK. Lee Kump goes further. “Lovelock also showed us that Darwin had it only half right,” says Kump, a geoscientist at Pennsylvania State University in University Park. “Life evolves in response to environmental change, but the environment also evolves in response to biological change.” Despite severing formal links with universities decades ago, Lovelock has been showered with honorary degrees and awards from bodies as varied as NASA and the Geological Society of London.

The procession of engaging books began in 1979 with Gaia: A New Look at Life on Earth . Each volume made its case more forcefully than the last, exploring what was known first as the Gaia hypothesis, then simply as Gaia, and the hazards facing either the biosphere or humanity. The books include his endearing autobiography Homage to Gaia (2000), increasingly urgent warnings of climate devastation in The Revenge of Gaia (2006) and The Vanishing Face of Gaia (2009), and the less apocalyptic A Rough Ride to the Future (2014).

James Lovelock pictured in 1989. Credit: Terry Smith/The LIFE Images Collection/Getty

Novacene picks up from that note of hope, and showcases another big idea. Gaia might, after all, be saved — by the singularity. This artificial-intelligence takeover, which so alarms many doomsayers, will be our redemption. Lovelock argues that increasingly self-engineering cyborgs with massive intellectual prowess and a telepathically shared consciousness will recognize that they, like organisms, are prey to climate change. They will understand that the planetary thermostat, the control system, is Gaia herself; and, in tandem with her, they will save the sum of remaining living tissue and themselves. The planet will enter the Novacene epoch: Lovelock’s coinage for the successor to the informally named Anthropocene.

Lovelock welcomes this. “Whatever harm we have done to the Earth, we have, just in time, redeemed ourselves by acting simultaneously as parents and midwives to the cyborgs,” he writes. He takes the long view on this rescue, however. Climate change is a real threat to humanity, but Earth will inevitably be overtaken by a ‘big heat’ in a few billion years, as the Sun slowly waxes more fierce.

Although co-authored with journalist Bryan Appleyard, Novacene reads like undiluted Lovelock. From the start of his writing life — no matter how tortuous the narrative or complex the argument — Lovelock has written persuasively. In his debut, Gaia , he sidestepped evolution’s first and biggest obstacle (how to get from organic chemistry to a living, devouring, excreting, replicating organism) in two sentences that seem to me models of clarity and brevity: “Life was thus an almost utterly improbable event with almost infinite opportunities of happening. So it did.”

No place like home

In The Ages of Gaia (1988), a richer and more closely argued restatement, he answered the vexed question of how life contradicts the second law of thermodynamics. Life, he wrote, “has evolved with the Earth as a highly coupled system so as to favour survival. It is like a skilled accountant, never evading the payment of the required tax but also never missing a loophole.” This metaphoric brilliance is no rarity. A few pages on, he reminds us that Gaia is “a quarter as old as time itself. She is so old that her birth was in the region of time where ignorance is an ocean and the territory of knowledge is limited to small islands, whose possession gives a spurious sense of certainty.”

Lovelock’s Gaia theory is only one aspect of his nonconformism. His vigorous support for nuclear power annoys many environmentalists. Brought up as a Quaker, he registered as a conscientious objector in 1940, then changed his mind and prepared for military action in 1944 (the National Institute for Medical Research in London considered him more useful in the lab). Later, he became a consultant for the security services of Britain’s defence ministry. Among his inventions is an electron capture detector sensitive enough to identify vanishingly small traces of pollutants — such as the pesticides that spurred Rachel Carson to write the 1962 book Silent Spring — and chlorofluorocarbons, later implicated in damage to the ozone layer. In Novacene , he writes teasingly that he now sees himself as an engineer who values intuition above reason.

Lovelock to the last, he even has a kind word for the Anthropocene, marked by degradation of natural resources and the devastation of the wild things with which humanity evolved. He gives a “shout of joy, joy at the colossal expansion of our knowledge of the world and the cosmos”, and exults that the digital revolution ultimately “empowers evolution”. Is he right? Some of us might live to find out. In the meantime, if you want a sense of hyperintelligence in bipedal form, Novacene is a good place to start.

Nature 570 , 441-442 (2019)

doi: https://doi.org/10.1038/d41586-019-01969-y

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A Philosophical Look at Gaia

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Tim Lenton, A Philosophical Look at Gaia, BioScience , Volume 64, Issue 5, May 2014, Pages 455–456, https://doi.org/10.1093/biosci/biu041

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A generation ago, the Gaia hypothesis was simultaneously met with both an explosion of public popularity and an implosion of rejection by many in the scientific community. This rare occurrence is explained by Michael Ruse, professor of philosophy at Florida State University, in his entertaining and highly readable book The Gaia Hypothesis: Science on a Pagan Planet . The action centers on the 1970s and 1980s, but Ruse traces the underlying reasons for this schism back to Plato and two traditions of thought that began with the ancient Greeks. His aim is to show how our thinking today is deeply influenced by the past.

Gaia was the brainchild of James Lovelock; the idea was born in the mid-1960s out of the observation that Earth possesses a thermodynamically remarkable atmosphere that is also surprisingly stable in both its composition and its climate. Developed in the early 1970s in collaboration with the late Lynn Margulis, the Gaia hypothesis postulated that life and its planetary environment on Earth form a single system that self-­regulates in a habitable state. To many, the Gaia hypothesis represents a modern scientific incarnation of a very old idea that the Earth is, in some sense, alive—or at least that it behaves, in some ways, as an organism. Perhaps unsurprisingly, the main scientific objections to Gaia came from evolutionary biologists, who feel a strong sense of ownership over the concept of what defines an organism . How, they asked, could the Earth self-­regulate like an organism when it is not the product of evolution by natural selection among a population of reproducing planets?

Ruse's aim in The Gaia Hypothesis is to show that the heart of this disagreement was not a simple case of a new hypothesis's appearing to be at odds with established theory. Instead, it stretches back to the foundations of Western philosophy. The Gaia hypothesis, he explains, belongs to a long tradition of organicism , the philosophical position that the behavior of whole systems cannot be explained by the properties of their parts alone. By contrast, modern science has largely been a triumph of the tradition of reductionism (i.e., the idea that complex systems are no more than the sum of their parts), along with mechanism (i.e., natural wholes are essentially complicated machines).

Ruse expertly traces these two philosophical traditions from Plato through the scientific revolution to the time that Gaia hit the intellectual scene. He argues that the sturdy plant of organicist science has always been growing under the shadow of reductionism and that Gaia is simply a recent flowering of this. But the flowering of the Gaia hypothesis occurred at a particularly bad time, when evolutionary biologists were in the middle of trying to ensure that their theory did not imply that natural selection could act for the good of a group or of a species, let alone for the good of life as a whole.

The arrival of Gaia in the popular consciousness, however, fell on fertile ground. The embrace of Gaia by sectors of the public was, according to the author, part of a long history of hylozoism —the position that all matter, including the Earth, has life and value in its own right. This is the “pagan planet” of Ruse's subtitle, although he is careful to point out that the Gaia hypothesis does not go this far, except in the hands of some of its New Age devotees. He is curious enough, however, to have visited Oberon Zell-Ravenheart, cofounder of the Church of All Worlds and a writer and speaker on the subject of neopaganism, to find out more.

This is typical of Ruse's chatty and engaging style of writing. He treats his central characters with a healthy mixture of playfulness and respect. Perhaps Ruse's boldest proposition is that his two main protagonists, Lovelock and Margulis, actually belong to two different intellectual traditions. Lovelock, he claims, is a mechanist at heart, whereas Margulis was a true organicist. Ruse suggests that this can be seen in the way that each responded to the early criticisms of Gaia from evolutionary biologists: Lovelock produced a model—Daisyworld—to illustrate that a self-regulating mechanism could emerge automatically from life interacting with its environment, without any appeal to teleology. Daisyworld operates through a crude form of natural selection. Indeed, Lovelock has always been eager to demonstrate that Gaia is consistent with evolution by natural selection, whether his critics believe him or not. Margulis, however, loved nothing more than to goad evolutionary biologists. She argued that natural selection alone is not enough to explain the emergence of higher levels of biological organization. She believed that symbiogenesis was a crucial creative force and that Gaia was symbiosis as seen from space. Computer models such as Daisyworld left her unmoved.

Ruse's analysis has a ring of truth about it, but it would be wrong to infer that Lovelock is not an organicist. In my experience, Jim has a keen ability to intuit the behavior of whole systems, even if he cannot (at least at first) explain how they work in a mechanistic sense. This was true of his most famous invention, the electron capture detector, and is also true of Daisyworld. He conceived the model but only later wrote it in mathematical form with the help of Andrew Watson.

The value of Ruse's book is in how he captures the wider importance of the debate triggered by the Gaia hypothesis. Like all good philosophers, he makes the reader think about how we think. For example, when is it permissible to think in terms of parts having a purpose for the whole? We are not ridiculed for asking, “What is the purpose of the eye for the whole animal?” So, why is asking the purpose of nitrous oxide gas for the biosphere a laughing matter?

If I missed something from this work, it was a look at Gaia from a more contemporary scientific perspective. Ruse is writing as a historian of science, with the aim of understanding events that happened a generation ago. Unfortunately, this can create the erroneous impression that the Gaia hypothesis is a historical footnote that has led nowhere scientifically.

Many of the evolutionary biologists that Ruse discusses seem to be interested only in what can be explained through evolution by natural selection. Having convinced themselves that Gaia cannot be a product of natural selection, they have long since dismissed it. But climatologists and geochemists, for example, do not expect natural selection to explain how the planet functions. The Gaia hypothesis triggered them to think about the Earth as a system and about how life is intimately involved in feedback mechanisms that govern its behavior. As a result, a whole field of Earth system science has emerged.

Even the reductionist triumphs of molecular biology have led in some distinctly holistic directions. The genomics revolution is continually broadening our perspective on the mechanisms of life and of evolution, and those in the field of systems biology are attempting to understand the emergent properties of biological systems. Even one of Gaia's most insightful critics, W. Ford Doolittle, has argued that natural selection can happen through survival alone and, therefore, that Gaia and evolutionary theory could be reconciled (Doolittle 2013 ).

Now that the controversy that arose over the Gaia hypothesis is understood, we need to take a fresh look at it from a twenty-first century perspective of flourishing systems science. Has Gaia lost her relevance? I don't think so.

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Gaia theory: is it science yet?

Honorary Senior Associate, Faculty of Science, The University of Melbourne

Disclosure statement

Ian Enting does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

University of Melbourne provides funding as a founding partner of The Conversation AU.

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James Lovelock’s “ Gaia hypothesis ” has challenged conventional thinking about the nature of the earth as an integrated system. Gaia proposes that the earth acts like a living organism — that life is part of a self-regulating system, manipulating the physical and chemical environment to maintain the planet as a suitable home for life itself. Lovelock has developed this idea in a series of books, from “Gaia: A new look at life on earth” (1979) through to “Revenge of Gaia” (2006) and “The Vanishing Face of Gaia” (2009). He argues that as changes in the physical earth system occur, living systems respond so as to mitigate such changes.

How can a planet be alive?

In claiming that Gaia is “lifelike”, Lovelock notes the difficulty of defining life. He points out that a biological emphasis on (potential for) reproduction would, for example, exclude postmenopausal women. On the other hand, a physical emphasis on entropy reduction would include refrigerators. This leads Lovelock to emphasise physiological self-regulation as the defining characteristic of life-like systems - networks of interacting processes serve to regulate each other to preserve the functioning of the organism

In discussing the concept of Gaia, Lovelock now distinguishes:

Gaia hypothesis : the original version — the Earth’s organisms regulate the physical and chemical components of the earth system so as to maintain the planet as an optimal habitat for life.

Gaia theory : the revision in response to critics — the combined physical, chemical and biological components of the earth system regulate the planet so as to maintain it as a habitat for life.

Various analyses have tried to distinguish between “weak” and “strong” Gaia, with weak Gaia differing little from conventional earth system science.

But isn’t Gaia for hippies?

The name Gaia has been widely used as a metaphor, as well co-opted for a large amount of pseudo-scientific baggage. This does not invalidate any underlying science any more than the majority of physics is invalidated by similar appropriation of terms such as “relativity”, “crystals”, “force fields” etc.

After stripping away such baggage, one has to confront the question: is what Lovelock is saying science and mysticism? While Lovelock has used the term “geophysiology” to avoid some of the mystical associations, he notes that all that has been achieved is that the term geophysiology now carries the same suspicion as the name Gaia.

The confrontation between Gaian theory and “conventional” science is largely focused on a few key words: “Gaia is like a living organism … whose goal is to maintain the planet in state fit for life”.

A powerful argument against the Gaia hypothesis is the assertion (such as that made by Richard Dawkins in The Extended Phenotype ) that Gaia cannot arise from Darwinian evolution of life — the planet as a whole is not a unit of selection.

Dawkins can be answered by an anthropic argument (wherein observations of the physical universe must be compatible with the existence of the conscious life that observes it):

The emergence of Gaian self-regulation through the course of evolution is allegedly extremely improbable.

Nevertheless, the long-term survival of life on a planet without Gaian self-regulation may well be even more improbable.

Therefore, intelligent observers are most likely to find themselves on a planet with Gaian self-regulation.

Personally, I find this sort of argument unsatisfying. However, similar arguments seem to be needed to “explain” the physical universe — it is a very precise combination of physical constants that allows the existence of atoms heavier than hydrogen and helium. Anyway, if Gaian self-regulation has arisen by chance, one would still want to know how it works.

For me, one of the most intriguing possibilities is some form of “innate Gaia” — rather than being highly improbable, some degree of Gaian self-regulation is inevitable.

Writing in Nature Tim Lenton has proposed that if:

• the physical system is stable, and
• the biological system has self-increasing growth, and
• there is a physical optimum for growth

then the steady state will be whichever side of the optimum leads to negative feedbacks, thus enhancing the stability of the physical system. The “optimal for life” in the original Gaia hypothesis is replaced by “mutually enhanced stability of the physical and biological systems”.

A theory with gaps is still a theory

While Thomas Henry Huxley famously talked of “the slaying of a beautiful hypothesis by an ugly fact” such discrepancies can also mean that the “ugly facts” are being misinterpreted.

For example, the gap in Wegener’s account of continental drift was that the continents aren’t ploughing through the crust — they are being carried by the crust. The gap in Darwin’s argument 150 years ago was the implicit assumption of blending of characteristics, so that new traits would be diluted. Mendel’s experiments showed that this is not so. Working out the details has been the work of subsequent generations of population geneticists.

Returning to Dawkins’ argument as quoted above, the hidden assumption that may represent a weak point is the assumption of a single level of selection.

In Revenge of Gaia , Lovelock quotes William Hamilton: “Just as the observations of Copernicus needed a Newton to explain them, we need another Newton to explain how Darwinian evolution leads to a habitable planet.” This echoes Alfred Wegener: “The Newton of [continental] drift has not yet appeared. His absence need cause no anxiety.”

To summarise: gaps and discrepancies in a theory imply a case for serious further study, not necessarily a reason to panic and immediately abandon any consideration of the idea.

What does Gaia mean for humankind?

In his recent books, Lovelock argues that humanity is like an army with over-extended supply lines — there is no option but to retreat (allowing Gaia to recover). Depending on humanity’s choices the retreat could be comparable to the British from Dunkirk or Napoleon from Moscow. We can take control of population ourselves, or see it plummet as Gaia kills us off.

My interpretation of what Lovelock is proposing as the potential relation between Gaia and humanity is the 20th century concept of “Mutually Assured Destruction” rather than “revenge”.

These concerns seem to be based on Lovelock’s expectation of a third climate state. The last 500,000 years show an alternation between quasi-stable warm and cold states, flipping on a 100,000 year cycle.

Lovelock (using simple modelling described in Vanishing Face of Gaia) proposes that higher CO₂ will lead to a third, hotter, quasi-stable state. The proposed causal chain is: warming from more CO₂ → more stable oceans, less circulation → less nutrients at surface, so less algal production → less pumping of CO₂ into deep oceans → more CO₂ remains in the atmosphere, locking in the warming.

But is there real evidence for a “third climate state”? Apart from the general principle that once self-regulation of a system fails, the failure can be very abrupt, are the arguments really Gaian?

So does it work?

An “ideal” summary would answer the question: “Is Lovelock right? Does the Gaia concept describe how the earth works?” I hope you won’t be too disappointed if I fail to commit to an answer. Indeed the whole process of preparing my talk and then editing it for The Conversation would have been less fun if I had been working from a preconceived view.

At times Lovelock seems to equate “Gaia” with “earth system science” by asking “would you have bought The Vanishing Face of Earth System Science?” A more substantive question is to ask: “is the (strong) Gaia concept established science?”, to which the answer is “not yet, and maybe it never will be”.

We come back to the statement that for Gaia “we need another Newton…”. Would a complete theory be a matter of filling in the gaps, as 150 years of accumulating evidence has “filled in the details” in Darwinian evolution? Or would the survival of Gaian theory mean morphing into something different, in the way that continental drift morphed into plate tectonics?

My best guess is that if “strong” Gaian theory survives (with or without the name Gaia) it will be through some such similar transformation. The “innate Gaia” implied by negative feedbacks being an “automatic” consequence of an interaction between expanding life and a dissipative physical system may well be part of such a re-synthesis.

Assessing Lovelock’s role as a “key thinker” raises the question of whether, regardless of its validity, the Gaia hypothesis has had a positive influence on the development of earth system science. (Lovelock’s other contributions to science through instrumentation have been invaluable). If, as I do not, one equates Gaia to current earth system science then the question largely disappears — the implication is that the rest of science has caught up with Lovelock.

My view is that even though “strong Gaia” and probably “innate Gaia” currently lie beyond the boundaries of established science, Lovelock’s role in pushing the boundaries of thinking about the earth system has spurred the thinking of many in the emerging earth system science community. This is a valuable legacy, regardless of the ultimate fate of his ideas.

This article is based on a lecture delivered in April 2009 as part of The University of Melbourne series of public lectures on Key Thinkers.

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4.3: Gaia - Bioregulation of the Environment

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• Page ID 98746

• Stephen Lower
• Simon Fraser University

The Gaia Hypothesis

The physical conditions under which life as we know it can exist encompass a relatively narrow range of temperature, pH, osmotic pressure, and ultraviolet radiation intensity. It seems remarkable enough that life was able to get started at all; it is even more remarkable that it has continued to thrive in the face of all the perils that have, or could have occurred, during the past 3 billion years or so.

During the time that life has been evolving, the sun has also been going through the process of evolution characteristic of a typical star; one consequence of this is an increase in its energy output by about 30 percent during this time. If the sun’s output should suddenly drop to what it was 3 billion years ago, the oceans would freeze. How is it that the earth was not in a frozen state for the first 1.5 billion years of life’s existence? Alternatively, if conditions were somehow suitable 3 billion years ago, why have the oceans not long since boiled away?

A rather non-traditional answer to this kind of question is that the biosphere is far from playing a passive role in which it is continually at the mercy of environmental conditions. Instead, the earth’s atmosphere, and to a lesser extent the hydrosphere, may be actively maintained and regulated by the biosphere. This view has been championed by the British geochemist J.E. Lovelock, and is known as the Gaia hypothesis .

Gaia is another name for the Greek earth-goddess Ge , from which root the sciences of geography, geometry, and geology derive their names. Lovelock's book Gaia: a new look at life on Earth (Oxford, 1979) is a short and highly readable discussion of the hypothesis.

Evidence in support of this hypothesis is entirely circumstantial, but nevertheless points to important questions that must be answered: how have the climatic and chemical conditions on the earth remained optimal for life during all this time; how can the chemical composition of the atmosphere remain in a state that is tens of orders of magnitude from equilibrium?

Although the Gaia hypothesis has received considerable publicity in the popular press, it has never been very well received by the scientific community, many of whom feel that there is no justification for proposing a special hypothesis to describe a set of connections which can be quite adequately explained by conventional geochemical processes. More recently, even Lovelock has backed away from the teleological interpretation of these relations, so that the Gaia hypothesis should now be more properly described as a set of loosely connected effects, rather than as a hypothesis. Nevertheless, these effects and the mechanisms that might act to connect them are sufficiently interesting that it seems worthwhile to provide an overview of the major observations that led to the development of the hypothesis.

Teleology is the doctrine that natural processes operate with a purpose. See No longer willful, Gaia becomes respectable. 1988: Science 240 393-395.

Bioregulation of the Atmosphere

The increase in the oxygen content of the atmosphere as a result of the development of the eucaryotic cell was discussed above. Why has the oxygen content leveled off at 21 percent? It is interesting to note that if the oxygen concentration in the atmosphere were only four percent higher, even damp vegetation, once ignited by lightning, would continue to burn, enveloping vast areas of the earth in a firestorm. Evidence for such a worldwide firestorm that may be related to the extinction of the dinosaurs has recently been discovered. The charcoal layers found in widely distributed sediments laid down about 65 million years ago are coincident with the iridium anomaly believed to be due to the collision of a large meteor with the earth.

• Oxygen : Regulation of the oxygen partial pressure is probably achieved by a balance between its production through photosynthesis and its consumption during oxidation of organic matter; the present steady state requires the burial of about 0.1% the carbon that is fixed annually, leaving one O 2 molecule in the air for each atom of carbon removed from the photosynthetic cycle. The large quantities of microbially-produced methane and N 2 O also constitute important oxygen sinks; if methanogenic bacteria should suddenly cease to exist, the O 2 concentration would rise by 1% in about 12,000 years. This type of regulation implies a negative feedback mechanism, in which an increase in atmospheric oxygen would increase the activity of organisms capable of generating metabolic products that react with it.
• Nitrous oxide : Nitrous oxide, in addition to serving as an oxygen sink, might also be a factor in the regulation of the intensity of the ultraviolet component of sunlight. N 2 O acts as a catalytic intermediate in the decomposition of stratospheric ozone, which shields the earth from excessive ultraviolet radiation.
• Ammonia : Ammonia, another atmospheric gas, is produced by the biosphere in approximately the same quantities as methane, 10 9 tons per year, and at the expense of a considerable amount of metabolic energy. The function of NH 3 could well be to regulate the pH of the environment; in the absence of ammonia, the large amounts of SO 2 and HCl produced by volcanic action would reduce the pH of rain to about 3. The fact that the atmospheric concentration of ammonia is only 10 –8 times that of N 2 should not imply that this “trace” component plays a less significant role in the overall nitrogen cycle than does than N 2 . In fact, the annual rates of production of the two gases are roughly the same; the much lower steady-state concentration of NH 3 is due to its faster turnover time.
• Nitrogen : As stable as the triply-bonded N 2 molecule is, there is a still more stable form of nitrogen: the hydrated nitrate ion. How is this stability consistent with the predominance of nitrogen in the atmosphere? The answer is that it is not: if it were not for nitrogen-fixing bacteria (powered directly or indirectly by the free energy of ATP captured from sunlight), the nitrogen content of the atmosphere would disappear to almost zero. This would raise the oxygen fraction to disastrously high levels, and the additional NO 3 – concentration would increase the ionic strength and osmotic pressure of seawater to levels inconsistent with most forms of life.

Bioregulation of the Oceans

The input of salts into the sea from streams and rivers is about 5.4 x 10 8 tons per year, into a total volume of about 1.2 x 10 9 km 3 yr –1 . Upwelling of juvenile water and hydrothermal action at oceanic ridges provide additional inputs of salts. With a few bizarre exceptions such as the brine shrimp and halophilic bacteria, 6 percent is about the maximum salinity level that organisms can tolerate. The internal salinities of cells must be maintained at much lower levels (around 1%) to prevent denaturation of proteins and other macromolecules whose conformations are dependent on electrostatic forces. At higher levels than this, the electrostatic interaction between the salt ions and the cell membrane destroys the integrity of the latter so that it can no longer pump out salt ions that leak in along the osmotic gradient. At the present rate of salt input, the oceans would have reached their present levels of salinity millions of years ago, and would by now have an ionic strength far to high to support life, as is presently the case in the landlocked Dead Sea.

The present average salinity of seawater is 3.4 percent. The salinity of blood, and of many other intra- and intercellular fluids in animals, is about 0.8 percent. If we assume that the first organisms were approximately in osmotic equilibrium with seawater, then our body fluids might represent “fossilized” seawater as it existed at the time our predecessors moved out of the sea and onto the land.

By what processes is salt removed from the oceans in order to maintain a steady-state salinity? This remains one of the major open questions of chemical oceanography. There are a number of answers, mostly based on strictly inorganic processes, but none is adequately supported by available evidence. For example, Na + and Mg 2 + ions could adsorb to particulate debris as it drops to the seafloor, and become incorporated into sediments. The requirement for charge conservation might be met by the involvement of negatively charged silicate and hydroxyaluminum ions. Another possible mechanism might be the burial of salt beds formed by evaporation in shallow, isolated arms of the sea, such as the Persian Gulf. Extensive underground salt deposits are certainly found on most continents, but it is difficult to see how this very slow mechanism could have led to an unfluctuating salinity over shorter periods of highly variable climatic conditions.

The possibility of biological control of oceanic salinity starts with the observation that about half of the earth’s biomass resides in the sea, and that a significant fraction of this consists of diatoms and other organisms that build skeletons of silica. When these organism die, they sink to the bottom of the sea and add about 300 million tons of silica to sedimentary rocks annually. It is for this reason that the upper levels of the sea are undersaturated in silica, and that the ratio of silica to salt in dead salt lakes is much higher than in the ocean.

These facts could constitute a basis for a biological control of the silica content of seawater; any link between silica and salt could lead to the control of the latter substance as well. For example, the salt ions might adsorb onto the silica skeletons, and be carried down with them; if the growth of these silica-containing organisms is itself dependent on salinity, we would have our negative feedback mechanism.

The continual buildup of biogenic sedimentary deposits on the ocean floor might possibly deform the thin oceanic crust by its weight, and cause local heating by its insulating properties. This could conceivably lead to volcanic action and the formation of new land mass, thus linking the lithosphere into Gaia.

Contributors and Attributions

Stephen Lower, Professor Emeritus ( Simon Fraser U. ) Chem1 Virtual Textbook

ENVS203: Environmental Ethics, Justice, and World Views

The gaia hypothesis.

Read this page, which discusses the Gaia hypothesis. Do you believe that the theory holds weight, and that we could observe some of impacts as outlined in the hypothesis?

This teaching unit begins with a conceptual sketch of the Gaia Hypothesis, followed by a way of thinking about teaching found in John Dewey's philosophy of education that meets the challenge of Gaia in the classroom. There follows an outline of how Dewey unites scientific and moral problem solving for developing social policy which is, in turn, made applicable to solving problems in the environment. These ideas are translated into lesson plans, a course outline to integrate the unit into a course in ecology and biodiversity, and finally, analytical scoring rubrics.

1. The Gaia Hypothesis

Up until the last decade, few had thought of planet earth as in any sense alive. True in ancient Greece, Gaia was worshipped as the Goddess of the earth and pantheistic tribes had comparable deities of the earth that magically controlled their lives. An important step in this direction came from ecology where self-sustaining systems were discovered in which energy flowed and a delicate balance was maintained between all the organisms in the local environment. A meadow, a pond, or a forest were described as ecosystems. The abiotic factors were the inorganic or nonliving entities essential to the biotic factors or community of life that sustained each other – the producers, the consumers, and decomposers. Subseguently, James Lovelock in his Gaia Hypothesis suggests that the entire earth is one large ecosystem, homeostatically controlled. Furthermore, he shows that the environment was both created to meet life's needs as much as it has adapted to the conditions of the environment. Indeed life and the non-living are inseparable entities rather as the mind is to the body (1). It was more correct to say that the earth as a whole is self-sustaining, self-renewing, and self-creating. The earth is a living planet. Since life is sacred and encompasses both the biotic and the abiotic, the term Gaia seemed appropriate for the living earth.

We are used to the adage "think globally and act locally". Gaian thinking is really this idea in the fullest sense of its meaning. It is thinking through policies of management of the earth as a whole and to look at all other problems as subsets of this. It is a cybernetic approach to global village management where the problem is basically humans and culture, not nature. It is recognition that in our rape of mother earth, Gaia may dispose of us in the process of a planetary self-correcting homeostatic mechanism before we get to destroy Gaia.

As James Lovelock points out in 'Ages of Gaia', the central concept in the Gaia Hypothesis is homeostasis in which microbes, plants, soil organisms, and aquatic life play an integrated role. They control the flow of carbon, nitrogen, water, and other elements that go to make up life – with the sun turning the cycles at the homeostatically corrected temperature for life and by life. Life started taking control of the environment with the development of the double-helical nucleotides and these genes have driven the experiment of life with the environment as its encompassing cloak. (2)

The key example worked out by Lovelock was thermostatic control of the earth's surface temperature. He used the 'Daisy World' model as theoretical construct to demonstrate his theory. In simple outline, Gaia Hypothesis attributes the creation of earth's peculiar atmosphere to

(A) the stratospheric Carbon Dioxide blanket. When thick temperatures rise; when thin it cools. The ocean acts as a sink for Carbon Dioxide along with the rocks. Trees and cyanobacteria also absorb the gas and generate moisture. The Carbon Dioxide blanket above the stratosphere also keeps the oceans from evaporating away.

(B) For surface temperature to be around 13 degrees Celcius, the preferred average temperature for planetary life, it is necessary to have a correct mix of atmospheric gases. Air has the correct balance of 79% Nitrogen, 20% Oxygen and 0.003% Carbon Dioxide (all other planets have very high Carbon Dioxide and minimal Nitrogen and Oxygen). The Oxygen content comes from photosynthetic activity, the Nitrogen from decomposers (protists, fungi and bacteria). Oxygen forms ozone in the ionosphere and neutralizes ultraviolet radiation to protect life.

(C) The luminosity of the earth is lower and controlled by forest and vegetation (micro/macroflora) on land and in the oceans. When darker the temperature cools and when light the temperature rises (the Albedo factor). (3)

The gene flow of information that we call life, to an evolving experimentation problem-solving creation and adaptation to the environment, has an exponential history of development. It is Gaia's own self-development leading from the origin of the universe as bare energy leading up to higher levels of awareness. The levels of Gaia may be represented in powers of 10 from 4.5 billion years ago to the present generation born 45 years ago. The boxes are different by x10 to the power of 2 years. In the final box we have the highest level of self-awareness, a level that has the power to destroy Gaia – see the diagram opposite and the graph above it describing another exponential development, the human population explosion. We humans, though having evolved to an unprecedented level of self-awareness, have become a cancerous growth – a part of Gaia that is reproducing itself uncontrollably and fast killing its living host – Gaia.

It is the point of view of this teaching unit that Gaia protection is the fundamental starting point for all problem-solving in the environment. Norman Myers points out in "Atlas of Future Worlds", that protection of Gaia needs to be embedded in international law and all human behavior subjected to such a law (4). All other environmental and human problems pale by comparison. Accepting the axiom of the inviolability of Gaia would also help prioritize and suggest acceptable solutions to environmental problems, many of which are being sidetracked because of lack of agreement about what constitutes environmental moral culpability. The following unit then takes this as its a priori and seeks to involve students in the Gaia principle in any and every environmental problem that concerns them. Before developing the practicalities of such an undertaking, it seems necessary that we rethink our pedagogy to make sure that it is adequate to deal with the holistic mode of thinking required by the Gaia hypothesis, and rethinking John Dewey's educational philosophy is our place to begin.

2. Gaia and Education

John Dewey has had a profound influence on American education. The present reforms in science education are almost pure Deweyan. Those earlier reforms instituted in his name were not as successful as hoped but with research and creativity, the integrity of his ideas have been practically realized. However, the fundamentals of his philosophy of education have far-reaching implications that this unit seeks to include.

The first significant relevance is Dewey's own all-encompassing metaphor that he carried to all his ideas about education i.e. the metaphor of life itself. Life is self-renewing, self-adaptive, systemic, and social; hence education must have these characteristics to be effective.

"The most notable distinction between living things and inanimate things is that the former maintain themselves by renewal".(5) Education is such a process of renewal and transmission of resources that also includes ideas, skills, and so forth for the purpose of continuing life in the environment. Education communicates habits (skills) in doing, thinking, and feeling from generation to generation. The whole range of life's experience is passed on to individuals that enlarges their private experience. The individual 'goes out' of the self to find points of contact with that wider experience, the life of the species. (6)

Education manipulates meanings that have been called for by the need to interact and solve problems, those problems given by history, the present, and the challenge of the future. The ability to respond is natural to us – not an extrinsic capacity to be forced on the unwilling. It is not an act of conditioning but learning to see how ideas come together in a dynamic interplay to achieve some goal. The example Dewey gives to make his point is a baseball game. The game cannot be taught by memorizing rules or sequences of events. These may be used in the process of learning the game, but nothing is learned until the idea of the game is learned. Each of the parts have to come together so that it all makes sense. The test is whether the information works for the individual and they can be creatively used. When this is achieved the individual can demonstrate it and see how all the parts of the game are systemically interconnected to achieve the goal of winning and so forth. In this unit, problems will be thought through in such a 'feedback' loop.

At the heart of education is the idea of growth and this is equally characteristic of life as it moves from inception to death. Dewey's key ideas in this respect are 'reorganizing, reconstructing and transformation'.

Education by contrast is not static and not extrinsic. It is about taking the past into the future with thought, inventiveness and initiative.(7) Gaia problem solving challenges us all to break out of the static 'business as usual' ways of thinking.

The relevance to Gaian thought is that education must be taken out of its abstract and past orientation so as to apply past knowledge to the present and future. We need to move out of the Newtonian universe and move into the contemporary world of nonlinear physics, holistic math, creative chaos, and global cultural dialogue. Education must transcend meeting the interests of the status quo, class (business) privilege, or nationalist self-interest, for the purposes of all life, all of humanity, and for responding creatively to the environment. (8)

As Gaia is sacred and has its own ends and meanings, so also education provides its own interests, its own intrinsic ends. What is intrinsic, however, is open-ended, flexible, responsive, a shared activity, personal, and problem-solving. It is intelligent and springs from the student's own natural intelligence. It is its own discipline.

Dewey does not equate education with mere biological life but with reflective thought within the biological process of living in the environment. The essence of education is thinking within experience. Intelligence is not limited to humans. Humans are more adapted to finding a reflective solution to an environmental problem. Reflective experience or intelligent thought may be summarized as follows and is clearly a generalized scientific way of thinking that can be applied to any kind of experience of any kind.

perplexity, doubt, confusion in a situation (a problem/question) a tentative interpretation (hypothesis, projected answer) a careful detailed survey or examination of the experience (observations to clarify the problem) hypothesis (rational explanation) stated with independent variables (causes) and dependent variables (effects) test the explanation by effecting a cause to produce an effect or in other words, live the thought within an experience to see if it gives integrity or coherence to the event. (9)

Methodology in teaching is then no more nor less than the method of intelligent thinking. Students cannot learn this unless they participate in an event that requires active reflection. It cannot be isolated from the world but part and parcel of an action that becomes part of a growing world of experience. Books bring that accumulation of global experience to the student but it has to become a direct experience to become meaningful. The task of the teacher is to help mediate 'universal' and private experience.

In Dewey's major opus 'Democracy and Education', he elaborates the above in terms of the various disciplines – geography, history, humanities, science, and so forth (10). He also apples it to the social spirit, the essence of morality. In the following teaching unit, we will focus more of the implication of his educational theory to ethics and problem solving, particularly as they relate to environmental crises of Gaian proportions. The relevance of Dewey's pedagogy above will be highlighted too.

3. Developing a Social Policy

From the reasoning above, a teaching methodology will develop out of the steps needed to think intelligently when confronted by some aspect of the environment that we experience or live in. It is essentially scientific but since we are developing social policy we are also operating at a moral level of reasoning. Can such a methodology work for moral reasoning? In my teaching unit on genetics (YNHTI 1996), I set out Dewey's arguments for the appropriateness of scientific reasoning when making ethical judgments. His key justifications are as follows:

Moral judgments, as science, deals with time and space since both concern antecedents and consequences. In both science and morality, universals are abstracted out of particular events and actual contexts. Both concern universal 'laws' that only mean anything as predicators in actual situations. Science and morality both concern judgments on experiences that require reflection and then action to test theoretical understandings. These are tested as events involving some action, the results of which are used to confirm or deny the validity of the prior reflections and judgments. Science demands that reason be subjected to the hard knocks of experience. Similarly morality must justify itself in terms of actual experienced problems. Neither can hide behind appeals to transcendence independent of experience if they are to claim to be true. Both science and morality involve feeling awareness, rational cognition and action to test validity of the relationship between feeling and thought. Feeling awareness in both science and morality is attention to some aspect of the immediacy of experience that calls forth sentient interest, goals and vision of possibilities (in morality, love is an example of this). Cognition consists of logical connections in experience based on cause and effect. Objective thought in morality and science comes from acting out this reasoning within the environment (in morality, moral principles are reasoning within an experience such as love). If the consequences of action meet those expected by reason and those desired by the original feeling awareness (that drew one's attention to this aspect of the environment in the first place) then both science and morality have reasonable grounds for objectivity. Since methodology of making scientific and moral judgments are analogous, then the use of the following scientific or intelligent method of making social policies to solve problems in the environment are legitimated.

To simplify the above, we may use the life-skills problem-solving schema described below that all teachers in New Haven Public Schools are expected to use, where applicable, across all academic disciplines. What follows is a practical application of this applied to the population crisis.

(i) Defining the Problem

a. Population is the root cause of pollution and since population increases exponentially so pollution is increasing exponentially and so necessarily uncontrollably.

b. Pollution of air, water, and soil means loss of available resources for the expanding population.

c. Population drives consumption that depletes resources and prevents a balanced or sustainable economy with the environment. It drives the need for synthetics and the need for garbage disposal that further pollutes and cuts back on available land and resources.

d. Population increase drives the need to use mass farming techniques such as mono-genetic crops and pesticides that only increases productivity of crop production in the short term. It increases the risk of loss of protection from pests in the future and toxicity to life in general. In the process, further environmental damage threatens the existing level of human population.

e. Population increase means reduction of forests to provide fuel and more cultivated land, more houses and recreational space, etc. Loss of forests threatens global homeostatic control of global temperature.

If the temperature goes up there is flooding and increased rate of desertification, if the temperature goes down, there is a movement towards a glacial age. In either case, there is more land lost to farming.

f. Increase in population means increased dependence upon oil and other imported goods that decreases national security and so increases military expenditure that reduces resources available for feeding the population etc

g. Increase in population ultimately threatens all environmental treaties because the struggle for survival will justify governments to abandon them, that then in turn may lead to qualitative leaps in environmental destruction, and as such possibly lead to death of Gaia or devastating loss of human life to levels below existing population.

(ii) Hypothetical Solutions

a) Give tax and social benefits as incentives to 2 children families and penalties for exceeding this number.

b) Require all synthetics to be either biodegradable or able to be recycled on a sustainable basis.

c) Agribusiness must justify all management and farming policies based upon long term sustainable policies, organic solutions to pest and preservation of genetic diversity in the environment.

d) Enforcement of 'greenbelts' around all forest and woodlands. Cutting of trees must not threaten a complex ecosystem in which they live.

e) Reduce dependence upon foreign imports to reduce military expenditure. Reduce foreign debt by limiting profits that can be made on loans.

f) Support an international economic order that requires foreign trade to be based upon the best use of natural resources consistent with local climate or distinctive biome needs.

g) Give priority to all plans that address issues solving systemic problems.

(iii) Determine what criteria would be used to deem plans/solutions as good/bad or better/worse. (controlling variables).

The task is now to anticipate consequences of the hypothetical solutions that have been imagined. In this case, we are interested in:

• outcomes for the government, state or wider community material or nonmaterial.
• outcomes for those immediately involved.
• outcomes for extended family and others directly affected.
• anticipated outcomes based upon research into comparable situations, for example China.
• anticipate costs to different sectors of the economy and ways to deal with this.

(iv) Procedure/Materials/Presentation of Data.

Choose the best hypothetical plan and fully write out how it would be implemented with list of resources and costs incurred. Plan data tables, graphs, and so forth to determine how outcomes can be measured and presented.

(v) Conclusion

Recommend implementing the plan that appears to offer the best outcomes. Point out limitations and expected arrears for refinement.

Saylor Academy Knowledge Check

The Gaia Hypothesis: Conjectures and Refutations

• Published: May 2003
• Volume 58 , pages 21–45, ( 2003 )

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• James W. Kirchner 1  

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The uncertainties surrounding global climate change provide ample evidence, if any were necessary, of the need for a whole-system view of the Earth. Arguably the most visible – and controversial – attempt to understand Earth as a system has been Lovelock's Gaia theory. Gaia has been a fruitful hypothesis generator, and has prompted many intriguing conjectures about how biological processes might contribute to planetary-scale regulation of atmospheric chemistry and climate. In many important cases, however, these conjectures are refuted by the available data. For example, Gaia theory predicts that the composition of the atmosphere should be tightly regulated by biological processes, but rates of carbon uptake into the biosphere have accelerated by only about 2% in response to the 35% rise in atmospheric CO 2 since pre-industrial times. Gaia theory would predict that atmospheric CO 2 should be more sensitively regulated by terrestrial ecosystem uptake (which is biologically mediated) than by ocean uptake (which is primarily abiotic), but both processes are about equally insensitive to atmospheric CO 2 levels. Gaia theory predicts that biological feedbacks should make the Earth system less sensitive to perturbation, but the best available data suggest that the net effect of biologically mediated feedbacks will be to amplify, not reduce, the Earth system's sensitivity to anthropogenic climate change. Gaia theory predicts that biological by-products in the atmosphere should act as planetary climate regulators, but the Vostok ice core indicates that CO 2 , CH 4 , and dimethyl sulfide – all biological by-products – function to make the Earth warmer when it is warm, and colder when it is cold. Gaia theory predicts that biological feedbacks should regulate Earth's climate over the long term, but peaks in paleotemperature correspond to peaks in paleo-CO 2 in records stretching back to the Permian; thus if CO 2 is biologically regulated as part of a global thermostat, that thermostat has been hooked up backwards for at least the past 300 million years. Gaia theory predicts that organisms alter their environment to their own benefit, but throughout most of the surface ocean (comprising more than half of the globe), nutrient depletion by plankton has almost created a biological desert, and is kept in check only by the nutrient starvation of the plankton themselves. Lastly, where organisms enhance their environment for themselves, they create positive feedback; thus Gaia theory's two central principles – first, that organisms stabilize their environment, and second, that organisms alter their environment in ways that benefit them – are mutually inconsistent with one another. These examples suggest that the further development of Gaia theory will require more deliberate comparison of theory and data.

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Kirchner, J.W. The Gaia Hypothesis: Conjectures and Refutations. Climatic Change 58 , 21–45 (2003). https://doi.org/10.1023/A:1023494111532

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Animal behaviourist weighs in on Bluey fan theory about why dogs seem to enjoy watching too

When Madeline Carpou needs the family dog Lilliput to sit still and chill, she reaches for the remote control and turns on Bluey.

Ms Carpou stumbled upon her pup's love for  the ABC's beloved blue heeler when a dog-sitting date at her parents' place clashed with an outing with friends.

To keep Lilliput company while she was gone, Ms Carpou popped on a 24/7 Bluey marathon and gave her a chewy treat. 

She returned around five hours later to a very contented dog.

"She greeted me as usual then went straight back to the couch to get back to Bluey and her treat," Ms Carpou said. 

"We watched it together for 30 minutes — she was totally zoned in." 

Mary Bolling's labradoodle River is another big fan of the show, but growing up in the home of a Bluey fanatic , he had no real choice in the matter.

According to his owner, the excitable two-year-old pup is calmest when seated with family in front of the screen.

"I definitely count it as one of his favourite programs," Ms Bolling said. 

Bluey in high definition

A viral social media theory, originating on TikTok,  suggests Bluey uses colours that dogs can see well , which is why they are drawn to the show.

But can science really explain River and Lilliput's behaviour?

Kate Mornement, an applied animal behaviourist in regional Victoria, said contrary to popular belief, "dogs are not necessarily colour blind".

"But they are restricted to only seeing shades of grey, brown, yellow and blue," she told ABC Victorian Mornings .

"It's because they have less [colour-sensing] cones in their eyes compared to humans, so they see a few less colours."

While Bluey's colour palette is heavy on the blues, yellows and browns dogs can see, Dr Mornement offers another theory about why some dogs may appear to enjoy the cartoon.

"It's a phenomenon — dogs watching TV — that's increased in recent years, and the reason is … high-definition TV.

"[Its] invention … has made it much easier for dogs to see the images on the screens, and so that's why they tend to be more interested these days than years gone past."

So, can dogs following what's happening on screen or are they just watching shapes?

"I've seen some really interesting videos on social media of dogs watching TV in different contexts, and they tend to be a lot more interested when it's animals that they're watching," Dr Mornement said.

"Some dogs are intrigued and you might see them cock their heads and stare at the TV, and other dogs … might be really scared or anxious and they'll start barking.

"I've even helped clients with dogs that might jump up at the TV really aggressively because they were scared … of what they were seeing."

What do Bluey's creators say?

In a very tongue-in-cheek statement, Ludo Studio, the creatives behind the series, said the discovery that dogs were not colourblind had "created an exciting creative and business opportunity" for the show.

"It is for these reasons that Bluey's lead art designers collaborated with Queensland scientists during development and pre-production in the hope we might create a series with a colour palette and certain storylines as appealing to dogs as they were to parents and children," the studio said in jest.

So, with studios now creating programs in colours that are "appealing to dogs", do we need to start moderating puppy screen time? 

"Look, everything in moderation, just like with children, is fine," Dr Mornement laughed.

"A little TV every now and then for the dog — as long as it's not causing anxiety —  is totally fine."

It's good news for canine Bluey fans, as the ABC is set to air a 28-minute special of the cartoon — called The Sign — this Sunday.

The extra-long release comes fresh off the heels of an episode titled Ghostbasket, released last weekend, which (spoiler alert) ends with a cliffhanger: the Heelers' house has hit the real estate market.

Stream the new Bluey episode Ghostbasket on ABC iview now , and catch Bluey's 28-minute special The Sign at 8am on April 14  on ABC iview .

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