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  • richardmitnick 8:40 am on July 5, 2018 Permalink | Reply
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    From Science Alert: “These Scientists Have a Tantalising New Answer to The Mysterious ‘Gaia Puzzle’ “ 


    From Science Alert

    5 JUL 2018

    (Louis Maniquet/Unsplash)


    We will likely never know how life on Earth started. Perhaps in a shallow sunlit pool.

    Or in the crushing ocean depths miles beneath the surface near fissures in the Earth’s crust that spewed out hot mineral-rich soup. While there is good evidence for life at least 3.7 billion years ago, we don’t know precisely when it started.

    But these passing aeons have produced something perhaps even more remarkable: life has persisted.

    Despite massive asteroid impacts, cataclysmic volcano activity and extreme climate change, life has managed to not just cling on to our rocky world but to thrive.

    How did this happen? Research we recently published with colleagues in Trends in Ecology and Evolution offers an important part of the answer, providing a new explanation for the Gaia hypothesis.

    Developed by scientist and inventor James Lovelock, and microbiologist Lynn Margulis, the Gaia hypothesis originally proposed that life, through its interactions with the Earth’s crust, oceans, and atmosphere, produced a stabilising effect on conditions on the surface of the planet – in particular the composition of the atmosphere and the climate.

    With such a self-regulating process in place, life has been able to survive under conditions which would have wiped it out on non-regulating planets.

    Lovelock formulated the Gaia hypothesis while working for NASA in the 1960s. He recognised that life has not been a passive passenger on Earth.

    Rather it has profoundly remodelled the planet, creating new rocks such as limestone, affecting the atmosphere by producing oxygen, and driving the cycles of elements such as nitrogen, phosphorus and carbon.

    Human-produced climate change, which is largely a consequence of us burning fossil fuels and so releasing carbon dioxide, is just the latest way life affects the Earth system.

    While it is now accepted that life is a powerful force on the planet, the Gaia hypothesis remains controversial. Despite evidence that surface temperatures have, bar a few notable exceptions, remained within the range required for widespread liquid water, many scientists attribute this simply to good luck.

    If the Earth had descended completely into an ice house or hot house (think Mars or Venus) then life would have become extinct and we would not be here to wonder about how it had persisted for so long.

    This is a form of anthropic selection argument that says there is nothing to explain.

    Clearly, life on Earth has been lucky. In the first instance, the Earth is within the habitable zone – it orbits the sun at a distance that produces surface temperatures required for liquid water.

    There are alternative and perhaps more exotic forms of life in the universe, but life as we know it requires water. Life has also been lucky to avoid very large asteroid impacts.

    A lump of rock significantly larger than the one that lead to the demise of the dinosaurs some 66 million years ago could have completely sterilised the Earth.

    But what if life had been able to push down on one side of the scales of fortune? What if life in some sense made its own luck by reducing the impacts of planetary-scale disturbances?

    This leads to the central outstanding issue in the Gaia hypothesis: how is planetary self-regulation meant to work?

    While natural selection is a powerful explanatory mechanism that can account for much of the change we observe in species over time, we have been lacking a theory that could explain how the living and non-living elements of a planet produce self-regulation.

    Consequently the Gaia hypothesis has typically been considered as interesting but speculative – and not grounded in any testable theory.

    Selecting for stability

    We think we finally have an explanation for the Gaia hypothesis. The mechanism is “sequential selection”. In principle it’s very simple.

    As life emerges on a planet it begins to affect environmental conditions, and this can organise into stabilising states which act like a thermostat and tend to persist, or destabilising runaway states such as the snowball Earth events that nearly extinguished the beginnings of complex life more than 600 million years ago.

    If it stabilises then the scene is set for further biological evolution that will in time reconfigure the set of interactions between life and planet. A famous example is the origin of oxygen-producing photosynthesis around 3 billion years ago, in a world previously devoid of oxygen.

    If these newer interactions are stabilising, then the planetary-system continues to self-regulate. But new interactions can also produce disruptions and runaway feedbacks.

    In the case of photosynthesis it led to an abrupt rise in atmospheric oxygen levels in the “Great Oxidation Event” around 2.3 billion years ago.

    This was one of the rare periods in Earth’s history where the change was so pronounced it probably wiped out much of the incumbent biosphere, effectively rebooting the system.

    The chances of life and environment spontaneously organising into self-regulating states may be much higher than you would expect.

    In fact, given sufficient biodiversity, it may be extremely likely. But there is a limit to this stability.

    Push the system too far and it may go beyond a tipping point and rapidly collapse to a new and potentially very different state.

    This isn’t a purely theoretical exercise, as we think we may able to test the theory in a number of different ways. At the smallest scale that would involve experiments with diverse bacterial colonies.

    On a much larger scale it would involve searching for other biospheres around other stars which we could use to estimate the total number of biospheres in the universe – and so not only how likely it is for life to emerge, but also to persist.

    The relevance of our findings to current concerns over climate change has not escaped us. Whatever humans do life will carry on in one way or another.

    But if we continue to emit greenhouse gasses and so change the atmosphere, then we risk producing dangerous and potentially runaway climate change.

    This could eventually stop human civilisation affecting the atmosphere, if only because there will not be any human civilisation left.

    The ConversationGaian self-regulation may be very effective. But there is no evidence that it prefers one form of life over another. Countless species have emerged and then disappeared from the Earth over the past 3.7 billion years.

    We have no reason to think that Homo sapiens are any different in that respect.

    See the full article here .


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  • richardmitnick 5:30 am on June 28, 2016 Permalink | Reply
    Tags: , Gaia Theory, ,   

    From U Cambridge: “Super-slow circulation allowed world’s oceans to store huge amounts of carbon during the last ice age” 

    U Cambridge bloc

    Cambridge University

    27 Jun 2016
    Sarah Collins
    Communications office

    Foraminifera “Star sand” Hatoma Island – Japan Credit: Psammophile

    The way the ocean transported heat, nutrients and carbon dioxide at the peak of the last ice age, about 20,000 years ago, is significantly different than what has previously been suggested, according to two new studies. The findings suggest that the colder ocean circulated at a very slow rate, which enabled it to store much more carbon for much longer than the modern ocean.

    Using the information contained within the shells of tiny animals known as foraminifera, the researchers, led by the University of Cambridge, looked at the characteristics of the seawater in the Atlantic Ocean during the last ice age, including its ability to store carbon. Since atmospheric CO2 levels during the period were about a third lower than those of the pre-industrial atmosphere, the researchers were attempting to find if the extra carbon not present in the atmosphere was stored in the deep ocean instead.

    They found that the deep ocean circulated at a much slower rate at the peak of the last ice age than had previously been suggested, which is one of the reasons why it was able to store much more carbon for much longer periods. That carbon was accumulated as organisms from the surface ocean died and sank into the deep ocean where their bodies dissolved, releasing carbon that was in effect ‘trapped’ there for thousands of years. Their results are reported in two separate papers in Nature Communications.

    The ability to reconstruct past climate change is an important part of understanding why the climate of today behaves the way it does. It also helps to predict how the planet might respond to changes made by humans, such as the continuing emission of large quantities of CO2 into the atmosphere.

    The world’s oceans work like a giant conveyer belt, transporting heat, nutrients and gases around the globe. In today’s oceans, warmer waters travel northwards along currents such as the Gulf Stream from the equatorial regions towards the pole, becoming saltier, colder and denser as they go, causing them to sink to the bottom. These deep waters flow into the ocean basins, eventually ending up in the Southern Ocean or the North Pacific Ocean. A complete loop can take as long as 1000 years.

    “During the period we’re looking at, large amounts of carbon were likely transported from the surface ocean to the deep ocean by organisms as they died, sunk and dissolved,” said Emma Freeman, the lead author of one of the papers. “This process released the carbon the organisms contained into the deep ocean waters, where it was trapped for thousands of years, due to the very slow circulation.”

    Freeman and her co-authors used radiocarbon dating, a technique that is more commonly used by archaeologists, in order to determine how old the water was in different parts of the ocean. Using the radiocarbon information from tiny shells of foraminifera, they found that carbon was stored in the slowly-circulating deep ocean.

    In a separate study led by Jake Howe, also from Cambridge’s Department of Earth Sciences, researchers studied the neodymium isotopes contained in the foraminifera shells, a method which works like a dye tracer, and came to a similar conclusion about the amount of carbon the ocean was able to store.

    “We found that during the peak of the last ice age, the deep Atlantic Ocean was filled not just with southern-sourced waters as previously thought, but with northern-sourced waters as well,” said Howe.

    What was previously interpreted to be a layer of southern-sourced water in the deep Atlantic during the last ice age was in fact shown to be a mixture of slowly circulating northern- and southern-sourced waters with a large amount of carbon stored in it.

    “Our research looks at a time when the world was much colder than it is now, but it’s still important for understanding the effects of changing ocean circulation,” said Freeman. “We need to understand the dynamics of the ocean in order to know how it can be affected by a changing climate.”

    The research was funded in part by the Natural Environment Research Council (NERC), the Royal Society and the Isaac Newton Trust.

    Jacob Howe et al. North Atlantic Deep Water Production during the Last Glacial Maximum. Nature Communications (2016): DOI: 10.1038/ncomms11765

    Emma Freeman et al.Radiocarbon evidence for enhanced respired carbon storage in the Atlantic at the Last Glacial Maximum. Nature Communications (2016). DOI: 10.1038/ncomms11998

    See the full article here .

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    U Cambridge Campus

    The University of Cambridge (abbreviated as Cantab in post-nominal letters) is a collegiate public research university in Cambridge, England. Founded in 1209, Cambridge is the second-oldest university in the English-speaking world and the world’s fourth-oldest surviving university. It grew out of an association of scholars who left the University of Oxford after a dispute with townsfolk. The two ancient universities share many common features and are often jointly referred to as “Oxbridge”.

    Cambridge is formed from a variety of institutions which include 31 constituent colleges and over 100 academic departments organised into six schools. The university occupies buildings throughout the town, many of which are of historical importance. The colleges are self-governing institutions founded as integral parts of the university. In the year ended 31 July 2014, the university had a total income of £1.51 billion, of which £371 million was from research grants and contracts. The central university and colleges have a combined endowment of around £4.9 billion, the largest of any university outside the United States. Cambridge is a member of many associations and forms part of the “golden triangle” of leading English universities and Cambridge University Health Partners, an academic health science centre. The university is closely linked with the development of the high-tech business cluster known as “Silicon Fen”.

  • richardmitnick 4:28 pm on January 26, 2015 Permalink | Reply
    Tags: , Gaia Theory,   

    From New Scientist: “My verdict on Gaia hypothesis: beautiful but flawed” 


    New Scientist

    26 January 2015
    Toby Tyrrell

    We now have the evidence to pass judgement on James Lovelock’s wildly popular notion that life engineers hospitable worlds, says oceanographer Toby Tyrrell

    Climate cycles seem incompatible with the Gaia notion of a hospitable planet (Image: Michael Appelt/Anzenberger/eyevine)

    LIFE has steered Earth’s environment over billions of years, helping to keep it stable and comfortable for living things. That’s the crux of James Lovelock’s Gaia hypothesis, which addresses enduring questions such as “how does our planet work?” and “how is it that Earth has remained continuously habitable for more than 2 billion years?”

    Gaia is a fascinating hypothesis, but is it right? Working out the answer is particularly significant as we battle to be stewards of a planet with a human population of 7 billion and rising. If we don’t understand how our planet’s environment works, how can we know the best way to preserve it?

    I first became interested in Lovelock’s idea when I read his book Gaia: A new look at life on Earth and became intrigued by the idea that our planet could regulate itself. That interest influenced my career, eventually leading me to oceanography. But at the same time, I wasn’t sure that things could really be as simple as Lovelock had suggested.

    Lovelock made powerful arguments in favour of the Earth as a self-regulating system, but I could see no conclusive proof that the hypothesis was correct. So I began to investigate its feasibility in more detail, carrying out research into pertinent questions such as whether the ocean’s nitrate levels could be regulated by a “nitrostat” – a natural stabilising mechanism analogous to a thermostat.

    I was also fortunate to attend several conferences on Gaia, in Valencia, Spain, and in Oxford, along with luminaries such as the evolutionary biologists Bill Hamilton and John Maynard Smith; Lynn Margulis, who established endosymbiosis, the idea that one organism can live symbiotically within another; and Heinrich “Dick” Holland, an expert in the great oxygenation event, when oxygen first accumulated in the air. These meetings were a cross-disciplinary melting pot and led to an exciting exchange of ideas of a breadth we seldom find today.

    As I did more work, I realised that although there was a wealth of literature on Gaia, no one had made a thorough investigation of the whole hypothesis. I decided to attempt one. My approach was to dissect the Gaia hypothesis into component assertions, scrutinising each in turn.

    Lovelock’s books and articles propose three main arguments for Gaia: (1) that Earth is an extremely favourable habitat for life; (2) that life has greatly altered the planetary environment, including the chemical composition of the atmosphere and the sea; and (3) that Earth’s environment has remained fairly stable over geological time.

    Climate record

    I tested these assertions against the latest scientific evidence. In the decades since the Gaia hypothesis was proposed, our knowledge has grown enormously. We now have long climate records from ice cores; we have devised experiments to test the idea of kin selection – that it can make evolutionary sense for an organism to sacrifice its own reproductive success to boost that of a close relative; and we can reconstruct ice-age landscapes and vegetation. I tried to determine not only whether each assertion seemed correct in light of modern data but also whether, if correct, it constituted strong evidence in favour of the Gaia hypothesis over alternatives.

    Analysis of the first claim – that Earth’s environment is favourable for life – led me to look at ice ages. The environmental scientist Stephen Schneider considered these to be a strong argument against Gaia. I, too, found plenty of evidence that they are rather unfortunate times for life. During past ice ages the amount of terrestrial vegetation was reduced to about half that of warmer interglacial periods, and about three-quarters of the area now covered by shallow seas – the most productive parts of the ocean – became dry land when the sea level fell.

    The main driver of ice ages is not life but Milankovitch cycles, the periodic variations in the way the Earth orbits the sun, which are purely a matter of physics. However, life is implicated in the low temperatures which allow ice ages to occur because life is involved in the carbon cycle, which in turn controls atmospheric carbon dioxide and thus Earth’s greenhouse warming.

    Also unhelpful for life are the forms in which nitrogen is found on Earth. Vast quantities of it are present in the air and sea as inert molecules made of two nitrogen atoms, which only nitrogen-fixing microbes can make use of; much rarer are forms more easily used by life, such as nitrates. This leads to widespread nitrogen starvation despite the element’s superabundance. Earth’s nitrogen cycle is run almost entirely by microbes – but the outcome is the exact opposite of what ought to happen on a Gaian planet, on which life would be expected to engineer more favourable environmental conditions.

    When I looked into Lovelock’s second claim, I found it to be supported. There is plenty of evidence of biological alteration of the global environment. For instance, life affects the planetary albedo – the degree to which Earth reflects solar energy back out to space – through the generation by ocean microbes of dimethyl sulphide, a chemical that influences cloud formation.

    However, this effect, long held up as confirming Gaia, has turned out to be relatively weak (New Scientist, 29 June 2013, p 32). And there’s another catch. Although Lovelock’s second claim is clearly correct, it is not a clincher for Gaia because it could equally well support a competing idea. The “coevolution of life and planet” hypothesis posits that life and the environment influence each other but with no requirement that the outcome improve or maintain Earth’s habitability. There is no compelling reason to favour Gaia over this alternative.

    What about Lovelock’s third claim, that the Earth’s environment has remained fairly stable over geological time? This is contradicted by evidence for climate cycles punctuated by ice ages. We also have evidence of long-term variations in the concentrations of the major ions in seawater, and of snowball/slushball Earth events, when our planet may have completely frozen over. There is also the great oxygenation event itself, which caused a mass poisoning of anaerobic organisms.

    I also considered other topics, such as whether there is any obvious mechanism for Gaia. The hypothesis would be instantly more plausible if it could be seen to arise naturally out of evolution. Although I found no convincing reasons to believe this, I did come across some fascinating cases of “Gaias in miniature”. For instance, the interiors of termite mounds and wasps’ nests are strongly thermoregulated, experiencing much smaller day-night temperature fluctuations than the air outside. These stable internal temperatures come about partly because of how these social insects orientate their nests, but also through corrective group behaviours when brood temperatures drop too low or rise too high.

    These are great examples of Gaia in action, but they do not lead us to expect that something similar must happen at the global scale. It turns out that communal regulation of a shared environment has so far been observed only in closely related individuals, whereas the global biota is the opposite – genetically extremely diverse.

    My research led to a clear outcome: that the Gaia hypothesis is not an accurate picture of how our world works. Unfortunately, our planet is less robustly stabilised than Gaia implies, and therefore more fragile. In some ways it is a shame that this beautiful idea doesn’t hold true, but it is far better that we tackle environmental issues based on an accurate view of how our Earth system operates rather than a flawed one.

    See the full article here.

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