Tonight on RDF should have been the deadline of Mazille's second Science Writing Award, a great idea for which he was thanked by the RDF management in a very strange way, since all of his posts have been deleted :pissed: ...including the contest's rules.
I am starting that thread so that I can post the article I was about to submit when the lights went out. It would probably be a nice idea if the others would also post their already submitted articles here, whether or not the vote is carried on.
Earth - Our Home was the theme of that contest. Following soon is my try at a subject that took me quite some research to write about, since it lies very far from my comfort zone. Comparing to the version I was about to post on RDF, I just removed a reference to Richard Dawkins, I hope that was not too vengeful a thing to do.
The Second RDF Science Writing Award - Post-Apo Submissions
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palindnilap
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palindnilap
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Re: The Second RDF Science Writing Award - Post-Apo Submissions
Earth, Life and Thermodynamics
What makes Earth different?
The answer to that question may seem obvious, but try to imagine how you would characterize Earth in the most general possible way if you were living some light years away from it, having only its radiation spectrum to work with. That is the type of question that the inventor James Lovelock was confronted to when he was a part of the NASA search project for extra-terrestrial life, and he came up with the following great idea. [1]
Fill a black bottle with a sample of the atmosphere of a "dead" planet, like Mars or Venus, and keep it in isolation. What happens to the content of the bottle? The short answer is, nothing happens. Now fill a second bottle with Earth's atmosphere. There is something different. The free oxygen starts to react with the other gases in the sample. When the gas in the bottle finally settles to an equilibrium state, that state is quite different from what we started with. In fact, the composition of the gas is now not very far from the content of the first bottle. [2]
What it means is that the composition of Earth's atmosphere is not at equilibrium ; but another observation we can make is that it is still remarkably constant. That fact is not as easy to explain as it sounds, and let us first review why the most traditional approaches don’t tell much on that matter.
A system at equilibrium is a dead system [3]
The idea of equilibrium might have been the most successful idea in the study of dynamical systems (systems that evolve with time) and has yielded spectacular results in domains as diverse as economy, population genetics and chemistry. It consists of focusing on the conditions in which the system can be in a constant state. And the good news is that it is generally possible to find those conditions, thanks to the simple mathematical trick of solving the equations that set all the derivatives of the system's functions to zero.
But are there such solutions? Actually, it is known that given enough time, any closed physical system - that does not interact with its surroundings - will evolve to an equilibrium state. So the principle of looking for equilibrium points is an extremely powerful tool for predicting the behavior of a closed system.
In contrast, the common knowledge about open systems, the ones that exchange energy (or matter) with their surroundings, is that, put in the extremely rigorous words of mathematicians, weird things can happen. The view of equilibrium theories over an open system is that of as a succession of exogeneous shocks (coming from outside the system), each one followed with a return to a different equilibrium. That works well is some cases. For instance, if in a chemical reaction one adds an extra amount of one of the reactives, the result will be a rapid equilibrium shift according to Le Chatelier's principle [4].
But the sad news for the equilibrium theories is that many systems are widely open systems that are not satisfactorily modeled by a succession of exogeneous shocks, since the external influences are so frequent that the system never comes close to attaining any of its successive computed equilibrium points. For instance, that is one of the reasons why the equilibrium-based theories that form the core of the mainstream study of economy have fared so badly at predicting real-life events [5]. According to nobelized economist Paul Samuelson, "Wall Street indexes predicted nine out of the last five recessions."[6]
In that regard, the attraction of the scientists for equilibrium theories is not without resemblance with the story of the proverbial drunkard looking for his lost keys under a street lamp, although he knows very well that he dropped them a little further, in the dark. Since the keys of understanding Earth as a whole are not under the street lamps of the equilibrium theories, we will soon have to enter the darker areas with a modest pocket lamp.
Earth as a thermodynamical system
We now know that Earth, being out of equilibrium, must be an open system. That begs the question of what enters and exits the system; or in other words, what is the fuel of life? The commonplace answer is in schoolbooks: it is the energy of the sunlight. That energy is absorbed by the plants through photosynthesis, stored as potential energy in the organic molecules thus built, and can in turn fuel the herbivores, who fuel their predators, and so on.
While that standard answer is partly correct, it lacks a lot in precision. Life is more than an energy cycle. Life is also about the building of structures, the creation of information. The Second Law of Thermodynamics tells that the entropy of a closed system – in our case, the universe as a whole - can never decrease. Since structure and information are antonyms for entropy, what must pay for the building of those is a negative entropy balance in the Earth system, for which Schrödinger coined the term negentropy. [7]
That negentropy is explained by classical thermodynamics. All the energy that Earth (or any other planet) receives from the Sun has to be radiated back into space, if the planet's temperature is to remain constant. But although both radiations carry the same amount of energy, they carry a different kind of energy! The Sun being much hotter than the Earth, its radiation consists of photons of a much higher frequency. The entropy carried by radiation is known to be inversely proportional to the temperature of its emitter, hence Earth is radiating much more entropy into space that it is gaining from the sunlight. That is the secret of Earth's entropy balance. We are currently pondering about sending our nuclear waste into space; but by its cold radiation, Earth already sends its "waste" into space: a lot more entropy than it is getting from the sunlight.
For those of you interested in wildly approximated figures, the available negentropy has been computed to be about 1038 bits per second in terms of information [8], which can be thought of as the Earth's computing power. The part of that negentropy that is "consumed" by the human civilization is about 0.08% [9].
The above are today's figures. But it has not always been like today. An interesting estimation of stellar theory is that the intensity of the Sun's radiation has increased by about 30% since the time when life started on Earth. Another calculation translates that into a difference of about 20-30 K in Earth's mean temperature, enough to cause the whole surface of Earth to be covered with ice. That contradiction with geological observations has been well explained by an enhanced greenhouse effect [10], but it is still a strange coincidence. So to our short-term surprise of the atmosphere being of stable composition, we can add the long-term surprise of Earth's mean temperature being more stable across times than we should expect.
Feedback loops, where are you?
A straightforward yet powerful observation over open dynamical systems is that the wildest behaviours are observed in the presence of positive feedback loops, better known as vicious circles (although they aren’t necessarily deleterious). On the other hand, the self-regulating behaviours indicate the presence of at least one negative feedback loop. An example of a negative feedback loop is the law of supply and demand in economy. If the demand for a good increases, its price increases as well, which makes customers less interested in it. If the supply increases, the price decreases, which lowers the incentive to produce. That negative feedback has a stabilizing effect on prices, ensuring that the bread you pay $2 today won't cost $20 tomorrow - unless you are unlucky enough to live in an economy that hosts vicious circles.
So Earth’s stable condition can be explained only by the discovery of a negative feedback loop. And a simple statistical intuition suggests that if a system as complex as Earth must host a negative feedback loop, then it probably hosts many such loops. Since those feedback loops exist only on planet Earth, they certainly involve the biosphere. Since they make life sustainable, a tempting conjecture would be that they have been the logical issue of an evolutionary process (indeed, the original Gaia Hypothesis by James Lovelock and Lynn Margulis took the conjecture even one step further by considering Earth as a living organism, that the elements of the biosphere were actively striving to regulate [11]).
But there is a big problem here : the regulator organisms would be vulnerable to an invasion by defectors, which would take profit of the atmospheric regulation without contributing to it. As soon as some organisms would mutate to a non-regulating form, they would be favoured by natural selection, since they would reap the benefits of atmospheric regulation at no cost. In other words, the envisioned mechanism for atmospheric regulation by altruistic living organisms is a naive kind of group selection - just the kind that doesn't work.
On the other hand, Stuart Kauffmann's taught us in his book "The Origins of Order" that although evolution by natural selection is a huge contributor to the self-organization we observe around us, it is not the only one. A visual example of a structure that self-organizes without selection is a snow flake. And it is indeed possible to exhibit self-organizing behaviours in systems that obey simple rules and that don't rely on natural selection [12]. In other words, the processes by which an organism takes part in the atmospheric regulation can emerge from self-organization and don’t need to entail a cost in fitness - they can also be neutral or beneficial. The regulation can then be a byproduct of those processes instead of being the result of an evolutionary dynamic. In fact, that might be an understatement. It looks like it must be such a byproduct.
There are not many known examples that illustrate the presence of those necessary negative feedback mechanisms. One that seems to be understood is the production and emission of dimethyl sulfide by the phytoplankton. That production is thought to sustain important physiological functions, and increases with the amount of sunlight received. The emitted dimethyl sulfide has a positive effect on cloud formation, which in turn decreases the amount of sunlight received by the phytoplankton [13]. But although all the steps of the chain seem to hold, in a system as complex as Earth's biosphere and meteorology there could easily exist overlooked factors which could unbuckle the loop.
A toy model
I would like to conclude that article by describing a nice toy model, again by James Lovelock, in which all the computations can be carried on. Daisyworld is a planet that gets light from a nearby star and that hosts only two forms of life, competing for covering its limited gray surface : white daisies and black daisies. Both varieties of daisies share the same window of viable temperatures, and have a reproduction rate that depends on their local temperatures according to some sort of symmetrical bell curve - with the optimal reproduction rate occurring at the middle of the viability window. The diffusion of temperature isn’t immediate, so that local temperatures can differ. That’s all there is, translated into some simple equations. The question is, what happens to the planet's mean temperature when the star's radiation varies? [14]
The idea is that low temperatures favour the black daisies, which by absorbing the most possible light can warm their surroundings, and thus contribute to increase Daisyworld's mean temperature. Conversely, high temperatures favour the white daisies, which reflect all of the light and cool their surroundings. That sounds like a perfect negative feedback loop. Let us see how it worked in the original simulation.
The simulation started with a low radiation value, which was gradually increased. Daisies started to appear as soon as the planet's temperature entered the viability window, but black daisies proliferated while white daisies couldn't sustain themselves since they were cooling their surroundings, throwing themselves out of the viability window. The black daisies made Daisyworld darker and warmer, with Daisyworld's temperature rising much faster than the increase in radiation. Then the white daisies appeared, making the rise in mean temperature a little slower. The temperature then rose to a maximum slightly over the ideal temperature. That made the white daisies the favoured species, which had the surprising effect that the further increases in radiation resulted in a slight decrease in temperature. The radiation was then increased to extreme values, which would have pushed the temperatures well beyond the viability window were Daisyworld a bare ground. But even then, the favoured white daisies managed to cool the planet enough to survive. Of course, all good things come to an end and at the point where the radiation made even an all-white planet too hot, Daisyworld's ecosystem collapsed. Of course, a similar sequence of events happened when the radiation was decreased again, since the model is symmetrical with regard to temperature.
The Daisyworld model has spawned a lot of recent research, with people testing the addition of various degrees of realism. It must be said that not all of those enriched models showed the same nice regulating properties as the original Daisyworld. [15]
When making Daisyworld's temperature diffusion rely on a more realistic geometry, some studies found out that although there still was regulation, the apparition of deserts made it less efficient and more vulnerable to ecological catastrophes. Another observation was that the temperature diffusion must not be too fast, as it could occur on a too small planet.
Evolutive models - with the daisies allowed to mutate in colour and/or in preferred temperature - yielded contrasted results, with some cases where the regulation disappeared. A key condition for regulation seemed to be the existence of a high enough cost entailed for a big shift in preferred temperature.
Small increases in ecological complexity can be harmful, but bigger increases seem to have a positive effect. That is a very interesting finding because it contrasts with the behaviour of ecosystems that have been modeled without interaction with their environment [16]. For instance, the introduction of a species of unselective herbivore can destroy the regulation. But if one allows for three species of selective herbivores that have different degrees of preferences, the regulation is restored. And the introduction of an extra unselective carnivore makes the regulation work even better. [17]
That last result inspired me an optimistic though more than speculative conclusion. In contrast to what the Daisyworld model seemed to tell us at first glance, one of the reasons why the self-regulating magic of the Earth system is so elusive might be that it resides in the very complexity of the system. In some sense, that would be rather bad news for research. But seen from a more down-to-earth perspective, wouldn’t that also be good news for the sustainability of our beloved planet?
References
[1] Lovelock, J.E., "A physical basis for life detection experiments", Nature, 1965.
[2] Smolin, L., "The Life of the Cosmos", Oxford University Press, 1997.
[3] Waldrop, M.M., "Complexity : the Emerging Science at the Edge of Order and Chaos", Touchstone, 1992. The title of the section is in fact a variant of the John Holland quote that appears in that book, which was "If the system ever reaches equilibrium, it isn't just stable. It is dead."
[4] Wikipedia article about Le Chatelier's principle : http://en.wikipedia.org/wiki/Le_Chatelier's_principle
[5] Beinhocker, E., "The Origin of Wealth", Harvard Business School, 2006.
[6] Samuelson, P., "Science and Stocks", Newsweek, September 1966.
[7] Schrödinger, "What is life ?", McMillan, 1946. Although the observations of the whole paragraph are now more than commonplace, they seem to stem from that Schrödinger book.
[8] Roland-Mieszkowski, M., "Life on Earth - Flow of Energy and Entropy", Digital Recordings, 1994, http://www.digital-recordings.com/publ/publife.html .
[9] Weiss, W., "The Balance of Entropy on Earth", in "Continuum Mechanics and Thermodynamics", Springer, 1994.
[10] Owen, T., Cess, R.D., Ramanathan, V., "Earth: An enhanced carbon dioxide greenhouse to compensate for reduced solar luminosity", Nature, 1979.
[11] Lovelock, J.E., "The Ages of Gaia - A Biography of Our living Earth", Oxford University Press, 1983.
[12] Kauffmann, S., "The Origins of Order", Oxford University Press, 1993.
[13] Norris, K.B., "Dimethylsulfide Emission: Climate Control by Marine Algae?", http://www.csa.com, 2003, http://www.csa.com/discoveryguides/dime ... erview.php .
[14] Lovelock, J.E., "Daisy world - A cybernetic proof of the Gaia Hypothesis", The Co-evolution Quarterly Summer, 1983. Yes, the title is a little over the top.
[15] Wood, A.J., Ackland, G.J., Dyke, J.G., Williams, H.T.P., Lenton, T.M., "Daisyworld: a review", Review of Geophysics 46, 2008.
[16] Pimm, S.L., “The complexity and stability of ecosystems”, Nature, 1984.
[17] Harding, S.P., “Food web complexity enhances community stability and climate regulation in a geophysiological model”, Tellus, Series B, 1999
What makes Earth different?
The answer to that question may seem obvious, but try to imagine how you would characterize Earth in the most general possible way if you were living some light years away from it, having only its radiation spectrum to work with. That is the type of question that the inventor James Lovelock was confronted to when he was a part of the NASA search project for extra-terrestrial life, and he came up with the following great idea. [1]
Fill a black bottle with a sample of the atmosphere of a "dead" planet, like Mars or Venus, and keep it in isolation. What happens to the content of the bottle? The short answer is, nothing happens. Now fill a second bottle with Earth's atmosphere. There is something different. The free oxygen starts to react with the other gases in the sample. When the gas in the bottle finally settles to an equilibrium state, that state is quite different from what we started with. In fact, the composition of the gas is now not very far from the content of the first bottle. [2]
What it means is that the composition of Earth's atmosphere is not at equilibrium ; but another observation we can make is that it is still remarkably constant. That fact is not as easy to explain as it sounds, and let us first review why the most traditional approaches don’t tell much on that matter.
A system at equilibrium is a dead system [3]
The idea of equilibrium might have been the most successful idea in the study of dynamical systems (systems that evolve with time) and has yielded spectacular results in domains as diverse as economy, population genetics and chemistry. It consists of focusing on the conditions in which the system can be in a constant state. And the good news is that it is generally possible to find those conditions, thanks to the simple mathematical trick of solving the equations that set all the derivatives of the system's functions to zero.
But are there such solutions? Actually, it is known that given enough time, any closed physical system - that does not interact with its surroundings - will evolve to an equilibrium state. So the principle of looking for equilibrium points is an extremely powerful tool for predicting the behavior of a closed system.
In contrast, the common knowledge about open systems, the ones that exchange energy (or matter) with their surroundings, is that, put in the extremely rigorous words of mathematicians, weird things can happen. The view of equilibrium theories over an open system is that of as a succession of exogeneous shocks (coming from outside the system), each one followed with a return to a different equilibrium. That works well is some cases. For instance, if in a chemical reaction one adds an extra amount of one of the reactives, the result will be a rapid equilibrium shift according to Le Chatelier's principle [4].
But the sad news for the equilibrium theories is that many systems are widely open systems that are not satisfactorily modeled by a succession of exogeneous shocks, since the external influences are so frequent that the system never comes close to attaining any of its successive computed equilibrium points. For instance, that is one of the reasons why the equilibrium-based theories that form the core of the mainstream study of economy have fared so badly at predicting real-life events [5]. According to nobelized economist Paul Samuelson, "Wall Street indexes predicted nine out of the last five recessions."[6]
In that regard, the attraction of the scientists for equilibrium theories is not without resemblance with the story of the proverbial drunkard looking for his lost keys under a street lamp, although he knows very well that he dropped them a little further, in the dark. Since the keys of understanding Earth as a whole are not under the street lamps of the equilibrium theories, we will soon have to enter the darker areas with a modest pocket lamp.
Earth as a thermodynamical system
We now know that Earth, being out of equilibrium, must be an open system. That begs the question of what enters and exits the system; or in other words, what is the fuel of life? The commonplace answer is in schoolbooks: it is the energy of the sunlight. That energy is absorbed by the plants through photosynthesis, stored as potential energy in the organic molecules thus built, and can in turn fuel the herbivores, who fuel their predators, and so on.
While that standard answer is partly correct, it lacks a lot in precision. Life is more than an energy cycle. Life is also about the building of structures, the creation of information. The Second Law of Thermodynamics tells that the entropy of a closed system – in our case, the universe as a whole - can never decrease. Since structure and information are antonyms for entropy, what must pay for the building of those is a negative entropy balance in the Earth system, for which Schrödinger coined the term negentropy. [7]
That negentropy is explained by classical thermodynamics. All the energy that Earth (or any other planet) receives from the Sun has to be radiated back into space, if the planet's temperature is to remain constant. But although both radiations carry the same amount of energy, they carry a different kind of energy! The Sun being much hotter than the Earth, its radiation consists of photons of a much higher frequency. The entropy carried by radiation is known to be inversely proportional to the temperature of its emitter, hence Earth is radiating much more entropy into space that it is gaining from the sunlight. That is the secret of Earth's entropy balance. We are currently pondering about sending our nuclear waste into space; but by its cold radiation, Earth already sends its "waste" into space: a lot more entropy than it is getting from the sunlight.
For those of you interested in wildly approximated figures, the available negentropy has been computed to be about 1038 bits per second in terms of information [8], which can be thought of as the Earth's computing power. The part of that negentropy that is "consumed" by the human civilization is about 0.08% [9].
The above are today's figures. But it has not always been like today. An interesting estimation of stellar theory is that the intensity of the Sun's radiation has increased by about 30% since the time when life started on Earth. Another calculation translates that into a difference of about 20-30 K in Earth's mean temperature, enough to cause the whole surface of Earth to be covered with ice. That contradiction with geological observations has been well explained by an enhanced greenhouse effect [10], but it is still a strange coincidence. So to our short-term surprise of the atmosphere being of stable composition, we can add the long-term surprise of Earth's mean temperature being more stable across times than we should expect.
Feedback loops, where are you?
A straightforward yet powerful observation over open dynamical systems is that the wildest behaviours are observed in the presence of positive feedback loops, better known as vicious circles (although they aren’t necessarily deleterious). On the other hand, the self-regulating behaviours indicate the presence of at least one negative feedback loop. An example of a negative feedback loop is the law of supply and demand in economy. If the demand for a good increases, its price increases as well, which makes customers less interested in it. If the supply increases, the price decreases, which lowers the incentive to produce. That negative feedback has a stabilizing effect on prices, ensuring that the bread you pay $2 today won't cost $20 tomorrow - unless you are unlucky enough to live in an economy that hosts vicious circles.
So Earth’s stable condition can be explained only by the discovery of a negative feedback loop. And a simple statistical intuition suggests that if a system as complex as Earth must host a negative feedback loop, then it probably hosts many such loops. Since those feedback loops exist only on planet Earth, they certainly involve the biosphere. Since they make life sustainable, a tempting conjecture would be that they have been the logical issue of an evolutionary process (indeed, the original Gaia Hypothesis by James Lovelock and Lynn Margulis took the conjecture even one step further by considering Earth as a living organism, that the elements of the biosphere were actively striving to regulate [11]).
But there is a big problem here : the regulator organisms would be vulnerable to an invasion by defectors, which would take profit of the atmospheric regulation without contributing to it. As soon as some organisms would mutate to a non-regulating form, they would be favoured by natural selection, since they would reap the benefits of atmospheric regulation at no cost. In other words, the envisioned mechanism for atmospheric regulation by altruistic living organisms is a naive kind of group selection - just the kind that doesn't work.
On the other hand, Stuart Kauffmann's taught us in his book "The Origins of Order" that although evolution by natural selection is a huge contributor to the self-organization we observe around us, it is not the only one. A visual example of a structure that self-organizes without selection is a snow flake. And it is indeed possible to exhibit self-organizing behaviours in systems that obey simple rules and that don't rely on natural selection [12]. In other words, the processes by which an organism takes part in the atmospheric regulation can emerge from self-organization and don’t need to entail a cost in fitness - they can also be neutral or beneficial. The regulation can then be a byproduct of those processes instead of being the result of an evolutionary dynamic. In fact, that might be an understatement. It looks like it must be such a byproduct.
There are not many known examples that illustrate the presence of those necessary negative feedback mechanisms. One that seems to be understood is the production and emission of dimethyl sulfide by the phytoplankton. That production is thought to sustain important physiological functions, and increases with the amount of sunlight received. The emitted dimethyl sulfide has a positive effect on cloud formation, which in turn decreases the amount of sunlight received by the phytoplankton [13]. But although all the steps of the chain seem to hold, in a system as complex as Earth's biosphere and meteorology there could easily exist overlooked factors which could unbuckle the loop.
A toy model
I would like to conclude that article by describing a nice toy model, again by James Lovelock, in which all the computations can be carried on. Daisyworld is a planet that gets light from a nearby star and that hosts only two forms of life, competing for covering its limited gray surface : white daisies and black daisies. Both varieties of daisies share the same window of viable temperatures, and have a reproduction rate that depends on their local temperatures according to some sort of symmetrical bell curve - with the optimal reproduction rate occurring at the middle of the viability window. The diffusion of temperature isn’t immediate, so that local temperatures can differ. That’s all there is, translated into some simple equations. The question is, what happens to the planet's mean temperature when the star's radiation varies? [14]
The idea is that low temperatures favour the black daisies, which by absorbing the most possible light can warm their surroundings, and thus contribute to increase Daisyworld's mean temperature. Conversely, high temperatures favour the white daisies, which reflect all of the light and cool their surroundings. That sounds like a perfect negative feedback loop. Let us see how it worked in the original simulation.
The simulation started with a low radiation value, which was gradually increased. Daisies started to appear as soon as the planet's temperature entered the viability window, but black daisies proliferated while white daisies couldn't sustain themselves since they were cooling their surroundings, throwing themselves out of the viability window. The black daisies made Daisyworld darker and warmer, with Daisyworld's temperature rising much faster than the increase in radiation. Then the white daisies appeared, making the rise in mean temperature a little slower. The temperature then rose to a maximum slightly over the ideal temperature. That made the white daisies the favoured species, which had the surprising effect that the further increases in radiation resulted in a slight decrease in temperature. The radiation was then increased to extreme values, which would have pushed the temperatures well beyond the viability window were Daisyworld a bare ground. But even then, the favoured white daisies managed to cool the planet enough to survive. Of course, all good things come to an end and at the point where the radiation made even an all-white planet too hot, Daisyworld's ecosystem collapsed. Of course, a similar sequence of events happened when the radiation was decreased again, since the model is symmetrical with regard to temperature.
The Daisyworld model has spawned a lot of recent research, with people testing the addition of various degrees of realism. It must be said that not all of those enriched models showed the same nice regulating properties as the original Daisyworld. [15]
When making Daisyworld's temperature diffusion rely on a more realistic geometry, some studies found out that although there still was regulation, the apparition of deserts made it less efficient and more vulnerable to ecological catastrophes. Another observation was that the temperature diffusion must not be too fast, as it could occur on a too small planet.
Evolutive models - with the daisies allowed to mutate in colour and/or in preferred temperature - yielded contrasted results, with some cases where the regulation disappeared. A key condition for regulation seemed to be the existence of a high enough cost entailed for a big shift in preferred temperature.
Small increases in ecological complexity can be harmful, but bigger increases seem to have a positive effect. That is a very interesting finding because it contrasts with the behaviour of ecosystems that have been modeled without interaction with their environment [16]. For instance, the introduction of a species of unselective herbivore can destroy the regulation. But if one allows for three species of selective herbivores that have different degrees of preferences, the regulation is restored. And the introduction of an extra unselective carnivore makes the regulation work even better. [17]
That last result inspired me an optimistic though more than speculative conclusion. In contrast to what the Daisyworld model seemed to tell us at first glance, one of the reasons why the self-regulating magic of the Earth system is so elusive might be that it resides in the very complexity of the system. In some sense, that would be rather bad news for research. But seen from a more down-to-earth perspective, wouldn’t that also be good news for the sustainability of our beloved planet?
References
[1] Lovelock, J.E., "A physical basis for life detection experiments", Nature, 1965.
[2] Smolin, L., "The Life of the Cosmos", Oxford University Press, 1997.
[3] Waldrop, M.M., "Complexity : the Emerging Science at the Edge of Order and Chaos", Touchstone, 1992. The title of the section is in fact a variant of the John Holland quote that appears in that book, which was "If the system ever reaches equilibrium, it isn't just stable. It is dead."
[4] Wikipedia article about Le Chatelier's principle : http://en.wikipedia.org/wiki/Le_Chatelier's_principle
[5] Beinhocker, E., "The Origin of Wealth", Harvard Business School, 2006.
[6] Samuelson, P., "Science and Stocks", Newsweek, September 1966.
[7] Schrödinger, "What is life ?", McMillan, 1946. Although the observations of the whole paragraph are now more than commonplace, they seem to stem from that Schrödinger book.
[8] Roland-Mieszkowski, M., "Life on Earth - Flow of Energy and Entropy", Digital Recordings, 1994, http://www.digital-recordings.com/publ/publife.html .
[9] Weiss, W., "The Balance of Entropy on Earth", in "Continuum Mechanics and Thermodynamics", Springer, 1994.
[10] Owen, T., Cess, R.D., Ramanathan, V., "Earth: An enhanced carbon dioxide greenhouse to compensate for reduced solar luminosity", Nature, 1979.
[11] Lovelock, J.E., "The Ages of Gaia - A Biography of Our living Earth", Oxford University Press, 1983.
[12] Kauffmann, S., "The Origins of Order", Oxford University Press, 1993.
[13] Norris, K.B., "Dimethylsulfide Emission: Climate Control by Marine Algae?", http://www.csa.com, 2003, http://www.csa.com/discoveryguides/dime ... erview.php .
[14] Lovelock, J.E., "Daisy world - A cybernetic proof of the Gaia Hypothesis", The Co-evolution Quarterly Summer, 1983. Yes, the title is a little over the top.
[15] Wood, A.J., Ackland, G.J., Dyke, J.G., Williams, H.T.P., Lenton, T.M., "Daisyworld: a review", Review of Geophysics 46, 2008.
[16] Pimm, S.L., “The complexity and stability of ecosystems”, Nature, 1984.
[17] Harding, S.P., “Food web complexity enhances community stability and climate regulation in a geophysiological model”, Tellus, Series B, 1999
Re: The Second RDF Science Writing Award - Post-Apo Submissions
Just so you know: We'll get the contest up and running again after the dust has settled a bit. life is currently trying to get the deleted posts by us few unlucky ones back, which means that the rules will be available again soon. THWOTH and hack have backed up all the submissions so far, as well as all the discussions around the writing competition, so not much is lost in that regard, although it will take some time.
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palindnilap
- Posts: 13
- Joined: Tue Feb 23, 2010 9:38 am
- Contact:
Re: The Second RDF Science Writing Award - Post-Apo Submissions
Hey Mazille, good to see you back and kicking ! I guessed that the contest would be resurrected after all this month's great submissions. I thought it would help getting all articles together in a thread here, but it sounds like it won't be necessary. Great !Mazille wrote:Just so you know: We'll get the contest up and running again after the dust has settled a bit. life is currently trying to get the deleted posts by us few unlucky ones back, which means that the rules will be available again soon. THWOTH and hack have backed up all the submissions so far, as well as all the discussions around the writing competition, so not much is lost in that regard, although it will take some time.
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