Gaia hypothesis 248189 225975085 2008-07-16T08:00:40Z Plumbago 125900 remove vandalism {{Otheruses|Gaia}} [[Image:The Earth seen from Apollo 17.jpg|200px|thumb|right|The study of planetary habitability is partly based upon extrapolation from knowledge of the [[Earth]]'s conditions, as the Earth is the only [[planet]] currently known to harbour [[life]]. The release of this image prompted the formulation of the proposition that the Earth was alive, and fostered acceptance of that proposition.]] The '''Gaia hypothesis''' is an [[ecology|ecological]] [[hypothesis]] that proposes that the [[biosphere]] and the physical components of the [[Earth]] ([[atmosphere]], [[cryosphere]], [[hydrosphere]] and [[lithosphere]]) are coupled together to form a [[complex system|complex interacting system]]. This system is proposed to act in a [[homeostasis|homeostatic]] fashion that preserves [[climate|climatic]] and [[biogeochemistry|biogeochemical]] conditions on Earth that are suitable for living [[organism]]s. Named after the [[Gaia (mythology)|Greek Titan of the earth]], the hypothesis is frequently described as viewing the Earth as a single organism. == History == The Gaia hypothesis was first scientifically formulated in the 1960s by the independent research scientist [[James Lovelock]], as a consequence of his work for [[NASA]] on methods of detecting life on Mars.<ref name="Lovelock1965">{{cite journal | author = Lovelock, J.E. | year = 1965 | title = A physical basis for life detection experiments | journal = [[Nature (journal)|Nature]] | volume = 207 | issue = 7 | pages = 568–570 | doi = 10.1038/207568a0}}</ref><ref>[http://www.jameslovelock.org/page4.html Geophysiology]</ref> He initially published the ''Gaia Hypothesis'' in journal articles in the early 1970s<ref>{{cite journal | author = J. E. Lovelock | title = Gaia as seen through the atmosphere | year = 1972 | journal = [[Atmospheric Environment]] | volume = 6 | issue = 8 | pages = 579–580 | doi = 10.1016/0004-6981(72)90076-5 }}</ref><ref name="lovelock1974">{{cite journal | author = Lovelock, J.E. | coauthors = Margulis, L. | year = 1974 | title = Atmospheric homeostasis by and for the biosphere- The Gaia hypothesis | journal = [[Tellus]] | volume = 26 | issue = 1 | pages = 2–10}}</ref> followed by a popularizing 1979 book ''Gaia: A new look at life on Earth''. The theory was initially, according to Lovelock, a way to explain the fact that combinations of chemicals including oxygen and methane persist in stable concentrations in the atmosphere of the Earth. Lovelock suggested using such combinations detected in other planets' atmospheres would be a relatively reliable and cheap way to detect life, which many biologists opposed at the time and since. Later other relationships such as the fact that sea creatures produce sulfur and iodine in approximately the quantities required by land creatures emerged and helped bolster the theory. Rather than invent many different theories to describe each such equilibrium, Lovelock dealt with them holistically, naming this self-regulating living system after the [[Greek mythology|Greek]] [[Greek primordial gods|goddess]] '''''[[Gaia (mythology)|Gaia]]''''', using a suggestion from the novelist [[William Golding]], who was living in the same village as Lovelock at the time ([[Bowerchalke]], [[Wiltshire]], UK). The Gaia Hypothesis has since been supported by a number of scientific experiments<ref>{{cite journal | author = J. E. Lovelock | title = Hands up for the Gaia hypothesis | year = 1990 | journal = [[Nature (journal)|Nature]] | volume = 344 | issue = 6262 | pages = 100–102 | doi = 10.1038/344100a0}}</ref> and provided a number of useful predictions,<ref>Volk, Tyler (2003), "Gaia's Body; Toward a Physiology of Earth" (MIT Press)</ref> and hence is properly referred to as the Gaia Theory. Since 1971, the noted [[microbiologist]] Dr. [[Lynn Margulis]] has been Lovelock's most important collaborator in developing Gaian concepts.<ref>Turney, Jon (2003), ''Lovelock and Gaia:Signs of Life'' Icon Books, UK [ISBN 1-84046-458-5]</ref> Until 1975 the hypothesis was almost totally ignored. An article in the [[New Scientist]] of February 15, 1975, and a popular book length version of the theory, published as ''The Quest for Gaia'', began to attract scientific and critical attention to the hypothesis. The theory was then attacked by many mainstream biologists. Championed by certain environmentalists and climate scientists, it was vociferously rejected by many others, both within scientific circles and outside them. == Lovelock's initial hypothesis == [[James Lovelock]] defined Gaia as: : ''a complex entity involving the Earth's [[biosphere]], [[Earth's atmosphere|atmosphere]], [[ocean]]s, and [[soil]]; the totality constituting a feedback or [[cybernetic]] system which seeks an optimal physical and chemical environment for life on this planet.'' His initial hypothesis was that the [[biomass (ecology)|biomass]] modifies the conditions on the planet to make conditions on the planet more hospitable – the Gaia Hypothesis properly defined this "hospitality" as a full [[homeostasis]]. Lovelock's initial hypothesis, accused of being [[Teleology|teleological]] by his critics, was that the [[atmosphere]] is kept in [[homeostasis]] by and for the [[biosphere]]. Lovelock suggested that life on Earth provides a cybernetic, [[homeostasis|homeostatic]] [[feedback]] system operated automatically and unconsciously by the [[biota (ecology)|biota]], leading to broad stabilization of global temperature and chemical composition. With his initial hypothesis, Lovelock claimed the existence of a global control system of [[surface temperature]], [[atmosphere composition]] and ocean [[salinity]]. His arguments were: * The global surface temperature of the Earth has remained constant, despite an increase in the energy provided by the [[Sun]]. * Atmospheric composition remains constant, even though it should be unstable. * Ocean salinity is constant. Since life started on Earth, the energy provided by the Sun has increased by 25% to 30%;<ref>{{cite journal | author = Owen, T. | coauthors = Cess, R.D.; Ramanathan, V. | year = 1979 | title = Earth: An enhanced carbon dioxide greenhouse to compensate for reduced solar luminosity | journal = [[Nature (journal)|Nature]] | volume = 277 | pages = 640–642 | doi = 10.1038/277640a0}}</ref> however the surface temperature of the planet has remained remarkably constant when measured on a global scale. Furthermore, he argued, the atmospheric composition of the Earth is constant.<ref>Lovelock, James (2000). Gaia: A New Look at Life on Earth ISBN 0-19-286218-9 </ref> The Earth's atmosphere currently consists of 79% nitrogen, 20.7% oxygen and 0.03% carbon dioxide. Oxygen is the second most reactive element after fluorine, and should combine with gases and minerals of the Earth's atmosphere and crust. Traces of methane (at an amount of 100,000 tonnes produced per annum)<ref name="Cicerone1988">{{cite journal | author = Cicerone, R.J. | coauthors = Oremland, R.S. | year = 1988 | title = Biogeochemical aspects of atmospheric methane | journal = [[Global Biogeochem. Cycles]] | volume = 2 | issue = 4 | pages = 299–327 | url = http://www.osti.gov/energycitations/product.biblio.jsp?osti_id=6704984 | doi = 10.1029/GB002i004p00299}}</ref> should not exist, as methane is combustible in an oxygen atmosphere. This composition should be unstable, and its stability can only have been maintained with removal or production by living organisms. Ocean [[salinity]] has been constant at about 3.4% for a very long time.<ref>{{cite journal | author = Volk, T. | year = 2002 | title = Toward a Future for Gaia Theory | journal = [[Climatic Change]] | volume = 52 | issue = 4 | pages = 423–430 | doi = 10.1023/A:1014218227825}}</ref> Salinity stability is important as most cells require a rather constant salinity and do not generally tolerate values above 5%. Ocean salinity constancy was a long-standing mystery, because river salts should have raised the ocean salinity much higher than observed. Recently it was suggested<ref>{{cite journal | author = Gorham, E. | year = 1991 | title = Biogeochemistry: its origins and development | journal = [[Biogeochemistry (journal)|Biogeochemistry]] | volume = 13 | issue = 3 | pages = 199–239 | doi = 10.1007/BF00002942}}</ref> that salinity may also be strongly influenced by seawater circulation through hot basaltic rocks, and emerging as hot water vents on ocean spreading ridges. However, the composition of sea water is far from equilibrium, and it is difficult to explain this fact without the influence of organic processes. The only significant natural source of atmospheric [[carbon dioxide]] (CO<sub>2</sub>) is [[volcanic activity]], while the only significant removal is through the precipitation of [[carbonate rocks]].<ref>{{cite journal | author = Karhu, J.A. | coauthors = Holland, H.D. | date = [[1996-10-01]] | title = Carbon isotopes and the rise of atmospheric oxygen | journal = [[Geology (journal)|Geology]] | volume = 24 | issue = 10 | pages = 867–870 | url = http://geology.geoscienceworld.org/cgi/content/abstract/24/10/867 | doi = 10.1130/0091-7613(1996)024<0867:CIATRO>2.3.CO;2}}</ref> In water, CO<sub>2</sub> is dissolved as a "[[carbonic acid]]," which may be combined with dissolved calcium to form solid calcium carbonate ([[limestone]]). Both precipitation and solution are influenced by the [[bacteria]] and plant roots in soils, where they improve gaseous circulation, or in coral reefs, where calcium carbonate is deposited as a solid on the sea floor. Calcium carbonate can also be washed from continents to the sea where it is used by living organisms to manufacture carbonaceous tests and shells. Once dead, the living organisms' shells fall to the bottom of the oceans where they generate deposits of chalk and limestone. Part of the organisms with carboneous shells are the [[coccolithophore]]s ([[algae]]), which also happen to participate in the formation of clouds. When they die, they release a sulfurous gas (DMS), (CH<sub>3</sub>)<sub>2</sub>S, which act as particles on which water vapor [[condensation|condenses]] to make clouds.<ref>Harding, Stephan (2006), "Animate Earth" (Green Books)</ref> Lovelock sees this as one of the complex processes that maintain conditions suitable for life. The volcanoes produce CO<sub>2</sub> in the atmosphere, CO<sub>2</sub> participates in rock weathering as carbonic acid, itself accelerated by temperature and soil life, the dissolved CO<sub>2</sub> is then used by the algae and released on the ocean floor. CO<sub>2</sub> excess can be compensated by an increase of [[coccolithophore|coccolithophoride]] life, increasing the amount of CO<sub>2</sub> locked in the ocean floor. Coccolithophorides increase the cloud cover, hence control the surface temperature, help cool the whole planet and favor precipitations which are necessary for terrestrial plants. For Lovelock and other Gaia scientists like Stephan Harding, coccolithophorides are one stage in a regulatory [[feedback loop]]. Lately the atmospheric CO<sub>2</sub> concentration has increased and there is some evidence that concentrations of ocean [[algal bloom]]s are also increasing.<ref>{{cite | date = [[2007-09-12]] | title = Interagency Report Says Harmful Algal Blooms Increasing | url = http://www.publicaffairs.noaa.gov/releases2007/sep07/noaa07-r435.html}}</ref> === Controversial concepts === Lovelock, especially in his older texts, indulged in language that has later caused fiery debates. For instance many of his biological critics such as [[Stephen J. Gould]] and [[Richard Dawkins]] attacked his statement in the first paragraph of his first Gaia book (1979), that "the quest for Gaia is an attempt to find the largest living creature on Earth." Lynn Margulis, the coauthor of Gaia hypotheses, is more careful to avoid controversial figures of speech than is Lovelock. In 1979 she wrote, in particular, that only [[homeorhetic]] and not [[homeostasis|homeostatic]] balances are involved: that is, the composition of Earth's atmosphere, hydrosphere, and lithosphere are regulated around "set points" as in [[homeostasis]], but those set points change with time. Also she wrote that there is no special tendency of biospheres to preserve their current inhabitants, and certainly not to make them comfortable. Accordingly, the [[Earth]] is a kind of community of trust which can exist at many discrete levels of integration. This is true for all [[multicellular organisms]] which do not live or die all at once: not all cells in the body die instantaneously, nor are homeostatic "set points" constant through the life of an organism. == Critical analysis == This theory is based on the idea that the [[biomass]] self-regulates the conditions on the planet to make its physical environment (in particular temperature and chemistry of the atmosphere) on the planet more hospitable to the species which constitute its "life". The Gaia Hypothesis properly defined this "hospitality" as a full [[homeostasis]]. A model that is often used to illustrate the original Gaia Hypothesis is the so-called [[Daisyworld]] simulation. Whether this sort of system is present on Earth is still open to debate. Some relatively simple [[homeostasis|homeostatic]] mechanisms are generally accepted. For example, when [[Earth's atmosphere|atmospheric]] [[carbon dioxide]] levels rise, the biomass of photosynthetic organisms increases and thus removes more carbon dioxide from the atmosphere, but the extent to which these mechanisms stabilize and modify the Earth's overall climate are not yet known. Less clear is the reason why such traits evolve in a system in order to produce such effects. Lovelock accepts a process of systemic Darwinian evolution for such mechanisms, creatures that evolve that improve their environment for their survival will do better than those which damage their environment. But many [[Darwinism|Darwinists]] have difficulty accepting such mechanisms can exist.<ref>Kirchner, James (2002), "The Gaia Hypothesis: Fact, Theory, and Wishful Thinking"52, Number 4 / March, 2002)</ref> === Criticism === After initially being largely ignored by most scientists, (from 1969 until 1977), thereafter for a period, the initial Gaia hypothesis was ridiculed by a number of scientists, like Ford Doolittle, Dawkins and Gould. On the basis of its name alone, the Gaia hypothesis was derided as some kind of [[neo-Pagan]] [[New Age]] [[religion]]. Many scientists in particular also criticised the approach taken in his popular book "Gaia, a New look at Life on Earth" for being [[teleology|teleological]]; a belief that all things have a predetermined purpose. Lovelock seems to have accepted this criticism of some of his statements, and has worked hard to remove the taint of teleological purpose from his theories, stating "Nowhere in our writings do we express the idea that planetary self-regulation is purposeful, or involves foresight or planning by the [[biota (ecology)|biota]]." – (Lovelock, J. E. 1990). In 1981, [[Ford Doolittle|W. Ford Doolittle]], in the ''[[CoEvolution Quarterly]]'' article "Is Nature Motherly" argued that there was nothing in the [[genome]] of individual organisms which could provide the feedback mechanisms Gaia theory proposed, and that therefore the Gaia hypothesis was an unscientific theory of a maternal type without any explanatory mechanism. In 1982 [[Richard Dawkins]] in his book ''[[The Extended Phenotype]]'' argued that organisms could not act in concert as this would require foresight and planning from them. Like Doolittle he rejected the possibility that feedback loops could stabilize the system. Dawkins claimed "there was no way for evolution by natural selection to lead to [[altruism]] on a Global scale".<!-- not sure about this last quote; can't find it in my copy of Extended Phenotype; looks more like paraphrasing to me --> [[Stephen Jay Gould]] criticised Gaia as merely a metaphorical description of Earth processes<ref>S.J.Gould: ''Kropotkin was no crackpot''. Natural History 106 (June 1997): 12-21 see [http://libcom.org/library/kropotkin-was-no-crackpot]</ref>. He wanted to know the actual mechanisms by which self-regulating homeostasis was regulated. Lovelock scoffs at this criticism and argues that no one mechanism is responsible, that the connections between the various known mechanisms may never be known, that this is accepted in other fields of biology and ecology as a matter of course, and that specific hostility is reserved for his own theory for political reasons. Aside from clarifying his language and understanding of what is meant by a life form, Lovelock himself ascribes most of the criticism to a lack of understanding of non-linear mathematics by his critics, and a linearizing form of [[greedy reductionism]] in which all events have to be immediately ascribed to specific causes before the fact. He notes also that his theory suggests experiments in many different fields, but few of them in biology which most of his critics are trained in. "I'm a general practitioner in a world where there's nothing but specialists... science in the last two centuries has tended to be ever-dividing" and often rivalrous, especially for funding which Lovelock describes as overly abundant and overly focused on institutions rather than original thought. He also flatly states that many of the critics above admitted not having actually read his work, but instead reacted to the name. {{Fact|date=January 2008}} He points out that [[Richard Feynman]] not only shared this opinion (coining the term [[cargo cult science]]) but also accepted a lack of general cause and effect theory as an inevitable phase as theories evolve, or indeed that some self-regulating phenomena may not be explainable at all mathematically. === Theory === {{unreferencedsection|date=July 2008}} One of the criteria of the empirical definition of life is its ability to replicate and pass on their genetic information to succeeding generations. Consequently, an argument against the idea that Gaia is a "living" organism is the fact that the planet is unable to reproduce. Lovelock, however, defines life as a self-preserving, self-similar system of feedback loops like [[Humberto Maturana]]'s [[autopoiesis]]; as a self-similar system, life could be a cell as well as an organ embedded into a larger organism as well as an individual in a larger inter-dependent social context. The biggest context of interacting inter-dependent living entities is the Earth. The problematic empirical definition is getting "fuzzy on the edges": Why are highly specialized bacteria like E. coli that are unable to thrive outside their habitat considered "life", while mitochondria, which have evolved independently from the rest of the cell, not? Maturana and Lovelock changed this with the [[autopoiesis]] deductive definition which to them explains the phenomenon of life better; some aspects of the empirical definition, however, no longer apply. Reproduction becomes optional: bee swarms reproduce, while the biosphere has no need to. Lovelock himself states in the original Gaia book that even that is not true; given the possibilities, the biosphere may multiply in the future by colonizing other planets, as humankind may be the primer by which Gaia will reproduce. Humanity's exploration of space, its interest in colonizing and even terraforming other planets, lends some plausibility to the idea that Gaia might in effect be able to reproduce. The astronomer [[Carl Sagan]] also remarked that from a cosmic viewpoint, the space probes since 1959 have the character of a planet preparing to go to seed. This might warrant interpretation as a rhetorical point, however, as it [[Equivocation| equivocates]] two differing meanings of "reproduction" otherwise. == Daisyworld simulations == Lovelock responded to criticisms by developing the mathematical model [[Daisyworld]] with Andrew Watson to demonstrate that feedback mechanisms could evolve from the actions or activities of self-interested organisms, rather than through classic [[group selection]] mechanisms.<ref>Watson, A.J., and Lovelock, J.E. (1983). Biological homeostasis of the global environment: the parable of Daisyworld. ''Tellus '35B''', 286-289.</ref> Daisyworld examines the [[Earth's energy budget|energy budget]] of a planet populated by two different types of plants, black daisies and white daisies. The colour of the daisies influences the [[albedo]] of the planet such that black daisies absorb light and warm the planet, while white daisies reflect light and cool the planet. Competition between the daisies (based on temperature-effects on growth rates) leads to a balance of populations that tends to favour a planetary temperature close to that which is optimum for the daisy growth. Lovelock and Watson demonstrated the stability of Daisyworld by forcing the [[star|sun]] that it [[Orbit#Planetary orbits|orbits]] to evolve along the [[main sequence]], taking it from low to high [[Solar radiation#Solar constant|solar constant]]. This perturbation of Daisyworld's receipt of [[solar radiation]] caused the balance of daisies to gradually shift from black to white but the planetary temperature was always regulated back to this optimum (except at the extreme ends of solar evolution). This situation is very different from the corresponding [[abiotic]] world, where temperature is unregulated and rises linearly with solar output. Later versions of Daisyworld introduced a range of grey daisies and populations of [[grazing|grazers]] and [[predation|predators]], and found that these further increased the stability of the [[homeostasis]]. More recently other research, modelling the real biochemical cycles of Earth, and using various "guilds" of life (eg. [[photosynthesis]]ers, [[decomposition|decomposers]], [[herbivores]] and primary and secondary [[carnivores]]) has also been shown to produce Daisyworld-like regulation and stability, which helps to explain planetary [[biodiversity|biological diversity]]{{Fact|date=October 2007}}. This enables nutrient [[recycling]] within a regulatory framework derived by [[natural selection]] amongst [[species]], where one being's harmful waste becomes low energy food for members of another guild. This research on the [[Redfield ratio]] of Nitrogen to Phosphorus shows that local biotic processes can regulate global systems (See Keith [http://scholar.google.com/scholar?hl=en&lr=&q=cache:5cOZ-ijfXIoJ:www.ifi.ntnu.no/grupper/ai/eval/guild/guild.ps.gz+Gaia+theory| Downing] & Peter Zvirinsky, ''The Stimulated Evolution of Biochemical Guilds: Reconciling Gaia Theory with Natural Selection''). == First Gaia conference == In 1988, to draw attention to the Gaia hypothesis, the [[climatology|climatologist]] [[Stephen Schneider]] organised a conference of the [[American Geophysical Union]]'s first Chapman Conference on Gaia, held at San Diego in 1989, solely to discuss Gaia. At the conference [[James Kirchner]] criticised the Gaia hypothesis for its imprecision. He claimed that Lovelock and Margulis had not presented one Gaia hypothesis, but four - * [[Coevolution|CoEvolutionary]] Gaia - that life and the environment had evolved in a coupled way. Kirchner claimed that this was already accepted scientifically and was not new. * [[Homeostatic]] Gaia - that life maintained the stability of the natural environment, and that this stability enabled life to continue to exist. * [[Geophysics|Geophysical]] Gaia - that the Gaia theory generated interest in geophysical cycles and therefore led to interesting new research in terrestrial geophysical dynamics. * Optimising Gaia - that Gaia shaped the planet in a way that made it an optimal environment for life as a whole. Kirchner claimed that this was not testable and therefore was not scientific. Of Homeostatic Gaia, Kirchner recognised two alternatives. "Weak Gaia" asserted that life tends to make the environment stable for the flourishing of all life. "Strong Gaia" according to Kirchner, asserted that life tends to make the environment stable, ''in order to enable'' the flourishing of all life. Strong Gaia, Kirchner claimed, was untestable and therefore not scientific. Referring to the Daisyworld Simulations, Kirchner responded that these results were predictable because of the intention of the programmers - Lovelock and Watson, who selected examples which would produce the responses they desired. Lawrence Joseph in his book "Gaia: the birth of an idea" argued that Kirchner's attack was principally against Lovelock's integrity as a scientist. As Jon Tuney demonstrates, it is not Lovelock's style to respond to such personal attacks and Lovelock did not attack Kirchner's views for ten years, until his autobiography "Homage to Gaia", where he spoke of Kirchner's ''[[sophistry]]''. Lovelock and other Gaia-supporting scientists, however, did attempt to disprove the claim that the theory is not scientific because it is impossible to test it by controlled experiment. For example, against the charge that Gaia was teleological Lovelock and Andrew Watson offered the [[Daisyworld]] model (and its modifications, above) as evidence against most of these criticisms. Lovelock was careful to present a version of the Gaia Hypothesis which had no claim that Gaia intentionally or consciously maintained the complex balance in her environment that life needed to survive. It would appear that the claim that Gaia acts "intentionally" was a metaphoric statement in his popular initial book and was not meant to be taken literally. This new statement of the Gaia hypothesis was more acceptable to the scientific community. The accusations of [[teleology|teleologism]] were largely dropped after this conference. == Range of views == Some have found [[James Kirchner]]'s suggested spectrum, proposed at the First Gaia Chapman Conference, useful in suggesting that the original Gaia hypothesis could be split into a spectrum of hypotheses, ranging from the undeniable (Weak Gaia) to the radical (Strong Gaia). === Weak Gaia === At one end of this spectrum is the undeniable statement that the organisms on the Earth have altered its composition. A stronger position is that the Earth's biosphere effectively acts as if it is a [[self-organizing system]], which works in such a way as to keep its systems in some kind of "[[meta-]]equilibrium" that is broadly conducive to life. The history of evolution, ecology and climate show that the exact characteristics of this equilibrium intermittently have undergone rapid changes, which are believed to have caused [[extinction]]s and felled [[civilization]]s (see [[climate change]]). Weak Gaian hypotheses suggest that Gaia is co-evolutive. [[Co-evolution]] in this context has been thus defined: "[[biota (ecology)|Biota]] influence their abiotic environment, and that environment in turn influences the [[biota (ecology)|biota]] by [[Darwinism|Darwinian process]]." Lovelock (1995) gave evidence of this in his second book, showing the evolution from the world of the early [[bacteria|thermo-acido-phyllic]] and [[methanogenic bacteria]] towards the oxygen enriched atmosphere today that supports more [[Phanerozoic|complex life]]. The weakest form of the theory has been called "influential Gaia". It states that [[biota (ecology)|biota]] barely influence certain aspects of the [[abiotic]] world, e.g. temperature and atmosphere. The weak versions are more acceptable from an orthodox science perspective, as they assume non-[[homeostasis]]. They state the evolution of life and its environment may affect each other. An example is how the activity of [[photosynthesis|photosynthetic]] bacteria during Precambrian times have completely modified the [[Earth's atmosphere|Earth atmosphere]] to turn it aerobic, and as such supporting evolution of life (in particular [[eukaryotic]] life). However, these theories do not claim the atmosphere modification has been done in coordination and through homeostasis. Also such critical theories have yet to explain how conditions on Earth have not been changed by the kinds of run-away positive feedbacks that have affected [[Mars]] and [[Venus]]. Biologists and earth scientists usually view the factors that stabilize the characteristics of a period as an undirected [[emergent property]] or [[entelechy]] of the system; as each individual species pursues its own self-interest, for example, their combined actions tend to have counterbalancing effects on environmental change. Opponents of this view sometimes reference examples of life's actions that have resulted in dramatic change rather than stable equilibrium, such as the conversion of the Earth's atmosphere from a [[reducing environment]] to an [[oxygen]]-rich one. However, proponents sometimes say that those [[earth atmosphere|atmospheric]] composition changes created an environment even more suitable to life. Some go a step further and hypothesize that all lifeforms are part of one single living planetary being called ''Gaia''. In this view, the atmosphere, the seas and the terrestrial crust would be results of interventions carried out by Gaia through the [[coevolution|coevolving]] diversity of living organisms. While it is arguable that the Earth as a unit does not match the generally accepted [[biology|biological]] criteria for [[life]] itself (''Gaia'' has not yet reproduced, for instance; it still might ''spread'' to other planets through human [[space colonization]] and [[terraforming]]), many scientists would be comfortable characterising the earth as a single "[[system]]". === Strong Gaia === A version called "Optimizing Gaia" asserts that biota manipulate their physical environment for the purpose of creating biologically favorable, or even optimal, conditions for themselves. "The Earth's atmosphere is more than merely anomalous; it appears to be a contrivance specifically constituted for a set of purposes"<ref name="lovelock1974" />. Further, "... it is unlikely that chance alone accounts for the fact that temperature, pH and the presence of compounds of nutrient elements have been, for immense periods, just those optimal for surface life. Rather, ... energy is expended by the biota to actively maintain these optima"<ref name="lovelock1974" />. Another strong hypothesis is the one called "Omega Gaia"<ref>[http://www.kheper.net/gaia/Gaia-table.htm Stages in the Evolution of Gaia], [http://www.kheper.net/ Kheper website]. Retrieved [[14 May]] [[2008]].</ref>. [[Teilhard de Chardin]] claimed that the Earth is evolving through stages of [[cosmogenesis]], affecting the [[geosphere]], [[biogenesis]] of the [[biosphere]], and [[noogenesis]] of the [[noosphere]], culminating in the ''[[Omega Point]]''. Another form of the strong Gaia hypothesis is proposed by [[Guy Murchie]] who extends the quality of a holistic lifeform to [[galaxies]]. "After all, we are made of star dust. Life is inherent in nature." Murchie describes geologic phenomena such as sand dunes, glaciers, fires, etc. as living organisms, as well as the life of metals and crystals. "The question is not whether there is life outside our planet, but whether it is possible to have "nonlife". There are speculative versions of the Gaia hypothesis, including versions in which it is held that the Earth is conscious or part of some universe-wide evolution such as expressed in the [[Biocosm|Selfish Biocosm hypothesis]] strain of a larger speculative [[Gaia philosophy]]. These extreme forms of the Gaia hypothesis, that the entire Earth is a single unified organism that is ''consciously'' manipulating the climate in order to make conditions more conducive to life, are [[Metaphysics|metaphysical]] or [[Mysticism|mystical]] views for which no evidence exists, and which cannot be tested scientifically. Another strain which also goes further than science presently justifies, is the [[Gaia Movement]], a collection of different organisations operating in different countries, but all sharing a concern for how humans might live more sustainably within the "living system". == Recent developments == Gaia Theory has developed considerably.<ref>Turney, Jon (2003), ''Lovelock and Gaia:Signs of Life'' Icon Books, UK [ISBN 1-84046-458-5]</ref> Margulis dedicated the last eight chapters of her book, ''The Symbiotic Planet'', to Gaia. She resented the widespread personification of Gaia and stressed that Gaia is "not an organism", but "an emergent property of interaction among organisms". She defined Gaia "the series of interacting ecosystems that compose a single huge ecosystem at the Earth's surface. Period." Yet still she argues, "the surface of the planet behaves as a physiological system in certain limited ways". Margulis seems to agree with Lovelock in that, in what comes to these physiological processes, the earth's surface is "best regarded as alive". The book's most memorable "slogan" was actually quipped by a student of Margulis': "Gaia is just symbiosis as seen from space". This neatly connects Gaia theory to Margulis' own theory of [[endosymbiosis]]. In recent years both Lovelock's and Margulis's understanding of Gaia have gained some increased support as a potentially viable, testable scientific hypothesis or theory.<ref>Schwartzman, David (2002) "Life, Temperature, and the Earth: The Self-Organizing Biosphere" (Columbia University Press, ISBN 0231102135)</ref>.<ref>Turney, Jim (2003). "Lovelock & Gaia. Signs of Life". (Icon Books UK, Cambridge. ISBN 1-84046-458-5.)</ref> ==== Second Gaia conference ==== By the time of the 2nd Chapman Conference on the Gaia Hypothesis, held at Valencia, Spain, on 23 June 2000, the situation had developed significantly in accordance with the developing science of Bio-[[geophysiology]]. Rather than a discussion of the Gaian teleological views, or "types" of Gaia Theory, the focus was upon the specific mechanisms by which basic short term homeostasis was maintained within a framework of significant evolutionary long term structural change. The major questions were: # "How has the global biogeochemical/climate system called Gaia changed in time? What is its history? Can Gaia maintain stability of the system at one time scale but still undergo vectorial change at longer time scales? How can the geologic record be used to examine these questions?" # "What is the structure of Gaia? Are the feedbacks sufficiently strong to influence the evolution of climate? Are there parts of the system determined pragmatically by whatever disciplinary study is being undertaken at any given time or are there a set of parts that should be taken as most true for understanding Gaia as containing evolving organisms over time? What are the feedbacks among these different parts of the Gaian system, and what does the near closure of matter mean for the structure of Gaia as a global ecosystem and for the productivity of life?" # "How do models of Gaian processes and phenomena relate to reality and how do they help address and understand Gaia? How do results from Daisyworld transfer to the real world? What are the main candidates for "daisies"? Does it matter for Gaia theory whether we find daisies or not? How should we be searching for daisies, and should we intensify the search? How can Gaian mechanisms be investigated using process models or global models of the climate system which include the biota and allow for chemical cycling?" Tyler Volk (1997) has suggested that once life evolves, a Gaian system is almost inevitably produced as a result of an evolution towards far-from-equilibrium homeostatic states that maximise [[entropy]] production (MEP). Kleidon (2004) agrees with Volk's hypothesis, stating: "...homeostatic behavior can emerge from a state of MEP associated with the planetary albedo"; "...the resulting behavior of a biotic Earth at a state of MEP may well lead to near-homeostatic behavior of the Earth system on long time scales, as stated by the Gaia hypothesis." Staley (2002) has similarly proposed "...an alternative form of Gaia theory based on more traditional Darwinian principles... In [this] new approach, environmental regulation is a consequence of population dynamics, not Darwinian selection. The role of selection is to favor organisms that are best adapted to prevailing environmental conditions. However, the environment is not a static backdrop for evolution, but is heavily influenced by the presence of living organisms. The resulting co-evolving dynamical process eventually leads to the convergence of equilibrium and optimal conditions." ==== Third Gaia conference ==== A third international conference on the Gaia Theory, sponsored by the Northern Virginia Regional Park Authority and others, was held in October 2006 at the Arlington, VA campus of George Mason University. Lynn Margulis, Distinguished University Professor in the Department of Geosciences, University of Massachusetts-Amherst, and long-time advocate of the Gaia Theory, was a keynote speaker. Among many other speakers: Tyler Volk, Co-director of the Program in Earth and Environmental Science at New York University; Dr. Donald Aitken, Principal of Donald Aitken Associates; Dr. Thomas Lovejoy, President of the Heinz Center for Science, Economics and the Environment; Robert Correll, Senior Fellow, Atmospheric Policy Program, American Meteorological Society and noted environmental ethicist, J. Baird Callicott. James Lovelock, the theory’s progenitor, prepared a video specifically for the event. This conference approached Gaia Theory as both science and metaphor as a means of understanding how we might begin addressing 21st century issues such as climate change and ongoing environmental destruction. == Gaia hypothesis in ecology == After much criticism, a modified Gaia hypothesis is now considered within [[Ecology|ecological science]] basically consistent with the planet Earth being the ultimate object of ecological study. Ecologists generally consider the biosphere as an [[ecosystem]] and the Gaia hypothesis, though a simplification of that original proposed, to be consistent with a modern vision of global ecology, relaying the concepts of [[biosphere]] and [[biodiversity]]. The Gaia hypothesis has been called [[geophysiology]] or [[Earth System Science]], which takes into account the interactions between [[biota (ecology)|biota]], the [[ocean]]s, the [[geosphere]], and the [[Earth's atmosphere|atmosphere]]. To promote research and discussion in these fields an organisation, "Gaia Society for Research and Education in Earth System Science" was started. An example of the change in acceptability of Gaia theories is the Amsterdam declaration of the scientific communities of four international global change research programmes - the International Geosphere-Biosphere Programme (IGBP), the International Human Dimensions Programme on Global Environmental Change (IHDP), the World Climate Research Programme (WCRP) and the international biodiversity programme DIVERSITAS - recognise that, in addition to the threat of significant climate change, there is growing concern over the ever-increasing human modification of other aspects of the global environment and the consequent implications for human well-being. They state "Research carried out over the past decade under the auspices of the four programmes to address these concerns has shown that: # The Earth System behaves as a single, self-regulating system comprised of physical, chemical, biological and human components. The interactions and feedbacks between the component parts are complex and exhibit multi-scale temporal and spatial variability. The understanding of the natural dynamics of the Earth System has advanced greatly in recent years and provides a sound basis for evaluating the effects and consequences of human-driven change. # Human activities are significantly influencing Earth's environment in many ways in addition to greenhouse gas emissions and climate change. Anthropogenic changes to Earth's land surface, oceans, coasts and atmosphere and to biological diversity, the water cycle and biogeochemical cycles are clearly identifiable beyond natural variability. They are equal to some of the great forces of nature in their extent and impact. Many are accelerating. Global change is real and is happening now. # Global change cannot be understood in terms of a simple cause-effect paradigm. Human-driven changes cause multiple effects that cascade through the Earth System in complex ways. These effects interact with each other and with local- and regional-scale changes in multidimensional patterns that are difficult to understand and even more difficult to predict. # Earth System dynamics are characterised by critical thresholds and abrupt changes. Human activities could inadvertently trigger such changes with severe consequences for Earth's environment and inhabitants. The Earth System has operated in different states over the last half million years, with abrupt transitions (a decade or less) sometimes occurring between them. Human activities have the potential to switch the Earth System to alternative modes of operation that may prove irreversible and less hospitable to humans and other life. The probability of a human-driven abrupt change in Earth's environment has yet to be quantified but is not negligible. # In terms of some key environmental parameters, the Earth System has moved well outside the range of the natural variability exhibited over the last half million years at least. The nature of changes now occurring simultaneously in the Earth System, their magnitudes and rates of change are unprecedented. The Earth is currently operating in a no-analogue state." Sir Crispin Tickell in the 46th Annual Bennett Lecture for the 50th Anniversary of Geology at the University of Leicester in his recent talk "Earth Systems Science: Are We Pushing Gaia Too Hard?" stated "as a theory, Gaia is now winning." [http://www2.le.ac.uk/ebulletin/features/2000-2009/2006/11/nparticle.2006-11-20.9623961254] He continued "The same goes for the earth systems science which is now the concern of the Geological Society of London (with which the Gaia Society recently merged). Whatever the label, earth systems science, or Gaia, has now become a major subject of inquiry and research, and no longer has to justify itself." These findings would seem to be fully in accord with the Gaia theory. Despite this endorsement, the late [[Bill Hamilton]], one of the founders of modern [[Darwinism]], whilst conceding the empirical basis of the planetary homeostatic processes on which Gaia is based, states that it is a theory still awaiting its [[Copernicus]]. == Gaia hypothesis in Media Studies == The notion of Gaia has been applied to the networked society and the globalized Internet by cultural theorist Dr. [[Michael Strangelove]], "Confronted with the inaccessibility of our physical frontiers, my generation has turned inward and discovered two new immanent and infinite frontiers. These new frontiers of the next millennium are the uncensored, distributed self, and cyberspace--the location of the virtual self/community--Electric Gaia." <ref>Michael Strangelove '[http://www.ibiblio.org/cmc/mag/1994/sep/self.html The Internet, Electric Gaia and the Rise of the Uncensored Self],' ''Computer-Mediated Communication Magazine'', Vol. 1, No. 5, 1 September 1994, 11. In a posting to the [http://www.iath.virginia.edu/lists_archive/Humanist/v06/0577.html Humanist listserv] in 1993 Strangelove described the concept of 'electric Gaia in the following terms: 'I am trying to develop an idea that occurred to me over a year ago while in some god-forsaken hotel in Kansas City, and thought HUMANIST to be a good place to start. I want to write about the implications of the gradual convergence of two separate systems and conceptual worlds. These "systems" are Gaia, as understood in popular terms as a self-regulating biosphere (and, by extension, universe); and the Net (or Matrix), the emerging global "virtual community" of computer networks, from BBSs to Free-Nets, to the Internet itself. As these conceptual worlds gain ground and combine in the popular imagination, will we witness the emergence of what I have named "Electric Gaia" - the technologically-facilitated growth of a new form of global consciousness or self/group identity that could be said, in a metaphorical sense, to give consciousness to Gaia itself? Given this "research question" I will probably explore the implications of an emergent Electric Gaia on issues surrounding self and group identity, the impact of "virtual community" upon one's relationship with the physical self and other bodies. Further threads of inquiry would look at the possibility of an existential schizophrenia, unique to the individual who participates in Electric Gaia, that might arise in light of two radically different experiences of time/space and the "other".'</ref> == ''The Revenge of Gaia'' == In James Lovelock's latest book, ''[[The Revenge of Gaia]]'', he argues that the lack of respect humans have had for Gaia, through the damage done to [[rainforests]] and the reduction in planetary [[biodiversity]], is testing Gaia's capacity to minimize the effects of the addition of [[greenhouse gases]] in the [[atmosphere]]. This eliminates the planet's [[homeostasis|homeostatic]] [[negative feedback]] potential and increases the likelihood of [[positive feedback]]s associated with runaway [[global warming]]. Similarly the warming of the oceans is extending the oceanic [[thermocline]] layer of tropical oceans into the [[Arctic]] and [[Antarctic]] waters, preventing the rise of oceanic nutrients into the surface waters and eliminating the [[algal bloom]]s of [[phytoplankton]] on which oceanic [[foodchain]]s depend. As phytoplankton and forests are the main ways in which Gaia draws down greenhouse gases, particularly [[carbon dioxide]], taking it out of the [[atmosphere]], the elimination of this environmental [[buffer]]ing will see, according to Lovelock, most of the earth becoming uninhabitable for humans and other life-forms by the middle of next century, with a massive extension of tropical [[desert]]s. Given these conditions, Lovelock expects human [[civilization]] will be hard pressed to [[end of civilization|survive]]. He expects the change to be similar to the [[Paleocene-Eocene Thermal Maximum]] when atmospheric concentration of CO2 was 450 ppm. At that point the [[Arctic Ocean]] was 23 degrees Celsius and had [[crocodile]]s in it, with the rest of the world mostly scrub and desert. He says of [[sustainable development]] and [[renewable energy]] that it came "200 years too late" and that more effort should go into [[adaptation]], including more use of [[fission]]. He likens the [[Kyoto Protocol]] to the Munich conferences that failed to prevent [[World War II]], including the likelihood that the disaster will cause people to come together in common cause. "We have been through no less than seven of these events as humans...comparable in extent to the change" likely to be wrought by global warming. He claims that Gaia's self-regulation will likely prevent any extraordinary runaway effects that wipe out life itself, but that humans will survive and be "culled and, I hope, refined." According to James Lovelock, by 2040, the world population of more than six billion will have been culled by floods, drought and famine. The people of Southern Europe, as well as South-East Asia, will be fighting their way into countries such as Canada, Australia and Britain. He says that ''"By 2040, parts of the Sahara desert will have moved into middle Europe. We are talking about [[Paris]] - as far north as [[Berlin]]. In Britain we will escape because of our oceanic position."'' Lovelock believes it is too late to repair the damage. ''"If you take the [[Intergovernmental Panel on Climate Change]] predictions, then by 2040 every summer in Europe will be as hot as it was in 2003 - between 110F and 120F. It is not the death of people that is the main problem, it is the fact that the plants can't grow - there will be almost no food grown in Europe. We are about to take an evolutionary step and my hope is that the species will emerge stronger. It would be hubris to think humans as they now are God's chosen race."''<ref>[http://www.dailymail.co.uk/pages/live/articles/news/news.html?in_article_id=541748&in_page_id=1770 Daily Mail - 22 March 2008 - We're all doomed ! 40 years from global catastrophe - says climate change expert]</ref> == Influences of the Gaia hypothesis == === Scientific literature === [[Fritjof Capra]], in his fourth book, ''The Web of Life,'' used Gaia theory to explain the complications and interconnections in the web of life. [http://www.chelseagreen.com/authors/stephan_harding/ Stephan Harding], a student of [[Lovelock]], has written a book, [http://www.chelseagreen.com/2006/items/animateearth ''Animate Earth: Science, Intuition, and Gaia'']. === Music === An oratorio by American composer [[Nathan Currier]] called ''Gaian Variations'' was premiered on [[Earth Day]] 2004 at [[Lincoln Center]] by the Brooklyn Philharmonic, using texts of [[James Lovelock]], [[Loren Eiseley]] and [[Lewis Thomas]]. === Fiction === At least four works of fiction use the Gaia hypothesis as a central part of the plot. In two of his [[science fiction]] novels, ''[[Foundation's Edge]]'' ([[1982]]) and ''[[Foundation and Earth]]'' ([[1984]]), [[Isaac Asimov]] describes the planet [[Gaia (Foundation universe)|Gaia]] as one on which all things, living and inanimate, are taking part in a planetary consciousness to an appropriate measure. In Asimov's story Gaia strives for an even greater [[superorganism]] that it calls [[Galaxia]], and that comprises the whole [[galaxy]]. In ''[[Lovelock]]'' ([[1994]]), a novel by [[Orson Scott Card]] & [[Kathryn H. Kidd]], Gaiaology is a fully fledged interdisciplinary science which will soon be put to use by the Earth's first interstellar colony ship. Assuming the target planet will need [[terraforming]], the job of the ship's Gaiaologist will be to integrate the terrestrial species needed for the colonists' survival with the planet's existing ecology. The Gaiaologist's "Witness," a form of assistance animal whose job it is to record every waking moment in the life of such a prominent member of society, is the central character of the book, an enhanced [[Capuchin monkey]] named after [[James Lovelock|Sir James Lovelock]]. The Gaia hypothesis is used extensively by Brian Aldiss in his [[Helliconia]] Trilogy, where the planets of Helliconia and, to a lesser extent, Earth, are presented as the main characters in a story spanning the rise and fall of civilizations as influenced by Helliconia's 2,500-year-long cycle of seasons. The Gaia hypothesis was also used as a central theme in the novel ''Portent'', by James Herbert, in which Lovelock is mentioned by name. The South Park episode [[Lice Capades]] addresses the Gaia hypothesis from an ironic standpoint- when one louse suggests that the planet (a child's head) is alive, another louse responds with "If the planet was alive, would it feel this?" and shoots the boy's head-- the impact being so minute the boy barely notices. The dialog refers to a scene from Final Fantasy: The Spirits Within, in which the same dialog is used. [[Edge of Darkness]] a British television drama serial, produced by BBC Television in association with Lionheart Television International and originally broadcast in six fifty-five minute episodes in late 1985. American poet, writer and Deep Ecology activist Gary Snyder has a chapter of poems called "Little Songs for Gaia" in his collection of poetry "Axe Handles" (1983). In [[Final Fantasy: The Spirits Within]], a sci-fi movie, Dr. Sid and his assistant Aki are fierce promoters of the Gaia Theory. Though, in the film, "Gaia" is in reference to the underlying life force within the planet, very similar to the [[lifestream]] found in [[Final Fantasy VII]]. === Games === [[Maxis]] has specifically named the Gaia hypothesis and Lovelock as inspirations for their 1990 game, [[SimEarth]]. The 1999 [[turn-based strategy]] [[Personal computer game|PC game]], ''[[Sid Meier's Alpha Centauri]]'', features a living (and eventually sentient) planet in the [[Alpha Centauri]] star system. One of the games factions is named "Gaia's Stepdaughters", a group of environmentalists who believe in living with the planet rather than trying to tame or destroy it. == See also == * [[Autopoiesis]] * [[Blue marble]] * [[CLAW hypothesis]] * [[Earth Science]] * [[Environmentalism]] * [[Gaia spore]] * [[Geophysiology]] * [[James Kirchner]] * [[Noosphere]] * [[Permaculture]] * [[SimEarth]] * [[Technogaianism]] == References == ===Inline=== <references /> ===General=== * Lovelock, James. ''The Independent''. [http://comment.independent.co.uk/commentators/article338830.ece The Earth is about to catch a morbid fever], 16 January 2006. * Kleidon, Axel (2004). Beyond Gaia: Thermodynamics of Life and Earth system functioning. ''Climate Change'', 66(3): 271-319. * Lovelock, James (1995). ''The Ages of Gaia: A Biography of Our Living Earth'' ISBN 0-393-31239-9 * Lovelock, James (2000). ''Gaia: A New Look at Life on Earth'' ISBN 0-19-286218-9 * Lovelock, James (2001). ''Homage to Gaia: The Life of an Independent Scientist'' ISBN 0-19-860429-7 * Lovelock, James (2006), interviewed in ''How to think about science'', [[CBC Ideas]] (radio program), broadcast January 3, 2008 * {{cite book | author=Lovelock, James | title=The Revenge of Gaia: Why the Earth Is Fighting Back - and How We Can Still Save Humanity | publisher=Allen Lane, Santa Barbara (California) | year=2006 | id=ISBN 0-7139-9914-4}}. [[The Revenge of Gaia]] * {{cite book | author=Margulis, Lynn | title=Symbiotic Planet: A New Look at Evolution | publisher=Weidenfeld & Nicolson, London | year=1998 | id=ISBN 0-297-81740-X}} * Staley, M. (2004). Darwinian selection leads to Gaia. ''J. Theoretical Biol.'', 218(1): [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12297068&dopt=Citation|M. Staley abstract] * Stephen H. Schneider, et al., (Eds) (2004), ''Scientists Debate Gaia: The Next Century'' ISBN 0-262-19498-8 * Thomas, Lewis (1974) ''Lives of a Cell'' == External links == * [http://www.jameslovelock.org/page4.html Bibliography] * [http://www.mountainman.com.au/gaia.html The Gaia Hypothesis] proposed by Dr James Lovelock & Dr Lynn Margulis * [http://www.gaianvariations.com/ GaianVariations] * [http://jebin08.blogspot.com/2006/01/gaia-revenge-and-trust.html Gaia, revenge and trust] Lovelock's pessimism on anthropogenic climate change. * [http://www.gaiatheory.org Gaia Theory: Model and Metaphor for the 21st Century] Conference information and upcoming Gaia-related programs and events. 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