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THE FEASIBILITY OF A TESTABLE GAIA HYPOTHESIS
A Project Presented to The Faculty of the Undergraduate College of Mathematics and Sciences James Madison University
In Partial Fulfillment of the Requirements for the Degree Bachelor of Sciences by Brent Franklin Bauman 1998
Introduction
In contrast to Darwinian theories of natural selection which hold that life evolves and adapts to existing geologic conditions, the Gaia hypothesis, first proposed by James Lovelock in 1969, states that Earth and the life inhabiting it coevolve as one globally integrated system. This system, Gaia, is homeostatically regulated through biological negative feedback reactions and creates conditions that are self-sustaining and comfortable for life itself. Lovelock compares the Earth's self-regulating abilities to those of a hypothetical planetary organism that is capable of maintaining the Earth's surface biogeochemistry as an organism maintains its own life-sustaining internal conditions. Views regarding the relationships between life and the Earth have historically resulted in polar opposite positions of scientific thought. Within the natural sciences, two such positions currently prevail: reductionism and holism. Reductionism is the notion that systems can be understood by analysis of their component parts. It proposes, for example, that all biological phenomena can be understood and described by the laws of physics. Holism is the notion that the component parts of a system can only be understood in context of the whole system. For example, biological phenomena exhibit emergent properties that can be ultimately reduced to or explained by the laws of physics. Although numerous holistic theories have recently emerged, reductionism has remained the dominant paradigm in the sciences since the 1950's (Goldsmith 65). In view of the reductionist paradigm, it is unsurprising that Gaia, a holistic approach to science, has procured much division within the scientific community and has obtained many critics. James W. Kirchner, a professor at the University of California, Berkeley, has become one of Gaia's staunchest critics in recent years. His criticisms focus on the testability of the Gaia hypothesis. Kirchner claims that the Gaia hypothesis has merits because of the interdisciplinary scientific research it has stimulated in fields that have historically remained isolated. He acknowledges also that it has reiterated the well-established fact that the Earth's biology influences the environment. As a scientific hypothesis, however, Kirchner finds Gaia untestable, ambiguous, and misleading. Kirchner's criticisms of Gaia stem from the early works of Karl Popper, a notable philosopher of science who viewed theories as testable as long as remained open to falsification. Surficially, Kirchner provides convincing arguments illustrating the untestable nature of Gaia. It is naïve, however, to brand Gaia as "untestable" without thoroughly exploring the philosophical foundations of scientific testability. A complex system like Gaia cannot simply be accepted or rejected based upon simple verification or falsification tests. The testability of Gaia can only be determined by careful examination of the philosophical foundations governing its testability.
This paper explores the feasibility of a testable Gaia hypothesis in a twofold endeavor. First, it is imperative to delineate the scientific foundations that govern scientific testability. Under the umbrella of this definition for testability, it then becomes possible to use mechanisms such as ecological modeling to prove the viability of inherently chaotic and complex systems such as Gaia.
James Lovelock and the Formulation of the Gaia Hypothesis
The Gaia hypothesis was first proposed by James Lovelock in 1969. Lovelock is a British scientist and inventor with a Ph.D. in Medicine from the London School of Hygiene and Tropical Medicine. Although Lovelock has been a visiting scientist at many institutions including Harvard, Yale, the Jet Propulsion Laboratories in Pasadena, California, and NASA, Lovelock is not formally associated with any major university or research facility. Lovelock, instead, practices science independently, using revenue earned from his inventions to fund his research. As an inventor, Lovelock is most well known for the development of the Electron Capture Detector (ECD), a device designed to detect trace amounts of chemical compounds in the atmosphere. Using this device, Lovelock was the first to confirm the accumulation of chlorofluorocarbons (CFCs) in the atmosphere. This research provided the first hard data leading to the ban of CFCs in order to protect the Earth's stratospheric ozone layer. In spring of 1961, the National Aeronautics and Space Administration (NASA) invited Lovelock to work as a member of a team developing lunar soil analysis methods. Soon after he began with NASA, Lovelock was transferred to work with the Voyager mission, designing life detection instrumentation for other planets, namely Mars. When faced with the task of detecting life on Mars, Lovelock was dissatisfied with the efforts of his fellow scientists who envisioned Martian life detection techniques which emulated those effective on Earth. Their ideas included automated microbiological laboratories to sample the Martian soil for its suitability to support fungi, bacteria, and other microorganisms, and devices to detect life's byproducts such as proteins and amino acids (Lovelock, A New Look 2). Lovelock questioned these methods, wondering "How can we be sure the Martian way of life, if any, will reveal itself to tests based on Earth's lifestyle…to say nothing of more difficult questions such as ‘What is life, and how should it be recognized'" (A New Look 2). When asked how he would detect life on Mars, Lovelock first considered the ideas that eventually led to his formulation of the Gaia hypothesis. He proposed to search for a decrease in entropy on Mars, since entropy reduction is a seemingly universal characteristic of life. Realizing the inherent difficulties in testing the properties of entropy reduction of possible life on distant planets, Lovelock reconsidered the problem. After considering the notion of life and entropy reduction for some time, Lovelock envisioned a new method of life detection. Assuming that life requires the use of fluid media (the oceans and or the atmosphere) as ‘conveyor belts' for raw materials and waste products, Lovelock deduced that some activities associated with the entropy reduction of living systems would affect and alter the composition of the ‘conveyor-belt regions'. Thus, the atmosphere of a life-bearing planet would noticeably differ from the atmosphere of a dead planet. Since Mars currently has no oceans, the presence of life would require the utilization of the atmosphere to convey raw materials. Thus, Mars would be the ideal planet for life detection experiments based on its atmospheric composition (Lovelock, A New Look 6).
carbon dioxide, containing trace amounts of hydrogen and hydrogen sulfide, unknown quantities of nitrogen, and presumably no methane or oxygen. This early atmosphere maintained a state of thermodynamic equilibrium and was controlled by abiological chemical reactions. The Earth's surface presumably contained organic chemical components such as amino acids, the subunits of proteins, the subunits of polysaccharides, nucleosides, and other building blocks for life. The Earth contained liquid water and therefore ranged in temperature from 0 and 50 degrees Celsius. In addition, the Archean solar luminosity, or output of the sun, was 25% less than that of today (Lovelock Ages of Gaia 65-69). Around 3.6 billion years ago, the first life on Earth evolved. This first Archean life consisted of two major types of bacterium: photosynthesizers and consumers. The photosynthesizers converted carbon dioxide into organic matter and oxygen. Small amounts of oxygen produced by these photosynthesizers quickly reduced by oxidizing chemicals such as iron and sulfur. The consumers, or decomposers, converted organic matter back into carbon dioxide and methane. As these simple bacteria colonized the Archean Earth and acquired the capacity to control their environment, Gaia first emerged. According to Lovelock, in the anoxic Archean Earth, the simple balance between the photosynthesizers and consumers stabilized the planetary ecosystem. The growth of photosynthesizers cooled the Earth by consuming the ‘greenhouse gas' carbon dioxide. The growth of the photosynthesizers, conversely, warmed the Earth by renewing carbon dioxide and methane into the atmosphere (Lovelock, Ages of Gaia 80). This balance required no foresight or planning and evolved naturally from simple evolutionary processes. By the end of the Archean period, the atmospheric composition of oxygen greatly increased in an event known as the oxygen crises. This increase in oxygen resulted from both a decreasing supply of oxygen removers (iron and sulfur) from declining plate tectonic activity, and an increase in the amount of photosynthesizers producing oxygen (Lovelock, Healing Gaia 112). Little is known about the atmospheric composition of the Proterozoic period (2.5 - .7 billion years ago) which immediately followed the Archean. Consequently, most Gaian arguments of atmospheric regulation describe the Phanerozoic period (570 – 0.7 million years ago). Lovelock cites numerous mechanisms of Gaian atmospheric regulation during the Phanerozoic period. His mechanisms describe the consistency of Phanerozoic atmospheric compositions of oxygen, carbon dioxide, methane, carbon, and nitrogen. In Healing Gaia, Lovelock cites the following Gaian mechanisms to support his claims of Gaian homeostatic regulation:
Regarding carbon dioxide regulation: Ø Carbon dioxide cycles through the Earth from its source, volcanic outgassing, to its final sink, calcium carbonate (limestone). The atmospheric concentrations of carbon dioxide (currently 0. percent) depend on the balance between the rates at which it leaks in and is pumped out.
Ø As plants grow they break up surface rocks and draw carbon dioxide in the soil. There, carbon dioxide (dissolved in rainwater) reacts with basaltic rocks to form calcium bicarbonate, which washes to the oceans and is used by microscopic marine life to form shells. The ocean algae also pump down carbon dioxide from the air. When the algae die, their shells form chalk deposits on the ocean floor.
Regarding oxygen, methane, and carbon regulation: Ø Plants photosynthesize and convert carbon dioxide and water into oxygen and organic matter of composition approximately CH2O
Ø Animals and microorganisms consume most of this CH2O, using up the oxygen made by the plants and returning carbon dioxide to the air.
Ø Approximately one percent of the organic matter is buried in the soil, where methanogenes convert it to carbon dioxide and methane.
Ø The methane escapes into the air and reacts with the remaining one per cent of oxygen to form carbon dioxide and water.
Ø A small proportion (about 0.1 per cent) of the buried organic matter escapes digestion by the methanogenes. The carbon is buried deep in the sedimentary rocks and the equivalent oxygen is left free.
Ø It is thus the small amount of buried carbon that accounts for the oxygen in the air. All remaining oxygen made by the plants is consumed by animals and microorganisms, by reaction with the methane and with the rocks and gases during volcanic activity and weathering.
Regarding nitrogen regulation: Ø Lightning flashes combine nitrogen with oxygen; the oxides react with water and hydroxyl radicals to form nitric acid, which falls in rain and neutralizes to form nitrates.
Ø Without life, nitrates would lock up nitrogen as dissolved nitrate ions in the oceans. Life, however, reverses the flow as biofixation of nitrogen (the capture and conversion of nitrogen to biological compounds by nitrogen-fixing microorganisms) ensures a constant supply of useable "fixed" nitrogen for land and sea biota.
Ø Other microorganisms, the de-nitrifying bacteria, work on the detritus of life and return nitrogen to the atmosphere.
Regarding sulfur regulation: Ø When marine algae are eaten, sulfur betadine (electrically neural salts found in algae) decomposes to yield an acrylic acid ion and dimethyl sulfide.
Ø Onshore breezes carry the dimethyl sulfide inland where atmospheric gases decompose it into a non-sea salt sulfate aerosol comprised of sulfate and methane sulfonate.
Ø In this form sulfur is deposited on the ground, thereby enhancing the growth of land plants and increasing the rate of rock weathering (Lovelock Healing Gaia 108-119).
Ø If life on Earth were to cease, the atmospheric quantities of oxygen and nitrogen would decrease in concentration until they were merely trace elements. This lifeless Earth would have an atmospheric composition of water vapor, carbon dioxide and noble gases. The atmospheric composition of the Earth would be a reasonable interpolation between those of Mars and Venus, depending upon its position in the solar system (Lovelock, (Atmospheric Dimethyl Sulphide 579). Since the Earth's atmospheric conditions are ideal for life and have remained constant for the past 300 million years, Lovelock regards the preceding facts as evidence for the regulatory properties of Gaia. Lovelock also illustrates the following scenarios as evidence for Gaia. An increase in the Earth's atmospheric oxygen concentration to 25 per cent (from the present concentration of 21 per cent) would increase the probability of fires so that even the tropical rain forests would be at risk of combustion. A change in atmospheric pressure of 10 per cent, assuming that the composition remained constant, would cause a change of 4 degrees Celsius in the mean surface temperature; enough to provide unfavorable atmospheric conditions for life on Earth. Lovelock assumes that the probability of the biosphere interacting with the environment to regulate these delicate conditions is greater than the probability of these conditions arising randomly; therefore, Gaia regulates these conditions. Although Lovelock cites all of the previously listed information as evidence for the existence of Gaia, he states that "As yet there exists no formal physical statement of life from which an exclusive test could be designed to prove the presence of ‘Gaia' as a living entity" (579). Lovelock continues, saying: At present most biologists can be convinced that a creature is alive by arguments drawn from phenomenological evidence. The persistent ability to maintain a constant temperature and a compatible chemical composition in an environment which is changing or is perturbed if shown by a biological system would usually be accepted as evidence that it was alive." (579). Another of Lovelock's 1972 publications entitled "Atmospheric Dimethyl Sulfide and the Natural Sulfur Cycle" reports the first scientific findings discovered as a result of the Gaia hypothesis. This article addresses the well-known geochemical problem known as the sulfur gap. Essentially, the amount of sulfur that washes off the land into the oceans cannot be accounted for by all of the known sources of sulfur on land. Conventional wisdom regarding this issue assumed that hydrogen sulfide was emitted from the oceans, incorporated into the atmosphere, and replaced to the land by precipitation, thus balancing the sulfur budget. Lovelock doubted this hypothesis based on the premise that (1) the atmospheric quantities of hydrogen sulfide were not substantial enough to balance the sulfur budget, (2) the oceanic surface waters are too oxidizing to permit the necessary accumulation of hydrogen sulfide, and (3) hydrogen sulfide smells like rotten eggs and the odor of the sea is reminiscent of dimethyl sulfide. From the previous research of Frederick Challenger, Lovelock knew that marine organisms produced dimethyl sulfide to rid themselves of unwanted substances (Challenger 429). Since sulfur is the staple of existence for numerous land living organisms, Lovelock hypothesized that Earth's biota balanced the sulfur budget as a consequence of Gaian natural selection. With this Gaian mechanism in mind, he set out on a ship, the RSS Shackleton, to determine the atmospheric and oceanic quantities of dimethyl sulfide. In contrast to the conventional wisdom, he discovered that
dimethyl sulfide was ubiquitous in the atmosphere and available in sufficient quantities to potentially balance the sulfur budget. Since organisms were producing the dimethyl sulfide and therefore balancing the sulfur budget, Lovelock regards this process as possible evidence for Gaia (579). In 1974, Lovelock and Margulis published two papers entitled "Atmospheric homeostasis by and for the biosphere: the Gaia hypothesis", and "Homeostatic Tendencies of the Earth's Atmosphere". These two papers laid the theoretical framework for the Gaia hypothesis by addressing Gaia's philosophical foundations and offering thermodynamic and biogeochemical evidence for Gaia. At this time, Lovelock and Margulis defined the Gaia hypothesis as: The hypothesis that the total ensemble of living organisms which constitute the biosphere can act as a single entity to regulate chemical composition, surface pH and possibly also climate. The notion of the biosphere as an active adaptive control system able to maintain the Earth in homeostasis we are calling the ‘Gaia' hypothesis…Hence forward the word Gaia will be used to describe the biosphere and all of those parts of the Earth with which it actively interacts to form the hypothetical new entity with properties that could not be predicted from the sum of its parts (Lovelock and Margulis "Atmospheric Homeostasis" 3). In 1979, Lovelock published his first book on the Gaia Hypothesis entitled Gaia: A New Look at Life on Earth. This book, though relatively short in length (merely 150 pages), interested both scientists and laypersons. In this book Lovelock describes the Gaia hin a bare bones scientific approach. "I tried to write this book so that a dictionary is the only aid needed" (vii). Because of Lovelock's simplistic writing style and the controversial nature of the topic, A New Look at Life on Earth received considerable critical review from the scientific establishment. Although the Gaia Hypothesis has undergone extensive revision since its first introduction, many critics look no farther than the arguments presented in A New Look at Life on Earth as the basis for their criticisms. In A New Look at Life on Earth, Lovelock describes Gaia as: A complex entity involving the earth's biosphere, atmosphere, oceans, and soil; the totality constituting a feedback or cybernetic system which seeks an optimal physical and chemical environment for life on this planet. The maintenance of relatively constant conditions by active control may be conveniently described by the term ‘homeostasis' (11). Of the atmosphere, Lovelock explains "The atmosphere is not merely a biological product, but more probably a biological construction: not living, but like the cat's fur, a bird's feathers, or the paper of a wasp's nest, an extension of a living system designed to maintain a chosen environment" (10). Lovelock also stated: I have frequently used the word Gaia as a shorthand for the hypothesis itself, namely that the biosphere is a self-regulating entity with the capacity to keep our planet healthy by controlling the chemical and physical environment. Occasionally it has been difficult, without extensive circumlocution, to avoid talking of Gaia as if she were known to be sentient. This is meant no more seriously than is the appellation ‘she' when given to a ship by those who sail her, as a recognition that even pieces of wood and metal when specifically designed and assembled may achieve a composite identity with its own characteristic signature, as distinct from being the mere sum of its parts. (xii). In A New Look at Life on Earth, Lovelock lists numerous examples of Gaian regulatory mechanisms. These mechanisms include the relationships between methane, oxygen, carbon dioxide, and nitrogen in the atmosphere, the chemistry and salinity of the oceans, numerous examples of positive and negative feedback, and the possible relationship between Gaia and plate
persists. Gaia, as a total planetary being, has properties that are not necessarily discernable by just knowing individual species or populations of organisms living together (19).
In 1990 Lovelock first stated that the Gaia theory was testable. In his article "Hands up for the Gaia hypothesis", Lovelock describes numerous predictions, tests, and resulting conclusions spawned from the study of Gaia. In this article, Lovelock states: In many ways Gaia, like an invention, is difficult to describe. The nearest I can reach is to call Gaia the theory of an evolving system – a system made from the living organisms of the Earth, and from their material environment, the two parts being tightly coupled and indivisible. This evolutionary theory views the self-regulation of climate and chemical composition as emergent properties of the system. The emergence is entirely automatic; no teleology is invoked (102). He also questions Gaia's unpopularity among scientists, citing as the obvious reason "the natural inertia of science which means that large-scale theories are digested only slowly. It took forty years for another Earth theory, plate tectonics, to be accepted" (102). Lovelock's most recent book, Healing Gaia, was published in 1991. This book presents Gaia in a strict geophysiological manner. In the preface to Healing Gaia, Lovelock writes that he explores Earth "through the eyes of an imaginary planetary physician" (6). In Healing Gaia, Lovelock clearly outlines the context under which he defines a living Earth. Lovelock states: In this book I often describe the planetary ecosystem, Gaia, as alive because it behaves like a living organism to the extent that temperature and chemical composition are actively kept constant in the face of perturbations. When I do I am well aware that the term itself is metaphorical and that the Earth is not alive in the same way as you or me, or even as a bacterium. At the same time I insist that Gaia theory itself is proper science and no mere metaphor. My use of the term "alive" is like that of an engineer who calls a mechanical system alive to distinguish its behavior when switched on from that when switched off, or dead. Engines on whose proper function many lives depend have health monitors; devices that ensure signs of failure are detected early enough for a cure, not a tragedy (6). In 1995, Lovelock published "New Statements on the Gaia Theory." In this article Lovelock defines Gaia as a "planet-sized ecosystem…something that emerged when organisms and their material environment evolved together" (296). He also states that "Gaia is…a straightforward scientific theory about the Earth and the organisms that inhabit it. A theory that views the Earth as if it were alive. As if it were able to regulate the climate and chemistry to keep it comfortable for life (298). Lovelock makes the remark in "New Statements on the Gaia Theory" that "Gaia theory is testable and has a proper mathematical basis in a set of closely coupled differential equations" (298). In this article, Lovelock presents a list of predictions from Gaia Theory that has led to "significant planetary discoveries" (299). Table 1 paraphrases these predictions. Table 1.
Some Predictions from Gaia theory that have led to significant planetary discoveries
Some Predictions from Gaia theory that have led to significant planetary discoveries Year Prediction Test, result, and year 1968 That Mars was lifeless (from Viking Mission, 1977. Strong
atmospheric evidence). Confirmation. 1971 That organisms would make Dimethylslphide and methyliodide compounds that can transfer essential both found, 1973. elements from the oceans o the land surfaces. 1973 That oxygen has stayed at 21 + or -5% Still under test of total atmospheric gases for the last 200 million years. 1981 That climate may be regulated by Microorganisms greatly increase the control of carbon dioxide rock weathering, 1989. concentration through biologically enhanced rock weathering. 1987 That climate regulation via cloud Still under test. Evidence that oceanic density control is linked to algal cloud cover geographically matches sulfur as emissions. algal distribution, 1990. 1988 That Archean atmospheric chemistry Still under test. was dominated by methane
Criticisms of Gaia
There are 3 major criticisms of Gaia. In order to fully understand the implications of Gaia, it is necessary to examine these criticisms and Lovelock's subsequent responses to them. The first criticism states that Gaia is unnecessary to explain the history of the Earth. This criticism is an extension of the conventional wisdom that regards the Earth's atmospheric chemistry as the end result of volcanic outgassing and subsequent abiological chemical reactions. The second criticism states that Gaia is teleological, or would require foresight and planning to regulate the biogeochemistry of the Earth. The third criticism states that Gaia is untestable. The first major criticism, that Gaia is unnecessary to explain the history of the Earth, is predominately argued by Heinrich Holland, a geochemist at Harvard University. In Holland's 1984 book, The Geochemical Evolution of the Atmosphere and the Oceans, Holland states:
I find the hypothesis intriguing and charming, but ultimately unsatisfactory. The geologic record seems much more in accord with the view that organisms that are better able to compete have come to dominate, and that the Earth's near surface environment and processes have accommodated themselves to changes wrought by biological evolution. Many of these changes have been fatal or near fatal to parts of the contemporary biota. We live on an Earth that is the best of all worlds but only for those who have adapted to it (539).
Lovelock responded to Holland's criticism saying: I do not think that able scientists, such as Holland, would have rejected Gaia with such feeble criticism were it not for their faith in conventional wisdom. Had they taken thought they would have noticed that the world is massively modified by living organisms. The air, the oceans, and the rocks are all either made by living organisms, or else changed by their presence. Organisms do not just
The third major criticism, that Gaia is untestable, is predominantly argued by James Kirchner, a theoretical ecologist from Berkeley. Kirchner first expressed his criticisms in 1988 at the American Geophysical Union's (AGU) Chapman Conference. The Chapman Conference is a biannual symposium dedicated to a specific topic or branch of earth science. In 1988, the entire week-long conference was devoted to the study of the Gaia Hypothesis. Of all the critics present at the 1988 AGU Chapman Conference, James Kirchner stood out as the most noteworthy. Kirchner's criticisms challenged the validity of Gaia as a hypothesis and means for scientific inquiry. In his arguments, Kirchner divided Gaia into numerous hypotheses and analyzed each for its validity and scientific testability. By illustrating the vast ambiguities of Gaia, Kirchner has become one of Lovelock's most valued critics. In his 1989 AGU publication "The Gaia hypothesis: Can it be Tested?," Kirchner pursues the testability of the Gaia hypothesis. He illustrates that much of the confusion resulting from Gaia stems from that fact that numerous distinct hypotheses have been proposed under the single name "the Gaia hypothesis." To clarify the resulting confusion, Kirchner divides Gaia into four distinct statements or hypotheses. These distinct hypotheses are: Coevolutionary Gaia, Homeostatic Gaia, Geophysiological Gaia, and Optimizing Gaia. Using these four hypotheses, Kirchner analyzes each for its testability and scientific validity. Kirchner's "Coevolutionary Gaia" is the notion that life on Earth influences the environment and that, in turn, the environment influences the evolution of life on Earth by Darwinian processes of evolution (224). Kirchner uses a quote from Lovelock and Watson (Lovelock and Watson 284) to illustrate this "hypothesis:" The biota has effected profound changes on the environment of the surface of the earth. At the same time, that environment has imposed constraints on the biota, so that life and the environment may be considered as two parts of a coupled system…perturbations of one will affect the other and this may in turn feed back on the original change. The feedback may tend to either enhance or diminish the initial perturbation, depending on whether its sign is positive or negative (224). Kirchner's Homeostatic Gaia is the notion that life on earth influences the environment in a stabilizing manner; the major linkages between life and the environment being negative feedback loops (224). To illustrate this hypothesis, Kirchner quoted Lovelock and Margulis (Atmospheric Homeostasis 2-9): From the fossil record it can be deduced that stable optimal conditions for the biosphere have prevailed for thousands of millions of years. We believe that these properties of the terrestrial atmosphere are best interpreted as evidence of homeostasis on a planetary scale maintained by life on the surface (224). Kirchner's Geophysiological Gaia is the notion that the biosphere can be compared with a single immense organism. This organism may exhibit homeostatic and unstable behavior like any other organism (224). Kirchner quoted Lovelock to illustrate this idea "Gaia theory suggests that we inhabit and are part of a quasi-living entity that has the capacity for global homeostasis" (Geophysiology 11-23). Kirchner's Optimizing Gaia is the notion that earth's biota manipulates its physical environment in ways that create favorable conditions for itself (225). To illustrate Optimizing Gaia, Kirchner quoted Lovelock and Margulis:
We argue that 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 of time, just those optimal for surface life. Rather we present the "Gaia hypothesis" the idea that energy is expended by the biota to actively maintain these optima conditions (Homeostatic Tendencies 93) Kirchner also quoted Lovelock "The most important property of Gaia is the tendency to optimize conditions for all terrestrial life" (A New Look 157). After presenting these four distinct Gaia hypotheses, Kirchner dismisses each as untestable and scientifically invaluable. In formulating his arguments, Kirchner defines the following criteria for testability:
Ø Ill-defined hypotheses are untestable because they can be endlessly reinterpreted to fit almost any data. For the same reason, they cannot contain specific empirical information for they exclude no possibilities.
Ø Tautological hypotheses are untestable because they are true by definition; their conclusions are entirely contained within their premises.
Ø Unfalsifiable hypotheses are untestable because they fail to make falsifying predictions. Confirmation of these hypotheses does not exclude data because unfalsifiable hypotheses contain no empirical content and no excluding data (data inconsistent with the hypothesis) (226).
Of Coevolutionary Gaia, Kirchner argues that Lovelock simply restates the obvious and well-documented fact that life influences the environment. Kirchner cites numerous examples, dating as far back as 1844 that illustrate the premise that biological processes alter the physical environment. Kirchner states "An observation that is so widely recognized lacks the tentative character of a true hypothesis" (227). In criticizing Homeostatic Gaia, Kirchner divides the hypothesis into two separate forms: weak and strong. The weak form of Homeostatic Gaia states that "the dominant interactions between the biotic and abiotic worlds are stabilizing" (227). The strong form states that "these dominant interactions make the Earth's physical environment significantly more stable than it would have been without life" (227). Kirchner states that climatic homeostasis alone is not evidence for Gaia because it is impossible to determine whether the climate is stable as a result of those biological processes or regardless of them. He criticizes the proposed feedback mechanisms of Gaia because it unclear whether these mechanisms are stabilizing or destabilizing. Without the ability to determine which mechanisms are destabilizing, or tend to weaken homeostasis, Kirchner argues it is impossible to understand an organism's homeostatic regulatory function. Kirchner criticizes that Homeostatic Gaia is unfalsifiable. To support this claim, he points to Lovelock's explanation of the oxygen crisis, the switch from oxidizing to reducing conditions in the Precambrian atmosphere. Lovelock cites the fact that terrestrial life survived the oxygen crises as evidence for Gaia's ability to adapt to changing conditions. In response, Kirchner states: If the most destabilizing biotic event in Earth's history can be construed as evidence for Gaia, and the relative stability since then can also be cited as evidence for Gaia, one wonders what conceivable
editor for Kirchner's anti-Gaian articles, and that in the credits to his 1991 paper entitled "the Gaia Hypotheses: Are they testable? Are They Useful?" Kirchner states "I particularly want to acknowledge Jim Lovelock's gracious response to this paper at the conference. I wish that all scientific debates could be as free of acrimony" (46). Lovelock, however, has not remained silent to Kirchner's criticisms. In his 1989 paper, Kirchner criticized the notion of Gaia as a living organism in more than one reference. This view of Gaia, although implied in some of Lovelock's earlier writings, no longer applied to his definition of Gaia by the late 1980's. To this, Lovelock responded "Our thoughts have evolved over the last 20 years. In the early stages one tended to speak poetically. I hope that we are now speaking more scientifically" (Kerr 393). Although by 1988, Lovelock was not claiming that the Earth was an immense organism, he called Kirchner's criticisms of Homeostatic (strong) Gaia "a clear-cut demolition of Gaia"(Kerr 393) and admitted that all remaining notions of Gaia as an actual living organism must be abandoned. In light of the preceding arguments, the question that still remains is: which of Kirchner's criticisms are still valid and should be taken into account when determining the feasibility of a testable Gaia? Of Kirchner's four distinct hypotheses, only two hypotheses are relevant to this analysis. Kirchner's Coevolutionary Gaia, which states that Lovelock simply reiterates the conventional wisdom concerning life's influence on earth, will not be analyzed. This criticism was adequately answered by Lovelock when he made the statement (previously quoted), "Organisms do not just "adapt" to a dead world determined by chemistry and physics alone. They live with a world that is the breath and bones of their ancestors and that they are now sustaining" (The World 25). Independent of whether Lovelock is correct in making this statement, he refutes Kirchner's criticism, thus leaving it invalid. In addition, this criticism, even if valid, is independent of Gaia's testability and therefore irrelevant to the scope of this analysis. Kirchner's Geophysiological Gaia, which states that the Earth can be compared to a single immense organism, will not be pursued. As previously mentioned, although in the past Lovelock may have implied that the Earth is a living organism, he clearly recanted this idea in 1988 (Kerr 393). Kirchner's criticisms of Geophysiological Gaia are thus outdated, irrelevant, and not important to the scope of this analysis. Having refuted Coevolutionary Gaia and Geophysiological Gaia, it is thus Optimizing Gaia, and Homeostatic Gaia that must be analyzed in order to determine the feasibility of a testable Gaia hypothesis.
The Nature of Science and Scientific Testability
Kirchner's criticisms of Homeostatic and Optimizing Gaia primarily concern the untestable nature of these hypotheses. Surficially, Kirchner provides logical, deductive arguments illustrating the untestable nature of Gaia. In the context of his criticisms, Kirchner's evidence is convincing that Gaia, both Homeostatic and Optimizing, is untestable. It is naïve, however, to brand Gaia as untestable without thoroughly exploring different types of scientific testability and their philosophical foundations. A complex system such as Gaia cannot simply be accepted or rejected based upon simple verification or falsification tests. The testability of Gaia can only be determined
by careful analysis of many philosophical issues regarding its testability. This chapter outlines the philosophical foundations governing scientific and ecological testability.
Popperian Falsificationism In his 1989 paper, "The Gaia Hypothesis: Can it be tested," Kirchner explains "the minimal criteria of testability can be stated concisely" (226). He continues: In order to be testable a hypothesis must be clear, and its terms must be unambiguous. It must be intelligible in terms of observable phenomena. And most importantly, it must generate predictions of two kinds: confirmatory predictions (phenomena that should be observed if the hypothesis is true and that would not be predicted by the existing body of accepted theory) and falsifying predictions (phenomena that should be observed if the hypothesis is false) (226). Kirchner's ideas regarding testability stem from the early works of Karl Popper, a notable philosopher of science. Kirchner quotes and paraphrases Popper extensively in "The Gaia Hypothesis: Can it be tested.." Popper is one of many philosophers who has attempted to create a definition of science. Throughout much of his career, Popper was concerned with a method of systematically distinguishing science from pseudoscience. He viewed the study of physics as the epitome of science, and Marxism and Freudism as examples of pseudoscience. Popper's method of scientific inquiry was entitled ‘falsificationism,' and considered a theory scientific as long as it: (1) was liable to be falsified by data (2) was testable by observation and experiment and (3) made valid predictions. The ideas expressed in Popper's ‘falsificationism' have become mainstream and are currently accepted and labeled ‘the scientific method' by numerous textbooks and bureaucratic establishments. Falsificationism is not universally accepted, however, and has received substantial criticisms from philosophers of science and scientists alike, namely biologists. Many of these criticisms stem from the fact that in his early writings, Popper strongly argued that evolutionary theory was unfalsifiable and therefore (Popper 230). Popperian critics argue that biological theories are inherently different from the theories of chemistry or physics and therefore cannot be tested by the same means. Later in life Popper recanted his arguments against evolutionary theory and altered his scientific philosophy to incorporate biological theories; however, many misconceptions of his position still linger from his early writings. Ernst Mayr, a notable biologist and philosopher of science from the Technical University of Munich, refutes many aspects of Falsificationism. In his 1988 book, Towards a New Philosophy of Biology, Mayr argues against the notion that falsificationism can be equally applied to all of the sciences. He states: Popper's claim…allows one rather neatly to delimit science from nonscience: any claim which in principle cannot be falsified is outside the realm of science...Falsification, however, is sometimes as difficult to provide as absolute proof. It is therefore not considered the only measure for obtaining scientific acceptability (26).
Concerning the applicability of falsificationism to Gaia, Lovelock writes: Geophysiology is about the evolution of a tightly coupled system whose constituents are the biota and their material environment, which comprises the atmosphere, the oceans, and the surface rocks. Self-regulation of important properties, such as climate and chemical
Holism Whereas theories of reductionism tend to split apart scientific methodologies into component parts, theories of ‘holism' tend to view complex systems as whole, integrated, systems. Holism is the idea that the components of a system can only be understood in context of that system. A holistic approach to science is opposite a reductionist approach and scientists tend to favor either reductionism or holism, rarely both. The division between reductionists and holists in science is pronounced, and especially so in the study of ecology. Since Gaia can be viewed as a planetary ecosystem, it is necessary to examine the following philosophical aspects of ecology. The Implications of Reductionism and Holism to the Study of Ecology The science of ecology has undergone significant paradigm shifts since its origin towards the end of the last century. Ecology began as a very holistic science that studied communities, or associations of organisms. As part of this early holistic approach, communities of organisms were not studied in isolation, but in context of the whole system or their environment. Both Frederick Clements and Victor Shelford, two prominent early American ecologists defined ecology as the ‘science of communities'. In the early 1930's, the Oxford ecologist Arthur Tansley coined the term ‘ecosystem', defining it as a "community taken together with its abiotic environment" (Goldsmith 64). Around 1950 however, Ecology (along with many other scientific disciplines) shifted from a primarily holistic science to a reductionist science. According to Edward Goldsmith: Ecology has undergone, about a half century later than genetics and evolution, a transformation so strikingly similar in both outline and detail that one can scarcely doubt its debt to the same materialistic and probabilistic revolution. An initial emphasis on a similarity of isolated communities replaced by concern about their differences: the examination of groups of populations largely superceded by the study of individual populations; belief in deterministic succession shifting with the widespread introduction of statistics into ecology, to realization that temporal community development is probabilistic: and a continuing struggle to focus on material, observable entities rather than ideal constructs" (Goldsmith 65). Although the development of systems theory and numerous ‘bottom-up' methods of viewing ecology have emerged in the last twenty years, since the 1950's reductionism has pervaded as the dominant paradigm in the sciences of ecology and biology. Within this reductionist paradigm, Gaia, as a holistic approach to science, received staunch criticisms since its first proposal. Many scientists and philosophers are currently extremely unsatisfied with the reductionist paradigm of ecology. According to Edward Goldsmith: Ecology has in fact been perverted – perverted in this interests of making it acceptable to the scientific establishment and to the politicians and industrialists who sponsor it…it is unlikely that those ecologists who view the biosphere in purely reductionistic and mechanistic terms can understand the implications of the devastation being wrought by the modern industrial system, and hence they can understand what action is required to bring this devastation to an end. (65). Numerous scientists and philosophers of science doubt the wisdom of applying reductionist principles to the life sciences. In The Growth of Biological Thought Ernst Mayr writes: This discussion of reductionism can be summarized by saying that the analysis of systems is a valuable method, but that attempts at a "reduction" of purely biological phenomena or concepts to
laws of physical sciences has rarely, if ever, led to any advance in our understanding. Reduction is at best vacuous, but more often a thoroughly misleading and futile, approach (63). Summarizing the applicability of reductionism to the life sciences, Stephen Jay Gould states: First nothing in biology contradicts the laws of physics and chemistry; any adequate biology must be consonant with the "basic" sciences. Second, the principles of physics and chemistry are not sufficient to explain complex biological objects because new properties emerge as a result of organization and interaction. These properties can only be understood by the direct study of whole, living systems in their normal state. Third, the insufficiency of physics and chemistry to encompass life records no mystical addition, no contradiction to the basic sciences, but only reflects the hierarchy of natural objects and the principles of emergent properties at higher levels of organization (From Barlow, 103).
General System Theory as it Relates to the Study of Ecology
It was these ideas concerning the hierarchical organization within the life sciences that spawned general system theory (GST) in the late 1960's. Under the framework of GST, a holistic approach to science, ecosystems are examined as complex, integrated systems. Recent developments in GST have revolutionized the study of ecology and numerous other complex systems. A ‘systems' approach to ecology and other complex systems offers an alternative approach to the traditional reductionist methods of evaluating ecosystems. GST is therefore important to the study of ecological modeling and Gaia. The notions of ‘systems' science first became widespread in the 1960's as the limitations of reductionist science became apparent. Since then, GST has been applied to all disciplines of science. In relation to ecology, GST regards every organism as a system, or a "complex of elements in mutual interaction…circumscribed in space and time" (Bartlow 12). The major ecological implications of GST can be summarized by two basic premises. First, it is impossible to resolve the phenomena of life completely into its elementary units because each individual part depends not only on conditions within itself, but also to the conditions within the whole. Therefore, the behavior of an isolated part is inherently, different from it behavior within the context of the whole. Secondly, the whole shows emergent properties, or properties that are not merely the sum of its parts. As a result, as long as we single out individual phenomena, we do not discover any fundamental difference between the living and the non-living (112). The introduction of GST was important to ecology because it provided an alternative framework for viewing complex systems. GST paved the way for scientifically acceptable, holistic interpretations of ecological phenomena. Another theory which dramatically altered the foundations of ecology was chaos theory. By illustrating that complex systems exhibit unpredictable or chaotic behavior, chaos theory greatly modified the concept of scientific and ecological testability.
Chaos Theory as it Relates to the Study of Ecology
Chaos theory is the notion that complex systems exhibit inherently random or unpredictable behavior. This behavior was first noticed by Edward Lorenz, a meteorologist at the Massachusetts Institute of Technology, in 1960. Lorenz, while manipulating, a computerized weather model noticed that small changes in input data resulted in unusually large changes of output data. This
