gaia hypothesis conclusion

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The Gaia hypothesis: Earth has its own life and we are part of a super organism

Hundreds of ‘black spiders’ spotted in mysterious ‘inca city’ region on mars, astronomers discover a space structure of unknown origin larger than the milky way galaxy, over 2 miles thick water ice buried beneath mar’s equator discovered, enough to cover the entire planet in a shallow ocean if melted, ancient tree contains record of earth’s record of earth’s magnetic field in its rings.

In the realm of scientific exploration, the Gaia hypothesis has sparked significant intrigue and debate.

This revolutionary concept suggests that planet Earth operates as a single, interconnected organism, where all living beings and their environments form a complex and self-regulating system.

Table of Contents

Introduction:.

Coined by renowned scientist James Lovelock in the 1970s, the Gaia hypothesis challenges conventional thinking about the relationship between life and its planetary environment. This article delves into the intricacies of the Gaia hypothesis, explores its scientific underpinnings, and examines its implications for our understanding of Earth as a living superorganism.

Unraveling the Gaia Hypothesis: A Paradigm Shift in Ecological Thinking

The Gaia hypothesis proposes that Earth is not merely a lifeless rock supporting life but an integrated and self-regulating entity. The term “Gaia” originates from Greek mythology, referring to the ancient goddess personifying the Earth. Lovelock’s hypothesis presents an alternative perspective, suggesting that Earth itself exhibits characteristics of a living organism.

Gaia: A Dynamic Self-Regulating System

The reference article provides an in-depth analysis of the Gaia hypothesis, exploring its scientific foundations. It outlines the concept of Earth as a self-regulating system, where living organisms and their environment maintain a delicate balance, allowing for the sustenance and evolution of life. The reference article highlights key findings and research that support the Gaia hypothesis, emphasizing the intricate interconnections between biological, geological, and atmospheric processes.

NASA Spacecraft Hears A Strange “Hum” From Beyond The Solar System

Scientists Discover ‘Secret Symmetries’ protecting Earth from the chaos of space

The Gaia Hypothesis in Action: Homeostasis and Feedback Mechanisms

A fundamental principle of the Gaia hypothesis is the presence of homeostasis, a state of equilibrium that allows the planet to maintain stable conditions conducive to life. Feedback mechanisms, both positive and negative, play a crucial role in regulating Earth’s systems. These mechanisms ensure that any disturbances or changes are counteracted, helping the planet adapt and sustain the delicate balance necessary for the continuity of life.

Gaia and the Biosphere: A Symphony of Life

The Gaia hypothesis recognizes the biosphere—the zone where life flourishes—as a critical component of Earth’s living superorganism. From microorganisms to plants, animals, and humans, all organisms interact with their environment, exchanging vital elements and energy. This intricate web of life forms a symphony of interdependent relationships, working harmoniously to support the collective survival and thriving of the biosphere.

Gaia and Earth’s Climate: A Coordinated Dance

Climate plays a significant role in the Gaian perspective, as it impacts the stability of Earth’s systems and the distribution of life. The reference article sheds light on the intricate connections between Gaia and climate, highlighting how Earth’s living organisms, such as plants and algae, actively participate in regulating atmospheric composition and temperature. The balance between greenhouse gases and other climatic factors is influenced by the intricate interactions within the biosphere.

Gaia and Human Interactions: Our Responsibility as Stewards

As conscious inhabitants of Earth, humans hold a unique position within the Gaian framework. Our actions, choices, and impact on the planet play a pivotal role in shaping the health and longevity of Earth’s living superorganism. The Gaia hypothesis calls for a shift in our perception of the planet, emphasizing the importance of environmental stewardship, sustainable practices, and the preservation of biodiversity.

Criticisms and Debates: Challenging the Gaia Hypothesis

No scientific hypothesis is immune to criticism, and the Gaia hypothesis is no exception. Skeptics argue against the notion of Earth as a living organism, citing the lack of clear mechanisms and empirical evidence to support the hypothesis. Some critics contend that the apparent self-regulation observed in Earth’s systems can be attributed to natural physical and chemical processes rather than a conscious, living entity. Additionally, the idea of Gaia as a single, unified organism faces challenges regarding the delineation of its boundaries and the mechanisms by which it functions.

Despite the criticisms, proponents of the Gaia hypothesis argue that it provides a useful framework for understanding the complex interactions between life and the environment. They point to various lines of evidence that support the idea of Earth as a self-regulating system. For example, the regulation of atmospheric composition by living organisms, such as the balance of oxygen and carbon dioxide, suggests a feedback mechanism that maintains a suitable environment for life.

Gaia and the Future of Earth: Implications and Applications

The Gaia hypothesis has far-reaching implications for our understanding of Earth’s past, present, and future. By recognizing Earth as a living superorganism, we gain insights into the fragility and resilience of our planet. The concept of Gaia prompts us to consider the long-term consequences of human activities on Earth’s systems, from the exploitation of natural resources to the effects of climate change. By embracing the Gaian perspective, we can adopt a holistic approach to environmental management and work towards sustainable practices that promote the well-being of both the planet and its inhabitants.

The Gaia hypothesis also has practical applications in fields such as ecology, conservation, and environmental policy. Understanding Earth as a living system encourages scientists and policymakers to consider the interconnectedness of ecological processes and the potential impacts of human actions on the planet’s health. By applying the principles of Gaia, we can develop strategies for biodiversity conservation, land management, and climate change mitigation that take into account the complex interactions within the biosphere.

Gaia and the Frontiers of Scientific Exploration

As our understanding of Earth and its interconnected systems continues to evolve, the Gaia hypothesis remains an intriguing avenue for scientific exploration. Researchers are delving into various aspects of Gaia, such as investigating the role of microbial communities in regulating global biogeochemical cycles, studying the potential influence of biodiversity on Gaian stability, and exploring the impact of human-induced changes on Earth’s self-regulation. Through ongoing research, scientists aim to unravel the complexities of Earth’s living superorganism and expand our knowledge of the interconnectedness between life and its environment.

Collaboration between scientific disciplines is crucial in advancing our understanding of Gaia. By integrating insights from ecology, geology, atmospheric sciences, and other fields, researchers can gain a comprehensive understanding of the intricate web of interactions that shape Earth’s systems. Furthermore, interdisciplinary collaboration fosters dialogue between scientists, philosophers, and scholars, leading to a more holistic and integrated understanding of the Gaia hypothesis and its broader implications.

Conclusion:

The Gaia hypothesis challenges us to reimagine Earth as a living superorganism, where all elements of the biosphere are interconnected and contribute to the planet’s self-regulating systems. Despite criticisms and debates, the hypothesis has sparked profound discussions and inspired new avenues of scientific exploration.

By embracing the Gaian perspective, we gain a deeper understanding of the delicate balance that sustains life on Earth and our responsibility as stewards of the planet. The Gaia hypothesis encourages us to strive for sustainable practices, environmental stewardship, and a harmonious relationship between humanity and nature. As we continue to uncover the complexities of Earth’s living superorganism, interdisciplinary collaboration and further scientific exploration will contribute to expanding our knowledge and understanding of Gaia and its implications for the future of our planet.

Ongoing research and exploration into the Gaia hypothesis hold the potential to shed light on critical questions about Earth’s systems and their interconnections. Scientists are investigating the role of microbial life in shaping planetary processes, studying the influence of biodiversity on the stability of Gaia, and exploring the intricate feedback mechanisms that maintain Earth’s homeostasis. By delving into these frontiers of scientific exploration, we can deepen our understanding of the complex interactions that sustain life on our planet.

The Gaia hypothesis also serves as a source of inspiration for technological innovations and practical applications. As we recognize the interconnectedness of Earth’s systems, we can seek solutions that mimic the self-regulating mechanisms found in nature. Biomimicry, for example, draws inspiration from Gaian principles to develop sustainable and efficient technologies that work in harmony with the planet. By emulating the resilience and adaptability of Earth’s living systems, we can strive towards a more sustainable future.

Moreover, the Gaia hypothesis holds profound philosophical implications. It challenges us to question our relationship with the natural world and our role as inhabitants of Earth. By perceiving the planet as a living superorganism, we are reminded of our interconnectedness and interdependence with all life forms. This perspective fosters a sense of responsibility and stewardship towards the environment, encouraging us to make choices and take actions that support the well-being of the entire Earth community.

In conclusion, the Gaia hypothesis presents a paradigm-shifting perspective on the nature of our planet. By viewing Earth as a living superorganism, we gain insights into the intricate web of interactions that sustain life and maintain the delicate balance of our biosphere.

While facing criticisms and ongoing scientific debates, the Gaia hypothesis has inspired profound discussions, interdisciplinary collaborations, and scientific exploration. By embracing the Gaian perspective, we can deepen our understanding of Earth’s interconnected systems, foster sustainable practices, and promote a harmonious relationship between humanity and the natural world. Through ongoing research, technological innovation, and philosophical contemplation, we can continue to unravel the mysteries of Gaia and strive towards a future where the well-being of our planet and all its inhabitants are upheld.

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10 Conclusions

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This concluding chapter evaluates the Gaia hypothesis. Based on the evidence studied in this book, the chapter argues that the Gaia hypothesis is not a reasonable picture of how Earth and life interact with each other. There is no single body of facts or line of unimpeachable reasoning that sways the debate conclusively in favor of Gaia. The lack of any established bottom-up mechanism that can explain how Gaia is produced also weighs against it. No one has been able to explain convincingly how Gaia could emerge out of evolutionary or ecological dynamics. It is therefore perhaps not surprising that major evolutionary advances, such as the evolution of oxygenic photosynthesis, or the first foresting of the land by sizeable trees, have been associated with environmental catastrophes.

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The Gaia Hypothesis, Evolution and Ecology

• First Online: 15 April 2021

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The Gaia hypothesis was introduced in the 1970s by James Lovelock and Lynn Margulis. The original idea proposed that near homeostatic conditions on Earth have been maintained “by and for the biosphere”. A major justification for this approach was that the atmospheric composition for an anabiotic Earth would be quite different from the observed one. However, the authors did not provide details of how these calculations were made and on the basis of the biogeochemical cycles knowledge at that time (fifty years ago) it is quite dubious that those results represented reality.

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By Muddiman, S.  (2019).

This book bridges the gap between economic and ecological theory and practice. Its main focus is on how the principles of the Austrian School of economics could improve the validity of Ecosystem Services.

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Earth System Analysis

By Schellnhuber, H. (Ed), Wenzel, V. (Ed)  (1998).

As humanity approaches the 3rd millennium, the sustainability of our present way of life becomes more and more questionable. New paradigms for the long-term coevolution of nature and civilization are urgently needed in order to avoid intolerable and irreversible modifications of our planetary environment. Earth System Analysis is a new scientific enterprise that tries to perceive the earth as a whole, a unique system which is to be analyzed with methods ranging from nonlinear dynamics to macroeconomic modelling.

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Gaia’s Body

By Volk, T.  (1998).

Is Earth alive? Put more rigorously, is the biosphere a self- sustaining meta-organism? This is the essence of Gaia theory: if the biosphere really is a single coherent system, then it must have something like a physiology. It must have systems and processes that perform living functions. OK, then, what systems, what processes, what functions? Gaia's Body is Tyler Volk's answer to this question. In this book, he describes the environment that enables the biosphere to exist; various ways of looking at its “anatomy” and “physiology,” the major biogeographical regions such as rainforests, deserts, and tundra; the major substances the biosphere is made of; and the chemical cycles that keep it in balance.

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The Biosphere

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Long unknown in the West, The Biosphere established the field of biogeochemistry and is one of the classic founding documents of what later became known as Gaia theory. It is the first sustained expression of the idea that life is a geological force that can change Earth's landforms, its climate, and even the contents of its atmosphere. A complete, unabridged translation has never before been available in English. This edition - complete with extensive annotations, an introductory essay placing the work in its historical context and explaining its relevance to readers today, and a foreword cosigned by a stellar group of international experts - will be the definitive edition of this classic work.

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The Dynamics of Small Solar System Bodies

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This SpringerBrief summarizes the latest relevant research and discoveries that have been made in the area of ringed small bodies and small body taxonomy, including those that lay the groundwork for future discoveries.

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The Earth System and Evolution of Life

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During the last 200 years since Geology has been established as an integrated science, nearly the same duration as modern Biology, our understanding of the Earth has taken great leaps forward through the works of several experts, and by contributions from a large number of scientific community. In the 21st Century, however, we face a massive challenge to understand and integrate the voluminous data and break-through made in several fields of Genome-Biology, Astronomy, Climate in the near future, fast depleting resources and the fate of human beings in this Planet. The well illustrated chapters in this book provide a succinent summary of the multi-disciplinary nature of science and attempts to bridge genome-level biology through astronomy and earth history.

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Understanding the Earth System

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This volume includes revised versions of most of the presentations made at the International Conference «Understanding the Earth Sys­ tem: Compartments, Processes and Interactions” held on November 24–26, 1999 in Bonn. The Conference was organized by the German National Committee on Global Change Research as part of the Bonn Science Festival 1999–2000.

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Visconti, G. (2021). The Gaia Hypothesis, Evolution and Ecology. In: Visconti, G. (eds) Climate, Planetary and Evolutionary Sciences. Springer, Cham. https://doi.org/10.1007/978-3-030-74713-8_11

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The Gaia hypothesis

The evolution of life and the atmosphere.

• The biosphere and Earth’s energy budget
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• Climate, humans, and human affairs

• What is a climate classification?
• Are there different kinds of climate classifications?
• Who was Wladimir Köppen?
• What are Köppen’s five main climate types?

The notion that the biosphere exerts important controls on the atmosphere and other parts of the Earth system has increasingly gained acceptance among earth and ecosystem scientists. While this concept has its origins in the work of American oceanographer Alfred C. Redfield in the mid-1950s, it was English scientist and inventor James Lovelock that gave it its modern currency in the late 1970s. Lovelock initially proposed that the biospheric transformations of the atmosphere support the biosphere in an adaptive way through a sort of “genetic group selection .” This idea generated extensive criticism and spawned a steady stream of new research that has enriched the debate and advanced both ecology and environmental science . Lovelock called his idea the “ Gaia Hypothesis ” and defined Gaia as

a complex entity involving Earth’s biosphere, atmosphere, oceans, and soil ; the totality constituting a feedback of cybernetic systems which seeks an optimal physical and chemical environment for life on this planet .

The Greek word Gaia, or Gaea, meaning “Mother Earth,” is Lovelock’s name for Earth, which is envisioned as a “superorganism” engaged in planetary biogeophysiology. The goal of this superorganism is to produce a homeostatic , or balanced, Earth system. The scientific process of research and debate will eventually resolve the issue of the reality of the “Gaian homeostatic superorganism,” and Lovelock has since revised his hypothesis to exclude goal-driven genetic group selection . Nevertheless, it is now an operative norm in contemporary science that the biosphere and the atmosphere interact in such a way that an understanding of one requires an understanding of the other. Furthermore, the reality of two-way interactions between climate and life is well recognized.

Life on Earth began at least as early as 3.5 billion years ago during the middle of the Archean Eon (about 4 billion to 2.5 billion years ago). It was during this interval that life first began to exercise certain controls on the atmosphere. The atmosphere’s prebiological state is often characterized as being rich in water vapour and carbon dioxide. Though some nitrogen was also present, little if any oxygen was available. Chemical reactions with hydrogen sulfide , hydrogen , and reduced compounds of nitrogen and sulfur precluded any but the shortest lifetime for free oxygen in the atmosphere. As a result, life evolved in an atmosphere that was reducing (high hydrogen content) rather than oxidizing (high oxygen content). In addition to their chemically reducing character, the predominant gases of this prebiotic atmosphere, with the exception of nitrogen, were largely transparent to incoming sunlight but opaque to outgoing terrestrial infrared radiation . As a result, these gases are called, perhaps improperly, greenhouse gases ( see greenhouse effect ) because they are able to slow the release of outgoing radiation back into space .

In the Archean Eon, the Sun produced as much as 25 percent less light than it does today; however, Earth’s temperature was much like that of today. This is possible because the greenhouse gas -rich Archean atmosphere was effective in retarding the loss of terrestrial radiation to space. The resulting long residence time of energy within the Earth-atmosphere system resulted in a warmer atmosphere than would have been possible otherwise. The average temperature of Earth’s surface in the early Archean Eon was warmer than the modern global average. It was, according to some sources, probably similar to temperatures found in today’s tropics. Depending on the amount of nitrogen present during the Archean Eon, it has been suggested that the atmosphere may have held more than 1,000 times as much carbon dioxide than it does today.

Archean organisms included photosynthetic and chemosynthetic bacteria , methane -producing bacteria, and a more primitive group of organisms now called the “ Archaea ” (a group of prokaryotes more related to eukaryotes than to bacteria and found in extreme environments). Through their metabolic processes, organisms of the Archean Eon slowly changed the atmosphere. Hydrogen rose from trace amounts to about 1 part per million (ppm) of dry air . Methane concentrations increased from near zero to about 100 ppm. Oxygen increased from near zero to 1 ppm, whereas nitrogen concentrations rose to encompass 99 percent of all atmospheric molecules excluding water vapour. Carbon dioxide concentrations decreased to only 0.3 percent of the total; however, this was nearly 10 times the current concentration. The composition of the atmosphere, its radiation budget, its thermodynamics , and its fluid dynamics were transformed by life from the Archean Eon.

American geochemist Robert Garrels calculated that, in the absence of life and given the burial rate of carbon in rocks , oxygen would be unavailable to form water, and free hydrogen would be lost to space. Without the presence of life and compounded by this loss of hydrogen, there would be no oceans , and Earth would have become merely a dusty planet by the middle of the Archean Eon. By the end of the Archean Eon 2.5 billion years ago, both the pigment chlorophyll and photosynthetic organisms had evolved such that the production of oxygen increased rapidly. The atmosphere became transformed from a reducing atmosphere with carbon dioxide, limited oxygen, and anaerobic organisms (that is, life-forms that do not require oxygen for respiration) in control to one with an oxidizing atmosphere that was rich in oxygen , poor in carbon dioxide, and dominated by aerobic organisms (that is, life-forms requiring oxygen for respiration).

With the decline in carbon dioxide and a rise in oxygen, the greenhouse warming capacity of Earth’s atmosphere was sharply reduced; however, this happened over a period of time when the energy produced by the Sun increased systematically. These compensating changes resulted in a relatively constant planetary temperature over much of Earth’s history .

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21.5: Gaia Hypothesis and Daisyworld

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• Roland Stull
• University of British Columbia

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James Lovelock proposed a thought-provoking hypothesis: life regulates the climate to create an environment that favors life. Such self-maintained stability is called homeostasis . His hypothesis is called gaia — Greek for “mother Earth”.

Lovelock and Andrew Watson illustrate the “biological homeostasis of the global environment” with daisyworld , a hypothetical Earth containing only light and dark colored daisies. If the Earth is too cold, the dark daisies proliferate, increasing the absorption of solar radiation. If too warm, light-colored daisies proliferate, reflecting more sunlight by increasing the global albedo (Fig. 21.22).

21.5.1. Physical Approximations

We modify Lovelock’s toy model here to enable an easy solution of daisyworld on a spreadsheet. Given are two constants: the Stefan-Boltzmann constant σ SB = 5.67x10 –8 W·m –2 ·K –4 and solar irradiance S o = 1361 W·m –2 . Small variations in solar output are parameterized by luminosity, L , where L = 1 corresponds to the actual value for Earth. These factors are combined into a solar-forcing ratio, q:

\begin{align}q=\frac{L \cdot S_{o}}{4 \cdot \sigma_{S B}}\tag{21.40}\end{align}

The model forecasts the fraction of the globe covered by light daisies (C L ) and the fraction covered by dark daisies (C D ). Some locations will have no daisies, so the bare-ground fraction (C G ) of Earth’s surface is thus:

\begin{align}C_{G}=1-C_{D}-C_{L}\tag{21.41}\end{align}

To start the calculation, assume an initial state of C L = C D = 0.

Define a planetary albedo (A) as the coverage-weighted average of the individual daisy albedoes (A i , which are adjustable parameters):

\begin{align}A=C_{G} \cdot A_{G}+C_{D} \cdot A_{D}+C_{L} \cdot A_{L}\tag{21.42}\end{align}

For this example, let:

A L = 0.75 is the albedo of light-colored daisies

A D = 0.25 is the albedo of dark-colored daisies

A G = 0.5 is the bare-ground albedo (no flowers).

Use the planetary albedo with the solar forcing ratio to find daisyworld’s effective-radiation absolute temperature:

\begin{align}T_{e}^{4}=q \cdot(1-A)\tag{21.43}\end{align}

For a one-layer atmosphere with no window, the average surface temperature is

\begin{align}T_{s}^{4}=2 \cdot T_{e}^{4}\tag{21.44}\end{align}

Let Tr = 0.6 be an efficiency for horizontal heat transport. For example, Tr = 1 implies efficient spreading of heat around the globe, causing the local temperature to be controlled by the global-average albedo. Conversely, Tr = 0 forces the local temperature to be a function of only the local albedo in any one patch of daisies.

Thus, the patches of dark and light daisies have the following temperatures:

\begin{align}T_{D}^{4}=(1-T r) \cdot q \cdot\left(A-A_{D}\right)+T_{s}^{4}\tag{21.45a}\end{align}

\begin{align}T_{L}^{4}=(1-T r) \cdot q \cdot\left(A-A_{L}\right)+T_{s}^{4}\tag{21.45b}\end{align}

Suppose that daisies grow only if their patch temperatures are between 5°C and 40°C, and that daisies have the fastest growth rate (β) near the middle of this range (where T o = 295.5 K = 22.5°C):

\begin{align}\beta_{D}=1-b \cdot\left(T_{o}-T_{D}\right)^{2}\tag{21.46a}\end{align}

\begin{align}\beta_{L}=1-b \cdot\left(T_{o}-T_{L}\right)^{2}\tag{21.46b}\end{align}

where negative values of β are truncated to zero. The growth factor is b = 0.003265 K –2 .

Because dark and light daisies interact via their change on the global surface temperature, you must iterate the coverage equations together as you step forward in time

\begin{align}C_{D \text { new }}=C_{D}+\Delta t \cdot C_{D} \cdot\left(C_{G} \cdot \beta_{D}-D\right)\tag{21.47a}\end{align}

\begin{align}C_{L \text { new }}=C_{L}+\Delta t \cdot C_{L} \cdot\left(C_{G} \cdot \beta_{L}-D\right)\tag{21.47b}\end{align}

where D = 0.3 is death rate (another adjustable parameter) for both light and dark daisies. In this iteration, the daisy coverages (C D & C L ) at any one time step can be inserted into the right side of the above two equations, and the solution can be stepped forward in time to find the new coverages (C D new & C L new ) one time step ∆t later. The time units are arbitrary, so you could use ∆t = 1 or ∆t = 0.5. To get daisies to grow if none are on the planet initially, assume a seed coverage of C s = 0.01 and force C L new ≥ C s and C D new ≥ C s .

With the new coverages, eqs. (21.41 - 21.47) can be computed again for the next time step. Repeat for many time steps. For certain values of the parameters, the solution (i.e., coverages and temperatures) approaches a steady-state, which results in the desired homeostasis equilibrium.

21.5.2. Steady-state and Homeostasis

Suppose L = 1.2 with all other parameters set as described in the Physical Approximations subsection. After iterating, the final steady-state values are C L = 0.24 , C D = 0.40 and T s = 296.8 K (see Fig. 21.23). Compare this to the surface temperature of a planet with no daisies: T s barren = 291.3 K, found by setting A = A G in eqs. (21.43 - 21.44).

Suppose you rerun daisyworld with all the same parameters, but with different luminosity. The resulting steady-state conditions are shown in Fig. 21.24 for a variety of luminosities. For luminosities between about 0.94 to 1.70, the daisy coverage is able to adjust so as to maintain a somewhat constant Ts — namely, it achieves homeostasis. Weak incoming solar radiation (insolation) allows dark daisies to proliferate, which convert most of the insolation into heat. Strong insolation is compensated by increases in light daisies, which reflect the excess energy.

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The Gaia hypothesis (/ˈɡaɪ.ə/), also known as the Gaia theory, Gaia paradigm, or the Gaia principle, proposes that living organisms interact with their inorganic surroundings on Earth to form a synergistic and self-regulating, complex system that helps to maintain and perpetuate the conditions for life on the planet. The hypothesis was formulated by the chemist James Lovelock and co-developed by the microbiologist Lynn Margulis in the 1970s. Lovelock named the idea after Gaia, the primordial goddess who personified the Earth in Greek mythology. The suggestion that the theory should be called "the Gaia hypothesis" came from Lovelock's neighbour, William Golding. In 2006, the Geological Society of London awarded Lovelock the Wollaston Medal in part for his work on the Gaia hypothesis. Topics related to the hypothesis include how the biosphere and the evolution of organisms affect the stability of global temperature, salinity of seawater, atmospheric oxygen levels, the maintenance of a hydrosphere of liquid water and other environmental variables that affect the habitability of Earth. The Gaia hypothesis was initially criticized for being teleological and against the principles of natural selection, but later refinements aligned the Gaia hypothesis with ideas from fields such as Earth system science, biogeochemistry and systems ecology. Even so, the Gaia hypothesis continues to attract criticism, and today many scientists consider it to be only weakly supported by, or at odds with, the available evidence.

1. Overview

Gaian hypotheses suggest that organisms co-evolve with their environment: that is, they "influence their abiotic environment, and that environment in turn influences the biota by Darwinian process". Lovelock (1995) gave evidence of this in his second book, Ages of Gaia , showing the evolution from the world of the early thermo-acido-philic and methanogenic bacteria towards the oxygen-enriched atmosphere today that supports more complex life.

A reduced version of the hypothesis has been called "influential Gaia" [ 1 ] in "Directed Evolution of the Biosphere: Biogeochemical Selection or Gaia?" by Andrei G. Lapenis, which states the biota influence certain aspects of the abiotic world, e.g. temperature and atmosphere. This is not the work of an individual but a collective of Russian scientific research that was combined into this peer reviewed publication. It states the coevolution of life and the environment through "micro-forces" [ 1 ] and biogeochemical processes. An example is how the activity of photosynthetic bacteria during Precambrian times completely modified the Earth atmosphere to turn it aerobic, and thus supports the evolution of life (in particular eukaryotic life).

Since barriers existed throughout the twentieth century between Russia and the rest of the world, it is only relatively recently that the early Russian scientists who introduced concepts overlapping the Gaia paradigm have become better known to the Western scientific community. [ 1 ] These scientists include Piotr Alekseevich Kropotkin (1842–1921) (although he spent much of his professional life outside Russia), Rafail Vasil’evich Rizpolozhensky (1862 – c. 1922), Vladimir Ivanovich Vernadsky (1863–1945), and Vladimir Alexandrovich Kostitzin (1886–1963).

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 may have counterbalancing effects on environmental change. Opponents of this view sometimes reference examples of events that 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 at the end of the Archaean and the beginning of the Proterozoic periods.

Less accepted versions of the hypothesis claim that changes in the biosphere are brought about through the coordination of living organisms and maintain those conditions through homeostasis. In some versions of Gaia philosophy, all lifeforms are considered 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 coevolving diversity of living organisms.

The Gaia paradigm was an influence on the deep ecology movement. [ 2 ]

The Gaia hypothesis posits that the Earth is a self-regulating complex system involving the biosphere, the atmosphere, the hydrospheres and the pedosphere, tightly coupled as an evolving system. The hypothesis contends that this system as a whole, called Gaia, seeks a physical and chemical environment optimal for contemporary life. [ 3 ]

Gaia evolves through a cybernetic feedback system operated unconsciously by the biota, leading to broad stabilization of the conditions of habitability in a full homeostasis. Many processes in the Earth's surface, essential for the conditions of life, depend on the interaction of living forms, especially microorganisms, with inorganic elements. These processes establish a global control system that regulates Earth's surface temperature, atmosphere composition and ocean salinity, powered by the global thermodynamic disequilibrium state of the Earth system. [ 4 ]

The existence of a planetary homeostasis influenced by living forms had been observed previously in the field of biogeochemistry, and it is being investigated also in other fields like Earth system science. The originality of the Gaia hypothesis relies on the assessment that such homeostatic balance is actively pursued with the goal of keeping the optimal conditions for life, even when terrestrial or external events menace them. [ 5 ]

2.1. Regulation of Global Surface Temperature

Since life started on Earth, the energy provided by the Sun has increased by 25% to 30%; [ 6 ] however, the surface temperature of the planet has remained within the levels of habitability, reaching quite regular low and high margins. Lovelock has also hypothesised that methanogens produced elevated levels of methane in the early atmosphere, giving a view similar to that found in petrochemical smog, similar in some respects to the atmosphere on Titan. [ 7 ] This, he suggests tended to screen out ultraviolet until the formation of the ozone screen, maintaining a degree of homeostasis. However, the Snowball Earth [ 8 ] research has suggested that "oxygen shocks" and reduced methane levels led, during the Huronian, Sturtian and Marinoan/Varanger Ice Ages, to a world that very nearly became a solid "snowball". These epochs are evidence against the ability of the pre Phanerozoic biosphere to fully self-regulate.

Processing of the greenhouse gas CO 2 , explained below, plays a critical role in the maintenance of the Earth temperature within the limits of habitability.

The CLAW hypothesis, inspired by the Gaia hypothesis, proposes a feedback loop that operates between ocean ecosystems and the Earth's climate. [ 9 ] The hypothesis specifically proposes that particular phytoplankton that produce dimethyl sulfide are responsive to variations in climate forcing, and that these responses lead to a negative feedback loop that acts to stabilise the temperature of the Earth's atmosphere.

Currently the increase in human population and the environmental impact of their activities, such as the multiplication of greenhouse gases may cause negative feedbacks in the environment to become positive feedback. Lovelock has stated that this could bring an extremely accelerated global warming, [ 10 ] but he has since stated the effects will likely occur more slowly. [ 11 ]

Daisyworld simulations

In response to the criticism that the Gaia hypothesis seemingly required unrealistic group selection and cooperation between organisms, James Lovelock and Andrew Watson developed a mathematical model, Daisyworld, in which ecological competition underpinned planetary temperature regulation. [ 12 ]

Daisyworld examines the energy budget of a planet populated by two different types of plants, black daisies and white daisies, which are assumed to occupy a significant portion of the surface. The colour of the daisies influences the albedo of the planet such that black daisies absorb more light and warm the planet, while white daisies reflect more light and cool the planet. The black daisies are assumed to grow and reproduce best at a lower temperature, while the white daisies are assumed to thrive best at a higher temperature. As the temperature rises closer to the value the white daisies like, the white daisies outreproduce the black daisies, leading to a larger percentage of white surface, and more sunlight is reflected, reducing the heat input and eventually cooling the planet. Conversely, as the temperature falls, the black daisies outreproduce the white daisies, absorbing more sunlight and warming the planet. The temperature will thus converge to the value at which the reproductive rates of the plants are equal.

Lovelock and Watson showed that, over a limited range of conditions, this negative feedback due to competition can stabilize the planet's temperature at a value which supports life, if the energy output of the Sun changes, while a planet without life would show wide temperature changes. The percentage of white and black daisies will continually change to keep the temperature at the value at which the plants' reproductive rates are equal, allowing both life forms to thrive.

It has been suggested that the results were predictable because Lovelock and Watson selected examples that produced the responses they desired. [ 13 ]

2.2. Regulation of Oceanic Salinity

Ocean salinity has been constant at about 3.5% for a very long time. [ 14 ] Salinity stability in oceanic environments is important as most cells require a rather constant salinity and do not generally tolerate values above 5%. The constant ocean salinity was a long-standing mystery, because no process counterbalancing the salt influx from rivers was known. Recently it was suggested [ 15 ] that salinity may also be strongly influenced by seawater circulation through hot basaltic rocks, and emerging as hot water vents on mid-ocean ridges. However, the composition of seawater is far from equilibrium, and it is difficult to explain this fact without the influence of organic processes. One suggested explanation lies in the formation of salt plains throughout Earth's history. It is hypothesized that these are created by bacterial colonies that fix ions and heavy metals during their life processes. [ 14 ]

In the biogeochemical processes of Earth, sources and sinks are the movement of elements. The composition of salt ions within our oceans and seas is: sodium (Na + ), chlorine (Cl − ), sulfate (SO 4 2− ), magnesium (Mg 2+ ), calcium (Ca 2+ ) and potassium (K + ). The elements that comprise salinity do not readily change and are a conservative property of seawater. [ 14 ] There are many mechanisms that change salinity from a particulate form to a dissolved form and back. Considering the metallic composition of iron sources across a multifaceted grid of thermomagnetic design, not only would the movement of elements hypothetically help restructure the movement of ions, electrons, and the like, but would also potentially and inexplicably assist in balancing the magnetic bodies of the Earth's geomagnetic field. The known sources of sodium i.e. salts are when weathering, erosion, and dissolution of rocks are transported into rivers and deposited into the oceans.

The Mediterranean Sea as being Gaia's kidney is found (here) by Kenneth J. Hsue, a correspondence author in 2001. Hsue suggests the "desiccation" of the Mediterranean is evidence of a functioning Gaia "kidney". In this and earlier suggested cases, it is plate movements and physics, not biology, which performs the regulation. Earlier "kidney functions" were performed during the "deposition of the Cretaceous (South Atlantic), Jurassic (Gulf of Mexico), Permo-Triassic (Europe), Devonian ( Canada ), and Cambrian/Precambrian (Gondwana) saline giants." [ 16 ]

2.3. Regulation of Oxygen in the Atmosphere

The Gaia theorem states that the Earth's atmospheric composition is kept at a dynamically steady state by the presence of life. [ 17 ] The atmospheric composition provides the conditions that contemporary life has adapted to. All the atmospheric gases other than noble gases present in the atmosphere are either made by organisms or processed by them.

The stability of the atmosphere in Earth is not a consequence of chemical equilibrium. Oxygen is a reactive compound, and should eventually combine with gases and minerals of the Earth's atmosphere and crust. Oxygen only began to persist in the atmosphere in small quantities about 50 million years before the start of the Great Oxygenation Event. [ 18 ] Since the start of the Cambrian period, atmospheric oxygen concentrations have fluctuated between 15% and 35% of atmospheric volume. Cite error: Closing </ref> missing for <ref> tag Carbon precipitation, solution and fixation 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 is used by living organisms to manufacture carbonaceous tests and shells. Once dead, the living organisms' shells fall. Some arrive at the bottom of the oceans where plate tectonics and heat and/or pressure eventually convert them to deposits of chalk and limestone. Much of the falling dead shells, however, re-dissolve into the ocean below the carbon compensation depth.

One of these organisms is Emiliania huxleyi , an abundant coccolithophore algae which may have a role in the formation of clouds. [ 19 ] CO 2 excess is compensated by an increase of coccolithophorid life, increasing the amount of CO 2 locked in the ocean floor. Coccolithophorids, if the CLAW Hypothesis turns out to be supported (see "Regulation of Global Surface Temperature" above), could help increase the cloud cover, hence control the surface temperature, help cool the whole planet and favor precipitation necessary for terrestrial plants. Lately the atmospheric CO 2 concentration has increased and there is some evidence that concentrations of ocean algal blooms are also increasing. [ 20 ]

Lichen and other organisms accelerate the weathering of rocks in the surface, while the decomposition of rocks also happens faster in the soil, thanks to the activity of roots, fungi, bacteria and subterranean animals. The flow of carbon dioxide from the atmosphere to the soil is therefore regulated with the help of living beings. When CO 2 levels rise in the atmosphere the temperature increases and plants grow. This growth brings higher consumption of CO 2 by the plants, who process it into the soil, removing it from the atmosphere.

3.1. Precedents

The idea of the Earth as an integrated whole, a living being, has a long tradition. The mythical Gaia was the primal Greek goddess personifying the Earth, the Greek version of "Mother Nature" (from Ge = Earth, and Aia = PIE grandmother), or the Earth Mother. James Lovelock gave this name to his hypothesis after a suggestion from the novelist William Golding, who was living in the same village as Lovelock at the time (Bowerchalke, Wiltshire, UK). Golding's advice was based on Gea, an alternative spelling for the name of the Greek goddess, which is used as prefix in geology, geophysics and geochemistry. [ 21 ] Golding later made reference to Gaia in his Nobel prize acceptance speech.

In the eighteenth century, as geology consolidated as a modern science, James Hutton maintained that geological and biological processes are interlinked. [ 22 ] Later, the naturalist and explorer Alexander von Humboldt recognized the coevolution of living organisms, climate, and Earth's crust. [ 22 ] In the twentieth century, Vladimir Vernadsky formulated a theory of Earth's development that is now one of the foundations of ecology. Vernadsky was a Ukrainian geochemist and was one of the first scientists to recognize that the oxygen, nitrogen, and carbon dioxide in the Earth's atmosphere result from biological processes. During the 1920s he published works arguing that living organisms could reshape the planet as surely as any physical force. Vernadsky was a pioneer of the scientific bases for the environmental sciences. [ 23 ] His visionary pronouncements were not widely accepted in the West, and some decades later the Gaia hypothesis received the same type of initial resistance from the scientific community.

Also in the turn to the 20th century Aldo Leopold, pioneer in the development of modern environmental ethics and in the movement for wilderness conservation, suggested a living Earth in his biocentric or holistic ethics regarding land.

Another influence for the Gaia hypothesis and the environmental movement in general came as a side effect of the Space Race between the Soviet Union and the United States of America. During the 1960s, the first humans in space could see how the Earth looked as a whole. The photograph Earthrise taken by astronaut William Anders in 1968 during the Apollo 8 mission became, through the Overview Effect an early symbol for the global ecology movement. [ 24 ]

3.2. Formulation of the Hypothesis

Lovelock started defining the idea of a self-regulating Earth controlled by the community of living organisms in September 1965, while working at the Jet Propulsion Laboratory in California on methods of detecting life on Mars. [ 25 ] [ 26 ] The first paper to mention it was Planetary Atmospheres: Compositional and other Changes Associated with the Presence of Life , co-authored with C.E. Giffin. [ 27 ] A main concept was that life could be detected in a planetary scale by the chemical composition of the atmosphere. According to the data gathered by the Pic du Midi observatory, planets like Mars or Venus had atmospheres in chemical equilibrium. This difference with the Earth atmosphere was considered to be a proof that there was no life in these planets.

Lovelock formulated the Gaia Hypothesis in journal articles in 1972 [ 28 ] and 1974, [ 29 ] followed by a popularizing 1979 book Gaia: A new look at life on Earth . An article in the New Scientist of February 6, 1975, [ 30 ] and a popular book length version of the hypothesis, published in 1979 as The Quest for Gaia , began to attract scientific and critical attention.

Lovelock called it first the Earth feedback hypothesis, [ 31 ] and it was 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 detecting such combinations in other planets' atmospheres as a relatively reliable and cheap way to detect life.

Later, other relationships such as sea creatures producing sulfur and iodine in approximately the same quantities as required by land creatures emerged and helped bolster the hypothesis. [ 32 ]

In 1971 microbiologist Dr. Lynn Margulis joined Lovelock in the effort of fleshing out the initial hypothesis into scientifically proven concepts, contributing her knowledge about how microbes affect the atmosphere and the different layers in the surface of the planet. [ 33 ] The American biologist had also awakened criticism from the scientific community with her advocacy of the theory on the origin of eukaryotic organelles and her contributions to the endosymbiotic theory, nowadays accepted. Margulis dedicated the last of eight chapters in her book, The Symbiotic Planet , to Gaia. However, she objected to the widespread personification of Gaia and stressed that Gaia is "not an organism", but "an emergent property of interaction among organisms". She defined Gaia as "the series of interacting ecosystems that compose a single huge ecosystem at the Earth's surface. Period". The book's most memorable "slogan" was actually quipped by a student of Margulis'.

James Lovelock called his first proposal the Gaia hypothesis but has also used the term Gaia theory . Lovelock states that the initial formulation was based on observation, but still lacked a scientific explanation. The Gaia hypothesis has since been supported by a number of scientific experiments [ 34 ] and provided a number of useful predictions. [ 35 ]

3.3. First Gaia Conference

In 1985, the first public symposium on the Gaia hypothesis, Is The Earth A Living Organism? was held at University of Massachusetts Amherst, August 1–6. [ 36 ] The principal sponsor was the National Audubon Society. Speakers included James Lovelock, George Wald, Mary Catherine Bateson, Lewis Thomas, John Todd, Donald Michael, Christopher Bird, Thomas Berry, David Abram, Michael Cohen, and William Fields. Some 500 people attended. [ 37 ]

3.4. Second Gaia Conference

In 1988, climatologist Stephen Schneider organised a conference of the American Geophysical Union. The first Chapman Conference on Gaia, [ 38 ] was held in San Diego, California on March 7, 1988.

During the "philosophical foundations" session of the conference, David Abram spoke on the influence of metaphor in science, and of the Gaia hypothesis as offering a new and potentially game-changing metaphorics, while James Kirchner criticised the Gaia hypothesis for its imprecision. Kirchner claimed that Lovelock and Margulis had not presented one Gaia hypothesis, but four:

• 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.
• Geophysical Gaia: that the Gaia hypothesis 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, to enable the flourishing of all life. Strong Gaia, Kirchner claimed, was untestable and therefore not scientific. [ 39 ]

Lovelock and other Gaia-supporting scientists, however, did attempt to disprove the claim that the hypothesis 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. [ 12 ] Lovelock said that the Daisyworld model "demonstrates that self-regulation of the global environment can emerge from competition amongst types of life altering their local environment in different ways". [ 40 ]

Lovelock was careful to present a version of the Gaia hypothesis that 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 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. Most accusations of teleologism ceased, following this conference.

3.5. Third Gaia Conference

By the time of the 2nd Chapman Conference on the Gaia Hypothesis, held at Valencia, Spain, on 23 June 2000, [ 41 ] the situation had changed significantly. Rather than a discussion of the Gaian teleological views, or "types" of Gaia hypotheses, 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: [ 42 ]

• "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 collaborated with using process models or global models of the climate system that include the biota and allow for chemical cycling?"

In 1997, Tyler Volk argued that a Gaian system is almost inevitably produced as a result of an evolution towards far-from-equilibrium homeostatic states that maximise entropy production, and Kleidon (2004) agreed stating: "...homeostatic behavior can emerge from a state of MEP associated with the planetary albedo"; "...the resulting behavior of a symbiotic 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. 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 and vibration-based beings and organisms. The resulting co-evolving dynamical process eventually leads to the convergence of equilibrium and optimal conditions", but would also require progress of truth and understanding in a lens that could be argued was put on hiatus while the species was proliferating the needs of Economic manipulation and environmental degradation while losing sight of the maturing nature of the needs of many. (12:22 10.29.2020)

3.6. Fourth Gaia Conference

A fourth international conference on the Gaia hypothesis, sponsored by the Northern Virginia Regional Park Authority and others, was held in October 2006 at the Arlington, VA campus of George Mason University. [ 43 ]

Martin Ogle, Chief Naturalist, for NVRPA, and long-time Gaia hypothesis proponent, organized the event. Lynn Margulis, Distinguished University Professor in the Department of Geosciences, University of Massachusetts-Amherst, and long-time advocate of the Gaia hypothesis, 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.

4. Criticism

After initially receiving little attention from scientists (from 1969 until 1977), thereafter for a period the initial Gaia hypothesis was criticized by a number of scientists, including Ford Doolittle, [ 44 ] Richard Dawkins [ 45 ] and Stephen Jay Gould. [ 38 ] Lovelock has said that because his hypothesis is named after a Greek goddess, and championed by many non-scientists, [ 31 ] the Gaia hypothesis was interpreted as a neo-Pagan religion. Many scientists in particular also criticized the approach taken in his popular book Gaia, a New Look at Life on Earth for being teleological—a belief that things are purposeful and aimed towards a goal. Responding to this critique in 1990, Lovelock stated, "Nowhere in our writings do we express the idea that planetary self-regulation is purposeful, or involves foresight or planning by the biota".

Stephen Jay Gould criticized Gaia as being "a metaphor, not a mechanism." [ 46 ] He wanted to know the actual mechanisms by which self-regulating homeostasis was achieved. In his defense of Gaia, David Abram argues that Gould overlooked the fact that "mechanism", itself, is a metaphor — albeit an exceedingly common and often unrecognized metaphor — one which leads us to consider natural and living systems as though they were machines organized and built from outside (rather than as autopoietic or self-organizing phenomena). Mechanical metaphors, according to Abram, lead us to overlook the active or agent quality of living entities, while the organismic metaphors of the Gaia hypothesis accentuate the active agency of both the biota and the biosphere as a whole. [ 47 ] [ 48 ] With regard to causality in Gaia, Lovelock argues that no single 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 hypothesis for other reasons. [ 49 ]

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 also states that most of his critics are biologists but that his hypothesis includes experiments in fields outside biology, and that some self-regulating phenomena may not be mathematically explainable. [ 49 ]

4.1. Natural Selection and Evolution

Lovelock has suggested that global biological feedback mechanisms could evolve by natural selection, stating that organisms that improve their environment for their survival do better than those that damage their environment. However, in the early 1980s, W. Ford Doolittle and Richard Dawkins separately argued against this aspect of Gaia. Doolittle argued that nothing in the genome of individual organisms could provide the feedback mechanisms proposed by Lovelock, and therefore the Gaia hypothesis proposed no plausible mechanism and was unscientific. [ 44 ] Dawkins meanwhile stated that for organisms to act in concert would require foresight and planning, which is contrary to the current scientific understanding of evolution. [ 45 ] Like Doolittle, he also rejected the possibility that feedback loops could stabilize the system.

Lynn Margulis, a microbiologist who collaborated with Lovelock in supporting the Gaia hypothesis, argued in 1999 that "Darwin's grand vision was not wrong, only incomplete. In accentuating the direct competition between individuals for resources as the primary selection mechanism, Darwin (and especially his followers) created the impression that the environment was simply a static arena". She wrote that the composition of the Earth's atmosphere, hydrosphere, and lithosphere are regulated around "set points" as in homeostasis, but those set points change with time. [ 50 ]

Evolutionary biologist W. D. Hamilton called the concept of Gaia Copernican, adding that it would take another Newton to explain how Gaian self-regulation takes place through Darwinian natural selection. [ 21 ] More recently Ford Doolittle building on his and Inkpen's ITSNTS (It's The Song Not The Singer) proposal [ 51 ] proposed that differential persistence can play a similar role to differential reproduction in evolution by natural selections, thereby providing a possible reconciliation between the theory of natural selection and the Gaia hypothesis. [ 52 ]

4.2. Criticism in the 21st Century

The Gaia hypothesis continues to be broadly skeptically received by the scientific community. For instance, arguments both for and against it were laid out in the journal Climatic Change in 2002 and 2003. A significant argument raised against it are the many examples where life has had a detrimental or destabilising effect on the environment rather than acting to regulate it. [ 53 ] [ 54 ] Several recent books have criticised the Gaia hypothesis, expressing views ranging from "... the Gaia hypothesis lacks unambiguous observational support and has significant theoretical difficulties" [ 55 ] to "Suspended uncomfortably between tainted metaphor, fact, and false science, I prefer to leave Gaia firmly in the background" [ 56 ] to "The Gaia hypothesis is supported neither by evolutionary theory nor by the empirical evidence of the geological record". [ 57 ] The CLAW hypothesis, [ 9 ] initially suggested as a potential example of direct Gaian feedback, has subsequently been found to be less credible as understanding of cloud condensation nuclei has improved. [ 58 ] In 2009 the Medea hypothesis was proposed: that life has highly detrimental (biocidal) impacts on planetary conditions, in direct opposition to the Gaia hypothesis. [ 59 ]

In a 2013 book-length evaluation of the Gaia hypothesis considering modern evidence from across the various relevant disciplines, Toby Tyrrell concluded that: "I believe Gaia is a dead end*. Its study has, however, generated many new and thought provoking questions. While rejecting Gaia, we can at the same time appreciate Lovelock's originality and breadth of vision, and recognize that his audacious concept has helped to stimulate many new ideas about the Earth, and to champion a holistic approach to studying it". [ 60 ] Elsewhere he presents his conclusion "The Gaia hypothesis is not an accurate picture of how our world works". [ 61 ] This statement needs to be understood as referring to the "strong" and "moderate" forms of Gaia—that the biota obeys a principle that works to make Earth optimal (strength 5) or favourable for life (strength 4) or that it works as a homeostatic mechanism (strength 3). The latter is the "weakest" form of Gaia that Lovelock has advocated. Tyrrell rejects it. However, he finds that the two weaker forms of Gaia—Coeveolutionary Gaia and Influential Gaia, which assert that there are close links between the evolution of life and the environment and that biology affects the physical and chemical environment—are both credible, but that it is not useful to use the term "Gaia" in this sense and that those two forms were already accepted and explained by the processes of natural selection and adaptation. [ 62 ]

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The Gaia Hypothesis: Is the Earth Alive?

More than one astronaut looking back at our planet has been awed into concluding that this blue and green globe is, in fact, a living being. Of course, many native peoples the world over have always believed (and functioned on the premise) that the earth is alive.

And now contemporary scientists are talking more and more about the Gaia hypothesis: the proposition that, in some ways, the planet does behave like a living system. (Gaia pronounced “Guy-uh” — was the Greek goddess of the earth.)

“What’s that?” you say. “Scientists are saying the earth is alive?” Well, the honest answer to that is “No, but  . . .” And the “but” becomes quite fascinating.

British scientist James Lovelock, the person most responsible for the Gaia hypothesis, was working for NASA when he first reached his living system insight questioning is the earth alive? Surprisingly, though, at the time he was creating tests to detect life on Mars!

Lovelock had taken the approach that, rather than have satellites take minute soil tests on the red planet (using what he described as “glorified flea detectors”), scientists should look at Mars’ atmosphere to see if it has any concentrations of gases that could exist only if they were maintained by living organisms. To test that idea, Lovelock looked at the atmosphere of our own planet. Sure enough, earth’s air contains large quantities of highly reactive gases — such as oxygen and methane — that naturally break down into other compounds. “If chemical thermodynamics alone mattered,” he wrote, “almost all the oxygen and most of the nitrogen in the atmosphere ought to have ended up in the sea combined as nitrate ion.”

This simple discovery later developed into one of Lovelock’s original arguments for Gaia: Something is maintaining numerous reactive gases in our atmosphere in an equilibrium steady state. (Mars, by the way, flunked the “active atmosphere” test.)

The second, and even more compelling, argument was that over the millenia the earth has somehow regulated its own temperature. When life began on our planet four billion years ago, the sun was 30% cooler than it is today. Yet, from then until now, the temperature of the earth’s surface has remained within the critical life-supporting range of 15 degrees to 30 degrees Celsiu. The level of CO, has dropped a hundred fold in those four billion years, reducing the “greenhouse” heat-holding effect of the atmosphere even while the sun was radiating more heat. The result? The earth has kept itself at a constant temperature . . . just as our own bodies do!

Temperature and a reactive atmosphere are just two of the factors kept in balance by the earth. One must also notice that if — as Lovelock states — “humidity or salinity or acidity or any one of a number of other variables had strayed outside a narrow range of values for any length of time, life would have been annihilated.”

The interactive mechanisms that accomplish this self — regulation are too complex for current science to quantify, so Lovelock often uses a simplified model of an imaginary “Daisy World” to suggest how the system might work. Suppose there was a planet that supported only two plant species, white daisies and black daisies. Since the white ones reflect more heat than black ones, they would fare better when the planet was unusually hot. The reverse would also be true: Black daisies, being better heat absorbers, could survive better during cool periods.

But what would happen if Daisy World was cool for an extended time? Black daisies would take over more and more of the land surface, increasing the absorption capacity of the planet and thereby warming it up. In time, the temperature would rise to the best range for white daisies. Those would spread, and the black ones would largely die back. But that event would increase the heat reflectiveness of the planet, thus eventually cooling its surface.

By such means, the black and white daisies would balance each other and keep the planet’s temperature from ever getting too hot or too cold to support plant life. On a much more complex level, the organisms on our own planet must work together to stabilize the earth.

In sum (again quoting Lovelock), “The Gaia hypothesis sees the earth as a self-regulating system able to maintain the climate, the atmosphere, the soil, and the ocean composition at a fixed state that’s favorable for life. It’s often taken that the capacity for self regulation in the face of perturbation, change, disasters, and so on is a very strong characteristic of living things and, in that sense, the earth is a living thing.”

But Really, is the Earth Alive?

Lovelock is saying that the evolution of life and the evolution of the planet have not been separate phenomena but one single, tightly coupled process. Life does not simply adapt to its environment but, through various feedback loops, coevolves with it. This unifying, whole systems view is beginning to gain ground with scientists. And the fascinating search for Gaia’s mechanisms is already leading to new areas of exploration. Biologist Lynn Margulis, who worked closely with Lovelock on the original hypothesis, now studies the roles that hardy microorganisms may play in regulating the atmosphere. She’s found 200 or so mostly dormant microorganisms in tiny culture samples, each ready under the right conditions — to perform its function and give off its particular gaseous emission, depending on surrounding conditions. Atmospheric scientist Pat Zimmerman examined the intestinal bacteria of termites as a source of atmospheric methane and learned that since there are about 1,500 pounds of termites per human being on earth, and since the wood nibblers go through the equivalent of one-third of the new plant carbon created every year, they may produce half of the methane in the atmosphere!

But Lovelock’s words have at times suggested that the planet’s totality of life is deliberately working to better its condition and increase itself. Adding such an aspect of purposefulness (even consciousness) to Gaia grates on most otherwise sympathetic scientists. Any hints that the whole system may indeed be alive are taboo to them — that’s talking religion. And as Stanford Research Institute senior policy analyst Don Michael puts it, “Science and spirit are different realms. They are not in conflict, but there’s no interface between the two.” Lovelock himself now seems to back away from such implications: “There’s no foresight or planning involved on the part of life in regulating the planet. It’s just a kind of automatic process.”

That hasn’t stopped many non-scientists from drawing their own conclusions about the implications of the Gaia hypothesis. Like several other environmentalists, Nancy Todd, co-founder of the New Alchemy Institute, sees Gaia as a means of helping humans be better planetary stewards. “Gaia,” she states, “is the only metaphor scientific and mythologic enough to see us through our present crisis and lead to a resacralization of the world.”

Indigenous peoples who have always felt themselves in communication with a living planet feel that interest in Gaia is a sign that technological cultures are beginning to agree with them. Prem Das, a shaman — healer in Tepic, Mexico, tells outsiders that of course the planet is alive: “The Earth is speaking all the time. But it doesn’t speak English. It speaks Earthese. We just need to learn how to listen.”

Psychologist Jim Swan-producer of a national symposium called “Is the Earth a Living Organism?” — feels the Gaia hypothesis may herald a paradigmatic shift that would affect almost all areas of thought and be greatly beneficial to society. He says, “You can’t prove earth is alive scientifically, because living is a property beyond the very limited structure of current science. But you can know it for yourself through direct experience — through vision quests in sacred places, for example. And such knowledge has incredible practical utility. Science based on it would help bind us to each other, not blow each other up. Experience of the living earth can also have great benefits for mental and physical health — especially in our society, which rejects feeling, intuitive modes of being. The experience can also change your life priorities. Almost all our country’s great environmentalists — including Burroughs, Thoreau, Carson, and Muir — have felt a oneness with the planet and had that as a motivation for their actions.”

Earthly Thoughts in the Meantime

While Gaian scientists stay clear of such thoughts, the hypothesis is beginning to motivate their actions, as well. Dr. Stephen Schneider of the National Center for Atmospheric Research points out that although Gaia’s regulatory mechanisms may help assure the long-term existence of life on the planet, they may not assure the short-term survival of our own individual species — a species that may be making the planet too hot for its own good. “And I’m a chauvinist for human beings,” he confesses.

Even Lovelock, for all his British aplomb, agrees: “The clearing of the tropical forests and the addition of carbon dioxide to the atmosphere by fossil fuel burning act both in the same way to stress a system which is already near the limit of its capacity to regulate. And the effect of this perturbation might cause us to jump to a new stable state in the very near future. I imagine if the system does flip to a different stable state, there will be a sudden and enormous change in speciation, just as there was when the dinosaurs vanished. There will be a new biota that will be fit for the new environment. But I doubt it will be very comfortable for us.”

So, if widely understood, the Gaia hypothesis could help us avoid such a catastrophe. Whether the idea is adopted as a new spiritual credo or an automatic mechanism, it may be a notion whose time has come . . . not a moment too soon.

EDITOR’S NOTE: Lovelock’s book Gaia: A New Look at Life on Earth is available for $6.95 postpaid from Oxford University Press, NJ.

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Unveiling the Practical Applications of the Gaia Hypothesis: Harnessing Earth’s Interconnected Ecosystems

Understanding the gaia hypothesis: a paradigm shift in earth science.

The Gaia hypothesis, proposed by James Lovelock in the 1970s, challenges traditional views of the Earth by presenting it as a self-regulating and interconnected system. Named after the Greek goddess Gaia, who personifies the Earth, this hypothesis suggests that the planet functions as a complex organism in which various biotic and abiotic components interact and maintain a state of equilibrium. While the Gaia hypothesis has generated considerable debate and criticism within the scientific community, it offers a unique perspective that may have practical implications for our understanding of the Earth and its ecosystems.

Insights for ecosystem management and conservation

A practical application of the Gaia hypothesis lies in its potential to guide ecosystem management and conservation efforts. By recognizing the Earth as a self-regulating entity, the hypothesis emphasizes the importance of maintaining ecological balance. It highlights the interdependence of different species and their role in maintaining the overall health of the planet. This perspective can help inform conservation strategies by emphasizing the need to protect biodiversity, conserve habitats, and promote ecological resilience.

In addition, the Gaia hypothesis can provide insights into the potential impacts of human activities on Earth’s ecosystems. Recognizing the delicate balance of the planet, it underscores the importance of minimizing anthropogenic impacts to prevent destabilization of the overall system. This understanding can guide policymakers and conservationists in making informed decisions about land use, resource management, and sustainable development practices.

Climate Change and Planetary Feedback Mechanisms

Another area where the Gaia hypothesis may have practical implications is in the context of climate change. The hypothesis suggests that the Earth possesses self-regulating mechanisms that help to maintain stable climatic conditions conducive to life. These mechanisms, often referred to as planetary feedback loops, involve complex interactions among the atmosphere, oceans, biosphere, and geosphere.

Understanding and harnessing these feedback mechanisms can help develop effective mitigation and adaptation strategies. By recognizing the Earth as an interconnected system, the Gaia hypothesis underscores the importance of considering the broader impacts of climate change interventions. It highlights the potential for unintended consequences and emphasizes the need for holistic approaches that take into account the complex dynamics of the Earth system.

Implications for technological innovation and sustainability

The Gaia hypothesis also offers insights into technological innovation and sustainability. By viewing the Earth as a self-regulating entity, it encourages us to explore nature-inspired solutions to various challenges. The hypothesis suggests that studying and emulating natural systems can lead to the development of sustainable technologies and practices.

This perspective has influenced fields such as biomimicry, where designers and engineers draw inspiration from nature to solve human problems. By observing the efficiency and resilience of natural systems, scientists can design more sustainable materials, energy systems, and infrastructure. The Gaia hypothesis encourages interdisciplinary collaboration and the application of systems thinking to address complex environmental problems.

In addition, the Gaia hypothesis can foster a sense of interconnectedness and stewardship toward the Earth. By recognizing the planet as a living organism, it encourages individuals and communities to adopt more sustainable lifestyles and practices. This shift in mindset can lead to changes in consumption patterns, waste management, and resource conservation, contributing to a more sustainable future.

While the Gaia hypothesis has generated controversy and debate, its practical implications cannot be ignored. By challenging conventional views of the Earth as a passive backdrop to life, it offers a holistic perspective that can inform ecosystem management, climate change mitigation and adaptation, technological innovation, and sustainability efforts. Embracing the interconnectedness of the planet and recognizing the delicate balance of its systems can guide us toward a more harmonious coexistence with nature. The Gaia hypothesis serves as a reminder of the complexity of the Earth and our responsibility to protect and preserve it for future generations.

Would the Gaia hypothesis have any practical use?

The Gaia hypothesis, proposed by James Lovelock, suggests that the Earth functions as a self-regulating system. While it is primarily a scientific concept, it has implications for various practical applications.

How can the Gaia hypothesis be applied to environmental conservation?

The Gaia hypothesis encourages us to view the Earth as a complex, interconnected system. By understanding the interdependencies between different components of the environment, we can develop more effective strategies for environmental conservation and management.

Can the Gaia hypothesis guide sustainable development practices?

Yes, the Gaia hypothesis can inform sustainable development practices. By recognizing the Earth as a self-regulating entity, we can strive to achieve a harmonious balance between human activities and the natural environment. This can lead to the development of sustainable practices that minimize negative impacts on the planet.

Are there any implications of the Gaia hypothesis for climate change mitigation?

Indeed, the Gaia hypothesis has implications for climate change mitigation. By understanding the Earth’s self-regulating mechanisms, we can gain insights into how human activities affect the climate system. This knowledge can guide efforts to reduce greenhouse gas emissions, adapt to changing climate conditions, and develop strategies for long-term climate resilience.

How can the Gaia hypothesis influence our approach to medicine and healthcare?

The Gaia hypothesis can influence our approach to medicine and healthcare by emphasizing the interconnectedness of living organisms and their environment. It encourages a holistic perspective that recognizes the profound impact of environmental factors on human health. This can lead to the development of new medical practices and policies that promote both individual and planetary well-being.

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Earth Science

On Gaia: A Critical Investigation of the Relationship between Life and Earth

A critical examination of James Lovelock's controversial Gaia hypothesis

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One of the enduring questions about our planet is how it has remained continuously habitable over vast stretches of geological time despite the fact that its atmosphere and climate are potentially unstable. James Lovelock’s Gaia hypothesis posits that life itself has intervened in the regulation of the planetary environment in order to keep it stable and favorable for life. First proposed in the 1970s, Lovelock’s hypothesis remains highly controversial and continues to provoke fierce debate. On Gaia undertakes the first in-depth investigation of the arguments put forward by Lovelock and others—and concludes that the evidence doesn’t stack up in support of Gaia. Toby Tyrrell draws on the latest findings in fields as diverse as climate science, oceanography, atmospheric science, geology, ecology, and evolutionary biology. He takes readers to obscure corners of the natural world, from southern Africa where ancient rocks reveal that icebergs were once present near the equator, to mimics of cleaner fish on Indonesian reefs, to blind fish deep in Mexican caves. Tyrrell weaves these and many other intriguing observations into a comprehensive analysis of the major assertions and lines of argument underpinning Gaia, and finds that it is not a credible picture of how life and Earth interact. On Gaia reflects on the scientific evidence indicating that life and environment mutually affect each other, and proposes that feedbacks on Earth do not provide robust protection against the environment becoming uninhabitable—or against poor stewardship by us.

"Tyrrell's story is very informative and the reader will learn many fascinating stories of an organism's adaptation to an environment (rather than an environment conforming to an organism's need)."—Jonathan DuHamel, Arizona Daily Independent

"A systematic, dispassionate, retrospective examination of Gaia. . . . Tyrrell makes it very clear where he stands on Gaia, but the path of his journey is well reasoned—not a diatribe."—William Schlesinger, Nature Climate Change

"It is timely to present a systematic review of how Gaia theory looks in the light of . . . new information. Not too well is Toby Tyrrell's conclusion in this clear summary of the evidence to date. . . . Persuasive."—Jon Turney, Times Higher Education

"In On Gaia: A Critical Investigation of the Relationship between Life and Earth , Dr. Toby Tyrrell, for the first time, conducts a lengthy analysis of the scientific data for and against the Gaia Hypothesis. He concludes that the Gaia Hypothesis does not have enough scientific data to support it. He write eloquently, clearly, and succinctly describing how the Gaia Hypothesis lacks sufficient scientific evidence. . . . A fair and reflective analysis."—Gabriel Thoumi, MongaBay.com

"Tyrrell examines alternative arguments about the long-term characteristics of the Earth, considering geological and coevolutionary effects. He provides a detailed examination of how and why the environment cannot be affected by natural selection and how diverse physical factors affect living things. . . . Overall, a useful examination of the changing nature of Earth and the biologic/physical factors that affect the planet's organisms."— Choice

"His theory is not as grandiose as Gaia, but it is far more compelling. The conclusion is worth reading by itself if you are pushed for time, but for those who really want a good insight into Gaia in the context of natural systems, I would recommend reading the whole book."—Gillian Gibson, Environmentalist

"If you've had your curiosity piqued by the Gaia Hypothesis before, you'll appreciate this well-organized and comprehensive assessment of it. Tyrrell doesn't have an axe to grind, and his discussion is fair and focused on the evidence. If you want to grapple with Gaia, this book is a good way to do it."—Scott K. Johnson, ArsTechnica

"One third of this well argued book consists of end notes, many of which are as readable as the main text. By questioning the arguments for and against the Gaia hypothesis, Tyrrell has done a great service to enriching the ongoing discourse on making our planet hospitable for all life forms, now and in the future."—Sudhirendar Sharma, Cover Drive

" On Gaia is a rewarding read for the knowledgeable reader. The book is an easy read and accessible to a broad audience. Unlike some science books intended for popular audiences, the book is sophisticated enough to keep the interest of graduate students."— GeoQ

"It is . . . Valuable for a variety of reasons: as a good natural history brief; as a good introduction to modern ecology (the one that considers the biota as a whole); and as a cautious reflection on what makes a theory gain or lose respectability. Therefore, it will be useful at different academic levels, from teaching at secondary school (it is an excellent starting point for serious debate) to highly specialized climate scientists."— Chemical Engineer

"A handful of scientists have become crusaders for the Gaia hypothesis, while the rest have dismissed it without a second thought. Toby Tyrrell, on the other hand, is one of the very few scientists to have considered the evidence at length and in detail. In summarizing nearly forty years of arguments for and against the Gaia hypothesis, he has done a great service for anyone who is curious about Gaia, or about this fascinating planet that we all call home."—James Kirchner, University of California, Berkeley

"Toby Tyrrell unravels the various formulations of Gaia and explains how recent scientific developments bring the hypothesis into question. His criticisms are insightful, profound, and convincing, but fair. On Gaia is wonderfully informative and a pleasure to read."—Francisco J. Ayala, author of Am I a Monkey?: Six Big Questions about Evolution

"At last, a beautifully written and clear-eyed analysis of the interplay of life and the Earth system. On Gaia provides the understanding for moving forward in the quest for sustainability, and is essential reading if our planet is to remain habitable for humanity."—Thomas E. Lovejoy, George Mason University

" On Gaia makes a wonderful addition to the literature. It is scholarly, well-written, and well-reasoned."—Simon A. Levin, Princeton University

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A Critical Investigation of the Relationship between Life and Earth

• Toby Tyrrell and Toby Tyrrell
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• Language: English
• Publisher: Princeton University Press
• Copyright year: 2013
• Edition: Course Book
• Audience: Professional and scholarly;College/higher education;
• Main content: 320
• Other: 16 halftones. 31 line illus. 12 tables.
• Keywords: Gaia hypothesis ; James Lovelock ; climate science ; oceanography ; atmospheric science ; geology ; ecology ; evolutionary biology ; global environment ; planetary regulation ; environmental control ; geological hypothesis ; geological forces ; astronomical processes ; coevolutionary hypothesis ; planetary environment ; Gaia ; natural selection ; single organisms ; eusocial colonies ; homeostatic regulations ; genetic uniformity ; genetic similarity ; environmental regulation ; extremophiles ; biosphere ; evolution ; habitat commitment ; environmental preferences ; optimal temperatures ; living organisms ; temperature ; growth ; metabolic rates ; primary production ; biomass ; biodiversity ; temperature effects ; ice ages ; interglacials ; carbon ; Cretaceous ; climatic state ; atmosphere ; chemical equilibrium ; biological processes ; oxygen ; methane ; life ; vegetation ; plant transpiration ; fossil evidence ; diatoms ; evolutionary inventions ; oxygen-yielding photosynthesis ; first forests ; oxygen-dependent photosynthesis ; anaerobes ; land plants ; stability ; Earth environment ; Earth climate ; Earth history ; icy climates ; long-term life ; life persistence ; atmospheric CO2 ; anthropic principle ; climate shifts ; evolutionary dynamics ; ecological dynamics ; evolutionary advances ; oxygenic photosynthesis ; environmental catastrophes
• Published: July 21, 2013
• ISBN: 9781400847914