Lovelock Publishes

In Gaia: A New Look at Life on Earth, James Lovelock argued that the biosphere itself is an organism that regulates its own environment.

Summary of Event

How does the planet Earth maintain a nearly stable environment? It was once common to regard Earth as uniquely suited to life, but many of the features that make the planet hospitable to life (such as the oxygen-rich atmosphere) were actually created by life. The steady state of Earth’s environment actually is a complex problem. For example, theories of stellar evolution imply that the early Sun was perhaps one-third less luminous than the present-day Sun, but Earth has had liquid water for more than three billion years. A delicate balance had to have been maintained among temperature, pressure, and atmospheric composition throughout Earth’s history to avoid either the freezing or the vaporization of the oceans. The oxygen content of the atmosphere is close to the maximum possible without fire becoming a serious hazard; if the oxygen content of the atmosphere were 25 percent rather than the actual 20 percent, even wet fuel would burn readily. In the absence of biological action, the oceans would long ago have been saturated by dissolved salts; instead, they are only about 10 percent saturated. Gaia hypothesis
Environmental awareness;Gaia hypothesis
Gaia hypothesis
Environmental awareness;Gaia hypothesis
Lovelock, James
Margulis, Lynn
Williams, George C.

Reflections on the relationship between life and the environment led atmospheric scientist James Lovelock to publish a short note in the journal Atmospheric Environment in 1972 in which he proposed that life on Earth actually regulates its own environment. He proposed the term “Gaia” for the complex of self-regulating systems on Earth; he credited writer William Golding Golding, William for suggesting the name, which is that of the ancient Greek goddess of the Earth.

The following year, Lovelock published the first of many papers he would write in concert with American microbiologist Lynn Margulis. Margulis already had one radical innovation to her credit: During the 1960’s, she proposed that intracellular bodies such as mitochondria and chloroplasts had once been free-living organisms. Mitochondria Mitochondria are energy-producing bodies in cells, and chloroplasts Chloroplasts are the green-pigmented bodies in plant cells. Both have their own deoxyribonucleic acid (DNA) and reproduce separately from their host cells. Margulis proposed that this arrangement originated when one cell ingested another but did not digest it, and the combined organisms entered a symbiotic relationship. This idea, highly controversial when first introduced, became widely accepted.

The Gaia hypothesis was little noticed outside the scientific community until 1979, when Lovelock published Gaia: A New Look at Life on Earth. The Gaia hypothesis postulates that the biosphere (all living organisms on Earth), atmosphere, soils, and oceans of Earth form a self-regulating system, which is given the collective name Gaia. Although the theory that organisms modify their environment is undisputed, the Gaia hypothesis asserts that the biosphere actively regulates its environment to create conditions optimal for life. Self-regulation, or homeostasis, is widespread among organisms and is actually one of the hallmarks of living things. In many versions of the Gaia hypothesis, the self-regulation is claimed to be so complex that Gaia itself should be regarded as a living organism. Self-regulating systems require sensors to detect change, information storage to accumulate and process sensed information, amplifiers to convert information into action capable of modifying the system, and feedback mechanisms to monitor the effect of the change on the system.

Self-regulation does not necessarily mean invulnerability. The human body maintains a stable internal temperature, but under extremes of heat and cold the self-regulatory mechanism can fail. Gaia proponents have never argued that the existence of Gaia guarantees survival of life on Earth or that the self-regulatory mechanisms cannot be overwhelmed by large enough disturbances. With the recognition of the importance of such external change agents as large meteor impacts, Lovelock later modified his original hypothesis to one of punctuated homeostasis—that is, stable conditions punctuated by occasional disturbances, followed by return to stable conditions that are not necessarily identical to those before the disturbances.

Both Gaia proponents and critics of the hypothesis are careful to distinguish the self-regulation at the core of the Gaia hypothesis from a variety of superficially similar concepts. Balance of forces is not self-regulation. Earth maintains a stable orbit around the Sun because of a balance between the planet’s momentum, which would cause it to continue in a straight line, and gravity, which would pull Earth into the Sun. Earth and the Sun do not do anything to correct disturbances of Earth’s orbit—for example, those disturbances caused by other planets.

Equilibrium is not self-regulation. If an evacuated tube is half filled with water and then sealed, water will evaporate until the pressure of the water vapor is powerful enough to prevent further evaporation. If the temperature of the cylinder is changed, water will evaporate or condense until a new equilibrium is reached. Nevertheless, this process is not self-regulation, because there is no sensory or control mechanism to detect and regulate changes in the system. Individual water molecules merely move from one phase to the other until the rate of movement in both directions is equal.

Feedback and input-output balances are also not self-regulation. A glacier may maintain a stable configuration in which melting and evaporation balance snowfall and ice flow. A change in any of these variables may cause the glacier to advance or retreat until a new stable configuration exists, but this process is not self-regulation; the glacier is simply responding passively to external influences.

All of the mechanisms noted above may be means by which a self-regulatory system maintains control, but they are not, in themselves, self-regulatory. Two simple examples, one natural, the other artificial, illustrate the differences between true self-regulation and superficially similar processes. When the human body becomes heated, it radiates more heat to its surroundings because of its higher temperature, and the body absorbs heat because of the high heat capacity of water. Both processes mitigate temperature rise, although insufficiently, but neither is self-regulatory. The body also opens blood capillaries to the skin to carry heat to the surface and begins sweating to cool by evaporation. These are genuinely self-regulatory mechanisms: They are not caused directly by heating but are initiated by the body in response to sensory inputs that indicate excessive heat buildup.

To consider an artificial example: The pressure-relief cap on a pressure cooker is not a true self-regulatory device; it simply responds to excess pressure by pushing a weight upward. As long as there is enough pressure to keep the weight suspended against the force of gravity, the valve stays open. If the valve were connected to a device that cut the heat to the cooker, and perhaps compensated for water lost by evaporation, then the device would be a simple self-regulating system.

Scientists have recognized for many years that organisms modify their environments and in turn adapt to their modified environments. This process of coevolution is also not self-regulation in the Gaia sense. In the words of biologists Connie Barlow and Tyler Volk, “Coevolution and Gaia are world views apart.” Lovelock differentiates Gaia from coevolution, arguing that coevolution does not allow for active regulation of the environment by living things. Instead, as he puts it, coevolution “accepts the dogma of mainstream biology, which is that organisms simply adapt to changes in their material environment modified by the organisms themselves.” On a more aesthetic and philosophical level, Lovelock criticizes coevolution because “it does not see the earth as alive in any sense, nor as a physiological system.” Lovelock is also critical of the “Spaceship Earth” concept Spaceship Earth concept that became popular following the Moon landings of 1969 through 1972, arguing that the concept is too human-centered—it treats the biosphere as a mere life-support system for human survival.


The Gaia hypothesis has been more favorably received by interdisciplinary scientists who work across the frontiers of biology and other disciplines than by biologists themselves. The hypothesis has generated controversy on several levels. First, it has generated debate over its status as a scientific concept. To qualify as a scientific concept, an idea must be testable in some sense. One of the most widely applied criteria of testability is falsifiability: For an idea to qualify as a scientifically legitimate hypothesis, there must exist some test capable of proving the idea wrong, and the idea must survive the test. Ideas that cannot be falsified are not necessarily invalid, but they belong to the domains of philosophy, theology, or metaphysics rather than to science. Many critics of the Gaia hypothesis argue that the concept is so broad and so vaguely defined that there is no imaginable way to test the hypothesis, thus it is a philosophical notion rather than a scientific one.

Some supporters of Gaia acknowledge the lack of tests for the hypothesis but argue that the concept is useful in two ways: It can serve as a paradigm or overall worldview within which scientists can integrate their theories and observations, and it can serve as a heuristic device—that is, as a means of generating new ideas and approaches to research.

Another level of debate on Gaia concerns the scientific validity of the claims made by proponents of the Gaia hypothesis. One serious criticism of the Gaia concept is that natural selection cannot apply to a single organism. If Gaia is the sum total of all the environmental feedbacks and evolutionary mechanisms on Earth, what is to prevent some organism from evolving in a way that benefits the organism in the short term but ultimately harms Gaia as a whole? It is conceivable that such a change might succeed in causing the extinction of all life, including the organism itself. The list of stabilities that proponents of the Gaia hypothesis claim to explain is impressive, but it is also easy to list examples of processes that seem to violate self-regulation. Forests, for example, accumulate dead vegetation that can ignite and destroy the forest. Algal blooms in a body of water can consume so much oxygen and nutrients that the blooms kill all other life in that body. If the algae Algae become thick enough, they cut off the light needed for their own survival. The most dramatic departure from self-regulation is the biologically created change from a primitive oxygen-poor atmosphere to the present-day oxygen-rich atmosphere. These examples weaken the case for self-regulation.

Perhaps the most powerful criticism of the Gaia hypothesis, however, is the lack of any identified mechanisms for sensing change and responding to it. Although myriad interactions take place between the biosphere and its environment, nothing analogous to the features of a true self-regulatory system has been unambiguously identified.

For supporters and critics alike, the Gaia hypothesis is probably most important as a philosophy. The Gaia concept is not inevitably an environmentalist doctrine, although it is widely embraced within the environmental movement. Lovelock’s connections with industry and his criticisms of some environmental positions of the 1970’s led some environmentalists of that time to condemn the Gaia concept as a license to pollute, an assurance that the self-regulatory mechanisms of Gaia would correct any human disturbance. This early criticism of the Gaia concept largely disappeared as a result of Lovelock’s later writings and because of a growing general appreciation of the environmentally positive aspects of the Gaia concept.

The Gaia concept appeals to a variety of philosophical viewpoints, such as the idea that all life is interconnected. Others see the concept as a holistic approach that treats Earth as a whole, as opposed to the traditional reductionist approach in science that examines small subsets of nature. The use of a feminine figure as the symbol of the concept appeals to those who believe that science and religion have been too dominated by masculine images and values.

The features of the Gaia concept that appeal to supporters are often the same features that irritate critics. Some critics consider the Gaia hypothesis an element in the growth of mysticism, irrationality, and antiscience. Others warn of the danger of ideological misapplication of the theory and are suspicious of ideological pressure to accept a concept that lacks the support of scientific evidence. Gaia hypothesis
Environmental awareness;Gaia hypothesis

Further Reading

  • Barlow, Connie, and Tyler Volk. “Gaia and Evolutionary Biology.” BioScience 42 (October, 1992): 686-693. Pro-Gaia article, written at a moderately technical level, summarizes and attempts to respond to criticisms of the Gaia concept.
  • Joseph, Lawrence E. Gaia: The Growth of an Idea. New York: St. Martin’s Press, 1990. Somewhat rambling and loosely organized history of the Gaia concept provides extensive discussions of its reception by various groups and its application to various social, political, and religious worldviews.
  • Lovelock, James. The Ages of Gaia: A Biography of Our Living Earth. New York: W. W. Norton, 1988. A largely nontechnical history of the Gaia concept and a summary of Earth’s history from a Gaian perspective. Includes the “Daisyworld” illustration of self-regulation (Daisyworld is a hypothetical world in which flowers of varying colors regulate temperature changes).
  • _______. Gaia: A New Look at Life on Earth. 1979. Reprint. New York: Oxford University Press, 2000. The book that put the Gaia concept into public view. Written for general audiences. Chapters discuss early conceptions of Gaia, control mechanisms, the atmosphere, oceans, and human impacts on Gaia.
  • _______. Healing Gaia: A New Prescription for the Living Planet. New York: Crown, 1991. An application of Gaian concepts to environmental problems, using medical terminology as an organizing theme. Written for general audiences and illustrated in color.
  • _______. The Revenge of Gaia: Earth’s Climate Crisis and the Fate of Humanity. New York: Basic Books, 2006. Discusses the topic of global climate change as it is related to the Gaia hypothesis. Includes illustrations and glossary.
  • Mann, Charles. “Lynn Margulis: Science’s Unruly Earth Mother.” Science 252 (April 19, 1991): 378-81. Presents a kindly, nontechnical treatment of Margulis’s scientific career and the controversy surrounding her views on Gaia. Includes an inset box that lists a few of the most significant arguments for the Gaia hypothesis.
  • Schneider, Stephen H., James R. Miller, Eileen Crist, and Penelope J. Boston, eds. Scientists Debate Gaia: The Next Century. Cambridge, Mass.: MIT Press, 2004. Collection of essays by contributors from numerous scientific disciplines shows how viewpoints on the Gaia hypothesis have changed over time.
  • Williams, George C. “Gaia, Nature Worship, and Biocentric Fallacies.” Quarterly Review of Biology 67 (December, 1992): 479-486. Mildly technical critique of the Gaia hypothesis points out apparent violations of self-regulation in the biosphere. Provides interesting historical perspective on early theorists who anticipated features of the Gaia concept.

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