Gaia hypothesis

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This article deals specifically with Gaia hypothesis ideas of James Lovelock; for a more detailed discussion of how the scientific community in general understands this hypothesis, see the article on Gaia theory.

James Lovelock's Gaia hypothesis was first formally advanced by him in 1969; it states that the entire mass of living matter (also called biosphere) on Earth (or any planet with life) functions as a single and vast organism (which he named for the Greek goddess Gaia) that actively modifies its planet to produce the environment that suits its needs.

This idea is based on the holistic idea that the biomass self-regulate the conditions on the planet to make its physical environment (in particular temperature and chemistry of the atmosphere) on the planet more hospitable to the species which constitute its "life." - the Gaia Hypothesis proper defined this "hospitality" as a full homeostasis. A simple model that is often used to illustrate the original Gaia hypothesis is the so-called Daisyworld simulation.

Whether this sort of system is present on Earth is still open to debate. Some relatively simple homeostatic mechanisms are generally accepted. For example, when atmospheric carbon dioxide levels rise, plants are able to grow better and thus remove more carbon dioxide from the atmosphere, but the extent to which these mechanisms stabilize and modify the Earth's overall climate are not known.

The Gaia hypothesis is sometimes viewed from significantly different philosophical perspectives. Some environmentalists view it as an almost conscious process, in which the Earth's ecosystem is literally viewed as a single unified organism. Some evolutionary biologists, on the other hand, view it as an undirected emergent property of the ecosystem; as each individual species pursues its own self-interest, their combined actions tend to have counterbalancing effects on environmental change. Proponents of this view sometimes point to examples of life's actions in the past that have resulted in dramatic change rather than stable equilibrium, such as the conversion of the Earth's atmosphere from a reducing environment to an oxygen-rich one.

Depending on how strongly the case is stated, the hypothesis conflicts with mainstream neo-Darwinism. (How?) Most biologists would accept Daisyworld-style homeostasis as possible, but would not accept the idea that this equates to the whole biosphere acting as one organism.

Gaia hypothesis led to the new science called biogeography, or even geophysiology, which take into account the interactions between biota, the oceans and the atmosphere.

See also: Gaia theory, James Lovelock