The Concept of ‘ G aia’

The Gaia theory of James Lovelock proposes that the Earth is a self‐regulating system, or super‐organism, maintaining conditions hospitable to contemporary planetary biota. Objections to this theory, concerning its alleged untestability and circularity, are considered and countered. Favourable evidence includes Lovelock's Daisyworld model of a planet regulating its own temperatures and thus maintaining homeostasis, and his discoveries of actual regulatory mechanisms such as the biological generation of dimethyl sulphide, which removes sulfur from the oceans and seeds clouds whose albedo reduces solar radiation (a negative feedback mechanism). After some decades of scepticism, sections of the scientific community have partially endorsed Gaia theory, accepting that the Earth system behaves as if self‐regulating. Whether or not this theory is acceptable in full, it has drawn attention to the need for preserving planetary biological cycles and for the planetary dimension to be incorporated in ethical decision‐making, and thus for a planetary ethic.