British scientist James Lovelock, working with American microbiologist Lynn Margulis, developed the Gaia hypothesis during the 1970s. It proposes that:

Living organisms and the physical Earth interact to form a single, complex, self-regulating system.

Life does not simply adapt to the Earth. It also changes the atmosphere, soils, oceans and climate. These changes can create feedback mechanisms which help to keep conditions suitable for life.

Examples include:

• Plants remove carbon dioxide and release oxygen.
• Forests influence rainfall, temperature and cloud formation.
• Marine organisms affect atmospheric gases and the carbon cycle.
• Soil organisms recycle nutrients and help vegetation grow.
• Changes in vegetation can alter how much sunlight the Earth absorbs or reflects.

Lovelock illustrated the idea with his Daisyworld computer model. An imaginary planet contains black and white daisies. Black daisies absorb heat, while white daisies reflect it. As the planet warms or cools, one type becomes more successful than the other. Their changing proportions help stabilise the planet’s temperature without any conscious organisation.

Gaia should not be understood as saying that the Earth is literally a conscious being. Lovelock argued that planetary regulation could emerge naturally from countless interactions between organisms and their surroundings. There need be no plan, controller or foresight.

The strongest claim, that the Earth always acts to produce ideal conditions for life, remains controversial. However, the more modest proposition that life and the physical environment form an interconnected, evolving Earth system has become influential in modern Earth-system science. A useful scientific history of the hypothesis explains this development.

Gaia and localism

Gaia fits naturally with localist thinking. A locality is not merely an administrative or economic unit. It is part of a living system consisting of people, soil, water, plants, animals, climate and energy flows.

This means that damaging local soil, water or woodland eventually damages the human economy as well. Conversely, rebuilding soil fertility, retaining water, planting suitable trees and keeping nutrients circulating locally strengthen both nature and the locality.

Gaia therefore suggests an important principle:

The economy is not an independent machine standing above nature. It is a dependent part of the Earth’s living system.

Lovelock introduced the idea in scientific papers before making it widely known through his 1979 book, Gaia: A New Look at Life on Earth. A good short overview is provided by the Smithsonian account of Lovelock and his Gaia theory.