Background on Gaia
It now seems almost certain that the Earth is the only planet in our solar system to contain life. But why does life continue to evolve and thrive here but not on other planets?
When James Lovelock was asked by NASA to help look for life on other planets, his proposal was to do a simple, earth-based analysis the chemical composition of the planet's atmosphere (rather than try to collect and analyse actual rock samples). If the planet was "dead" it would be expected to have a "dead" atmosphere - one that did not change. But a planet with life would have living things that use the atmosphere. So, the atmosphere would be ever changing. From the information he gathered and all previous data gathered about Mars and Venus, Lovelock discovered that both had atmospheres that were pretty much unchanging - indicating that there was little or no life on either of the planets.
To confirm this prediction, Lovelock looked at the atmosphere of the Earth. As he expected, he discovered that the Earth was not like Mars and Venus, but in a state of change.
Traditionally, scientists have viewed much of the earth, such as the oceans, rocks and atmosphere as 'dead' matter - that is just where organisms live. Lovelock describes the entire earth as alive - a global ecosystem - 'a single physiological system, an entity that is alive at least to the extent that, like other living organisms, its chemistry and temperature are self-regulated at a state favourable for life.'
In this hypothesis, Gaia is the Earth's control system - a changing system made up of all living things and their environment (the rocks, oceans and atmosphere). The hypothesis suggests the control of climate and atmosphere is automatic - and the control reacts as the system changes.
Humans have altered the climate and the atmosphere of the Earth for the worse. Lovelock would say that we have made Gaia sick and that we should act to restore a state of health before it's too late. It's important to note that Lovelock does not say that we are threatening the very existence of life on earth - but we are threatening the existence of those organisms that will can survive in a changed climate - organisms such as humans!
Ideas on Gaia are beginning to become more accepted - particularly now that we recognise that it is people who are increasingly responsible for the pollution of the atmosphere and the oceans, the deforestation of vast areas of rain forest and the expansion of the deserts.
