Is life its own worst enemy?

Stated briefly, the Gaia hypothesis is that life as an aggregate interacts with the physical environment in such a way that it not only keeps the Earth habitable but continually improves the conditions for life. It does this through a series of feedback systems similar to biological homeostasis, the mechanism by which living organisms maintain a stable internal environment. Those aspects that most affect the habitability of the planet - temperature, the chemical composition of the oceans and fresh water, and the make-up of the atmosphere - are not just influenced by life, they are controlled by it. New Scientist