Here is Tim lenton’s conclusion to his article in Nature which James Lovelock describes as a “seminal article” (The revenge of Gaia p32).  In it he describes how the earth keeps to its goal of sustaining habitability through a number of feedback loops.

“When asked to explain how planetary self-regulation could have arisen, we are in much the same position as Darwin when asked how the eye could have evolved. We see a complex phenomenon and have only the beginnings of a theory with which to tackle the puzzle. Darwin focused on the exponential growth of organisms, the constraints imposed on them by their environment and the resultingnatural selection. The fact that organisms also alter their environment means there is an inevitable feedback connection between the living and non-living. I have tried to describe the forms that such a connection could take. The implications may be far reaching; simple principles suggest that environmental regulation can emerge at levels from the individual to the global. Natural selection is seen as an integral part of Gaia, and Gaia theory also has something to offer evolutionary biology. Gaian models suggest that
we must consider the totality of organisms and their material environment to fully understand which traits come to persist and dominate”.
T. M. Lenton

http://adi-38.bio.ib.usp.br/0440041/2006/lenton1998.pdf