The Boston Globe has this article challenging the fundamental assumption of the "Gaia Hypothesis", which assumes that the Earth's ecology will heal itself if given time and respite from human activity. The new "Medea Hypothesis", proposed by Dr. Peter Ward, suggests that mass extinctions are also caused naturally by the Earth, and we need to now be proactive in preventing the next one.
"Ward himself believes that the only help for the planet over the long run is management by human beings - whether that means actively adjusting the chemical composition of the atmosphere or using giant satellites to modify the amount of sunlight that reaches us. As Ward sees it, the planet doesn't need our help destroying itself. It will do that automatically. It needs us to save it.