While I think my part of the globe could use a bit more warming to ease the chilly winds lately, a lot of people are worried about the earth's slowly changing climate and what effects that might bring. Thing is, the earth's climate has been warming and cooling for millions of years without humans around. What's so different now is that humans are having an effect, and there's a philosophy about human interaction with the environment, embraced by greens, that fears any changes and has been gaining in influence.
Nature is good, humans are bad.
While razing a rainforest and leaving behind a barren wasteland is bad, it's no better to change a desert into a thriving forest or city. Overfishing where life is plentiful is as bad as the notion of creating plankton blooms and fish in an otherwise lifeless ocean. Humans are unnatural, and the more we do the worse it is. But there's nothing unnatural about manipulating the environment. Animals do it consciously all the time, like by constructing nests and other structures for homes, or unconsciously by overhunting a local ecosystem or simply ravaging a given area.