I believe this planet, like everything else, is a process, and that we are a part of that process. The earth has never been, is not now, nor will it ever be in static balance. There are balances, but they are constantly shifting. There is no "correct" state for the earth to be in. That doesn't mean we can't do things that make it less hospitable to us. But the earth doesn't care one way or another any more than it cares if an asteroid plunges in to it and brings mass extinction and an ice age.
Like any religion, Environmentalism has its good points in the ways that it encourages "good" behavior (in this case conservation and preservation). And like any religion, the more zealous the adherent, the more tunnel vision he develops, and the greater the potential for damage to others and humanity as a whole he becomes. And like any religion, it is ultimately based on a myth. While myths can be powerful, useful, and worthwhile - they also, as I mentioned above, have the potential to drive the over-zealous to all kinds of bizarre conclusions and actions -- in many cases undesirable actions. It has even led to (so far relatively minor, thankfully) cases of environmental terrorism.
A rational human familiar with the history of the planet knows that the planet has changed dramatically, often catastrophically, without any input from humans in the past. Gigantic super-volcano eruptions, asteroids and comets, wobbles in the tilt of the planet, orbital variations, and variations in solar output have all caused massive extinctions, changes in global vegetation, ice, temperature, sea levels, etc over the millennia. These are all considered natural. Only human impact is considered unnatural. It is as if everything on and of this planet is natural except for us, as if we are not on and of this planet.
It is, in effect, an anti-human religion.