The Judeo-Christian view of environmentalism is typically one of stewardship. We ought to care for the environment because it is a gift that God has bestowed on us (Gen. 1:28-31 - the term, "subdue" should not be interpreted as "exploit").
I also came across this passage in the Koran that we can likely agree with insofar as it accords with Biblical teaching: "So remember (all) the bounties of Allah and do not evil, making mischief in the earth" (Surah 7:74).
Under a divinely-instituted caretaker understanding of environmental ethics, we can make sense out of our obligation to care for the earth, and for the environment, generally-speaking. The environment has an intrinsic value to it because a personal agent (God) has created and designed it, and only persons have value or can give value to something.
For the naturalist, though, environmentalism seems out of place. I suppose the naturalist could argue that our care for the environment is pragmatic, e.g. we need to care for the environment in order for human beings to flourish. But of course, why should human beings be so highly valued? Are we not deceiving ourselves, under naturalism, by acting as if we are worth more than the impersonal environmental forces we are so oddly concerned about?
Of course, I am convinced that rationality, intelligence, intentionality, and value are all attributes of human beings best explained by an ultimate cause that possesses those same attributes, albeit in an analogical way.