Hi Ben
I tend to agree with Brian in that it really depends on how one defines religion. Sometimes, one's religion is part of an organized (or somewhat disorganized at times

) belief system which may or may not speak to the idea of taking care of the environment. However, it seems to me that the issue is often addressed by these systems, either by direct command, or by a general idea of how we are to treat all things.
In cases where there is no written, organized doctrine, there are still many cultures who have, over the ages, been extremely environmentally aware. This might often be due to necessity, but I think it also can go somewhat beyond to a sense of spiritual responsibility--a mutual respect with nature, or perhaps a need to care about the things around us that sustain and enhance our existence.
And I might venture that there could actually be a contemporary, organized religion out there somewhere with environmentalism at its core. I know there are certainly individuals who "religiously" practice love for the environment. (Lots of us tree huggers here in CR, too!)
Best wishes for a great dissertation...
InPeace,
InLove