Alas, they really don't go anywhere for theory which is symptomatic of most activists. I met somebody I know from work at the Globalization Conference at Riverside Church we attended a few years ago. She considers herself a green and has worked with various groups on various issues. She is also working on a PhD at Columbia Teacher's College, probably the most prestigious teacher's college in the country. She is also very well-read, from Chomsky to people like Shiva. But in terms of consciously trying to wed a theory to her activity, nothing like this takes place. She, like the 2 or 3 thousand mostly young people at the conference, get active around a sense of justice. The thought of indigenous peoples being exterminated at the altar of Mammon, unlike many of our Marxists, upsets them greatly. They also think it is insane to turn Redwood trees into fancy furniture. They know enough about what this does to biodiversity in the Pacific Northwest to become an activist.
The same thing was true of the students who joined the Vietnam antiwar movement, like me. We didn't even know there was something called "imperialism" that Lenin wrote about. We just turned on our TV's at night and saw villages being destroyed senselessly. A small fraction of this movement became conscious Marxists because Marxists made a strategic decision to build the movement.
In the green movement, there are very few Marxists except for the occasional Joel Kovel. Hence when people begin to seek a systematic explanation for ecological destruction they see around them, they will naturally accept the arguments of someone like Shiva at face value. They will believe the problem is Cartesian rationalism, modern science, male domination, etc. The whole effort of people like Foster, Jim O'Connor, etc. is to alert Marxism to the urgency of this movement so as to inspire some Marxists to commit themselves to this movement. I am not sure how successful they have been. I am afraid they are dealing with a century of mistaken notions within our movement that are partially the fault of Stalinism, but also the tendency of Trotskyism as well to worship industrial "progress" uncritically.
Louis Proyect (http://www.panix.com/~lnp3/marxism.html)