I think this is true of an environmentalist movement that wants there to be a healthy environment for humans; I’m not sure this is true of an environmentalist movement whose main goal is to dismantle capitalism.
FWIW, the environmentalist movement that I’m most familiar with from Finland (which is somewhat partisan but much less so than the US one) is neither of these. There’s some element of “wants there to be a healthy environment for humans” but mostly it’s “wants to preserve the environment for its own sake”.
E.g. ecosystems being devastated is clearly depicted as being intrinsically bad, regardless of its effect on humans. When “this is how humans would be affected” arguments are brought in, they feel like they’re being used as a motte.
EDIT: I guess climate change stuff is much more human-focused; it being so big is a more recent development, so I didn’t happen to think of it when considering my prototypical sense of “environmentalism”. (It also feels like a more general concern, with “environmentalism” connoting a more narrowly-held concern to me.)
This seems similar to the thing in Why Artists Study Anatomy and Drawing Less Wrong, that in order to produce art that accurately reproduces an aspect of reality, you have to actually learn to pay attention to reality. And by learning to produce art, you start noticing all the ways in which your brain usually filters out reality.
I think this generalizes. E.g. to write good dialogue you need to pay attention to how people actually talk and what makes for an interesting conversation; to learn to dance you need to start paying attention to your body, etc.