Haven't some of the enviro groups in recent years come out against immigration altogether? I'm certain I've heard the Sierra Club mentioned in that light. Not sure if they distinguish Illegals in any way, though.
I recall a story a few years ago of an RV full of Cambodians headed from SoCal to NorCal for a wedding. For some reason, the RV was pulled over, and the cops found they were carrying over 60 endangered Desert Tortoises that they'd poached for some sort of ritual dish at the Cambodian wedding.
Kinda funny to consider the muticultural implications.