Kudos to my wife, Kate, for doing the research on this.
Several groups that have been described as racist or hate based by the Southern Poverty Law Center are attempting to push their agenda by hitching their messages to the environmental movement.
One typical group is Negative Population Growth. http://www.npg.org/ This group has recently been advertising in magazines such as E - The Environmental Magazine.
More on the flip
It turns out that this group has ties to other groups either founded or funded by John Tanton.
Tanton has founded or funded numerous anti-immigrant groups such as The Center for Immigration Studies and Population-Environmental Balance.
More on Tanton at http://www.splcenter.org/intel/intelreport/article.jsp?sid=72
These anti immigrant groups also recently attempted to get some of their people elected as board members of the Sierra Club. Morris Dees, founder of the Southern Poverty Law Center, helped efforts to expose the truth about the anti-immigrant candidates running for the Sierra Club board of directors.