Query: membership in U.S. environmental groups

[Gar Lipow <gar.lipow@xxxxxxxxx>]

Does  reasonable estimate exist somewhere for total dues paying
membership  in environmental groups - really wide specturm - Earth
First to Green Peace to Sierra Club to World Wildlife fund? I have the
membership claims for most national organizations. But that does not
begin to  capture state and local grassroots groups.  I can't help
think that sometime someone did a survey that included a question
along the line of "Have you countributed money to an environmental,
wildlife, conservation, nature or sustainability promoting
organinzation in the  last 12 months?", or generated a rough estimae
some other way.

Thanks

Gar