If I ever get rich enough to do so, I'm going to buy some land somewhere - perhaps old farming land that's no longer profitable, and just let it return to nature. Let the trees and bushes grow, let the insects, birds and whatever else breed there. I'm beginning to think that's one of the best things one could do for the planet right now.
see for example: http://theconversation.com/chernobyl-has-become-a-refuge-for...