This was posted as a link the other day by Susan Schwartz in a comment to an article I posted. It is an outstanding, compelling, and heartwarming example of how one small change can alter the landscape--a small change that I recall ranchers howling and screaming about, when it was ultimately in their own best interest, along with humankind in general. I've seen over the years many such examples, but this video, in a little over four minutes, might just well surpass any biology you learned in college (I was a bio major for four years, and this short clip hits the nail on the head; worth watching a few times, imo).