I agree, thanks for the response and counter-response. One of my main concerns is genetic variation (or the lack of it). In any ecosystem, it seems that genetic variation is the primary source of adaptation. While it is nice to have corn with higher yield, I worry what might happen to very large pieces of land when there is only 1 kind of corn planted on it.
BTW, The Triple Helix by Lewontin was a favorite read from college. It's short and fascinating. Everyone should read it!