It's backwards thinking, based on a moralization that mother nature is all good and human beings are all bad. If you look at all the problems associated with the "human overcrowding" problem, the solution is more knowledge, not less people. To stop overpopulation: educate and empower women. To slow carbon emissions: keep track and educate people about the consequences. You can join this particular doomsday cult if you so desire, as long as you don't try to prevent me from reproducing. I will still roll my eyes at you, but nothing more.