humanity is in deep trouble. global warming is going to shake the planet, and will disrupt human economy a lot, or worse. it may kill us all. if it doesn't, resource depletion will have similar consequences, in a longer time frame. then there's the four horsemen, who will be riding along with these natural events.
all of these problems grow out of a simple fact: there's too many humans on this mud ball. when we were only one billion, the forests and fish were pretty much what they had been for a long time. the air quality was as usual, except over a few cities. there was enough water drink, and bathe in, as it was since man came on the scene.
if we had stayed at one billion, all of the major problems with nature would not exist. which suggests to me that we should be thinking about ways to stabilize, and reduce, the population. it is blindingly obvious that this is the only long term solution to humanity's problems.