Do we now. Says who, you and Dr Doom. Hmm, I travel much, I see vast tracts of uninhabited land, land with good soil and ample water.
On a similar thread a few months ago some FReepers helped me calculate that you could comfortably fit all the people in the entire world into Texas (actually you could put them in Nebraska).
Have any of you naysayers considered the possibility that he may be right?
The biggest problem with the earth's population is that those who can least afford kids are having the most. And all those Third Worlders are invading the developed world.
Locate a copy of the book "Camp of the Saints". It'll scare the hell out of you.