Two words.
Global warming.
Seems to me the same folks who are saying Man will not exhaust the Earth's resources are the same folks who have been denying global warming. (Has anyone said where global warming will stop? Or do we just look at the bright side, as GWB says, and be glad we have longer growing seasons? What a maroon!!)
Not much of a learning curve.
And, the same folks who suggest "terra-forming" other planets for when this one is no longer liveable. (Go figure.)
If we cannot keep this place liveable, a place into which we evolved, we ain't gonna make it anywhere else where it would have to be harder.
Arf