It is not just over-fishing and pollution, it is over-population, but nature has a way of dealing with that.
I have been aware of the start of teh next great extinction for qutie soem time. The onl yquestion in my mind is whether humans will survive it.
I am quite sure they won't. Between the environment and the nuclear weapons, and nature, there is not much chance of humanity being that lucky . . . . hence the drive to get humans to Mars, so they can fuck that planet up too.