Such does indeed occur periodically in different locales. When it does, war usually provides a violent, if temporary, solution. The planet is running out of clean, potable water. Look unto the ruins of the Anasazi civilization in the American Southwest, among other sites, for a stark vision of what happens when water grows scarce. Unless we stop our noxious industrial exhalations, we will choke the planet.
Nature limits all life forms sooner or later.
The universe tends constantly toward more disorder and less order. The same thermodynamic processes that are ending the universe are also inexorably finishing off the human enterprise. This astrophysical explanation for social decline is a bit of a stretch, but not too far-fetched for crude Entropy enthusiasts like Jeremy Rifkin. In the end it all depends upon biology. Biology is cosmology.