Climate change is beginning to acerbate over-population.  

What needs to be understood is "over-population" is a conclusion reached through analysis of the number of predators to the number of prey.  (Using "predators" and "prey" in an abstract sense.)  Climate change is a systematic variant (changeable) first directly lowering prey, e.g., global wheat production, which follows through to stressing and then lowering predator population.  Typically in these scenarios the predator population crashes below objective conditions for the predator population.  The typical run of events:

1.  Prey population increases
   
2.  Predator population increases
   
3.  The system become unbalanced
   
4.  Prey population crashes
   
5.  Predator population crashes
   
6.  Prey population stabilizes at a lower rate and begins to climb
   
7.  Predator population stabilizes at a lower rate and begins to climb

As the canonical Canadian hare/lynx relationship illustrates:

 

Unfortunately, there is another canonical scenario where the rate of predation is above the rate of prey population renewal and the prey goes extinct.  This seems to have happened with the mastodon; humans over-predated the species to extinction; I note Climate Change was also affective in this scenario.  Something similar is happening with oil/human "predation."  

If you will.

She believed in nothing; only her skepticism kept her from being an atheist. -- Jean-Paul Sartre