As a population reaches its carrying capacity, resources become more scarce.

[Tom Johnson]

Which of the following would incr? A. Competition
B. Birthrate
C. Nesting sites
D. available shelter

 

[Irv S]

A. and read the news to wacth it happen in real life here on Earth.
it's already happening with oil, and likely to happen with food in your lifetime.

 

[Fred Barrio]

Pretty Sure A would because there would be less resources to go around.