Q. Can you help me find reliable information on how overpopulation is affecting the world's agriculture?
I recommend that you start with the library's Environmental Studies research guide at http://library.uhd.edu/environmental. The databases listed under "Quick Start for Environmental Studies Resources" should be good for your topic, particularly the first two, "Environment Complete" and "Academic Search Complete." AGRICOLA may also be helpful.
I suggest using various combinations of these words or phrases to search the databases:
You may want to combine these terms in various ways, i.e.,
overpopulation AND "food security"
"population growth" AND "food security"
overpopulation AND "agricultural production"