Why isnt food the only limiting factor that keeps populations from growing too large

Food isn't the only factor that keeps populations from growing too large because humans have a higher level of thinking about reproduction so there are other factors that can control populations from growing too large. These factors can include things such as family planning, the economic thinking that goes into deciding how many children to have, and other factors as well. 

I'm going to go with 1,982 feet because of all of the ice.                                               ps its this is not the answer go with d 6,500.