Answer:
Something that may be affected is habitats.
Step-by-step explanation:
This is because humans decide to do create buildings and cities because their population is too high, which will make animals lose their habitats due to us chopping trees down or just laying pavement. Another thing that could happen to the environment could be pollution, this affects us all because we all breathe oxygen, so do animals. There are many other things that overpopulation can affect, but that would be too long to state, happy to help though!!! (if you want more info just look up China's pollution levels over the past ten years then look up their population over the past ten years an conpare.)