text: how does the population impact on the environment? how do birth, death, fertility, and migration rates affect population size? what factors can affect these rates? well fertility has to do with how many babies, or new people, there are. death lowers the amount of people we have. migration is when people come to another place, affecting the amount of people there. good environmental conditions can raise fertility, people like to move to nice areas, and crappy areas might cause death, if there is too much radiation, smog, etc.