What will happen if a country is over populated?

It will not be able to sustain itself. Expect depletion of Natural Resources, including soil that will be able to grow sufficient crops and degrading and scarcity of drinkable water and rising fuel costs. When soil becomes poor, farmers might over fertilize it chemically, which will make it food more expensive in the short run and add to the toxicity in the land and water, creating long-term problems. It will result in cyclical problems. As farming becomes less economically viable, people will move to cities leading to urban sprawl. Increasing urbanization will consume more agriculture land.

Overpopulation will also lead to other environmental pressures, including higher carbon dioxide levels. Overpopulation will result in overcrowding, creating economic problems as economic growth becomes more difficult to maintain. Crime, hunger and other issues can be expected as prices for the basics outpace earning ability.

There may be an increase in aid from other nations, but this also cannot be depended upon to last. The country is threatened with loss of economic power and political might. It may resort to war to gain what it cannot maintain, either on its own or through political alliances.

The nation may legally or informally resort to population control, whether its limit on child births or abortion or infanticide, particularly if boys are desired for reasons such as economic-earning potential.