Environment.

The number of a people in an area exceeds the capacity of the environment to support life at a decent standard of living.

Natural situation in which heat is retained in Earth's atmosphere by carbon dioxide, methane, water vapor, and other gases.

A long period of dry weather.

An extreme shortage of food.

Disappearance of a species from all parts of its geographical range.

A tropical forest, usually of tall, densely growing, broad-leaved evergreen trees in an area of high annual rainfall.

The removal of trees faster than forests can replace themselves.

The shaking that results from the movement of rock beneath Earth's surface.

Air pollution by a mixture of smoke and fog.

A slide of a large mass of dirt and rock down a mountain or cliff.

A rapidly spreading and usually fatal disease.

The process by which fertile land becomes desert,typically as a result of drought, deforestation, or agriculture.

Rain that contains more acid than normal.