Greenhouse gas:gases in Earth's atmosphere that trap heat.

Planet: a celestial body distinguished from the fixed stars by having an apparent motion of its own (including the moon and sun), especially with reference to its supposed influence on people and events.

effect: a change which is a result or consequence of an action or other cause

expanding: become or make larger or more extensive.

untreated sewage: wastewater which contains harmful waterborne pathogens and bacteria and which has not yet gone through a sewage treatment plant

Air pollution: the presence in or introduction into the air of a substance which has harmful or poisonous effects.

Overfishing: deplete the stock of fish in (a body of water) by too much fishing.

fossil fuel: a natural fuel such as coal or gas, formed in the geological past from the remains of living organisms.

Country: a nation with its own government, occupying a particular territory.

alternatives: one of two or more available possibilities.

endangered species: a species of animal or plant that is seriously at risk of extinction.

Deforestation: the action of clearing a wide area of trees.

Global warming: a gradual increase in the overall temperature of the earth's atmosphere generally attributed to the greenhouse effect caused by increased levels of carbon dioxide, chlorofluorocarbons, and other pollutants.