Many species have become extinct each year before biologists can identify them.

Although tourism is often called 'the smokeless industry', or an environmentally-friendly industry, it can actually damage nature.

Overpopulation in big cities has severely affected the air and water quality.

The emergence of the Internet has completely changed the way people exchange information.

One of the approaches to reduce the impact of noise pollution on schools is to plant more trees.

It is found that endangered species are often concentrated in areas that are poor and densely populated, such as much of Asia and Africa

Ecotourism needs to recruit better educated people, so it won't provide more jobs for the local people.

Mass tourism may cause numerous problems.

Cuting down trees or hunting wild animals may upset the ecological balance of an area.