Planting trees provides some protection from the gradual wearing away of soil. What do you call this gradual degradation?

These potatoes are cultivated naturally, without using any chemical fertilisers or pesticides. What do you call these types of products?

More and more cars are being built to use fuel which has been made without lead additives. What do we call this fuel?

Due to unbalanced population control or ecosystems in danger, many animals have to be killed (e.g. hippos in Hacienda Nápoles). What do we call this population control practice?

Polluted precipitation which kills trees falls a long distance away from the source of the pollution. What do you call such precipitation?

The gases and other substances which come from factories using oil, coal and other fuels which are the remains of plants and animals can cause serious damage to the environment. What do you call this kind of fuel?

Human beings have had a devastating effect on the living things, both large and small, in many parts of the world. What do you call the community of those large and living small beings?

Friends of the Earth, Green Peace and other people concerned with protecting the environment are holding a forum in London next month. What do we call these groups?

"Don't drink that water! It's been made dirty by something being added to it!" Another way to say this is that the water is ______.

Many ecosystems are endangered by animals or plants that do not belong to these regions originally. We shall also say these animals or plants are not _____.

Many companies are developing boxes, cartoons, and cans which can be easily decomposed by organisms such as bacteria, or by sunlight, sea, water, etc. What do you call this type of material?

In many countries, illegal hunters keep killing animals for their fur, horns or other body parts. What do you call this illegal practice?

In Britain, building is restricted or completely banned in the area or farming land or woods and parks which surrounds a town. What do you call this area?