Life has been evolving on Earth for over 3 billion years. Scientists have identified about 1,4 million different species. There are many more waiting to be identified, perhaps millions. This collection of vastly varied living organisms is our planet's biodiversity.

The richest parts of the planet's biodiversity are also the least well-known. It is estimated that 97% of all species on Earth live in the oceans below the zone where sunlight penetrates the water. On the continents, it is estimated that 50% of all land-dwelling species live in tropical rainforests. The first step towards preserving life on Earth is getting to know and understand it.

Throughout the history of the Earth, as new species evolve, other species become extinct. Overall, as time has progressed, there are more and more different kinds of organisms. The dinosaurs became extinct 60 million years before humans walked the Earth. What caused their extinction is still not fully understood but it was some sort of natural catastrophe.

Why should humans save species?

If animals and plants become extinct naturally, why should humans worry about the ones that they exterminate? There are several good reasons to worry:

Many plants can make things that we cannot produce for ourselves in laboratories or factories such as medicines, oils or perfumes.

Seeing an eagle soaring above a mountain or walking through a forest in springtime can be a great pleasure. In some parts of the world wildlife is an important source of income because tourists come to see the exotic organisms which live there. Kenya's savannas and Australia's coral reefs are just two examples. One does not need to go very far, however, to appreciate what nature has to offer.

• Extinction of Species : Homepage

• Some Human Activities which Modify Habitats

• Introduced Species

• The Great Barrier Reef as an example of biodiversity

• How Humans Can Help

• Natural Parks in France

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