This is the breaking up of large natural places into smaller fragments or islands of habitat. National parks and nature reserves are some examples. Just as your own back garden is too small for a population of tigers to survive, small areas of habitat cannot hold the same number of species that large ones can. Many of the world's nature reserves could lose their plants and animals gradually over time if they are too small.

Although half of the Earth's original forests still remain, less than half of these are in large patches that can hold large numbers of species. Many of the smaller national parks of America have lost numbers of their larger mammal species, or they can only be maintained by strenuous efforts.

The larger animals are the ones that need larger areas of habitat. But since no species exists in isolation, if a species disappears then the other species that depend on it and interact with it are also affected. When Jaguars disappeared from the tiny island of Barro Colorado in Panama, the whole ecosystem changed. Even if small populations of plants and animals can hang on, their populations may be too small to survive for long. Tigers, pandas and mountain gorillas may number several hundred in the wild, but often the individuals are separated from each other by farms and villages.

Make natural habitats as big as possible, and join together the small ones with habitat corridors. This allows animals to move between isolated areas which keeps their populations large and healthy. In some parts of the world, adjoining countries are connecting their national parks across international borders to make really big parks in a project called 'The Peace Parks Initiative'. This appears to be benefiting local wildlife, and the local people who depend on it.

| habitat loss | introduced species | pollution | | over harvesting | fragmentation |