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Areas like tropical rainforests have millions of different species and are very biodiverse. Other areas like the Polar Regions have far fewer species and are less biodiverse.

Biodiversity is specifically the number of different species. An area with large populations of few species is not biodiverse.

Interdependence

If the numbers of one species are affected, there are almost always knock-on consequences. A simple food chain is:

algae → zooplankton → sand eel → puffin → arctic skua

If the numbers of zooplankton are reduced by pollution, such as plastic waste, then more algae will grow and the population of other consumers will fall.

Ecosystems with higher biodiversity have fewer species that depend on just one other for food, shelter and maintaining their environment. With the example above, puffins could also eat molluscs and worms. Ecosystems with higher biodiversity are more stable as they can easily adjust to changes.

We are slowly realising that the future of our species on Earth depends on maintaining high biodiversity. There are a number of reasions for this:

• Maintaining important biological resources such as food and medicines - we rely on many different species as food or sources of medicine so it is important to the health of future generations that organisms that supply us with these resources are not lost. This is an example of the importance of biodiversity on a global scale.
• For recreation and tourism - for example, forests with a high biodiversity are attractive places to visit. They benefit local people who use the ecosystem for recreation. It also provides an income to many by attracting other people to the area. This shows why local biodiversity is important.
• Activities that create air and water pollution, are reducing biodiversity in many ecosystems - conservation of species and habitats by charities, governments and individuals helps to maintain the range of biodiversity.