The Benefits of Maintaining Biodiversity

This is the variety of species in a small area such as a pond, a hedgerow or a school field. A local area with many species is more likely to provide services such as pollination of crops, clean water and healthy soil for the people who live there.

This is the variety of all the species on the whole Earth, which is made up of millions of species. Human activity has greatly increased the rate of extinction, and a species that dies out in one ecosystem may be lost for ever if it lived nowhere else.

Global biodiversity is the sum of all the local ecosystems. Protecting species in many local places protects the planet's biodiversity as a whole.

In an ecosystem with many species there are many food chains linked in a web. If one species declines, the animals that ate it have other food, so the ecosystem is better able to cope with disease, drought or a changing climate.

Plants, pollinators, herbivores, predators and decomposers all depend on each other. Keeping the full range of species keeps these links working, such as bees for pollination and decomposers for recycling minerals.

More species, and more variation within each species, means that there are more alleles available. This gives the living world a better chance of adapting when conditions change.

Many different organisms help to keep soil fertile, to break down waste and to filter water, so these services continue.

Wild relatives of crop plants have alleles for disease resistance and drought tolerance that can be bred into crops, and insects pollinate about one third of the food crops people eat. Fish stocks need healthy ecosystems.

Many drugs come from living organisms. Aspirin was first made from a chemical in willow bark, quinine for malaria comes from cinchona bark, and the rosy periwinkle of Madagascar provides drugs for leukaemia. Species that we have not yet studied may hold cures that would be lost if they die out.

People use wood, fibres, rubber, dyes and many other materials from wild species, and these are only available if the species survive.

Forests and oceans take carbon dioxide out of the air, and wild places support jobs in tourism and give people places to relax. Many people also believe that every species has a right to exist.

National parks, nature reserves and marine reserves protect habitats from building, farming and hunting, and give animals a safe place to breed.

Laws ban the hunting of rare species, and international agreements ban the trade in endangered animals and products such as ivory, which cuts the demand for them.

Zoos and breeding centres breed endangered animals and, where possible, release the young into the wild. Records of which animals are related are kept so that mates are matched to keep the gene pool as varied as possible.

Replanting hedgerows, restoring wetlands and creating wildlife corridors that link habitats gives animals more room to feed and breed, and cuts the risk of inbreeding.

Conservation can be expensive, it can conflict with farmers and local people who need the land, captive populations can have little genetic variation, and an animal bred in captivity may not survive in the wild.

A forest provides food and shelter for many species, so planting native trees gives animals, fungi and other plants a habitat to move back into and increases biodiversity.

Trees take carbon dioxide from the air for photosynthesis and store the carbon in wood, so they remove a greenhouse gas from the atmosphere. This helps to slow global warming.

Roots bind the soil together and the trees take up water from it. This reduces erosion, lowers the risk of floods and landslides downstream, and keeps rivers clearer.

Replanted forests supply sustainable timber, protect water supplies and give jobs. The limits are that it takes decades for trees to mature, it costs money, and the land may no longer be available for growing food.

Look for data, such as a rise in the numbers of an endangered animal or in the area of forest, and work out the percentage change.

A scheme that works only while money is flowing is not sustainable. The best schemes give local people jobs or income from tourism and sustainable timber, so they have a reason to protect the species or forest.

Planting a single fast-growing species of tree makes a plantation, not a forest. Restoring the biodiversity needs a mixture of native trees, and time.

Land used for reserves or trees cannot be used for farming or housing, so a balance between the needs of people and wildlife must be found.