Biodiversity is the variety of different living organisms in an ecosystem. It can be local, such as the species in one pond or wood, or global, meaning all the species on Earth. A high biodiversity makes an ecosystem more stable. If one species declines, other species can take its place in food webs, and species that depend on each other, such as insects that pollinate flowers, are more likely to survive.
People depend on biodiversity. Plants and animals give us food, timber and other materials, and many medicines come from plants. Wild relatives of crops carry genes, such as genes for disease resistance, that breeders can use. Losing a species can mean losing a possible new medicine. Many people also value wildlife for enjoyment and tourism.
Conservation of animal species protects biodiversity. Methods include breeding programmes, protected nature reserves and laws that ban hunting. Keeping each species alive helps keep food webs intact.
Reforestation means replanting trees where forests were cleared. Trees remove carbon dioxide from the air by photosynthesis, which helps to reduce climate change. The new forest restores habitats, so animals can return and biodiversity increases. Tree roots also hold the soil, which reduces erosion and flooding.