Biodiversity is the variety of different species living in an ecosystem. Keeping it high is important locally and globally. Species in an ecosystem are interdependent, so losing one species can affect many others through food webs. An ecosystem with high biodiversity is more stable, because if one species is lost, others can fill its role.
Humans also rely on biodiversity. We get food, medicines and materials from other species, and many species have not yet been studied and could be useful in future. Insects such as bees pollinate crops, so losing them would reduce the amount of food people can grow. Locally, biodiversity supports healthy ecosystems and jobs such as tourism. Globally, it helps keep the whole biosphere stable and protects future food supplies.
Animal species can be conserved by breeding programmes in zoos, by protecting their habitats in nature reserves and by laws that ban hunting. Breeding programmes help conserve endangered species by building up numbers that can be released into the wild.
Reforestation means planting trees on land where forest has been cleared. It restores habitats, so wildlife returns and biodiversity increases. The trees also remove carbon dioxide from the air by photosynthesis, and their roots help stop soil being washed away.