Biodiversity is important for sustainability. That is because biodiversity is the presence of life of plants, animals and other species that exist together to let the environment have a life. An example is that in a forest there are trees and shrubs and ferns and many other types of plants and trees. There is also the presence of animals and insects. The presence of one species is needed for the other species. If one species would be wiped out then there is an imbalance in the biodiversity.
The balance of the existence of one special with another is important. An example is that snakes are not that much welcome because of a danger they pose and that people are afraid of them. This snake likes to eat rats. Then if snakes are wiped out the rat problem would balloon. That is why a balance should be maintained. Not too many snakes or the rat. The different locations have different situations as the weather and availability of natural resources also is different.
There are types of biodiversity and that is genetic diversity, ecosystem diversity, and species diversity. This three types should be able to exist as we already said that the balance should be created as it can become too many or lacking. An animal with a specific gene with specific character should continue to exists. The species to have different varieties. Like one mushroom, it has many varieties that you could find. If the biodiversity increases, it means the forest (and other places) is healthy.