Keystone species are those of critical importance for maintaining ecological processes or the diversity of their ecosystems. A keystone species is usually a species on which the persistence of a large number of other species in the ecosystem depends. If a keystone species is extirpated from a system, the species it supports also will disappear, as will other dependent species. Where a keystone species has been identified, efforts to protect it also will help protect the other species in delicately balanced ecosystems.
Protecting keystone species is a priority for conservationists. Unfortunately, the keystone functions of a species may not be known until it has been extirpated and the ecosystem changes. Keystone species may occur at any level of the ecosystem, from plants and herbivores (plant eaters), to carnivores (meat eaters), and detritivores (waste eaters). Examples of keystone species may be top carnivores that keep prey in check, large herbivores that shape the habitat in which other species live, important plants that support particular insect species that are food for birds, bats that disperse the seeds of plants and many other types of organisms.