Keystone Species

In architecture, a keystone is the central stone in an arch that holds the other stones in place. If the keystone is removed, the structure collapses.

A keystone species plays a key role in the structure of an ecological community by influencing the number and variety of species through ecological interactions, including predation, competition, and habitat modification.

Relative to its abundance in the community, a keystone species has a disproportionately large effect on community structure.

If the keystone species is removed, the community structure can change dramatically, often leading to major shifts in species composition.

For example, in kelp forest ecosystems along the Pacific coast, sea otters are a keystone species.

These otters consume large quantities of sea urchins, which mainly graze on kelp. Without predation by sea otters, the sea urchin population increases dramatically and can destroy the kelp forests.

Species such as fish, crabs, and clams that depend on kelp forests decline significantly, resulting in the formation of urchin barrens.

Biodiversity describes the variety of life in a community and is often discussed in terms of species richness, which is the number of species present, and evenness, which is their relative abundance.

Sea otters promote biodiversity by reducing the sea urchin population. They are the primary predator in the kelp forest and help regulate this population.

So, many species that live in kelp forests rely on sea otters to protect their habitat.