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What is a keystone species?
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Quick answer
A keystone species is one whose presence holds an entire ecosystem together, far out of proportion to its numbers. Remove it and the whole web of life can unravel — like pulling the keystone from a stone arch. Its impact on the ecosystem is much bigger than its abundance suggests.
Key things to understand
- Its impact on the ecosystem is much bigger than its abundance suggests.
- It often controls the populations of other species, keeping balance.
- Sea otters protect kelp forests by eating sea urchins.
- Removing it can trigger a cascade of extinctions and collapse.
- Predators, grazers, and even plants can be keystone species.
People also ask
What is an example of a keystone species?
Sea otters: by eating sea urchins, they stop urchins from devouring kelp forests, protecting an entire coastal ecosystem.
Why are keystone species important?
They hold ecosystems in balance, so losing one can collapse the whole food web, even if the species itself was never numerous.
Are predators always keystone species?
Often, because they control prey numbers, but some grazers and plants are keystone too — it depends on the role, not the type.
Part of the guide: Nature & Earth: Living Things and Rocks →