Science
What is A keystone species?
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.
See it, don’t just read it.
Watch a 2-minute lesson with voice + animation that explains a keystone species.
Key things to understand
- 1Its impact on the ecosystem is much bigger than its abundance suggests.
- 2It often controls the populations of other species, keeping balance.
- 3Sea otters protect kelp forests by eating sea urchins.
- 4Removing it can trigger a cascade of extinctions and collapse.
- 5Predators, grazers, and even plants can be keystone species.
Frequently asked questions
- 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.