Keystone Species

ecosystems · nature's balance · predators · food chains

What's in a name?. The term "keystone species" comes from the wedge-shaped stone at the top of an arch that holds all the other stones in place. Without it, the whole arch falls apart. That's exactly how these special species work in nature.

Big effect, small numbers. A keystone species can be rare or not the most common animal around, but it still controls its entire ecosystem. Wolves are a famous example: even though they're not everywhere, they shape the whole forest by hunting deer and changing how plants grow.

Everything depends on them. Without keystone species, an ecosystem would look completely different or might not exist at all. They keep the balance that allows thousands of other plants and animals to survive together in the same space.

A scientist's discovery. A zoologist named Robert T. Paine came up with the keystone species idea in 1969 by studying starfish and sea urchins. He found that removing one small starfish changed an entire ocean ecosystem.

Hunters rule the ecosystem. Some keystone species are apex predators like wolves and lions, meaning nothing hunts them. By controlling what they eat, they stop other animals from becoming too numerous and taking over.