<p>Beavers are considered a keystone species for the way they shape their ecosystems by building dams that, in turn, create a wetland habitat in which many other species thrive.</p>

Beavers are considered a keystone species for the way they shape their ecosystems by building dams that, in turn, create a wetland habitat in which many other species thrive.

Photograph by Joel Sartore, National Geographic Photo Ark

Why some animals are more important to ecosystems than others

Keystone species, scientists have discovered, play a critical role in conservation efforts. Here’s why.

Ecologists have long understood that the diversity of an ecosystem is at the heart of its stability. A groundbreaking discovery in the 1960s took it a step further and changed the way scientists thought about biodiversity and the effects species have on one another. Robert Paine, then a young researcher at the University of Washington, demonstrated there are certain species that can radically change the diversity of their communities—and whose loss could cause cascades of destruction within the ecosystem. He called these “keystone species.”

Named for an architectural term—the keystone is the topmost stone in an arch that holds the entire structure together—keystone species are defined as species that have a disproportionately large effect on the communities in which

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