Beavers are a very special type of keystone species, which is what the GP is getting at. Sea stars and wolves, for example, are keystone species in many habitat

Beavers are a very special type of keystone species, which is what the GP is getting at. Sea stars and wolves, for example, are keystone species in many habitats because they control herbivore populations but that impact pales in comparison to habitat building animals like reef-building corals or beavers.