From The New York Times:
Beavers are influential. By cutting trees and damming streams, these rodents change the world around them, raising water levels and creating habitats for diverse plants, insects, fish and more. They are some of the world’s best-known ecosystem engineers, a term for species that produce outsize effects on their environments.
Wolves are powerful. As apex predators, their facility at killing reverberates down the food web, and their direct effect on prey species may affect vegetation, other animals and even how streams flow.