HOW WOLVES CHANGE RIVERS
Wolves were once native to the US’ Yellowstone National Park — until hunting wiped them out. But when, in 1995, the wolves began to come back (thanks to an aggressive management program), something interesting happened: the rest of the park began to find a new, more healthful balance. When the grey wolf was reintroduced into the Greater Yellowstone Ecosystem in 1995, for example, there was only one beaver colony in the park. Today, the park is home to nine beaver colonies, with the promise of more to come, as the reintroduction of wolves continues to astonish biologists with a ripple of direct and indirect consequences throughout the ecosystem. A flourishing beaver population is just one of those consequences. Other species flourished. Valleys grew back and erosion subsided changing the course of the rivers.