When wolves disappeared from Yellowstone National Park, the deer population increased. This, in turn, caused a decrease in the willow tree population as the deer overgrazed on them. The decrease in willow trees led to a decrease in beaver populations as they rely on willow as a food source and building material for their dams. Additionally, the absence of wolves disturbed the balance of the ecosystem, leading to an increase in the populations of smaller mammals such as rabbits and rodents. Over time, the loss of willow trees and the changes in vegetation had a cascading effect on the ecosystem, impacting the overall biodiversity and health of Yellowstone National Park.
