Trophic cascades are powerful indirect interactions that can control entire ecosystems.
In the early 1900s, when wolves roamed Yellowstone, young trees such as aspen and willow were abundant. In 30 years, after wolves were hunted out, the forest stopped regenerating. Reintroducing wolves into Yellowstone National Park after nearly 70 years of absence has been controversial. However, the effects have been utterly transformative to the Yellowstone ecosystem.
A trophic cascade recently has been reported among wolves, elk, and aspen on the northern winter range of Yellowstone National Park, Wyoming, USA.
What is a trophic cascade and how exactly do wolves change rivers? What happens when a species that has been hunted to extinction is introduced to its happy hunting grounds after 70 years? Find out in this beautiful little film.