Die Rückkehr der Wölfe: Das Wunder im Yellowstone-Nationalpark (2017)

For 70 years, the population of the wapiti deer in the Yellowstone National Park in the United States increased unchecked. Without natural predators and despite all human attempts to check the increase of the deer population they kept spreading and destroyed vast regions of the park's vegetation. They literally defoliated the National Park. However, a well-directed reintroduction of 41 wolves between 1995 and 1997 worked wonders: The animals restored the natural balance in the National Park. The wolves hunted the wapiti and, even more crucially, they influenced their behavior so that the wapiti withdrew from the valleys and ravines. The most fascinating result of all was that the presence of the wolf did not only reduce the number of the wapiti from 20.000 to about 7.000 animals, but that the flora in the park also recovered and created new habitats for other species. Scientists and experts call this phenomenon a trophic cascade, a chain reaction created by a change in the food chain within a complex ecosystem. The documentary shows the surprising and dramatic consequences on the park's whole ecosystem that resulted from the reintroduction of the wolf. Contrary to their reputation as mercilessly killing predators, the wolves are creators of new life, restoring the ecosystem that had previously been out of whack.