Study: Link between Yellowstone wolf reintroductions & aspen regeneration not as solid as advertised
Following the reintroduction of wolves to Yellowstone National Park in 1995-97, the regrowth of aspen trees became a worldwide story, highlighting the importance of large predators.
The wolves ate elk, which browsed on aspen. When elk numbers fell, aspen stands rebounded and birds and beavers returned. Such ecological effects caused by the addition, or removal, of a top predator are called trophic cascades.