"New research questions the long-held theory that reintroduction of such a predator caused a trophic cascade, spawning renewal of vegetation and spurring biodiversity."
"In 1995, 14 wolves were delivered by truck and sled to the heart of Yellowstone National Park in Wyoming, where the animal had long been absent. Others followed.
Since then, a story has grown up, based on early research, that as the wolves increased in number, they hunted the park’s elk herds, significantly reducing them by about half from 17,000.
The wolves’ return and predatory dominance was believed to have had a widespread effect known as a trophic cascade, by decreasing grazing and restoring and expanding forests, grasses and other wildlife. It supposedly even changed the course of rivers as streamside vegetation returned.
Yellowstone’s dramatic transformation through the reintroduction of wolves has become a global parable for how to correct out-of-balance ecosystems.
In recent years, however, new research has walked that story back. Yes, stands of aspen and willows are thriving again — in some places. But decades of damage from elk herds’ grazing and trampling so thoroughly changed the landscape that large areas remain scarred and may not recover for a long time, if ever."
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