New study questions effects of reintroducing top predators

phys.org | 10/16/2018 | Staff
bluelilly (Posted by) Level 3
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For years, scientists have assumed that when top predators are reintroduced to an ecosystem, the effects are predictable: The ecosystem will return to how it was before the predators were wiped out.

Now, University of Wyoming researchers have published a study showing that there's little evidence for such claims. This has big implications for wildlife conservation in places such as Yellowstone National Park.

People - Story - Yellowstone - Wolves - Wolves

Most people are probably familiar with the story of Yellowstone's wolves. Wolves were wiped out in Yellowstone in the 1920s and, in their absence, elk became much more common and ate so much vegetation that it degraded the ecosystem.

Wolves were reintroduced to Yellowstone in the mid-1990s and over the next two decades brought profound change to the ecosystem. The number of elk decreased, while the number of aspen, willow and cottonwoods increased. Biologists observed positive responses by other animals, from songbirds to beavers. Scientists assumed that Yellowstone's ecosystem is on its way to being restored to historical conditions.

Study - Questions - Conditions - Predators - Predictability

But this new study questions that assumption: Do we really know what those historical conditions were? And, does reintroducing apex predators alter ecosystems with any predictability at all?

The team of researchers from UW, Yale University and the University of British Columbia-Okanagan set out to find the answer. The results were published in the journal Biological Conservation earlier this week.

Ecosystem - Restoration - Carnivore - Reintroduction - Relies

Ecosystem restoration via large carnivore reintroduction relies on two critical assumptions. First, large carnivore reintroduction has to initiate a predictable trophic cascade—that is, where carnivores reduce the abundance of herbivores, which, in turn, increases the abundance of the plants they feed on. Second, the magnitude of that trophic cascade has to push an ecosystem back to a previous state.

But lots of other things can happen, too. Reintroduction of large carnivores might not affect the ecosystem much at...
(Excerpt) Read more at: phys.org
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