He said he was surprised by how few studies show evidence of wolves, bears, and cougars having an effect on elk, moose, and deer populations. Instead, the biggest driver of changing elk population numbers across the West is humanity.
“In most mainland systems, it’s only when you combine wolves with grizzly bears and you take away human hunting as a substantial component that you see them suppressing prey numbers,” Wilmers said. “Outside of that, they’re mostly background noise against how humans are managing their prey populations.”
In some studies, ungulate populations actually increased slightly in the presence of wolves and grizzlies, Wilmers said, likely because human wildlife managers overestimated the effects of predators as they reduced hunting quotas.
“This is a much-needed review, as it is well executed, and highlights areas where more research is needed,” said Rae Wynn-Grant, a wildlife ecologist and cohost of the television show Mutual of Omaha’s Wild Kingdom Protecting the Wild, in an email to Inside Climate News. Wynn-Grant was not involved in the paper, and her work was not part of its survey.
In her view, the paper showed that an increase in predators on the landscape doesn’t automatically balance plant communities. “Our world would be much simpler if it did,” she said, “but the evidence suggests that so many variables factor into if and how ecosystems respond to increases in carnivore population in North America.”
Yellowstone, with its expansive valleys, relatively easy access, and status as an iconic, protected landscape, has become a hotspot for scientists trying to answer an existential question: Is it possible for an ecosystem that’s lost keystone large carnivores to be restored to a pre-extinction state upon their reintroduction?
Wilmers doesn’t think scientists have answered that question yet, except to show that it can take decades to untangle the web of factors driving ecological shifts in a place like Yellowstone. Any changes that do occur when a predator is driven to extinction may be impossible to reverse quickly, he said.
Yellowstone’s alternative stable state was a point echoed by researchers in both camps of the trophic cascade debate, and it is one Wilmers believes is vital to understand when evaluating the tradeoffs of large-carnivore reintroduction.
“You’d be better off avoiding the loss of beavers and wolves in the first place than you would be accepting that loss and trying to restore them later,” he said.
This story originally appeared on Inside Climate News.
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