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The National Park Service has proposed transplanting up to 30 wolves to Isle Royale, a historic decision that concedes that extraordinary steps are needed to restore a healthy balance of predator and prey on the wilderness island in Lake Superior.

After years of deliberations, the Park Service has concluded in a new report that quickly introducing a significant number of wolves may be the best way to re-establish a healthy population on the island. Only two wolves are left there now — down from a one-time high of 50 — a result of disease, inbreeding and a warming climate that has reduced the frequency of ice bridges that give them a natural route to and from the mainland.

The recommendation is a remarkable switch from the Park Service's traditional hands-off policy in managing wilderness, and it elicited both praise and criticism from conservation groups.

"We are glad they are choosing an option that recognizes the critical value of wolves," said Christine Goepfert, Midwest program manager for the National Parks Conservation Association. "They serve such a critical role."

Others said the step would violate the intent of the 1964 Wilderness Act.

"We believe the [law] directs us to let nature make these decisions and not let humans manipulate them," said Kevin Proescholdt, conservation director of Wilderness Watch. The step would be a major precedent for the federal government as it tries to manage the rapidly increasing impacts of climate change across wilderness systems, he said. "They think they have to do something to keep it natural."

But the Wilderness Act was anchored in the idea that letting nature take care of itself was the surest way to preserve a natural system, a concept that may now be outdated, said Michael Nelson, a professor at Oregon State University who has studied public opinion on wolves and Isle Royale.

"We are invested in the idea that we are the agents of harm," he said. Now, Nelson said, there is a growing realization across the National Park Service and other federal land managers that sometimes climate change and other factors are so overwhelming that nature is not enough.

"We are first to struggle with this issue — when you do or don't intervene," said Phyllis Green, Isle Royale park superintendent.

In this case the isolation of the island makes it, in some ways, more fragile than many other parks and wilderness areas.

Rolf Peterson, a scientist from Michigan Technological University who leads a decades-long research project on the wolves and moose of Isle Royale, said the decline in predators has allowed the island's moose to proliferate. They are already changing the forest in significant ways, he said.

Boom and starve cycle

Left unchecked, moose numbers will likely grow to the point where they will starve, beginning a cycle of population explosions followed by dramatic crashes, according to scientists who advised the park service. The same is true of beavers that inhabit the island, also prey for wolves.

The Park Service is taking public comments on its recommendations until March 15. Then, if the plan is adopted, wolves would be trapped elsewhere and transplanted to the island starting "immediately" and continuing over three years. The Park Service also considered doing nothing or introducing a smaller number of wolves.

The boom and crash cycle has happened before. In the 1930s, moose numbers soared to nearly 3,000, decimating vegetation on the 210-square-mile island before they crashed from starvation in the later 1930s and again in the 1940s.

But then, around 1948, wolves made their way across the frozen lake and have been on the island ever since, setting up the natural drama that would become the longest and most famous predator-prey study ever conducted.

The two species kept each other in check for decades.

Moose numbers hit a low of 385 in 2007, but by last year had climbed to 1,300, according to the Michigan scientists' survey.

Wolf numbers averaged 25, rising at one point to nearly 50. But then in the 1980s, they were struck by parvovirus, a disease carried by dogs brought to the island by visitors, and their number plummeted to 12.

The wolf population, believed to be the descendants of just a few animals, is also inbred. But in 1998, another wolf crossed the ice, an extraordinary event that researchers only discovered later through genetic analysis. He became the alpha wolf, and the influx of genes had a remarkably healthy effect on the population. But they never again got close to a population of 50.

In the winter of 2012, three wolves plunged to their deaths in a long-abandoned mine shaft, dropping their numbers to nine. Between January 2014 and 2015 the number inexplicably dropped to three. Six wolves may have perished or vanished across an ice bridge that formed between the island and Lake Superior's North Shore in winter 2015.

One mating pair left

Now the island has just one mating pair left — a male and a female who are father and daughter. Peterson said they've tried to reproduce, but their one known recent pup was visibly deformed and disappeared very quickly.

Peterson said it's clear from the Park Service report "that they understand the problem — genetic inbreeding and a top carnivore. They are trying to address those two very important issues right out of the gate, and that's great."

Perhaps even more important, scientists said, if the Park Service does introduce new wolves to the island, it will open a new window into understanding wolf behavior by allowing scientists to watch how the newly introduced animals adapt.

"It's such an ideal laboratory," said David Mech, a wolf biologist with the U.S. Geological Service. "This is a great opportunity to learn a great deal."

Josephine Marcotty • 612-673-7394