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The last two surviving wolves on Isle Royale might soon get 20 to 30 new neighbors, after the National Park Service advanced a wolf reintroduction plan Friday for the wilderness island on Lake Superior.

In an effort to intervene in the drastic imbalance between the island's predator wolves and a booming population of vegetation-chomping moose prey, the park service released a final environmental impact statement that favors adding more of the canines over a three-year period.

Under the plan, which could be finalized in a month, officials would start looking for healthy and genetically diverse gray wolves suitable for moving to the island beginning in late autumn.

The wolf reintroduction plan comes amid controversy among conservation groups and others who are split on whether the 1964 Wilderness Act precludes such intervention in federally designated wilderness areas, including 45-mile-long Isle Royale, which sits roughly 20 miles offshore from Grand Portage, Minn. Some groups interpret the law to mean that nature should simply be allowed to take its course.

But Rolf Peterson, a scientist from Michigan Technological University who leads a decades-long research project on the island's wolves and moose, favors population management.

"What counts is getting new paws on the ground and this is a necessary bit of planning that has to precede this," Peterson said. "It's a perfectly fine plan and they should move ahead with it."

The wolf population on Isle Royale has been on the verge of annihilation in recent years, more than a half-century after a few of them first crossed an ice bridge from the mainland in the late 1940s. At their peak, about 50 wolves later roamed the island, but inbreeding, disease and a freak accident contributed to their decline. Warmer winters have also produced fewer ice bridges in recent years, reducing the chances of new wolves wandering in.

The remaining two wolves are father and daughter, and while they mated once, the pup was visibly deformed and didn't survive its first year, Peterson said.

Meanwhile, with so few predators, the moose population has exploded to 1,600 last year. The moose have been devouring aquatic plants and other vegetation and face eventual decline through starvation, a cycle that has happened on the island before.

The island's ecosystem became a rich site for research on interaction between species.

In December 2016, the park service recommended quickly transplanting a significant number of wolves to the island as the best way to re-establish a healthy population there.

But Kevin Proescholdt, conservation director of Wilderness Watch, said the Wilderness Act "really demands that humans not manipulate these wilderness areas."

Proescholdt said he believes the moose population would find a new equilibrium.

"Moose lived and survived and thrived on Isle Royale for several decades, at least, before wolves ever arrived," he said. Once an area is designated as wilderness, he added, "we humans have to have the humility and restraint to allow those areas to exist and evolve and thrive on their own without imposing human desires on the landscape."

Advocates for reintroducing wolves argue that humans have already had an impact on what's happening on the island.

"The fact that we only have two wolves left is really largely human-related," said Christine Goepfert, Midwest program manager for the National Parks Conservation Association.

In addition to the effects of climate change, someone brought a dog to the island in the 1980s that introduced a canine virus, and when a dozen wolves roamed the island in 2012, three fell to their deaths in an old mine shaft, Goepfert pointed out.

The park service outlined its preferred plan in the environmental impact statement:

Within three years, wolves will be brought to the island in multiple, separate shipments, maximizing diversity in their genetics, age and sex. Supplemental transplants would be added as needed through the third year. Wolf packs or pairs with pups could be released as groups across the island. Unrelated wolves would be dispersed to minimize conflict.

By the third year, if disease or other unforeseen events cuts the number of wolves to fewer than a dozen, including fewer than three breeding-age females, the park could bring in more wolves for two more years. No additional wolves would be introduced after five years, however.

Park Superintendent Phyllis Green said the number and timing of the wolf restoration project would depend on finding and capturing wild wolves from other areas surrounding Lake Superior.

"Wolves aren't all that easy to trap and catch. They get very smart very fast," Green said. "I can't give you a number. If I gave you one the wolves would decide otherwise."

Under the plan, officials would introduce collared wolves to the island starting in late fall or early winter. Wolves typically breed midwinter and have pups in the spring.

"That's part of the reason to collar, because we'll have a better sense of what's going on with them," Green said. "We'll know if they're still loners or whether they've found a mate."

A 30-day waiting period will give groups time to bring new information to the debate. Proescholdt said Wilderness Watch will analyze the lengthy environment impact statement before determining what to do.

Goepfert said she would be surprised if significant new information comes forward. The park service has thoroughly analyzed the situation, she said.

The environmental impact statement can be found online at A few hard copies are also available at public libraries in Duluth, Superior, Wis., and Houghton and Marquette, Mich.

Pam Louwagie • 612-673-7102