In an unprecedented effort to restore balance between predator and prey, the National Park Service and wildlife officials around the Great Lakes this fall will begin trapping and shipping the first of some two dozen wolves to Isle Royale, where their numbers have dwindled to two.

It's the first time the National Park Service has moved to pre-empt natural dynamics in order to reset the ecological equilibrium in a wilderness area, which by federal designation is to be left largely untouched by human hands. But after three years of review and debate — and a decade of declining wolf numbers — Park Service officials said intervention was the better choice to prevent the overpopulation and eventual starvation of moose, which are eating the island down to bedrock.

"The consequences were trade-offs," said Phyllis Green, superintendent of Isle Royale National Park. "What you could lose in terms of wilderness character, you benefit in terms of keeping an ecosystem resilient and functioning, as it has been for the life of the park."

Wolves, which made their way to Isle Royale over an ice bridge from the mainland in the 1940s, once numbered as high as 50. But inbreeding, disease and a freak accident have knocked their numbers back to the single pair that roam the island today. Warmer winters have also produced fewer ice bridges in recent years, reducing the odds of new wolves wandering in.

The remaining two wolves, a father and daughter, have mated once, but the pup was visibly deformed and didn't survive its first year.

Meanwhile, with so few predators, the moose population has risen to 1,500 this year. That's not the highest on record, but without predators it could double in the next few years, according to an annual wolf and moose survey conducted by researchers from Michigan Technological University. They've been studying the island's predator-prey relationship since the 1950s.

Now the moose are devouring aquatic plants and other vegetation, and face eventual decline through starvation — a cycle that happened on the island before wolves arrived to keep their numbers in check.

"Now is the time to restore wolves and bring balance back to Isle Royale National Park," said Lynn McClure, senior regional director for the National Parks Conservation Association in a statement. "We encourage the National Park Service to act soon and bring more wolves to Isle Royale National Park so we might once again hear their unmistakable howls."

But not everyone agrees. Some wilderness advocacy groups argued that nature should be allowed to take its course.

Kevin Proescholdt, conservation director of Wilderness Watch, said nature has likely already determined that the island is too small to maintain a healthy wolf population, and that rapid turnover of species is characteristic of island ecosystems. Isle Royale, for example, was once home to caribou and lynx. Wolves are relatively new.

"This project is an immense manipulation in a designated wilderness that is supposed to be free of manipulation," he said.

Proescholdt said he also fears that it sets the tone for ways the National Park Service will deal with the significant impact of climate change on species across its system.

"The climate change precedent is ... very important," he said.

Seth Moore, wildlife manager for the Grand Portage Band of Chippewa, said he's disappointed that the Michigan Tech predator and prey study, the longest running research of its kind, will not be completed in its original form. And he pointed out that the park service may be intervening sooner than it needs to because, despite warmer and shorter winters, ice bridges aren't done yet. In the last four years, three have formed between Minnesota and the island, and twice wolves have used them to cross to and from the mainland.

Nonetheless, now that the reintroduction is moving forward, Moore said the tribe is willing and eager to help.

"I'm equally opposed and excited at the same time," he said.

The plan calls for transporting 20 to 30 wolves over the next three to five years. They will be captured from around the Great Lakes to ensure a genetically diverse group of animals — preferably those with expertise in hunting moose.

Mark Romanski, chief of natural resources for Isle Royale National Park, said the park service will work with wildlife officials from Minnesota, Michigan, Ontario and tribal groups to trap and collar wolves, keeping packs intact as much as possible. They will be vaccinated and tested for diseases such as heartworm and parvo virus. To reduce stress, they will be transported immediately by boat or plane to the island. Individuals or packs will be let loose in different places to reduce conflicts once they get there.

The park service will also try to keep the newcomers clear of the two remaining wolves on the island in the hope that they can avoid territorial conflicts that could result in fights and serious injuries or deaths.

Green said the project will cost about $660,000 overall. And it's a one-time shot. She said the park service and outside wolf experts believe the plan will give wolves the best chance of taking firmer hold on the island.

"We will let wolves be wolves for the next 20 years, and possibly longer if the genetics work," said Green.