Elizabeth Harball, E&E reporter
ClimateWire
Although they rarely come into contact with humans, eight gray wolves on an island in Lake Superior are causing a big headache for the National Park Service.
Rising winter temperatures have nearly obliterated the infrequent occurrence of an ice bridge that forms between Michigan’s Isle Royale National Park and the mainland, the only way wolves naturally arrive there. Today, the shrinking wolf pack is so inbred that some fear they will no longer reproduce.
But others say that climate change has not played a role in the wolves’ decline, claiming that despite their isolation, the pack could recover and carry on.
The decision that must be made — whether to introduce more wolves to the island or to allow the pack to possibly die out — is among the first controversial moves National Park Service administrators must make in a world of inevitable yet indirect human-induced threats to wild species.
Even if the agency determines that global warming has affected the wolves, it is not certain that reintroduction will save the current population. Isle Royale Superintendent Phyllis Green must weigh a dizzying array of possible outcomes before she makes a recommendation to National Park Service Director Jonathan Jarvis, which she hopes to do early next year.
Green is keenly aware that the Isle Royale wolves have become symbolic of how wildlife management must be rethought in an era of climate change.
“What confounds this to a degree is that we have a policy … where you let natural processes rule and dictate the changes on the landscape, and we also have a policy that says when people have caused the dramatic change within a park, then you should do what you can to rectify it,” Green said.
“So what do you do when the change that human beings have wrought is so broad-based that on a wolf level, he just knows he’s living, but on our level, we know he’s living in an environment that isn’t quite the way we thought it would be?”
Death by melting?
In the late 1940s, wolves walked to Isle Royale from Ontario via an ice bridge on Lake Superior. There, they found a kind of wolf paradise: untouched wilderness and around 1,000 moose that became their primary food supply.
But the isolation that has kept the wolves safe from human conflict has also taken a toll. Isle Royale scientists have found congenital deformities due to generations of inbreeding in all of the vertebral columns collected since 1994.
Rolf Peterson and John Vucetich of Michigan Technological University, who currently lead a 55-year study of wolves and moose on Isle Royale, worry that their research could end within the decade.
The population in the park is usually around 25 wolves. But during last winter’s annual count, the number dipped to eight, the lowest ever recorded. Although there was some evidence that pups were born this summer, the scientists think the wolves’ genetics have deteriorated to the point that they will soon be unable to reproduce.
Peterson and Vucetich are advocates for a “genetic rescue” of the Isle Royale wolves, outlining their opinion in scholarly journals and even writing a New York Times op-ed.
A key part of their argument hinges on the ice bridge, which aided a natural genetic rescue in 1997, when a male wolf made his way across the ice and met the 14 wolves living there. In less than a decade, the immigrant male was related to every other wolf on the island.
But the next lone wolf might not appear until the pack is dead. According to Vucetich, ice bridges formed in four out of five years during the 1960s, but over the last two decades, they formed in only one out of every 15 years.
“A person would be quite right to say, ‘Well, that’s so indirect,'” Vucetich said. “Absolutely it’s indirect, and that’s kind of the point.
“We’re talking about something that used to be everywhere and now is almost nowhere,” he added. “Climate change is going to take some things away from us that are beautiful and valuable, and there will be nothing we can do about it. … But if that’s the case, it doesn’t mean we should just throw our hands up.”
‘Why is this suddenly necessary?’
Climate change also may have affected Isle Royale’s moose. Higher temperatures could be exacerbating tick outbreaks, which have occurred more frequently since 2001. Also, as summers heat up, the animals spend more time trying to cool off and less time foraging for food, making them less able to survive winter. In 2006, the population plummeted to 400 — a decline that has been linked to above-average temperatures.
But the moose population is now healthy, at nearly 1,000 animals. U.S. Geological Survey biologist David Mech, who has studied the Isle Royale wolves since 1958, argues that the recovery invalidates any claims that warmer summers pose a threat to moose in the future.
Mech has become the go-to counterpoint to Vucetich and Peterson’s call for a genetic rescue and serves on Green’s panel of experts charged with informing her final decision. Mech does think a genetic rescue could work, based on earlier research. But he questions whether the wolves need rescuing.
“The island’s wolves have been inbred since they got there — they were founded by a single female and either one or two males,” Mech said. “At least until the early ’90s, they were highly inbred all that time, and they were still functioning as a normal population. So … why is this suddenly necessary now?”
And although Mech agreed that ice bridges will likely form less frequently with climate change, he is skeptical of their importance, pointing out that natural immigration has happened only once in the wolves’ history.
Bert Frost, associate director of natural resource stewardship and science for the National Park Service, said that it is still unclear to decisionmakers how important a role the ice bridge plays in the debate.
“It is very important,” he said. “But is it absolutely critical? If there was no more immigration onto the island from the mainland by wolves, would wolves go extinct? That’s a question I don’t think we have an answer to.”
Is extinction natural?
In a letter to Green, Emmet Judziewicz, a biology professor at University of Wisconsin, Stevens Point, pointed out that extinction is a common phenomenon on island ecologies.
“In the 10,000 years since glaciers left, there have probably been several [or] many episodes in which wolves, coyotes, foxes, lynx, moose, and caribou have colonized the island, then went extinct after an interval. … That is natural!” he wrote.
Judziewicz added that the less frequent formation of the ice bridge is “a significant caveat,” but in the end, he said, nonintervention is the best course.
Others have also urged Green to “let nature take its course,” including Kevin Proescholdt, conservation director at Wilderness Watch in Minneapolis.
“If humans start transplanting wolves to Isle Royale, we start on a slippery slope that may have no end,” Proescholdt wrote. “Additional wolves may be needed to ‘freshen up’ the gene pool again and again.”
According to Frost, it will not be necessary to change National Park Service policy to introduce new wolves to the island, if that decision is made. But he added that the decision would have “huge implications” for the island’s ecology, and those impacts would influence the Park Service’s choices in the future.
“Adaptive management is a little bit of a cliche these days, but this really is the ultimate experiment if we were to go down that road,” Frost said.
Growing temptation to ‘tinker’
Although Vucetich acknowledges that extinction is common in island ecologies, he argues that the National Park Service must overcome its “institutional inertia,” as he puts it, and preserve one of the last natural havens for a top predator and its prey in the world.
As Green attempts to arrive at a final decision, she notes that the debate over the Isle Royale wolves will be the first of many the National Park Service will face as the planet warms.
“The temptation to push the Parks Service in some ways to start tinkering more is going to be there even stronger as the public sees landscapes change that they don’t want to change,” Green said.
“They can accept the fact that it’s difficult to stop a glacier from melting,” she added. “The question becomes when you have a species dependent upon that glacier, what do you do, how far do you go, and where’s the best place to do it?”