There are just three wolves remaining on Isle Royale, a Michigan island in Lake Superior, and that's a problem for the ecosystem, as the moose population is surging and their grazing is threatening the island's vegetation. But it's also a sign of the climate change-related impacts the nation is set to face.
Researchers from Michigan Technological University gave the tally of the wolf numbers earlier this year, noting that it was a big drop from the nine they counted the previous year.
But the number has been on a steady decline. Michigan Tech professors John Vucetich and Rolf Peterson, who lead the study, write in their report (pdf):
These changes are part of a longer trend. Since 2009 the wolf population has dropped by nearly 90%. As a result of very low wolf abundance, each of the past four years has seen unprecedented low rates of predation. In response, the moose population has been growing at a mean rate of 22% per year for each of the past four years.
With such a small population, inbreeding is weakening the wolves that do remain. There are two adults and a pup now, and the researchers said that the pup appears unhealthy.
But why plummeting numbers on Isle Royale?
As Peterson previously stated: "The human imprint is written all over the dynamics of this wolf population in recent decades." And the National Parks Conservation Association explains
that the route that brought wolves to the island – naturally occurring ice bridges that form in winter from the mainland – do not form as often because of the warming climate. When ice bridges do form, it is hard to predict whether wolves will use the bridge to arrive and stay on the island or to leave; both scenarios occurred the last two winters. Coupled with a period of disease and other factors, the wolves on the island are now inbred, which negatively impacts the health of the pack and their ability to breed.
Vucetich told MLive last week that the best plan is to import wolves to the island "as soon as possible."
The "frequency of ice bridges is expected to continue to decline because of climate warming," Vucetich said.
"That's why this issue is really much bigger than just being about Isle Royale. It's an issue that will set precedent on how the National Park Service will make decisions about climate change," he said.