Until a few years ago, a small stream meandered down a long valley flanked by sheer ridges in Umiujaq, a subarctic village in northern Quebec. The waterway had pretty much hewed to that course since the earth’s crust rebounded after the last ice age.
Newcomers from the south, though, had other ideas.
A crew of bucktoothed, paddle-tailed beavers has erected five dams, the most impressive being as tall as a city bus and even longer. The sound of cascading water is heard half a mile away. Toads paddle inside the large ponds that now pockmark the valley, beneficiaries of the hydrological attenuation engineered by the recent arrivals.
“Here, you really feel the beaver’s power,” said Najat Bhiry, a geographer who had recently spent two hours thrashing through dense thickets and battling thousands of airborne insects to reach the most ostentatious dam, where a single beaver popped out of the water for a split second.
Catching her breath behind the barrier, her words nearly drowned out by the roar of the crashing water, Professor Bhiry added, “A little animal like the one we just saw, swimming peacefully — and look what it’s done!”
Beavers are migrating north — way north. The furry, pyriform rodents are waddling across boreal forests and torpedoing through both freshwater and saltwater in their push north as Canada’s Arctic grows less frigid. They have established themselves in subarctic regions that straddle the tree line, like Umiujaq. The most intrepid are testing the waters hundreds of miles above the Arctic Circle, in hamlets like Tuktoyaktuk, where beavers have been spotted lolling around in the harbor this summer.
Canada’s national symbol, beavers have finally hit land inhabited by the Canadians who perhaps know them the least: the Inuit. Traditional residents of Canada’s treeless, northern reaches, the Inuit had little, if any, interaction with them until now. Humans are considered beavers’ apex predator. Not the Inuit, though.
“We’re not really interested in beavers,” Johnassie Crow, 40, said, adding that he had tried, unsuccessfully, to trap the animal. “I still have a lot of learning to do. But, really, we Inuit aren’t interested in trapping them.”
Looking down at the valley, Mr. Crow said he found the beavers’ behavior disconcerting. As their numbers increased, they had dammed a river used by Arctic char, a troutlike fish that is a delicacy in the Far North. Mr. Crow belonged to a dragnet that had repeatedly torn down the barricade, only to see it rebuilt.
“Arctic char, we love,” he added.
Castorologists say that the beavers’ northward advance is a new chapter in the animal’s long and complicated history with Canada. Long prized by the First Nations, beavers and the trade in their pelts fueled the exploration and building of the country. The most famous fur trader, Hudson’s Bay Company, was for a long time North America’s oldest company. It celebrated its 355th anniversary before finally going bankrupt last year.
The beaver has been embossed on the Canadian nickel since 1937 and became an official symbol of Canada in 1975. In Canadian culture, it is a cute fur ball summoned to sell items as diverse as Canadian clothing, by brands like Roots, and national parks; it makes more than regular appearances in children’s books and cartoons.
The reality is that the beaver is a formidable beast that has consistently outwitted predators. In the late 19th century, beavers bounced back from near-extinction after three centuries of the fur trade.
“They’re the second-largest rodent in the world after the capybara,” said Glynnis Hood, an emerita professor of environmental biology and ecology at the University of Alberta and the author of “The Beaver Manifesto.”
Across North America, from Alaska to Quebec, higher temperatures, the growth of shrubs across the tundra, shorter winters, earlier snowmelts and other changes driven by climate change are fueling the castorid migration north, Dr. Hood said.
No longer strangers in the subarctic, some beavers are creeping higher into the Arctic proper.
In Tuktoyaktuk, a hamlet that faces the Arctic Ocean in western Canada some 200 miles north of the Arctic Circle, the rodents with orange incisors have wrenched two-foot-tall willows into place to dam the surrounding creeks — which are used by spawning whitefish. In the past two summers, beavers have even surfaced in the hamlet, carving paths across the harbor’s brackish water.
“They’re either looking for a creek to dam up or a mate to dam up a creek with,” said William Dillon, a resident who has led efforts to measure the thawing permafrost in Tuktoyaktuk.
Canada’s beloved icon has left most Inuit in Tuktoyaktuk entirely cold, Mr. Dillon said.
“It’s just an awful big mouse to us,” he added.
To be sure, beavers aren’t the only transplants heading north. Across Canada’s Arctic, people report seeing new species of birds and sea mammals in their midst. On land, moose are branching out of their traditional range, following the northward spread of ever-taller shrubs across the tundra, a phenomenon scientists call the region’s “shrubification.”
But no southerner has had a greater impact on the north than the beaver. By building dams and ponds, beavers are rewiring Arctic hydrology, scientists say. Their ponds accelerate the permafrost’s thaw, leading to new wetlands and more vegetation — not to mention the release of methane, a highly potent greenhouse gas.
“Beavers are called ecosystem engineers,” said Dr. Hood, the expert in castorology. “Beavers are just fundamentally driven to modify the environment to their advantage. There are several mammals that can do that. Humans and beavers sort of compete, though humans have probably won.”
In Umiujaq, an Inuit village of 550 people facing Hudson’s Bay eastern shore, beavers are often sighted swimming up the coast in the bay’s brackish waters.
Professor Bhiry, the geographer, who is a professor at Laval University’s Center for Northern Studies in Quebec City, has visited Umiujaq every summer for the past three years to record the beaver-led transformation of Umiujaq’s valley. A decade ago, before beavers, only a 40-inch-wide stream ran down the valley, she recalled.
On a visit in July, Professor Bhiry and two of her students spent hours in the brush to get a close-up view of the beaver dams and lodges. They flew drones to get the big picture of the ever-taller and denser willows and birches that were replacing the lichen and other vegetation typical of the tundra. Submerged in the beaver ponds, native plants could be seen browning and dying.
“Here, beavers found what they were looking for,” Professor Bhiry said. “It’s peaceful. There’s a lot of water. There’s a lot of food, and no competition for it.”
The beavers’ impact didn’t stop there.
“Beavers change their environment so much that they even end up creating habitats that are favorable to other animal species — small birds like warblers that are able to nest in the bushes,” said Isabeau Pratte, a biologist for the Kativik Regional government, which oversees the Inuit communities in northern Quebec.
A study by helicopter of 270 miles of waterways in the Umiujaq region had tallied 71 beaver habitats, each with one or more dams, Ms. Pratte said.
But one spot in particular — dams on a river where Arctic char go to spawn and Inuit to fish — had angered the locals.
“Salmon are strong — they can jump high,” said Eddie Kumarluk, the leader of a local wildlife association behind efforts to dismantle the dams and track the beaver population. “But Arctic char are less strong and have problems jumping over the beaver dams.”
Catches had dwindled in recent years, he said, adding, “Eventually, the fish could move elsewhere.”
Mathilde Lapointe St-Pierre, a biologist at Makivvik, a political organization for Inuit in northern Quebec, said that salmon had evolved while rubbing shoulders with beavers.
“But for the Arctic char, beavers are new,” she said. “So it’s less of a fighter.”
All Inuit communities with beavers were worried about the loss of Arctic char and increasing food insecurity, Ms. St-Pierre said, though those concerns had yet to alter time-tested hunting habits.
Late one evening, half a dozen beavers lingered around their lodges in the Umiujaq valley’s ponds. Peering down, Mr. Kumarluk said that he had tried to curb their population by urging his fellow Inuit — otherwise excellent hunters — to focus on beavers.
He had even invited Cree First Nation hunters from the south — for whom beavers are a source of food, clothing and spirituality — to teach locals how to trap the relentless rodent.
“I bought maybe 40 traps,” he said. “I even offered them for free. But they’re just sitting in our storage.”
