Beaver expansion into Alaska’s Arctic tundra presents problems for people, but also opportunities

A wide-ranging research program led by a UAF ecologist is tracking the way beavers’ northward movement affects permafrost, water quality, fish, birds and communities.

When Cyrus Harris first saw a beaver during a camping trip in the tundra territory in the far northwest of Alaska in 1988, the discovery created a stir in his hometown of Kotzebue.

“That made big news then,” he said. He and his companions removed the beaver, which was near Cape Krusenstern just north of the Bering Strait, above the Arctic Circle and, until recently, far north of the Alaska tree line. When they heard about the beaver, Harris said, local Inupiat elders issued a warning that more would appear: “They’re coming, and that’s what’s going to be happening.”

The presence of beavers in the Arctic landscape around Kotzebue is no longer news. The beaver population, previously not an Arctic feature, has exploded in that region — and quickly transformed the landscape.

That transformation was summarized at a workshop in late February at the University of Alaska Fairbanks, where scientists and community residents shared research findings and observations.

In a 100-square-kilometer area near Kotzebue — just under 40 square miles — the number of beaver dams jumped from two in 2002 to 98 in 2019, according to UAF research presented at the beginning of the three-day workshop. The workshop was part of a National Science Foundation-funded program called the Arctic Beaver Observation Network, or A-BON. On a wider area of the Baldwin Peninsula, the number went from 94 in 2010 to 409 in 2019. Across a wider area of Arctic Northwest Alaska, their presence went from nothing in the 1950s, as shown in aerial photos, to more than 11,300 beaver ponds identified through satellite imagery by 2019, according to the UAF scientists. The presence of beaver ponds in that region more than doubled between 2004 and 2017, the scientists found.

Satellite images that have tracked beaver expansion over time clearly show not just the number of dams but their drastic impacts, said Ken Tape, the UAF ecology professor who is leading the A-BON program. He pointed to one site as an example. “It basically changes from a little stream into a sprawling wetlands,” he said.

The proliferation of beavers is attributed to the northward spread of woody plants that they eat and use for their dams and lodges.

While climate change has enabled beavers to live farther north, the animals are exacerbating the effects of Arctic climate change. Through their dam and lodge engineering, they are inundating some areas with water, speeding up permafrost thaw. Elsewhere, they are drying out areas.


Effects of climate change were already underway on the tundra landscape, with permafrost warming and lakes expanding or draining and woody shrubs growing bigger and farther north, but those were relatively gradual – until the new arrivals began engineering the landscape, Tape said.

“All of a sudden, the beaver shows up. It’s like, wham, just night and day, completely different,” he said.

‘Tundra Be Dammed’

Tape, who got into beaver studies when he and UAF permafrost expert Ben Jones were tracking climate change effects on the tundra, has now become a leading authority on the animals’ northward expansion. A famous study that he led, published in 2018, described the phenomenon in Northwest Alaska and bore a catchy title: Tundra Be Dammed.

Beavers can be as disruptive to the tundra ecosystem as wildfires are, Tape and his colleagues have concluded.

Beaver presence in Arctic Alaska largely stops at the Continental Divide in the Brooks Range, leaving the North Slope largely beaver-free — for now. There are some exceptions discovered recently: a beaver pond complex that was found on the Kongakut River, which flows through the Arctic National Wildlife Refuge near the Canadian border, and some chew marks and tracks left by beavers on the Killik River, which flows from a point in Gates of the Arctic National Park and Preserve into the bigger Colville River.

But that North Slope situation is expected to change, Tape said. Projections are that if the climate continues its current warming trend and shrubs continue spreading north, beavers will follow, moving down the northern side of the divide to establish themselves across the entire North Slope by century’s end, he said. “They’re poised to swim downstream,” he said.

For many residents, their animals’ new presence is a serious problem.

“We’re surrounded by beaver lodges,” said Ralph Ramoth of Selawik, an Inupiat village about 90 miles east of Kotzebue.

Beaver structures have blocked access to traditional areas for duck hunting and berry-picking, and they’ve created barriers on creeks where fish used to spawn, Ramoth said. They have affected water quality as well, he said.

“When I was young, you used to be able to drink the water out of the river. Nowadays you don’t,” he said. Those who try, he said, get stomach distress. “People call it ‘beaver fever,’” he said, referring to the unpleasant intestinal infection caused by the parasite giardia.

Beaver sins

There is a long litany of observed or suspected beaver sins in their new Arctic territory that were discussed at the workshop.

Their dams can be insurmountable barriers to fish, particularly to the whitefish that are important subsistence foods but not particularly strong swimmers. That affects people who depend on those fish for their diets — and reverberates through the food web in ways that might seem surprising. Belugas in Arctic waters, for example, depend on whitefish populations that might be harmed by new beaver presence.


As articulated by Ramoth and by residents of Canada’s Northwest Territories who attended the workshop, beaver structures can impede travel, blocking boat routes long used in the summer and turning once-dependable winter ice-travel routes into danger zones.

Deteriorated water quality is a widespread concern; Harris noted that beaver complexes are plentiful just upstream of the reservoir that is the drinking-water source for Kotzebue.

There are potentially longer-term and wider-ranging effects as well.

By speeding permafrost thaw, they are hastening the release of carbon into the atmosphere, scientists said. That is because permafrost holds organic material accumulated over thousands of years that, through freeze, is resistant to decomposition, said Michael Loranty, an associate professor of geography at Colgate University in New York.

“But when you start thawing that out, it starts decomposing,” he said at the workshop. “And if, you know, you’re kind of putting all that permafrost carbon in the bank slowly over tens of thousands of years and then you thaw it out very quickly, it’s kind of a big pulse, potentially, into the atmosphere.”

There is evidence that such pulses are already underway. Work led by UAF researcher Jason Clark detected hotspots of methane emissions from Northwest Alaska beaver ponds. Methane is a particularly potent greenhouse gas and is known to be produced from permafrost thaw. The discovery of “is an example of a new disturbance regime, wrought by an ecosystem engineer, accelerating the effects of climate change in the Arctic,” said the 2023 study, which was coauthored by Tape, Jones and others at UAF, along with scientists from the National Park Service and the California Institute of Technology.


There are related effects. Though studies are preliminary, there is evidence that beavers are contributing to higher mercury levels in the water systems — and thus in fish populations. Permafrost thaw releases natural elemental mercury that is stored in frozen peat, and beavers stimulate that thaw. Additionally, the beavers may be inadvertently helping to convert that elemental mercury into methylmercury, the form that is most dangerous to people and animals.

“Beavers bring a lot of wood to streams,” Matthew Mervyn, a graduate student who is studying the question in Canada’s Northwest Territories, said at the workshop. “Since the water slows down, it introduces more bacteria to methyl-ize the mercury.”

Mervyn, with Canada’s Wilfrid Laurier University, is part of a Canadian-British program called Beavers and Socio-ecological Resilience in Inuit Nunangat, or BARIN. It focuses on the Arctic region of the Northwest Territories. There, Indigenous hunters were the first to document colonization of the Beaufort Sea coast by beavers, with the animals spotted in 2008 and 2009.

The benefits of beavers

But there is another side of beavers in the Arctic.

“If I had a T-shirt, it would say, ‘I love beavers.’ I love them. They’re the best things in the world,” Lance Kramer, one of only about three Kotzebue residents who regularly trap beavers, said at the workshop.

He acknowledged that many of his Kotzebue neighbors greeted the news of beaver presence with the expression “Aiee,” a somewhat untranslatable Inupiaq expression of alarm and annoyance.


Kramer, in contrast, has taken advantage of the new arrivals. When he traps a fat beaver, he can use it for meat. The meat from skinny beavers goes to his dog, he said. He is making money selling the pelts. He has created his own detailed map of beaver lodges in the area, with names like “Faceplant Place Lodge” “About Time Lodge” and “Mad Snowman Lake Lodge,” the latter so named because his son became so annoyed about waiting for him to show up there that he built a snowman with an angry face.

He has even taken his love of beavers to show business, albeit subtly. He was an actor in the Alaska-based HBO series “True Detective: The Night Country,” and in a tense scene where his character brandishes a gun at law enforcement officers, he is wearing a beaver hat made by his mother-in-law.

Kramer brought up other beaver benefits. Aside from supplying meat, fur and income, beavers make it easier for him to hunt or trap other animals that gather at the structures, like wolverines and minks. “You can get everything at a beaver lodge. It’s a one-stop shop,” he said.

Evidence, mostly from outside of Alaska, shows that beaver lodges and dams can create habitat for other species, from insects to birds to predators. Research into that is continuing through the A-BON program; one project, explained by UAF graduate student Sebastian Zavoico, is using sound recorders to track bird diversity at recently established Alaska beaver sites.

While many Arctic residents are leery about the impacts of beaver dams and lodges to fish, evidence gathered to date paints a mixed picture.

In the Lower 48, where many riparian systems have been damaged by development, beavers are often considered restorers. Numerous studies there have found that beaver colonization is good for fish.

In Alaska, where study of the beaver-fish relationship is just starting, the evidence is that the animals have been positive influences in some spots and negative in others, according to information presented at the conference by UAF graduate student William Samuel. He has been tracking the relationship between beavers and Arctic grayling — and the relationship between beavers, grayling and wildfire. Within Interior Alaska, he found strong evidence that beaver densities increased in burned areas and that the combination of beavers and fires could be bad for grayling.

But the presence of beavers can make forested areas resistant to fires, too. Dammed areas can serve as fire breaks and help speed ecosystem recovery after wildfires, research in the Lower 48 has found.


The “beaver fever” name notwithstanding, beavers may not be as responsible as people think for giardia infections, said Glynnis Hood, an environmental science professor at the University of Alberta. “Beavers always get the rap, but humans carry giardia, too, and they don’t always clean up after themselves,” she said at the workshop.

Entrenched in the tundra landscape?

Future action on beavers might address both negative and positive aspects, suggested Andy Bassich of Eagle, an Interior community near the Canadian border.

“I don’t want, really, to use the word ‘infestation,’ but in some people’s minds that’s the appropriate word,” he said. In his region, where beavers have long been established, the animals have become a good source of food that substitutes for traditional food sources like salmon that are in short supply, he said.

If people want to get rid of “nuisance beavers” that might be blocking fish passage or creating other problems, perhaps there should be some kind of combined economic and cultural program that trains young people to hunt and trap them, process them, tan the hides, providing both meat and income, Bassich said.

Whatever Alaskans and Arctic residents decide to do about them, beavers may be in the far north for good.

That was a lesson imparted by Lennie Emaghok, an elder from Tuktoyaktuk, a Northwest Territories Inupiat community on the Beaufort Sea coast.

He recounted how in 2020, along a relatively short stretch of creek, he and others found 10 beaver structures and quickly removed most of them, including one that was particularly towering.

“When we returned three days later, the dam was built back, as if we had never touched it,” he said.

Hood summarized the power of the wood-chomping rodent. “Never underestimate a beaver,” she said.

Originally published by the Alaska Beacon, an independent, nonpartisan news organization that covers Alaska state government.