Warm winter could mean ecological ripple effects on Minnesota forests, wildlife

Partially frozen lake along sidewalk and grass
There was no snow on the ground -- and rapidly melting ice on the lake -- as temperatures climbed into the 50s on Wednesday at Lake of the Isles in Minneapolis. Cities across Minnesota set record highs for Jan. 31.
Estelle Timar-Wilcox | MPR News

Forests and wildlife are dealing with a winter whiplash.

Last winter produced enormous amounts of snow and an infamous polar vortex, even as 2023 in its entirety was one of the hottest years on record for Minnesota and the globe.

While there have been periods of intense cold this winter, there has been little snow. It all has experts wondering about the longer term impact.

“If this winter is a one-off, and then next winter we have lots of snow, the effects can be different than if we have three of these kinds of winters back to back,” said John Erb, wolf research scientist with the Minnesota Department of Natural Resources.

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John Erb
Department of Natural Resources wolf research biologist John Erb inspects the frozen carcass of a wolf in a DNR laboratory in Grand Rapids.
Tom Robertson | MPR News 2012

Erb monitors furry critters from weasels to wolves.

“Last winter definitely had negative effects on one set of wildlife species and this winter may have negative effects on a different set of wildlife species.”

In December, the Superior National Forest posted a pair of pictures on Facebook depicting a fox with a snow-white hare in its mouth, set against a dark background.

“Poor hare got a little too white for the mostly brown forest ecosystem,” the post reads. “The fox won that chase for a fine winter solstice eve meal.”

“We always have to be careful to not over-interpret any individual photo,” Erb said. “Obviously, foxes and fishers and bobcats catch plenty of hares in deep snow winters where everything’s white … But it does provide a striking image when you see a fox carrying a snowball in a black and green background.”

Research shows that color mismatch, said Erb, does negatively affect the survival rate of snowshoe hares. Whether there’s a lasting effect on hares and other color-changing species like weasels and how much natural selection will play a role remains to be seen.

Ripple effect

Cheron Ferland, forest wildlife biologist for the Superior National Forest, is headquartered in Duluth but works across the 3 million acres of national forest spanning northern Minnesota. She says the warmer temperatures are starting to have a visible ripple effect on trees.

A wildland firefighter prepares to load up a canoe
A wildland firefighter prepares to load a canoe to battle the Spice Lake Fire in the Boundary Waters Canoe Area Wilderness on June 16, 2023.
Courtesy of U.S. Forest Service

“Sometimes they’ll show up in events such as insect and disease outbreaks, more frequent or more intense wildfires,” Ferland said.

Some of northernmost Minnesota is host to boreal forests, which also cover Russia, northern Europe, Canada and Alaska. These forests are home to lots of wildlife species — including endangered animals such as the Canada lynx — but also make up the world’s largest terrestrial carbon storage system. If those forests recede or shrink, that could result in species loss and more carbon dioxide in the atmosphere.

Ferland says the U.S. Forest Service and its partners including the DNR are trying to make boreal forests more resilient to climate change. One method is thinning forests.

“That means that the remaining trees have more of those limited resources available, so hopefully they can be a little more robust to things like wildfires to insect and disease outbreaks — they’re less stressed in those conditions,” Ferland said.

Mitigation also includes reducing burnable materials such as understory and tree saplings to prevent wildfires, as well as prescribed burns to promote new growth and control parasites such as ticks. All these efforts, says Ferland, can improve habitats for wildlife and watersheds.

Superior National Forest is taking part in a pilot program called “Assisted Migration.” The process plants tree seedlings from seed sources one zone south of the established climate.

“We’re actually trying to sort of transplant genetically more adapted species in our forest restoration efforts with the prediction, again, that the climate is changing … and maybe those trees would be more adapted to that future climate,” Ferland said.

Delayed surveys

The critical process of species monitoring is also challenged by the changing climate. Morgan Swingen, wildlife biologist for the 1854 Treaty Authority, says last year’s record snowfall in Duluth delayed grouse surveys due to slow melting. Conversely this year, the lack of snow has delayed winter track and moose surveys by several weeks.

As part of the state moose survey, observers including Swingen with the 1854 Treaty Authority go up in a helicopter typically during the first week of January with a benchmark of eight inches of snow on the ground.

“The snow just makes it easier to see the moose. If there’s a nice white background and the snow’s covering other dark objects like rocks and stumps, it’s just easier,” Swingen said.

This year, the team couldn’t survey moose until Jan. 17. And with poor flying weather, it has completed just 31 of 53 plots as of Jan. 31 but hopes to finish in the coming days.

The 1854 Treaty Authority is an intertribal natural resources agency, working with the Grand Portage Band of Lake Superior Chippewa and the Bois Forte Band of Chippewa. Swingen says it’s analogous to the DNR for tribal members and works with other land management agencies to collaboratively manage natural resources in northern Minnesota.

Band members can hunt, fish and gather off-reservation without a state license. Instead, they get an ID card from the Authority, or obtain a big game license. However, they can only exercise those treaty rights within set boundaries.

“If animal ranges are shifting, the boundary is not changing of the ceded territory. And so that’s a challenge,” Swingen said. “If we’re losing species because of ranges due to climate change, they’re just not available anymore for band members. So that is definitely a concern for us.”

A screen grab of a video of a wild animal.
A video screen grab of a moose at the Voyageurs National Park.
Courtesy of Voyageurs Wolf Project

Plans and strategies

The agency is working on a climate change adaptation plan, including mitigation strategies.

“That might mean eventually switching our idea of management to focus on species that are going to do better with changing climate,” Swingen said, underlining the agency is doing all it can to keep moose. “But we recognize that, eventually, that just might not be a viable option anymore. And we might have to in the future shift or strategies to focus on other species that will do better, like deer or even elk.”

It’s not all bad news. Erb says recent modeling shows climate change isn’t having a huge effect on wolves in Minnesota. Deer may also benefit, indirectly helping wolves. But he’s hesitant to trust that modeling innately or look too far into the future.

“There’s a whole lot of complicated interactions here that just makes it hard to hard to predict,” Erb said. “We tend to like to focus on individual species, but all of this interacts with weather and climate change, making it difficult to really make big grand predictions.”

The time, Erb and Ferland agree, is now to focus on mitigation, continued monitoring and public education about climate change. Ferland wants to remain on the cutting edge of science, be progressive and consider adapting those monitoring strategies. Erb is also hopeful that a statewide citizen science-based camera survey for wildlife is in the future — similar to Snapshot Wisconsin. It has the added benefit of freeing up DNR staff. But all that relies on private citizens stepping up as volunteers.

“Hopefully a path for success would be just continuing to engage on so many levels,” Ferland said. “We’re the federal government, we have our state partners, we have nongovernment organization partners, we have the public, we have counties, we have our tribes bands. And I think bringing those people in collectively … will bring more ideas.”