How the warming climate will turn the Boundary Waters into a barren grassland

Photo illustration of Big Moose Lake's shoreline, after climate change
This photo illustration of Big Moose Lake's shoreline shows what the Boundary Waters could look like as climate changes transform it into as grassland-like region.
Courtesy of David Luke

A few hours' drive north of the Twin Cities will transport you into one of the most unique spots on the continent: a dense, green forest replete with glacial lakes.

The Boundary Waters Canoe Area's isolation and wilderness protections make it so the scent of the pines or rustling of tree branches are most likely to hit your senses before anything else.

This lack of many people and modern worldly distractions are part of what make the BWCA special to visitors.

The Boundary Waters may seem unchangeable and stoic. But humankind's actions over time are far too much for nature.

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If you know where to look, you can already see the Boundary Waters transforming from a lush forest into a desolate grassland.

Warmer temperatures caused by human greenhouse gas emissions are letting maple and oak to start invading the region.

"Later on when the summers get really hot, because it's shallow rocky soil, most of the trees will die and it will end up being savannah," said University of Minnesota forest ecologist Lee Frelich. "So grassland with scattered oak trees."

How Moose Lake trail might look
This photo illustration shows how artist David Luke envisions the Boundary Waters Moose Lake trail might look in a warmer climate.
Courtesy of David Luke

The Boundary Waters' eventual transition to a savannah, as predicted by research from Frelich and others, is a stunning example of how climate change will affect Minnesota if we continue putting carbon into the atmosphere at current rates.

Right now, the prairie-forest border runs from west of St. Cloud southeast to northern Illinois. Under a "business as usual" scenario, Frelich said, that line could move 300 miles northeast and be at Thunder Bay, Ontario, by 2100.

Even if everyone followed the Paris climate pact, it wouldn't stop the change, Frelich said. The deal's primary goal is to hold global temperature increase to 2 degrees Celsius.

Worldwide, "if we actually followed the Paris accords," he said, "the change would be less and I think there would still be some savannahs in the Boundary Waters by the year 2100 but there would also be patches of forest."

President Trump pulled the United States from the climate pact last summer.

The main factor determining if the forest changes into a grassland is the balance between evaporation and rainfall, Frelich said.

The climate is trending warmer and wetter. But the increase in precipitation might be negated by evaporation caused by the higher temps, effectively making the environment drier.

"Literally it could be rainier but drier," Frelich said. "It sounds weird to say that."

There lies the fate of the Boundary Waters: "So if the evaporation, especially during summer, outpaces the increase in precipitation, then it will flip over to a grassland," Frelich said.

Scientists expect many species to go extinct or leave northern Minnesota as the climate changes it into a different habitat.

"Moose don't live on savannahs that are hot in the summer," Frelich said. "Lynx don't live in areas where you don't have six months of snow cover, so they would move out."

Among the trees that would be gone, Frelich said: black spruce, balsam fir, balsam poplar, paper birch, most aspen, white spruce. Potentially jack and red pines. Basically, all the trees that form the region's identity.

Major swaths of savannah and prairie wouldn't be new to Minnesota. There used to be millions of acres of prairie and savannah in Minnesota, just in the southern part of the state.

"That's all been turned into cornfields," Frelich said.

He sees the Boundary Waters situation as an opportunity to restore savannah.

"If the climate gonna go that direction and we're not gonna do anything about it, we might as well make it the best savannah that it can be."

Note: Images in this story are courtesy of visual artist David Luke, whose recent series of photo illustrations show how the Boundary Waters may look as the warming climate changes them.