Studies show that the upper reaches of the Great Lakes are at high risk for wildfires, and that large, hot fires can harm lakes in the region’s remote watersheds.
Reason: Plants burn in fire. Scorching high temperatures make soils hydrophobic, causing erosion and increasing runoff into lakes. There are no longer any plants to filter the sediment that seeps into waterways. One area of concern is northern Minnesota, where dry and windy conditions are causing fires.
In early June, lightning sparked three wildfires in the Boundary Waters Canoe Area Preserve, leading to a ban on campfires. Two more fires recently broke out in Ely, prompting emergency evacuations. The Flanders Fire, which broke out east of Breezy Point in mid-May, scorched more than 1,700 acres in about a week.
Teresa Froberg said the fires are evidence that increased fire danger is becoming the new norm in the region. She is the Ely Fireshed coordinator for Dovetail Partners, an environmental think tank that works with the Superior National Forest.
“If you look at the wildfire risk maps for northern Minnesota, northern Wisconsin and northern Michigan, the wildfire risk is similar to the West,” Froberg said. “The same level of risk factors exists, and it could be intensified.”
Of course, the risks aren’t limited to the Northwoods. Wildfire experts are predicting a tough fire season across the country this year as drought grips much of the country. As of mid-June, the National Interagency Coordination Center reported that wildfires had burned more than 2.5 million acres across the United States, nearly double the 10-year average.
The causes have been gradually accumulating for more than a century. Climate change is the main culprit: warmer summers, shorter winters, and unexpectedly dry and windy days. That and over a century of federal fire policy. Fuel that has accumulated in forests over decades, such as fallen trees and thick undergrowth, fuels the blazes, causing wildfires to spread to catastrophic proportions.
Fighting wildfires costs a lot of money. Wildfires in northern Minnesota required $8.7 million in emergency response from National Guard and fire personnel last year alone.
Chris Filstrup is an expert on how wildfires are impacting remote lakes in northern Minnesota.
Five years ago, when the Greenwood Fire burned more than 26,800 acres in northeastern Minnesota, lake scientists became obsessed with what that summer’s largest and most destructive wildfire was doing to the thousands of pristine lakes in its warpath across the Superior National Forest.
Filstrup thoroughly reviewed previous studies examining how fires affect watersheds. There were few studies, and those he found overwhelmingly focused on the western half of the United States.
“This issue needs to be studied in the Midwest because differences in vegetation, landscape, hydrology, and weather patterns are all likely to influence lake response to fire,” Filstrup said. “We have a very different system here.”
Sam Reid agrees. Reid is the climate conservation manager for the advocacy group Friends of the Boundary Waters and reviews all climate impact studies in the greater Quetico-Superior ecosystem. Fire has been largely excluded from that research.
“The relationship between fire and freshwater needs more attention, both from a research perspective and from a policy perspective,” Reid said. “We need to think about how that will affect our wonderful freshwater resources.”
Filstrup is one of the leaders in filling that knowledge gap.
Philstrup, along with a team of researchers, received fast-track funding from the National Science Foundation to study the effects of wildfires on inland lakes in the Upper Midwest. When they began surveying the Superior National Forest watershed the following May after the fires, much of the landscape was still scorched. Mr. Philstrup said it was like stepping onto another planet. The lake within the burn site was and still is the color of sweet tea, with almost no vegetation on its shores. Before the fire, it was clear, home to a variety of plants, and largely unaffected by pollution.
In the years since the Greenwood Fire, Philstrup and the lab he directs at the University of Minnesota have continued to monitor the lake every summer.
“You’ll see the landscape rejuvenate. You’ll see the soil start to stabilize again. You’ll see the vegetation start to regrow. It’s really amazing,” Filstrup said. “But a lot of these lakes haven’t really recovered yet when it comes to water quality.”
In their initial study, Filstrup and other scientists sampled lakes that were charred by the fire and some of the lakes outside the burn scar. The researchers found that lakes in burned areas of forests had higher concentrations of phosphorus, nitrogen, and carbon than undisturbed lakes. The water was even cloudier and more acidic. All this means poor water quality.
Although the researchers did not see an increase in algae growth in the lakes they studied, increased nutrients can encourage algae growth, leading to algal blooms, a rapid overgrowth of organisms found in areas such as Green Bay and the western Lake Erie basin.
That green sludge can strip large amounts of oxygen from the water as it dies, blocking sunlight to the plant communities on the lake bed that normally bind nutrients. Without that plant, nitrogen and phosphorus could stay in the water and encourage algae blooms, and Filstrap said lower oxygen levels could kill fish.
Additionally, water quality can be at risk when fighting wildfires. Increasing fire intensity and frequency means fire agencies are using more flame retardants to put out fires. Red plumes dumped from planes can contaminate waterways with heavy metals, fertilizers, and chemicals such as phosphorus.
“My concern was that really valuable and cherished ecosystems like the Boundary Waters Canoe Area Wilderness and the Superior National Forest would start to turn into lakes, which are common in highly urbanized areas, highly agricultural areas, or areas with very high human pressure within their watersheds,” Filstrup said.
When Filstrup first started analyzing these lakes, he said there was some debate about how much fires actually affected water quality. Some said this was a minor disruption and the lake would recover on its own by next year.
“Five years after the fire, these lakes still exhibit similar characteristics: high nutrient content, brownish color, murky water, and low clarity,” Filstrup said. “These are lasting effects and results that are shocking to a lot of people because we thought this was not something we necessarily had to deal with.”
It’s not just the lake that will be affected.
Ecosystem degradation can have a dramatic impact on Minnesota’s economy. Outdoor recreation in the Northeast region alone generated more than $1.3 billion in economic output in 2024.
“If you start changing the water quality in these ecosystems, people won’t travel as far,” says Filstrup. “If people don’t travel to get there, they won’t spend money along the way.”
Part 2 reports on how Minnesotans are working to control fires to protect watersheds.
thisarticleteeth,Circle of Blue First published inCreative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.
