We’re pleased to present this informative piece by Chance Lasher, a writing studies major at the University of Minnesota Duluth. He wrote it for an Outdoor and Environmental Journalism class. His instructor, John Hatcher, suggested it might be a good fit for Agate, and he was right. It has long been a goal at Agate to encourage young peoples’ writing efforts, and here is a good example.
Compared to last year, Minnesota’s spring wildfire season has been a lamb.
During March and April of 2021, Minnesota experienced 819 fires. So far, 2022 has produced 60 fires in that same time frame. But even with a milder start to this year’s wildfire season, smoke events are likely this year and for the foreseeable future.
As a result of 100 years of fire suppression in many areas and increasingly dry fuels, the past 40 years have seen the wildfire burn area increase by roughly four times in the United States.
Minnesota’s 2021 fire season was a reminder that fires can hit close to home. Late summer saw record drought, severe wildfires, and prolonged smoke events across the state.
Wildfires, no matter where they burn, belch smoke over state and even national borders, affecting large geographic areas. Places with usually pristine air quality are at the mercy of out-of-state smoke.
Climate change is bringing warmer and wetter weather to the upper Midwest. In the last 125 years, Minnesota’s average state temperature has risen 3 degrees Fahrenheit, and annual precipitation has increased by 3.4 inches.
While the relationship of temperatures to increasing wildfires is straightforward, an increase in average moisture might seem counterintuitive to wildfire growth. Kenneth Blumenfeld, senior climatologist at the Minnesota Department of Natural Resources, said the relationship isn’t so simple. Trees in Minnesota are acclimated to a specific temperature and moisture level. As the climate gets warmer and wetter, these trees fall out of their comfort zone. This means they become prone to disease and insect infestation. Ultimately, they weaken and/or die — both of which make them fuel for potential wildfires. “As long as we are in conditions that weaken trees, we will have an increased fire threat in the drier years,” Blumenfeld said.
It matters when the precipitation falls. Winter snow often runs off quickly in the spring, depriving the trees of its moisture. Though both temperature and precipitation are rising, it isn’t a pure linear trend. Wet years tend to be milder, slightly cool, and warm years tend towards moderate to low precipitation. 2021 was one of the hottest summers on record in Minnesota, and it was also very dry — the prime conditions for a wildfire.
The word wildfire often conjures the image of a hot and dry forest, like in California or Australia, somewhere very much not-Minnesota, with its snow, lakes, and boggy terrain. But even Minnesota has wildfire seasons—in the spring and fall.
Ninety percent of fires in the state are caused by people. The DNR tracks fire danger around the state and imposes restrictions in drought-susceptible areas.
In southern Minnesota, fires can be limited by smaller parcels of land, surrounding marshes, human habitation, and infrastructure like roads. Smaller parcels cannot burn as long or spread as easily as larger parcels, according to Travis Verdegan, forester and predictive services coordinator at the DNR.
In the north, large parcels of forest are more common, which means fires are more likely to build out of control. Additionally, years of fire suppression allow the buildup of plant growth, which provides ample fuel for fires.
Northeastern Minnesota, home to the Superior National Forest, the Boundary Waters Canoe Area Wilderness, Voyageurs National Park, and state forest land, has more than three million acres of woods susceptible to wildfire conditions. The Greenwood Fire burned 27,000 acres from August to October of 2021. About 300 homes were evacuated, and more than 14 homes and 60 outbuildings were destroyed.
AQI, or air quality index, is a measure of particles in a cubic meter of air. Lower AQI means healthier, cleaner air. AQI levels above 100 are defined as unhealthy for sensitive groups.
In 2021, smoky skies plagued the region all summer. Minnesota communities experienced about 40 days of prolonged air quality above 50 AQI, and 10 days above 100 AQI.
The MPCA has not yet released 2021 data on emergency department visits for respiratory issues. However, anecdotal evidence and historical literature tell us it is likely that such visits spiked during the smoke events.
According to Jesse Berman, assistant professor of environmental epidemiology at the University of Minnesota, the danger of smoke lies in the size of the particulates.
Wildfire particulate matter can be 2.5 micrometers or less in size (PM 2.5), which is smaller than the width of a hair. “These particles penetrate deeper into lungs and damage sensitive tissue that provides oxygen to the body,” said Berman.
Additionally, the type of materials burned can create different dangers. Fires near industry can contain toxic metals. When trees burn, the smoke mostly contains minerals and carbonates — whatever makes up the trees and surrounding soil.
PM 2.5 smoke travels with the winds, covering wide geographic areas and spreading the health risks. These include risks for cardiovascular, respiratory, kidney and neurological systems, poor birth outcomes for women, and increased risk of Alzheimer’s disease.
Children, the elderly, and those with pre-existing conditions are among the most vulnerable to PM 2.5. Individuals who work outside, like construction workers, are also more likely to be exposed to the particles.
People with lower income, disproportionately people of color, have higher rates of pre-existing conditions and therefore are in more danger from smoke events. Berman advises people at risk to reduce exposure by staying indoors. Air conditioning units are very good at keeping particulate matter out, and regular maintenance of their filters is important.
Use of local air pollution apps, such as EPA’s AirNow, is key for vulnerable groups, as these apps will issue warnings when AQI is high and precautions should be taken.
Duluth: uniquely vulnerable
In 2021 Duluth had 10 days with air quality above 100 AQI. For comparison, the last two decades in Duluth saw only one or two events per year over 100 AQI. Summers in the city have generally been below 50 AQI.
The smoke came from near and far. The Greenwood Fire, only 70 miles from Duluth, was a major source. Several California fires, whose smoke rose over the Rockies on high winds, arrived in Minnesota as a haze.
Satellite tracking revealed that Canadian wildfires were the largest contributor to Duluth’s poor air quality. More than ten million acres burned, nearly twice as much as the average over the last ten years.
A high-pressure system, referred to as a heat dome, lingered in the Canadian Shield region, circling Hudson Bay. Heat dome systems push out moisture and divert clouds. This process caused severe drought across Canada and parts of the western United States.
While the surface winds are variable, they usually blow west to east in Minnesota. But during the 2021 fire season they blew southeast — straight from the heat dome and towards Duluth.
Minnesota Pollution Control Agency (MPCA) Meterologist Matt Taraldsen described Duluth as a “really unique place in Minnesota” in terms of its weather.
The surrounding hills and cold lake can combine to make the city vulnerable to a specific type of atmospheric inversion called subsidence. Subsidence means cool, falling air. Generally, temperatures are warmer at the ground and cooler as altitude increases. But cold air can also settle on the ground, trapping warm air between the cold air above and below. This is an inversion. In summer the deep waters of Lake Superior are usually colder than the air above, which often provides cold air to a high-pressure front. Common in the Midwest, these high-pressure systems form about every two days or so. They vary in strength, but the stronger the system, the stronger subsidence will be.
Taraldsen said when a front passes over Duluth, the backside of the front sinks, dropping its load of smoke to the ground, where it is trapped between the two layers of cold air. And the hilly terrain can prolong an inversion by shielding Duluth from the mixing wind.
Lake Superior makes yet another contribution to the area’s unique weather. Last year’s smoke pollution in Duluth was strongest in the morning and at night because of the lake breeze, a phenomenon propelled by the temperature difference between the land and the lake.
During the afternoon, when it’s warmest, the air over land is relatively warmer than the air over Lake Superior. The breeze moves towards the lake and takes the smoke with it. But at night, the lake is warmer and the breeze goes the other way. This means smoke gathers on land, over the city, and air quality grows poor.
Sometimes a lake breeze can clean out one area while surrounding areas get a higher concentration of smoke. “It’s just like pushing a big broom,” said Taraldsen. “You end up with all the dust from the floor along the line wherever you stop sweeping.”
Lake breezes are common in warm springs and summers — times which can correlate with the Minnesota fire season. If an atmospheric inversion and wildfire smoke are present, Duluth is at risk for poor air quality events.
What we can expect this year
Though Minnesota’s spring has been relatively damp, distant areas like California, Canada, and New Mexico, where serious fires are already occurring, are predicted to have above normal wildfire seasons. If these areas burn, Minnesota is likely to receive their smoke.
Minnesota will have fires of its own. According to NOAA, the late summer into fall outlook trends toward above average temperatures and below average precipitation. Last winter’s endless snowfalls could dampen fire activity, but lingering dry conditions following the drought of 2021, which affected the northern half of the state especially, mean wildfire conditions will be dependent on weekly rainfall.
In recent years, Minnesota AQI forecasters have changed their focus from ozone to wildfire smoke as fires become an increasing trend locally and nationally. Wildfire smoke is one of the global effects of climate change that Minnesotans will experience locally—not just from Minnesota fires, but from smoke that transcends boundaries on a map.
It’ll be worthwhile to pay attention to the wildfire risk as it evolves over the summer.
Chance Lasher is pursuing a Bachelor’s Degree in Writing Studies and a minor in Environmental Science at the University of Minnesota Duluth. He is intensely interested in the effects climate change will have on the future world. He hopes continued writing on environmental issues and climate change will shift thought and action towards a better world.