MINNESOTA — World Soil Day, celebrated this year on Thursday, Dec. 5, brings awareness to the roles soil has in each of our lives, along with the sustainable management of its resources. Fittingly, this year’s theme is “Caring for soils: Measure, monitor, manage.” The celebration for World Soil Day takes place in Bangkok, Thailand — half a world away. But here in the USDA Forest Service, we can see its importance by looking no further than northern Minnesota, where our own soil scientists are observing wildfire’s troubling new effect on peatlands.

Largely located in northern Minnesota, peatlands are a type of wetland area composed of decaying, water-logged plant material. The wetland area prevents the plant material from fully decomposing to form layers of peat soil over thousands of years. Located in just under three percent of the earth’s terrestrial surface, peatlands are carbon-rich storage areas.  

Due to the water volume in peatlands, it is not common to see fire impacting those areas. But with more extreme weather events becoming the norm, peatlands are at greater risk. And one concern is that intense wildfires can cause the carbon stored in peatlands to be released into the atmosphere.

“The point to drive home is, what we are seeing is the weather is tending to be a bit more chaotic, where we get these prolonged periods of droughts — severe droughts,” said David Morley, soil scientist with the Superior National Forest. “This spring when we had heavy rains, that 13 inches of rain came in just a few storms over a week period, and flooding and erosion issues with it. It is a different environment we are in.”

In August 2021, a wildfire was detected approximately 10 miles south of Isabella, Minn. At the time, the area was impacted by severe drought and high winds. Ignited by a lightning strike, the Greenwood fire ultimately burned over 28,000 acres — and became a worrying example of peatlands becoming more vulnerable to wildfire.

“There were areas up to a meter of peat that was consumed by the fire,” said Morley. “Areas where some of the mineral soil beneath the peat was exposed.”

To measure the volume of peatlands burned in the Greenwood fire, Randy Kolka, a research soil scientist with the Forest Service’s Northern Research Station, utilized Light Detection and Ranging data from uncrewed aerial system flights flown by the State of Minnesota just prior to the fire and compared them to LiDAR data collected from UAS flights in August 2023.

“The volume lost is key to understanding the total greenhouse gas, nitrogen and mercury emissions from the fire,” said Kolka. “The volume lost is a result of subtracting the post-flight LiDAR elevations from the pre-flight elevations and is led by an expert LiDAR research group at the Boise State University, our main partner in this research, along with the University of Minnesota and Department of Energy’s Oak Ridge National Laboratory in Tennessee.”

While the research continues, it is important to educate the public on the importance of peatlands, which are both rare and ecologically significant.

“Within the Eastern Region of the Forest Service, we have wetlands throughout, but many of our peatlands are only located in the Lake States forests,” said James Gries, assistant director of Air, Water, Lands, Soils, and Minerals in the Eastern Region. “These peatlands store massive amounts of carbon and are crucial for global carbon cycling and are likely to be impacted by climate change and increased fire.”

For more detailed information from the researchers cited in this story, please listen to their episode of Forest North: The Dirt on Soil Science.