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Climate
Cathy Wurzer and Lukas Levin

'Zombie fires' under snow raise concern for upcoming wildfire season

Forest fires rage on in the distance
A plume of smoke hangs in the air as forest fires rage on in the distance in Fort McMurray, Alberta on May 4, 2016. More than 100 Canadian wildfires are still burning underground from fires in 2023. These fires that smolder over winter are called “zombie fires.”
Cole Burston | AFP | Getty 2016

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Minnesotans inhaled more Canadian wildfire smoke last summer than much of the nation and 2024 could bring more of the same.

More than 100 of those Canadian wildfires are still burning underground. These fires that smolder over winter are called “zombie fires.”

Minnesota Department of Natural Resources wildfire operations supervisor William Glesener explained how fires can burn under snow blankets and lead to a more active wildfire season.

Listen to the full conversation with Glesener using the audio player above or read a transcript of it below. Both have been edited for clarity and length.

I did not know that forest fires can simmer in the cold and snow. Is that what is happening in Canada?

That is what is happening in Canada. The term zombie fires is new to me. The technical term in the wildfire community is peat fires or ground fires.

They burn under the surface of the ground and can smolder for extended periods of time. We have peat fires every year in Minnesota. We had a few last year. Usually, our process is we stir up the soil, we get water on it, and we try to flood them out.

Folks might remember a couple of years ago, by Delano, there was a fire that we actually flooded. We were able to put that out in very short order compared to what they are dealing with in Canada due to the remote nature of those fires.

So, once those wildfires start and you are in a drought condition, all that material that is usually underwater and usually wet that normally would not burn becomes available. Any surface fire that goes across that area can ignite and then it just continues to smolder and smolder and smolder, much like a campfire does when people don't put them out.

Can these fires spring up once the ground thaws? Can they reignite into a larger fire?

If you have an overwintering fire or a peat fire that starts and it's not taken care of, they can—when we have a hot, windy, dry day— poke their little heads up and throw some sparks and embers out and if there are fuels in the vicinity that can ignite, they will burn across the landscape.

What does the Minnesota situation for zombie fires look like at this point?

When we look at the state of Minnesota being in 85 percent abnormally dry or worse conditions, that is very concerning. With the warm and dry weather that we will have this spring, it's going to be a busy year.

Are you prepared? Do you think there are enough crews to fight fires as they pop up?

We just had a preseason meeting with all of our fire staff here in Grand Rapids. We brought in people from across the state and got our coordination elements together and started laying out plans on how we're going to operate. I think we will be successful.

We have agreements so that if we need help from Canada, they can come down. If we need help from Wisconsin, Michigan, North Dakota, or South Dakota, they can come in and help us. Just like we traveled nationwide to help others, we can make those requests. It's going to be busy. It's going to be a lot of effort. But, you know, we have a good operation in place so that we can protect the citizens, resources, life and property of the state of Minnesota.