Beneath some of Alberta’s snowy cold, “zombie” wildfires are smoldering, slumbering dragons waiting for air and warmth to snarl back to life.
The remnants of some 2024 wildfires have gone nearly anaerobic in Alberta — overwintering and flameless, thriving on peat and dry foliage detritus deep under the forest bed, with wisps of smoke rising from remote forest floors, like giant Dutch ovens, with heat signatures only detectable by satellites and infrared technology.
“I’m beginning to think that we are going to see fires that started in 2023 still burning in 2025, which is kind of mindboggling for here,” said former University of Alberta professor Mike Flannigan, now professor of wildland fire at Thompson Rivers University, and the B.C. Innovation Research Chair for emergency management, predictive services and fire sites.
The 2023 fire season, with more than 100 fires burning in Western Canada, was exceptional, he said.
“That’s really triggered something that I’ve never seen before, which is kind of rare, because I thought I’ve seen just about everything.”
In the first part of the 2024 fire season, most of the first 500,000 hectares burned were the result of fires that started in the previous year, he said.
“I’ve never seen anything like that,” said Flannigan, who’s been watching wildfire statistics since the 1970s.
Continuing drought unchecked by an unexpectedly weak La Nina climate effect means more wildfires will survive and wake up come spring, living up to their “zombie” nickname.
Traditionally, fires started in the spring or summer are extinguished, either by fire suppression activities or by Mother Nature’s rain.
There were fires overwintering in the Northwest Territories and Quebec, but only B.C. and Alberta really seem to be documenting them in any degree, Flannigan said.
Fighting overwintering fire
In the deep organic layers of sphagnum mosses and “peat,” fire can smoulder anaerobically for long periods, a phenomenon not limited to Canada. Some peat fires have burned in Indonesia for decades, Flannigan noted.
The smouldering ground could rise to 350 degrees — temperatures for baking cookies or roasts.
“We actually could put something in tinfoil, and it would take a while, because it’s moving really slowly, but yeah, it could cook potatoes or beans or fish or whatever,” Flannigan said ruefully.
During fall, things get quieter for firefighters, and fire management goes into less-emergent mop-up mode, putting out hot spots in the perimeter of fires.
“Hot spots in the interior (of the fire) are of less concern, because even if they wake up the following spring, after the snow melts, they’ve got nothing to burn. Whereas the ones on the edge, they can grow,” Flannigan said.
Historically, Alberta fire season used to start April 1. But around 2015, because they were getting fires in February, the season start was moved to March 1, then bumped up again to mid-February in 2024, because the 2023 fire season was so exceptional.
The fire season went well into the fall, with crews busy fighting massive active fires. It became physically impossible to go around all fire perimeters and put out all hotspots.
A mild 2024 winter with not much precipitation has left northeastern Alberta relatively dry.
“They’ve got some precipitation, but not enough to overcome the drought. So these fires are continuing to smoulder. And when spring comes, the snow melts, weather conditions are conducive. These fires will continue to grow,” Flannigan said.
“As we get warmer and drier, I expect to see more of these overwintering fires causing problems.”
Overwintering fires are typically dug in between 50 centimetres to one metre below the surface.
“The difficult part is extinguishing it. You can flood it out if you have lots of water, like with pumps and hoses. Sometimes they use backhoes if it’s a really deep spot, but it takes a lot of effort. It’s very time-consuming to get these smouldering fires and deep organic layers,” Flannigan said.
“That’s what they were doing last February — actioning these fires and mostly digging them up. Yes, it will freeze depending on the conditions. But you know, if you can get the water to the fire or at least raise the water table above where the fire is, it will go out.”
Conflicting forecasts
Climate has an immediate bearing on forest fire prospects, and when it comes to climate effects, some predictions are more solid than others, Flannigan said.
Seasonal forecasts are expected to start sometime in February. The overarching question is which climate effect pattern will hold weather sway over Western Canada.
“All the models said we’d be well into a La Nina starting months ago, and it did not happen.
“The models were wrong, it stayed neutral,” he said.
A cooler La Nina cycle with increased precipitation is more elusive than the warm and dry climate of El Nino, Flannigan said.
“They’re now updating the forecast and saying it’s probable we’ll get a weak La Nina for a couple of months and then flip back to neutral.”
If the ocean temperature is within a half-degree above or below the long-term average, that’s considered “neutral.”
“The ocean isn’t quite behaving the way it’s supposed to,” Flannigan said.
Overall, seasonal forecasts for temperature remain above normal for most of Canada, for most models — although some say it’ll be wetter or drier than normal in northern Alberta, Flannigan said.
The drought cycle Alberta has seen won’t be sated unless the province gets much more precipitation over a longer period — a rainy spring to dampen the already-dry landscape.
“I’d say odds are that we could have an active (fire season) in spring again, in part due to these overwintering fires, because their ignition’s ready to roll, as opposed to new fires that lightning or people start,” Flannigan said.
“As soon as the snow goes, and it gets warm, dry and windy, the fires pop up to the surface and start spreading.”
Zombies know no limits
The limbo of the underground fire isn’t just a rural phenomenon limited to the wilds outside Lac La Biche in northern Alberta.
One local example was the 2023 fire on the western rim of Anthony Henday Drive, said Derrick Forsythe, provincial information officer with Alberta Wildfire.
“That was a peat fire. That was a fire that had been underground for who knows how long, who knows what the source was,” Forsythe said.
It popped up and caught a good whiff of oxygen.
“There were some other fuels, and some trees and stuff in and around the area, and those kind of ignited and away we went,” he said.
“One of the most volatile times for us is that period between when the snow leaves and before the grass turns back to green, when we’re looking for green up and we’re not at green-up yet,” Forsythe said.