"How overwintering fires are changing the landscape in boreal Alaska and the Northwest Territories of Canada"
"Winter usually offers a reprieve from the fire season. However, scientists have noted an uptick in a very specific type of fire as climate change alters the northern reaches of our planet in unrecognizable ways. Zombie fires are not a new phenomenon, but researchers in Alaska and the Northwest Territories of Canada have found that with hotter summers and blazing wildfires, fire has the potential to lie dormant in dry undergrowth, even under snow. When the next summer rolls around, with dry conditions, those fires can reemerge.
Jennifer Baltzer is a Canada Research Chair, a prestigious title given to professors at Canadian universities, in Forests and Global Change. And her team originally thought that only peatlands, with their deep peat soil ideal for combustion, could harbor zombie fires. But, when the team visited 20 sites across the boreal forests, they found that overwintering fires could be supported across the boreal landscape, creeping into upland forests. In the aftermath of the 2014 fire season, Baltzer's research created the first-ever field study of overwintering fires.
In 2023, over 17 million hectares (over 40 million acres) burned across Canada, four times the area burned in 2014. After this record fire year, Western Canada also had the highest frequency of overwintering fires it had ever seen—around 150 zombie fires across the country. In the past, the majority of fires were caused by humans or lightning strikes. Now, overwintering fires have become a larger part of the equation.
“All three of these ignition sources are projected to increase in the coming decades. Zombie fires have always been a part of the system, but not as a frequent ignition source,” Merritt Turetsky, an ecosystem ecologist at the University of Colorado Boulder, said. “That's my concern for the future—that we are going to have all three types of ignitions cranking up to a higher frequency than we’ve ever seen before.” "
