The devastating wildfires in northern Canada in recent years have climate consequences that go far beyond smoke and carbon dioxide released into the atmosphere, according to a new study co-authored by two NAU researchers.
The study, which looked at the various effects of fire in northern Canada and Alaska, wasn't all bad news: The researchers found fires in Canada, when coupled with snowpack, have a net cooling effect. That cooling, however, isn't enough to outweigh the warming effects of permafrost carbon released into the atmosphere from fires in Alaska.
The study, which NAU professor Scott Goetz called "the most comprehensive attempt to date to
document the myriad factors that play a role in the influence of fire on the climate system," confirms what more localized research has found and reaffirms the need for land and fire managers to reconsider how wildland fires are managed.
Hot on the trail
The research, led by Max Van Gerrevink, a doctoral student at Vrije Universiteit Amsterdam, and his doctoral adviser, Sander Veraverbeke, was conceived of on a smaller scale two decades ago by a small consortium of environmental scientists. This group included Goetz, a Regents' professor in the School of Informatics, Computing, and Cyber Systems, and Michelle Mack, Regents' professor in the Department of Biological Sciences and the Center for Ecosystem Science and Society. The ideas were shared with colleagues and passed down to postdocs and students, including senior author Brendan Rogers, a scientist at the Woodwell Climate Research Center and a former postdoc of Goetz.
Researchers combined historical fire records, satellite and climate data with machine learning, then quantified and mapped the net long-term climate impacts from multiple sources for fires across Alaska and western Canada between 2001 and 2019. The results indicate that, on average, Alaskan fires contribute to climate warming, whereas fires in Canada generally have a climate-cooling effect. The findings were published in Nature Geoscience THIS WEEK.
"While the majority of northern forest fires in North America are currently exerting a climate-cooling influence, this is likely to change as northern forests continue to warm," Van Gerrevink said. "Continued warming is expected to reduce snow cover and shorten its duration, which may substantially alter the net climate impacts of future fires as it reduces the dominant cooling source from increased reflectivity from snow."
Different fires, different outcomes
Alaska and Canada have different biomes. Unlike Alaska, much of Canada was covered by glaciers, and it contains extensive areas of tundra, which burns less frequently than its boreal forests (also known as taiga). As a result, the fires in Canada, even in the record-breaking fire seasons of 2023 and 2025, didn't lead to significant permafrost thaw, though the smoke and environmental damage still was devastating.
What's more, when the burned areas were covered in snow, more light was reflected off the snow instead of being absorbed by the ground, which led to a net cooling effect.
In Alaska, there's more vulnerable permafrost, so when fires rip through the region and permafrost thaws, huge amounts of stored carbon are released into the atmosphere, leading to more climate warming.
That's bad enough on its own, but it's potentially much worse. Mack said about 70% of the terrestrial Arctic is in Siberia and Eurasia, and it looks more like Alaska than it does Canada. That means if those areas burn, we're likely to see significant permafrost thaw and the resulting release of carbon into the atmosphere.
Major takeaways
Fire happens. Most of the fires studied were caused naturally by increasing lightning strikes and happening in areas away from people, so decision-makers aren't likely to do much fire suppression. It is time to discuss other options, both Mack and Goetz said.
"It's a call that we really have to take this seriously—the more fires there are, the more rapidly permafrost is going to thaw," Mack said. "Maybe we need to think about slowing down these natural fires. It would buy us time while we figure out other solutions to decarbonize the atmosphere."
"One clear takeaway is that fire managers and fire suppression efforts could attempt to prioritize fighting fires in areas that are permafrost-rich, because that's where the bulk of the carbon is stored and vulnerable post-fire," Goetz added. "When rich organic soils are combusted in fires, there is a big pulse of carbon dioxide in the atmosphere. Then, as permafrost thaw follows, it continues to emit more carbon over the years that follow fire."
