Wildfire management could do more to keep carbon in northern forests, where fires increasingly burn through organic soils that have stored carbon over several fire cycles. Recent research points to two tools, stopping selected fires early and encouraging tree species that burn less intensely.
Northern Arizona University ecologist Michelle Mack brought that work to Harvard in a Charles Bullard Lecture on far-northern megafires and local solutions. Mack leads the Bonanza Creek Long-Term Ecological Research program in Alaska, and her published studies show where wildfire carbon losses happen and what can limit them.
Shorter Fire Intervals Expose Older Soil Carbon
In boreal forests, much of the carbon at stake sits below the trees. Organic soil layers can hold carbon that survived earlier fires, but that reserve becomes exposed when fires return sooner or burn deeper.
A 2019 study in Nature, with Mack as senior author, used radiocarbon dating after the 2014 megafires in Canada's Northwest Territories. In older stands, this "legacy carbon" stayed protected. In stands younger than 60 years, it burned. The cutoff reflects the forests studied and is not a universal threshold, but the finding shows why inventories that count only trees can miss much of a forest's wildfire exposure.
Deciduous Stands Lose Less Carbon When They Burn
Mack's research also points to a counterweight. A 2021 study in Science tracked 75 Alaskan black spruce stands for 13 years after they burned in 2004. Where severe fire let deciduous broadleaf trees replace spruce, the new stands accumulated carbon four times faster, and over a 100-year fire cycle they more than made up for the soil carbon lost.
A Nature Climate Change paper published in January, again with Mack as a co-author, found that deciduous forests in interior Alaska and Canada's Yukon lose less than half as much carbon to combustion per unit of burned area as conifer forests. The result supports testing deciduous stands as living fuel breaks and in restoration. It does not show that wildfire is a net climate benefit, or that regrowth offsets emissions right away.
Early Suppression Brings Costs and Tradeoffs
A 2022 peer-reviewed study in Science Advances, led by Carly Phillips of the Union of Concerned Scientists and Woodwell Climate Research Center, projected that boreal burned area could increase by 24%–169% in Alaska and 36%–150% in Canada between 2020 and 2050. If existing fire-suppression levels continued, cumulative net emissions could reach 1.33–11.93 gigatonnes of carbon dioxide over that period. The authors estimated that expanded fire management in Alaska could avoid CO₂ emissions at an average cost of approximately US$12.63 per metric ton, comparable to or below several other mitigation approaches evaluated in the study.
Fuel treatments carry their own tradeoffs. A National Park Service summary of a 2023 study found that thinning and shearblading in interior Alaska did not consistently reduce modeled fire behavior about 20 years after treatment. Permafrost thaw depth increased at treated sites, most of all where shearblading left a thin organic layer, and those areas filled in with deciduous shrubs and seedlings.
For sustainability teams and forest owners, particularly those relying on forest carbon credits that wildfire can erase, the research argues for judging each suppression or fuel project on local evidence. Assuming every treatment delivers the same benefit can overstate stored carbon at a time when the math behind offset claims is drawing closer scrutiny.
Northern soils hold carbon built up over multiple fire cycles, and expanding Arctic peatlands raise the stakes for the global carbon balance. Keeping that carbon in place will take quick fire response along with forests that burn less of it.
