In the face of climate change, permafrost peatland wildfires could play more of a role in the destructive cycle of global warming, University of Alberta research suggests.
A recent study showed that after frozen peatlands burn, they can release large amounts of long‑stored carbon for several years - meaning as climate warming amps up, the frequency and severity of wildfires in Canada's northwestern boreal peatlands could turn them into long-term sources of greenhouse gas, says lead author Christopher Schulze, who conducted the work to earn a PhD in water and land resources.
"It could turn these ecosystems from carbon sinks, which absorb harmful greenhouse gas from the atmosphere, into carbon sources."
The research presents the first multi‑year measurements of how burned permafrost peatlands behave, providing vital information to update climate impact models.
"Without data on these post-fire emissions, there's a risk of underestimating the long‑term carbon losses from wildfire‑affected regions," he adds. "Updating models with these numbers is crucial, because if permafrost peatlands flip from carbon sinks to carbon sources, they can accelerate global warming."
The researchers explored what happened to carbon exchange - the process of releasing carbon into the air versus absorbing it back into the ground - from frozen peatlands in Western Canada's Taiga Plains Ecozone in the first four years after they burned in 2019, compared with a similar peatland nearby that had burned in 2007. They also looked at how long it took for the areas to recover their previous function as carbon sinks.
The analysis revealed that burned peatlands experienced large net carbon losses for several years after the fire, losing around 130 grams of carbon per square metre per year in the first four years. Emissions from fire-exposed, decomposing peat and less uptake of carbon dioxide by burned vegetation were driving factors.
When combined, the initial combustion from wildfire and the subsequent 15 years of carbon release resulted in a total loss of 2.9 kilograms of carbon per square metre, with post-fire emissions alone accounting for almost 40 per cent of that amount.
Given that extreme wildfires in 2023 burned approximately 15,000 square kilometres of peatlands on the Taiga Plains, the study suggests they will release about two million tonnes of carbon as carbon dioxide in 2026 - equivalent to per capita annual emissions of 500,000 Canadians.
"It shows that the impact of a wildfire on the climate extends into the future far beyond the immediate burning event," Schulze notes.
As well, post-fire warming poses an additional risk by causing deeper thaw and the potential release of old, deep "legacy" carbon, the researchers note. Although the study indicates that after about 15 years, the burned peatlands could recover their ability to absorb more carbon than they release, that resilience has limits, Schulze says.
"If climate change drives more frequent, hotter or larger wildfires, the recovery clock - in this case, long-term carbon sink function - may not get the chance to reset."
Overall, the findings could help guide climate policy and conservation planning, says David Olefeldt, a professor in the Faculty of Agricultural, Life & Environmental Sciences who co-led the study.
"The results will be used to improve modelling of the total greenhouse balance of Canadian peatlands, which represent a key component of the Canadian reporting of land-atmosphere greenhouse gas emissions," he says.
"Knowing the impacts of wildfire on peatlands will also further highlight the value of peatland conservation, which can direct decisions on establishing northern Indigenous protected conserved areas."
