Report details how tundra has become a carbon emitter

Increasingly frequent and severe wildfires have become a yearly concern for many Arctic communities, and a chapter of a new U.S. report involving one Canadian university—Université de Montréal—suggests that they are also having a significant impact on carbon emissions in the region.

When wildfire emissions were accounted for, the Arctic tundra has shifted from storing carbon to being a source of carbon emissions to the atmosphere, according to findings published in the U.S. National Oceanic and Atmospheric Administration (NOAA)’s 2024 Arctic Report Card.

Led by the Permafrost Pathways initiative at Woodwell Climate Research Center, in Massachusetts—with input from UdeM biogeosciences researcher Oliver Sonnentag and two members of his Atmosbios laboratory, Haley Alcock and Gabriel Hould Gosselin—the report’s chapter on Arctic terrestrial carbon cycling tracks 40 years of permafrost monitoring and more than half a century of increasing wildfire.

On average, permafrost temperatures measured in 2024 were the second warmest on record at long-term monitoring sites across Alaska, and the year registered the second highest wildfire emissions north of the Arctic Circle.

“Climate-driven disturbances such as wildfire may last no longer than a few days or weeks,” said Sonnentag, who for the past 10 years was holder of the Canada Research Chair in Atmospheric Biogeosciences in High Latitudes.

“But they may negatively alter or even trigger the loss of important ecosystem services such as subsistence, weather and climate regulation. Despite their well-documented effects on ecosystems and society, the future impacts of climate-driven disturbances remain highly uncertain.”

Now a major metric

Co-led by collaborators at University of Alaska-Fairbanks and Northern Arizona University, the report’s chapter on land carbon cycling details findings that stand out among a series of Arctic climate indicators tracked annually by the NOAA. For the first time in its report card’s 25-year history, land carbon cycling is recognized among these major metrics of Arctic warming and change.

“The Arctic is warming up to four times the global rate,” said Permafrost Pathways lead scientist Sue Natali, the lead author of the carbon cycling chapter.

“We need accurate, holistic, and comprehensive knowledge of how climate changes will affect the amount of carbon the Arctic is taking up and storing, and how much it’s releasing back into the atmosphere, in order to effectively address this crisis,” she said.

“This report represents a critical step toward quantifying these emissions at scale which is critical for understanding their impacts on global climate and informing equitable mitigation and adaptation strategies.”

Added Brendan Rogers, co-lead of Permafrost Pathways and co-author of the carbon chapter of the report card: “In recent years, we’ve seen how increasing fire activity from climate change threatens both the communities and the carbon stored in permafrost, but now we’re beginning to be able to measure the cumulative impact to the atmosphere, and it’s significant.”

Involving 97 scientists from 11 countries, the Arctic Report Card reveals record-setting observations of a rapidly warming Arctic, including rising air temperatures, declines of large inland caribou herds, and increasing precipitation. These climate impacts and others threaten the health, subsistence and homes of many Indigenous communities living in the Arctic.

“This year’s report demonstrates the urgent need for adaptation as climate conditions quickly change,” said Twila Moon, the report card’s lead editor and deputy lead scientist at the U.S. National Snow and Ice Data Center. “Indigenous knowledge and community-led research programs can inform successful responses to rapid Arctic changes.”