In 2023, Canadian wildfires burned nearly 150,000 square kilometers of forest—about 4 percent of the country’s forested land—releasing an estimated 554 million tonnes of carbon into the atmosphere, according to a new study. This area is more than twice the size of New Brunswick. The catastrophic fires, largely concentrated in northern Quebec, Alberta, British Columbia, and the Northwest Territories, generated expansive smoke plumes that impacted air quality as far as major U.S. cities including New York and Washington.

The research, led by Dr. Gonsamo and his colleagues, sought to refine estimates of carbon emissions from last year’s fires while distinguishing between carbon released from above-ground vegetation and soil organic matter. While above-ground biomass such as branches and leaves contribute to wildfire carbon emissions, the study found that carbon stored in forest soils—often overlooked—accounted for roughly 76 percent of the total emissions, totaling around 423 million tonnes from below ground. This finding highlights the substantial role of soil carbon in wildfire emissions, especially under the increasingly dry and hot conditions driven by climate change.

Using a 2021 nationwide soil carbon inventory developed through remote sensing at McMaster University and combining it with field surveys in burned northern Quebec regions, the team was able to evaluate carbon loss at a granular scale of 30 by 30 meters. Advanced machine learning models were then applied to extrapolate these results across the larger burn areas. Their analysis produced a total carbon emission estimate of 554 million tonnes from the 2023 wildfires.

This figure aligns with prior estimates from other studies, including NASA Jet Propulsion Laboratory research that placed wildfire carbon emissions in a range between 469 million and 639 million tonnes for the same year. The Canadian wildfire emissions equate to about two-thirds of the annual fossil fuel carbon emissions produced by India, the world’s third-largest emitter.

Experts note that climate change is intensifying multiple factors that contribute to these high emission levels. Werner Kurz, a retired Natural Resources Canada scientist and project advisor, emphasized that warming temperatures are not only increasing wildfire severity but also lowering water tables and accelerating permafrost thaw. These changes expose significant new stores of soil carbon to burning.

University of Alberta fire scientist Mike Flannigan pointed out that flash drought—rapid drying episodes caused by extreme heat—is likely to worsen conditions, promoting faster fire spread and making containment more difficult. He acknowledged that preventing large fires is increasingly challenging, especially when prevailing winds carry smoke across borders, affecting air quality in the United States.

While the study does not include data from the 2026 wildfires, initial observations suggest that areas burning this year have similar soil carbon content to those affected in 2023, implying that below-ground carbon will again be a major source of emissions. These findings underscore growing concerns about the contribution of wildfire soil carbon release to global carbon budgets amid ongoing climate change.