A wildfire rips through the boreal forest in Manitoba, Canada, in 2025
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Recent wildfires in the Arctic are believed to be significantly impacting global warming, more than previously estimated. While it was thought that these fires mainly burned recent vegetation, a new study indicates they are also releasing carbon stored in the soil for up to 5000 years.
According to Meri Ruppel from the Finnish Meteorological Institute, burning soil can release ancient carbon previously thought to be safely stored. Current climate models do not account for this release.
In the Arctic’s cold environment, plant growth is slow, but dead plant material accumulates over time, forming carbon-rich soils like peat. These soils have traditionally acted as carbon sinks, absorbing carbon dioxide from the atmosphere.
However, with the increase in large and frequent fires, this role is shifting. Ruppel’s team gathered soil samples from regions recently affected by fires to analyze the impact.
The analysis revealed that while surface vegetation burns rapidly, deeper layers of organic material smolder slowly, emitting black carbon and CO2.
Black carbon captures heat from the sun, contributing directly to atmospheric warming. When it settles on ice or snow, it darkens the surface, leading to melting that would not occur otherwise.
Ruppel explained at a European Geosciences Union meeting in Vienna that the age of carbon released by fires varies across environments, depending on soil depth and burn intensity.
The likelihood of ancient carbon release rises near the Arctic, where soils are shallow and organic matter is closer to the surface. For example, in Canada’s Northwest Territories, fires burn several centimeters into the soil, releasing carbon from 400 years ago.
In Greenland, fires penetrate an average of 10 centimeters, releasing carbon up to 560 years old, and in some areas, up to 1000 years old. In Quebec’s boreal forests, carbon dating back 5000 years has been released by fires, although this is not common, Ruppel noted.
The key question remains: how much ancient carbon is being released by these fires? Ruppel emphasized that more research is needed to quantify the extent of this phenomenon.
Sandy Harrison from the University of Reading, UK, highlighted the importance of this research, stating that as new fire patterns destroy soil layers and peatlands, significant amounts of ancient carbon may be released.
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