Quirks & Quarks

Which forest fires spew out the most CO2? It's the soil that matters, not the trees

New study finds that carbon emissions from boreal wildfires are largely coming from fuel available underground.

Study finds carbon emissions from boreal wildfires are largely coming from fuel available underground.

Jennifer Baltzer, middle, with students Genevieve Degre-Timmons and Kirsten Reid studying the boreal forest in the Northwest Territories after a wildfire burned in 2014. (Jennifer Baltzer)

As wildfires seasons worsen, it's become more important than ever for scientists to understand just how much carbon is being released by these fires, and the drivers leading to these carbon emissions. 

In a new study that looked at hundreds of fires in the boreal forest across Canada and Alaska, researchers found that the available fuel was the most important factor of determining how much carbon a fire will release.

Currently, scientists look at fire weather to determine carbon emissions in the boreal forest, which includes metrics like drought conditions and temperature. However this study showed that fire weather was a poor indicator of carbon combustion.

"Our main finding was that fuel availability, and not fire weather, was really important in determining biomass burning and carbon loss," said Jennifer Baltzer, a biologist at Wilfrid Laurier University and a Canada Research Chair in Forests and Global Change. "The large majority of carbon is coming from from below ground, and those carbon stocks make up about 80 to 90 percent of the carbon in the system."

Speaking with Quirks & Quarks host Bob McDonald, Baltzer discussed how this is especially important to understand in the boreal forest, which stores between 30 and 40 percent of terrestrial carbon.

The features that affect carbon emissions include stand age, forest composition, and soil moisture, which is likely to change as the climate warms and permafrost melts.

The wildfire research study, led by Xanthe Walker at Northern Arizona University, was recently published in the journal Nature Climate Change.

Produced and written by Amanda Buckiewicz


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