Wildfires turning boreal forests from carbon sinks to carbon sources

Bigger, hotter wildfires are turning Canada’s vast boreal forest into a significant new source of climate-changing greenhouse gases.

The shift, which may have already happened, could force firefighters to change how they battle northern blazes, says Merritt Turetsky, an ecologist at the University of Guelph and co-author of a recent study that appeared in Nature.

The boreal forest, a band of green that stretches over six provinces and two territories, has long been a storehouse of carbon.

Although fires sweep through as often as every 70 years, much carbon accumulates in soil — up to 75 kilograms of carbon per cubic metre, some of it thousands of years old.

But with climate change, fires are becoming more frequent, larger and more intense.

Turetsky and researchers from U.S. and Canadian universities wanted to see whether those changes affected stored carbon.

“Understanding the fate of this stockpile of boreal carbon is really important in the context of atmosphere greenhouse gases and Earth’s climate,” Turetsky says.

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