Canada’s northern boreal forests have been carbon sinks for millennia, but more recently are becoming sources of atmospheric carbon, and therefore could be contributing to the greenhouse effect. That’s the conclusion of an international study which includes researchers from the University of Saskatchewan.

Lead author of the paper, Xanthe Walker, who is a USask PhD graduate, explains that forest soil accumulates carbon, so it is considered a carbon sink but more recently there have been more fires and that means it’s not just the older forests that are burning. Their research found that in older stands of trees, this carbon remained protected from combustion because of thick, organic soil but in stands younger than 60 years, the legacy carbon burned because the protective soil didn’t have time to re-accumulate after the previous fire.

The paper says the frequency of boreal forest fires is projected to increase because of climate warming and drying and the total burned area is forecast to increase 130 to 350 per cent by mid-century.

Saskatchewan’s boreal forest is about 101-million acres, which would be bigger than Germany. Previous to this report, it was calculated that Saskatchewan’s forest stored 5-billion tonnes of carbon in its soils, peat and forest, which is equivalent to around 25 years’ worth of Canada’s greenhouse gas emissions at 2014 levels.