Boreal warning: Climate change could make Canada's forest a carbon emitter

As the world's attention is focused on wildfires in the Amazon, an international group of researchers has issued a warning about fires caused by climate changeand theirimpact on Canada's boreal forest.

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Canada's boreal forest is vast, stretching from coast to coast and covering some 270 million hectares.

"The boreal forest has historically acted as a place where carbon is stored over many centuries, sometimes millennia," said Jill Johnstone.

Johnstone is an adjunct biology professor at the University of Saskatchewanand part of a research team studying the effect of severe fires in the Northwest Territories in 2014.

Fires will actually feedback to increase climate warming.- Jill Johnstone

Tipping the balance

What they've discovered is of great concern.

According to Johnstone and her team, if the number of severe forest fires continues to increase as a result of climate change, then the boreal forest's ability to store carbon is in jeopardy.

"Parts of the boreal forest are going to shift to being actually a source of carbon and release carbon that's been stored for long periods," explained Johnstone.

Under normal circumstances, said Johnstone, older parts of the boreal forest are most susceptible to fire and for the most part, historical carbon buried down in deeper layers of soil is protected. The real concern here is in younger stands of trees, where wildfires can quickly burn off protective layers of organic material and get down into older soils where carbon is stored. This could tip the balance, turning the forest into a carbon emitter thatcontributesto the greenhouse effect.

"So that isn't a good news story because it means that the emissions from these fires will actually feedback to increase climate warming rather than to act as a dampening effect."

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Their findings, recently published in the journal Nature, are the result of a three-year field study comparing soil samples taken from burned and unburned regions of forest in the Northwest Territories.

"This research has opened up a whole new can of worms for us," said Johnstone.

Much work to do

One of the things the team will have to figure out is whether young sections of forest, dominated by species of trees that are less flammable, will be able to stand up to the stress that's expected to come as the climate continues to warm.

"Maybe these young stands will actually continue to resist burning and we won't see an increase in fire activity," said Johnstone. "That really depends on whether the vegetation can inhibit fire even under these future extreme fire conditions that were predicting."

One thing not in question is that humanity needs to figure out how to slow climate change, Johnstone said.

"We need to really continue to think about how we can reduce our emissions."