N.W.T.'s record wildfire season in 2014 tipping point for boreal forest, says study

Canada's boreal forests areproducing more carbon than they capture during bad forest-fire years, and a new report from Wilfrid Laurier University expects this trend to continue.

"The boreal forest is a really critical carbon store for the planet.It stores about a third of the terrestrial carbon," said Jennifer Baltzer, Wilfrid Laurier University associate professor and co-author of apaper recently published in the scientific journal Nature.

Baltzerand her family havespent several summers in the Yellowknife area, including the summer of 2014the worst wildfire season on record for the N.W.T. It was this summer thatkicked off an indirect collaboration with the N.W.T. government to look into the impacts of extreme wildfire seasons and ultimately fuelled Baltzer'sresearch in this area.

"This research, with the help and partnership of the GNWT, has really advanced our understanding of these fires and the tremendous impact extreme wildfires have on globally critical stores of carbon," she said.

She is recognized as one of the country's top-tier researchers on how climate change impacts Canadian forests, and sits as theCanada Research Chair in Forests and Global Change.

Fire years like 2014 are unusual, but they're becoming increasingly common with climate warming.- Jennifer Baltzer

The 2014 fire season in the N.W.T. burned 34,000 square kilometres of forest, according to Natural Resources Canada.Those 380 firesreleased roughly 94.5 megatonnes of carbon, half of the carbon sequestered annually in all of Canada.

The boreal forest captures carbon from the air and stores it back underground in soil and layers of mosses. Extreme forest fires burn can burn so hot and so long that they reach carbon that has been stored deep in the earth for many years and release it back into the atmosphere.

If this trend continues, and the boreal forest becomes a regular carbon emitter rather than a carbon sink, this will create a positive feedback loop exacerbatingthe overall climate crisis, said Baltzer.

Boreal forests need wildfires, just not so many

Wildfires are part of the lifecycle ofboreal forests, and important to their maintenance and biodiversity.

What is alarming in the new research is that hotter, drier conditions throughout the North result in the forests burning hotter, deeper, and more often than the norm.

"Fire is a critical part of the boreal forest," saidBaltzer. "But fire years like 2014 are unusual, but they're becoming increasingly common with climate warming."

Historically, boreal forests experience wildfires every 60 to 100 years. When fires occur more frequently, the forest doesn't not havethe chance to build up new layers of soil, giving fire access farther underground toburn layers of carbon that have potentially been stored there for thousands of years.

"Many species are adapted to thrive under conditions with fairly regular wildfires," said Baltzer.

"Part of the changes that we see associated with these altered fire regimes is not only changes in the carbon storage function but changes in the way the system recovers from severe burning."