These wildfires never went out — they just moved underground

Under the ground, even under the snow, zombie fires are burning.

The remnants of the most extraordinary wildfire season in recent Canadian history are still smoldering on a scale that experts say is unprecedented. The warm and dry winter, particularly in western Canada, has left more than 150 fires burning across British Columbia and Alberta, according to the Canadian Interagency Forest Fire Center.

While it’s common that such hot spots — known as holdover or zombie fires — can smoke and smolder through the cold months, this amount of them is not.

“We’ve seen this before but never at this scale,” said Michael Flannigan, a wildfire expert and professor at Thompson Rivers University in British Columbia. “I’ve been watching fire in Canada and abroad since the late ’70s. I’ve never seen anything like this.”

These winter fires burn underground, often consuming peat — thick layers of compacted organic matter, including sphagnum moss. Plumes of smoke seep out, even from beneath snowfields. The vast majority of them are deemed “under control” by Canadian authorities, but experts worry that the fires could spread when spring comes and winds pick up.

“The perimeters are thousands and thousands of kilometers long. [Firefighters] haven’t gone and put all these hot spots out,” Flannigan said. “These fires can grow.”

The prevalence of these ongoing fires is a testament to last year’s outsize wildfire season, which shattered records for the amount of Canadian forests burned and created vast plumes of smoke that darkened skies in the Midwest and East Coast over the summer and choked major American cities with some of the worst air quality in the world. The roughly 45 million acres that burned is more than twice as much as the previous record in any year dating back to 1983, according to the Canadian Interagency Forest Fire Center. The fires also displaced hundreds of thousands of people from their homes.

These Canadian fires are part of the growing footprint of wildfires across North America and other parts of the world as the climate warms, primarily from humans burning fossil fuels.

Canada has vast swaths of boreal forest, so many trees that Canada accounts for some 10 percent of all the world’s forests. Just last year, the fires consumed about 4 percent of Canada’s forests.

A spokesperson for British Columbia’s Forests Ministry said in a statement that the amount of winter fires is “understandable given how widespread the fire activity and drought conditions were” last year. The 90 holdover fires in the province are all under control, the statement said, “meaning suppression efforts have ensured the wildfire will not spread any further at this time.”

“The BC Wildfire Service monitors these fires in case activity resurfaces and further wildfire response is needed,” the statement said.

Further warm and dry conditions brought on by the El Niño weather pattern have heightened fears about what’s to come this summer.

Federal Emergency Preparedness Minister Harjit Sajjan warned this past week that Canadians needed to be “prepared for the worst.”

“Early reporting suggests that this year’s wildfire season could be worse than the last,” Sajjan told reporters in Ottawa.