2023 wildfires are reigniting in western Canada after 'overwintering'
All but one active fire in British Columbia started last year and smoldered under the snow all winter.
All but one active fire in British Columbia started last year and smoldered under the snow all winter.
All but one active fire in British Columbia started last year and smoldered under the snow all winter.
Canada's wildfire season is off to an active start for the second year in a row, and "overwintering" fires from 2023 are largely to blame.
Last year was far and away Canada's most active wildfire year on record. An estimated 36 to 39 million acres were burned across the country. Canada's previous record was 16 million acres.
Wildfire behavior experts say that many current fires in Alberta and British Columbia began last year and managed to survive a snowy winter.
"We had over 100 overwintering fires in British Columbia. About 50 in Alberta," said Dr. Mike Flannigan, a professor of wildland fire at Thompson Rivers University in Kamloops, British Columbia.
These overwintering fires were able to continue burning beneath the winter snowpack because of the thick layers of peat moss that cover forest floors in Western Canada.
"These fires burn in deep organic layers," Flannigan said. "You can have snow on the surface, and these fires continue to smolder all winter long. And then spring comes, snow melts, fires pop to the surface, and if they’ve got somewhere to spread, they do."
Several fires emerged in northern British Columbia last week, prompting evacuations.
Winds in the upper part of the atmosphere have since carried smoke south and east into the U.S. plains. On Tuesday, air quality readings showed pollution levels that would be unhealthy for some.
Flannigan said that given how active May has been so far, more rounds of smoke should be expected in parts of Canada and the U.S. through the spring.
"Because we have so many fires that are burning on the landscape already and because [western Canada] has an ongoing drought I expect spring to be very active in the West," he said.
Every wildland fire releases carbon that gets stored in vegetation. Peat forests may release substantially larger amounts of carbon compared to the types of forests that grow in California.
That has climate scientists watching for potential global temperature impacts. The released carbon could contribute to atmospheric warming. Data also shows that large amounts of smoke can also contribute to temporary cooling.
Flannigan said that while the long-term effect of fires on global temperatures is unclear, there is a connection between human-caused climate change and the risk of more large fires in the future. In a warmer climate, fire fuels dry out much faster.
"The drier the fuels, the easier it is for a fire to start. The easier it is for a fire to spread," he said. "That means more fuel is available to burn. That leads to higher intensity fires that are difficult to impossible to extinguish through direct attack."
Flannigan added that an increased risk of more wildfires does not mean that every season will be a bad one.
California has experienced this firsthand with more than 4 million acres burning in the state in 2020, more than 2 million acres in 2021, then close to just 300,000 acres each of the last two years.
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