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As thousands fled, a few paused to capture the moment for social media. Their videos show vehicles lining the road, while flames and smoke billow overhead. Behind lie their neighbourhoods, many now destroyed by the Fort McMurray wildfire.

More than 80,000 Canadians have been forced to leave their homes this week, in the largest evacuation of its kind in the country’s history. So far, the fire has burned through an area covering at least 850 square kilometres and shows no signs of stopping. Alberta is in a state of emergency and even the infamous tar sand oilfields have had to curb output.

“While it is too soon to comprehend the full extent of the damage, we know that it is far-reaching and utterly devastating,” said prime minister Justin Trudeau in a statement to the House of Commons yesterday.


The effects may extend far beyond Canada and Alaska, because of the frozen organic matter under the forest permafrost. Wildfires can strip away the protective vegetative blanket and release all that stockpiled carbon into the atmosphere, says Merritt Turetsky, an ecosystem ecologist at the University of Guelph in Ontario. The thawing soil could also trigger microbial activity, releasing more carbon dioxide and methane.

In other words, more wildfires can mean more greenhouse gases, accelerating the very climate change that may have helped kick off the fires in the first place — not to mention changing the equation for rest of the globe.

“This is carbon that the ecosystem has not seen for thousands of years and now it’s being released into the atmosphere,” says Turetsky. “We need to start thinking about permafrost and we need to start thinking about deep carbon and everything we can do to inhibit the progression of climate change.”

Landscape shaped by fire

Serious wildfires aren’t unusual for northern America. Pick a spot in Canada’s boreal forests — a subarctic swathe of hardy coniferous trees with deciduous mixed in — and chances are that it’s been on fire at least once in the past century. For thousands of years, wildfires have shaped this forest landscape.

But recently, they have become more severe. Last year, the military was called in to help fight aggressive fires in Saskatchewan, while Alaska experienced its second-worst wildfire year in recorded history.

The year before, 34,000 square kilometres of land burned in the Northwest Territories, in what some described as the worst fires the region had seen in decades. The events at Fort McMurray may signal the start of yet another brutal wildfire season.

“It’s unusual to see an early season fire get this severe,” says Turetsky. “It really does feel like the new normal is [that] some part of Canada is going to be experiencing tremendous fire pressure at any point in time.”

Recent hot and dry weather probably kicked off the Fort McMurray wildfire. It has been unseasonably warm: hitting 32 °C on Tuesday, the city set an all-time temperature record for 3 May. It has also had lower than average rainfall this year.

More broadly, climate change seems to have had an effect, too. A report released in March by the US National Academy of Sciences concluded that climate warming has led to longer fire seasons. An earlier study of interior Alaska found that boreal forests have been burning in the last few decades at a rate unprecedented in the previous 10,000 years, driven by the warming climate.

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But — unlike with hurricanes or heatwaves — climate change’s role in specific wildfires is tough to assess. It’s difficult to model the short-term weather patterns associated with wildfires, or pin down a relationship between climate change and the lightning strikes that often start fires.

“It’s still a story that needs to be figured out,” says Scott Rupp, a forest ecologist at the University of Alaska Fairbanks. “You could point to this particular fire as just one more data point on some of the trends that have been going on over the past two decades.”

What will that trend mean for the future? More frequent and severe fires will strain the limited government resources available to fight and recover from them. Over the long term, more wildfires may favour deciduous over coniferous trees, shifting the characteristics of the ecosystem itself.

Read more: Ignition impossible: When wildfires set the air alight