Highlights: So-called “winter” fires, also called “zombie fires”, continue to burn underground in Canada. Last summer, like all of Canada, the Northwest Territories experienced the worst fire season in its history. Random lightning, arson and the El Nino phenomenon do not alone explain the intensity of this summer's fires and the increase in winter fires. The vast majority of fires are caused by lightning from storms, with a small proportion caused by hibernating fires.

LIGHTING

Canada: under the snow, the phenomenon of “zombie fires” is already threatening the coming summer

So-called “winter” fires, also called “zombie fires”, resulting from the terrible summer season experienced by the Canadian Northwest Territories, continue to burn underground. Paradoxically protected by snow and accentuated by global warming, they require the authorities to be constantly vigilant.

Smoke from a winter fire along the road leading to Yellowknife, in the Northwest Territories, Canada, Tuesday, January 16, 2024. © Léopold Picot / RFI

By: Léopold Picot Follow

From our correspondent in Canada,

There's not much on the road that connects Calgary, the largest city in the western Canadian province of Alberta, to Yellowknife, a city of 20,000 in the Northwest Territories. Bison, a few foxes, rare cars, and forests... or at least what's left of them. Trees are charred over large portions as we approach Yellowknife, and even in the middle of winter, a few fumaroles continue to pierce through the thick snow cover.

Last summer, like all of Canada, the Northwest Territories experienced the worst fire season in its history. Among its 35,000 inhabitants, “

70% had to be evacuated, and four million hectares of our territories were affected

”, soberly lists Mike Westwick, information manager at the forest management service of the Northwest Territories, before adding: “

We are used to fires in the boreal forest. But this year, the burden on people and the environment has been particularly heavy

.” The fires were so powerful that they burned the soil deeply.

Read also Forest fires in Canada: evacuees from Yellowknife recount their escape from the flames

A phenomenon as old as time

The fumaroles visible along the Mackenzie Highway are partly the result of this intensity. Contrary to what our eyes lead us to believe, a fire does not only burn from the bottom up. The flames consume everything down to the basement itself, explains the manager: “

In the boreal forests, there are very good fuels, buried deep. Peat and other types of organic matter conduct heat and keep the embers trapped, so they remain active even in winter.

The phenomenon of hibernating fires has always existed, in Canada as elsewhere. But the surface area of the Northwest Territories is so large, twice that of France, that it is normally unlikely to see the manifestation of these winter fires. The fact that four plumes of smoke can be seen along the road to Yellowknife speaks to the countless number of fires still burning across the more than a million square kilometers of land.

For now, the phenomenon of winter fires, although impressive, should not be exaggerated. The vast majority of fires are caused by lightning from storms, a small proportion by hibernating fires. The fact remains that this proportion is increasing. “

After the season of 300 wildfires between 2014 and 2015, we saw eight of these fires overwinter

,” continues Mike Westwick,

“but in some jurisdictions, this is happening more and more often. And researchers suggest to us that this phenomenon could get worse.

Also read: Canada: after the summer fires, firefighters want the authorities to get more involved

Climate change at work

Indeed, random lightning, arson and the El Nino phenomenon do not alone explain the intensity of this summer's fires and the increase in winter fires. “

It is always very difficult to link a single event to climate change. But what we do know is that we experienced, before last season, areas of the territory that only received about 30% of the precipitation that we could have expected during the spring. And this, throughout a period when we were already facing drought

,” recalls Mike Westwick.

For the moment, winter fires are subject to increased monitoring by Canadian authorities. They are impossible to extinguish one by one: some burn one meter below the ground, not counting the thick snow cover, and this would require human resources that no country is capable of providing. The objective is therefore to detect the slightest outbreak of fire in the open air, insists the manager: “

We mainly monitor the borders between burned and unburned areas, because that is where the flames can start

”.

The forestry division thus works hand in hand with the provincial firefighters, using reports from human witnesses, satellite images, aerial patrols. Twelve fire surveillance towers, nine of which are automated, also dot the area. The phenomenon is therefore not taken lightly. “

The first fire detected in the Northwest Territories was of underground origin. It launched the most intense fire season in our history

,” recalls Mike Westwick.

Lately, the months of March and April tend to get warmer in Canada, as in the rest of the world. With the risk of causing an earlier and earlier recovery and a lengthening of fire seasons, driven by the phenomenon of winter fires.

Read alsoLosing your forest or modifying it: Canada facing the carbon footprint of fires

Canada: under the snow, the phenomenon of “zombie fires” is already threatening the coming summer

Canada: under the snow, the phenomenon of “zombie fires” is already threatening the coming summer

A phenomenon as old as time

Climate change at work

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