Three ingredients to a wildfire
There are three ingredients to a wildfire, says Flannigan: fuel (trees, grasses, shrubs), ignition (caused by lightning or people) and weather (heat, moisture and wind).
With a sea of boreal forest surrounding the Wood Buffalo region, there’s no shortage of fuel. The cause of the fire is still under investigation, but with no recent lightning activity in the area and the blaze starting in early spring when a lot of fires are caused by humans, Flannigan says it’s likely people were responsible.
In terms of weather, Alberta had a mild, dry winter and spring, likely attributed to El Niño, where warmer than normal temperatures over the Pacific Ocean influence weather elsewhere. A recent El Niño year, 1997–98, was bad for wildfires, Flannigan explains, and so far this year Alberta has had 374 wildfires compared with 173 this time last year (as of May 6).
The day of the evacuation, Fort McMurray saw record temperatures of 32.6 C.
Simply put, the Fort McMurray region had all the ingredients for a raging wildfire.
“Conifers are particularly flammable. The jack pines, the spruces, these burn like stink,” Flannigan says. The heat is so intense some trees are exploding due to superheated gases igniting all at once, like a propane barbecue that’s been left on for a few seconds before igniting, he says.
“It goes ‘womp!’ all at once, and that’s what’s happening to these trees that don’t normally burn very well, because it was so dry and such extreme conditions. Even for typical boreal forest, this was on the extreme end—it’s still on the extreme end because it’s still growing.”
