How wildfires are changing in Canada

The wildfires raging in many parts of Canada this spring are part of an overall increase in more powerful blazes, experts say. But the details behind this trend are more complex than just counting the fires, or damage done, per year. 

CBC News reviewed historical data to get a sense of the changing nature of wildfires, and the role of climate change, in the country. (Canada started collecting wildfire data in 1950, though that first decade's is thought to be less reliable.)

The first chart shows that the number of annual wildfires has, in fact, been declining since the '80s.

Experts attribute that to improved fire prevention — so the number of human-caused fires is going down.

This is thanks to better education and fire bans, says Mike Flannigan of Thompson Rivers University in Kamloops, B.C., one of the country's foremost experts on wildfires, who also reviewed the data.

At the same time, the fires that break out now tend to burn more territory. Overall, the area burned annually by wildland fires has more than doubled since the 1970s, according to a recent federal report. 

The next chart shows the number of burned hectares by decade.

The trend is "not just a straight line. It's a bumpy path," Flannigan stressed.

"There is a large year-to-year variability because of weather and ignition." 

The recipe for a wildfire has three ingredients — ignition (either lightning or humans), fuel (dried grasses, shrubs, trees and other vegetation) and dry weather, he says.

But the particulars of those three ingredients are changing, along with the climate.  

In Canada, roughly half of all fires are now caused by lightning. But lightning strikes are on the rise and expected to further increase with climate change.

Because of climate change, the vegetation is more likely to be dry and more flammable.

"As the temperature increases, the ability of the atmosphere to suck moisture out of the fuel increases almost exponentially," said Flannigan. 

"Unless you get more rain to compensate for this drying effect from the warming, you end up with drier fuels. And this is a really critical aspect of the fire world."

In addition, for years, many jurisdictions have focused on putting out fires that would have reduced the accumulation of dry organic matter.

Finally, that same hot and dry weather — particularly on windy days — contributes to the likelihood of wildfire spreading more widely. 

The disastrous 2016 fire in Fort McMurray, Alta., for example, came as an an unusually hot and dry system settled over northern Alberta that May.

The opposite is also true. For instance, between 2000 and 2009 it was unusually cool in the Northwest Territories, which led to a lower overall burned area, Flannigan said.

In general, fires are also happening earlier in the year due to the increasingly early spring thaw and ending later in the year, Flannigan says. He was one of the authors of a 2019 study that concluded, overall, Canada's fire season has been starting approximately one week earlier and ending one week later.

Generally speaking, a rise in major fires has also led to more evacuations, given the fires' growing size and the growing population. The next chart shows the rise in people displaced by fires. 

The Fort McMurray fire displaced 80,000 people — the largest evacuation in Canadian history.

Such fires also can threaten critical infrastructure, such as power lines and major industrial sites like the oilsands, says Kelsey Copes-Gerbitz, a postdoctoral fire researcher at University of British Columbia who also reviewed the data.

Lastly, experts use another category, "fire disasters," to indicate especially significant fires.

Fire disasters must meet at least one of these conditions: 

• 10 or more people killed.
• 100 or more people injured, relocated, infected, displaced or homeless.
• Authorities appeal for national or international assistance.
• Historical significance.
• Causes significant damage to a community.

Fire disasters are on the rise, with more than three times as many between 2010-19 and the three decades prior.

Overall, the period covered by the data was when Canada tried, for the most part, to suppress all wildfires, Copes-Gerbitz says.

That policy, in fact, made our forests more vulnerable to extreme fire because of an accumulation of dry organic matter and older trees, she said.

Now, she said, "climate change is really pushing us to a place where we can no longer suppress all fires and be guaranteed in our success for suppression."

Experts say improved fire management through, for instance, allowing some fires to burn, and increasing the number of prescribed burns (such as Indigenous cultural burns), would help reduce the number of out-of-control, large-scale fires.

An increased emphasis on community-level fire safety, and better oversight of what kind of trees are planted (some better resist, or recover from, fires for instance) would also help. 

"That kind of approach will help us reduce the area that a fire can burn," said Copes-Gerbitz.

Is the weather normally like this in June? Check the CBC News Climate Dashboard to find out how today's temperatures compare to historical trends.

You can search for your town or city and add it as a favourite. Come back daily to see how current conditions and forecasts diverge from previous years.