Dry conditions, lightning contributed to Alberta's record-breaking 2023 wildfire season: study

Wildfires in Alberta last summer burned more area than any previous fire season and a new study shows hot, dry conditions and an unusual amount of fires started by lightning were major contributing factors. 

These findings come from a new study of the 2023 Alberta wildfires, published in the Canadian Journal of Forest Research. 

Jen Beverly, a professor at the University of Alberta and one of the study's authors, says "it's not unusual in Alberta to have a fire season where you have 700, [or] 800,000 hectares burned. Last year it was closer to two million."

She says the fires themselves weren't unusual, but there were more big fires than in a regular fire season. In 2023, there were 36 wildfires that covered 100 square kilometres or more in size. 

Lightning started big wildfires 

Last year's fire season started fierce and many fires in May were caused by lightning. These fires were ignited in dry conditions, before the trees and shrubs in the province's forests had a chance to fully green up. 

Typically, Beverly said, the province gets about one big lightning fire in May per decade. Last year, there were 13. 

"This was a really unusual change in the cause of fires, because normally in the spring, we're worried about people starting fires," she said. 

Beverly said the conditions last spring were dry and crispy. 

"People are really good at starting fires under those conditions," she said. 

"Lightning is even better."

May set the tone for fire season

Josee St-Onge with Alberta Wildfire says the study's findings reflect what she has heard from firefighters.

"We saw a lightning storm in late April that went through the province and ignited multiple wildfires at the same time throughout the province of Alberta, and that set the tone for the rest of the season," she said. 

St-Onge said they "were constantly reacting to new wildfires as opposed to being able to make good progress periodically."

Beverly said fire suppression resources were quickly exhausted in May 2023 because of the number of lightning fires. 

"They have to decide where they're going to put their resources. That means some fires and portions of some fires are not going to get suppression effort. And they may just be left to burn for a period of time," she said. 

Rains, cooler temperatures helped this year 

St-Onge said the number of wildfires this year is similar to the year before. Last year, it was 975. In 2024, it's 1090. 

What's different, she said, is the area burned. 

"At this time last year, we had already crossed the two million hectares threshold and this year we are around 660,000," she said. 

St-Onge credits rain that the province received in May and June this year for this difference.

"There was more of a respite in the spring after those rains came," she said. 

"That allowed firefighters to make some very good progress on the wildfires that had started earlier in the season. And so we didn't find ourselves in the same situation where we were having to battle large wildfires throughout the province during the entire season.

Beverly said the fire season's severity can be assessed using different metrics, and the total area burned is just one way to measure it. 

"We often, as researchers, look at it in terms of the area that was consumed by fire, but severity can also be reflected in any kind of impact. And certainly, any time a community is impacted, that makes it a high severity season."

Climate change could intensify fire seasons

The study notes "severe fire seasons are expected under a heating climate and are consistent with an increasing trend observed in annual area burned in Canada since 1959."

Lori Daniels, a professor at the University of British Columbia who was not involved in the research, said as the climate warms, wildfire seasons will also change.

"Longer fire seasons and early season droughts that clearly are conducive to fire, when they do occur, is one of the predictions that has been made as climate is changing and as our forests become more susceptible to fire." 

She added large fires are more likely when weather conditions are hot and dry and when there are extended droughts.