Canada is having its worst fire season in modern history. The fires have burnt more than 20 million acres, casting hazardous smoke over parts of the U.S. and stretching Canadian firefighting resources thin.

Public officials and news headlines have declared the fires as "unprecedented," and in the modern-sense they are. But researchers who focus on the history of wildfire in Canada's boreal forests say the situation is not without precedent.

"Right now, I'm not alarmed by what's happening," said Julie Pascale, a PHD student at the Forest Research Institute at the University of Quebec in Abitibi Témiscamingue, in northwest Quebec. "Years like this happen and happened."

Canada's boreal forests have a long history of major wildfires, research shows. In fact, scientists believe the country's boreal forests burned more in the past than they do today.

"I understand that the current fire situation is like, 'Wow!' but the reality is fire is part of the ecosystem," said Miguel Montaro Girona, a professor at the University of Quebec in Abitibi Témiscamingue. Many of the tree and animal species in the country's boreal forests depend on wildfire. Montaro Girona explained that as massive as the current wildfires are, they are still in the "range of variability," for Canada's forests.

That's not to say that climate change isn't a concern, Montaro Girona said. Human activities have released massive amounts of climate-warming gasses into the Earth's atmosphere, causing the world's temperature to rise. Hotter temperatures are fueling more intense wildfires and lengthening fire seasons globally.

Normand Lacour, a fire behavior specialist with Quebec's fire prevention agency said he's seen wildfire seasons lengthen by about six weeks since he started his firefighting career 35 years ago — a trend that he expects to continue.

"If we want to predict the future we need to know how our activities and the climate has affected fires in the past," Pascale said.

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This episode was produced by Carly Rubin. It was edited by Sadie Babits and Rebecca Ramirez. The audio engineer was Maggie Luthar.