As Canada is once again in the midst of a harsh wildfire season, a new study out of McGill University has shown that aspen trees can act as effective barriers to wildfires.
It’s a phenomenon that Indigenous Peoples and local foresters have long been aware of, says the study’s lead author and recent PhD graduate, Flavie Pelletier. But Pelletier wanted to provide scientific data to confirm existing anecdotal knowledge about the tree’s fire-resisting properties to influence legislation that protects our forests.
The impetus behind the study came from an article Pelletier read about a commercial forest management practice where aspens are sprayed with a herbicide called glyphosate to prohibit their growth in favour of more valuable conifers, such as spruces, firs, and pines. But as forest fires become more common and increasingly devastating, these would-be aspens could play a key role in minimizing their damage.
Pelletier, who is a remote sensing specialist, set out to confirm this long-held knowledge using satellite technology. “I had mapped a lot of fires, especially after the 2023 fire year, and the Canadian Forest Service recently came out with a data set of dominant tree species across Canada,” she says. “So, I basically combined my fire maps with this new data to see which tree species were inside the burn perimeters, but more importantly, which were along the burn perimeters.”
What she found was that aspens were more than two times more likely to be found at the edge of forest fire burn areas than inside them, indicating that they play a role in containing the blaze.
As for why this happens, Pelletier says it’s not entirely known, but that there are theories. “There’s high moisture content in aspen leaves, as well as the understory around it,” she says. “They also produce sap instead of the more flammable resin produced by conifers, and their leaves usually start pretty high up, so if there’s a ground fire, it will be harder for aspen to catch.” However, Pelletier’s findings show that lone aspens aren’t as effective as aspen clusters at stopping the progression of forest fires.
Now that she has proven the fire-stopping capabilities of aspens, Pelletier hopes her work will lead to reduced glyphosate spraying as well as enhanced forest fire protections. “It would be good practice to implement more aspen fuel breaks around vulnerable communities or vulnerable infrastructure,” she says. “If you have a cottage near forest fire regions, it’s not a bad idea to plant a bunch of aspen around your property, because there’s a better chance it’s going to stop a fire than if you have just coniferous trees.”
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