As Ontario continues to experience its worst fire season on record, new research from McGill University reaffirms that aspen trees can act as a fire barrier. The before-and-after images showed that larger patches of aspen were more prevalent at the perimeters of burned out areas. Pelletier said there are a couple theories as to why patches of aspen can act as a fire barrier. (Jonathan Migneault/CBC)'War against aspen'While aspen can help contain wildfires, Pelletier said "there's kind of a war against aspen in commercial forests." As for whether wildfire smoke from forests sprayed with glyphosate is more toxic, Pinto said the effect would be negligible.