Temperatures throughout Canada’s forests are rising fast because of human-caused global climate change, leaving researchers increasingly worried about the potential for longer, more deadly forest fire seasons in the near future.
One of the under-reported consequences of forest fires is their impact on air quality. In many cases, communities several hundreds of kilometers downwind from a major fire can suffer smoke-filled skies that blot out the sun and cause respiratory distress for weeks at a time. Tell this to residents of Calgary Alberta, who have so far endured 321 hours of smoky conditions in 2017—by far the most smoky hours observed in a year since air-quality records began in 1953. With new and dangerous fires now burning in Waterton Lakes, in southwestern Alberta, this number is expected to keep rising.
Why do warmer temperatures lead to more forest fires?
Warmer temperatures lead to more evaporation from the surface, leaving forests drier and more fire-prone. Warmer temperatures can also lead to more severe thunderstorms capable of producing lightning, the chief cause of forest fires in remote areas. According to fire researcher Mike Flannigan from the University of Victoria, for every 1 °C increase in temperature rise the boreal forest region will experience 12% more cloud-to-ground lightning strikes, on average. Finally, there is growing evidence that climate change is causing the jet stream to slow down and meander much more than it normally would, promoting larger swings between much wetter and much drier conditions. This, in turn, can lead to both more severe flooding and more severe forest fires—often back to back.
Humans are interfering with the natural fire cycle
Rising global temperatures are not the only way humans are impacting the natural fire cycle. More than half of all wildland (forest and grassland) fires in Canada are sparked by humans, typically from off-road vehicles and poorly-managed campfires. The devastating 2016 Fort McMurray fire, which grew to the size of Prince Edward Island, was ruled human-caused.
Interestingly, humans also impact the natural fire cycle by preventing fires. Many wild fires are extinguished as quickly as possible by fire fighters, especially if they are within range of human settlements or popular recreation spots. This promotes the development of older trees and more dead twig and leaf litter on forest floors in and around cities and towns, escalating the risk that a more extreme fire will occur in the future. In many places, fire managers use controlled burns to remove some of this material; however, it is inevitably the case that some of these purposely-lit fires escape.
What can be done?
Fortunately, there are several actions individuals and municipalities can take to reduce fire risk. For starters, structures can be built using Fire Smart principles. Municipalities can build a fire-buffer around their communities by bulldozing trees and removing built-up forest litter. Better public education and better enforcement of backcountry fire bans can also reduce the number of human-caused fires. Finally, remote fires can be allowed to ‘run their course’ to remove built-up twigs and forest debris.
Prairie Climate Centre