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I have added a new step to my morning routine. After promptly looking up the weather upon waking, I now check the air quality. If it’s bad, how bad is it and how long might I have to try to avoid it? And if it’s good, how long can I hope to enjoy it? It has only been in the past few years that wildfire smoke from Canada has become a persistent risk to the air we all breathe. Why is this?
Scientific advances achieved way back in the 19th century offer insights. In 1884, Wladimir Köppen, a German-Russian botanist and climatologist, first developed a classification system for climate zones throughout the world. How could he accomplish this when vast areas of the globe still lacked any temperature and precipitation records? To create his maps, Köppen built on research conducted by earlier 19th-century scientists who established a strong link between vegetation and climate. Much work had been accomplished on mapping the dominant vegetation types across the world.
Climate is the culmination of the weather conditions prevailing in an area over a long period of time. Weather can and does vary greatly from day to day, but over decades and centuries certain patterns of temperature and precipitation tend to persist, and vegetation responds accordingly.
A vast swath across northern Canada has a subarctic climate, characterized by long, cold winters and short, cool summers. The types of vegetation best adapted to these conditions are conifer forests dominated by black and white spruce with some pine, balsam fir, larch, aspen and birch.
Fire has always been an element of this biome. Historically, about 7.3 million acres have burned annually but in 2023, an astonishing 67 million acres burned. This year’s acreage is on pace to meet or exceed the record-breaking year of 2023. The wildfire season in Canada is starting earlier and extending longer, and some fires even are overwintering — smoldering underground in thick, peaty soils and then flaring up again if dry weather resumes the following spring.
The fire season is changing in Canada because the climate of Canada is changing. Canada’s north is warming at a rate two to three times the global average. The duration of snow cover is decreasing across much of Canada, with a trend toward earlier spring melts. In short, the subarctic climate that for millennia sustained Canada’s vast boreal forest is quickly changing. Climate and vegetation are no longer in sync — a pattern that is being repeated in many parts of the world as global warming intensifies.
