Explained | What is causing large-scale wildfires in Canada?  Premium

According to the Canadian Interagency Forest Fire Centre, there are 426 active fires in the country as on June 8, 2023.

The story so far: New York City’s air quality is currently ranked among the worst in the world due to drifting smoke rising from wildfires in Canada. According to AirNow, areas from the mid-Atlantic through the Northeast and upper parts of the Great Lakes registered air quality in unhealthy or worse categories starting Wednesday. The smoke has now also engulfed Washington D.C. and other parts of the North American continent.

According to the Canadian Interagency Forest Fire Centre, there are 426 active fires in the country as on June 8, 2023. Out of these, 232 were reportedly out of control. A major chunk of these — 144 — were reported from Quebec province alone. The organisation has also raised the national preparedness level, an indicator of wildland fire activity, to its highest level, at five.  

Wildfires in Canada’s British Columbia and Alberta province started in late April, news agency Reuters reported. These have now moved on to the eastern provinces of Quebec, Ontario, and Nova Scotia. Quebec is Canada’s largest province by area, and also home to most currently active wildfires. Most of these have been caused by lightning, the Reuters report added.

Human activities are also to be blamed for adding to the forest fires, reports have said.

According to a study published in Nature journal on February 10, 2023, lightning is the main precursor of natural wildfires. Laboratory experiments and field observations have indicated that continuing electrical currents in lightning flowing for more than some tens of milliseconds (so-called Long-Continuing-Currents, or LCC) are likely to produce fires.

According to the study, simulations suggest an increase in total global lightning and global LCC by the 2090s. The simulated globally averaged surface temperature increases by about 4 Kelvin (since Kelvin and Celsius have a linear relationship, this equals to an increase by about 4 degrees Celsius), and thus we obtain an increase in total lightning activity of 11% per Kelvin.

The estimated increase of LCC lightning over land by 47% indicates a higher risk of lightning-ignited wildfires in the future, the study says. Although the simulated relative increase of the global total lightning flash rate (43%) is similar to the relative increase of the global LCC lightning flash rates (41%), the trends are opposite in some regions including western parts of North America, North and the South of South America, parts of Central Asia, and in the Scandinavian Peninsula. Simulations suggest that in these parts, total lightning decreases, but LCC lightning increases, hence leading to an increase in wildfires.