Today’s Image of the Day from NASA Earth Observatory features a river of dark smoke flowing from fires in western Canada. On August 11, 2024, the VIIRS (Visible Infrared Imaging Radiometer Suite) on the NOAA-20 satellite detected nearly 100 active fires burning in the Northwest Territories.

Boreal forest fires

“The boreal forests of northern Canada have evolved to burn. These forests are dominated by black spruce, a type of evergreen that is not just tolerant of fire but dependent on it,” noted NASA.

“Black spruce has waxy, resinous needles adapted to ignite during lightning storms and burn vigorously. The forests thrive if they burn every century or so because fires open the canopy up to light, stimulate new growth, and help maintain biodiversity.” 

NASA pointed out that fires also melt the waxy coating on black spruce cones, enabling them to release seeds that are specially adapted to grow in the charred, acidic soils. 

However, in recent decades, Canada’s black spruce boreal forests have experienced more frequent fires, placing even these fire-adapted ecosystems under significant stress.

Fires in the Northwest Territories 

The Canadian government uses hotspot data from the Fire Information for Resource Management System (FIRMS), a fire monitoring system developed by NASA, to help detect and track wildfires.

Most fires in the Northwest Territories occur far from towns or infrastructure, allowing authorities to let many burn out naturally, a process that can take weeks or even months, depending on weather conditions. 

As of August 11, Canadian authorities reported 96 active fires, of which 88 were left to burn without intervention. Firefighters had successfully controlled five fires and were actively working to suppress one more, according to the territory’s government. 

None of the fires posed an immediate threat to settlements, so no evacuation orders were issued. However, dense smoke has led to air quality warnings in fifteen Northwest Territories communities, including those in the North Slave, South Slave, Dehcho, and Sahtu regions.

Drought and heat fueled the fires

The fires coincided with a drought categorized as moderate to extreme by the North American Drought Monitor, as well as a week of extreme heat that broke temperature records across several parts of the Northwest Territories, including Aklavik, Inuvik, Fort McPherson, and Tuktoyaktuk. 

All four communities experienced temperatures exceeding 30 degrees Celsius (86 degrees Fahrenheit), with Fort McPherson reaching a notable 34.9°C (94.8°F) on August 7 and 8.

Some forests are struggling to recover

Although black spruce forests in Canada are adapted to fire, ecologists studying the region are observing that some forests are struggling to recover due to the increasing frequency and intensity of fires. 

A study led by Jennifer Baltzer, an ecologist at Wilfrid Laurier University, revealed that black spruce regeneration has declined at 38 percent of 1,500 recently burned sites studied, with complete regeneration failure at 18 percent of the sites – figures that are unusually high compared to historical norms. 

This analysis was based on tree regeneration data collected and examined as part of NASA’s Arctic-Boreal Vulnerability Experiment (ABoVE).

Many of the areas affected in this image also burned in 2023, during Canada’s worst wildfire season on record. However, data from Canadian authorities indicate that the total number of fires and the hectares burned in the Northwest Territories through mid-August 2024 are below the 10-year average. 

In contrast, the extent of burning in neighboring British Columbia and Alberta during the same period is above average.

Image Credit: NASA Earth Observatory 

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