As spring temperatures rise across northern regions of Canada, an unusual but increasingly familiar wildfire phenomenon is making its return: overwintering wildfires. These fires, which burn silently beneath the snow-covered forest floor through the winter, can reemerge in the spring, reigniting surface vegetation and causing concern for wildfire management authorities.
Overwintering wildfires, also referred to as “zombie fires,” persist underground, smoldering in layers of peat, organic soil, and decaying plant matter. While they may appear extinguished at the surface, the fire’s core remains active, sustained by oxygen and fuel trapped below the frozen surface. As the snowpack melts and soil thaws, these fires can flare up again, sometimes months after they were initially thought to be extinguished.
What Causes Overwintering Wildfires?
Several conditions must align for a wildfire to persist through winter. Most often, overwintering fires originate from intense blazes that burned late into the previous wildfire season. When the ground remains dry and temperatures stay warm late into the autumn, the flames can burn deeper into the forest floor. Once snow begins to fall, the upper layers may insulate the burning material beneath rather than extinguish it, effectively preserving the heat over the cold months.
In regions such as northern British Columbia, where last year’s wildfires were particularly large and intense, this phenomenon is becoming more common. Remote and forest-dense areas provide ample organic matter for fires to consume underground. As the snowpack recedes in spring, smoke and hotspots begin to emerge, triggering monitoring and containment efforts from wildfire crews.
Current Activity and Monitoring
This spring, wildfire authorities in British Columbia have reported multiple overwintering wildfires becoming active again in the northern parts of the province. Smoke has been observed near key transportation routes such as Highway 77 and the Alaska Highway, prompting response teams to assess the potential for fire spread. Although no critical infrastructure is currently at risk, crews remain on alert for changing wind conditions and fuel availability that could expand the fires beyond last year’s boundaries.
Wildfire response officers are actively patrolling burn sites, particularly those near Fort Nelson and along the Fort Nelson River, using aerial surveillance and ground crews to monitor hotspots. The key focus is determining whether these fires will remain confined within previously burned zones or require a larger containment strategy.
How Overwintering Wildfires Differ From Seasonal Wildfires
While seasonal wildfires are typically ignited by lightning, human activity, or dry lightning during warmer months, overwintering wildfires are remnants of past events. Their persistence below the surface makes them harder to detect using conventional monitoring tools. Satellite imagery, infrared scanning, and drone technology have become essential for identifying these underground hotspots early in the season.
Key Differences Include:
- Location: Overwintering fires start below ground, while typical wildfires begin above ground with visible flames.
- Timing: These fires can become active during spring thaw, weeks before new fires usually begin.
- Detection: They are harder to spot and often identified only when smoke appears or soil temperatures are monitored.
- Fuel Source: Overwintering fires consume peat and organic soils, while seasonal fires often feed on dry vegetation and brush.
- Response Strategy: Specialized tools and tactics are needed to suppress underground fires, including deep soil saturation and excavation.
Implications for Wildfire Management
The resurgence of overwintering wildfires highlights the increasing complexity of fire management in northern climates. With climate patterns shifting toward longer, warmer fire seasons, the risk of deep, persistent fires is rising. Firefighting agencies are adapting by conducting extended monitoring into the winter and pre-positioning resources in high-risk areas during spring melt.
Public safety remains a priority, especially for residents living near historical burn areas. Smoke from these fires can reduce visibility along highways and affect air quality, even if the fires themselves are not directly threatening communities or infrastructure. Authorities advise residents and travelers in affected areas to stay informed through local emergency services and wildfire information channels.
Looking Ahead
As climate variability continues to influence fire behavior, overwintering wildfires may become a more regular occurrence. Researchers and wildfire specialists are studying how to better predict and respond to these persistent events. Improved mapping of burn scars, soil composition, and moisture levels may aid in forecasting where overwintering hotspots are most likely to emerge.
While not yet widespread across all forested regions, overwintering wildfires serve as a reminder of the lingering effects of intense fire seasons. Proactive monitoring and public awareness are essential in mitigating the risks associated with these underground threats.