Zombie wildfires are forcing thousands to evacuate in Canada (Credit: Andrei Axenov/ CC-BY-SA-2.0/ BCEHS)

Canada is no stranger to wildfires. However, the 2023 wildfire season was the worst on record. Over 6,500 blazes scorched more than 48 million acres of forest across Canada, a 170 percent increase over 2022. The wildfires finally seemed to die down when the snow arrived, bringing relief to affected communities.

However, as the snow began to melt, a new challenge emerged. Many of the fires had not been fully extinguished. They were simmering under the snow, waiting for warmer weather to reignite. These "zombie" fires have now roared back to life, forcing thousands of people in British Columbia and Alberta to evacuate their homes.

What are "zombie" fires?

Zombie fires get their name because the wildfires seem to come back from the dead. Also known as holdover or overwintering fires, the flames can burn underground for weeks, months, or even years. They are sustained by organic matter such as peat, which is highly flammable. The blazes emerge when the ground is struck by lightning or when farmers set controlled fires to burn excess vegetation.

Zombie fires can remain alive for years (Credit: Sitn.hms.harvard.edu/ CC-BY-SA-4.0)

“When these fuels are exceptionally dry, wildfires smolder in deep duff layers and within large logs, remaining active underground with the potential to resurface come spring,” states Canada’s Wildfire Service.

Are zombie fires a new natural phenomenon?

Zombie fires occur annually in British Columbia and Alberta. However, there are usually no more than 15 each year. But there has been a significant surge this year. Officials estimate that there are currently 93 zombie fires raging in British Columbia and over 55 in Alberta.

Canada's three-year drought has led to a surge in zombie fires (Credit: Agriculture and Ag Food Canada/ CC-BY-SA-4.0)

Experts say that most years, the melting snow goes deep underground and extinguishes the hidden flames. However, British Columbia and Alberta have received less snow than usual for the past three years. The lower precipitation and warmer winter temperatures have enabled the fires to continue simmering in the dense vegetation layers under the snowpack.

Why are firefighters unable to detect zombie fires?

Zombie fires are difficult to detect due to several factors. Firstly, many of these wildfires occur in remote, hard-to-reach forest areas, making them challenging to access. Additionally, the underground fires are mainly flameless. This allows them to spread undetected across large areas of land. While firefighters diligently monitor suspected active areas, the frozen, snow-covered ground often hampers their efforts.

Do zombie fires only occur in Canada?

Zombie fires are not unique to Canada. Alaska, Northern Europe, and Siberia are also prone to zombie fires, as they share similar characteristics. These areas are home to cool coniferous forests, where the ground is covered with a thick layer of needles and other vegetation that burns easily.

Resources: foxweather.com, CNN.com, CBSnews.com, Wikipedia.org