'Zombie fires' in the Arctic: Canada's extreme wildfire season offers a glimpse of new risks in a warmer, drier future

• Apocalyptic orange skies and air pollution levels that force people indoors only tell part of the story, though.
• As global temperatures rise, fires are also spreading farther north and into the Arctic.
• These underground fires are known as “zombie fires,” and there are a number of reasons to worry about the trend.
• Recent research finds that Arctic soil fires can smolder through the winter and reignite during early spring when temperatures rise, hence the nickname “zombie fires.”

The Arctic is increasingly flammable

• However, the severity, frequency and types of wildfires in northern and Arctic regions have changed in recent decades.
• One major culprit is the rising temperature: The Arctic is warming nearly four times faster than the rest of the world, a phenomenon known as Arctic amplification.
• As the Arctic warms and fires move farther northward, peat soils rich in dead plant material burn at an accelerated rate.
• Northern ecosystems store twice as much carbon in their peat and permafrost as the atmosphere, and both are increasingly vulnerable to fire.

What is a zombie fire?

• Ground fires, on the other hand, do not flame but burn more slowly and have the tendency to spread deep into the ground and spread laterally.
• During the 2019-2020 fire season in Siberia, zombie fires were blamed for rekindling fires the following year.
• They were ignited by slash-and-burn activities to plant palm plantations and amplified by drought conditions during a severe El Niño event.

Some hope and caution from past lessons

• My work and that of many colleagues, however, focus on the combustion of above-ground biomass.
• In the meantime, the continuing waves of wildfire haze in Canada and the U.S. are a reminder of the impact of these fires.
• Best practices for safely fighting zombie fires are also needed, along with better public education about the health risks of wildfire smoke.