Zombie Fires: The Wildfires That Refuse to Stay Dead

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8 min read

Picture a wildfire season ending the way they always do. The smoke clears, the flames die down, firefighters pack up their gear, and snow eventually blankets the scorched forest. Case closed, right? Not always. In parts of the Arctic and boreal North, some fires never actually go out. They simply retreat underground, tucking themselves into layers of soggy, carbon-rich peat, and wait out the winter in a smoldering, flameless state. Then, when the snow melts and the ground warms again in spring, they climb back to the surface and start burning as if no time had passed at all.

Scientists call this phenomenon an overwintering fire, though the nickname that stuck is far more memorable: a zombie fire. It sounds like something out of a horror movie, and in a way, that is fitting. These fires really do rise from what looks like a dead landscape, and they are becoming an increasingly serious concern as the planet warms.

What Exactly Is a Zombie Fire

A zombie fire begins its life as an ordinary wildfire, sparked by lightning or human activity during a hot, dry summer in a boreal forest or Arctic tundra region. Boreal forests stretch across northern Canada, Alaska, Scandinavia, and Siberia, and beneath much of that forest floor sits a thick layer of peat, which is partially decomposed plant material that has been accumulating for thousands of years. Peat is spongy, packed with organic carbon, and able to hold enormous amounts of moisture, but it can also burn in a very different way than a tree or a patch of dry grass.

Instead of flaming and racing across the landscape the way surface fires do, peat burns through a process called smoldering combustion. This is slow, flameless, low-temperature burning that creeps through the fuel rather than consuming it in a rush. A smoldering fire can sink several feet into the ground, insulated from the freezing air above by layers of snow and soil.

Researchers describing overwintering peat fires in Russia's boreal forests have documented this exact pattern, with smoldering fires persisting underground through the entire winter before reigniting the following spring. Because the fire is buried, it is largely shielded from the punishing cold of an Arctic winter. The surrounding snowpack actually works like insulation, trapping just enough heat for the smolder to keep going at a very slow burn, sometimes releasing faint wisps of steam that rise up through cracks in the frozen ground. Firefighting crews and Indigenous land observers have occasionally spotted this steam curling up from a snow-covered forest floor in the dead of winter, a strange and eerie sign that something is still alive beneath the frost.

The Permafrost Connection

Zombie fires are closely tied to another feature of the far north: permafrost, the layer of ground that stays frozen for two or more consecutive years. Permafrost can extend hundreds of meters deep and often contains ancient organic material, including long-frozen plants and even animal remains, locked away like a time capsule. As the Arctic warms at more than twice the global average rate, permafrost is thawing decades ahead of earlier scientific predictions.

That thawing matters enormously for zombie fires. When permafrost melts, it releases methane, a highly flammable gas that had been trapped in the frozen ground for centuries. That methane can seep upward and effectively feed a smoldering fire from below, helping it survive the winter and even allowing it to burrow deeper underground rather than staying near the surface. This creates a troubling feedback loop. A warmer Arctic thaws more permafrost, which releases more methane and carbon dioxide, which traps more heat in the atmosphere, which in turn drives further warming and creates the ideal conditions for more zombie fires the following year. Scientists at organizations including the World Wildlife Fund have specifically flagged this cycle as one of the most concerning aspects of Arctic warming, since it turns a regional wildfire problem into a global climate issue.

How Common Are They Really?

For a long time, zombie fires were considered a rare curiosity rather than a major driver of wildfire activity. A widely cited study covering Alaska and the Northwest Territories between 2002 and 2018 found that overwintering fires accounted for well under 1% of the total area burned by all wildfires in that period. That is a small slice of the overall picture, but the trend line matters more than the raw percentage. Researchers studying the Northwest Territories found that zombie fires consistently emerged the spring after each of the region's hottest summers on record, and that none appeared following the coolest summers. That pattern gave scientists strong evidence that overwintering fires track closely with heat and drought rather than occurring randomly.

The trend has accelerated sharply in recent fire seasons. Canada's catastrophic 2023 wildfire season burned more than 17 million hectares, roughly four times the area burned in 2014, and the following winter researchers tracked around 150 separate overwintering fires smoldering across the western part of the country, the highest number ever recorded there. Some of those zombie fires are believed to have fed directly into the massive blazes that forced thousands of residents to evacuate communities like Fort Nelson, British Columbia, the following year. A newly published 2026 study using Landsat satellite imagery to analyze reburning patterns in boreal North America found that the overwhelming majority of these overwintering fires reignite within about 500 meters of the previous year's fire perimeter, which means they tend to expand a burn scar outward rather than spark somewhere entirely new.

Russia's Far North has seen similarly dramatic numbers. In some recent fire seasons, Russia's Eastern Federal District has emitted several hundred megatonnes of carbon dioxide from wildfire activity, a total that surpassed every previous year on record for that dataset. Researchers cataloging overwintering peat fires in Russia's Sverdlovsk region during the winters of 2022 through 2024 confirmed dozens of smoldering hotspots using a combination of satellite imagery, ground surveys, and reports from local firefighting crews.

Hunting Ghosts From Space

Detecting a fire that is deliberately hiding underneath snow and frozen soil is an unusual scientific challenge, and it has pushed researchers to get creative. Standard fire-detection satellites, which typically look for the intense heat signature of an active flame, often cannot see a smoldering peat fire buried beneath a thick blanket of snow. Instead, scientists rely on a combination of tools to catch these fires in the act of waking up.

One major resource is the Copernicus Atmosphere Monitoring Service, which uses Europe's Sentinel satellite network, along with data from NASA's Terra and Landsat missions, to track daily wildfire and biomass-burning emissions worldwide. By comparing the exact location of a fire that flares up in spring against the mapped boundary of a fire from the previous summer, scientists can flag a likely zombie fire and prioritize it for further investigation. This kind of remote sensing detective work first put the phenomenon on the scientific map when a researcher at the Vrije Universiteit Amsterdam noticed strange, isolated flecks of fire on satellite images from Alaska in May of 2016, weeks before the region's normal fire season should have even started.

Because clouds, snow cover, and frozen soil can all interfere with satellite readings, researchers are increasingly combining multiple types of instruments, including visible light, infrared, and microwave sensors, to build a clearer picture of what is happening underground. Ground teams still play an essential role too. In Alaska, one overwintering fire near the town of Willow was confirmed by technicians who traveled out on snowmobiles to check a suspicious satellite anomaly in person.

Why Scientists Are Genuinely Worried

The concern surrounding zombie fires goes well beyond the fires themselves. Boreal forest soil, particularly the deep peat layers where these fires like to hide, stores an extraordinary amount of carbon. Researchers estimate that boreal soils collectively hold roughly as much carbon as Earth's entire atmosphere, if not close to double that amount. When a zombie fire reignites and burns through that peat, it releases carbon that has been locked away for centuries or even millennia, adding it back into the atmosphere in a matter of weeks.

There is also a growing body of research on how these fires affect the wider ecosystem. A 2025 study published in CATENA examined how underground wildfire activity damages plant root systems in peat soil, altering how the land recovers and regrows in the years after a burn. Other recent research published in Environmental Science and Technology has focused on how Arctic and boreal wildfires release ancient carbon and light-absorbing soot particles that can settle on snow and ice, darkening those surfaces and causing them to absorb more heat from the sun rather than reflecting it away, which accelerates melting even further. A separate 2025 study in Scientific Reports projected that peatland fires in Alaska could roughly double in frequency by the end of the century if current warming trends continue.

None of this is happening in isolation. A 2026 study in Nature Climate Change examined how shifting wildfire risk under climate change threatens species across ecosystems, and Arctic and boreal environments, already home to caribou, migratory birds, and countless smaller organisms adapted to a very specific and fragile habitat, are among the regions facing the fastest rate of change.

What Firefighters Can and Cannot Do

One of the most frustrating aspects of zombie fires for wildfire management teams is how difficult they are to fully extinguish. Because the fire is burning slowly through dense, moisture-retentive peat rather than across the surface, dousing the visible smoke or steam does very little. The smoldering front can simply continue at a different depth or shift slightly to the side, re-emerging weeks or months later somewhere nearby.

In extremely remote sections of boreal forest, far from any town or piece of critical infrastructure, fire agencies sometimes make the difficult decision to let a fire burn itself out naturally rather than risk sending crews into dangerous, roadless terrain. That decision carries real trade-offs, since even a fire that poses no immediate threat to people still releases significant carbon and can set the stage for the following year's fire season. Where resources allow, crews use tools like fire breaks, targeted digging, and prolonged monitoring throughout the winter months to try to catch a fire before it can spread into new peat.

The Bottom Line

Zombie fires are a small but rapidly growing piece of a much larger story about how climate change is reshaping the Arctic. They are not villains acting alone, but rather a symptom of hotter summers, thawing permafrost, and drier landscapes working together to keep fire alive in places and seasons where it once had no chance of surviving. Understanding how they work, and investing in the satellite technology and fieldwork needed to track them, gives scientists a genuine head start on predicting where the next major wildfire season might ignite before a single flame is even visible above the snow.

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