Biosphere Climate Change Daily Earth Science Environment Repost

Wildfires and zombie fires

Climate warming is the result of increasing heat content in the planet’s atmosphere and oceans. Because heat is an enabler of regional climate change, it affects not only temperatures but weather patterns also. Warmer air holds more moisture, thus increasing rainfall in some areas. But as weather patterns shift, the regions receiving rain change. Areas that receive more heat and the same (or less) precipitation find themselves exposed to increasing wildfire risk, and when conditions are right, zombie fires become an ongoing threat.

Most wildfires ravage the forests and grasslands in their path and then move on as their fuel source burns away. But fuel is the key to understanding zombie fires. Forests, peatlands, and grasslands in the northern latitudes develop under cool, damp conditions. So, bacterial decay is inhibited in these conditions, and thus the soils of these regions (particularly peatlands) are high organic content.  Remember, the carbon within preserved organic material is what makes fossil fuels useful. Coal is a prime example of preserved plant material that can be dug up and used for fuel.

When peat or other organic-rich soils dry out, then the preserved carbon can ignite and burn. Wet peatlands within boreal forests are usually natural fire breaks. However, when the peatlands dry out, they then become zones of fire propagation, not fire breaks.

If conditions are dry enough, then highly organic soils below a wildfire will also start to burn. But the fire won’t necessarily remain on the surface. The fire can make its way underground and then maintain a long, slow burn. As global temperatures rise, the peatlands around the edge of the Arctic are drying out and increasingly exposed to wildfires and associated zombie fires.

Burning coal seams 

The town of Centralia Pennsylvania began a descent into hell about 60 years ago when a coal seam that lies beneath the town caught on fire. The fire initially started when the city tried to clean up a garbage dump by burning it over. The fire then escaped underground into abandoned coal mines. From 1962 to 1980, state and federal agencies tried in vain to put the fire out, but finally, they gave up and started relocating residents of the town. 

As the underground fires burn, holes open up in the earth’s surface, letting poisonous gases vent into the atmosphere. These hellish fire pits gobble up trees, roads, and houses. The fires have burned for 58 years and could continue burning for another 250 years before they consume all of the local coal.

The Centralia experience is not unique. Around the globe, thousands of these hidden, underground fires burn out of control. Although the Centralia fire was sparked by human activity, that is not always the case. Natural events like lightning strikes or wildfires can also spark an underground coal fire. The coal fires at Australia’s Burning Mountain (Mount Wingen) are estimated to have burned for 6,000 years. Worldwide these underground fires are estimated to contribute about one percent of the total CO2 emissions related to human activity.

Zombie Fires

The basic chemistry behind coal fires also applies to zombie fires. Densely packed organic materials ignite at the surface and then creep underground, where a low oxygen environment lets the fire smolder and simmer for decades or even centuries. Zombie fires in the boreal peatlands originate from a similar process, and the underground fires smolder throughout the winter. When warm weather returns, these fires resurface and then start new wildfires.

Siberia experienced a heatwave this spring. As temperatures increased, so did evapotranspiration, thus sucking moisture from the soils and drying them out. Scientists suspected zombie fires at work as satellite images detected an outbreak of fresh wildfires associate with this heatwave. Many of these fires occur in areas that burned last year, making underground zombie fires the likely culprit.

Increasing regional temperatures without increased precipitation is a recipe for drought, wildfires, and possibly zombie fires. It is all part of a changing planet.


Hot weather in 2020 (Source: ArcheanWeb) –  Also:

Water loss and plant biology: The demise of boreal peatlands (Source: ArcheanWeb) –  Also:


‘Zombie fires’ are erupting in Alaska and likely Siberia, signaling severe Arctic fire season may lie ahead (By  Andrew Freedman; Washington Post) –  Also:

Fire in the Hole (Kevin Krajick; Smithsonian Magazine) –  Also

Feature Image: Northwest Crown Fire (Modified) – By (Photograph used by permission of the USDA Forest Service.) – Bunk S: World on Fire. PLoS Biol 2/2/2004: e54. doi:10.1371/journal.pbio.0020054.g001, CC BY 2.5,

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.