Its name sounds like the title of a crappy Saturday afternoon movie, but the “zombie fires” – remnants or hibernators, as the experts prefer to call them – have little joke and, in their own way, something does resemble the “undead” from ‘The Walking Dead’. Basically they are forest fires that are registered in the extreme north of the Earth, but with a peculiarity: time after being considered extinct, after months or even years, they re-emerge just like the deceased who came back to life in George A. Romero’s film. Its impact is not limited to the damage that can be caused by the flames in its path; It is also linked to global warming.
As in the rest of the planet, forest fires can break out in certain regions of the Arctic, such as boreal forestsdue to natural or man-made causes. In the case of “zombie fires”, however, there is a striking feature: in addition to devouring the vegetation on the surface, the combustion ends up penetrating the soil and reaching accumulations of organic materials, especially the large reserves of peat.
an underground fire
Thanks to this subterranean “food”, generous in carbon, combustion continues hidden from view, extending in depth and throughout the land. The speed at which it advances is largely determined by the amount of oxygen available in each case, but researchers who have dedicated themselves to studying the phenomenon have already verified that —at low temperatures, without the presence of a flame— it can burn peat for Several months. Even years.
When the “zombie fire” encounters layers of water or materials that it cannot “feed” on, it stops. Often, however, the surface does offer fuel after thawing. If that happens, the flames are reborn just like the best “living dead” in Hollywood. Even in a different place from the initial fire and after a long period in which the ground was covered by a thick blanket of snow. As scientists have verified, the phenomenon usually occurs after hot summers that reduce the ice and make it easier for the peat to dry out.
Last year a group of scientists published in Nature a study prepared after analyzing “zombie fires” located in northern regions, such as Alaska or northwestern Canada, between 2002 and 2018, and concluded that they had been responsible for 0.8% of all the burned land and the 0.5% of carbon emissions released. These are small percentages, but enough to warn about the phenomenon – in 2008, in fact, a single “zombie fire” burned more than 130 km2 in Alaska, which represented 38% of all the land devastated by fire that same year in the country—and, above all, how it can be increased with climate change.
Throughout their study, the researchers observed how those years with temperatures above average were usually associated with an increase in “zombie fires”. In fact, they recorded cases in the winters that followed the hottest summers in the Northwest Territories. The question is: why should we worry about more such fires? Well, because they are linked to one of the great challenges of humanity: climate change. So much, in fact, that it represents both a consequence and a factor that favors it.
Beyond the damage caused by the flames on the surface and the devastation of the vegetation, the “zombie fires” advance in lands that are very rich in carbon and end up releasing CO2 into the atmosphere. Peatlands are in fact the most carbon-dense ecosystems on Earth and about half of the carbon they store is located between altitudes of 60 and 70º north, along the arctic circle. In addition to carbon, underground fires also expel methane – present in the soil -, a powerful greenhouse gas that contributes to global warming.
Rising temperatures reduce ice cover and favor ideal conditions for the advancement of these fires worthy of the films of A. Romero. Result: a dynamic that somewhat resembles whiting biting its own tail. The less ice cover, the greater the absorbed radiation, the greater the increase in temperatures, the greater the loss of ice and the greater incidence of fires in the Arctic that end up releasing CO2 and methane into the atmosphere.
A recent study carried out by a group of researchers led by Kimberley Miner, from the Jet Propulsion Laboratory of the California Institute of Technology (USA), warns that underground fires could release carbon stored in areas that until recently were believed to be resistant to the fire And alert: according to your calculationsAs the climate warms, Arctic wildfires could increase exponentially by mid-century.
Images | US Fish and Wildlife Service Northeast Region (Wikipedia) and Unsplash