How Climate Change Is Fueling the World's Longest-Burning Fires

Peat is the stuff of bogs and wetlands; it gives rise to our swamp things and our Scotch. But peat burns, and to ugly effect. It doesn't burst into flames so much as smolder—instead of towering fires, it produces thick walls of foggy smoke. These fires are already the largest in the world in terms of carbon output, and, in a category they share with coal blazes, they are the longest-lasting. 'Smoldering fires' can go on for years.

Now, new research published in Nature Geoscience indicates that in the age of climate change, vast swaths of the world's peatlands are poised for ignition.

The thrust of the study is fairly straightforward: climate change is warming and drying out peat-filled regions around the world. Meanwhile, thirsty humans are lowering water levels, and both factors are making peatlands much more likely to be set asmolder. It's a similar phenomenon we're seeing with typical wildfires, with a few crucial—and disconcerting—differences.

"Peat fires, once established, are extremely difficult to control, and notoriously difficult to extinguish," the ​Desert Research Institute's Dr. Adam Watts, one of the authors of the study, told me. Because the smoldering occurs in underground peat layers, the fires can endure weather that would douse other fires, and even survive winters. "Once they start, it really takes an act of nature to extinguish them."

This, of course, poses a host of problems to the planet and its populations. Peat covers 3 percent of the planet's land surface, and contains a full quarter of the world's soil carbon.

There's peat on all seven continents. There's peat in ​Norway, there's peat in Indonesia—there's a lot of peat in Indonesia—and there's peat in the United States. You've probably walked through it, if you've been to Florida; America's most famous peatland is the Everglades. In fact, peatlands are, ​according to the experts, "the most widespread of all wetland types in the world, representing 50 to 70 percent of global wetlands."

The ecosystem also happens to be, as another recent study explains, the "most efficient carbon sink on the planet." Which is precisely why Watts and his colleagues are worried.

"Globally, the amount of carbon stored in peats exceeds that stored in vegetation and is similar in size to the current atmospheric carbon pool," the authors of the Nature study write. Let that sink in for a second; there is about as much carbon in the world's peatlands—the bogs, swamps, and mosslands—as there currently is in the sky. And humanity, as we known has spewed a lot of carbon into the air.

Smoldering poses an imminent threat, despite the intrinsic dampness of peat. "Peat fires are dominated by smoldering combustion, which is ignited more readily than flaming combustion and can persist in wet conditions," the authors write. And man, can they persist.

"Because of the easy ignition and difficult suppression, smoldering is the most persistent type of combustion phenomena on Earth," ​Dr. Guillermo Rein, another author of the study, an expert on these kinds of fires, and the editor-in-chief of the science journal Fire Technology, told me in an email. "Smoldering fires burn for very long periods of time (e.g. months, years, decades) despite extensive rains, weather changes and fire-fighting attempts."

As one of the top scientists in the field, he's seen many up close—aboveground, anyway.

"Indeed, the oldest continuously burning fire on Earth is the Burning Mountain in New South Wales, Australia, a large coal seam that has been smoldering for approximately 6,000 years," Rein said. "It is the best example of smoldering fire that slowly burns the underground coal when it becomes exposed to atmospheric air." He ​visited the site last year, and sent along a couple photos from his trip.

The man who discovered that there was an ongoing smolder under the mountain, Rein notes, remarked that it had been burning "far preceding the memory of man."

And yes, Burning Mountain is a coal seam fire. Climate change is ripening conditions for the peat fire's ugly, pure-carbon cousin as well.

"Coal fire is another smoldering phenomenon that shares many similarities with peat fires," Rein said. As with peat, "[b]oth climate change and human development can lead to more coal fires." This is because, he said, the carbon emissions from smoldering coal can lead to warmer and drier soils—thus, coal seams become more vulnerable to catching fire. "Second," he said, "continuous underground exploration and exploitation of coal deposits leads to more and more coal seams becoming exposed to air, which is a condition for smoldering combustion."

One of the primary jobs of a coal miner is to clear a path through the earth to the coal seams—which, incidentally, leaves them exposed and vulnerable to both surface fires and underground pyrotechnics. In 1962, for instance, America's most famous coal conflagration was lit when someone started a trash fire in a dump in Centralia, Pennsylvania, and it inadvertently spread to an open coal seam nearby. It has been smoldering ever since, and now Centralia is a ghost town.

These sorts of subsurface fires are ​especially rampant in China, where coal mining is ubiquitous and regulations are weak. One ​2008 report found that coal seam fires in Northern China alone accounted for 3 percent of global carbon emissions. The amount of coal inadvertently burned underground in China, estimated to be between 20 and 100 million tons annually, was as much as industrious Germany burned intentionally.

"I think we should expect more coal and peat fires in the future," Dr. Rein said.

Like coal mining, irresponsible agriculture is beckoning more smoldering fires. In addition to climate change, human activity—developing land for agriculture, or residential areas—is clearing the way for more smolder. See, "In undisturbed peatlands, most of the peat carbon stock typically is protected from smoldering, and resistance to fire has led to a build-up of peat carbon storage in boreal and tropical regions over long timescales," the study explains. But climate change is drying them out, and humans are draining the local water reserves—and starting more fires.

When peat smolders, it's burning stuff that hasn't been burned for hundreds or even thousands of years: "The combustion of deep peat affects older soil carbon that has not been part of the active carbon cycle for centuries to millennia."

"The regions were ecosystems are most vulnerable to peat fires are the permafrost soils in Alaska and Siberia," Rein said. Not coincidentally, Arctic regions are seeing some of the world's most rapid warming, and scientists are especially worried about ​the methane-rich permafrost that's beginning to thaw. "These soils have not been exposed to fire in millennia but warming is making them susceptible to smoldering combustion.

Such climate-abetted peat burning has notably racked Indonesia, where, in 1997, farmers in Kalimantan and Sumatra adopted a disastrous slash-and-burn agricultural approach that accidentally lit a slew of peat fires. The resultant event, known as the ​1997 Southeast Asian Haze, shrouded 1.2 million square miles in fire-fog, impeded air travel to the region, and spurred an air quality crisis across the continent. It also belched out ​up to 2.57 gigatons of carbon—or 40 percent of the amount emitted by fossil fuel burning that year.

But today, even after with hard lesson about slash-and-burn learned, and even in non-drought years, smoldering peat fires are engendering "episodes of extreme air pollution."

The authors of another Nature study on Sumatran fires in 2013 determined that "the greenhouse gas emissions during this brief, localized event were considerable… representing 5–10 percent of Indonesia's mean annual GHG emissions for 2000–2005." The researchers concluded that such episodes "in Southeast Asia are no longer restricted to drought years. We expect major haze events to be increasingly frequent because of ongoing deforestation of Indonesian peatlands."

It's an unfortunately apt example of the plight Watts and his colleagues are cataloging. So are ​the devastating 2010 peat fires that snarled Moscow in acrid smoke, killed scores of citizens, and did untold amounts of property damage. There will, sadly, likely be more examples before too long.

Then come the feedback loops. When peat smolders, it has effects far beyond the local region where it burns. In the north, peat smoldering can lead to longer seasons and longer frost-free periods, Watts said.

"And of course to further carbon release from those fires," he adds. In other words, the more carbon gets expelled from peat, the more climate change exposes more peat for smoldering, and thus, the more peat smolders.

To put it simply, we don't really want to live in a world overcome with smoldering fires.

"Not affected by weather, typical forest fires—flaming fires are very highly affected by weather—but if you get a peat fire with no wind, that poses a huge concern with smoke production," Watts said.

Sometimes, you'll even get what Watts calls "super fog," in which ​a combination of moisture and dense smoke will create very low visibility. If you've driven in the South, where i​t's more common, you might have ​trudged through its tendrils before.

Of course, smoldering isn't healthy, either. "The smoldering combustion—you can analogize that to cigarettes," he said. "They produce a lot of particulate matter that can enter the lungs. Smoldering is a very dirty form of combustion, and the particulate matter can be wafted into the regions where there are smoldering fires."

That particulate matter, when it enters the lungs, can cause asthma, respiratory illness, and lung disease. Not something you'd want to live anywhere close to—unfortunate for the millions of people who live near the places primed by climate change to smolder.

The air pollution, the super fog, the carbon emissions; all told, smoldering fires represent yet another under-examined calamity burgeoning in a warming world.

"From a climate change perspective," Dr. Watts said, "we should be very concerned."