Peatlands across the world are vulnerable to fires as a result of climate change, according to a paper published this month in the journal Nature Geoscience.
Peat-rich areas, which span every continent but are most prevalent in the northern high latitudes, not only contain more carbon than is stored in all other vegetation, but also store carbon that has not been part of the active carbon cycle for centuries, the authors say.
"We’ve always known that peatlands do burn, but they’re burning at much faster rates as a result between human activities and climate change," said the study’s lead author, Merritt Turetsky, a professor of integrative biology at the University of Guelph in Ontario.
Peatlands, which cover 2 to 3 percent of the planet’s land surface but store around 25 percent of the world’s soil carbon, are an organic soil compound that consists of partially decayed plant remains mixed with soil that is too wet for further decomposition.
The ecosystem is layered, with newer plant remains decomposing on top and older organic matter buried under the water table decomposing very little. The layers can be hundreds, even thousands, of years old.
The authors assert that if warming continues and the water table drops, more decomposition will occur, releasing carbon stored in the peat. More worrisome, Turetsky said, is that peatlands will also dry out, leaving them susceptible to fire.
Potential for long-lived, toxic fires
Peat is naturally protected from burning because of its wet nature, but when peat does catch fire, it burns by what is called smouldering combustion, a flameless burn that can survive under low temperatures and in moist conditions and can last for weeks, sometimes months.
Think of it as the difference between a match and a cigarette, said Adam Watts, a fire ecologist at Nevada’s Desert Research Institute and one of the co-authors of the study. The match is a more traditional forest or wildfire: quick and efficient. Peat fires are like a cigarette burning: slow, flameless and releasing smoke that is full of more potent climate change chemicals such as methane and carbon monoxide.
The particulates released in peat fires are also associated with serious human health risks. A study that examined smoke-affected counties in North Carolina after a peat fire burned for more than six months in 2008, scorching more than 40,000 acres, showed that emergency room visits during the fire increased by 73 percent for chronic obstructive pulmonary disease, 65 percent for asthma, and 59 percent for pneumonia and bronchitis. Symptoms of heart failure increased by 37 percent.
Emissions like those from fossil fuels
If you imagine your typical forest, with ponderosa pine trees and the like, while bugs and other microbes decompose the pine needles and other organic materials, an organic dust will be created that will coat the forest floor, Watts said. If that forest catches fire, the plant materials that will burn, the pine needles and tree limbs, were created using carbon from the last few years, maybe decades. Watts calls this "new carbon."
In peat forests, because the plant material is not decomposing in the same way, organic matter accumulates for centuries and is made of what Watts calls "old carbon."
"In terms of emissions, you might think of peat fires as more like fossil fuels," Watts said, because they release ancient carbon that is not likely to be moved from the atmosphere and stored anytime soon.
In turn, peat fires have some of the largest carbon footprints of any blazes.
Researchers in the paper wanted to address the different natures of peatlands in tropical parts of the world, specifically Southeast Asia.
In the northern latitudes, peatlands occur in boreal forests, often in remote areas, and will naturally burn.
Tropical fires get help from lawbreakers
But in Southeast Asia, especially Indonesia and Sumatra, over the last two decades, peat fires have been most often set by humans in order to clear land for agricultural purposes such as establishing palm oil forests or timber plantations. Although it is illegal, citizens will drain the peatlands by creating canals and set fire to the forest to clear it because it is cost-effective.
In the tropics, peatlands do not naturally burn, said Susan Minnemeyer, geographic information systems manager for the Forests Program at the World Resources Institute, and health hazards from the fires are estimated to kill more than 300,000 people a year. Tropical peat fires can emit three to six times as much particulate matter as grassland, forest or plantation fires per unit of carbon combusted, the paper’s authors write.
Peat fires in parts of Southeast Asia are an annual occurrence that send heavy smoke and haze into the air. In June 2013, BBC News reported, officials in Singapore were forced to close schools as a smoky haze enveloped the country because of peat fires raging in Indonesia.
The effect of peat fires on climate change is also significant. Carbon dioxide emissions from peat fires are heavy. Widespread peat fires that burned in Indonesia in 1997 and 1998 are estimated to have released about 15 percent of the global emissions at that time, according to the paper.
Watts said the goal of the paper, which brought together six peatlands experts from across the world, was to determine what generalities in the peatlands ecosystems exist across latitudes.
As to what can be done to reduce peat fires, he said some areas are using management tactics similar to controlled burns that are done with traditional forests.
"Unfortunately, short of reducing our emissions and slowing climate change, this paper and lot of other work indicates that no matter what we do, these fires are going to become more prevalent," Watts said.