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The western U.S. has made headlines this summer for its intense wildfires, but it's not the only region of the world that's burning. A new study has found that the boreal forests just south of the Arctic Circle are experiencing a higher frequency of wildfires today than at any point in the last 10,000 years, a discovery that spells an uncertain future for these vast stores of carbon.
Researchers for the study, published Monday in the Proceedings of the National Academy of Sciences, used charcoal samples from 14 lakes in Yukon Flats, AK, and found that the fire frequency in the area is twice as high as it was 500 to 1,000 years ago - about 20,000 wildfires per 1,000 years compared to 10,000 fires per 1,000 years.
The increasing wildfire activity in the subarctic region are likely linked to rising temperatures, Ryan Kelly, a researcher who examined the coal records, told LiveScience.
"There's a pretty clear link between humans inducing a warmer climate and increased forest burning," he said.
It's unclear yet what this increased burning means for the subarctic boreal forests. The researchers also found that, after the fires, young deciduous trees were moving in to take the place of the black spruces, a staple species in many boreal forests - a trend that could help slow the growth of future wildfires, as the deciduous trees are not as quick to burn as the coniferous spruces. This trend of deciduous trees replacing spruce was also seen during the Medieval Climate Anomaly, a period that experienced similar temperatures to today, but as the new study's researchers found, the fire frequency today is double that of the MCA. In addition, since future temperatures are projected to reach higher levels than they have in the past 10,000 years, even deciduous trees could end up being highly flammable, one of the researchers told Climate Central.
"The ecosystems in this ecoregion appear to be undergoing a transition that is unprecedented." Feng Sheng Hu, a coauthor of the study and a plant biologist at the University of Illinois, told Climate Central. "We think this transition may occur in other boreal regions in the decades to come."
But one thing that is clear is that losing the boreal forest to wildfires releases a major amount of stored carbon into the atmosphere. Boreal forests cover about 10 percent of the Earth's land surface and contain nearly a third of the carbon stored in biomass and soils - nearly twice as much as tropical forests per hectare. Boreal forsests are located on carbon-rich permafrost, which, when warmed, release huge amounts of carbon into the atmosphere. One study found that, after a fire in the boreal forest, the ground's thermal conductivity can increase 10-fold and the surface albedo can be cut in half.
Unfortunately, wildfires aren't the only climate-related threats facing the boreal forest. Already, Russia's boreal forests' larch trees, which have historically been the biome's dominant plant, are being replaced by coniferous trees, a trend that in some cases is leading to a positive warming feedback loop. And the mountain pine beetle, which can destroy huge swaths of forest, is expanding north into Canada's boreal forest, aided by warmer temperatures. These threats aren't just environmental problems - a 2012 Pew report found that Canada's boreal forests, a portion of which are being destroyed and replaced by tar sands oil development, provide about $700-billion in services globally each year.
