The far north is both a huge carbon sink and a powerful environmental time bomb. The region stores a huge amount of CO2 in boreal forests and underlying soils. Organic peat soil, for example, covers only 3% of the Earth’s land area (there are also some in tropical regions), but it contains a third of its terrestrial carbon. And Arctic permafrost has locked away thousands of years of plant matter, preventing the rot that would release clouds of planet-warming carbon dioxide and methane.
But in two recent papers, scientists found that wildfires and human interference are reducing the ability of northern ecosystems to sequester carbon, threatening to turn it into carbon. sources. This will in turn accelerate climate change, which is already warming the Arctic four and a half times faster than the rest of the world, triggering the release of even more carbon – a gnarly feedback loop.
In fact, more than 100 wildfires are currently burning in Alberta, Canada, forcing nearly 30,000 people from their homes – an “unprecedented situation” in the region. The annual area burned in Canada has doubled since the 1970s, says Mike Flannigan, a fire scientist at Thompson Rivers University. (He was not involved in any of the new studies.) “A warmer world means more fire,” he says. “As the temperature warms, the atmosphere becomes very efficient at sucking moisture out of dead fuel. This therefore means more fuels available to burn, leading to high intensity fires that are difficult or impossible to extinguish.
The northern boreal forests are the largest terrestrial biomes on the planet. When they burn, they release greenhouse gases from both vegetation and carbon-rich soils, which the first new paper, published in March, quantified. In fact, burning boreal forests releases between 10 and 20 times more carbon than fires in other ecosystems. Typically, fires account for 10% of global fire CO2 emissions annually, but they contributed 23% in 2021, thanks to severe heat waves and drought.
“We are facing a dangerous positive feedback between climate and boreal fires,” says lead author Bo Zheng of China’s Tsinghua University. “The slow recovery of soil microbial communities in forests after extreme wildfires weakens carbon sinks and prevents them from fully absorbing the large amount of carbon dioxide released during combustion.” This, adds Zheng, “will increase the concentration of carbon dioxide in the atmosphere and promote global warming, further increasing the likelihood of extreme wildfires.”
Zheng’s team found that the geographic range of boreal fires has expanded since 2000, which worries Carly Phillips, a researcher at the Union of Concerned Scientists who studies these fires but was not involved in the article. “Given the carbon density in these ecosystems, that translates into a lot of emissions,” she says.
Climate change makes these fires more likely. As northern landscapes dry out, they accumulate dead brush ready to burn catastrophically. Warming also creates more opportunities to ignite vegetation. The region has gotten so hot that lightning – usually a hot weather phenomenon – now strikes within 300 miles of the North Pole, and strikes could double in the Arctic by the end of the century.