Carbon emissions from wildfires in boreal forests, the largest terrestrial biome and a significant carbon sink, rose higher in 2021 than in any of the past 20 years, according to a new study.
Boreal forests, which cover northern latitudes in parts of North America, Europe and Asia, typically account for about 10 percent of the carbon dioxide released annually by wildfires, but in 2021 they were responsible for almost a quarter of those emissions.
In general, emissions from forest fires are increasing. However, in 2021, boreal forest fires released “abnormally huge amounts of carbon”, releasing 150 percent of their annual average over the previous two decades, according to a study published earlier this month in the journal Science. That’s double what global aviation emitted that year, author Stephen Davis, professor of systems science at the University of California, Irvine, said in a press release.
Emissions from wildfires create a detrimental climate feedback loop as the greenhouse gases they add to the atmosphere contribute to climate change, which contributes to more frequent and extreme wildfires, according to the authors of the study.
“The boreal region is so important because it contains a huge amount of carbon,” said Yang Chen, an assistant researcher at the University of California, Irvine and one of the study’s authors. “The impact of fire on this carbon release could be very significant.”
In recent decades, boreal forests have warmed at an increasing rate, causing the permafrost to thaw, drying vegetation to tinder, and setting the stage for wildfires. The advocacy group Environment America said that disturbances such as deforestation, along with a warming climate in the boreal forests, could turn the region “into a carbon bomb”.
Overall, boreal forests have “profound implications for the global climate,” said Jennifer Skene, policy manager for natural climate solutions at the Natural Resources Defense Council’s international program. “In fact, boreal forests store twice as much carbon per acre as rainforests, trapped in soil and vegetation. The Canadian boreal resources alone contain twice as much carbon as the world’s oil reserves. So this is an incredibly important forest for a climate-smart future.”
Most of the carbon that boreal forests take up is in the soil, as plants slowly decompose at low temperatures, Skin said. When wildfires burn, they release carbon stored in soil, peat and vegetation. In 2019, a study funded in part by NASA showed that as fires increase, boreal forests may lose their carbon sink status as they release “inherited carbon” that the forest has stored from past fires.
In 2021, drought, very high temperatures and water scarcity contributed to abnormally high fire emissions from boreal forests, according to a new study. Although forest fires are a natural part of the boreal ecosystem, fires in a given forest typically take more than 50 years, and often a century or more, between fires. But as the climate warms, fires are increasingly occurring in these landscapes.
“What we are seeing in the northern latitudes is a fire regime that is certainly becoming much, much more frequent and intense than before, primarily due to climate change,” said Skene, who was not involved in the study. Skin said it’s also important to protect boreal areas because “industrial unrest” makes forests more vulnerable to wildfires.
There is less deforestation and deforestation in boreal forests than in other tree biomes such as rainforests. But the authors of the study noted that increased disturbance in the boreal forests will affect their ability to store carbon, and climate-induced fires could put the forests in a “frequently restless state.” In 2016, a wildfire near Alberta spread to boreal forests and burned nearly 1.5 million acres in total, becoming one of Canada’s costliest disasters. To preserve the biome, over 100 indigenous peoples and communities have created programs to help manage and protect parts of the boreal region.
“In terms of climate change mitigation and climate resilience, protecting forests is more important than ever,” said Skin. “In a changing climate, it is much more difficult for forests to recover to the way they were in the past. Once disturbed, they are much less resistant to these kinds of influences.”