Global carbon dioxide emissions from forest fires have surged by 60% since 2001, with emissions nearly tripling in some of the most climate-sensitive boreal forests, according to a new study published in the journal Science. The research, led by the University of East Anglia, involved scientists John Abatzoglou and Crystal Kolden from the University of California, Merced, and analysed global fire patterns by grouping regions into "pyromes" – areas where forest fire activity is influenced by similar environmental, climatic and human factors.

The study attributes the rise in emissions to an increase in what researchers describe as "fire-favourable weather", including hot and dry conditions that are often associated with heat waves and droughts. Additionally, accelerated forest growth in some areas has resulted in an abundance of vegetation that fuels wildfires. The rapid warming in northern latitudes, occurring at twice the rate of the global average, has further exacerbated the situation. Emissions from fires in one of the largest pyromes, encompassing boreal forests in Eurasia and North America, have nearly tripled from 2001 to 2023.

“Our planet's temperate and boreal forests are under fire as the Earth continues to warm,” said Abatzoglou, a professor at the School of Engineering. “Fire activity is the result of a complex interplay of factors, but the growing prevalence of fire-conducive weather has exacerbated the scale of wildfires.”

The research highlights a significant increase not only in the extent of forest fires over the past two decades but also in their severity. Fires are burning hotter and more completely, releasing approximately 50% more carbon per unit burned area than in the early 2000s.

The western United States, particularly California, has faced numerous wildfire disasters in the past decade, such as the 2018 Camp Fire, which resulted in 85 fatalities. The study underscores that these fires are not only causing loss of life and property but are also contributing to higher carbon emissions compared to previous decades.

Forests play a crucial role in global carbon storage, as their growth helps sequester carbon and mitigate climate change. However, the rising frequency and intensity of wildfires threaten this balance, as forests may not fully recover to their previous state, potentially reducing their capacity for long-term carbon storage. Fires outside tropical regions are now emitting 500mn tonnes more CO2 annually than they did two decades ago.

“Increasing extratropical wildfires are also contributing substantial levels of smoke, leading to hazardous air quality events, as seen in California in 2020 and across the northeastern U.S. during the 2023 Canada fires,” noted Kolden, director of the UC Merced Fire Resilience Center.

The study points out that while global burned areas are declining due to reduced fire activity in tropical savannahs, the uptick in fires in extratropical regions is driving a rise in overall wildfire carbon emissions. This trend underscores the need for restoring and maintaining forest health, especially in western US forests that historically experienced more frequent, lower-intensity fires.

“We know that fire suppression in frequent-fire forests led to a build-up of fuels, resulting in carbon-emitting megafires under extreme fire weather,” Kolden said. “These conditions are becoming more frequent due to anthropogenic climate change. However, reducing tree density through prescribed burns and fuel management projects can help mitigate high-severity fires and enhance carbon storage, even in the face of climate change."

She added: "Fewer, larger trees hold more carbon and are much more resistant to burning than many smaller ones."