New research has found that wildland fires may be releasing far more air-polluting gases than previously thought.
The findings suggest that current global fire emission inventories significantly underestimate the true environmental and health impacts of wildfires and controlled prescribed burns.
Traditionally, fire emission inventories have focused on two types of pollutants: primary organic aerosols (POA) and volatile organic compounds (VOCs). However, the new study shows that intermediate-volatility and semi-volatile organic compounds (IVOCs and SVOCs) – which are harder to measure but more likely to form harmful fine particles in the air – have largely been overlooked.
The research team developed a global wildland fire organic emission inventory covering 1997 to 2023 that, for the first time, accounts for organic compounds across their full range of volatility. Using satellite-based burned-area data and a combination of field measurements and laboratory experiments, the researchers calculated emissions from fires in forests, grasslands and peatlands worldwide.
The results show that wildland fires release an average of 143 million tons of airborne organic compounds each year – 21% more than earlier estimates. The newly identified gap amounts to about 25.1 million tons per year of IVOCs and SVOCs alone.
Grassland fires were the largest contributors, accounting for 66% of full-volatility emissions, followed by tropical forests (13%), boreal forests (11%), peatlands (6%) and temperate forests (4%).
Geographically, Southern Hemisphere Africa emerged as the world’s largest hotspot, with organic emissions reaching 4.4 tons per km² per year – up to nearly seven times higher than other major fire regions such as Northern Hemisphere Africa, South America and Equatorial Asia.
‘These regions’ air pollution challenges are complex,’ the researchers observed, pointing to areas where intense fire activity overlaps with human emissions. Addressing air quality in these hotspots will likely require coordinated strategies that account for both sources.
On a global scale, wildland fires now appear to rival human activity in their contribution to the most pollution-forming compounds. While anthropogenic sources still emit more organic material overall, the study found that fires and human activities produce comparable amounts of IVOCs and SVOCs.
Lyuyin Huang, the study’s first author said: ‘The inventory provides a foundation for more detailed air-quality modeling, health-risk assessment and climate-related policy analysis.’
Photo: Josh Berendes
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