Global mercury emissions from wildfires are three times lower than existing estimates

Wildfires reintroduce mercury (Hg) stored in terrestrial ecosystems into the atmosphere, raising concerns about environmental and health risks. Existing estimates rely on emission factors derived from limited observations and assume that Hg emissions scale with burnt biomass. This simplification can bias emissions because it neglects the variability in Hg content and fire intensity. Here, we develop an atmosphere-land-vegetation coupled Hg model to simulate wildfire Hg emissions and postfire impacts for 1995–2014. Our results show that global wildfire Hg emissions are about three times lower than previous estimates, revealing that Hg release is controlled primarily by Hg content rather than burnt biomass. Although these emissions are equivalent to only 10% of global anthropogenic Hg emissions, we find that episodic fires can cause significant short-term local contamination and alter land-atmosphere Hg exchange through a wildfire-vegetation-Hg feedback loop. These impacts warrant greater attention as wildfire risks continue to rise in a warmer future.