Rain can convert wildfire smoke into nutrient-rich fertilizer
A new study shows that when rain falls through wildfire smoke, it can deposit significant amounts of nitrogen, phosphorus, and potassium onto ecosystems. These nutrient pulses, which are essential for life, could become more common as wildfires increase. The finding highlights an overlooked ecological consequence of fire.
The study analyzed 250 sites across 16 U.S. climate regions, using satellite smoke observations and rainfall chemistry data from 2014, 2020, and 2022. Researchers found that smoke-rain events, though relatively infrequent, delivered disproportionately large shares of nitrogen, phosphorus, and potassium to ecosystems. The National Atmospheric Deposition Program's long-term rainwater monitoring network, originally established to track acid rain, supplied the chemical data.
Smoke-rain days were more numerous in 2022 than in 2014, with regional hotspots shifting year to year. When rain passes through smoke, dissolved nutrients become immediately bioavailable to organisms in lakes and on land. The research team included scientists from the University of Utah, Utah State University, and the Cary Institute of Ecosystem Studies.
As wildfires intensify, smoke-rain nutrient pulses could reshape soil chemistry and aquatic ecosystems across the U.S., particularly in downwind regions far from burn zones. Land managers may need to factor these inputs into fertilization and restoration planning. Communities relying on reservoirs or lakes could see shifts in water quality and algal growth. The finding suggests fire's ecological reach extends well beyond burned areas, potentially affecting agriculture and forestry in ways not previously accounted for.