Fire-derived ozone intensifies carbon loss in Amazon forests under extreme droughts

Abstract The Amazon rainforest is a vital contributor to the removal of anthropogenic carbon dioxide from the atmosphere. Ozone (O 3 ) is an atmospheric pollutant that reduces carbon dioxide uptake by vegetation. Yet the degree to which variability in ozone, elevated by anthropogenic-derived fire activity, and climate contribute to changes in Amazon forest productivity remains poorly understood. Here, we employ a land surface model to quantify the interannual variability of fire-derived ozone damage across the Amazon and explore its coupling with extreme drought and stomatal responses. We estimate that fire-derived ozone damage increases carbon losses by approximately one quarter of direct fire emissions, revealing a potentially important indirect pathway by which may fires amplify carbon loss. Notably, our simulations suggest high fire activity during extreme droughts, such as in 2024, likely result in ozone damage despite extensive stomatal limitation, highlighting the urgency to reduce deforestation and forest fire as the climate changes.