During the record-breaking 2023–2024 El Niño drought, the most severe ever recorded in the Amazon, trees in the rainforest dramatically altered their emissions of volatile organic compounds.
Researchers using high-precision measurements from an 80-meter tower in the central Amazon detected a 122% increase in sesquiterpene emissions during the drought, while levels of isoprene and monoterpenes remained relatively stable. Even more striking, once the rains returned in the following wet season, the forest began releasing an entirely new class of compounds never previously observed in rainforest air: sesquiterpene alcohols, including beta-eudesmol, alpha-eudesmol, and gamma-eudesmol. These emissions persisted for weeks after the drought ended.
Sesquiterpenes and their oxygenated derivatives are known to function as stress signals and protective compounds, helping plants cope with oxidative damage from extreme heat, drought, and water scarcity. The appearance of these lower-volatility alcohols after the peak stress suggests the trees’ defense metabolism remained activated long into the recovery phase.
These findings matter for atmospheric chemistry. The emitted compounds can influence the formation of secondary organic aerosols, which affect cloud formation, regional weather patterns, and even how the forest interacts with sunlight and precipitation. As climate change increases the frequency and intensity of Amazon droughts, such novel emissions could become more common.
[Byron, J., et al. (2026). Intense El Niño provokes production of new reactive volatiles as stress defences in Amazon rainforest. Communications Earth & Environment, 7, 159. DOI: 10.1038/s43247-026-03597-7]