The Amazon rainforest may be revealing a new warning sign of climate stress. Scientists have discovered that trees in the world’s largest rainforest released previously undetected chemical compounds into the atmosphere during and after the record breaking drought of 2023–24 suggesting that extreme climate events are altering the forest’s natural processes in unexpected ways.
The findings come from researchers at Max Planck Institute for Chemistry, who monitored air samples above the Amazon canopy and found that trees began emitting rare chemical compounds known as sesquiterpene alcohols. These molecules had never before been recorded in the air over a tropical rainforest.
Researchers collected air samples at the Amazon Tall Tower Observatory, located northeast of Manaus. By tracking emissions before during and after the severe drought linked to the 2023–24 El Nino event scientists were able to observe how the rainforest’s chemistry changed as environmental conditions worsened.
During the drought, temperatures climbed significantly while humidity and soil moisture dropped to unusually low levels. The team found that emissions of stress related compounds called sesquiterpenes more than doubled. These chemicals are often released by trees when they are exposed to heat, drought or pest attacks.
What surprised researchers most was what happened after rainfall returned. Instead of disappearing, the stress signals evolved. Trees began releasing heavier compounds led by beta-eudesmol, a molecule never previously detected in rainforest air. These emissions continued for weeks after the drought had eased, suggesting that the forest remained under physiological stress even during recovery.
Scientists believe these compounds may help trees cope with damage caused by reactive oxygen species, unstable molecules that build up during extreme environmental stress. While the exact role of beta eudesmol inside trees remains unclear, the chemical is known for its antioxidant properties in other biological systems.
The discovery is important because these airborne compounds can influence cloud formation, rainfall patterns and atmospheric chemistry. If drought driven emissions become more common as global temperatures rise, they could affect weather systems across the Amazon Basin and beyond.
Lead researchers say the findings may provide a valuable new way to monitor forest health. The newly detected compounds could serve as real time indicators of environmental stress, helping scientists understand how the Amazon responds to increasingly frequent and intense droughts.
The study published in the journal Communications Earth & Environment, adds to growing evidence that climate change is not only affecting the Amazon’s trees but may also be changing the very chemistry of the rainforest atmosphere. As droughts become more severe, researchers warn that these unusual emissions could become a permanent feature of the region’s environmental landscape.