A new study published in Phys.org reveals that extreme droughts in the Amazon rainforest significantly reduce the soil's capacity to absorb isoprene, a volatile organic compound (VOC) naturally produced by plants. More than 500 megatonnes of isoprene enter the atmosphere annually, mostly from tropical forests. Soils are recognized as major sinks for this compound, but their behavior under environmental stress has remained poorly understood — until now.
This disruption matters because isoprene plays a critical role in atmospheric chemistry, influencing ozone formation and aerosol processes that affect cloud formation and regional climate. The Amazon basin accounts for a substantial share of global isoprene emissions, making even small changes in soil uptake potentially significant for the Earth system. The findings highlight a previously underappreciated vulnerability in the rainforest's climate regulation functions.
According to the researchers, extreme drought conditions suppressed the microbial activity in soils that typically breaks down isoprene. The study, conducted in the Amazon, showed that drought-stressed soils absorbed far less of the compound compared to healthy rainforest soils. The exact percentage reduction was not specified in available reporting, but the authors emphasized that the feedback loop between forest health and soil processes is more fragile than earlier models assumed.
The implications are twofold: intensified droughts driven by climate change could further weaken the Amazon's ability to buffer atmospheric VOC levels, potentially accelerating regional warming. Additionally, altered isoprene dynamics may shift ozone and aerosol concentrations, with unknown effects on local precipitation patterns. The study adds urgency to calls for enhanced drought monitoring in tropical ecosystems.
Experts caution that soil-based isoprene uptake is just one component of a complex system. Further research is needed to quantify the net atmospheric impact and to distinguish drought effects from seasonal variability.