Rising sclerophylly in the Amazon over the last four decades

The Amazon Forest, essential for global biodiversity and climate regulation, is increasingly threatened by deforestation, fire, and climate change, pushing it toward a critical tipping point. This may lead to a shift from dense forests to open, fire-prone landscapes, jeopardising its original biodiversity and key ecological functions. Using historical satellite spectral data and community-weighted tree trait data from 130 vegetation plots, we quantify changes in leaf sclerophylly - leaf toughness, a drought-adaptive trait - across the Amazon. We show that vegetation with higher sclerophylly exhibits more stable spectral reflectance over time. Over the last four decades, this stability has increased by 10%, suggesting a rise in sclerophylly linked to climatic stress. If current trends continue, in 40 years, the Amazon may approach sclerophylly levels seen in transitional zones with the Cerrado savanna biome, potentially altering carbon and water cycles with profound implications for biodiversity and ecosystem resilience. However, significant regional variation in this trend underscores the role of local factors, including human activities, in influencing forest resilience. These findings highlight the urgent need for targeted conservation strategies to mitigate both climate-induced and anthropogenic pressures, ensuring the forest’s future resilience.