Forest edge effects amplify impacts of 2023-2024 Amazon drought on forest productivity

The Amazon rainforest is increasingly affected by both forest fragmentation and extreme droughts. However, the interacting impacts of these two disturbances on forest carbon dynamics remain poorly understood. Here, we investigated how fragmentation-induced forest edges modulated productivity responses to the 2023–2024 “once-in-a-hundred-years” drought in the Amazon. Using high-resolution satellite observations of photosynthetic indices together with canopy height and forest cover data, we compared the differences in drought responses between edge and interior forests across the basin. We found that, at the basin scale, edge forests exhibited stronger drought-induced productivity declines than interior forests and contributed 64.0 ± 18.1% of the total productivity loss during this drought, indicating that edge effects overall amplify drought impacts on productivity. However, edge responses exhibited strong regional contrasts during this drought. In the northeastern Amazon, where water tables were deeper and droughts were more severe, edge forests exhibited 4.9 ± 2.4% greater productivity declines than interior forests. In contrast, in the southwestern Amazon, characterized by shallow water tables, edge forests showed 2.9 ± 1.8% smaller productivity reductions than interior forests. In addition, edge-related forest structural degradation, reflected by reduced canopy height, further intensified the differences in drought responses between edge and interior forests. Our findings show that edge–drought interactions substantially undermine the carbon uptake across large areas of the Amazon, highlighting the urgent need to curb further fragmentation and protect remaining interior forests, particularly in drought-prone edge regions.