Accelerated Erosion and Sediment Fluxes in the Ayeyarwady River Due To Anthropogenic Activities

Human activities have a strong impact on global climate and natural ecosystems, yet the extent of their influence on long-term natural erosional processes remains poorly determined. A quantitative analysis is needed. The Ayeyarwady River, renowned for its large sediment flux ranking second in Asia, provides a compelling case study. We here show that extensive anthropogenic activities in the Ayeyarwady catchment have strongly accelerated erosion rates compared to natural benchmark levels, thereby contributing to its high sediment discharge. To highlight this point, we compared present-day erosion rates calculated from sediment fluxes with long-term natural erosion rates derived from detrital-apatite fission track (AFT) and cosmogenic ¹⁰Be data. Our findings reveal a stark contrast. Long-term natural erosion rates were notably higher in the Upper Ayeyarwady (0.06–0.34 mm/a) than in the Upper Chindwin (0.02 ± 0.005 mm/a), whereas present-day erosion rates are three times higher in the Upper Chindwin (0.63 ± 0.05 mm/a) than in the Upper Ayeyarwady (0.19 ± 0.02 mm/a). Particularly, noteworthy are the Upper Chindwin and Mu drainages, where erosion rates are calculated to have increased by more than an-order-of-magnitude relative to long-term natural background rates. Such a striking increase in erosion rate correlates positively with the spatial distribution of alluvial mining, especially for the Upper Chindwin catchment. The observed increases in sediment fluxes from long-term to present-day timescales may also be attributed to land-use expansion related deforestation, and intensified precipitation. These results underscore how human activities can drastically accelerate erosional processes, thus exerting a dramatic impact on natural systems.