Increased megafauna stranding risk from sand mining: Lessons from the Yangtze finless porpoise

Sand mining has emerged as a pervasive environmental crisis with profound consequences for freshwater ecosystems. However, current conservation efforts primarily focus on regulating mining intensity, often neglecting the long-term ecological consequences that may lead to unforeseen risks. Here, we integrated 20 years of remote sensing data on sand dredging activities with eight field surveys of the megafauna, Yangtze finless porpoise (Neophocaena asiaeorientalis asiaeorientalis) in Poyang Lake, to investigate the long-term impacts of sand mining. Our findings revealed that high-density sand mining creates numerous water-filled depressions during the dry season (equivalent to 153.5 % of the original lake area), which we refer to as sand traps. These activities exert dual impacts on porpoise populations: high-intensity dredging significantly limits porpoise distribution during active mining (p = 0.031); whereas the expansion of sand traps attracts porpoises after mining ceases (p = 0.0016). Within sand trap areas, untransported sediments accumulate to form sand reefs, leading to irregular water depth. Moreover, under extreme dry events, the expansion rate of sand reefs (<1 m water depths) within sand traps is 2.15 times higher than that outside them, further exacerbating the risk of megafauna stranding. In addition to controlling mining intensity, our study highlights the urgent need for mitigating long-term stranding risks from sand mining through ecological water level management, intensified patrolling, and targeted dredging, particularly amid the increasing frequency of extreme drought events.