Long-term variations of hydrological connectivity and its drivers in the middle reach wetlands of the Yangtze River

This study focuses on the middle Yangtze River's ecologically vital but hydrologically vulnerable wetlands: the Poyang Lake Plain and Dongting Lake Plain, China. Hydrological connectivity is essential for sustaining wetland ecological integrity, especially under accelerating climate change and intensified human activities. However, few studies have provided long-term, quantitative assessments of wetland hydrological connectivity and its driving mechanisms. This study examined the long-term (1993–2022) patterns and drivers of wetland hydrological connectivity in the Poyang Lake and Dongting Lake plains, and quantified natural and anthropogenic factor impacts using random forest (RF), partial least squares structural equation modeling (PLS-SEM), and Copula methods. The results revealed a significant long-term decline in hydrological connectivity in the Poyang Lake Plain, whereas no consistent trend was observed in the Dongting Lake Plain. Both regions experienced marked reductions in connectivity following the operation of the Three Gorges Dam, particularly during the wet season. Climate factors predominated drivers of hydrological connectivity changes across both plains. Although human-induced land use change accounted for less than 5 % of the total effect, it served as an important amplifying stressor on connectivity loss. Critical water level thresholds are 9.8 m and 23.5 m for Poyang Lake and Dongting Lake respectively to maintain moderate or higher connectivity. These insights provide a scientific basis for region-specific wetland management and restoration. • A framework to quantify long-term wetland hydrological connectivity dynamics. • Climate and hydrology drive connectivity, human impact is secondary and negative. • Ecological water levels maintain hydrological connectivity at moderate-high levels.