Rising river habitat risk in China is driven by climate change and intensive human activities

Human activities and climate changes threaten river habitats worldwide. This study developed a framework combining external river disturbance and internal river obstruction to assess river habitat risk (RHR) and then identify priority conservation and restoration basins in China. A new river fragmentation index was suggested, which considers the comprehensive impact of the number, location, and type of river obstacles on river fragmentation. Results showed that RHR was high in the eastern China and low in the western China. Approximate 8 %, 28 %, and 64 % of 55,820 basins in China were at high, moderate and low risk levels in 2020, respectively. External river disturbance and internal river obstruction risk dominated in the water-rich and -scarce basins, respectively. In addition, landscape risk characterized by land uses was the primary factor of external river disturbance while river regulation and sediment trap were the primary factors of internal river obstruction. RHR change from 2010 to 2020 was mainly driven by climate change, with risk increase and decrease in the 28 % and 35 % of basins in China, respectively. The RHR increase mainly occurred in the southeastern China. The 4.2 % and 23.6 % of 55,820 basins in China were identified as priority restoration areas with high RHR in 2020 and RHR increase from 2010 to 2020 and as priority conservation areas with low RHR in 2020 and RHR decrease from 2010 to 2020, respectively. The priority restoration basins were mostly distributed in the urban agglomeration areas of southeastern China. High RHR basins and priority restoration basins were concentrated in the Huai River area where urbanization, agricultural activity, and flood control were intensive. In addition, The RHR from precipitation change in the southwest river area and temperature change risk and water use degree risk in the northwest river area should be cared. China should develop green urban space, ecological and water-saving agriculture, ecological riparian zone, river ecological corridor, and dredging etc. to restore river habitat and decrease RHR.