[Ecological Risk Evaluation and Ecological Zoning Construction in the Upper Yangtze River Basin].

The upper reaches of the Yangtze River is an important ecological barrier for the entire Yangtze River Basin and a key national water source and conservation area， and its ecological risk problem constrains the sustainable development of the whole Yangtze River Basin. To evaluate the ecological environment security status of the upper Yangtze River， based on land use data from 1980 to 2020， the land use transfer matrix， ecosystem service value evaluation model， and ecological risk index model were applied to explore the spatial and temporal evolution patterns of ecosystem service provision value and ecological risk index in the upper Yangtze River Basin， and the Z-score standardization method was applied to construct four types of ecological zones. The results of the study follow： ① The changes of each land use type in the upper Yangtze River Basin were significant. However， the areas of unutilized land and arable land decreased more substantially， by 8 222 km² and 6 776 km²， respectively， accounting for 48.68% and 40.12% of the total decrease. ② Forest land was the most dominant land use type transferring out and transferring in， with areas of 121 125 km² and 129 424 km²， respectively， accounting for 32.26% and 34.47% of the total area of transfers out and transfers in. ③ The ecosystem service value showed a trend of decreasing and then increasing， with the high supply value area mainly distributed in northern Yunnan Province and southwestern Sichuan Province and the low supply value area mainly distributed in Chengdu Municipality， western Chongqing Municipality， and other areas with high population density. ④ The average ecological risk in the upper Yangtze River Basin showed a trend of fluctuating upward and then downward， gradually shifting to the medium-risk type， with a spatial distribution of "high in the northwest and east， and low in the middle." ⑤ During the study period， the number of the four types of ecological zones changed little， and the ecological zones were in a stable state. Among them， the partition type with the largest proportion was the high supply value-low ecological risk zone， and the distribution area of the high supply value-high ecological risk zone was relatively small. The findings above provide theoretical references for the ecological security of the upper reaches of the Yangtze River as well as the coordinated development of the economy and ecological environment in the Yangtze River Basin.