Planetary boundary-based assessment of environmental sustainability of the Qinghai-Xizang Plateau: a case study of Qinghai Province and Xizang Autonomous Region

To scientifically assess the environmental sustainability of the Qinghai-Xizang Plateau, this study focused on Qinghai Province and Xizang Autonomous Region, using the planetary boundaries framework. Four key indicators including land use, nitrogen cycling, phosphorus cycling, and freshwater use were selected, and the global boundaries were downscaled to the regional level using a per capita approach. Combined with the environmental footprint method, regional resource use was analyzed and compared with the corresponding environmental boundaries to evaluate the sustainability of resources and environment. Results showed that from 2010 to 2020, the boundary values of land use, nitrogen cycling, phosphorus cycling, and freshwater use increased by 5%-22%. Resource use status indicated that land use environmental sustainability development index (ESDI) exceeded 0.7 and nitrogen cycling ESDI remained positive in both regions; phosphorus cycling ESDI in Qinghai recovered from –0.07 to 0.29, while freshwater use ESDI in Xizang consistently remained below zero, indicating persistent overuse. At the prefectural level, Naqu and Ali in Xizang and Guoluo and Yushu in Qinghai maintained high sustainability, whereas Shigatse in Xizang and Haidong and Hainan in Qinghai showed multiple unsustainable indicators. Research reveals that the Qinghai-Xizang Plateau as a whole is in a state where land use and nitrogen cycling are sustainable, while freshwater utilization and phosphorus cycling are unsustainable. The unsustainability of freshwater utilization mainly stems from the unscientific agricultural structure, and the unsustainability of phosphorus mainly results from large-scale agricultural planting.