Multi-Scale Assessments and Future Projections of Drought Vulnerability of Social–Ecological Systems: A Case Study from the Three-River Headwaters Region of the Tibetan Plateau

The vulnerability of Social–Ecological Systems (SES) is a frontier research topic in the field of geography. Research on drought vulnerability has emerged as a key area of focus in the study of SES vulnerability, and it has increasingly been recognized as a critical step in formulating policies for drought prevention and mitigation. In this study, the indicator system for drought vulnerability evaluation of SES in the Three-River Headwaters Region (TRHR) was established. This paper revealed the drought vulnerability evolution process and characteristics, and key driving indicators of SES at county-town-village spatial scales in six time periods of 1990, 2000, 2010, 2015, 2020, and 2023, and predicted the drought vulnerability of SES in 2050 under two scenarios. Results indicate that the average drought vulnerability in the TRHR decreased from 0.526 in 1990 to 0.444 in 2023. Compared to 1990, among the 82 selected towns, 85.37% experienced a decline in 2023, and among the 152 selected villages, 95.39% showed a reduction in 2023. Hot spots of drought vulnerability were concentrated in the southeast of the TRHR, while cold spots were in the northwest. From 1990 to 2000, the drought vulnerability of counties and towns in the TRHR increased, but it decreased between 2000 and 2023. In 1990, Henan County exhibited the highest drought vulnerability at the county level. Waeryi Town in Jiuzhi County had the highest vulnerability among towns, while Suojia Town in Zhidoi County had the lowest. Of the 152 selected villages, 41.45% exhibited relatively high or high levels of drought vulnerability, while 23.68% showed relatively low levels. In 2023, Jiuzhi County became the most vulnerable county, with Baiyu Town in Jiuzhi County ranking highest among towns and Suojia Town in Zhidoi County remaining the least vulnerable. At the village level, 22.37% exhibited relatively high or high vulnerability, whereas 42.11% showed relatively low or low levels. Drought disaster records, the proportion of agricultural and animal husbandry output value, the proportion of grassland, the proportion of large livestock, and the per capita disposable income surface are the key factors influencing drought vulnerability in the TRHR. By 2050, under the first scenario, the average drought vulnerability of the TRHR is projected to be 0.428, indicating a medium level, while the second scenario predicts a further reduction to 0.350, representing a relatively low level. The adaptive governance strategies to mitigate drought vulnerability in the TRHR include developing an integrated drought management system; establishing an ecological management, protection, and financial support model; and so on. Overall, this paper can provide scientific references and policy recommendations for policymakers and researchers on the aspects of drought vulnerability and sustainable development of SES.