This paper is the result of eco−geological survey engineering.

Objective As the most severe ecological degradation form in South China’s karst regions, karst rock desertification has posed significant ecological stress effects, creating substantial barriers to the high−quality socioeconomic development of these areas. Advancing the scientific governance of karst rocky desertification, promptly identifying the critical ecological risks in vulnerable karst regions under evolving environmental stressors, and implementing integrated conservation−restoration of mountain−water−forest−farmland−lake−grassland−desert ecosystems constitute a paramount challenge for China's high−quality territorial development in the new era.

Methods This study focused on Quanzhou County, a karst−dominated area in the Yangtze−Pearl River watershed divide (Guangxi, China). Through integrated remote sensing monitoring and field surveys to construct a transition matrix of rocky desertification grades and land use types, we systematically analyzed the spatiotemporal evolution patterns and dominant controlling factors of rocky desertification from 2000 to 2023, with particular emphasis on the impacts of extreme dry−hot conditions on rocky desertification severity.

Results ① In 2023, the karst rocky desertification area reached 353.77 km² in Quanzhou County, with light and moderate grades accounting 81.2% of the total. From 2000 to 2023, the karst rock desertification evolved through three distinct phases: rapid expansion (2000—2005), gradual mitigation (2005—2021), and accelerated resurgence (2021—2023), maintaining a predominant distribution of light−to−moderate grades. ② High−risk zones clustered in areas with 5°~25° slopes, high−coverage grasslands and croplands, limestone lithology, and epikarst zones with 2~10 m thickness. ③ From 2000 to 2021, the land−use changes triggered sudden karst rocky desertification in 1%~3% of cases, but unsustainable land practices caused over 97% of karst rock desertification. ④ From 2021 to 2023, extreme dry−hot events were the primary driver of intensified karst rocky desertification. Prolonged drought caused severe water scarcity and widespread vegetation die−off in watershed areas, triggering accelerated desertification and severe ecological degradation.

Conclusions The kasrt rocky desertification remains a critical challenge in watershed regions, driven synergistically by fragile karst eco−geological conditions and unsustainable anthropogenic disturbances, while exhibiting heightened sensitivity to extreme dry−hot events. This study provides scientific evidence for mitigating critical ecological risks in vulnerable karst systems under intensifying climatic extremes.