Abstract: Objective The objective of this study is to explore the concept of ecosystem services (ES), which are defined as the direct and indirect benefits provided by natural ecosystems, contributing significantly to human well-being and maintaining ecological balance. These services play a crucial role in sustaining biodiversity, regulating biogeochemical cycles, and supporting socio-economic development. Since Costanza et al. (1997) introduced the concept of ecosystem service value (ESV), the assessment of these services has become a fundamental tool for understanding their contributions, particularly in the context of rapid urbanization and environmental degradation.While numerous studies have focused on low-altitude regions, there is a notable lack of research on the dynamics of ESV in high-altitude fragile ecosystems, where unique geographic and climatic conditions heighten ecological vulnerability. This study aims to address this research gap by investigating the spatio-temporal relationship between human activity intensity (HAI) and ESV in Lhasa, a high-altitude city located on the Tibetan Plateau.The specific objectives of the study are as follows: First, the study will quantify the impact of urbanization on ESV from 2007 to 2022, focusing on land-use changes and their ecological consequences.Second, it will assess the effectiveness of ecological restoration efforts, such as the Lhasa River Comprehensive Governance Project, in mitigating the decline of ESV.Third, the study will identify spatial patterns and thresholds in the ESV-HAI relationship to inform sustainable urban planning strategies in high-altitude regions. Methods The present study employs a high-resolution spatial analysis framework (0.5 km × 0.5 km grid) to examine the dynamics between ESV and HAI in Lhasa over a 15-year period (2007-2022). The methodology incorporates several key innovations to better assess ecosystem services in high-altitude areas. The assessment of ecosystem services (ES) employs a dynamic model based on the improved equivalence factor method (IEF) developed by Xie Gaodi et al. (2015). This model integrates factors such as net primary productivity (NPP) and precipitation, which are crucial for capturing the dynamic nature of high-altitude ecosystems.The model calculates the value of ecosystem services in each grid cell by considering multiple factors, such as land cover, vegetation type, and environmental productivity. To assess human activity intensity (HAI), the study constructs a composite index that reflects the cumulative effects of land-use change, population density, transportation infrastructure, and industrial development. These indicators are weighted according to their ecological impacts, with the resulting HAI index providing a comprehensive measure of human-induced pressures on the environment. Furthermore, a spatial correlation analysis using Moran''s I statistic is applied to identify patterns of interaction between ESV and HAI across different regions of Lhasa, taking into account the unique topography of the Tibetan Plateau. Results The results of the study highlight significant spatio-temporal variations in ESV and human activity intensity in Lhasa. From 2007 to 2022, the total ESV decreased by 24.3%, amounting to a loss of 462.8 million CNY, with a brief recovery observed between 2012 and 2017. This recovery was largely driven by the Lhasa River Comprehensive Governance Project, which focused on wetland restoration and the improvement of hydrological services. Of particular note is the observation that during this recovery period, hydrological regulation services in Lhasa experienced a 45.5% increase, which is statistically significant with a p-value less than 0.01.Despite this temporary improvement, the overall trend remains negative, indicating that the negative impacts of urbanization on ESV are considerable. The analysis of spatial patterns indicated that areas with high ESV values were predominantly concentrated around the Lhasa River Basin and the Lalu Wetland, while areas with low ESV values exhibited expansion in newly urbanized zones. A bivariate spatial autocorrelation analysis indicated that the positive spatial correlation between ESV and HAI weakened over the study period, with Moran''s I decreasing from 0.249 in 2007 to 0.083 in 2022. Local cluster analysis further identified shifts in spatial patterns, with a 38.6% reduction in high-high clusters (areas with both high ESV and low HAI) and a 217% expansion in low-high clusters (areas with low ESV and high HAI), predominantly in newly urbanized areas. Moreover, the study identified a significant negative correlation (p < 0.05) between ESV and HAI in 23.5% of the grid cells by 2022, indicating a decoupling of the relationship between human activity and ecosystem service provision. The study identified a threshold effect in the ESV-HAI relationship, where the decline in ESV accelerated when HAI exceeded a value of 0.65, with a regression coefficient of -1.32 and a p-value of less than 0.001. This threshold suggests that beyond a certain level of human activity intensity, the negative impact on ecosystem services becomes more pronounced. Conclusion This study makes several important contributions to the understanding of high-altitude urban ecology.First, it provides valuable theoretical insights into the non-linear relationship between urbanization and ESV, particularly in high-altitude regions.The identification of a threshold effect underscores the importance of regulating human activity in critical areas to prevent further degradation of ecosystem services. Secondly, methodological advancements, notably the incorporation of dynamic adjustment factors such as NPP and precipitation, enhance the accuracy and relevance of ESV assessments in topographically complex areas.The model''s performance, with an R2 value of 0.83, signifies a substantial enhancement over conventional models (R2=0.67). The study''s policy implications suggest a dual-threshold management framework for urban growth in high-altitude regions. This framework includes an ecological redline, which maintains HAI levels below 0.4 in critical ecological zones such as the Lhasa River Basin, and a sustainable transition zone, where HAI is controlled between 0.4 and 0.6 with stringent ecological compensation mechanisms. For areas where HAI exceeds 0.6, the study recommends limiting urban expansion to less than 15% of the total area.The findings provide a scientific basis for achieving sustainable urban development while protecting ecosystem services, aligning with the United Nations Sustainable Development Goals (SDGs), particularly Goal 11 (Sustainable Cities) and Goal 15 (Life on Land). Future research endeavors should integrate climate change scenarios and ecosystem process models to further refine the predictive capabilities of ecosystem service assessments in urbanizing high-altitude regions.