Under the dual pressures of global climate change and human activities, the carbon sink function of terrestrial ecosystems and ecological vulnerability exhibit a dynamic game relationship. To address the inadequacies in carbon dynamic assessment methodologies and the unclear driving mechanisms in ecologically fragile regions (particularly karst desertification areas), this study developed an integrated framework of "remote sensing monitoring-model coupling-scenario prediction". Focusing on Guangxi's karst desertification region, we analyzed the spatiotemporal evolution of carbon sinks and human-land coupling driving mechanisms from 2000 to 2020, while projecting future trajectories of carbon storage. The research findings indicate that (1) Rocky desertification control measures have significantly reduced the area of severely degraded land, with a 74.5 % decrease in extremely severe rocky desertification. However, latent risks persist, forming an "explicit improvement-implicit risk" coexistence. (2) Vegetation net primary productivity (NPP) exhibited a fluctuating upward trend (2000-2020), spatially characterized by lower values in central regions and higher values at the periphery. The carbon sink-source system has undergone a three-stage evolution of "rapid repair-dynamic balance-game adjustment," spatially manifesting as "marginal carbon fixation-central emission." (3) Partial least squares structural equation modeling (PLS-SEM) revealed that carbon loss stems from the interaction of natural constraints and human interference. Topography indirectly regulates carbon sinks by modulating climate and human activities, while vegetation suppression by human activities emerged as the primary driver of carbon loss. (4) Multi-scenario analyses predict that carbon storage in 2030 will retain the spatial differentiation observed from 2000 to 2020, maintaining a "high-edge, low-center" pattern. The sustainable development pathway (SSP1-2.6) yielded the most pronounced carbon storage gains. These findings provide a scientific foundation for optimizing carbon neutrality strategies in karst regions and insights for global carbon management in analogous geomorphic areas.