Abstract: Background Quantitative assessment and prediction of spatiotemporal changes in land use and ecosystem carbon storage are crucial for enhancing regional carbon sequestration and achieving China's Dual Carbon goals. Current research on carbon storage in urban agglomerations remains limited. This study investigates how land-use/cover change (LUCC) affects ecosystem carbon storage in the Changsha-Zhuzhou-Xiangtan (CZT) urban agglomeration. Through scenario-based modeling of different development pathways, we predict future carbon storage trends to provide scientific support for regional carbon management, thereby contributing to the realization of China's Dual Carbon strategy. Methods This study couples the PLUS-InVEST model to analyze land-use changes (2000–2020) and associated carbon storage dynamics in the study area. Based on 14 driving factors, we project 2040 land-use patterns and carbon storage under four scenarios: Business-as-Usual, Cropland Protection, Economic Development, and Ecological Conservation. The results reveal how different land-use policies influence carbon sequestration, providing a scientific basis for optimizing territorial spatial planning to enhance regional carbon storage capacity. Results 1) From 2000 to 2020, Cultivated land, forest land, and grassland showed a decreasing trend, while water bodies and built-up areas exhibited an increasing trend. The trend of unused land remained stable in the Chang-Zhu-Tan urban agglomeration. 2) From 2000 to 2020, the total carbon storage in the Chang-Zhu-Tan urban agglomeration showed a decreasing trend. The total carbon storage in 2000, 2005, 2010, 2015, and 2020 were 394.7×10⁶t, 393.5×10⁶t, 390.1×10⁶t, 388.1×10⁶t, and 385.9×10⁶t, respectively. The spatial heterogeneity was remarkably distinct, exhibiting a characteristic "high in the southeast and low in the northwest" distribution pattern, with Forest areas served as the primary carbon source while maintaining substantial carbon storage capacity. 3) Land use changes directly impacted carbon storage. From 2000 to 2020, the conversion of forest land to built-up land resulted in a decrease of 5.6×10⁶t in carbon storage, while the conversion of cultivated land to built-up land led to a reduction of 3.0×10⁶t in carbon storage. The conversion of cultivated land to forest land increased carbon storage by 2×10⁶t. 4) The predictions for 2040 indicate a decreasing trend in carbon storage across all four scenarios, with values of 382×10⁶t, 382.5×10⁶t, 381.7×10⁶t, and 382.7×10⁶t, respectively. Conclusions The study demonstrates that the conversion of high-carbon storage land types (e.g., forestland and cropland) to low-carbon types (e.g., construction land) is the primary driver of carbon stock reduction. To enhance regional carbon sequestration, future territorial spatial planning should consider the four scenarios proposed in this study: Business-as-Usual, Cropland Protection, Economic Development, and Ecological Conservation. These scenarios provide a scientific basis for optimizing land-use allocation to mitigate carbon loss while balancing socioeconomic development and ecological preservation needs.