Objective This study focuses on the coupled relationship between land-use/cover change (LUCC) and ecosystem carbon stock in the Changsha–Zhuzhou–Xiangtan urban agglomeration. By developing multiple development scenarios, we project future carbon stock trends, providing a scientific basis for enhancing regional carbon stocks and contributing to the achievement of China’s “Dual Carbon” strategic goals.

Methods This study couples the PLUS-InVEST model to analyze land-use changes (2000–2020) and associated carbon stocks dynamics in the study area. Based on 14 driving factors, we project 2040 land-use patterns and carbon stocks under four scenarios: Natural development, 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, cropland, forestland, and grassland showed a decreasing trend, while waterbody 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 stocks in the Chang-Zhu-Tan urban agglomeration showed a decreasing trend. The total carbon stocks in 2000, 2005, 2010, 2015, and 2020 were 394.7 × 10⁶ t, 393.5 × 10⁶ t, 390.1 × 10⁶ t, 388.1 × 10⁶ t, and 385.9 × 10⁶ t, respectively. The spatial heterogeneity was remarkably distinct, exhibiting a characteristic "high in the southeast and low in the northwest" distribution pattern, with forestland areas served as the primary carbon source while maintaining substantial carbon stoock capacity. 3) Land use changes directly impacted carbon stocks. From 2000 to 2020, the conversion of forestland to built-up land resulted in a decrease of 5.6 × 10⁶ t in carbon stocks, while the conversion of cultivated land to built-up land led to a reduction of 3.0 × 10⁶ t in carbon stocks. The conversion of cultivated land to forestland increased carbon stocks by 2 × 10⁶ t. 4) The predictions for 2040 indicate a decreasing trend in carbon stocks across all four scenarios, with values of 382 × 10⁶ t, 382.5 × 10⁶ t, 381.7 × 10⁶ t, and 382.7 × 10⁶ t, 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 stocks reduction. To enhance regional carbon sequestration, future territorial spatial planning should consider the four scenarios proposed in this study: Natural development, 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.