Objective Collaboratively promoting carbon reduction, pollution reduction, green expansion, and growth, while maintaining national ecological security, has become a key focus area in national strategic planning in recent years. However, rapid urbanization has compressed carbon sink spaces such as forest land and grassland, leading to a significant decline in environmental quality and soil carbon sink capacity. Currently, existing research on carbon sink spaces is limited, and it is mostly concentrated on regional scales with superior ecological environments and rich vegetation cover. Research on rapidly urbanizing areas with poor carbon sink backgrounds is relatively scarce. Therefore, analyzing the spatio-temporal evolution characteristics of carbon sinks in highly urbanized areas with weak carbon sink backgrounds and conducting multi scenario simulation analysis. To provide a basis for optimizing the spatial layout of the country and formulating differentiated carbon sink enhancement strategies, thus contributing to maintaining regional ecological security and achieving high-quality development.

Methods This study focuses on southern Jiangsu region, where urbanization is predominant and carbon sink spaces face intense competition with construction spaces. At the township scale, the carbon sink space is analyzed and classified using specific criteria. The PLUS (patch-generating land use simulation) model is used to analyze the spatio-temporal evolution characteristics of carbon sink space from 2000 to 2020, and proposes differentiated strategies based on simulation results of various future development scenarios.

Results This study focuses on the town carbon sink space in rapidly urbanizing areas, revealing that the evolution of carbon sink space in rapidly urbanizing areas is the result of the combined effects of natural factors, policy interventions, and town development stages. It has important theoretical and practical value for optimizing the national spatial pattern and achieving carbon neutrality goals, providing scientific support for the green transformation of new urbanization in developed areas. The research indicates four results. 1) From 2000 to 2020, the loss of carbon sink spaces in the Sunan region was not uniform but highly concentrated in high-value carbon sink areas. 2) The structure of carbon sink spaces in the Sunan region at the town scale did not completely disintegrate due to urbanization; instead, it demonstrated remarkable stability. 3) Simulation results show that different intensities of carbon sink protection measures can promote the expansion of high-quality carbon sink spaces. However, a "carbon sink enhancement scenario" is not necessarily optimal. The pursuit of a "high carbon sink coefficient" alone should be avoided, and the risk of ecological function simplification needs to be guarded against. 4) Towns in the Sunan region can be categorized into three types: those with high carbon sink capacity, high carbon sink potential, and high construction intensity. Most towns have maintained their original carbon sink spatial structure characteristics under three simulated scenarios, and in the future, they can focus on exploring the potential of existing space to protect and optimize carbon sink space. For sensitive town types—those with easily fluctuating carbon sink quality, those prone to carbon sink function degradation, and those with clearly degraded carbon sink functions—more targeted strategies should be implemented based on the specific risk types.

Conclusion Through multi scenario simulation, the evolution patterns of future urban carbon sink spaces can be analyzed and predicted, offering references for the protection and optimization of urban carbon sink spaces in rapidly urbanizing areas. This study can scientifically analyze the dynamic evolution laws of regional carbon sink space, explore the optimization path and has significant theoretical and practical value for optimizing territorial spatial patterns and achieving carbon neutrality goals, thus providing scientific support for the green transformation of new urbanization. This method can be widely applied to similar studies on town ecological space planning related to carbon sink enhancement, and helps other cities, especially those with rapid urbanization, to achieve coordinated and sustainable development of ecological environment and economy.