## 4 Discussion
### Decision-Making of Targeted Development Strategies  
Currently, in the context of China's ongoing push for new urbanization and urban renewal in major cities, optimizing urban ecological spatial patterns emerges as a crucial task. The GWR-RF-SEM attribution analysis framework has thoroughly assessed the contribution and causal processes of carbon sequestration (CS) across 197 counties in China's most developed urban agglomerations. The gained insights are instrumental in scientifically guiding these urbanization policies.  
Coordinated urban and county-level strategies: The enhancement of urban vegetation's CS capacity necessitates a coordinated strategy that encompasses both municipal districts and the surrounding counties. Due to the desynchronization between urbanization levels and carbon emissions across regions [83], it is possible to reduce carbon emissions within cities by strategically optimizing the location and scale of land designated for construction. Inter-city collaboration, accounting for the spillover effects of carbon emissions, can promote regional collaborative emission reductions, particularly through the coordination between developed areas and their peripheries. This fosters the coordinated development of neighboring regions and supports collective emission reductions. In this context, recognizing the high CS potential of green spaces, such as forests, is crucial for regional coordinated development. Based on factors including population density, nighttime illumination, nitrogen deposition, and soil nitrogen and phosphorus content, the selection of appropriate natural vegetation for cities and their adjacent counties is also of great importance. For rural and suburban areas, choosing vegetation species with the highest CS potential can effectively increase the regional carbon sink. It is estimated that, if all vegetation with carbon advantages were selected, China's entire forest ecosystem could offset 7-14% of the current fossil carbon emissions by 2060 [84]. In urban areas, where improved lighting and thermal conditions are more favorable for carbon fixation [43; 76], the effective maintenance of street trees and green belts will also contribute to the rapid achievement of regional carbon neutrality.  
Wetland-sensitive afforestation: In the plains of the Yangtze River Delta, which are characterized by an extensive network of waterways and wetlands, the selection of sites for afforestation must be approached with caution. The objective should be to minimize any adverse effects of afforestation on the CS functions of these critical wetland ecosystems. The plains of the Yangtze River Delta, with their dense network of waterways and numerous wetlands, are subject to increased carbon emissions from water bodies due to eutrophication caused by various wastewater sources, which correlates positively with the level of socio-economic development. Focused protection of these wetlands is essential. Additionally, the selection of sites for afforestation must be carefully considered, with the goal of minimizing the negative impact on the CS capabilities of these vital wetland ecosystems. It is also proposed to establish a wetland protection fund for urban agglomerations to compensate for the economic losses incurred by development restrictions in outside districts oriented toward wetland protection and to provide financial support for regional wetland conservation.  
Customized policy framework: Our identification of 14 key drivers influencing CS in the 197 counties of the YRDUA provides a valuable reference for crafting tailored CS policies at the county level. This localized approach is pivotal, as it recognizes the unique environmental, economic, and social contexts of each county.  
These findings and recommendations highlight the importance of nuanced, data-driven approaches to urban ecological planning, essential for fostering sustainable urban development and enhancing the environmental health of China's rapidly urbanizing regions.