Quantifying the relationship between urban blue-green landscape spatial pattern and carbon sequestration: A case study of Nanjing’s central city

Against the background of global warming, urban blue–green spaces (UBGS) are important carbon sequestration (CS) carriers that can reduce carbon emissions. However, previous studies on urban CS were mostly limited to urban green or blue spaces separately and lack a comprehensive consideration of the synergistic impact of UBGS on CS. In addition, research on the driving mechanism between urban blue–green spatial patterns (UBGSP) and CS has so far been insufficient. Therefore, in this study, we explored the correlation between UBGSP and CS, identified the affecting UBGSP factors, and proposed suggestions for planning design. We identified the UBGS of the central city of Nanjing based on Landsat-8, calculated the CS using the Carnegie-Ames-Stanford approach (CASA), and analyzed the relationship between the UBGSP and CS at both class and landscape levels by establishing sets of UBGSP indicators. At the class level, the percentage of landscape and aggregation index have positive effects on CS, whereas the landscape division and shape indexes have negative effects. Moreover, edge density and area-weighted patch fractal dimension do not correlate with CS. At the landscape level, connectance can promote the CS of UBGS. Finally, we found that the largest patch index, edge density, Shannon's evenness index, patch cohesion index, and contagion have no significant effects. The results of this study contribute to the systematic optimization of UBGSPs, promote the integrated development of UBGSs, and provide references for urban planning practices and resource management.