How does Blue-Green Infrastructure affect the urban thermal environment across various functional zones?

Considering the limited availability of urban Blue-Green Infrastructure (BGI), a principal area of focus in this research is identifying methods to maximize their cooling effects more effectively. Previous research has identified varying dominant factors in mitigating the urban heat island effect through the spatial arrangement of BGI. However, research on the specific mechanisms of these factors within different urban functional zones (UFZs) and their interactions with human activities remains insufficient. In this research, the influence of the BGI landscape index on surface temperature in different UFZs is explored through a random forest model, using Changchun, China as a case study. Results indicate that 1) Reducing the patch density of Green Infrastructure to 50 patches/ha can effectively lower surface temperature in Ecological Zones. 2) In other UFZs, the percentage of landscape of Green Infrastructure typically acts as a crucial factor contributing to the cooling effect. 3) Enhancing connectivity and proportional area of Blue Infrastructure markedly advances the cooling impacts in Ecological Zones. This study offers data-driven empirical evidence for advancing urban planning and environmental management strategies. It emphasizes the need to incorporate proper BGI patterns and urban functions in planning processes to effectively mitigate the urban heat island effect.