A landscape connectivity approach to mitigating the urban heat island effect

Context Urban integration has exacerbated the spreading of urban heat islands (UHIs) across cities. Blue/green landscapes embedded within urban areas, behaving as cool islands (CIs), have been highly focused due to their efficient cooling effects. Objectives Previous studies on the cooling effect of blue/green landscapes are mainly focused on isolated patches of CIs, which cannot provide a stable cooling service compared to connected ones. Thus, based on the 'source-corridor-network' paradigm, a new approach to mitigating cross-regional UHI effects was proposed through improving the connectivity of CIs. Methods Taking Guangzhou-Foshan Metropolitan Area (GFMA), one of the most densely settled regions in China, as the case study context, the localized contour tree method, minimum cumulative resistance model, and complex networks were integrated to identify and evaluate the source areas and connecting corridors of the cooling network. Results 35 cooling sources and 78 CI connecting corridors were identified across the GFMA. CIs within built-up areas such as parks had higher cooling intensity acting to hinder UHI from spreading while CIs in mountainous areas offer larger cooling coverage. The CI connecting corridors in northeast GFMA were dense and short while those at the junction of the two cities were sparse and long, which should be highly focused. The cooling network was composed of the hierarchically constructed CI source areas and corridors, which provided impetus and stability for mitigating UHI effect respectively. Conclusions The landscape connectivity approach proposed in this study can serve as a cooling network strategy in metropolitan areas, revealing important policy implications for cities with potential cross-regional UHI threat.