Mechanisms and Case Studies of Urban Green Infrastructure in Mitigating Urban Heat Islands

Abstract

With the intensification of global climate change and the acceleration of urbanization, the Urban Heat Island (UHI) effect has become a significant environmental challenge impacting urban sustainability and public health. Urban Green Infrastructure (UGI), due to its ecological regulatory functions, is increasingly regarded as a nature-based solution to mitigate UHI. This paper systematically explores three core biophysical mechanisms by which UGI alleviates UHI: evapotranspiration, shading and physical cooling, and improved surface albedo. Empirical case studies from Beijing and Fuzhou are used to verify these mechanisms and optimization strategies. The findings indicate that evapotranspiration significantly reduces local temperatures through latent heat absorption, functioning as a primary cooling mechanism. Shading reduces solar radiation absorption and enhances human thermal comfort, while increased surface albedo helps lower heat accumulation. The case in Beijing shows that small-scale, distributed green spaces (e.g., multi-layered vegetation) in dense urban areas can reduce surface temperatures by 3–6°C. In Fuzhou, the optimized spatial layout of green areas combined with prevailing wind directions formed effective ventilation corridors, contributing to a temperature difference of 2–3°C. This study emphasizes that merely increasing the quantity of green space is insufficient; the quality and spatial configuration are critical to achieving systematic thermal regulation and enhancing urban climate resilience.