Evaluating the Benefits of Urban Greenery in Urban Heat Island Mitigation: Methods, Indicators and Gaps

Urban Heat Island (UHI) effects pose a significant environmental challenge in contemporary urban planning, driven by accelerating climate change, rapid urban development, and changes in land use patterns. This study explores the potential of urban greenery as a mitigation strategy for UHI by conducting a systematic and bibliometric review of 42 peerreviewed studies, selected using the PRISMA 2020 protocol. A mixed methods approach was employed, integrating a systematic review with a critical content synthesis of selected studies using PRISMA 2020 and bibliometric mapping using VOSviewer (1.6.19). The results indicate that urban greenery, encompassing green roofs, vegetated facades, urban forests, and street trees, plays a critical role in mitigating surface and air temperatures by enhancing evapotranspiration, increasing surface reflectivity (albedo), providing shading, and improving urban ventilation dynamics. Widely used indicators in these studies include Land Surface Temperature, the Normalized Difference Vegetation Index, and canopy coverage. The bibliometric analysis reveals exponential growth in related publications between 2014 and 2024, is an R2 = 0.8263, along with emerging thematic clusters centered on thermal comfort modeling, nature-based solutions, and urban climate resilience. China, Australia, and the United States account for the majority of contributions, while tropical and lower-income regions remain underrepresented. The findings highlight critical thematic and geographic gaps, emphasizing the need for future research incorporating empirical validation, field experimentation, and integrative modeling to advance equitable and context-sensitive UHI mitigation strategies.