Vegetation-Based Strategies for Urban Heat Mitigation and Outdoor Thermal Comfort Enhancement in Hot-Arid and Mediterranean Cities: A Scoping Review

In the last century, urban growth has increased rapidly in most cities worldwide, contributing to the loss of natural areas, greater impervious surfaces, and urban density. This has led to elevated temperatures and the development of the urban heat island (UHI) effect. The UHI effect can significantly impact the environment, economy, public health, and overall urban livability. Abundant studies have proven that vegetation is the most effective strategy to mitigate urban heat through shading provision and evapotranspiration. However, despite the growing body of literature on vegetation-based cooling strategies, the influence of climatic conditions on its cooling performance remains insufficiently understood. This scoping review examines the UHI characteristics and maps the evidence on the effectiveness of vegetation-based strategies in reducing urban temperatures and enhancing outdoor thermal comfort in two different climates: hot arid (Köppen BWh) and Mediterranean (Köppen Csa). Peer-reviewed English language studies published between 2010 to 2026 were identified through Scopus, Web of Science, and ProQuest, with the final search conducted in April 2026. Following a screening and eligibility assessment, data from 127 included studies were synthesized quantitatively and qualitatively. The results show that, while hot-arid cities may exhibit nighttime canopy urban heat island (CUHI) and surface urban heat island (SUHI) effects and daytime canopy urban cool island (CUCI) and surface urban cool island (SUCI) effects, Mediterranean cities generally experience the CUHI and SUHI effects during both day and night. Moreover, the cooling capacity of vegetation varied according to vegetation type, configuration, density, local climate, water availability, and urban context. Consequently, developing a universal applicable solution for vegetation-based strategies with a consistent cooling performance across different climates and urban conditions is a real challenge.