Urban vegetation structure and composition influence pedestrian thermal comfort in public spaces: A case study in Munich

Abstract

Urban green infrastructure is widely recognized for moderating urban heat, yet the impact of different vegetation types and structure on human thermal comfort remains poorly understood. We quantified how vegetation structure and composition affect thermal comfort across 16 public squares in Munich during the summer of 2022. The squares featured varying proportions of different vegetation types and their structure (grass, shrubs, and trees). Meteorological variables were measured at pedestrian height to calculate physiological equivalent temperature (PET). Vertical and horizontal vegetation complexity was quantified through an index, while cooling efficiency was assessed via PET. High structural complexity sites showed significantly greater cooling on hot summer days (ΔPET = -5.1 ± 0.3°C) compared to low complexity sites (ΔPET = -0.5 ± 0.3°C). Low and medium-height trees demonstrated stronger cooling than tall trees. Each 1% increase in tree cover reduced PET by 0.17 ± 0.02°C, nearly three times more than shrub cover (0.06 ± 0.02°C) and significantly more than grass cover (0.015 ± 0.007°C). Built environment characteristics significantly influenced thermal conditions, with positive correlations between ΔPET and both building volume and impervious surfaces. Our findings demonstrate that multi-layered vegetation structures enhance cooling in urban spaces. The higher cooling performance of low and medium-height trees suggests that vegetation structure should be strategically considered in urban green space design, particularly in public squares where pedestrian thermal comfort is paramount. While derived from a temperate European city, these relationships may be applicable to similar urban morphological and climatic contexts. Further research is needed to evaluate their transferability across contrasting climate settings. • Structurally complex vegetation reduces pedestrian heat stress significantly in public squares • Cooling trade-offs include reduced wind speed and increased humidity • Low and medium trees cool more effectively than tall trees at pedestrian level • Tree cover cools PET three more than shrubs, and almost 11x more than grass cover

Topics & Concepts