The importance of private gardens and their spatial composition and configuration to urban heat island mitigation

Small Urban Green Infrastructure (UGI; green areas < 2 ha) represents the best opportunity to mitigate Urban Heat Island (UHI) and directly promote microclimate regulation. However, few studies investigate the cooling capacity (CC) of small UGI and how their spatial organization influences its provision. Here, we used an urban cooling model and landscape metrics to understand how UGI in public and private domains influences microclimate regulation in a dense urban region of Rio de Janeiro. Our findings highlight the significant correlation between private UGI and CC, explaining over 80% of its variation. We found an interaction between UGI composition (i.e. the amount of UGI) and configuration (i.e. spatial distribution of UGI). Nevertheless, UGI configuration exerted the greatest influence with edge density being the most significant landscape metric, suggesting that, with an equivalent green area, patchwork or numerous smaller green areas enhance CC compared to fewer larger ones. This study underscores the pivotal role of private UGI organization in tropical and dense urban context, where public UGI is neglected. We conclude that UGI awareness initiatives must systematically pay attention to spatial configuration of the small UGI, aligning interventions with urban dwellers' needs in order to guarantee microclimate regulation provision.