Abstract
Rapid urbanization and climate change have exacerbated the Urban Heat Island (UHI) effect in global megacities, disproportionately impacting vulnerable urban populations and escalating heat-related morbidity and mortality. This study presents a comparative geospatial and epidemiological assessment of the mitigating impacts of urban green infrastructure (UGI) across three high-density megacities: Tokyo, London, and São Paulo. Leveraging multi-temporal satellite imagery from Landsat 8/9, Sentinel-2, high-resolution municipal Land Surface Temperature (LST) data, and localized public health registry datasets over a five-year period (2018–2023), we quantified the cooling efficiency of various UGI typologies—including urban parks, street canopies, and green roofs—and analyzed their correlation with heat-related emergency hospital admissions. Spatial regression models revealed that canopy cover percentage and patch connectivity exerted the strongest cooling effect, yielding average local LST reductions of 1.8°C to 3.4°C within a 300-meter buffer. Furthermore, generalized additive models demonstrated that a 10% increase in localized vegetative cover was associated with a 7.2% to 11.5% decrease in relative risk for heat-induced cardiovascular and respiratory hospital admissions during extreme heat events. These findings underscore the imperative of strategic, connected green infrastructure planning as an evidence-based, cross-sectoral intervention for climate adaptation and public health resilience in high-density urban environments.
