Urban green infrastructure and microclimate regulation in intermediate cities

Accelerated urbanisation in the Global South alters the surface energy balance, intensifying the Urban Heat Island (UHI) effect. This study analysed the microclimatic impact of green infrastructure in tropical intermediate cities to inform a climate adaptation model. Ambient air temperature (Ta), relative humidity, and light intensity were monitored in situ across 38 sampling zones (comprising 7 categories and 5 structural canopy subcategories) in Villavicencio, Colombia; additionally, its green density was geospatially compared with Bucaramanga and Neiva using QGIS. The results demonstrated that UHI mitigation depends strictly on structural architecture (subcategory) rather than nominal land use (category). Waterways (Subcategory 5: high tree density and permeable soil) acted as efficient thermal sinks, depressing the mean temperature below the meteorological baseline (x̄ = 28.91°C; ΔT = -0.24°C). In contrast, vacant lots without canopy cover (Subcategory 1) recorded maximum thermal stress (x̄ = 32.12°C; ΔT = +2.97°C). The cross-city analysis revealed a low, homogeneous green density across the three urban centres (p = 0.7127). To address this deficit, the prospective "Garden City" scenario was modelled a Nature-based Solution that increases eco-structural density 3.7 times (6.01 to 22.15 green areas/km²; p = 6.928 × 10⁻⁴) utilising native species, thereby offering a transferable and scalable urban planning framework.