Evaluating the thermal impacts of urban corridor redevelopment and greening interventions in Addis Ababa using multi-temporal satellite data and machine learning

Abstract

Rapid urbanization and infrastructure expansion are fundamentally reshaping land surface thermal dynamics in Sub-Saharan African metropolises, yet the combined microclimatic impacts of simultaneous urban greening and corridor redevelopment remain understudied. This study systematically evaluated the spatiotemporal thermal and biophysical changes in Addis Ababa, Ethiopia, driven by the Corridor Development Projects between 1990 and 2025. Utilizing multi-temporal Landsat satellite imagery, we employed Random Forest machine learning classification alongside the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Built-up Index (NDBI) to quantify land-use and land-cover (LULC) transformations, surface temperature variations, and ecological severity via the Urban Thermal Field Variance Index (UTFVI). Over the 35-year period, built-up areas expanded nearly fourfold from 14.8% to 53.3%, primarily encroaching upon agricultural lands, while net vegetation cover contracted from 13.8% to 8.1%. Consequently, mean Land Surface Temperature (LST) increased by 5.06 °C (from 29.43 °C to 34.49 °C), expanding severe ecological heat stress (UTFVI ≥ 0.02) to 48.0% of the municipal area, with Bole, Akaki-Kality, and Kirkos emerging as considerable vulnerability hotspots. Bivariate spatial correlations confirmed strong cooling effects driven by elevation (r = −0.60 to − 0.68) and vegetation (r = −0.57 to − 0.71), contrasting with intense surface heating from built-up density (r = 0.54 to 0.63). The surface urban heat island (SUHI) intensity for Addis Ababa increased consistently from 0.40 °C in 1990 to 1.31 °C in 2025, reflecting faster urban warming than rural areas and a strengthening SUHI effect at an estimated rate of 0.026 °C per year over the study period. These findings expose a vital socio-ecological trade-off: localized corridor greening alters microclimate structure but cannot fully counterbalance city-wide warming from impervious surface expansion. Integrating thermal comfort metrics and minimum vegetation cover ratios into spatial planning is essential for climate-resilient urban development.