Unequal heat: Urban form, land cover change, and socioeconomic vulnerability in greater Kumasi, Ghana

Abstract

Rapid urbanization in developing cities increases thermal stress, but the links between urban form and socioeconomic vulnerability remain poorly understood. This study examines spatial and temporal changes of land surface temperature (LST) and Urban Heat Island (UHI) in Greater Kumasi, Ghana, using Landsat data from 2015 to 2024. It connects thermal patterns to urban form, Normalized Difference Built-up Index (NDBI), Bare Soil Index (BSI), Normalized Difference Vegetation Index (NDVI), and Normalized Difference Moisture Index (NDMI), along with socioeconomic indicators like population and Relative Wealth Index. The analytical techniques include trend detection (Mann–Kendall, Sen's slope), correlation analysis, hotspot mapping, and spatial overlays. The results reveal distinct warming trends, with annual LST increases of up to 1.53 °C and UHI intensification of 0.7 °C in areas such as Sokoban, Magazine, and Kumasi Central. Strong positive correlations between thermal metrics and built-up areas and bare soil underscore the significant role of impervious surfaces in heat accumulation, while weaker and positive relationships with NDVI and NDMI indicate limited cooling from vegetation and moisture. The hotspot analysis demonstrated that extreme thermal conditions predominantly affect high-density and lower-income areas, revealing patterns of unequal heat exposure linked to socioeconomic disadvantages. These findings underscore the need for equity-driven urban heat mitigation strategies, particularly nature-based solutions and climate-conscious planning, to address rising thermal risks in rapidly expanding African cities.