Linking major shifts in land surface temperatures to long term land use and land cover changes: A case of Harare, Zimbabwe

Abstract

Rapid urban development is known to increase a landscape's thermal values, exposing residents to among others adverse heat related health impacts, discomfort as well as energy and water demand. Therefore, there is need to determine the implication of the transforming urban landscapes on urban micro-climate to optimise urban land uses and to effectively mitigate adverse impacts. In this study, we aimed at assessing micro-climate forcing of Land Use and Land Cover (LULC) changes in the heterogeneous Harare Metropolitan City, Zimbabwe, between 1984 and 2015. To achieve this objective, the transformation of major LULCs within the city was determined and relative brightness temperature used to assess long-term thermal changes in the city. Results show that coverage of high density residential areas increased by 92% between 1984 and 2016 at the expense of cooler green-spaces, which decreased by 75.5%. This translated to a 0.98°C and 1.98°C temperature increase, attributed to LULC changes alone and to all factors that include greenhouse effect and ozone depletion respectively. Results also show that converting bare areas to water bodies reduced surface temperatures by 4.5°C, while the construction of low-to-medium density residential areas reduced bare surface temperatures by 3.78°C. Conversion of green-spaces to low-medium residential areas increased temperatures by 0.16°C. Overall, conversion of LULC types contributed more than 0.5°C thermal elevation within the city, largely attributed to increases in built-up areas and reduction in heat mitigating green-spaces. These findings offer insight into landscape surface energy balance changes arising from urbanization, critical for urban planning, environmental governance as well and climate change management in cities.