Patterns and drivers of land cover change in the City of Tshwane, South Africa, with a focus on change dynamics in ecologically sensitive areas

Abstract

Urban expansion drives land use and land cover change (LULCC), yet the exact drivers of this change, especially at localised scales, are not always known. Furthermore, urban natural areas, essential for biodiversity conservation and ecosystem services, are often transformed to other uses. This study examined spatiotemporal patterns and drivers of LULCC in the City of Tshwane (CoT), between 1990 and 2022. The objectives were to (1) describe LULCC, (2) identify drivers of LULCC, (3) identify drivers of LULCC in areas of natural vegetation, and (4) identify drivers of LULCC in riverine areas across the CoT. We compared land cover between 1990 and 2022 to assess LULCC, with a particular focus on transformations from ecologically sensitive natural vegetation and riverine areas to other land cover types. Generalised Linear Models and Geographically Weighted Regression were used to evaluate how socioeconomic and environmental variables influenced LULCC. Overall, 25.9% of the CoT experienced change in land cover between 1990 and 2022. Notable increases were seen in bare land (2902.9%), built-up areas (105.5%), and formal residences (95.6%), while recreational areas, natural vegetation, and waterbodies declined by 41.7%, 20.6%, and 16.5% respectively. Natural vegetation was mostly converted to cultivated land, built-up areas, and formal residences. Riverine areas experienced increases in cultivated land, built-up areas, formal residences, and bare land, and decreases in natural vegetation. Across the CoT, LULCC was more likely to occur in areas of higher population density, and closer to roads. However, geographically weighted regression revealed spatial heterogeneity in the strength, and in some cases the direction, of drivers of LULCC. In areas of natural vegetation, population density best predicted LULCC, while in riverine areas, distance to roads had a strong negative association with LULCC. These findings highlight that both human demography, and site accessibility, are important drivers of urban expansion, possibly leading to significant biodiversity losses.