An urban ecological synthesis of socio-ecological systems dynamics in Potchefstroom, South Africa

PhD (Environmental Sciences), North-West University, Potchefstroom Campus, 2015

As rural populations decrease and cities expand, the importance of urban ecological research becomes globally significant. Urban ecology seeks to understand the complex relationships between human settlements and their ecological contexts in an attempt to ensure sustainable futures. The discipline of urban ecology is at the forefront of the conflict between human perceptions, economy, and politics. Despite numerous studies conducted in urban areas in South Africa, no one city has yet synthesized all the amassed research conducted within its city limits. A shortage of detailed ecological data, therefore, led to an extensive study of urban open spaces in some cities of the North-West Province encompassing multiple disciplines. Consequently, this study attempts to consolidate and evaluate all the existing urban ecological research in South Africa and specifically, in the city of Potchefstroom. Firstly, a comprehensive overview of South African urban ecological literature discussing the early development, research themes and the future of urban ecology in South Africa was carried out. Three hundred and fourteen publications were reviewed and categorized into the following research themes: physical environment, biodiversity, management, conservation, planning, human needs, sustainability, public participation, ecosystem services, and resilience. Secondly, as researchers have long been interested in studying and explaining patterns of biodiversity in natural and anthropogenic landscapes, many theories have been proposed on the drivers of these patterns and numerous studies compare current land-use effects with biotic assemblages. However, a much-neglected perspective in urban ecological research is the impact of the history of the landscape. Consequently, the second paper investigated the possible time lags in the response of temperate natural grasslands to urbanization and the factors driving these changes. Thirdly, a study of the temporal vegetation dynamics of urban grasslands in Potchefstroom over a 17-year period was carried out. Open grasslands, woody vegetation sites, and vacant lots were resurveyed within the city limits. The potential change in species richness and abundance of species, and the differences in species composition between these three habitat types were compared. Lastly, the fourth paper synthesizes all the relevant existing interdisciplinary research carried out of urban open spaces in Potchefstroom. This is evaluated against municipal governance and management strategies, environmental law, public opinion and the steep spatially organized socio-economic gradient found in Potchefstroom, informing the progress towards a sustainable, liveable city. The results of the literature study indicated that there were various gaps within each theme that need to be addressed in future. In the study on the effects of urbanization history on observed vegetation patterns, the woody vegetation showed important time lags in the response of indigenous species richness to urbanization. The measures altitude and the road network density of natural areas were the most frequent predictors of species richness. Results of the temporal vegetation dynamics of urban grasslands indicated that in the relatively short 17 year period most vegetation diversity indices changed significantly, specifically a significant decrease in indigenous species richness of both grasslands and woody communities were noted. The synthesis of all the studies carried out in Potchefstroom revealed an impressive number of studies carried out, however most of the biodiversity groups were represented by a single investigation only. Evaluating the results with the IDP revealed than much of the known ecological information in Potchefstroom remains undiscovered by municipal policymakers. Moreover, proposed future development is planned for some of the highest biodiversity sites. This synthesis and the subsequent identification of the gaps in our understanding and research themes will allow a purposeful and informed advancement of the science of urban ecology in South Africa and the contribution thereof towards advancing urban ecology globally. In addition, the history of urbanization affects contemporary vegetation assemblages in urban areas indicating potential extinction debts. Moreover, the significant decreases in indigenous species richness of woody and grassland sites have important consequences for urban grassland conservation in South Africa. Subsequently, the knowledge and the identification of research gaps allow decision makers in Potchefstroom to plan for sustainable future solutions and for this city to emerge as a leading role player in the South African urban ecological context. The results of this thesis could be a substantial practical aid in policy and management strategies furthering decision makers in the pursuit of the elusive goal of developing sustainable cities.

Doctoral