Department of Geography and Environmental Studies

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Browsing Department of Geography and Environmental Studies by browse.metadata.advisor "Biggs, Reinette, 1979-"

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    Applying remote sensing and spatial analysis to investigateregime shifts in the Albany Thicket of the Baviaanskloof
    (Stellenbosch : Stellenbosch University, 2023-03) Matowanyika, Danai; De Klerk, Helen; Maciejewski, Kristine; Biggs, Reinette, 1979-; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
    ENGLISH ABSTRACT: Human activities have greatly altered the environment, the scale of impact has led to a new geological epoch - the Anthropocene. Of particular concern in this new era is the possibility for regime shifts: large, persistent changes in the structure and function of ecosystems that can have substantial impacts on human well-being and livelihoods. The Baviaanskloof is a semi-arid ecosystem in Southern Africa that has been substantively transformed by human activities. The Baviaanskloof, is located in the unique Thicket biome, characterized by dense spekboom thicket vegetation (Portulacaria Afra). Remote sensing and geoinformatics tools were used to investigate possible regime shifts in the Baviaanskloof, with a focus on regions classified as Baviaanskloof Thicket biome. The regime shift being investigated is the potential shift from an intact Thicket to a pseudo-Savanna Thicket regime. The thesis combined remotely sensed Enhanced Vegetation Index (EVI) from the MODIS platform as a surrogate of biomass and rainfall data from local weather stations over the period 2000 – 2018, complemented with observations from a field visit in Baviaanskloof Heartland area (BHB) in 2018. The BHB has been an active site for ongoing spekboom rehabilitation initiatives. Analytical tools, Break Detection for Additive Seasonal and Trend (BFAST), Sequential t-Test Analysis for Regime Shifts (STARS) and Green-Brown were used to investigate potential regime shifts. Different tools analysed different aspects of biomass changes in the Baviaanskloof, generally showing persistent decreases. Green-Brown showed that majority of the Baviaanskloof did not experience significant annual changes, but experienced significant seasonal changes. Most of the significant changes were decreases in biomass, with 58% of the Bavianskloof experiencing seasonal decreasing trend.Within the Thicket biome specifically, 77% of the area experienced significant biomass decreases. Majority of the changes occurred in the more arid vegetation classes (Groot Arid Spekboomveld), a possible early warning indicator of what lies ahead for the biome. BFAST and STARS detected two major breaks points in the Thicket biome in 2004 (2001 for STARS) and 2011. BFAST showed a decreasing trend of biomass in between and after both break points. STARS also identified a period of relatively low biomass between 2001 and 2011, a period of relatively higher biomass between 2011 and 2016, and a drastic drop in biomass after 2016 in the Thicket biome. The magnitude of the second break points is bigger than that of the first break points for both models. Spatial mapping of breakpoints showed majority of the Thicket biome (87.91%) experienced at least two break points, mostly negative break points experienced in the drier Groot Arid Spekboomveld regions. The thesis also anaylsed the effect of rehabilitation efforts at specific sites within the BHB. The BHB spekboom plantings of 2010-2013 initially showed an increase in biomass, followed by a decreasing trend. This variations in biomass patterns show that the Baviaanskloof is a complex system with spatial and temporal dynamism. The geoinformatics and analytical tools used in this study provided meaningful insights into investigating possible regime shifts in the Baviaanskloof, and was able to analyse these spatially and detect significant break points. This points to the potential for these tools in detecting regime shifts.