Department of Geography and Environmental Studies

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Browsing Department of Geography and Environmental Studies by browse.metadata.advisor "De Klerk, Helen"

Now showing 1 - 4 of 4
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    Advancing disaster risk management in an ecological context: the case of veldfire management in South Africa
    (Stellenbosch : Stellenbosch University, 2023-03) Forsyth, Gregory Graham; De Klerk, Helen; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
    ENGLISH ABSTRACT: Worldwide vegetation fires in peri-urban and rural settings pose a major hazard to social, economic and environmental assets. In South Africa, such fires are known as veldfires and they are necessary for maintaining natural processes in the fynbos, savanna and grassland biomes. Paradoxically, despite veldfires being ecologically beneficial, they often pose a risk to people and their property. This is especially so in the wildland–urban interface where buildings are found in the proximity of flammable vegetation. South Africa’s National Veld and Forest Fire Act, No. 101 of 1998 (South Africa 1998) provides a framework for setting priorities for veldfire management including the establishment of Fire Protection Associations (FPA). It seeks to find a balance between reducing risks to human lives and livelihoods while maintaining fire regimes which look after the functioning of fire-adapted ecosystems. Risk management offers a way for implementing this legislation and the National Veldfire Risk Assessment, completed in 2010, used risk management principles to establish the relative levels of veldfire risk in each of the country’s district and local municipalities. No detailed examination has been carried out of the applicability of the National Veldfire Risk Assessment framework and accuracy of nationally-generated veldfire risk information at local scales. This research addresses the gap between the National Veldfire Risk Assessment and how implementable this is to Fire Protection Associations and, at a finer scale, the wildland-urban interface. It examined three study areas typifying different spatial scales, climates, land-use practices, fuel types and assets at risk. It provides a systematic, stepwise, replicable, scalable assessment framework for determining veldfire risk that is in line with national policy (legislation). Importantly, it involves local stakeholders, and uses sound scientific ecological knowledge and established risk management principles to develop an accessible and practical methodological “tool” to identify different categories of risks at a range of spatial scales. In determining the risk, the likelihood of veldfire occurring was established, using combinations of the vegetation type and age, with the premise that the more flammable the vegetation the more likely a veldfire will occur. Consequences were decided on by identifying the types of buildings present and categorising the social and economic impacts should veldfire damage or destroy these buildings. The results were then mapped to show where vulnerable assets in the landscape are exposed to veldfires and in so doing enabling veldfire authorities to allocate resources according to the levels of risk present. This research has developed an accessible and practical “tool” to identify different categories of risks at a range of spatial scales and confirmed the relevance, applicability and scalability of the National Veldfire Risk Assessment framework. Adopting this approach will assist fire authorities to spend available budgets more effectively with more emphasis being placed on preventing rather than merely responding to veldfires. It will also assist in prioritising risk mitigation measures to prevent the inevitable future veldfires becoming disasters.
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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.
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    The influence of topographical variability on wildfire occurrence and propagation
    (Stellenbosch : Stellenbosch University, 2024-03) Christ, Sven; De Klerk, Helen; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
    ENGLISH ABSTRACT: Wildfires have increasingly become a point of concern, especially with notable incidents like the 2017 Knysna fire. These naturally occurring phenomena, despite their disruptive nature, are crucial for the sustainability of certain ecosystems. At the heart of understanding wild-fires lies the relationship between climate, vegetation, topography, and human land use, with topography standing out as a significant determinant. This thesis delves into the fundamen-tal role of topography, emphasizing its effect on the ignition, propagation, and behaviour of wildfires. Utilizing Digital Elevation Models (DEMs), the research extracts invaluable topographic data aiming to augment the understanding of wildfires, especially in mixed natural forest and fyn-bos ecosystems. Existing fire models have shown certain shortcomings, often overlooking crucial localized wind data, which has profound implications for predicting fire behaviour. By bridging this gap, the study explores the potential of computational fluid dynamics in modelling surface winds based on topography for fire research. The research systematically addresses several key objectives: Mapping the current land-scape of topography-cantered wildfire research and investigating the utility of DEM-derived surface wind in refining fire propagation models, identifying and analysing historical fire patterns to pinpoint fire refugia in the Knysna/Tsitsikhama region, employing machine learning techniques, to determine if topographic variables extracted from DEMs can antici-pate fire refugia. The findings underscore the salience of topography in wildfires. Especially significant is the role of aspect in determining fire refugia, emphasizing that a combination of multiple variables offers the most accurate insights. Machine learning, notably the XGBoost model, showcases potential in identifying critical topographical features impacting fire behaviours. Furthermore, the research sheds light on the pivotal influence of wind chan-nels, formed by topographical features, in both the inception and spread of wildfires. In summary, this thesis underscores the integral role of topography in understanding wild-fires. It charts a roadmap for future research, emphasizing the importance of high-quality validation data, a more comprehensive mapping of fire refugia, and an acknowledgement of the influence of human activity on fire regimes. By building on the methodologies and in-sights presented, there lies an opportunity to advance sustainable wildfire management so-lutions that benefit both ecosystems and human communities.
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    Scaling patterns and drivers of species richness and turnover across the Afrotropics
    (Stellenbosch : Stellenbosch University, 2017-03) Bailey, Junior Curtis; De Klerk, Helen; Hui, Cang; Munch, Zahn; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
    ENGLISH ABSTRACT: Understanding the broad scale patterns and environmental determinants of amphibian richness (α-diversity) and turnover (β-diversity) is becoming ever more crucial as communities, ecosystems and landscapes are increasingly threatened by anthropogenic processes and climate change. Spatial scale, the grain at which sampling takes place or analysis occurs, confounds understanding of such diversity patterns and the relationships these exhibit with environmental processes. This is because various processes operate at different spatial scales resulting in different patterns emerging at different spatial scales. This is problematic, because patterns, and pattern-process’ relationships which emerge at one scale may not hold at another scale thereby confounding our understanding of how biotic patterns are generated and maintained, thus leading to misguided conservation strategies and policies. The focus of the present study was thus to examine the relationship between present patterns of anuran richness and turnover, the relationship of these with several contemporary environmental processes, and how these patterns and pattern-process relationships are influenced by spatial grain. Using IUCN range data for the Afrotropical region, amphibian richness and turnover patterns were generated using a Geographic Information System and quantified using the recently formulated zeta diversity partitioning method (ζ). These patterns were then related to several contemporary environmental variables/processes hypothesised to govern amphibian diversity across a range of spatial scales using both the global Ordinary Least Squares (OLS) method and local spatial Geographically Weighted Regression (GWR) across three nested spatial grains. The results show that amphibian richness and turnover patterns (visual & empirical) and the relationships these exhibit with environmental conditions were sensitive to spatial grain. Visually, spatial patterns were more distinct at finer grains, but visibly smooth at the coarser grains. The statistics describing these patterns suggest that the scaling behaviour follows an increasing linear and nonlinear trend across spatial grain. Results from both the OLS and GWR models confirm that contemporary environmental conditions are significant determinants of both anuran richness and turnover patterns across spatial grain. Precipitation was the strongest determinant of anuran richness while topographic complexity best explained turnover. The relationship between both diversity components and environmental conditions, however, was scale dependent with environmental conditions explaining a greater proportion of the variation in these biotic patterns at coarser than finer grains. Studies conducted across multiple grains is thus recommended to improve current understanding of biodiversity patterns and the relationship they exhibit with environmental processes.