Doctoral Degrees (Geography and Environmental Studies)

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Browsing Doctoral Degrees (Geography and Environmental Studies) by Subject "Biodiversity conservation"

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    Negotiating grey spaces: A southernised relational analysis of customary land-use regulation mechanisms in peri-urban Informal mixed-use developments - A case study of the Helderberg District in Cape Town
    (Stellenbosch : Stellenbosch University, 2021-12) Geyer, H. S.; Donaldson, Ronnie; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
    ENGLISH ABSTRACT: The study investigates the phenomenon of mixed-use development in informalised public housing (Colloquially referred to as RDP housing) developments in the Helderberg region of the City of Cape Town Metropolitan Municipality in the Western Cape Province of South Africa. This settlement is ironically termed the Location by its residents. There is an irony that these informal mixed-use developments have several attributes of smart growth, such as high densities, affordable housing, accessibility, employment opportunities, etc., in contrast to zoned formal settlements that mostly do not have these characteristics. Informal mixed- use developments occur without the influence of zoning, but is informally regulated through customary land management systems (CLMS). Another irony is that these ‘smartified’ settlements are by no means ideal spaces to live and are generally regarded as unsustainable modes of living due to its informal nature by formal actors. This study investigates these paradoxes in terms of Relational theory and Southern theory, analysing how space is actively produced, organised, and regulated in the everyday life politic of the actor. The study analysed three research problems: Is informal mixed-use development smart, i.e., sustainable? How are these settlements regulated in a CLMS? And how can we plan and zone for these settlements? The study used an ethnomethodological research method to analyse these problems using in-depth interviews. The research results indicate that the mixed-use informalisation of RDPs creates a juxtapositional and contradictory urbanism, a Heterotopia. Informality creates liveable, polymorphic spaces from the marginalised and segregated Location. It develops several smart growth characteristics, not for aesthetic reasons but to make space functional and personal for the subaltern. This creates a new mode of urbanism that gives the actor the freedom to produce their own urban, but it also disconnects the actor from the city as an informal with an uncertainty of rights and standing, it limits the accumulation of wealth, and it creates dangerous and unhealthy living conditions. The Street, a local CLMS self-regulates informal mixed land-uses in the Location. These highly organised, democratic, and transparent organisations record their transactions in ‘black’ books. The Street layers authorities and procedures to create an open and idiosyncratic method of negotiating informal land-use externalities. This system is based on the principles of Ubuntu, which customarily defines propertied relations and incentivises self-regulation of land-uses, enabling the Street committees to provide several voluntary magisterial functions. It provides de facto security for informal land uses, but also complements and reinforces the role of the state in certain limited functions. However, this is also an imperfect system that struggles to regulate non-privatised externalities and accommodate ethnic plurality. The Street committees are also often dysfunctional or corrupt. The combination of informal mixed-uses and CLMS creates a legal grey zone in the Location with alternate zonings, legislations and polycentric authorities and a hybridity of regulations. This peri-urbanisation of the Location unmaps space and protects tenure but does not provide enough legitimacy for novel policing through zoning. This delegitimises zoning but it also creates a new role for planning and zoning, away from traditional socio-technical management by specialists to a more pragmatic and selective enforcement of zoning based on common law and substantial relations tests, in close collaboration with the Streets. Although this is by no means without its challenges, continually operating within a criticality of instabilities and crises, it does, however, strengthen the role of the state as a final and objective authority and benevolent provider of services. The Location thus has the best of both worlds: a formally zoned substructure and a peri-urbanised informal top structure that provides citizenship and agency to the subaltern.
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    Regional mapping of spekboom canopy cover using very high resolution aerial imagery
    (Stellenbosch : Stellenbosch University, 2019-12) Harris, Dugal Jeremy; Van Niekerk, Adriaan; Stellenbosch University. Faculty of Arts and Social Sciences. Dept. of Geography and Environmental Studies.
    ENGLISH ABSTRACT: Widespread degradation of subtropical thicket (South Africa) by poorly managed pastoralism has led to substantial decreases in ecological functioning and biodiversity. Once degraded, thicket does not recover after the removal of livestock, but requires active intervention for restoration. It has been shown that planting spekboom (Portulacaria afra), a dominant and keystone thicket species, increases biomass, improves soil health and creates conditions that support the natural regeneration of biodiversity. Spatial data, especially spekboom canopy cover maps, are required to inform and support large-scale restoration. This research aimed to develop and demonstrate a semi-automated spekboom canopy cover mapping method. A large study area in the Little Karoo in South Africa was selected to encompass the ecological heterogeneity of the wider region. Following a literature review, very high resolution (VHR) multi-spectral aerial imagery was identified as a viable data source for the fine-scale discrimination of spekboom. A set of 2228 aerial images covering the study area was subsequently acquired from Chief Directorate: National Geo-spatial Information (NGI). Techniques for (1) radiometric correction and (2) feature selection were devised to address specific challenges of regional canopy cover mapping. These techniques then formed components of the spekboom canopy cover mapping method. The need for the first technique, called radiometric homogenisation, arose from the presence of problematic radiometric variation in the aerial imagery. Radiometric homogenisation corrects for varying atmospheric and bidirectional reflectance distribution function (BRDF) effects by calibration with concurrent and collocated satellite surface reflectance data. In contrast to other radiometric correction methods, manual placement or acquisition of reflectance targets is not required. Moreover, it is not necessary to have detailed knowledge of atmospheric conditions at the time of capture. An experiment was conducted to establish the efficacy and accuracy of the technique. Homogenised images of the study area were validated by visual inspection and statistical comparison to surface reflectance reference data. Recognisable anomalies such as hot spots and seam lines were removed, and statistical results compared well to competing methods. While the technique was developed in the context of the spekboom canopy cover mapping problem, it could also be applied to general radiometric correction of VHR imagery. Radiometric homogenisation is especially applicable to large study areas where radiometric uncertainty can prevent accurate classification. The second technique, called feature clustering and ranking (FCR), was devised to address problems of sub-optimality and instability that often arise when applying feature selection to redundant data. Unlike other feature selection approaches, FCR allows for the optional inclusion of factors other than relevance (such as computation and measurement cost) in the selection criteria. An experiment was conducted to compare the effects of redundancy on popular feature selection approaches and FCR. Results confirmed that redundancy has a negative impact on commonly used ranking and greedy search (stepwise) feature selection methods. FCR provided the best accuracy and stability performance, confirming its value for selecting stable, informative features from high dimensional data containing redundancy. Finally, the radiometric homogenisation and FCR techniques were incorporated into a method for VHR spekboom canopy cover mapping. Per-pixel spectral, textural and vegetation index features were generated from imagery that had been processed with the radiometric homogenisation technique. FCR was subsequently used to select a reduced set of informative and computationally efficient features. The core of the spekboom mapping method consisted of supervised classification of selected features, followed by morphological post-processing of classifier output maps to remove noise and smooth boundaries. An experiment was carried out to test the accuracy of popular classifiers by comparing canopy cover estimates to ground truth data. A decision tree provided the best performance of the tested classifiers. Canopy cover maps exhibited some variation between different habitats, but provided good accuracy overall, with a mean absolute (canopy cover) error (MAE) of 5.85%. Regional vegetation maps are urgently required to inform responses to global issues, such as climate change. While there is a known operational need for large-area VHR vegetation maps, there are surprisingly few studies that address the cost, computation and classifier transferability challenges associated with large spatial extents. This research contributes to the important field of regional vegetation mapping through the development of the radiometric homogenisation and FCR techniques. In the context of thicket restoration, a viable method for regional mapping of spekboom canopy cover was demonstrated, providing a valuable foundation for future expansion of maps to the rest of the thicket biome. The techniques developed in this study will be useful for the mapping of other thicket vegetation traits, such as biomass.