Deltaic wetlands are among the most biodiverse systems on earth, provide important ecosystem services, and are natural buffers against violent storms and hurricanes. Marine processes change the planar configuration and internal stratigraphy of deltaic wetlands, and understanding their contribution to wetlands development and deterioration processes is a key issue for society. In this thesis, field data and numerical models are used to investigate the effect of marine processes on the formation and evolution of deltaic wetlands. The first part of this work focuses on the effect of micro and meso tides on the hydrodynamics, morphodynamics, and stratigraphy of deltaic distributaries. Data from instruments deployed in Apalachicola Bay (FL) were used to investigate the hydrodynamics of river mouths. Investigating the hydrodynamics is the first step for a deeper understanding of sediment transport processes, and possible implications for the morphological evolution of these depositional environments. The effect of micro and meso tides on the morphology and stratigraphy of mouth bars is then explored by using numerical and analytical tools. Mouth bars are the building units of river deltas and continuous bifurcations around them allow delta progradation and the formation of new deltaic islands. The second part of this work focuses on the effect of wind waves on salt marsh deterioration using cellular automata and process-based models. Special attention is given to salt marsh resilience to extreme events, to the effect of variable erosional resistance on the large scale morphodynamic response of salt marshes to wind waves, and to the identification of geomorphic features indicative of wetlands deterioration. Results from cellular automata and process-based models are compared to field and literature data.

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Includes bibliography. / Central to a policy for sustainable urbanisation in Namibia, is the recognition of rural-urban relationships. The cross cutting spatial and sectoral issues, of circular migration need to be incorporated in an urbanisation policy. Government policies based on the assumptions of linear development theories such as 'urban bias', which isolate rural from urban as two mutually exclusive areas, mask the fact that poverty is experienced by urban and rural dwellers alike. At the crux of sustainable urbanisation in Namibia, is the ability of urban areas to absorb rapidly urbanising populations by way of provision of adequate urban infrastructure and services, housing and employment opportunities. In tum, this requires appropriate urban local governance, management and planning. The adoption of approaches which embody flexibility, adaptability, cooperation between the urban roleplayers, and speed of response are key to a sustainable urban environment. In the absence of urban conditions which can support a rapidly increasing population, migrants and the urban poor are forced to maintain a foothold in both rural and urban areas as a mechanism of risk diversification and survival. Mere survival, as embodied in circular migration in Namibia, does not suggest a process which can attain economic, social and biophysical sustainability. The implication is that the longer the conditions of circular migration remain entrenched in Namibia, the less likely the attainment of conditions of sustainability, and the more likely the further degradation of the environment, which ironically would probably further necessitate the split of households across the spatial continuum. Policies, such as Namibia's National Resettlement Policy, which target beneficiaries spatially and sectorally, tend not to have the expected benefits of poverty alleviation, and instead, often unintentionally, have the disbenefit of further entrenching poverty and circular migration. Fundamental then, to the sustainability of urbanisation in Namibia, is the integration of rural, urban and environmental policies, in turn requiring multi-sectoral and multi-spatial policies based on a thorough understanding of the forces underpinning circular migration.

Bibliography: leaves 150-154. / As a diamond mining company, Alexkor Ltd has had a great impact on the Namaqualand region. Its non-mining section, ABT, has begun implementing a development strategy that is focused on internal transformation of the company and post-mining economic alternatives. This dissertation focuses on how marginalised communities have been incorporated into the planning, decision-making and implementation of the two Alexkor Ltd diversification projects, tourism and mariculture, in the Northern Namaqualand region. Their participation in these projects is crucial to ensuring that alternative economic options become a vehicle for socio-economic development in a post-mining economy. This is particularly important since the Namaqualand economy is heavily dependent on diamond mining, which has been scientifically predicted to decommission over the next few years. The social disruption caused by the inevitable downscaling of mining is a concern for mining companies and government. It is of greater concern for communities who will suffer the effects of retrenchments and therefore, loss of income, directly. The ABT facilitators of the diversification projects recognise the necessity of applying the development strategy at a regional level. This is to ensure that mine-linked communities, especially those who have been historically marginalised, will be socio-economically empowered by diversification, and that their capacity will have been built in order to participate in post-mining economic options. in addition, the nature of tourism and mariculture requires an IBM approach, which incorporates regional bio-geographical and socio-economic factors. Thus, the implementation of the diversification options has had to incorporate: * the socio-political history of South Africa and the Namaqualand region * relevant legislative and institutional policies and processes that espouse the need for transformation, reconstruction and nation-building at national, provincial and local levels. This study focuses on how the participation of communities has occurred over a period of about eight months. It concludes with recommendations and guidelines which development activists and facilitators could use for similar projects.

Urban areas are usually hotter than their surrounding rural areas, which is the well-known urban heat island (UHI) effect. With continuing urbanization, more people are threatened by the high thermal risks in urban areas, especially during heat waves (HWs). While there has been progress in improving our understanding of the physical processes controlling the urban thermal conditions, key questions remain, especially regarding the relative importance of different physical processes and their spatial variability. To bridge the gap, this dissertation aims to determine the key physical mechanisms that cause surface and near-surface air UHIs, and to quantify the contributions of different physical processes to the daytime warming rate of the urban boundary layer (UBL). In doing so, surface and boundary layer heat budget analyses are conducted using both observations and simulations with the Weather Research and Forecasting (WRF) model. In the first chapter of this dissertation, we quantify the magnitude of surface urban heat islands (SUHIs), or sometimes surface urban cool islands (SUCIs), and elucidate their biophysical and atmospheric drivers based on observational data collected from one urban site and two rural grassland sites in and near the city of Nanjing, China. The study highlights that the magnitude of SUHIs and SUCIs can vary strongly with the biophysical characteristics of the rural land. In the second chapter, we study the WRF-simulated surface and near-surface air UHIs during heat waves in two cities with contrasting climates (Boston and Phoenix). We demonstrate that the magnitude of UHIs or UCIs during HWs is strongly controlled by urban-rural differences in terms of aerodynamic features, moisture availability and heat storage, which show contrasting characteristics in different regions. In the last chapter, we further apply the UBL heat budget analysis to the WRF simulated results and show that in both Boston and Phoenix the surface sensible heat flux dominates the daytime UBL warming rate, whose behavior is the key to understanding how the daytime UBL warming rate changes throughout HWs. In summary, this dissertation improves our understanding of the physical processes modulating the thermal conditions of urban areas from the ground to the top of the boundary layer and provides scientific guidance on model development and mitigation of extreme heat conditions in cities.

Bibliography: leaves 219-230. / Agroforestry (the incorporation of woody perennials into crop production and animal husbandry systems) is placed within the rural development context at the local and national scales, and its potential role in attaining sustainable rural development evaluated. It is suggested as an appropriate response to social economic and ecological problems in the study area (located in KwaBiyela, a northern part of the former 'homeland' of KwaZulu), with potential applications for South Africa in general. A diagnostic survey of 90 households applying a questionnaire of open-ended design, and conducted within the Diagnosis and Design framework of the International Council for Research in Agroforestry, has established that problems exist in all farm production subsystems (cash, savings/investment, food production, energy, shelter, and raw materials) in the study area. The findings include an overwhelmingly positive response towards agroforestry. Recommendations for agroforestry implementation are formulated based on the results of the diagnostic survey, taking into consideration information relating to the functioning of the local society and economy. Importantly, these recommendations consist of agroforestry components which are flexible, can be combined in a number of ways as extensions of current farming practices, and pay particular attention to the utilisation of locally available resource, familiar to the people of the study area, to solve local problems. In this way, the adaptability and survivability of recommended practices is enhanced. In conclusion the requirements for the development of agroforestry in South Africa are discussed in the light of the structural transition currently under way in the country.

The consequences of poor water quality on urban aquatic ecosystems have been well established by researchers worldwide. Stormwater management in the urban areas of South Africa predominately focuses on the collection and diversion of runoff into the nearest receiving water body, with little acknowledgement of the impacts on the environment. The City of Cape Town Metropolitan municipality is an authoritative entity on Cape Town pollution and has acknowledged that polluted stormwater is a significant contributor to the deterioration of its' urban aquatic ecosystems due to the persistence of conventional drainage systems. Small urban wetlands are often overwhelmed by the quality of stormwater and urban runoff. Thus water bodies receiving urban stormwater runoff often have elevated loadings of pollutants. In theory wetlands are capable of treating these pollutants and improving water quality through various ecosystem services, but understanding the performance of wetlands under varying conditions is difficult to determine. In South Africa, there is a paucity of studies focussing on the impacts of urban development on small, urban wetlands and thus their ability to provide ecosystem services. This study aimed to identify the surface water quality of Princess Vlei, a small urban wetland, over the past 8 years, and establish the ingress and outflow of the wetland. The pollutant concentrations within the wetland were best explained by the predictor variables of total rainfall and progression of time. Impacts of total rainfall differed with various parameters resulting in larger volumes of water entering the wetland either diluting pollutant concentrations or elevating pollutant concentrations. These inverse trends were proved through the significant correlations found between total rainfall and COD and total rainfall and EC, while the variable of time influenced the wetland's ability to provide ecosystem services, either through the accumulation, retention or flushing of pollutants. The accumulation of pollutants over time was identified through the increasing concentrations off COD and PO₄³⁻, with the exception of NH₃-N that decreased over time. This implies that the wetland was able to assimilate the NH₃-N but not the COD and PO₄³⁻. The results did not suggest that the wetland was able to treat the water, as the literature emphasises, rather, confirmed the pervasive impacts of the urban catchment on the ability of ecosystem services to treat water quality in the wetland.

Includes bibliographical references. / There are neither historical nor current baseline information relating to the productivity of the OFCA veld and a definite link between the current crisis and the possibly that it is suffering from the effects of having farmed the OFCA veld into a state of durable suboptimal productivity remains to be conclusively established. This current study has been undertaken in order to investigate such a possible link, and to reach a more definite conclusion with regards to the contribution of negative environmental feedback which may have arisen from commercial farming. Specifically, the study investigates the relationship between commercial livestock grazing regimes, possible associated resource degradation (losses in veld productivity and adverse structuring of botanical communities due to livestock grazing effects), and the current productive crisis within the sector.

Bibliography: leaves 23-27.

Includes bibliographical references. / Since the end of white minority rule in southern Africa in the 1990s, transfrontier conservation initiatives have become the dominant conservation strategy in the region and have received international support. This dissertation focuses on the Kavango Zambezi TFCA involving Angola, Botswana, Namibia, Zambia and Zimbabwe. The general objectives of TFCAs - conservation of biodiversity, socio-economic and tourism development and peaceful political cooperation - have been under scrutiny. Literature has paid attention to these TFCAs because of the promises made by supporters of these initiatives on the one hand, and reports and experiences on the ground that suggests that there are political and economic interests in TFCAs, on the other hand. Critical literature has highlighted the effects of TFCAs on local populations. This dissertation addresses two research questions, the first being the rationale for Angola's involvement in the Kavango Zambezi TFCA initiative and the country's modes of participation. Second, it seeks to highlight the place of local communities in this initiative and how it affects these populations.