3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item Water utilization and population demography in South Africa: key ethical and human rights issues(2010-09-23) Mugabi, BrianAccess to sufficient water is a constitutionally recognized right in the Republic of South Africa as well as being a Universal Human Right. Despite this however, the world wide population numbers are ever growing and water is known to be finite. The Constitution’s Bill of Rights gives South African citizens the right to reproductive choices. South Africa is a water stressed country, with three forces feeding into availability of freshwater, namely; climate change, demographic factors, and policies. Currently, the problem of accessing safe freshwater is under question. This is presents a problem as the Constitution also addresses the right to a healthy environment. Uncontrolled population growth is detrimental to environmental integrity. It is arguable as to whether it is possible to conserve the environment, and at the same time realize human reproductive rights as envisioned in the Constitution. In this research report I reflect on the state of water and environmental resources in view of the right to procreate. I suggest that environmental education could play a major role in finding “the right balance”.Item Impact of charcoal production on populations of selected Savanna tree species on clay soils in Catuane, southern Mozambique(2007-02-21T13:39:28Z) Manjate, Nelson BelecuaneThe impact of charcoal production on populations of selected savanna tree species was investigated on clay soils in Catuane, southern Mozambique. The study focused on answering questions related to the contribution of charcoal production to the local economy, the way populations of selected species were changed by the activity and the way in which they recover. Acacia nigrescens, Acacia nilotica and Ziziphus mucronata were identified as being amongst the most utilised species for charcoal production due to their hard wood quality. The charcoal production is being done by individuals from outside the local community. They are able to generate relatively high revenues from their product, which they sell to external markets, notably Maputo. The local community do not share in the benefits of the production. Interviews with members of the local community, indicated that they would prefer the activity to be stopped or more rigourously controlled. A comparison was made between adjacent harvested and un-harvested areas to assess the effects of charcoal production on the tree populations. Population structure by stem circumference classes were broadly similar in all three study species being characterised by a high frequency in the smallest circumference class. All other classes had considerably lower frequencies. With regards density, Acacia nigrescens and Acacia nilotica showed significantly lower densities in the harvested area. Ziziphus mucronata showed no significant difference. The frequency of stump circumference classes of Acacia nigrescens and Acacia nilotica were normally distributed with the class 81-90 cm being the most common. Ziziphus mucronata data were skewed to the left, with most stumps in the class 52-60 cm. Stump heights were mostly in the region of 20 cm. Circumferences of stumps were similar across the study species, being in the region of 90 cm. Coppicing in stumps was relatively poorly developed, with the majority of stumps having no successful coppice shoots. Kilns had an average density of two kilns per hectare. There was an inverse relationship between species abundance and mean harvesting radius. The results of the study indicate that harvesting has had an effect on species abundance and population structures. With decreases in density and a shift in age distribution towards a predominance of juvenile trees. However, the results are not unequivocal, since the area is not pristine and may have been subjected to other activities before harvesting for charcoal. The charcoal producers appear to harvest all sizes of tree. Their production data, approximately 1300 kg of charcoal produced per hectare, indicate the potential for over utilisation of the woodland resource. Futhermore their practice of cutting at low height subjects the stumps to growth retarding elements such as herbivory and fire, possibly contributing towards relatively unsuccessful coppicing and exacerbating the sustainability issue. To address these issues, along with the socio-economics issues, appropriate structures need to be implemented by government, in consultation with communities.Item A statistical investigation into the properties and dynamics of biological populations experiencing environmental variability(2007-02-15T11:30:22Z) Varughese, Melvin MathewMuch research has been devoted towards the understanding of population behaviour. Such understanding has often been furthered through the development of theoretical population models. This research report explores a variety of population models and their implications. The implications of the various models are explored using both analytical results and simulations. Specific aspects of population behaviour studied include gross fluctuation characteristics and extinction probabilities for a population. This research report starts with an overview of Deterministic Models. This is followed by a study of Birth and Death Processes, Branching Processes and Models that incorporate environmental variability. Finally, we study the maximum likelihood approach to population parameter estimation. The more notable theoretical results derived include: the development of models that incorporate the population’s history; models that incorporate discontinuous environmental changes and the development of a means of parameter estimation for a Stochastic Differential Equation.