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North-West University (South Africa) 2004

Effects of land-use on avian demography in the Kalahari area of the North-West Province, South Africa

Hudson, Adrian

Titre : Effects of land-use on avian demography in the Kalahari area of the North-West Province, South Africa

Auteur : Hudson, Adrian

Université de soutenance  : North-West University (South Africa)

Grade : M. Omgewingswetenskappe (2004)

Résumé
Desertification, whether due to anthropogenic pressures, climate change or other factors, has become a global concern. The far-reaching effects of desertification have prompted the formation of the United Nations Convention for the Control of Desertification (UNCCD) and the initiation of the Desert Margins Programme (DMP) in order to attempt to control desertification. This study forms part of the first phase of the DMP and will thus aim to keep to the objectives of the DMP. The principal aims of this study was to determine what effects, if any, landuse types in the desert margins areas of the North-West Province, South Africa, will have on avian demography of the area, and to ascertain whether these changes in avian demography can be used in order to indicate land degradation in these areas. Vegetation structure is widely known to influence avian demography, along with factors such as food availability, nesting sites, water availability and climate. Vegetation structure was also found to be dramatically altered by the effects of land-use in the study area. The hypotheses formulated for this study were that : 1) Bird populations are noticeably influenced by the vegetation structure of the area they inhabit ; 2) bird species diversity as well as bird numbers decline with an increase in land degradation in the study area ; and 3) Bird species diversity will act as a good surrogate for land degradation in the study area. In order to test these hypotheses, the study area was selected in the Molopo district of the North-West Province. This district falls within the desert margin area and is earmarked as one of the target areas for the Desert Margins Programme in South Africa. Within the study area four sites were chosen to represent different degrees of degradation. Vegetation structure analyses were carried out at each of the sites in order to determine the degree of change in vegetation structure brought about by land use in the area. The birds at each of these sites were surveyed using three transects. Surveys were repeated over four seasons to give some indication of the effects of seasonality on bird populations of the different sites. The results showed a definite decline in bird species diversity with an increase in land degradation, especially due to the simplification of the vegetation structure because of anthropogenically induced alteration of the vegetation structure of the area. Both bird species diversity and the number of birds occurring at the sites declined with an increase in land degradation.

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