More water, less grass? An assessment of resource degradation and stakeholders' perceptions of environmental change in Ombuga grassland, northern Namibia

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The three overall objectives of this thesis are to assess 1) to what degree have soil and vegetation resources deteriorated, if at all, 2) how do perceptions of environmental change held by local stakeholders correspond to scientific assessments of present and past environmental conditions in the Ombuga grassland and surrounding mopane savanna an important grazing area in central northern Namibia, and 3) how do these relate to national level assessments? Analysis of the process of developing national level indicators for monitoring of land degradation in Namibia concluded that specific indicators should be developed on national level, and in some instances even on regional and local level, instead of the often proposed development of a global set of indicators to be used everywhere. Reasons for this are: 1) there are no universal causes and effects of land  degradation. 2) the participatory approach, involving stakeholders on both local and national levels gave them ownership of the process and the resulting indicators, and led to an increased understanding of the concepts of environmental monitoring. 3) the participatory process of developing national indicators taken in Namibia created a common platform for representatives from various sectors, leading to increased interaction among sectors, an important aspect in most developing countries, where sectoral approaches predominate. Assessment of local perceptions of environmental change in and around Ombuga grassland showed that farmers there claimed that overgrazing and low rainfall since the beginning of the 1990s cause negative environmental changes in the area, confirming findings from national monitoring. However, results from interviews give a more complex picture of causes and effects of environmental change, suggesting that 1) decreasing availability of grazing outside the study area, 2) improved access to the area, 3) provision of permanent water supply, and 4) fencing of large areas of the commons, are major factors contributing to environmental changes in the area. The results suggest that introduction of permanent water supply was the single most important factor, allowing more people and livestock into the area. Results suggest that assessments of local knowledge in a relatively small area can provide valuable contributions to development and assessment of national monitoring initiatives. Investigation of the influence of permanent water points on grazing resources in Ombuga grassland and surrounding mopane savanna showed that significant grazing induced changes, manifested by palatable perennial grasses being replaced by less palatable annual grasses, were identified around water points along a water pipeline as far as 6 km from water points. However, no significant grazing induced changes in grass composition were observed around privately owned hand dug wells. Private ownership leading to stronger control of access to traditional wells compared to open access water points along the pipeline seems to be a key factor preventing over-utilization of grazing resources around the former. Assessment of the usefulness of satellite remote sensing in detecting observed environmental changes in and around Ombuga grassland shows that the Landsat TM sensor is capable of identifying bare ground, saltpans and grassland with a fair accuracy. However, there are apparent difficulties in separating woodland from shrubland, and also shrubland from grassland, using supervised classification. The results suggest that the use of the soil adjusted vegetation index (SAVI) provides valuable information about variations of green biomass over time in semi-arid environments. However, because of the strong influence of underlying soil related to the relatively sparse ground cover in semi-arid environments, it is suggested that any investigation based on satellite remote sensing in dry environments be supported by a thorough ground based assessment, taking into account the high spatial and temporal variability of rainfall in these environments. Keywords: Environmental monitoring, semi-arid, pastoralism, rural water supply, indicators, local knowledge, vegetation survey, satellite remote sensing.

Stockholm University
PhD Thesis
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