Browsing Research articles (ORI) by Issue Date
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Neuenschwander, A.L.; Crawford, M.M.; Ringrose, S. (Taylor & Francis; http://www.tandf.co.uk/journals/titles/01431161.asp, October NaN, 2005)[more][less]
Abstract: The Earth Observing-1 (EO-1) satellite acquired a sequence of data in 2001 and 2002 that highlighted the annual flooding of the lower Okavango Delta. The data were collected as part of the calibration/validation programme for the Advanced Land Imager (ALI) sensor on the NASA EO-1 satellite. The primary purpose of this study was to compare the capability of ALI to that of Landsat ETM+ for large-scale mapping applications in the Okavango Delta. While the extent and inaccessibility of many areas of the Delta make application of remote sensing attractive, the availability of data with adequate spatial and spectral resolution has limited the characterization of the complex patterns of land cover and geomorphology in the Delta. Initial analysis of the ALI data via supervised classification clearly showed macro-flood features, delineation of downstream channel flow areas, and lateral-downstream inundation of the floodplain. These patterns and the proportions of flooding of the channel compared to that of the floodplain (impoundment) varied annually, from the wetter seasonal swamps through the drier seasonal and occasional swamps. Consistently higher classification accuracies achieved using ALI data relative to ETM+ data are attributed to the higher signal-to-noise ratio and the increased dynamic range of the ALI data. URI: http://hdl.handle.net/10311/169 Files in this item: 2
license.txt (1.998Kb)neuenschwander_ringrose_ijrs_2005.pdf (2.296Mb) -
Ringrose, S.; Jellema, A.; Huntsman-Mapila, P.; Baker, L.; Brubaker, K. (Taylor & Francis; http://www.tandf.co.uk/journals/titles/01431161.asp, October 10, 2005)[more][less]
Abstract: This work determines the value of remotely sensed imagery in developing drying impacts which occur as a result of internal and/or external factors in the Okavango catchment. Three sites provide a preview of the consequences of Delta margin drying as depicted over historical, intermediate and geological timescales. Initially, supervised classification resulted in the identification of sequences of islands and flood plains and their associated vegetation cover on ETM+ imagery, with a classification accuracy of 74- 77%. Comparative results, augmented by patch analysis, suggest that through time, island woody vegetation cover has invaded the flood plains and locally developed protected ecotonal areas (extensions) which are densely treed, relative to adjacent, non-protected flood plains. Over longer time periods, protected areas between extensions became infilled with woody vegetation leading to, in effect, island enlargement or agglomeration. Disadvantages of long-term Delta drying in terms of natural resource management include a reduced availability of wetland-based construction and agricultural resources. If natural regeneration (island agglomeration) is allowed to take place, these resources may ultimately be replaced by dryland timber and potential cropland. URI: http://hdl.handle.net/10311/174 Files in this item: 2
license.txt (1.998Kb)ringrose_int_j_remote_sensing_2005.pdf (3.625Mb) -
Daka, P.S.; Obuseng, V.C.; Torto, N.; Huntsman-Mapila, P. (South African Water Research Commission http://www.wrc.org.za, NaN, 2006)[more][less]
Abstract: Deltamethrin concentrations were determined in 35 sediment samples collected from three different habitats: channel, lagoon and pool sites from Xakanaxa in the Okavango Delta, NW Botswana. The samples were Soxhlet-extracted in acetone to extract deltamethrin residues and subsequently cleaned-up with silica gel 60. The final determination was carried out with a gas chromatograph equipped with an electron capture detector (GC-ECD). The sample work-up and determination gave deltamethrin recoveries of 54 to 97%, and detection limits of 0.004 mg/kg dw. The concentration of deltamethrin residues in the sediment samples collected from the three sprayed areas in the Okavango delta ranged between 0.013 and 0.291 mg/kg dw, with the highest concentrations observed in samples obtained from the pool sites. Analysis of samples for organic matter content showed percentage total organic carbon (% TOC) ranging between 0.19% and 8.21%, with samples collected from the pool having the highest total organic carbon. The concentrations of deltamethrin residues and the % TOC in sediment samples showed a similar trend with the highest levels recorded in the pool samples. These data confirmed that a simple method based on GC-ECD, after Soxhlet extraction, was robust enough to enable quantification of deltamethrin in the sediments, because comparable results were obtained with a more sophisticated system consisting of a GC coupled to a mass spectrometer with a time of flight (TOF) analyser. URI: http://hdl.handle.net/10311/650 Files in this item: 1
Daka_WSA_2006.pdf (1.231Mb) -
Characterization of arsenic occurrence in the water and sediments of the Okavango Delta, NW BotswanaHuntsman-Mapila, P.; Mapila, T.; Letshwenyo, M.; Wolski, P.; Hemond, C. (Elsevier Science B.V. Amsterdam; http://www.elsevier.com/wps/find/journaldescription.cws_home/768/description#description, NaN, 2006)[more][less]
Abstract: Detailed chemical analyses were performed on surface water, groundwater and sediment samples collected from the Okavango Delta between February and November 2003 in order to examine the distribution and geochemistry of naturally occurring As in the area. Surface water in the Okavango Delta, which is neutral to slightly acidic and has high dissolved organic C (DOC), was found to be slightly enriched in As when compared to a global value for stream water. Of the 20 new borehole analyses from this project, six were found to have values exceeding 10 ug/L. the current World Health Organization provisional guideline value for As. The results from field speciation indicate that As(III) is slightly more predominant than As(V). There is a positive correlation between As and pH and between As and DOC in the groundwater samples. For the sediment samples, there is a positive correlation between As and Co. As and Fe. As and loss on ignition (LOI) and between As and the percent fines in the sample. Reductive dissolution of oxides and hydroxides in the sediments with organic C as an electron acceptor is the likely mechanism for the release of As from the sediments into the groundwater. URI: http://hdl.handle.net/10311/135 Files in this item: 2
huntsman-mapila_app_geochem.pdf (3.170Mb)license.txt (1.998Kb) -
Kgathi, D.L.; Kniveton, D.; Ringrose, S.; Turton, A.R.; Vanderpost, C.; Lundqvist, J.; Seely, M. (Elsevier; www.elsevier.com/locate/jhydrol, NaN, 2006)[more][less]
Abstract: The Okavango basin comprises the Cuito and Cubango active catchment areas in Angola, in addition to the Kavango's Okavango non-active catchment in northern Namibia and Botswana. The Okavango River water and its ecosystem resources are critically important sources of livelihoods for people in the basin. Pressures from livelihoods and development are already impacting on the environment. These pressures may increase in the future due to the rapid increase in population, the peace process and associated resettlement activities in Angola, and major development initiatives in Botswana and Namibia. For instance, possible future increase in water abstraction from the Okavango River may affect the long-term environmental sustainability of the Okavango Delta by minimizing channel shifting and thereby reducing spatial biodiversity. The paper argues that while conservation of the natural environment is critical, the pressing development needs must be recognized. The reduction of poverty within the basin should be addressed in order to alleviate adverse effects on the environment. The paper recommends that the development of sustainable tourism and community-based natural resource management initiatives may be appropriate strategies for reaching the Millennium Development Goals of poverty alleviation and achievement of environmental sustainability in the Okavango Basin. These initiatives have a comparative advantage in this area as demonstrated by the performance of the existing projects. URI: http://hdl.handle.net/10311/154 Files in this item: 2
kgathi_j_hydrology_2006.pdf (6.004Mb)license.txt (1.998Kb) -
Ngwenya, B.N.; Kgathi, D.L. (Elsevier Ltd; www.elsevier.com/locate/pce, NaN, 2006)[more][less]
Abstract: This case study investigates access to potable water in HIV/AIDS related home-based care households in five rural communities in Ngamiland, Botswana. Primary data collected from five villages, consisted of two parts. The first survey collected household data on demographic and rural livelihood features and impacts of HIV/AIDS. A total of 129 households were selected using a two-stage stratified random sampling method. In the second survey, a total of 39 family primary and community care givers of continuously ill, bed-ridden or non-bed-ridden HIV/AIDS patients were interviewed. A detailed questionnaire, with closed and open-ended questions, was used to collect household data. In addition to using the questionnaire, data was also collected through participant observation, informal interviews and secondary sources. The study revealed that there are several sources of water for communities in Ngamiland such as off-plot, outdoor (communal) and on-plot outdoor and/or indoor (private) water connections, as well as other sources such as bowsed water, well-points, boreholes and open perennial/ephemeral water from river channels and pans. There was a serious problem unreliable water supply caused by, among other things, the breakdown of diesel-powered water pumps, high frequency of HIV/AIDS related absenteeism, and the failure of timely delivery of diesel fuel. Some villages experienced chronic supply disruptions while others experienced seasonal or occasional water shortages. Strategies for coping with unreliability of water supply included economizing on water, reserve storage, buying water, and collection from river/dug wells or other alternative sources such as rain harvesting tanks in government institutions. The unreliability of water supply resulted in an increase in the use of water of poor quality and other practices of poor hygiene as well as a high opportunity cost of water collection. In such instances, bathing of patients was cut from twice daily to once or not at all. Depending on the severity of HIV/AIDS related symptoms, e.g. diarrhoea, 20-80 additional litres of water could be required daily. The case study demonstrates that, at individual level, access to water is an integral element of the patient's holistic healing process and psychosocial well being. At household and community levels, access to sufficient supplies of potable water when and where it is needed is central to mitigation of HIV/AIDS impacts. Access to water should therefore not be treated strictly as an economic good due to its importance as a basic human need, a social good and indeed a human right. URI: http://hdl.handle.net/10311/172 Files in this item: 2
license.txt (1.998Kb)ngwenya_kgathi_PCE_06.pdf (4.416Mb) -
Mazvimavi, D.; Mmopelwa, G. (Elsevier, www.elsevier.com/locate/pce, NaN, 2006)[more][less]
Abstract: Lack of access to safe or improved water supply in developing countries is a major global concern, since water is a basic need for sustenance. Programmes aimed at improving access to safe water have been implemented in several sub-Saharan countries. In Botswana, only gazetted settlements have access to water and other basic services provided by the government. This paper examined the level of access to safe water, effort required, and problems encountered in collecting water by households in ungazetted settlements. The paper also investigated whether households in these settlements were willing to pay for improving access to water. The study has been undertaken on settlements located along the Boteti River in the North West District of Botswana. The majority of households in ungazetted settlements satisfy their domestic water requirements through abstracting untreated water from river flows and hand-dug wells when the river is not flowing. Men dominate in collecting water in ungazetted settlements, with the most dominant mode of transporting water being the use of donkey carts. The dominance of men in water collection and use of donkey carts is due to water sources being too distant from homesteads. This has resulted in low water consumption levels, with the per capita water consumption being less than 20 l/capita/ day for most households. Such low levels of water consumption adversely affect attainment of desirable personal hygiene and food preparation. The opportunity cost of time for water collection has been estimated at 1.80 Botswana Pula (P) and the price of water is estimated to be P18/m3 (1.00 P = 0.1755 USD on 18 November 2005). This is higher than the price paid by households residing in rural settlements obtaining water from government or district council water supply schemes. The majority of the households were willing to make a once-off contribution towards improving access to potable water with the mean willingness to pay (WTP) being P161 per household, or just over a third of the statutory agricultural minimum wage in Botswana, P589/month. The potential contribution by household to an improved water supply is significant for a largely unemployed rural population. URI: http://hdl.handle.net/10311/502 Files in this item: 1
Mazvimavi2006WaterAccess.pdf (1.377Mb) -
Dallas, H.F.; Mosepele, B. (African Journal of Aquatic Science http://www.nisc.co.za/journals?id=2, NaN, 2006)[more][less]
Abstract: The spatial distribution of aquatic macroinvertebrates in the Okavango River Delta, Botswana, was investigated during the low-water period in February 2003. This complements an earlier study undertaken during high-water in June 2000. Seventy-five samples were taken in a range of aquatic habitats at 29 georeference points in four focal areas: Upper Panhandle (UPH), Lower Panhandle and Guma Lagoon (LPH), Moremi Game Reserve/Xakanaka (MGR), and Chief’s Island (CI). Over 180 morphospecies (approximately 63 families) were recorded during the survey. Multivariate analyses of macroinvertebrate assemblages indicated that assemblages in each of the four focal areas were at least 54% similar at morphospecies level, and 71% similar at family level, although some taxa were more or less common in different areas. Differences in macroinvertebrate assemblages were observed amongst different habitat types, with differences most pronounced between the deltaic habitats and isolated seasonally-flooded pools and temporary rain-filled pools in MGR and CI. The highest number of taxa was recorded in the MGR (125), followed by the UPH (96), CI (93) and the LPH (89) areas. The most families were recorded in the Hemiptera (11), followed by Mollusca (10), Diptera (nine), Coleoptera (nine), Crustacea (six), Ephemeroptera (six) and Odonata (four). Three families of Hirudinea and Trichoptera, and one family of Lepidoptera, were also recorded. Hydracarina were common but not identified beyond order, while Oligochaeta were less frequently recorded. With respect to the different aquatic habitats sampled, the highest number of taxa was recorded in marginal vegetation in the channels and lagoons, although inundated floodplains, floating vegetation and marginal vegetation in backwaters also supported many taxa. The fewest taxa were recorded in sediment. This survey, whilst representing a ‘snapshot’ of the system under low-water conditions, highlights the importance of maintaining a mosaic of aquatic habitats in the Delta. Further studies would enhance our knowledge of the aquatic macroinvertebrate biodiversity of the Okavango Delta, thereby contributing to its conservation. URI: http://hdl.handle.net/10311/869 Files in this item: 1
Dallas_AJAS_2007.pdf (1.160Mb) -
Heinl, M.; Neuenschwander, A.; Sliva, J.; Vanderpost, C. (Springer: http://www.springerlink.com, NaN, 2006)[more][less]
Abstract: A series of 98 satellite images was analysed to reconstruct the fire and flood history of a floodplain system in southern Africa(Okavango Delta, Botswana). The data was used to investigate interactions between fire and flooding, and to determine the relevance of rainfall and flood-events for fire occurrences on floodplains and on drylands. The aims of the study are (1) to analyse and compare the fire frequency on floodplains and on adjacent drylands, (2) to investigate the influence of rainfall and flooding on the fire occurrence and (3) to determine correlations between fire frequency and flood frequency. The analyses show higher fire frequencies on floodplains than on drylands because of higher biomass production and fuel loads. The fire occurrence on drylands shows a correlation with annual rainfall events, while the fire frequency on floodplains is in principle determined by the flood frequency. Between floodplain types, clear differences in the susceptibility to fire where shown by analysing flood frequency vs. fire frequency. Here, the highest potential to burn was found for floodplains that get flooded about every second year. By calculating mean fire return intervals, the potential to burn could be specified for the different floodplain types. URI: http://hdl.handle.net/10311/792 Files in this item: 1
Heinl_Michael_LE_2006.pdf (1.827Mb) -
Vanderpost, C. (Population Environment; Springer Netherlands; http://www.springerlink.com/content/0t141ml76q32717m/, January NaN, 2006)[more][less]
Abstract: Intensification of human sprawl in buffer zones of globally important African wilderness areas is of worldwide concern. The paper identifies two major conflicting (yet potentially reconcilable) pathways of rural sprawl in African wilderness buffer regions, described as the subsistence pathway and the wildlife-tourism pathway. Containment of rural sprawl near important ecological reserves requires addressing both pathways and their underlying conflicts. Reconciliation of subsistence sprawl with wildlife-conservation based tourism may occur through adequate compensation for community subsistence resource losses by the creation of sufficient alternatives to local communities that may reduce the need to rely on subsistence resources. URI: http://hdl.handle.net/10311/59 Files in this item: 2
cvanderpostpathwaysprefinalversion.pdf (725.4Kb)license.txt (1.998Kb) -
Heinl, M.; Frost, P.; Vanderpost, C.; Sliva, J. (Elsevier; http://www.elsevier.com/wps/find/journaldescription.cws_home/622855/description#description, May 8, 2006)[more][less]
Abstract: Satellite imagery derived fire history data for the southern Okavango Delta, Botswana from 1989 to 2003 were used to analyse the temporal and spatial distribution of fires and to assess changes in fire activity. Maximum fire activity was encountered for 1997 with 24.1% of the study area burned. The annual extent of the burned area fluctuated considerably, but there appeared to be a regular oscillation apparently induced by floodplain fires. The main fire activity on drylands is in September at the end of the dry season, while most floodplains burn earlier in the year. Both burning of floodplains and drylands appear to peak prior to floods and rainfall-events, respectively. Areas with highest fire frequency were outlined and spatial analyses showed that fires on the drylands are largely due to burning of adjacent floodplains. The floodplains were therefore identified as the centres of fire activity, being the regions with the highest fire frequency and serving as source of fires spreading into drylands. Floodplains showed higher fire frequencies compared to drylands, but no increase in fire activity was detected over the study period for both floodplains and drylands. Description: The study was part of the project 'Fire regime and vegetation response in the Okavango Delta, Botswana' funded by the Volkswagen Foundation, Germany and carried out by the Chair of Vegetation Ecology, Technische Universitaet Muenchen, Germany in collaboration with the Harry Oppenheimer Okavango Research Center (HOORC, University of Botswana) and University of Pretoria, South Africa. Financial support was also given by Conservation International Botswana and the German Academic Exchange Service (DAAD). URI: http://hdl.handle.net/10311/151 Files in this item: 2
heinl_j_arid_env.pdf (392.9Kb)license.txt (1.998Kb) -
Mbaiwa, J.E.; Mbaiwa, O.I. (International Journal of Wilderness; http://ijw.wilderness.net/, December NaN, 2006)[more][less]
Abstract: This article examines the effects of veterinary fences on wildlife populations in the Okavango Delta, Botswana. Using data from secondary data sources, findings indicate that the existence of veterinary fences in the Okavango Delta contributes to the decline of wildlife species in Botswana. Veterinary fences are erected to control the spread of livestock diseases in order to protect the European Union beef market where Botswanaâ s beef is largely exported. Migratory wildlife species such as wildebeests, zebras, giraffes, buffalo, and tsessebes have their migratory routes blocked by veterinary fences and hence die from dehydration and entanglements in the fence. Those that get trapped by the fence often become easy kill targets for poachers. Some of the animals have been observed walking along the fence trying to cross. The erection of veterinary fences indicates that the expansion of livestock production into wildlife areas threaten the survival of wildlife in Botswana. To address the problem, an integration of wildlife production with other sectors such as agricultural development should be made a priority at national and local policy levels. This means that the principles of sustainability should be given priority in the erection of veterinary fences in wildlife areas. URI: http://hdl.handle.net/10311/28 Files in this item: 2
license.txt (1.998Kb)mbaiwa_int_j_wilderness_2006.pdf (338.1Kb) -
Mladenov, N.; McKnight, D.M.; Wolski, P.; Murray-Hudson, M. (Elsevier, www.elsevier.com/locate/ecolmodel, NaN, 2007)[more][less]
Abstract: In order to examine dissolved organic matter (DOM) fluxes in seasonal wetland systems that expand and contract seasonally, a time-variable model of dissolved organic carbon (DOC) was developed for a seasonal floodplain in the Okavango Delta of Botswana. The model simulates DOC concentrations from March 2001 to November 2002, during which time DOC concentrations varied between 8 and 31mgCL−1. The model uses a continuously stirred tank reactor (CSTR) approach to describe the hydrologic and biogeochemical controls on DOC leached from litter within the floodplain and transported into the floodplain from upstream. In 2002, a fire burned the floodplain and less litter was available for leaching than in 2001. The model was driven by observations of discharge, water temperature, upstream DOC concentrations, and DOC leaching rates from leaching experiments. Leaching experiments with sedges and grasses indicated that on average 23mgDOCg−1 were leached during the first day ofwetting and 0.6mgDOCg−1 d−1 were continuously leached afterwards. Leaching experiments also showed a decreased amount of DOC released from burned litter and soils than from unburned litter and soils. A two-pool first-order decaymodel that represents both rapidly (0.14 d−1 (at 22 ◦C)) and slowly (0.045 d−1) decaying pools of DOC provided the best representation of observed patterns in DOC concentration in 2001. The decay rate of the first pool decreased by nearly half in 2002, when an estimated 78% of litter was removed by fire. Upstream DOC transport into the floodplain was the dominant source of DOC (representing approximately 70% and 75% of the DOC input in 2001 and 2002, respectively), followed by DOC leaching from litter and DOC originating from microbial sources. In 2001, decomposition (representing approximately 36% of the DOC loss), outflow to an adjacent floodplain (36%) and infiltration (28%) were the major removal mechanisms for DOM from the study floodplain. The large amount of DOC transported by infiltration implies storage of DOC in the subsurface, whichmay influence subsurface heterotrophic activity. In light of future climate change anticipated for the region, a scenario using a 2 ◦C increase in average water temperature and 10% reduction in upstream DOC mass was performed and resulted in significant (11%) reduction in annual DOC mass within the study floodplain. URI: http://hdl.handle.net/10311/497 Files in this item: 1
Mladenov2007Simulation.pdf (2.048Mb) -
Swatuk, L.A.; Kgomotso, P.K. (Elsevier, www.elsevier.com/locate/pce, NaN, 2007)[more][less]
Abstract: Supplying adequate water and sanitation facilities to small, scattered rural communities and/or large, fast growing settlements in remote areas is a challenge not easily met anywhere in the world. This article focuses on just such a challenge in the remote, rural area of Ngamiland District in north-western Botswana. Drawing on a combination of critical analysis of government and secondary data, participant observation, and key stakeholder interviews conducted over the period 2004–2006, the article shows that despite a good aggregate record of supplying water and sanitation throughout the country, there are abiding, often serious, problems with supply in remote areas. The research reveals that due to a combination of limited human and financial resource capacity, government policy that deliberately under-serves remote areas in order to encourage resettlement, and complacence among key decision-takers, supply problems go unresolved. The article suggests four key interventions as possible ways forward: using the Okavango Delta Management Plan (ODMP) process as a guiding framework for institutional reform; linking research directly to human resource capacity development; treating water as both a social and an economic good; and soliciting an IWRM ‘champion’ to drive the political process. URI: http://hdl.handle.net/10311/501 Files in this item: 1
Swatuk2007WATERSUPPLY.pdf (1.584Mb) -
Mubyana-John, T.; Wutor, V.C.; Yeboah, S.O.; Ringrose, S. (Academic Journals. http://www.academicjournals.org/SRE, NaN, 2007)[more][less]
Abstract: The influence of wild fires on microbial community structure, soil organic matter, sulphur oxidising and nitrifying microbial populations in the floodplains of the Okavango Delta of Botswana was assessed. Microbial community structure was assessed by phospholipids ester-linked fatty acids (PLFA) quantification while microbial sulphur oxidisers were assessed by Most Probable Number (MPN). Community structure assessment showed that burning shifted the microbial community structure from single cellular bacteria being the dominant groups to filamentous fungi and actinomycetes being the most dominant groups. Generally burning increased the fungal component (18:2 w6) matrix from 3.40 to 8.35 while the actinomycetes and sulphur reducing bacterial (10 Me 16:0) component also increased from 1.02 to 1.70 mostly in the floodplains. Generally, the organic matter content declined with burning. However, the influence of burning on soil pH was non conclusive. Soil microbial biomass carbon increased slightly after the fire. The number of heterotrophic and nitrite-oxidizing and sulphur reducing bacteria increased. Overall, these results indicate that burning significantly alters the microbial community structure as large above ground losses of nutrients during and after burning often results in low quantities of nutrients released into the soil. URI: http://hdl.handle.net/10311/349 Files in this item: 1
Fire and.pdf (2.461Mb) -
VanderPost, C.; McFarlane, M. (Elsevier www.elsevier.com/locate/jag, NaN, 2007)[more][less]
Abstract: Locating additional long-term groundwater resources in semi-arid regions of developing countries with growing populations is an expensive undertaking. Simple geographic information system (GIS) techniques can be utilised to facilitate efficient application of expensive geophysical techniques and test-drilling by functioning as an interdisciplinary integration and decision-making tool, especially in data-poor and poorly mapped environments where more sophisticated GIS techniques are not applicable. The paper demonstrates this in the context of the search for groundwater alternatives to the dwindling river water supply in the Boteti area of the Kalahari region in Botswana. URI: http://hdl.handle.net/10311/573 Files in this item: 1
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Bonyongo, M.C.; Harris, S. (Willey Blackwell Publishing http://eu.wiley.com/WileyCDA/Brand/id-35.html, NaN, 2007)[more][less]
Abstract: We used body weight ratio to determine the degree of species-packing of the Okavango Delta (22,000 km2) grazers and compared it to that of four conservation areas of similar sizes but varying in the diversity of habitat types. They are Etosha National Park (23,175 km2) in Namibia, Hwange National Park (14,621 km2) in Zimbabwe, Kafue National Park (24,000 km2) in Zambia and Kruger National Park (19,633 km2) in South Africa. We considered possible ecological explanations for existing gaps within the assemblage. The weight ratio (measure of the degree of species-packing) of the grazers of the Okavango Delta was 1.25, with a total of 27 species which was far less than the theoretically expected 2.0. One-way analysis of covariance (ANCOVA) showed that there were significant differences in the degree of species-packing between the Okavango Delta and other conservation areas of similar size in southern Africa (F1,5 ¼ 166, P < 0.001). Regressing habitat heterogeneity (expressed as number of different habitat types) on species-packing of the five conservation areas yielded a positive linear relationship with R2 ¼ 0.76 implying that 76% of the variation in the degree of speciespacking in the five conservation areas is explained by variation in habitat heterogeneity. We conclude that size ratios are useful descriptors of animal communities and it is a useful measure of species diversity, which can be used for monitoring purposes. Imbalances in weight ratios provide a measure of identifying perturbations due to species loss or arrival of new species within a natural ecosystem. URI: http://hdl.handle.net/10311/608 Files in this item: 1
Bonyongo_AJE_2007.pdf (1.153Mb) -
Ngwenya, B.N.; Mosepele, K. (Elsevier www.elsevier.com/locate/pce, NaN, 2007)[more][less]
Abstract: Generally, rural households pursue all year round natural and non-natural resource-based livelihood systems to diversify these options in order to cope with risks emanating from a range of shocks and stressors. Artisanal fishing in the Delta is not only a major livelihood option but also a source of food security. This paper is based on analysis of primary data collected from a survey of 248 subsistence fishers’ households through simple random sampling in 22 villages in the Delta. The overall objectives of the survey were to assess the general prevalence of HIV/AIDS in the Ngamiland district of Botswana, to investigate potential effects of AIDS-related stressors, particularly chronic illness on artisanal fishing activities, and to assess implications towards food security. Results from this study indicate that HIV prevalence rates for pregnant women attending antenatal clinics in the Delta are approximately 30% and are related to factors such as marriage, education, and employment. Despite this relatively high prevalence percentage, most of the affected households do not have adequate access to HIV/AIDS support facilities. Support services are provided on the basis of population size and/or status of the settlement (i.e. urban, urban village, rural or remote). Therefore, since about 50% of the Delta’s population lives in settlements of less than 500 people, they receive health services indirectly through major population centres whose capacity to deliver timely HIV/AIDS services is limited. This disproportionate access to HIV/AIDS services disadvantages the majority of fishing communities in the Delta, and may affect their ability to fish. Moreover, about 53% of sampled households had cared for a continuously ill person/s (CIP’s) in the last 5 years, out of which approximately 29% felt that this seriously impacted fishing activities. These serious impacts included sale of family assets, depletion of savings, and switching or abandoning fishing activities. Subsequently, household food security is seriously affected because fish provides a significant proportion of food to CIP households where approximately 55% of households get their food from fish products. During food shortages, CIP households resorted to a hierarchy of strategies which included cutting down on meals or reducing meal portions, looking for paid work, gathering wild fruit, asking for food from relatives, selling livestock, and getting social assistance. In conclusion, artisanal fishing is a natural safety net which constitutes an important buffer for households affected by HIV/ AIDS-related stressors in the Okavango Delta. Access to fish helps these households mitigate potentially adverse impacts such as deterioration into chronic poverty. URI: http://hdl.handle.net/10311/572 Files in this item: 1
NGWENYA2007Okavango.pdf (1.602Mb) -
Ringrose, S.; Vanderpost, C.; Matheson, W.; Wolski, P.; Huntsman-Mapila, P.; Murray-Hudson, M.; Jellema, A. (Elsevier Ltd; www.elsevier.com/locate/jaridenv, January NaN, 2007)[more][less]
Abstract: This work seeks to determine whether riparian woody plant variables respond to drying and salinity regimes in the semi-arid distal Okavango Delta, northern Botswana. Structural and compositional variables were obtained from 47 field sites. Mapping using satellite imagery illustrated differences in the character of riparian zones in terms of species composition and provided data on flood frequency. Salinity data plots show increases downstream. Results imply that woody plant variables respond to desiccation-driven change due to water-table lowering (reduced recharge) and increased salinization through distinct changes in tree and shrub height, plant density and species richness. In the wetter, intermediate distributaries, key biotic indicators of ecosystem change comprise structural variables such as decreases in canopy cover per cent and tree height and increases of shrub height, which are indicative of mainly ground-water declines. Biotic indicators in the less frequently flooded receiver channels comprise plant density and species richness increases involving mainly brackish ground-water-tolerant and dryland species which are indicative of both ground-water declines and/or salinization. These indicators could provide useful parameters for use in long- and short-term monitoring aimed at assessing desiccation-driven change in different parts of the Okavango Delta and possibly other semi-arid wetlands. The indicators are important as a less-expensive alternative to drilling as a means of verifying ground-water declines and/or salinization. URI: http://hdl.handle.net/10311/161 Files in this item: 2
license.txt (1.998Kb)Ringrose_et_al_JAE_07.pdf (1.322Mb) -
Huntsman-Mapila, P.; Ringrose, S.; Downey, W.S.; Modisi, M.; Coetzee, S.H.; Tiercelin, J-J.; Kampunzu, A.B.; Vanderpost, C. (Elsevier; http://www.elsevier.com/wps/find/journaldescription.cws_home/865/description#description, February 7, 2007)[more][less]
Abstract: [Please note chemical formulae do not display correctly in this abstract]. Sediment samples from a continuous 4.6m profile in the dry bed of Lake Ngami in NW Botswana were analysed for geochemistry and dated using both 14C and TL methods. Certain units in the profile were found to be diatom rich and these, with the geochemical results, were used as indicators of high and low lake levels within the basin. The Lake Ngami sediments contain a high proportion of SiO2 (51-92.5 wt%, avg. 72.4 wt%) and variable levels of Al2O3 (2.04-17.2 wt%, avg. 8.88 wt%). Based on elevated Al2O3 and organic matter (LOIorgc) results, lacustrine conditions occurred at ca. 42 ka until 40 ka and diatom results suggest that relatively deep but brackish conditions prevailed. At 40 ka, the lacustrine sedimentary record was terminated abruptly, possibly by tectonic activity. At ca. 19 ka, shallow, aerobic, turbulent conditions were prevalent, but lake levels were at this time increasing to deeper water conditions up until ca. 17 ka. This period coincides with the Late Glacial Maximum, a period of increased aridity in the central southern Africa region. Generally, increasing Sr/Ca ratios and decreasing LOIorgc and Al2O3, from ca. 16 to 5 ka, suggest decreasing inflow into the basin and declining lake levels. Based on the enrichment of LREE results, slightly alkaline conditions prevailed at ca. 12 ka. Diatom results also support shallow alkaline conditions around this time. These lake conditions were maintained primarily by local rainfall input as the region experienced a warmer, wetter phase between 16 and 11 ka. Lake levels rose rapidly by 4 ka, probably in response to enhanced rainfall in the Angolan catchment. These results indicate that lake levels in the Lake Ngami basin are responding to rainfall changes in the Angolan catchment area and local rainfall. The results confirm that the present-day anti-phase rainfall relationship between southern Africa and regions of equatorial Africa was extant during the late Quaternary over the Angolan highlands and NW Botswana. URI: http://hdl.handle.net/10311/152 Files in this item: 2
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