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- SourceAvailable from: Frans Bongers[Show abstract] [Hide abstract]
ABSTRACT: Although the human domestication of forest and tree resources is often considered to result in resource degradation, it may also lead to improved resource potentials. This paper assesses the nature and dynamics of gum and resin focused woodland exploitation and management systems in Ethiopia in the context of degradation and domestication processes. In three sites with commercial gum resin producing woodlands and production history, we studied variation in (i) woodland management and gum resin production systems and (ii) socio-economic and biophysical factors that condition the management and production systems. On the basis of their organizational features, we formulated nine production models and related them to different phases of domestication and different degrees of ecosystem degradation. The production systems gradually evolved from the extraction of wild trees to production in an adapted forest system. However, domesticated woodlands with an adapted forest structure and composition and increased provisioning services are still little developed despite decades of production history. Many of these woodlands are undergoing serious degradation because of low quality management practices. This is mainly attributable to existing land use practices and the social arrangements for the production of and trade in the gums and resins. The findings illustrate that domestication involves not only a change in ecological and production systems but also the development of social arrangements for production and trade. We conclude that the status of domestication in a social sense determines whether forests and/or specific forest resources are degraded or aggraded in the sense of resource enrichment. Copyright © 2011 John Wiley & Sons, Ltd.Land Degradation and Development 03/2014; 25(2). DOI:10.1002/ldr.1153
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ABSTRACT: Classifying multi-temporal image data to produce thematic maps and quantify land cover changes is one of the most common applications of remote sensing. Mapping land cover changes at the regional level is essential for a wide range of applications including land use planning, decision making, land cover database generation, and as a source of information for sustainable management of natural resources. Land cover changes in Lake Hawassa Watershed, Southern Ethiopia, were investigated using Landsat MSS image data of 1973, and Landsat TM images of 1985, 1995, and 2011, covering a period of nearly four decades. Each image was partitioned in a GIS environment, and classified using an unsupervised algorithm followed by a supervised classification method. A hybrid approach was employed in order to reduce spectral confusion due to high variability of land cover. Classification of satellite image data was performed integrating field data, aerial photographs, topographical maps, medium resolution satellite image (SPOT 20 m), and visual image interpretation. The image data were classified into nine land cover types: water, built-up, cropland, woody vegetation, forest, grassland, swamp, bare land, and scrub. The overall accuracy of the LULC maps ranged from 82.5 to 85.0 %. The achieved accuracies were reasonable, and the observed classification errors were attributable to coarse spatial resolution and pixels containing a mixture of cover types. Land cover change statistics were extracted and tabulated using the ERDAS Imagine software. The results indicated an increase in built-up area, cropland, and bare land areas, and a reduction in the six other land cover classes. Predominant land cover is cropland changing from 43.6 % in 1973 to 56.4 % in 2011. A significant portion of land cover was converted into cropland. Woody vegetation and forest cover which occupied 21.0 and 10.3 % in 1973, respectively, diminished to 13.6 and 5.6 % in 2011. The change in water body was very peculiar in that the area of Lake Hawassa increased from 91.9 km(2) in 1973 to 95.2 km(2) in 2011, while that of Lake Cheleleka whose area was 11.3 km(2) in 1973 totally vanished in 2011 and transformed into mud-flat and grass dominated swamp. The "change and no change" analysis revealed that more than one third (548.0 km(2)) of the total area was exposed to change between 1973 and 2011. This study was useful in identifying the major land cover changes, and the analysis pursued provided a valuable insight into the ongoing changes in the area under investigation.Environmental Monitoring and Assessment 12/2013; 186(3). DOI:10.1007/s10661-013-3491-x
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ABSTRACT: Intestinal parasitic infectionsare a major public health burden in tropical countries. Although all HIV/AIDS patients are susceptible to parasitic infections, those having lower immune status are at greater risk. The aim of this study was to determine the prevalence of intestinal parasitic infections in patients living with HIV/AIDS. This was a facility-based cross-sectional study. A total of 343 consecutively sampled HIV/AIDS patients from the HIV care clinic of Hawassa University Referral Hospital were included. Subjects were interviewed for demographic variables and diarrheal symptoms using structured questionnaires. Stool examinations and CD4 cells counts were also performed. The prevalence of intestinal parasitic infection was 47.8% among HIV/AIDS patients; single helminthic infection prevalence (22.7%) was higher than that the prevalence of protozoal infections (14.6%). About 54% of study participants had chronic diarrhea while 3.4% had acute diarrhea. The prevalence of intestinal parasites in patients with chronic diarrhea was significantly higher than in acute diarrhea (p <0.05). Non-opportunistic intestinal parasite infections such as Ascaris lumbricoides, Taenia spp., and hookworm were commonlyfound, regardless of immunestatus or diarrheal symptoms. Opportunistic and non-opportunistic intestinal parasitic infection were more frequent in patients with a CD4 count of <200/mm(3) (OR=9.5; 95% CI: 4.64-19.47) when compared with patients with CD4 counts of ≥500 cells/mm(3). Intestinal parasitic infections should be suspected in HIV/AIDS-infected patients with advanced disease presenting with chronic diarrhea. Patients with low CD4 counts should be examined critically for intestinal parasites, regardless of diarrheal status.The Journal of Infection in Developing Countries 11/2013; 7(11):868-72. DOI:10.3855/jidc.2906
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