GeloriniPhD (PDF , 6973kb) - University of York

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INTRODUCTION Vegetation, land use and rural livelihoods The rainfall and temperature variability, in relation to the rapid rate of population growth in East Africa (~7.1% per annum), significantly determines the livelihood strategies of indigenous food producers (e.g., cultivators, livestock keepers and fishers) who exploit the country’s natural resources (Conway et al., 2005; Thornton et al., 2008) (Fig. iii). In total, about 70 to 80% of the East African workforce is employed in the agricultural sector (FAOSTAT, 2009), involving many distinct crop-livestock systems exploiting a wide range of agro-products (e.g., banana, maize, sorghum, millet, potatoes, meat, milk). Over 75% of total agricultural output is provided by smallholder farmers, with farm sizes of about 2.5 ha on average, mainly producing for home-consumption, and to a lesser degree for (semi-)commercial sale of goods. The farming activities are completely organised and directed within the family, operating within a network of relations at the community level and using limited technological innovations (Salami et al., 2010). Intensive small-scale subsistence farming is the most widespread permanent agricultural system (Widgren and Sutton, 2004) found in areas with high population density (Okigbo, 1990), such as the Naya in northwestern Tanzania (Maruo, 2002), the Chagga in north Tanzania (Fernandes et al., 1984) and the Ankole in southwestern Uganda (Kasfir, 1993). In sparsely populated semi-arid regions, such as the Ngorongoro district in north Tanzania and the Narok district in southwestern Kenya, cattle breeding forms an essential part of the rural livelihoods (Dixon et al., 2001). To optimise the use of rangeland resources for meat and milk production, transhumant pastoralists, such as the Maasai, move their herds throughout the year, maintaining semi-permanent home bases. In times of drought and during the night, livestock enclosures protect the herds from predators and from raiding by other humans (Marshall, 2000; Butt, 2010). In the last few decades, many of East Africa’s life-support have experienced dynamic changes induced by environmental, socioeconomic and political impacts (Maruo, 2002). Climate variability, however, is likely to have the most severe impact on resource-poor agriculturalists, leading to changes in productivity of rainfed crops and forage, reduced water availibility and severity of crop, livestock and human diseases (Goulden, 2005; Thornton et al., 2008). Moreover, soil erosion has severely increased as a result of land-use intensification (over-cultivation, over-grazing, logging), land fragmentation (loss of buffer zones) and the lack of fertilisers (Pomeroy et al., 2003; Ngecu et al., 2004), and is detrimental for soil nutrients and food production potential (Toy et al., 2002). Land degradation and the accelerating conversion of natural lands for agricultural purposes also causes a substantial loss of plant, mammal and bird diversity (Pomeroy et al., 2003). The threat of extinction may be particularly acute for the more than a million estimated species of fungi living in direct association with plants (e.g., Hawksworth, 1991, 1993; Hyde and Hawksworth, 1997). For example, based on limited data in Uganda the rate of overall biodiversity loss is estimated to have reached 10% per decade, with even higher values in savanna systems (~20%) and agro-ecosystems (~50%) (Pomeroy and Mwima, 2002). Also surface water resources, such as lakes and wetlands, become progressively depleted by eutrophication and/or siltation due to the combined impact of human activities and climate variability (e.g., Verschuren et al., 2002; Ngaira, 2009; Stager et al., 2009). Anomalies in the nutrient cycling of large water bodies, such as L. Tanganyika, severely affect fish abundance and fishery (O’Reilly et al., 2003). A recent more qualitative and quantitative assessment of the biogeochemical cycle in L. Tanganyika revealed that anthropogenic global warming may possibly be the main driver of decreasing lake productivity over the past 90 years (Tierney et al., 2010). Thus, by studying current and past ecosystem responses to human impact and climate change, strategies necessary for successful community-based natural resource management can be developed to retain resilience of the ecosystems, which support them (e.g., Willis and Bhagwat, 2010). . 22 .
1 Figure 2 Global Land-Cover 2000 map of Africa. Fig. iii. Vegetation map of Africa, with special reference to the East african region, which is mainly characterised by cropland, mosaic forest, deciduous woodland/shrubland and open grassland (Mayaux et al., 2004). . 23 . New land-cover map of Africa Journal of Biogeography 31, 861–877, ª 2004 Blackwell Publishing Ltd 869 INTRODUCTION
Page 3: 2011 Thesis submitted in partial fu
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Page 14 and 15: TABLE OF CONTENTS A.1. Septated spo
Page 17 and 18: Abstract . 17 . ABSTRACT In tropica
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Page 21: . 21 . INTRODUCTION Atlantic Ocean
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Page 37 and 38: . 37 . INTRODUCTION Mumbi, C.T., Ma
Page 39 and 40: . 39 . INTRODUCTION lipids in an eq
Page 41 and 42: . 41 . CHAPTER 1 Diversity and ecol
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CHAPTER 2 Modern non-pollen palynom
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CHAPTER 3 Effects of Land use on th
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CHAPTER 4 Validation of non-pollen
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General discussion and conclusion .
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. 189 . GENERAL DISCUSSION AND CONC
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SAMENVATTING beperkingen (i.v.m. de
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APPENDICES Appendix I. Raw NPP data
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APPENDICES Mahuhura Kitere Katanda
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APPENDICES Appendix II. Raw NPP dat
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APPENDICES L. Chibwera Identificati
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APPENDICES L. Chibwera Identificati
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APPENDICES Appendix III. Raw NPP da
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APPENDICES L. Kanymukali Identifica
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Photograph by Bob Rumes Front cover
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