Finding Solutions Where Equilibrium Models Fail Xavier Poshiwa

Finding Solutions Where Equilibrium Models Fail Xavier Poshiwa

African wildlife and people: finding solutions where equilibrium models fail Xavier Poshiwa i Thesis committee Promoters Prof. Dr H.H.T. Prins Professor of Resource Ecology Wageningen University Prof. Dr E.C. van Ierland Professor of Environmental Economics and Natural Resources Wageningen University Co-promoters Dr I.M.A. Heitkönig Assistant professor, Resource Ecology Group Wageningen University Dr R.A.Groeneveld Assistant professor, Environmental Economics & Natural Resources Group Wageningen University Other members Prof. Dr J.H.J. Schaminee, Wageningen University / Radboud University Nijmegen Prof. Dr W.J.M. Heijman, Wageningen University Prof. Dr A.J. van der Zijpp, Wageningen University Dr L.G. Hein, Wageningen University This research was conducted under the auspices of the C.T. de Wit Graduate School for Production Ecology and Resource Conservation (PE&RC), and the Wageningen School of Social Sciences (WASS). ii African wildlife and people: finding solutions where equilibrium models fail Xavier Poshiwa Thesis submitted in fulfilment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus Prof. Dr M.J. Kropff in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Monday 2 December 2013 at 11 a.m. in the Aula. iii Xavier Poshiwa African wildlife and people: finding solutions where equilibrium models fail 174 pages. PhD thesis, Wageningen University, Wageningen, NL (2013) With references, with summaries in Dutch and English ISBN 978-94-6173-761-8 iv To Sibongile, Tadiwa, Tanaka and my parents …..you are all a constant source of inspiration, much love. v Contents Abstract…………………………………………………………………………….....xi 1 General introduction……………………………………………………................1 Xavier Poshiwa 1.1 Background..................................................................................................1 1.2 History of equilibrium paradigm..................................................................2 1.3 Equilibrium dynamics in dryland savannas..................................................3 1.4 The non-equilibrium paradigm.....................................................................4 1.5 Non-equilibrium dynamics in dryland savannas..........................................5 1.6 Uncertainty and risk linked with non-equilibrium dryland ecosystems.......6 1.7 Study objectives and approach.....................................................................7 1.8 Study area.....................................................................................................9 1.9 Thesis outline.............................................................................................10 2 The effect of land use on vegetation composition in the southeastern lowveld of Zimbabwe………………………………………………………...........................15 Xavier Poshiwa; Ignas M. A. Heitkönig; Craig Morris; Kevin P. Kirkman; Ekko C. van Ierland and Herbert H.T. Prins. 2.1 Introduction................................................................................................16 2.2 Materials and methods ...............................................................................18 2.2.1 Study area ..............................................................................18 2.2.2 Vegetation sampling ................................................................19 2.2.3 Herbivore densities and rainfall ...............................................20 2.2.4 Biomass production and soil sampling ....................................21 2.2.5 Statistical analyses ...................................................................22 2.3 Results........................................................................................................23 2.3.1 Species composition.................................................................23 2.3.2 Grass species community.........................................................23 2.3.3 Land use effects on grass species community..........................25 2.3.4 Woody species community.......................................................27 2.3.5 Land use effects........................................................................27 vi 2.3.6 Grass and woody species composition explained by environmental variables ...........................................................29 2.3.7 Herbaceous biomass production and basal cover ....................31 2.4 Discussion .................................................................................................33 2.4.1 Grasses .....................................................................................33 2.4.2 Woody plants ...........................................................................34 2.4.3 Environmental variables ..........................................................35 2.5 Conclusion .................................................................................................37 3 Rainfall, primary production and cattle density relationships in southeastern lowveld of Zimbabwe.............................................................................................39 Xavier Poshiwa; Ignas M. A. Heitkönig; Amon Murwira; Ekko C. van Ierland and Herbert H. T Prins. 3.1 Introduction ...............................................................................................40 3.2 Materials and methods ..............................................................................42 3.2.1 Study area ................................................................................42 3.2.2 Normalised Difference Vegetation Index (NDVI) and rainfall data ..........................................................................................43 3.2.3 Cattle changes and densities ...................................................44 3.2.4 Statistical analysis...................................................................44 3.3 Results.......................................................................................................46 3.3.1 Rainfall....................................................................................46 3.3.2 Cattle.......................................................................................49 3.3.3 Step function...........................................................................52 3.3.4 Cattle age categories and sex response to drought and their recovery ..................................................................................58 3.4 Discussion.................................................................................................62 Acknowledgements.........................................................................................66 vii 4 Reducing rural households annual income fluctuations due to rainfall variation through diversification of wildlife use: portfolio theory in a case study of southeastern Zimbabwe………………………......................................................67 Xavier Poshiwa; Rolf A. Groeneveld; Ignas M. A. Heitkönig; Herbert H. T. Prins and Ekko C. van Ierland. 4.1 Introduction................................................................................................68 4.2 Methods......................................................................................................70 4.2.1 Study area.................................................................................70 4.2.2 General framework...................................................................71 4.2.3 Data collection..........................................................................73 4.2.4 Data analysis.............................................................................73 4.3 Results........................................................................................................75 4.3.1 Household socio-economic and agro-pastoral characteristics..75 4.3.2 Changes in cattle numbers with variations in annual rainfall...77 4.3.3 Variations in crop yields with rainfall fluctuations..................79 4.3.4 Changes in potential wildlife revenues with fluctuations in rainfall......................................................................................81 4.3.5 Wildlife income as a strategy for managing and coping with drought risk..............................................................................82 4.4 Discussion..................................................................................................83 4.5 Implications for conservation....................................................................86 Acknowledgements.........................................................................................86 Appendix 4.1...............................................................................................................87 Appendix 4.2...............................................................................................................89 Appendix 4.3...............................................................................................................91 Appendix 4.4...............................................................................................................92 viii 5 Wildlife as insurance against rainfall fluctuations in a semi-arid savanna setting of southeastern Zimbabwe…………………………………………………..............93 Xavier Poshiwa; Rolf A. Groeneveld; Ignas M. A. Heitkönig; Herbert H. T. Prins and Ekko C. van Ierland. 5.1 Introduction................................................................................................94 5.2 Methods......................................................................................................98

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