Agricultural Intensification
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Agricultural intensification - Saving space for wildlife? Frédéric Baudron Thesis committee Thesis supervisor Prof. dr. K.E. Giller Professor of Plant Production Systems Wageningen University Thesis co-supervisors Dr. M. Corbeels Research Scientist Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) Brasilia, Brasil Dr. J.A. Andersson Research Scientist Wageningen University Centre for Applied Social Sciences (CASS), University of Zimbabwe Harare, Zimbabwe Dr. P. Tittonell Research Scientist Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD) Harare, Zimbabwe Other members Prof. dr. ir. C. Leeuwis, Wageningen University Prof. dr. D.H.M. Cumming, University of Cape Town, University of Zimbabwe Dr. ir. W.A.H. Rossing, Wageningen University Dr. P. Caron, Centre de coopération Internationale en Recherche Agronomique pour le Développement (CIRAD), Montpellier, France This research was conducted under the auspices of the C.T. de Wit Graduate School of Production Ecology and Resource Conservation ii Agricultural intensification – saving space for wildlife? Frédéric Baudron 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 Thursday 8 September 2011 at 11 a.m. in the Aula iii Frédéric Baudron Agricultural intensification – saving space for wildlife? 244 pages. Thesis, Wageningen University, Wageningen, NL (2011) With references, with summaries in Dutch, English and French. ISBN: 978-90-8585-964-2 Cover design: Nathalie La Hargue iv Pour Louis v vi Abstract ABSTRACT Increasing agricultural production and preventing further losses in biodiversity are both legitimate objectives, but they compete strongly in the developing world. In this study, current tensions between agricultural production and environmental conservation were described and analysed in Mbire District, an agricultural frontier shared with wildlife that lies in the Mid-Zambezi Valley, in the northern fringe of Zimbabwe. The potential of conservation agriculture (CA) to intensify agricultural production with minimum negative environmental effects was then explored. The population of Mbire District almost doubled between 1992 and 2002, while the livestock densities increased at rates above 15% in the early 1990s and the late 2000s. From 1980 to 2007, the expansion of farmland over the years was described by an exponential relationship. It was suggested that these changes affected elephant and buffalo numbers negatively. Increase in human population, increase in cattle population, and expansion of cotton farming were all drivers on the observed land use change. However, cotton farming was demonstrated to be paramount, enabling cattle accumulation and expansion of plough-based agriculture. The ‘environmental footprint’ per farm was increasing significantly with the area under cotton and with the number of draught animals owned. A kilogram of seed cotton required 50% more land, removed twice as much N, 50% more K and 20% more P than a kilogram of cereal. However, except for pesticide, one man-day invested in cotton production had a smaller environmental footprint than a man-day invested in cereal production. As farming in Mbire District is limited by labour more than by land, specialising in cereal production would increase the total area occupied by crops and fallows, whilst specializing in cotton production would reduce this area. Therefore, maintaining or increasing the relative profitability of cotton vs. cereal may ‘spare land’ for nature. Compared with current farmers’ cropping practices (CP), CA had no effect on cotton productivity during years that received average or above average rainfall. During a drier year, however, CA was found to have a slightly negative effect (110 kg ha-1 less in on-farm trials and 220 kg ha-1 less in farmers’ cotton fields). Most soils in the study area are coarse-textured soils, on which runoff were significantly greater vii with CA than with CP. For these reasons, farmers perceived ploughing as necessary during drier years to maximize water infiltration, but saw CA as beneficial during wetter years as a means to ‘shed water’ and avoid waterlogging. In Zimbabwe, the approach used in the extension of CA appears to differ little from an earlier attempt to intensify smallholder agricultural production almost a century earlier: the Alvord model. In particular, the rationale of African smallholder farming has been persistently ignored. The analysis of smallholder farming practices in Mbire District showed how the socio-economic constraints they faced predisposed them towards extensification. In particular, labour availability for weeding was found to be a major limiting factor in the area. The increased weed pressure in CA is therefore a major reason preventing smallholders from embracing it. As a conclusion, mitigating conflicts between agricultural production and biodiversity conservation will require major innovations, far beyond CA. CA should be seen as part of a larger basket of technologies aiming at ‘ecological intensification’. In parallel to the development of technical innovations, local institutions should be empowered and strong regulations put in place. Key words: agricultural frontier; smallholder; intensification; semi-arid area; wildlife; conservation agriculture; cotton; Zimbabwe. viii Contents Chapter 1. General introduction 1 Chapter 2. Delineating the drivers of waning wildlife habitat: The 15 predominance of cotton farming on the fringe of protected areas in the Mid-Zambezi Valley, Zimbabwe Chapter 3. What kind of farming can save wild nature? 49 Environmental footprint of farms in the Mid-Zambezi Valley, Zimbabwe Chapter 4. Comparative performance of conservation agriculture and 87 current smallholder farming in semi-arid Zimbabwe Chapter 5. Failing to Yield? Ploughs, conservation agriculture and 123 the problem of agricultural intensification. An example from the Zambezi Valley, Zimbabwe Chapter 6. General discussion and conclusions: Agricultural 157 intensification – saving space for wildlife? References 187 Appendix 211 Summary 220 Samenvatting 225 Résumé 231 Acknowledgements 237 PE&RC PhD Education Certificate 241 Curriculum Vitae 242 Funding 244 ix Chapter 1 General introduction Chapter 1 2 General introduction 1.1. BACKGROUND Competing claims for land are acute in developing countries (Giller at al., 2008). Reducing the number of undernourished people, estimated to be 1.02 billion (FAO, 2009a), not only requires a reduction in poverty and more equity in food access, but also an increase in food production. Meeting this goal comes at a cost for some of the last biodiversity-rich areas on Earth. The need to slow down deforestation and extinction rates appears more pressing as the links between biodiversity and ecosystem processes on which human existence depends become better understood (Vitousek et al., 1997; Chapin et al., 2000; Loreau et al., 2001). Increasing agricultural production and at the same time minimizing the negative consequences of agriculture on biodiversity constitute probably one of the greatest challenges ahead for developing countries. Meeting this challenge will not be short of a new revolution (Tilman, 1998; Gregory et al., 2002). Conversion of rainforest to palm plantations in Southeast Asian and its acceleration due to demand for biofuel is prominent in the media (e.g. Fargione et al., 2008). For African savannas, the consequences of the increased demand for food, fiber and fuel on the habitat of the emblematic megafauna is of equal importance. In this study, I analyse competing claims on land between agriculture and conservation in an African savanna shared by people and wildlife: the Mid-Zambezi Valley, in northern Zimbabwe. 1.2. NEED FOR INNOVATION Agriculture affects biodiversity directly through changes in land use. Wild species are actively removed, controlled by the release of synthetic biocides or affected by disturbances associated to farming (Figure 1). The loss of a given species, particularly in the case of ‘keystone species’, may lead to further extinctions in trophic chains (Mills et al., 1993; Pace et al., 1999). In addition to these local impacts, agriculture may affect biodiversity regionally or globally through indirect changes (Figure 1). First, agriculture will often affect the biodiversity of adjacent landscapes through habitat fragmentation and fragment isolation (Pimm et al., 1995; Fischer and Lindenmayer, 2007). Second, agriculture affects hydrological and biogeochemical cycles, which may have far-reaching consequences on distant biodiversity. Farmland 3 Chapter 1 runoffs may cause siltation of distant streams, lakes, estuaries and coral reefs (Farella et al., 2001). Similarly, mobile nutrients such as nitrate and pesticides may contaminate regions downstream or downwind (Pimentel, 1995; Almasri and Kaluarachchi, 2004). The conversion of natural ecosystems to agriculture also releases CO2, which may contribute to global climate change and affect global biodiversity (Dixon et al., 1994; Vitousek et al., 1997). Increased Release of Biotic Biotic Alteration of Release Disturbances Synthetic Removals (e.g. Additions Hydrological of limiting (e.g. tillage, fire, Biocides competitors, (domestic Cycles elements grazing) predators, pests, species) (N, P) diseases) Altered Altered Soil