Modelling the dynamic interactions between food production and ecosystem services: a case study in Benin

Given the high levels of food insecurity and the loss of vital ecosystem services associated with deforestation, countries in sub-Saharan Africa (SSA) face a major dilemma. How can they produce enough food in a changing climate to feed an increasing population while protecting natural forests and woodlands that provide a wide array of ecosystem services beneficial to livelihoods? Thus, the objectives of this thesis are twofold. First, to further enhance the understanding of the dynamic interactions between food production, and natural and semi-natural ecosystems with a case study in Benin. Second, to further enhance the understanding of how hydrological ecosystem services can be captured in an accounting framework. Understanding hydrological ecosystem services is key to understanding the multi-directional relationship between food production and ecosystem services supply from natural and semi-natural ecosystems. First, I examine how a spatially explicit ecohydrological model can be used to analyse multiple hydrological ecosystem services in line with the ecosystem accounting framework. The hydrological ecosystem services include crop water supply for rainfed agriculture, household water supply (both groundwater supply and surface water supply), water purification, and soil erosion control. Second, I develop a general modelling approach for analysing the effects of deforestation on the availability of water for irrigation at the watershed level, and I apply the approach to the Upper Oueme watershed in Benin. Third, I analyse the impact of climate change on agricultural intensification options. Finally, I quantify trade-offs between per capita food availability and protecting forests and woodlands at different levels of yield increases taking into account climate change, population growth. This thesis shows that the integration of hydrological ecosystem services into an accounting framework can provide relevant information at appropriate scales suitable for decision-making. It is empirically feasible to distinguish between service capacity and service flow of hydrological ecosystem services. This requires appropriate decisions regarding physical and mathematical representation of ecohydrological processes, spatial heterogeneity of ecosystems, temporal resolution, and required model accuracy. This thesis also shows that opportunities for irrigation expansion depend on conservation of forests and woodlands in the headwaters of the rivers feeding the irrigation scheme. Opportunities for agricultural intensification in SSA are likely to diminish with climate change, hence increasing pressure to expand cultivated areas in order to meet increasing food demand. Climate change will lead to substantial reductions in; exploitable yield gaps for major food crops, rainfed cropland areas that can support the cultivation of two or more crops per year, and water availability for irrigation expansion. Furthermore, in the far future crop yields will have to increase at a faster rate than has been recorded over the past two and half decades in order to maintain current levels of per capita food availability. Failure to achieve the required levels of yield increases is likely to lead to the conversion of substantial areas of forests and woodlands for crop cultivation. Based on the results of this thesis, four main recommendations to help address the dual challenge of food security and ecosystem protection in Benin and the larger SSA region are made: (i) promote a precautionary approach to forest and woodland conservation, (ii) promote cross-sectoral policy coherence and consultations, (iii) promote the development of satellite ecosystem accounts consistent with national accounts, and (iv) identify, evaluate and implement adaptation and resilience measures to reduce agricultural vulnerability to climate change.