Coffee Leaf Traits, Bean Quality and Biochemistry across Elevation and Shade Gradients in Ethiopia

Abstract

According to model projections, coffee cultivation areas will need to move to higher elevations as suitability moves upslope to compensate for increased temperatures. However, shifting coffee-growing areas upslope may bring conflicts with land use and crops other than coffee and induce adverse socio-economic and environmental impacts associated with deforestation for new coffee cultivation. Moreover, model projections are largely limited to ex-situ experiments based on downscaled global climate models, and thus empirical data are still needed to assess climate change impacts on coffee production in Ethiopia in the future. Furthermore, conditions such as shade tree canopy closure, soil fertility and elevation may either ameliorate or exacerbate climate change impacts. In the absence of significant interventions, this could result in considerable land use change, increased vulnerability of coffee-dependent livelihoods and a potential shortage of coffee supply. Hence, to generate trustworthy and accurate information for climate-resilient Ethiopian coffee production, more field-based experiments are needed. In this PhD thesis, I used coffee plants growing at contrasting elevations using a space-for-time substitution approach for warming in south-west Ethiopia. The coffee plants were superimposed under various shade tree species with multi-strata canopy architecture. The potential of increasing canopy closure in modulating responses to increasing temperature, and the associated effect on coffee plant traits, green bean quality and biochemistry, were thoroughly explored. Based on my findings, I was able to identify potential limiting factors, to close the coffee quality gap by providing improved management recommendations tailored to the local ecological conditions while acknowledging the dynamic drivers (mainly resource availability and climatic variability) for the long-term sustainability of the coffee industry.