Exploring adaptation strategies of coffee production to climate change

The increase in demand for agricultural products driven by population and economic growth and dietary changes has been met through agricultural intensification, most notably by the green revolution. The way this intensification was achieved came at the cost of several negative environmental and health externalities due to high use of synthetic inputs, water, and conversion of diversified landscapes to monocultures. Consequently, agriculture is one of the main drivers of climate change, while at the same time being most vulnerable to it. Tackling this issue requires a shift in perspective from a production centred agricultural intensification approach to alternative pathways such as sustainable intensification and climate smart agriculture, envisioning agriculture to provide multiple ecosystem services. Coffee (Coffea arabica L.) is particularly vulnerable to climate change. It is a perennial crop, adapted to a narrow climatic niche, while relying on a narrow genetic base and farmed predominantly by smallholder farmers. Climate change impact assessments have relied on statistical niche models that analyse changes in future monthly temperature and precipitation of coffee growing areas, indicating significant investment needs for adaptation to climate change. While some areas will be able to continue in the coffee business, provided adaptation takes place, climate change will render coffee production economically non-viable in other areas. Only few areas are expected to experience a beneficial change. Commonly suggested agronomic adaptation options are the use of improved coffee varieties, management of shade trees and irrigation. Yet, improved understanding is required regarding where, when and how these general adaptation options can contribute to adaptation needs. Responding to these knowledge gaps will require new approaches for climate change impact assessment. These methods need to go beyond analysing monthly temperature and precipitation data and include the ecophysiological response of coffee to the interactive effects of light, temperature, water and atmospheric chemistry. It entails the recognition of genotypic and phenotypic plasticity of coffee as well as facilitative and competitive interactions with shade trees. Such an analysis needs to integrate current knowledge, highlight knowledge gaps and explicitly take into account uncertainty. The aim of this thesis is to improve our understanding of the coffee (Coffea arabica L.) crop’s response to climate change and evaluate adaptation options. First, different coffee agro-ecological systems are compared along an elevation gradient in the Mt. Elgon area of Uganda. This provides insights on how coffee farmers adapt to a range of temperature and precipitation conditions and how this affects coffee yield. Second, based on an extensive literature review and an existing process-based coffee model, the interactive effects of climate on coffee yield and the modifying effects of associating coffee with shade trees is explored along two East African mountain slopes, namely Mt. Elgon, Uganda, and Mt. Kilimanjaro, Tanzania. The presented approach aids in providing shade tree recommendations in space and time. Third, the uncer-