The potential of shade trees to improve microclimate in coffee production systems and contribute to the protection of coffee yield and quality in a changing climate

Wagner, Sigrun (2022) The potential of shade trees to improve microclimate in coffee production systems and contribute to the protection of coffee yield and quality in a changing climate. Doctoral thesis (PhD), Manchester Metropolitan University.

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Abstract

Climate change is a major challenge to which global coffee production must adapt. With Coffea arabica being especially sensitive to rising temperatures, shade trees present a promising adaptation strategy, as there is some evidence that they can modify microclimate. Employing an interdisciplinary approach, combining biophysical and sociological research, this study investigated the effect of shade on coffee production on the southern slope of Mt. Kilimanjaro with the aim of finding suitable strategies to optimise coffee production systems and ensure optimal yield and quality, thus assuring farmers’ livelihoods into the future, in the face of climate change. Precipitation records from coffee plantations were analysed for changes in weather patterns in the last two decades. The influence of shade on microclimate, leaf temperature, coffee yield and physical quality aspects was assessed in coffee plantations and smallholder systems. Additionally, focus group discussions and interviews with small-scale farmers were conducted to explore farmers’ knowledge on the impacts of weather extremes on coffee production and the ecosystem services different tree species provide. This research shows that climate change at Mt. Kilimanjaro manifests as droughts and shorter wet seasons with less frequent but heavier rainfall events, challenges to which coffee farmers will have to adapt. Shade trees show potential in adaptation of coffee production systems to climate change, as they reduce maximum air temperatures and can reduce leaf temperature extremes during hot periods, without having negative effects on nocturnal temperatures, which are beneficial for coffee production. In coffee plantations, no effect of shade on yields was observed while a slight reduction was observed for smallholder systems. Coffee quality benefits from shade, as different shade components are associated with an increase in bean size and weight. Farmers identified Albizia schimperiana as an important tree species, providing regulatory ecosystem services to improve coffee production. Recommendations need to take farmers’ priorities into account, including their willingness to trade some reduction in coffee production for other services, such as food, fodder or firewood, which were identified as the most important ecosystem services for farmers at Mt. Kilimanjaro.