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Decision and Policy Analysis Research Area – DAPA

A bitter cup: climate change profile of global production of Arabica and Robusta coffee

Coffee can have a bitter taste in more than one way. Only little coffee is consumed at its origins. Nearly all of it is traded on international stock markets and exported to fuel the white collar service industry. This way it links marginalized small holder producers with the urban elite like few other products. Western ideals of lush tropical mountain forests contrast with a reality in which low prices and failing harvests result in a high poverty risk for producers. A study published by DAPA in December in “Climatic Change” adds to previous evidence for the perhaps most unfortunate link between the two worlds: climate change caused by anthropogenic emissions harshly compromises the livelihoods of millions of coffee farmers.

The study concludes that about half of the area that can be used for coffee production is threatened by climate change. This finding is independent of the emissions scenario. Even if the 2°C warming target could still be met large areas would be lost. The authors attribute this to the susceptibility of coffee to higher temperatures. Most coffee is produced in commercial plantations on highland plains with relatively cool temperatures. Global warming moves the optimal altitudinal range for production up the mountain slopes where drastically less area is available for efficient farming. Increasing prices might create economic incentives to migrate coffee farming to locations previously unused for agriculture and cause deforestation with all its bitter consequences for local ecosystems.

This study is the first global assessment of the impacts of climate change on both coffee species. Previous studies (several of which can be found on this blog) were all limited to regional assessments. Most local studies agreed on a pressure to migrate coffee in altitude. Some studies however also suggested that latitudinal migration to previously cooler climate would be one of two of coffee drinkers’ silver bullets to climate change. Our global model disappoints such hopes by pointing to the coffee crop’s need for a stable climate to produce economical yields, ruling out migration to extreme Southern or Northern locations. The other silver bullet was meant to be Robusta coffee which can sustain much higher temperatures than the dominant Arabica species. The reasoning was that Robusta could simply replace Arabica once it becomes too hot for the latter. Our modeling exercise emphasizes that Robusta today is indeed grown at higher temperatures than Arabica, but also at lower latitudes with an even more stable climate throughout the year. Therefore Robusta will not be the simple way out, even if it should be able to replace Arabica in some African and Asian locations.

DAPA will thus continue to work with a broad range of stakeholders along the entire coffee supply chain, from producers to roasters, to find solutions to this complex challenge. This study demonstrated again that we can’t just sit back and watch. Optimal adaptation measures have to be site specific and vary from one context to the next. If we fail to develop smart practices we will have to swallow a bitter cup (or worse: drink tea).


Our method built on years of DAPA’s experience in modeling the impacts of climate change on coffee. We first combined sets of occurrence locations gathered in several local projects as reference data. Several background sampling strategies that are suggested by the literature were used in an ensemble approach. The occurrence sample and the background samples were used to train three classification algorithms (SVM, RandomForest, and MaxEnt). A total of 135 models per species were then used to classify climate layers for current and future conditions (2050s – RCP2.6, 6.0 and 8.5).

Bunn, C., Läderach, P., Ovalle Rivera, O. & Kirschke, D. A bitter cup: climate change profile of global production of Arabica and Robusta coffee. Climatic Change 1–13 (2014). doi:10.1007/s10584-014-1306-x

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