Not so robust: Robusta coffee production is highly sensitive to temperature.

Coffea canephora (Robusta coffee) is the most heat tolerant and 'robust' coffee species and therefore considered more resistant to climate change than other types of production coffee. However, the optimum production range of Robusta has never been quantified, with current estimates of its optimal mean annual temperature range (22-30 degrees C) based solely on the climatic conditions of its native range in the Congo basin, Central Africa. Using 10 years of yield observations from 798 farms across South East Asia coupled with high-resolution precipitation and temperature data we used hierarchical Bayesian modelling to quantify Robusta's optimal temperature range for production. Our climate based models explained yield variation well across the study area with a cross-validated mean R(2) = 0.51. We demonstrate that Robusta has an optimal temperature below 20.5 degrees C (or a mean minimum / maximum of