Climate change threatens east African coffee via borers

Some like it hot: The influence and implications of climate change on coffee berry borer (Hypothenemus hampei) and coffee production in east Africa. Jaramillo et al. 2011. PLoS One.

An important new paper published this week outlines the threat posed by the expansion of coffee berry borers in east Africa due to climate change.

This paper follows up research by the authors that was published in 2009. That paper looked at life history characteristics of the coffee berry borer (CBB), one of the worst pests of coffee, and how they might react to various climate change scenarios. This paper built on that data, looked at current distribution of CBB in east Africa, and modeled the change in distribution by 2050 based on two climate change scenarios.

The models indicated that CBB infestation will be worse in the arabica coffee producing regions of Ethiopia; the Ugandan part of the Lake Victoria and Mt. Elgon regions; Mt. Kenya, particularly in the coffee-producing areas of Embu and Meru, and the western part of Kenya, around Kitale and the Kenyan aide of Mt. Elgon; and most of Rwanda and Burundi. Further, it appears that increasing temperatures will likely double the number of generations of CBB per year in all current arabica-producing areas. Both models (using slightly different projections of climate change) are very similar, one figure is reproduced below.

Suitability of climate for CBB, year 2050. EI values indicate suitability, where 0 is unsuitable, and 100 is perfect. Click to enlarge. From Jaramillo et al. 2011.

Lest you view climate modeling (or climate change) with skepticism, the authors note that as recently as ten years ago, CBB were not reported above 1500 m. Now, due to increasing temperatures in coffee growing regions around the world, CBB can be found at higher altitudes, where arabica coffee is typically grown. CBB have been documented 300 m higher in Tanzania than they were ten years ago. The authors note that some of the changes predicted in their earlier paper, such as increased number of generations and broader distribution, seem to already be occurring.

The damage an increase in CBB to now-untouched coffee growing areas is serious and sobering. These impacts do not even incorporate other changes that are likely to take place with increasing temperatures: a change in the distribution of biological enemies of CBB, and the impact of changes in rainfall patterns, disrupted seasonality, and thermal stress to coffee plants.

The authors state,

We suggest that the best way to adapt to a rise of temperatures in coffee plantations could be via the introduction of shade trees in sun grown plantations.

They note adding shade trees can lead to a decrease in the temperature around coffee berries by up to 4°C, which in turn may reduce the rate of increase in CBB by 34%.  They go on to say shade coffee agroecosystems can serve as a refuge for beneficial arthropods, leading to higher levels of biological control of CBB, and they create a diversified and therefore more resilient system that will perform better under climate change. They conclude that while it is only one of many adaptation strategies, the use of shade trees is “… rational, affordable, and relatively easy for coffee farmers and other stakeholders to implement.”

The paper is open access, and you can read it the whole thing and view all the maps here. A link to an abstract in Spanish is available near the end.

Jaramillo, J., Muchugu, E., Vega, F., Davis, A., Borgemeister, C., & Chabi-Olaye, A. (2011). Some Like It Hot: The Influence and Implications of Climate Change on Coffee Berry Borer (Hypothenemus hampei) and Coffee Production in East Africa PLoS ONE, 6 (9) DOI: 10.1371/journal.pone.0024528

Posted in Climate change,Coffee regions,Research on coffee growing