Arabica coffee production across Ethiopia, South Sudan and Kenya is under threat from climate change and could cease completely by 2080, according to a new report from scientists based at the Royal Botanical Gardens in Kew in the UK.
Coffee is the world’s favourite beverage and the second-most traded commodity after oil. In 2009/10, coffee accounted for exports worth an estimated $15.4 billion worldwide, when some 93.4 million bags were shipped, with total employment in the coffee sector estimated at about 26 million people in 52 producing countries.
However, the productivity (green bean yield) of Arabica is tightly linked to climate change.
The Kew report notes that the optimum mean annual temperature range for Arabica is 18-21°C, or up to 24°C. At temperatures above 23°C, development and ripening of fruits are accelerated, often leading to the loss of beverage quality.
The report says that evidence from coffee farmers, from numerous coffee-growing regions around the world, shows that they are already suffering from the influence of increased global warming, although it acknowledges that precise modelling of this influence for either Arabica or robusta coffee is limited.
The study centred around populations of wild indigenous coffee in Ethiopia, southeastern Sudan and Kenya.
It said that the largest and most diverse populations of indigenous (wild) Arabica occur in the highlands of southwestern Ethiopia, in southeastern South Sudan (Boma Plateau) and northern Kenya (Mt Marsabit), at altitudes of between 950 metres and 1,950 metres, although 1,200 metres is the most frequent lower altitude limit.
The report said that its modelling shows a profoundly negative trend for the future distribution of indigenous Arabica coffee under the influence of accelerated global climate change.
It predicts that unless addressed, “The most favourable outcome would be a 65 per cent reduction in the number of bioclimatically suitable localities, and at worst an almost 100 per cent reduction by the year 2080.”
The report adds that even if new localities for Arabica were recorded.
“These are likely to represent a small proportion of those already known, based on the few remaining suitable areas for which we do not have occurrence records,” it reads.
The scientists also point out that Arabica has a relatively long generation time: Even in cultivation, it requires a minimum of three to four years to produce fruit and at least five to eight years to reach maximum reproductive potential.
The scientists say that coffee beans are also likely to suffer from increasing numbers of pests and diseases as temperatures rise.
Arabica coffee and Robusta coffee are the two main species used in the production of coffee, although the former is by far the most significant, providing approximately 70 per cent of commercial production.
The report adds that although commercial growers could still grow their own crops by watering and artificially cooling them, the wild type has much greater genetic diversity, which is essential to help plantations overcome threats like pests and disease.
Justin Moat, one of the report’s authors, said: “The worst case scenario, as drawn from our analyses, is that wild Arabica could be extinct by 2080. This should alert decision makers to the fragility of the species.”
The new study, published in the Public Library of Science ONE journal, used computer modelling to predict the survival prospects of Arabica coffee for the first time, based on three different climate change scenarios.
Aaron Davis, head of coffee research at the Royal Botanic Gardens, said: “Arabica can only exist in a very specific place with a very specific number of other variables. It is mainly temperature but also the relationship between temperature and seasonality — the average temperature during the wet season, for example.”
The researchers, however, said their estimates were “conservative” because they did not take into account the widespread deforestation taking place in the highland forests where the beans are grown, or other factors such as a drop in the number of birds who spread seeds.
Even if the beans do not disappear completely from the wild, climate change is highly likely to impact on yields and the taste of coffee beans in future decades, they added.