A study conducted by scientists at the Royal Botanic Gardens, Kew (UK), in collaboration¹ with scientists in Ethiopia, reports that climate change alone could lead to the extinction² of wild Arabica coffee (Coffea arabica) well before the end of this century. Wild Arabica is considered important for the sustainability of the coffee industry due to its considerable genetic³ diversity. The Arabicas grown in the world's coffee plantations⁵ are from very limited genetic stock and are unlikely to have the flexibility⁶ required to cope with climate change and other threats, such as pests and diseases. In Ethiopia, the largest producer of coffee in Africa, climate change will also have a negative influence on coffee production. The climate sensitivity of Arabica is confirmed, supporting the widely reported assumption that climate change will have a damaging impact on commercial coffee production worldwide. These are worrying prospects⁷ for the world's favourite beverage⁸（饮料） – the second most traded commodity（上市商品） after oil, and one crucial to the economies of several countries. The research is published in PLOS ONE on 7 November 2012. The study, which uses computer modelling, represents the first of its kind for wild Arabica coffee. In fact, modelling the influence of climate change on naturally occuring populations of any coffee species has never been undertaken. Surprisingly, even studies on plantation⁴ coffee have been limited, despite the concerns of farmers and other industry stakeholders.

 

The researchers used field study and 'museum' data (including herbarium植物标本 specimens) to run bioclimatic models for wild Arabica coffee, in order to deduce the actual (recorded) and predicted geographical⁹ distribution for the species. The distribution was then modelled through time until 2080, based on the Hadley Centre Coupled Model, version 3 (HadCM3), a leading model used in climate change research, and the only one available that covered the desired time intervals¹⁰, for several emission¹¹ scenarios¹², at the resolution required (1 km). Three different emission scenarios over three time intervals (2020, 2050, 2080) were used. The models showed a profoundly negative influence on the number and extent of wild Arabica populations.

 

Two main types of analysis were performed: a locality analysis and an area analysis. In the locality analysis the most favourable¹³ outcome is a c. 65% reduction in the number of pre-existing bioclimatically suitable localities, and at the worst, an almost 100% (99.7%) reduction, by 2080. In the area analysis the most favourable outcome is a 38% reduction, and the least favourable a c. 90% reduction, by 2080. Bioclimatic suitability refers to the combination of climatic variables that are necessary for the health and survival of a species: loss of optimum bioclimatic（生物气候学的） suitability places natural populations under severe environmental stress, leading to a high risk of extinction. This study assesses the survival of Arabica, rather than productivity or beverage quality, under the influence of accelerated climate change. There are other studies showing that the productivity (yield of coffee beans) and beverage quality (e.g. taste) of Arabica are tightly linked to climatic variability, and are strongly influenced by natural climatic fluctuations¹⁴（波动）.

 

Of the two analyses undertaken, the locality analysis is regarded by the authors as the most pragmatic and informative¹⁵. The predicted reduction in the number of Arabica localities, between 65% and 99.7%, can be taken as a general assessment¹⁶ of the species' survival as a whole, given the scope and coverage¹⁷ of the data and analyses used in the study. However, the predictions are regarded as 'conservative', as the modelling does not factor in the large-scale deforestation that has occurred in the highland¹⁸ forests of Ethiopia and South Sudan (the natural home of Arabica coffee). Moreover, because of the lack of suitable data, the models assume intact natural vegetation, whereas the highland forests of Ethiopia and South Sudan are highly fragmented due to deforestation. Other factors, such as pests and diseases, changes in flowering times, and perhaps a reduction in the number of birds (which disperse¹⁹ the coffee seeds), are not included in the modelling, and these are likely to have a compounding negative influence.

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