• The coffee sector and climate change

    Temperature and rainfall conditions are the main drivers when it comes to yield, i.e. production. In this respect the two main species, arabica and robusta that together account for about 99% of world production, have different requirements.


    Arabica coffee evolved in the cool, shady environment of the Ethiopian highland forests where there is a single dry season coinciding with the 'winter' months. The optimum temperature range is somewhere between 15° and 24° C. Much higher temperatures tend to impact negatively on both yield and quality. Rainfall requirements are between 1500 and 2000 mm per annum although the use of irrigation today allows arabica to be grown also in areas with otherwise insufficient rainfall.

    Robusta coffee evolved across lowland Equatorial Africa, particularly in the forests of the Congo River Basin and around the Lake Victoria Crescent in Uganda. It grows best in areas with abundant rainfall of around 2,000 mm per annum, at altitudes ranging from sea level to about 800 metres. Rainfall must be well distributed throughout most of the year because the robusta tree has a relatively shallow root system. The optimum temperature ranges from 22° to 26° C and the species is less tolerant of very high as well as very low temperatures than is arabica.

    Possible effects of climate change on coffee production

    Quality. As temperature rises, coffee ripens more quickly leading to a fall in inherent quality. This statement is supported by the fact that low grown arabica from tropical areas with higher temperatures mostly shows less 'quality' in the cup compared to the same coffee grown at higher altitudes. The beans are softer and may well be larger but, lack that 'quality'. In this regard Dr Peter Baker of CAB International (www.cabi.org) estimates that if by the end of this century temperatures rise by 3° C (some experts believe an increase of up to 5° C is possible), then the lower altitude limit for growing good quality arabica may rise by some 15 ft per annum, meaning that over time areas that are currently too cold for coffee could become suitable. But it is uncertain whether land at higher altitudes would in fact become available (or be rendered suitable) for coffee production. *

    Yield. If climatic events such as overly high temperatures occur during sensitive periods of the life of the crop, for example during flowering or fruit setting, then yields will be adversely affected, particularly if accompanied by reduced rainfall.

    Pests and diseases: Higher temperatures will not only favour the proliferation of certain pests and diseases, but will also result in these spreading to regions where they were not normally present. Research suggest that the incidence of pests and diseases such as coffee berry borer, leaf miner, nematodes, coffee rust and others will increase as future temperatures rise. The consequent need for more control will make coffee production both more complicated and more expensive.

    Irrigation: Areas currently not requiring this may do so in the future due to increased evaporation that reduces the soil's moisture content. Other areas may experience increases in both rainfall and the variability thereof.

    Potential impact on global coffee production

    As already mentioned, complexity and uncertainty make it hard to be precise. Nevertheless, there is a real possibility that fewer parts of the world will be suitable for growing coffee. If so then the already evident growth in the concentration of production could become even more pronounced. This in turn could make global production more prone to high fluctuations, as any severe disruption in output from one of the major producers would drastically curtail global output. Secondly, the cost of production will increase more than would have been the case without global warming and thirdly, competition from other crops for available arable land may increase.
    In the context of this brief review perhaps the most important point to note is that current initiatives to reduce the extent of global warming are mostly aimed at limiting further warming, not to reverse it rapidly. This means everyone in the coffee value chain needs to adapt by taking actions to minimize and cope with the seemingly inevitable effects.

    * For the original presentation by Dr. Peter Baker and Dr, Jeremy Haggar entitled 'Global Warming: the impact on global coffee' go to http://www.catie.ac.cr/BancoMedios/Documentos%20PDF/cafe_gw_baker_09.pdf 

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