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These areas will have to diversify their food
sources, by importing their crop of choice from
other areas or grow alternative food crops that
are more suited to the modified climate.
For coffee farmers, diversification is far
more complex.
Growers of coffee are dependent upon the
crop for an income, not just for subsistence
living as many farmers of food crops are in
developing nations. Coffee plants take several
years to mature, so farmers must wait until
their investment starts to payback. Given the
time to reach maturity, growers are unable
to switch between crops on an annual basis.
Coffee farming is usually the main activity for
many families throughout large regions that are
capable of producing, so if the harvest fails or
is poor, an entire community and their
associated dependents are affected.
Establishing insightful information to determine
which coffee producing regions are most
threatened by future climatic changes is critical,
so that communities can begin to plan, diversify
and mitigate the risk posed by a changing
climate. To begin to investigate these issues our
project explored the past and future suitability
of arabica coffee in eight East African countries.
Threat of climate change
Like all crops, a bountiful coffee harvest is
dependent to a great extent upon climatic
conditions. Arabica coffee is a climatically
sensitive plant: it requires temperatures that
are not too hot, not too cold, perfectly timed
precipitation and no frost. Without these exact
conditions, yields fall, quality declines and
disease amongst plants can become endemic.
Over the next century, climate scientists
predict that global temperatures will rise, that
precipitation will become increasingly erratic,
and that extreme events such as floods and
droughts will become more commonplace.
Such changes in our weather systems will
affect agricultural productivity and the
Intergovernmental Panel on Climate Change
(IPCC) has identified that agriculture-based
industries will be amongst the most affected
by future climatic changes. Indeed, several
studies have addressed the risk posed by
climatic change on stable food crop yields in
key producer regions, and in some areas it
is predicted that the yields of wheat, maize,
rice and millet may be negatively affected by
predicted changes in temperature and rainfall.
Over the past 40 years the mean annual
temperature in East Africa has risen by 1.2°C
and annual precipitation has declined by
150mm. During the same period of time,
the total area of land cultivated with arabica
coffee has fallen. Using annual climate data,
we established a model to identify locations
within the eight East African countries that
were climatically suitable for arabica coffee.
To distinguish between regions that were
very suitable and had near perfect climatic
conditions for coffee production and areas that
were within the physiological limits of arabica
coffee plant development, but were not ideal,
we established two different classifications of
suitable locations – those that were climatically
‘optimal’ and areas that would be climatically
‘tolerable’. We found that the number of
optimal and tolerable coffee growing locations
had declined during the past 40 years, which
suggests that changes in climate have already
begun to affect coffee producers.
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