By Leila Al-Hamoodah, data analyst in aWhere
Coffee is a critical cash crop in Uganda, and the country is one of the largest producers in the world. Coffee alone accounts for between 20 and 30 percent of foreign exchange earnings and employs an estimated 3.5 million workers. The production for coffee is spread across Uganda, with both Arabica and Robusta varieties in cultivation.
Unfortunately, coffee production faces significant risks from climate change, due to increasing average temperatures and changes in precipitation patterns. These changes are expected to impact not only the areas in which coffee is suitable for growth, but also the incidence of pests and diseases that threaten yields. Academics, environmental and industry groups have assessed the risks and impacts of climate change on coffee in Uganda. aWhere’s comprehensive weather database allows for our own investigation of the Uganda coffee sector and how weather may be impacting production.
Coffee production is highly dependent on suitable conditions for ideal growth. The plant can tolerate average annual temperatures up to 25°C, however, continuous exposure to temperatures at or above 30°C can cause significant damage to the crop, including stunted growth, yellowed leaves (see below), and stem tumors.  In addition, pests and diseases also pose an increasingly significant threat to coffee production as the climate changes and temperatures rise.

aWhere’s data was used to investigate observed weather in the coffee growing regions of Uganda in 2016, to identify any potentially damaging impacts that may be associated with climate change.   We found that 2016 was a highly irregular year, with high temperatures spread across the coffee-growing regions of the country, with possible implications for coffee production.
When comparing 2016 to long term norms, the year frequently exhibited high maximum and minimum temperatures.  As coffee is susceptible to high temperatures, consecutive days reaching or exceeding 30°C were flagged as potentially damaging. Of the 296 9km2 grids observed in this review, 96% experienced temperatures of at least 30°C for at least 7 days in 2016. Meanwhile, 41% of these grids experienced 30°C temperatures for one full month or longer.

These persistent high temperatures are concerning, as an extended period of extreme temperatures may cause irreversible damage to the seasonal crop, even if the rest of the season has ideal conditions.
To assess the abnormality of these temperatures and to be able to differentiate between high temperatures and extreme temperatures, we looked at the standard deviations.  When averaged together, the coffee growing regions in Uganda experienced daily maximum temperatures that were 2 or more standard deviations from the norm on 32 days in 2016.  On most of these occasions, the temperatures significantly exceeded the norms.  Meanwhile, minimum temperatures exceeded the norms by 2 or more standard deviations on 77 days in 2016.  This evidence suggests that not only was 2016 hotter than the previous decade in coffee growing areas, but that this temperature differential was significant and abnormal.

Coffee growing areas that experienced 30 or more consecutive days of 30°C+ temperatures in 2016

2016 temperature extremes
The weather conditions observed here could indicate serious trouble for Ugandan coffee production, with temperatures outside the ideal growth range and warmer temperatures encouraging the spread of pests and diseases. Uganda faces many challenges with regard to coffee production in the face of climate change, and farmers are left hoping that 2016 was an abnormality and not a sign of even warmer weather to come.