Do you know that high night temperatures affect our morning coffee?
Evidence that climate change is already having an impact on the Arabica coffee sector in the East African Highlands region is shown by a study called “Coffea arabica yields decline in Tanzania due to climate change: Global implications” published earlier this month by IITA, the International Center for Tropical Agriculture, and the University of Witwatersrand in www.sciencedirect.com. The study shows that over the last 49 years, there has been a +1.42 °C increase in night temperatures which has led to yield decreases in Arabica of 195 kg/ha. The consequences for smallholders in the region are dramatic as it represents losses of 46%.
“Coffee yields have declined to their lowest point in years, with many farmers in Tanzania giving up on coffee completely,” says Alessandro Craparo, the main author of the study.
The sensitive Coffea arabica berries need low temperatures to grow well and produce high quality coffee for consumption, that is why they are best suited to the cool tropical highlands of East Africa, typically between 1300-2800 m above sea level. Using data from the northern Tanzanian highlands, the study demonstrates for the first time that the increasing night time (minimum) temperature is the most significant climatic variable responsible for diminishing Arabica coffee yields between 1961 and 2012 and proves that climate change is an ongoing reality. The researchers A. Craparo, P. van Asten, P. Läderach, L. Jassogne, and S. Grab use open access datasets, which confirm that out of many climate variables, night temperature has the greatest correlation to coffee production.
The results of the study projected forward means that without substantial adaptation strategies, the average coffee production in Tanzania will drop to 145 ± 41 kg/ha by 2060. This is approximately a 35% loss in yield for the farmer, which could mean a decrease of up to US$28 million in export earnings for Arabica for the country.
“The industry is aware of the impact of climate change on coffee production, but they need hard data to prove to regional decision makers, how urgently climate mitigation strategies need to be put in place” says Dr Piet van Asten, IITA Country Representative in Uganda and agronomist working on sustainable intensification of cropping systems. “The study is the first of its kind globally providing essential time-series evidence that climate change has already had a negative impact on C. arabica yields,” he added.
Contrary to the typical constraints found in coffee research linked to rainfall and drought stress and the climate projections for future scenarios deriving from it, the observation of minimum temperatures needed for coffee growing leads to clear empiric data and biological relationships–the hotter the nights get, the higher the danger for Arabica coffee production.
At night temperatures of 23 °C and above, the plant’s metabolism starts to change, leading to lower yields and reduced quality, which will have a significant impact on the coffee industries and processors.
The study, which was done under the CGIAR Research Program on Climate, Agriculture and Food Security also received funding from the German Federal Ministry of Economic Cooperation and Development, BMZ . It may give the coffee sector the hard figures required to encourage the public and the private sector to invest in climate change adaptation strategies that will better sustain the industry and the livelihoods of millions of smallholder farmers who depend on it.