For years, studies have warned that a warmer planet might mean fewer cups of morning coffee — but a new study claims that rising temperatures are already taking their toll on East Africa’s coffee crops.
The study, conducted by researchers at the University of Witwatersrand in South Africa, found that Tanzania’s production of Arabica coffee — the most-consumed coffee species in the world — has fallen by 46 percent since 1966. Over the same period of time, the average nighttime temperature in Tanzania increased 1.4 degrees Celsius.
“Everybody is talking about the future,” Alessandro Craparo, a co-author of the study, told ThinkProgress. “But we can show that this has had a massive impact already.”
To understand how climate has been impacting coffee growth, Craparo and his colleagues began by looking for long-term data about coffee yields. In Tanzania, most coffee is grown by small hold farmers who don’t necessarily keep detailed records of their yields and the climate. To circumvent this, the study looked at data from three different sources: the Tanzania Coffee Board, the Tanzanian National Bureau of Statistics, and the agricultural statistics division of the Food and Agricultural Organization of the United Nations.
Using climate and yield data from those sources, the researchers analyzed the impact of climate variables on crop yield. Through statistical analysis, they found that increasing temperature had a negative effect on coffee yields — but the specific interaction between temperature and coffee growth surprised them.
“We’ve always known that high temperatures and low rainfall impact coffee,” Craparo said. “What this study found, and what’s really important, is its nighttime temperatures that are increasing at a rapid rate and having a bigger impact on coffee than what’s happening in the day.”
Arabica coffee is a sensitive plant that needs cool nights in order to thrive. For each 1-degree Celsius rise in nighttime temperatures, the researchers found, Arabica coffee yields declined by an average of 302 pounds of coffee per hectare, almost half of the typical small producer’s entire yield. If trends continue as they have in previous decade, the study says, Arabica yields in Tanzania will drop to around 320 pounds per hectare by 2060.
Coffee is Tanzania’s largest export, and Arabica beans account for about 70 percent of all coffee exported from the country, according to Reuters. Though Tanzania produces less than 1 percent of the world’s Arabica, the country’s coffee industry employs 2.4 million people and accounts for $100 million in profits each year. And even though Tanzania accounts for a relatively small percentage of world production, Craparo says that the studies findings could easily be applied to other regions growing the bean.
“It’s these increasing nighttime temperatures that are really creeping up on everybody,” he said, mentioning places like Brazil and India — both huge producers of Arabica — as potentially at risk of facing the same kinds of declines seen in Tanzania. “Have a look at these countries. Have a look at their regions. It could happen there in the future as well.”
Faced with decreasing yields, Arabica farmers and the national governments that benefit from their products will need to implement adaptation strategies to cope with warmer nighttime temperatures, Craparo said. While most governments have heavily invested in the coffee industry, few have implemented adaptation strategies to help farmers cope with changing conditions.
One immediate adaptation strategy Craparo thinks could be useful would be better management of shade on coffee farms. Shade-grown coffee helps maintain biodiversity on farms, as shading trees provide a habitat for native birds and wildlife. It also benefits the farm’s soil, helping better sequester carbon and prevent soil erosion. But choosing the right type of tree with which to shade the coffee crop is crucial, Craparo says, especially in light of the study’s findings about nighttime temperatures.
Planting the wrong kind of tree — or too many trees — might keep coffee crops shaded during the daytime, but the tree leaves can trap heat at night, artificially driving up nighttime temperatures. To combat this issue, Craparo says that farmers should consider planting trees with high canopies, which can help dissipate heat at night, and focus on pruning the trees they plant, to make sure they don’t cover the coffee crop too completely.
Farmers might also need to consider switching to a hardier species of coffee plant, such as Robusta, the second most popular coffee species in the world. Robusta doesn’t fetch the same price as Arabica — it’s considered inferior in taste and is often used for instant coffee — but it can tolerate changes in climate better than the more desirable Arabica beans.
While farmers can adapt by growing hardier varieties or managing their shade more effectively, Craparo sees the private sector as being equally responsible for finding adaptation strategies for the coffee industry — and he hopes that the study will sound the alarm for companies and countries that haven’t been paying close attention to how climate change is already affecting coffee crops.
“We have actual hard evidence of what happened,” he says of the study, adding that he hopes “it gets the private sector interested enough to do something about it.”