Coffee Is Under Threat: How Scientists Are Fighting to Save It from Extinction

“A mathematician is a machine for turning coffee into theorems”, a quote often attributed to the late Hungarian mathematician Paul Erdős. Coffee is one of the world’s favorite drinks and an essential stimulant for many researchers. But its future is uncertain. “Coffee is critically threatened by climate change,” says Kassahun Tesfaye, a plant geneticist at Addis Ababa University.

Nearly all the 10 million tonnes of coffee beans consumed annually around the world come from two plant species: the strong and often bitter robusta (Coffea canephora) and the more delicate-tasting arabica (Coffea arabica). Unfortunately, arabica suffers or dies when temperatures rise just a few degrees, and robusta requires massive amounts of water and its yields drop drastically in a drought. Researchers are racing to keep the world’s coffee drinkers awake – and preserve the livelihoods of the many lower-income-country farmers who grow the cash crop.

The Birthplace of Arabica and Genetic Diversity in Ethiopia

Ethiopians are proud of their country for being the homeland of arabica coffee. The Ethiopian government has been establishing conservation areas to preserve the natural genetic diversity of the species. It also grows more than 12,000 arabica plants in living collections at the Ethiopian Biodiversity Institute in Addis Ababa and at the Ethiopian Institute of Agricultural Research in Jimma. The government is betting that these plants will provide the material for breeding – or genetically engineering – arabica cultivars with traits designed to withstand high temperatures and drought.

Wild Coffee Species: Liberica, Excelsa, and Stenophylla

As temperatures increase, arabica cultivation might need to move to increasingly higher terrain to stay cool, which will not be easy for owners of small coffee plantations. Another solution is to grow other species of coffee plant that can better withstand climate change. There are 134 known wild coffee species, and a few are being grown for their climate resilience, including C. liberica and C. excelsa.

Aaron Davis, a researcher at the Royal Botanic Gardens, Kew, says “the success stories are always about changing the species” that farmers grow. In wet regions, that could mean switching from arabica to robusta, but in other places it could instead mean growing C. liberica, which tolerates higher temperatures than arabica does and does not require as much water.

Davis has also tried a “bonkers” coffee species, Coffea stenophylla, which was described by a Swedish botanist in West Africa in the 18th century and then largely forgotten by science. “It still freaks me out, because here we have a coffee which isn’t related to arabica, occurs in an extreme environment – and yet tastes like a very specific arabica from Rwanda.” The challenge, he says, will be to breed varieties of C. stenophylla that are productive and that farmers find easy to grow.

Chemistry Tricks: Grinding Frozen Beans and Improving Extraction

Some researchers are looking for ways to get more out of the shrinking arabica supply. Christopher Hendon, a materials scientist at the University of Oregon, says: “There’s a lot you can do at the consuming side.” Hendon and his collaborators have found that grinding coffee beans at below freezing temperatures results in smaller particles. However, counter-intuitively, they also found that finer grinds do not necessarily yield tastier brews. Smaller particles tend to aggregate through electrostatic forces, reducing the surface area exposed to water – and thus the amount of chemicals entering solution – but tweaks to the grinding techniques, such as starting with moist beans, can help reduce the clumping.

Somewhat surprisingly, coarser grinds can also release more of the good stuff into an espresso, but this happens only when beans are put under pressures as low as 7 atmospheres. (A typical coffee-house machine works at around 10 atmospheres.)

Chemistry: The Key to Coffee’s Future

Chemistry is also crucial to investigating alternative coffee plants and how to turn them into desirable products. Hendon says the science of coffee is still young, and researchers are working to develop reproducible and objective techniques. “Compositional measurement is a big challenge,” says Hendon, “and so is assigning a numerical value to flavor.” A typical cup of coffee might contain more than 2,000 organic compounds, and their concentrations vary greatly depending on how and where the plant is grown – and how the beans are roasted.

Tesfaye emphasizes that scientists, of all people, should care about coffee’s future, not just because science is good for coffee, but because coffee is good for science, too. “Many discoveries and knowledge are generated after having a cup of coffee.”

Frequently Asked Questions About Coffee’s Future Under Climate Change