When hot coffee means no coffee

Hot coffee is great in your cup, but heat is not a good thing for coffee crops, research at Oregon State University suggests.

A study by OSU’s College of Forestry showed that when Coffea arabica plants were subjected to short-duration heat waves, they became unable to produce flowers and fruit. That means no coffee beans — and no coffee.

As the globe’s dominant coffee-plant species, C. arabica accounts for 65% of the commercial production of the nearly 9 billion kilograms of coffee consumed globally each year.

Continually producing new flushes of leaves year-round, C. arabica grows in 80 countries across four continents in the tropics.

The OSU research investigated how leaf age and heat duration affected C. arabica’s recovery from heat stress during greenhouse testing. A major finding was that the younger, ‘expanding’ leaves were particularly slow to recover compared to mature leaves, and that none of the plants that endured the simulated heatwaves produced any flowers or fruit.

“This emphasises how sensitive Coffea arabica is to temperature,” said lead author Danielle Marias, a plant physiologist with OSU’s Department of Forest Ecosystems and Society. “No flowering means no reproduction, which means no beans, and that could be devastating for a coffee farmer facing crop failure.

“Heat is very stressful to the plants and is often associated with drought. However, in regions where coffee is grown, it may not just be hotter and drier, it could be hotter and wetter, so in this research we wanted to isolate the effects of heat.”

Results of the research were recently published in Ecology and Evolution.