Global warming is bad news for coffee lovers

It may get harder to find that perfect espresso in our globally warmer future. @bberwyn photo.

Study shows how coffee plants suffer even during short heatwaves

Staff report

Heatwaves are becoming more common in a world warmed by heat-trapping greenhouse gas pollution, and at some point in the not-too-distant future, that could spell bad news for your morning cup of wake-me-up.

Scientists with Oregon State University’s College of Forestry have 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 to drink.

C. arabica is the globe’s dominant coffee-plant species, accounting for 65 percent of the commercial production of the nearly 20 billion pounds of coffee consumed globally each year. The plants grow in 80 countries in four continents in the tropics.

The research used artificial warming in greenhouses to study how leaf age and the length of heatwaves affected C. arabica’s recovery from heat stress. 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 heat waves produced any flowers or fruit.

“This emphasizes 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.

The scientists exposed the coffee plants to conditions that produced leaf temperatures of a little more than 120 degrees Fahrenheit, for either 45 or 90 minutes — a realistic temperature for what’s expected in an ever-hotter world. They assessed the response by measuring the plants’ photosynthetic activity, finding that the developing leaves took longer to recover. Regardless of leaf age, the longer heat treatment resulted in decreased water-use efficiency, which could also worsen the effects of heat stress, particularly during drought.

The findings were recently published in Ecology and Evolution. The National Science Foundation supported the study, co-authors of which were Frederick Meinzer of the U.S. Forest Service and Christopher Still of the OSU Department of Forest Ecosystems and Society.

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