Your next pour-over may be Liberica or excelsa- Newstheusanewshubs

Image of a cappuccino's foam.

Diana Gitig

Coffee is uniquely vulnerable to climate change. It grows in tropical regions, where temperatures and rainfall are becoming increasingly erratic; it is grown by small farms, which do not have the resources available to weather the coming literal and figurative storms; and despite the fact that coffee is among the most highly traded commodities in the world, little agricultural research time or money has been devoted to it.

Right now, just two species of coffee are grown commercially: Arabica and robusta. Droughts over the past couple of years have reduced coffee yield, even as demand is exploding. Something must be done. Tea plantations are facing similar problems, so switching to tea won’t help. (Molecular coffee might eventually be an option, though.)

But researchers in the UK and Uganda posit that coffee farms can adapt in a number of ways. They can move, they can change their practices, or they can plant different varieties of coffee. These researchers vote for option three. And they have a candidate: Liberica coffee.

Liberica is indigenous across much of Central and West Africa and was planted in Sri Lanka and Southeast Asia in the late 19th century when Arabica plants were succumbing to coffee leaf rust (which they still succumb to). Liberica has lots of features that endear it to growers, like large fruit that stays on the tree once ripe rather than falling to the ground. These features make it easier to harvest. Alas, its tough skin also makes it more difficult to process and properly dry the coffee beans. Staying on the tree can also mean the fruit starts to ferment before it’s harvested, so the coffee it makes tastes like dreck.

The large-fruited Liberica plants that were disseminated throughout the coffee-growing world in the 1870’s are actually not that common in the wild, though. Other varieties of Liberica, notably excelsa, were discovered in the early 1900s. Excelsa has some of the benefits of the previously used and abandoned Liberica variety, but its fruits are smaller and easier to pulp.

And the coffee it makes is good. Tasting notes of a recent Ugandan crop “include cocoa nibs, peanut butter, dried fruits, Demerra sugar, and maple syrup.” That grown in South Sudan had “notes of raspberry coulis, figs, plums, and milk chocolate.” It has comparable caffeine levels to Arabica, so can be an appropriate substitute as growing conditions for Arabica continue to decline. And since Liberica is already widely cultivated across the coffee-growing world, hopefully the excelsa variety will thrive in those regions, too.

Nature Plants, 2022.  DOI:  10.1038/s41477-022-01309-5

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