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Robusta coffee more sensitive to climate change than previously thought

From the June 2020 issue.

A new study of the plant that produces Robusta coffee suggests its heat tolerance has been consistently overestimated. Worse yet, when temperatures slightly cross this point, yields plummet.

Scientists from the Alliance of Bioversity International and CIAT, the University of Southern Queensland (USQ), and ECOM Agroindustrial, conducted the research on farms in Vietnam and Indonesia, which supply about half the world's Robusta beans.

The study, published in Global Change Biology, was built on 10 years of yield observations on almost 800 farms across Southeast Asia. The analysis suggests that the optimal temperature range for Robusta is 20.5°C, which is markedly lower than the temperatures currently considered optimal. For every 1°C increase over this new optimal range, yields decrease by 14 per cent.

"Our results suggest that Robusta coffee is far more sensitive to temperature than previously thought," says the authors. "Its production potential could decline considerably as temperatures increase under climate change, jeopardising a multibillion-dollar coffee industry and the livelihoods of millions of farmers."

The study's findings contrast with current estimates, based on historical botanical explorations in Central Africa, that had suggested Robusta had a higher temperature tolerance.

"This should make us reassess the viability of some of our current options, like switching from Arabica to Robusta coffee as the climate warms to adapt production to climate change," says Jarrod Kath, the study's lead author from USQ.

Arabica coffee, which is generally preferred for its superior taste, is even more sensitive to temperature change. Coffee farmers at lower altitudes around the tropics have been switching out their Arabica trees for Robusta trees, while Arabica farmers have been searching for higher altitudes and lower temperatures to maintain production.

"These findings provide baseline information for coffee farmers, private sector investors, and governments to adapt their coffee production plans under climate change," says Alessandro Craparo, a co-author with the Alliance.

The researchers says this highlights the importance of testing assumptions about agricultural production sensitivity to climate variability with large field-based datasets.

"Precipitation changes have long been a concern of the coffee industry," said co-author Laurent Bossolasco of ECOM. "Now it's clear that we need more in-depth analysis of temperature variations in the Robusta region."

Image: Laurent Bossolasco

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