Have Scientists Seen Any Effects of Climate Change on Coffee Crops?

Ask a Scientist - November 2011

M. Day, of Boston, MA asks: “I've heard that some food crops are particularly vulnerable to global warming. Have scientists seen any effects on coffee crops around the world?” She is answered by Dr. Brenda Ekwurzel, Assistant Director of Climate Research and Analysis.

Right now climate change is threatening highly valued Arabica coffee bean crops in major coffee-producing regions of the world. These premium coffee supplies have shrunk dramatically in recent years as a result of higher temperatures, long droughts punctuated by intense rainfall, as well as more persistent pests—all of which are associated with climate change.

Let’s look at some specifics. 

Many economic factors can influence the price of the popular Arabica coffee bean which is grown in East and Central Africa, Latin America, India, and Indonesia. These can already be felt at the grocery store, as big coffee brands like Maxwell House and Folgers have increased retail prices for many grinds by 25 percent or more in the past year alone.

But how is this linked to climate change? You can see the answer clearly in a place like Costa Rica. This Central American nation began exporting coffee in the 1830s, and coffee has played a central role in the nation’s history and economic development ever since. In 2008, coffee was Costa Rica’s third-largest export, valued at more than $300 million annually. Since 2000, however, warming temperatures, a growing number of extreme rainfall events, and volatility in world coffee prices have contributed to a 44 percent plunge in Costa Rican coffee production.

Scientists know that average temperatures in Costa Rica have been rising over the past century. They also know that the Arabica coffee plant’s preferred temperature range is fairly narrow: between 64 and 71° F (18 to 22° C). Both yield and quality decline above that range. Above 93° F (34° C), little photosynthesis takes place within the coffee plant. In Costa Rica, since the 1970s, however, the number of warm days has risen about 2.5 percent per decade. Arabica coffee plants are also highly sensitive to intense rainfall. Scientists know that extreme rainfall events have become more common in Costa Rica, and have been accounting for more of the nation’s total rainfall since the 1960s.

Another devastating factor is that warmer temperatures foster the expansion of the range of one of the most destructive coffee pests in the world: the coffee berry borer. These beetles bore into coffee berries to lay their eggs. The hatched larvae feed on the berry seeds, reducing the yield and quality of the crops. Before 2000, the coffee berry borer was not present in Costa Rica. But, over the past decade as temperatures have risen, pest has come to infest a growing proportion of the nation’s coffee plantations.

Because temperature and incorrect timing and amount of rainfall can affect Arabica coffee plants directly, by making growing conditions less optimal, and indirectly, by enabling the success of pests such as the coffee berry borer, coffee-growing regions throughout the world are particularly susceptible to the changes in climate that are now underway. In Ethiopia, for example, Arabica coffee yields declined by nearly 35 percent from 2002 to 2009 because of rising temperatures and widespread coffee berry borer infestations. In India, between 2002 and 2011, Arabica coffee production declined by nearly 30 percent primarily due to intense rains.

With human-induced emissions of heat-trapping gases still rising, scientists project that global temperatures will continue to increase over the course of this century. If we commit to a concerted effort to lower our carbon emissions, we can still forestall some of the worst effects of global warming. To do that, of course, we need to “wake up” and better understand the changes that are occurring now—to coffee production and the planet’s climate.   

Dr. Brenda Ekwurzel is a climate scientist who leads UCS's climate science education work aimed at strengthening support for sound U.S. climate policies. She holds a Ph.D. in isotope geochemistry from the Department of Earth Sciences at Columbia University's Lamont-Doherty Earth Observatory and has studied climate variability in places as disparate as the Arctic Ocean and the desert Southwest.

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