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"gewg_" writes:
The Center for American Progress reports

For years, studies have warned that a warmer planet might mean fewer cups of morning coffee--but a new study claims that rising temperatures are already taking their toll on East Africa's coffee crops.

The study, conducted by researchers at the University of Witwatersrand in South Africa, found that Tanzania's production of Arabica coffee--the most-consumed coffee species in the world--has fallen by 46 percent since 1966. Over the same period of time, the average nighttime temperature in Tanzania increased 1.4 degrees Celsius.

[...]The researchers analyzed the impact of climate variables on crop yield. Through statistical analysis, they found that increasing temperature had a negative effect on coffee yields --- but the specific interaction between temperature and coffee growth surprised them.

"We've always known that high temperatures and low rainfall impact coffee," [Alessandro Craparo, a co-author of the study] said. "What this study found, and what's really important, is its nighttime temperatures that are increasing at a rapid rate and having a bigger impact on coffee than what's happening in the day."

Arabica coffee is a sensitive plant that needs cool nights in order to thrive. For each 1-degree Celsius rise in nighttime temperatures, the researchers found, Arabica coffee yields declined by an average of 302 pounds of coffee per hectare, almost half of the typical small producer's entire yield. If trends continue as they have in previous decade, the study says, Arabica yields in Tanzania will drop to around 320 pounds per hectare by 2060.