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Green Coffee Growing Practices Buffer Climate Change Impacts
ScienceDaily (Oct. 10, 2008) Chalk up another environmental benefit for shade-grown
Latin American coffee: University of Michigan researchers say the technique will
provide a buffer against the ravages of climate change in the coming decades.
Over the last three decades, many Latin American coffee farmers have abandoned traditional
shade-growing techniques, in which the plants are grown beneath a diverse canopy
of trees. In an effort to increase production, much of the acreage has been converted
to "sun coffee," which involves thinning or removing the canopy.
Shade-grown farms boost biodiversity by providing a haven for birds and other animals.
They also require far less synthetic fertilizer, pesticides and herbicides than sun-coffee
plantations.
In the October edition of the journal BioScience, three U-M researchers say shade-growing
also shields coffee plants during extreme weather events, such as droughts and severe
storms. Climate models predict that extreme weather events will become increasingly
common in the coming decades, as the levels of heat-trapping carbon dioxide gas continue
to mount.
The U-M scientists warn Latin American farmers of the risks tied to "coffee-intensification
programs"---a package of technologies that includes the thinning of canopies and
the use of high-yield coffee strains that grow best in direct sunlight---and urge
them to consider the greener alternative: shade-grown coffee.
"This is a warning against the continuation of this trend toward more intensive systems,"
said Ivette Perfecto of the U-M School of Natural Resources and Environment, one
of the authors. "Shaded coffee is ideal because it will buffer the system from climate
change while protecting biodiversity."
Perfecto has studied biodiversity in Latin American coffee plantations for 20 years.
The lead author of the BioScience paper is Brenda Lin, whose 2006 U-M doctoral dissertation
examined microclimate variability under different shade conditions at Mexican coffee
plantations.
Lin is currently a Science and Technology Policy Fellow with the American Association
for the Advancement of Science in Washington, D.C. The other author of the BioScience
paper is John Vandermeer of the U-M Department of Ecology and Evolutionary Biology.
The livelihoods of more than 100 million people worldwide are tied to coffee production.
In Latin America, most coffee farms lack irrigation---relying solely on rainwater---which
makes them especially vulnerable to drought and heat waves.
Shade trees help dampen the effects of drought and heat waves by maintaining a cool,
moist microclimate beneath the canopy. The optimal temperature range for growing
common Arabica coffee is 64 to 70 degrees Fahrenheit.
Lin's work in southern Mexico showed that shady farms have greater water availability
than sunny farms, due in part to lower evaporation rates from the coffee plants and
soils. More shade also reduced peak temperatures between 10 a.m. and 2 p.m., when
southern Mexican coffee plants experience the greatest heat stress.
"These two trends---increasing agricultural intensification and the trend toward
more frequent extreme-weather events---will work in concert to increase farmer vulnerability,"
Lin said. "We should take advantage of the services the ecosystems naturally provide,
and use them to protect farmers' livelihoods."
The study was funded by the National Security Education Program's David L. Boren
Fellowship, the Lindbergh Foundation and the National Science Foundation.
Shade trees also act as windbreaks during storms and help reduce runoff and erosion.
