One Cappuccino– Hold the Sun

Growing coffee in the shade may be the smartest way for small farmers to cope with global warming, according to research published in this month’s issue of BioScience.  University of Michigan scientists concluded that the industrial method of coffee cultivation, where swaths of forest are cut down to create large plantations, leaves the crop vulnerable to harmful fluctuations in temperature as a result of climate change. 

Brenda Lin, the leader of the Michigan team, planted coffee in shaded and sun-exposed plots at three farms in the Soconusco region of the Mexican state of Chiapas.  Her data showed that sites with low shade experience higher temperatures and lower humidity throughout an average day than a site with high shade coverage, and that higher shade sites had more consistent conditions overall.

Consistency, for coffee, is the highest of virtues. The plants, said Lin, are “very sensitive to changes within the climate, especially in South America, where there’s no irrigation; the farms are rain-fed.”  Quality beans are produced within a very narrow range of conditions- above a temperature threshold of 23 degrees Celsius, the rate of photosynthesis declines and the fruit ripens quicker, leading to inferior coffee.  Lower temperatures produce stunted plants.  Where there is the potential for large temperature and rainfall fluctuations, there is also the potential for massive crop failure.

Lin’s paper concludes that a return to the traditional practice of coffee farming, where coffee is grown underneath a canopy of shade trees, is the best way to mitigate the looming effects of global warming.  The shade-coffee movement is not a radically new idea, but Lin’s justification is.  Prior to her research, the literature on coffee growing focused on the effects of the industrial plantation system and its attendant clear-cutting on the birds of Central and South America.

“They noticed that migration patterns were changing… because the forest habitat was changing, due to the loss of the shade trees,” said Lin.  These studies noted the negative effect that coffee plantations had on biodiversity in the surrounding area.  Environmental groups began to carry the banner for replanting of shade trees, and a niche market was born soon afterwards. The Audubon Society enthusiastically promotes its own brand of shade-grown coffee through its website, touting it as “bird-friendly”.

Some farmers, more concerned with the bottom line, were not easily swayed by pleas for more stable bird migration patterns.  But Lin knew that the potential conclusions of her research could make the case that an environmentally-conscious plantation was a profitable one as well.

“I chose to look at climate change because farmers in that region had noticed the change in climate- the longer dry seasons, the El Nino years- seriously affecting their ability to produce more coffee.”  By highlighting the link between global warming and crop yields, Lin felt it would be easier to convince farmers to adopt the shade growing method “even if they didn’t care about biodiversity.”

The farmers originally practiced deforestation because it removed competition for natural resources “The idea was that less shade would equal greater yield, because you had more sun going to the plants,” says Lin.  Coupled with fears that fungal diseases, such as coffee leaf rust, would breed in the untamed lowlight, “sun coffee” caught on in the late 1970s, but really gained traction in the 1990s, when government programs in Central and South America incentivized the planting of sun coffee.  Genetic engineering has produced strains of coffee more tolerant of direct sunlight and producing, on average, more beans than its unaltered cousin, with a little help from manufactured fertilizers.  The big plantation system is able to produce a lot more coffee this way, but the smaller farmer is increasingly unable to imitate the sun coffee method.

“The rural growers on the hillsides can’t afford all the chemicals that come with implementation of intensified sun coffee, they can’t afford the fertilizers and pesticides.”  Shade-growing is easier to implement, says Lin, and better suited to local farms.  There is less coffee produced, but it is brings a higher price.  And, according to Lin’s study on shade and climate change, it may just be the soundest strategy in the long term.

Coffee, which grows as a small shrub, thrives naturally in the shade of a native canopy.  Shade-growing easily translates to similar plants, like tea and cacao.  But what about other crops like corn and wheat?  Lin is not advocating shade trees as a one-size-fits-all solution; she stresses the need for investigating a variety of sustainable agricultural practices.

One potential approach that Lin speculated upon was a return to the traditional method of crop rotation, which replenishes nutrients in the soil without the use of fertilizers, as well as “mixed plantations”, where a variety of food crops are grown in the same space.  A farmer is better able to hedge his bets growing corn, squash, and oranges together.  In mixed plantations, Lin says, “your food security isn’t necessarily tied to one crop.”

“Listen,” she says, “climate change is occurring, and that there is nothing at this point that we can do to stop it.  It’s imperative to start thinking about adaptation and coping strategies.”  The best advice for coffee growers, it seems, is to stay out of the sun.

A shade coffee plantation

Original Article: Lin, Brenda, Yvette Perfecto and John Vandermeer.  “Synergies Between Agricultural Intensification and Climate Change Could Create Surprising Vulnerabilities For Crops”.  BioScience Vol. 58, No. 9 (October 2008): 847-854.


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