Shady Endeavor Could Help Combat Coffee Rust

Coffee farmers—and birds—could benefit from a shift toward shade-grown crops, researchers say.

There's trouble brewing for coffee. By now, you've probably heard about coffee rust, or roya—the fungal disease that's devastated Latin American coffee farms to the tune of 1 billion dollars. Fearing price hikes and crop reductions of up to 40%, baristas everywhere are quaking in their aprons, and the livelihoods of 500,000-odd coffee-industry workers may be in jeopardy.

To combat the epidemic, everyone from the Obama administration to Starbucks is pouring funds into the development of disease-resistant plants. But some ecologists say there might be a better plan of attack—one that benefits migratory birds: Raise more shade-grown coffee.

The scientists worry that current solutions, such as fungicide application and developing resistant plants, focus too much on coffee alone—not on the health of the entire ecosystem.

"Those narrow approaches tend to work in the very short term; they're not part of a more sustainable approach to the management of coffee," said Ivette Perfecto, an ecologist at the University of Michigan. Perfecto and her colleagues advocate a return to shade-grown practices, which promote a healthy web of interactions that, ideally, would naturally keep coffee rust in check.

Hemileia vastatrix, the fungus that causes coffee rust, attacks the leaves of affected plants by coating them in an orangey powder that prevents photosynthesis. It is not a new disease. In fact, Brits have the fungus to thank for their world-renowned tea habit: When rust began sweeping through Ceylon's coffee plantations in the 1800's, infected coffee trees were replaced with tea bushes. The fungus reached Brazil in 1970, and there have been periodic outbreaks in Central and South America, the world capital of arabica coffee, ever since.

But the outbreak that began in 2012 is the worst the region has ever faced. Climate has been blamed in part, but a shift away from shade-grown coffee could also be responsible, a team of scientists including Perfecto reported in BioScience earlier this year.

Traditional shade-grown coffee farms preserve the existing canopy layers of the forest. In addition to fostering biodiversity and maintaining complex ecological relationships between plants, fungi, insects, and bats, shade-grown coffee provides critical winter habitat for migratory bird species like scarlet tanagers, Baltimore orioles, buntings, and a variety of warblers.

But sun-grown farms have their own appeal: they can produce higher yields and bring in more money. This approach has taken off in recent years; a study published in April found that the proportion of land dedicated to shade-grown coffee has declined almost 20% since 1996. That switch may have unintentionally exacerbated the spread of the fungus and the scope of the problem.

On sun-grown coffee farms, the plants are spaced very close together, making it easier for coffee rust to spread from one to the next. Fungal spores travel unimpeded in the open air surrounding the farms. The heavy use of fungicide to combat rust also kills beneficial species like white halo fungus, which naturally attacks the coffee rust fungus.

The Michigan researchers suspect that the breakdown of biodiversity in coffee farming has contributed to the coffee rust epidemic, worsening its impact on sun and shade-grown plantations alike. While cultivating plants that are resistant to the fungus is certainly a positive step, it represents only one piece of what should be a multi-pronged solution.

"We need a more ecological approach," Perfecto said. We'll drink (a cup of coffee) to that.

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