Coffee farms could benefit birds while lowering pests

Coffee is the second most valuable traded commodity worldwide, and tiny beetles called coffee berry borers are some of the world’s most economically damaging insect pests. Gravid females can lay up to 120 eggs in a single berry. But drilling into the berries could take several hours, making these dark beetles easy pickings for insectivorous birds. If coffee growers want more pest control help from the birds, however, they need more trees.

There are many ecological benefits to shade grown coffee, but crop yields are lower than coffee grown in full sun. So researchers from Humboldt State University built on field studies in Jamaican coffee croplands and designed a computer simulation to find the right blend of trees, birds, and coffee. Simulated birds got to forage in five habitat types: intact forest, trees (which range from individual trees to forest fragments), shade coffee with at least 50 percent cover, sun coffee with less than 25 percent cover, and unsuitable habitat such as roads.

As the team increased the area of the “trees” habitat in the model from 0 to 20 percent of the landscape, bird density increased fivefold. For coffee yield, the sweet spot was at 5 percent tree coverage, at which point infestation rates decreased by 60 percent. That means that the production loss — incurred by replacing 5 percent of sun coffee cropland with patches of trees — was offset by the higher beetle consumption, thanks to the larger bird population. And that’s an eye-opening conclusion.  Janet Fang | 10 April 2014

Source: Railsback, S.F. & Johnson, M.D. Effects of land use on bird populations and pest control services on coffee farms, Proceedings of the National Academy of Sciences (2014). doi/10.1073/pnas.1320957111

Image: baimaple | shutterstock.com

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