Would you like a tree with your coffee? That may not sound like a good idea, but a new study suggests that mixing trees with coffee bushes could boost bird populations while improving crop yields. Among the chief threats bean growers face is the coffee berry borer (Hypothenemus hampei), an insect that lays its eggs after digging into coffee berries. Recent studies in Jamaica’s “high mountain” coffee farms suggest that introducing insect-eating warblers such as the black-throated blue warbler (Setophaga caerulescens, inset, about to snag a coffee berry borer) onto plantations can keep the pests in check. But sustaining a population of the birds on a farm is a challenge; because of borers’ small size and seasonal population changes, they make up only about 10% of warblers’ diets. To see whether adding additional bird habitat in the form of trees and shrubs (background, above) might make a difference, biologists created a series of computer simulations of the ecosystem in and around a coffee farm. Replacing about 5% of the coffee-growing area with trees randomly dispersed about the farm supported a threefold increase in the number of birds living there, the team reports online today in the Proceedings of the National Academy of Sciences. That increase cut the coffee berry borer infestation rates from about 35% to less than 15%, bringing with it a slight increase in coffee yields despite the reduced growing area. If the simulations hold in the real world, taking your coffee with a dash of shrubbery might be a good choice after all.

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