Image: Dina Roberts

With Central and South America's forests disappearing at an alarming rate, conservation-conscious java consumers across the country have tried to do their part by turning to coffee grown in the shade. Unlike the higher-yield method of growing coffee plants in full sun, shade-coffee production is generally believed to be environmentally friendly because it can sustain indigenous tropical creatures, birds in particular. According to a report in the October issue of the journal Ecological Applications, however, the process isn't entirely green.

A team led by University of Georgia researcher Dina L. Roberts spent two years studying the birds that live in the vicinity of western Panama's coffee plantations and forests. They focused on the mixed-species parties of birds that follow swarm raids of army ants (such as the one shown right), which flush out more desirable insects from the leaf litter. By assessing these ant-bird interactions in intact forest, shade-coffee plantations near forests, shade-coffee plantations far from forest, and open-sun coffee areas, the scientists were able to observe how varying levels of environmental disturbance affect different bird species.

Roberts and her colleagues found that all shade-coffee and forested areas supported numerous bird species, in contrast to the open-sun areas, which did not have any ant swarms and, therefore, no ant-following birds. Yet they also noted the absence of many forest-dwelling birds in the shade-coffee areas that were distant from continuous forests. The reasons for this, the researchers propose, may be that many species have nesting practices that make them vulnerable in disturbed habitats, or that the vision adaptations that certain species have evolved in response to the dim forest light might leave them less inclined to fly through sunny regions to reach the shade-coffee patches. "With increasing distance from large areas of continuous forest, Roberts notes, "the value of traditional shade-coffee habitats is lessened for certain components of the bird community."

Thus, the investigators conclude, although the shade-growing approach is clearly superior to its full-sun counterpart, its value does appear to be limited. "Shade-coffee plantations provide a critical habitat for army ants and the associated biodiversity," Roberts remarks, "but shade-coffee alone should not be considered a panacea for conservation efforts to protect sensitive forest species."