Birds are providing a valuable ecosystem service on coffee plantations in Costa Rica, finds a new study that quantifies the pest control benefits of preserving tree cover in agricultural areas.
The study, published in the journal Ecology Letters, looked at the impact of the coffee berry borer beetle (Hypothenemus hampeii) on coffee yields. The beetle is the only insect that directly consumes coffee berries, making it a major scourge for coffee farmers around the world, costing producers some $500 million a year.
The pest’s recent arrival in Costa Rica provided an ideal opportunity to explore how coffee yields may be influenced by the presence of borer beetle predators, like birds and bats. The researchers, led by Daniel Karp of Stanford University, also wanted to understand whether maintaining tree cover in plantations helps reduce crop losses by boosting beetle predators.
After measuring coffee yields, Karp and colleagues set up a classical exclusion experiment. They found that birds, not bats, were the main borer beetle predator.
“Pest infestation doubled in absence of birds,” Karp said during a presentation at the June meeting of the Association for Tropical Biology (ATBC) in Costa Rica. “There were no effects with bats.”
The yellow warbler (Setophaga petechia) is a pest-eating bird that frequents coffee plantations. Photo by Daniel Karp
Among birds, there were five species that had the biggest effect on controlling the coffee borer. These species were more abundant on farms that maintained forest cover. In other words, more forest meant more birds and less coffee berry borer beetles.
“Borer infestations are less severe on more forested farms,” said Karp. “As forest cover increases, the number of berries saved increases.”
The researchers used that data to determine that birds increase yields $75-310 per hectare on an annual basis. So far a typical farm, maintaining small stands of forest could be worth $10,000 per year. The amount compares favorably to the $6,500 the average Costa Rican earns in a year.
Shade grown coffee in Costa Rica
Overall the researchers found the greatest post control came from having a number of small forest fragments — smaller than one hectare.
“This is some of the first evidence to show that rainforests offer pest control service,” said Karp.
“This work suggests that it might be economically advantageous to not farm in certain areas of a plantation,” Karp said in a Stanford press release. “We’re going to start trying to generalize these results so that farmers, conservationists, land managers and governments can use them anywhere to make simple estimates of what they might gain in pest protection by protecting certain patches of the landscape.”
CITATION: Daniel S. Karp, Chase D. Mendenhall, Randi Figueroa Sandí, Nicolas Chaumont, Paul R. Ehrlich, Elizabeth A. Hadly, Gretchen C. Daily. Forest bolsters bird abundance, pest control and coffee yield,’ Ecology Letters (doi: 10.1111/ele.12173)