Birds boost coffee yields

Intensive agriculture often leaves forests in tatters. But preserving patches of those natural habitats could end up saving farmers money. According to a new study, forest birds improve coffee yields by eating destructive pests.

Coffee is one of the world’s most valuable crops, worth about $90 billion per year. It is threatened by the coffee berry borer, an insect that can destroy more than three-quarters of a harvest and quickly becomes resistant to pesticides. Borer-eating birds, however, offer a potential natural control strategy.

The study authors set up experiments at two coffee plantations in Costa Rica. First, they built barriers of bamboo and mesh net around some coffee shrubs, which allowed insects but not birds to pass through. Other shrubs were left exposed to both insects and birds. Over two seasons, the team counted the number of the coffee berries infested by borers.

Coffee shrubs that were blocked from birds had roughly twice the percentage of infested berries as those open to birds, the researchers report in Ecology Letters. Borers also tunnelled deeper into the berries when birds were absent. The authors estimate that birds save the plantations about $75 to $310 per hectare each year.

The researchers also tested the contents of 469 fecal samples from birds. Five species, including rufous-breasted wrens and yellow warblers, had eaten the bugs.

Surveys of six coffee plantations suggested that areas with sparser forests had more borers. “[O]ur results show that adjusting agricultural practices to conserve countryside forest elements, and associated biodiversity, may limit losses from the most damaging pest of one of the world’s most economically important crops,” the authors conclude. Roberta Kwok | 5 September 2013

Source: Karp, D.S. et al. 2013. Forest bolsters bird abundance, pest control and coffee yield. Ecology Letters doi: 10.1111/ele.12173.

Image © Iryna1 | Shutterstock