ATBC Online Web Program

Birds and bats increase crop yield in tropical agroforestry landscapes

Monday, 24 June 2013: 14:50
La Paz - B East (Herradura San Jose)
Bea Maas , Agroecology, Goettingen University, Germany
Yann Clough , Agroecology, Georg August University Goettingen, Germany
Teja Tscharntke , Agroecology, Georg-August University Göttingen, Germany
Human welfare is significantly linked to ecosystem services such as the suppression of pest insects by birds and bats. Negative impacts of land-use change on predators can affect insect communities and plant productivity, but biocontrol services are still largely unquantified. Here, we analyze the impact of birds and bats on arthropods and crop yield in cacao in Indonesia. In an exclosure experiment on 15 cacao plantations, we manipulated the access of birds and bats on cacao trees (day, night and full exclosures, open control). We investigated, for the first time, the effect of predator exclosures on the abundance of arthropods on the cacao trees (phytophagous insects, aphids, predatory ants and spiders), fruit development and crop yield for 15 months. Unlike previous studies, we investigated the contingency of the effects on local and landscape scales (shade tree cover and forest-distance gradients). As expected, arthropod densities, depending on their main feeding preferences and activity period, significantly increased in the exclosures. We found that fruit development was negatively affected in all exclosure treatments, with the full exclosure of birds and bats decreasing crop yield by more than 30%. These dramatic yield effects were consistent across local and landscape changes. Our results highlight the tremendous economic impact of birds and bats for cacao agroforestry. The consistency over the plantations investigated suggest that common bird and bat species of the agricultural landscape provide substantial ecosystem services and should be an essential part of a sustainable use of natural resources and agricultural land in this highly dynamic region.