Ecosystem services in cacao agroforestry: predation by birds, bats and ants on spiders and insect herbivores
Final Report Abstract
The project disentangled important aspects of trophic relationships within cacao agroecosystems in Indonesia. Food webs links at different levels of land-use intensity, as well as the consequences for ecosystem services such as pest control and productivity were studied. Two approaches were used. First, exclusion of birds, bats and/or ants from cacao trees in fifteen plantations covering gradients in distance to forest and shade tree cover was conducted to find out the prey of these organisms, and the cacao trees depend on the predatory pressure of these groups. Secondly, ants and their food items were collected for stable isotope analyses which can be used to reveal the relative contribution of plant-based and animal-based food resources changes in space across different plantations, and in time as cacao goes through the harvest cycle. Day and nighttime exclosures of birds and bats did not only enhance the abundance of phytophagous insects, ants and spiders but also caused an economically significant reduction in crop yield, consistently across local and landscape gradients. The exclusion of birds and bats had contrasting effects on different herbivore and predator arthropod groups, suggesting complementary prey choice. Mesopredator release was observed but did not translate into lower herbivore loads nor higher herbivory or crop losses, but may have offset the impact of herbivore load on herbivory, which did not differ between treatments. Preliminary results for the ant experiment suggest that the ant exclusion further reduced yields. Sample collection for stable isotope analyses are complete and analyses are ongoing. Major new insights into the trophic interactions and its consequences across environmental gradients have been gained, and ongoing analyses will be completed with other source of funding shortly. Our results demonstrate the importance of ecosystem services for human welfare and translates the direct and indirect of predation on arthropods by birds and bats to gains in plant productivigty corresponding to an economical value of 730 USD per one ha and year.
Publications
- (2011) Multifunctional shade-tree management in tropical agroforestry landscapes – a review. Journal of Applied Ecology 48:619-629
Tscharntke T, Clough Y, Bhagwat SA, Buchori D, Faust H, Hertel D, Juhrbandt J, Kessler M, Perfecto I, Scherber C, Schroth, G, Veldkamp E, Wanger TC
- (2012) A generalized approach to modeling and estimating indirect effects in ecology. Ecology 93:1809–1815
Clough Y
(See online at https://doi.org/10.1890/11-1899.1) - (03/2013) “3rd International Bat Meeting: Bats in the Anthropocene” (Berlin, Germany). Title: Bats in South East Asian agroforestry contribute more to cacao pest control than birds
Bea Maas
- (04/2013) “Annual Conference of the Society for Tropical Ecology” (gtö in Vienna, Austria). Title: Birds and bats sustain productivity in agroforests of Central Sulawesi, Indonesia
Bea Maas
- (2013) Non-linear effects of pesticide application on biodiversity-driven ecosystem services and disservices in a cacao agroecosystem: a modeling study. Basic and Applied Ecology 14:115-125
Sabatier R, Meyer K, Wiegand K, Clough Y
(See online at https://doi.org/10.1016/j.baae.2012.12.006)
