Sustainable agriculture relies on biodiversity to provide important ecosystem services, such as pollination and pest control. However, some animals provide disservices by damaging crops or reducing yields. Quantifying the relative benefits and losses due to different animal groups is key to assessing potential management trade-offs and interactions in sustainable agroecosystems. Despite the importance of cacao for cosmetics, drinks, and (of course!) chocolate, little is known about the quantitative impacts of biodiversity on ecosystem services and disservices in cacao agroforestry systems.
An international group of researchers led by Justine Vansynghel—researcher at the Julius-Maximilians-University in Würzburg, Germany—and Carolina Ocampo-Ariza—researcher at the Georg-August-Universität in Göttingen, Germany—addresses this knowledge gap in their recent publication in Proceedings of the Royal Society B, “Quantifying services and disservices provided by insects and vertebrates in cacao agroforestry landscapes.” The goal of the study was to quantify multiple ecosystem services and disservices in cacao agroforests by establishing exclusion experiments to prevent certain animal groups from accessing cacao trees and measuring the resulting effects on fruit set, marketable yield, and fruit loss. The authors focused on the impacts of birds, bats, squirrels, flying insects, and ants.
In addition to evaluating the effect of animals on cacao productivity, the research team also assessed the impact of shade cover provided by non-cacao trees in the agroforests and the distance to other forests. The study was conducted in 12 organic cacao agroforests in northwestern Peru.
Results indicate that birds, bats, and flying insects supported cacao yield by enhancing cacao fruit set and marketable yield. Allowing flying insects as well as birds and bats to access cacao trees and flowers increased fruit set. In particular, fruit set services provided by flying insects were strongest in cacao agroforests with an intermediate level of canopy shade cover.
However, the study also revealed that ants and squirrels were associated with important disservices. Interestingly, while yield increased in cacao agroforests that were near other forests when ants were present, ants also caused a little over 9 kg/ha of fruit loss annually. Squirrels, on the other hand, only caused disservices. Through fruit predation, squirrels reduced mature fruit harvesting by an average of 10%. Despite these trade-offs, the annual yield benefits provided by birds and bats, close to 180 kg/ha, and flying insects, roughly 270 kg/ha, outweighed the yield losses caused by ants and squirrels.
Overall, the authors underscore the importance of accounting for both ecosystem services and disservices when developing management strategies in cacao agroforests. To increase the benefits provided by biodiversity, the authors offer some recommendations. Because ants were only associated with beneficial yield services in cacao agroforests close to other forests, the authors emphasize the importance of protecting or restoring forest patches located within a few hundred meters of cacao agroforests. They also note that maintaining intermediate levels of canopy shade cover is important for flying insect populations that are critical to cacao fruit set. This study provides an important first step in elucidating the complex biodiversity interactions in cacao agroforests.
Learn more about the team’s research in English and German.
Original Publication: J Vansynghel et al. 2022. Quantifying services and disservices provided by insects and vertebrates in cacao agroforestry landscapes. Proc. R. Soc. B 20221309. https://doi.org/10.1098/rspb.2022.1309
