- Birds and bats accounted for 54% of total cacao tree productivity over a one year period in northern Peru’s agroforestry systems.
- The economic benefits of bird and bat contributions in the study area amount to approximately $959 per hectare per year for Peruvian cacao farmers who grow the Blanco de Piura variety of fine-flavor cacao.
- Experimentally excluding birds and bats increased pest damage and reduced cacao yields, emphasizing their valuable “pest predation service” that benefits farmers.
- The presence of nearby forests is crucial for maintaining high cacao yields, as they support bird diversity, which helps mitigate the negative effects of ants and other pests on cacao trees.
In the arid forests of northern Peru, a rare variety of cacao tree known as blanco de Piura is cultivated by farmers and used to produce “fine-flavor” cacao (the main ingredient in chocolate). And, as it turns out, farmers in this region are getting help from some unexpected friends: birds and bats.
A new study published in the journal Ecological Applications reveals the significant role played by birds and bats in the productivity of cacao trees in irrigated agroforestry systems. Over a two-year period, these winged allies accounted for an impressive 54% of the total cacao tree productivity.
Carolina Ocampo-Ariza, a postdoctoral researcher at the University of Göttingen and lead author of the study, expressed surprise at the findings, highlighting the valuable “pest predation service” provided by birds and bats.
The economic benefits of avian and bat contributions are substantial, translating to approximately $959 per hectare per year for Peruvian cacao farmers in the study area.
All the farms used in the study are owned by small-scale farmers who are part of the Norandino Ltda. agricultural cooperative. Being part of the cooperative provides these farmers with various benefits, including selling their high-quality cacao at a premium price.
These farms use an agroforestry system which combines cacao trees with other species of shade-providing companion trees. These diverse trees attract more diversity to the farm, such as birds, bats, insects and other animals. And while there can be some costs to increased diversity, like mammals eating the fruit, this study finds that, overall, diversity benefits crop yields.
The traditional approach to cacao cultivation, which involves growing in monocultures, prioritizes short-term yield but poses problems. When cacao is grown alone, it is left vulnerable to bugs and other plant predators that a whole ecosystem would otherwise support. Additionally, cacao is adapted to thrive in the understory of forests, benefiting from the shade provided by taller trees during its early stages of growth. Monoculture plants do not have this benefit.
To figure out just how important birds and bats are in these agroforestry systems, Ocampo-Ariza and her team conducted an experiment in which they prevented birds and bats from accessing some cacao trees. They used nets surrounding the trees during the day to exclude birds, at night to exclude bats, or around the clock to exclude both. The researchers compared yields from these trees with those from the exposed trees.
The results were striking: Excluding birds and bats led to increased pest damage and reduced cacao yields. The researchers attribute this to the increased abundance of two main sap-sucking insects on cacao trees, aphids and mealybugs, which are pests known to damage the delicate white blossoms and young fruits of cacao trees.
In short, without birds and bats to eat the bugs, the bugs eat the trees.
In addition to birds and bats, the study also examined the role of ants in these cacao agroforestry systems. The researchers recorded numerous ant visitors, but most belonged to the Nylanderia genus. This genus has a mutually beneficial relationship with sap-sucking insects, feeding on their sap in exchange for protecting them from predators. Surprisingly, Nylanderia only hurt cacao yields in study sites far from native forests. The authors suggest that the presence of forests fosters high bird diversity, which helps counteract the negative effects of ants on cacao trees.
This result emphasizes the importance of nearby forests in maintaining high cacao yields. The authors stress that maintaining diverse shade trees that attract and support different birds and bats, alongside conserving nearby forests, is essential for the biocontrol services they provide.
“You can’t have cacao without forests nearby. You would lose these biocontrol services,” Ocampo-Ariza, a scientist with the Alliance of Bioversity International and the International Center for Tropical Agriculture, said. “So it makes sense to simultaneously have cacao agroforestry with diverse shade trees that attract and maintain different birds and bats and also maintain the forest nearby.”
However, Ocampo-Ariza said, getting top yields from crops is about more than putting your cacao crop right next to the forest. In a previous study, her team found that management, such as harvesting the cacao on time and managing crop diseases quickly are important parts of growing a successful crop.
“Understanding and quantifying the benefits biodiversity provides for crop production is important,” Dominic Martin, a postdoctoral researcher at the University of Bern, Switzerland, who was not involved in the study, told Mongabay. “It may help farmers to understand the value of maintaining diverse agroforestry systems, could motivate local conservation projects or increase the support for existing initiatives.”
These results have already reached decisionmakers, Ocampo-Ariza said. She and other researchers met with the Ministry of Agriculture, and the Ministry of Environment to discuss their research. Now, she said, the new plan for cacao agriculture in Peru between 2020 and 2030 considers the genetic diversity of the cacao, including native cacao varieties as well as the biodiversity present in the cacao plantations.
Peru is now the third largest producer of organic cacao in the Americas. While most of this is still grown in a monoculture, Ocampo-Ariza hopes these more biodiversity-friendly practices will continue to take hold, supporting farmers and forests as they create some of the best cacao around.
Citation:
Ocampo‐Ariza, C., Vansynghel, J., Bertleff, D., Maas, B., Schumacher, N., Ulloque‐Samatelo, C., … & Tscharntke, T. (2023). Birds and bats enhance cacao yield despite suppressing arthropod mesopredation. Ecological Applications, e2886. Doi: 10.1002/eap.2886
Vansynghel, J., Ocampo-Ariza, C., Maas, B., Martin, E. A., Thomas, E., Hanf-Dressler, T., … & Steffan-Dewenter, I. (2022). Quantifying services and disservices provided by insects and vertebrates in cacao agroforestry landscapes. Proceedings of the Royal Society B, 289(1982), 20221309. Doi: 10.1098/rspb.2022.1309
Banner image of irrigated cacao agroforests in northern Peru by Justine Vansynghel.
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