Press release: Which creatures mean more cacao in the field?
No. 124 - 14.09.2022
Research team led by the Universities of Göttingen and Würzburg highlights importance of critical animal species
Without insects, there would be no cacao - a much-desired raw material for the food industry. Insects ensure that the flowers are pollinated and that the cacao fruits develop. In addition, birds and bats contribute significantly to increasing the crop yield. Researchers from the Universities of Würzburg, Göttingen and Vienna, the Alliance of Bioversity International and CIAT, have studied this in north-western Peru. The results were published in the Proceedings of the Royal Society B.
"Animals such as birds, bats and insects, and even rodents, are important for cacao agroforestry," explains Justine Vansynghel, a PhD student at the Department of Animal Ecology and Tropical Biology at the University of Würzburg. On the one hand, they can increase yields, for example by pollinating the plants or acting as biological pest control. On the other hand, they can reduce yields, for example when squirrels eat the cacao seeds themselves.
"Until now, it hasn’t been clear how the contributions of individual animal species to cacao production interact with one another, and how other factors, for example the proximity to the forest or its level of shading, influence the yield," says Carolina Ocampo-Ariza from Agroecology at Göttingen University. In their study, the two ecologists therefore quantified the combined contributions of the animals to the crop yield.
The key findings of the team were that the amount of cacao harvested depends not only on the flying insects that pollinate, but also significantly on the presence of many birds and bats. If birds and bats do not have access to the cacao trees, the yield is halved. Ants also contribute to the cacao yield, but only on farms near forests. Squirrels, on the other hand, eat the seeds, and thus reduce the yield.
"Looking at the big picture, birds, bats and insects produce far greater biodiversity benefits than the losses caused by squirrels and other rodents," says Professor Teja Tscharntke, Head of the Department of Agroecology at Göttingen University. "When cacao trees grow together with shade trees, this also increases the proportion of flowers that form fruit, as well as the yield."
Why does the yield increase when there are birds and bats? Vansynghel explains: "Birds and bats could be involved in controlling pests directly, but this is an assumption that needs to be supported by further research." Why ants increase cacao yields when the cultivation area is close to a forest is also not clear. "Presumably, more predatory ant species colonise the cacao trees near the forest," says Vansynghel.
The results of the study contribute to a better understanding of the importance of wild vertebrates and invertebrates for cacao production. "The results demonstrate the great importance of pollinators and insect-eating birds and bats for the yield of smallholder farmers. They illustrate how important it is for organic cacao production to support the services of these species," Ocampo-Ariza emphasises.
Original publication:Justine Vansynghel, Carolina Ocampo-Ariza, et al.: Quantifying services and disservices provided by insects and vertebrates in cacao agroforestry landscapes. Proceedings of the Royal Society B. https://doi.org/10.1098/rspb.2022.1309
Contact
Carolina Ocampo-Ariza
University of Göttingen
Faculty of Agricultural Sciences - Agroecology
Grisebachstraße 6, 37077 Göttingen, Germany
Email: carolinamaria.ocampoariza@uni-goettingen.de
www.uni-goettingen.de/de/74726.html
Justine Vansynghel
Biocentre
University of Würzburg