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Multiple interactions in its culture


Newswise – The study is the result of new findings from scientists at the universities of Würzburg, Göttingen and Vienna and the Alliance of Bioversity International and CIAT. The biologists responsible for the study are Justine Vansynghel, researcher at the Department of Animal Ecology and Tropical Biology at Julius-Maximilians-Universität Würzburg (JMU), and Carolina Ocampo-Ariza, researcher at the Department of Agroecology at the University from Göttingen.

Sometimes harmful, sometimes pest control

“Animals such as birds, bats and insects, but also rodents, are important for cocoa agroforestry,” explains Justine Vansynghel. On the one hand, they can increase yields, for example by pollinating plants or acting as “biological pest control agents”. On the other hand, they can reduce yields, for example when squirrels steal the valuable seeds and prefer to eat them themselves.

Various animal species were known to affect cocoa cultivation and crop yield. “Until now, however, it was not clear how the individual contributions of all these animals interact and how other factors, such as the proximity of the cultivated area to a forest or its level of shade, may influence these contributions,” said Carolina Ocampo- dit Ariza. In their study, which has just been published, the two researchers therefore quantified the combined contributions of animals to crop yield and explored how distance from the forest and shade affect productivity.

The main conclusions of their study are as follows:

  • The level of cocoa fruit set does not only depend on the flying insects that visit the cocoa flowers. Birds and bats also have a positive effect on fruit set
  • If birds and bats have access to cocoa plants, it more than doubles the yield.
  • Ants also contributed positively to cocoa yield, but only in farms located near forests.
  • The existence of squirrels is unpleasant from the point of view of the cocoa farmer. Because they eat the seeds of cocoa trees, they reduce crop yield. However, “the benefits of biodiversity outweigh the losses caused by squirrels and other rodents”, specify the biologists.
  • And finally: when cocoa trees grow in the shade of other plants and flying insects can visit the cocoa flowers, this also increases the fruit set and therefore – ideally – the yield.

Why does yield increase with the presence of birds and bats? The authors have a theory about this: “There might be more spiders and ants when insectivores like birds and bats are absent,” they say. If the diet of spiders and ants includes important pollinators, their absence could cause a drop in fruit set. Additionally, birds and bats could also be directly involved in pest control if they eat them themselves. However, more research is needed to confirm these theories, biologists say.

Why ants increase cocoa yields when the cultivated area is close to forests is also unclear. “Presumably, proximity to forests exerts an influence on which ant species settle in cocoa-growing areas,” Vansynghel says. This is because certain species are known to be beneficial to cocoa plants.

A new impetus for organic cocoa farming

Cocoa trees are native to South America. In this region, they grow in the undergrowth of tropical rainforests. In so-called agroforestry systems, we try to copy these conditions: there, the cocoa tree is generally planted in the shade of large trees. As part of the project, the research team studied a total of 24 such systems in northern and southern Peru. The German Society for International Cooperation (GIZ) funded the project.

According to the scientists involved, the results of the study, which has just been published, contribute to a better understanding of the processes associated with wildlife-friendly agriculture. Based on these findings, they say, it is possible to modify cultivation strategies in such a way that the existence of different animal species is not only accepted, but ideally even encouraged. After all, it could help improve the yields of organic cocoa in its region of origin.