Vanilla cultivation in Madagascar provides small farmers with a good income, but without trees and shrubs, the plantations lack biodiversity. Agroecologists from the University of Göttingen, in collaboration with colleagues from the University of Antananarivo (Madagascar), have investigated the interaction between prey and their predators in these growing areas. To do this, they released dummy prey experimentally to determine the activity of natural enemies. The result: the more trees there were, the more prey was attacked. This pest control is beneficial for agricultural cultivation. The results of the study were published in the Journal of Applied Ecology.
Vanilla is the main crop in northwestern Madagascar and is sometimes grown alongside shade trees in agroforestry systems. The researchers distributed standardized plasticine models of caterpillars in different habitats such as forests, fallow land, vanilla plantations and rice paddies. By analyzing the bite marks, they were able to determine the predators' attention to these dummy "herbivores", i.e. how many predators attacked the prey.
The team showed that predator attention was highest in both rainforest and forest fragments, but decreased as there were fewer trees in the area. Even comparing landscapes, less dense forest areas had lost a large proportion of their predators. Ants and locusts also played a much larger role as predators than birds or other vertebrates, although the community in the forest was markedly different from the community in the cultivated fields. This also applied to vanilla plantations planted directly under the canopy of natural forests.
Dominik Schwab, who achieved these results as part of his master's thesis, emphasizes: "If rich vegetation with numerous trees is promoted or restored in the vanilla plantations, this can contribute to nature conservation outside the forests and also promote much better pest control." Co-author and PhD student Annemarie Wurz adds: "Such measures would not reduce yield, as studies in coffee and cocoa agroforestry have shown." Professor Teja Tscharntke, Head of Agroecology at the University of Göttingen and co-author of the study, says: "The study not only focuses on diversity, but also on an important ecological function of the species involved. In doing so, it supports the line of the United Nations, which advocates for the Decade of Ecosystem Restoration from 2021 to 2030."
The cultivation of vanilla under trees is therefore not only beneficial for pest control, but also contributes to nature conservation and the preservation of biodiversity. The study shows how important it is to find the right balance between agricultural production and environmental protection. By encouraging rich vegetation in vanilla plantations, small farmers can maintain their yields while helping to restore ecosystems and protect biodiversity.
Future research could focus on identifying the best methods for integrating trees and shrubs into vanilla orchards and figuring out how to most effectively encourage pests' natural enemies. In this way, farmers could benefit from improved pest control and at the same time make a contribution to environmental protection.
Overall, this study shows that more sustainable agriculture is possible by using natural solutions and taking advantage of agroforestry systems. This approach can help maintain smallholder yields while protecting the environment and promoting biodiversity.