Tropical farmers are often expected to choose between high crop yields and protecting wildlife. However, an international team of researchers led by the University of Vienna, in collaboration with the universities of Göttingen and Würzburg in Germany and Bioversity International in Peru shows that biodiversity conservation reinforces cacao production in agroforests via associated ecosystem services, such as natural pest control. The new study, published in Communications Earth & Environment, provides important evidence for sustainable farm and landscape management in one of the world's most biodiverse regions.

Agroforestry is where crops grow alongside shade trees. This type of farming can protect biodiversity while supporting food production. It can also promote natural pest control, improve soils and buffer extreme temperatures. The current study investigates the precise mechanisms of successful agroforestry. "Our results show that these benefits depend strongly on how trees are managed both within farms and across the surrounding Landscape", says Pablo Aycart-Lazo from the University of Vienna, lead author of the study.

Researchers studied 28 organic cacao agroforests in the northern Peruvian Amazon. They surveyed birds, bats and arthropods and measured cacao yield, natural pest control, pollination, pest and disease incidence, soil fertility and microclimate. Drone and remote-sensing data allowed them to test how shade-tree structure within farms and tree cover in the surrounding landscape influenced these outcomes.

The structure of the canopy matters

An interesting finding: More shade was not always better. In the study, shade-tree cover benefited wildlife, soils and microclimate, but very dense shade substantially reduced cacao yields because less light reached the crop. But the researchers found a promising alternative: Farms with a more varied arrangement of tall and short shade trees supported greater biodiversity without the same yield losses. "Our data show that cacao farms do not need uniform shade to support biodiversity. A mosaic of tall and short trees, tree clusters and open patches can create habitat for wildlife while maintaining production", explains Aycart-Lazo.

What happens outside the farm may be just as important

Perhaps the most striking finding is that the surrounding landscape had a major influence on cacao productivity. Cacao yields increased from 265 kg per hectare per year in deforested landscapes to about 1,000 kg per hectare per year in landscapes combining medium levels of forest cover and additional tree crops. Birds and bats played a key role by feeding on arthropods that damage cacao flowers and pods. This nearly doubled cacao yields in these tree-rich landscapes, equivalent to an estimated US$1,640 per hectare per year in additional production value. "Birds and bats can be powerful allies for cacao farmers, but only if the surrounding landscape provides enough habitat. If these landscapes become large monocultures, much of this natural pest-control benefit is lost", says senior author Bea Maas, from the University of Vienna.

The message is simple: sustainable cacao is not just about what happens inside the farm. It is also about the landscape around it. The authors advocate for a landscape-level strategy. In a contiguous region the researchers recommend maintaining 30–35% forest cover, together with another 40–45% of tree-based habitats such as agroforests or orchards and an additional 20–30% of open areas like annual crops. This could create multifunctional landscapes with high biodiversity while supporting cacao production and farmer livelihoods. "This is not a one-size-fits-all blueprint. Landscape strategies need to be adapted to local land availability and developed together with local communities", adds co-senior author Carolina Ocampo-Ariza, from the Technische Universität Darmstadt and the University of Göttingen, Germany.

Summary:

• Reconciling food production and biodiversity conservation in the tropics requires socio-ecologically viable farming systems.
• More shade can support biodiversity in cacao agroforests, but very dense shade reduces yields.
• On the other hand, structural diversity of shade trees can increase biodiversity without the same yield penalty.
• Maintaining forests and other tree-based habitats in the surrounding landscape supports birds, bats, natural pest control and cacao production
• Sustainable cacao production thus requires integrating local and landscape management to achieve win-win scenarios for biodiversity and farmers.

About the University of Vienna:

For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected. With degree programmes covering 188 disciplines, and approximately 11,000 employees, we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.

This research was part of the research project ECO-CACAO, funded by the Austrian Science Fund (FWF grant number I5272) and the German Research Foundation (DFG grant number TS 45/42-1, STE 957/27-1).