The study is the result of new findings from scientists from 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 the Julius-Maximilians-Universität Würzburg (JMU), and Carolina Ocampo-Ariza, researcher at the Agroecology Department at the University of Göttingen.

Sometimes pest, sometimes pest controller

“Animals such as birds, bats and insects, but also rodents, are important for cacao agroforestry,” Justine Vansynghel explains. On the one hand, they can increase yields, for example by pollinating the 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.

It was known that various animal species affect cacao 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 shading, can influence these contributions,” Carolina Ocampo-Ariza says. As part of their study, which has now been published, the two researchers therefore quantified the animals’ combined contributions to crop yield and explored how distance to the forest and shading affect productivity.

The key findings of their study are:

• The level

The results of an extensive five-year study conducted in Peru revealed a 50% decline in arthropod biomass following short periods of both drought and increased precipitation. One of only a few studies of this scope conducted in the tropics, the findings suggest terrestrial arthropods, a group that includes insects and spiders, will be more susceptible to climate change than previously suspected.

“Most of the time when we think about climate change, we think about warming temperatures, but rainfall patterns will change as well, which is something insects seem to be especially sensitive to,” said Felicity Newell, a postdoctoral associate and former doctoral student with the Florida Museum of Natural History. “We’re seeing that rainfall extremes can have negative effects over very short timescales.”

The insect apocalypse takes on new dimensions

The discovery of a Goldilocks preference for just the right amount of water makes its debut against a worrying backdrop of population declines. Over the last two decades, thousands of studies have documented insect decline and extinction on every continent except Antarctica, a pattern some have dubbed the insect apocalypse.

These results paint a stark but incomplete picture. Most of these studies have been conducted in densely populated temperate regions, while the planet’s most biodiverse ecosystems — the tropics — have received considerably less scrutiny.

Half of all insect diversity resides in the tropics, and as a result, scientists know a great deal about only a small fraction of imperiled insect species. This imbalance places strict limits on understanding how insects will fare with the complex problem of climate change.

“One of the biggest challenges