An unusual decline of caterpillars and their parasites has been recorded in the area of Selva in Costa Rica from a study in Scientific Reports conducted by researchers at the University of Nevada. Using 22-year-old data, the researchers found a very marked decline in the diversity and density of caterpillars and their parasitoids.

Both animals provide, according to the researchers themselves who published a statement on the university’s own website, an “important ecosystem service, focusing in particular on “biocontrol of herbivores.” The Selva area is located in Costa Rica and is basically a dense forest, relatively isolated, surrounded by cultivated fields, mainly banana, pineapple and palm fields that provide an important economic contribution to the region.

This area, as well as other nearby isolated areas, provides important parasitoid populations which in turn control the pest populations in the surrounding plantations. Reducing these caterpillar pests also means increasing plant parasitoids and this compromises the health of the forest ecosystem as well as the cultivated fields.

According to the researchers, more than 40% of the 64 kinds of caterpillars found in this area have disappeared. Along with the caterpillars, these parasites have also disappeared. According to the researchers, these significant decreases are due to the increased variability of precipitation and shifts in average, maximum and minimum temperatures, mainly due to ongoing climate change.

“Caterpillar-pesticide interactions are intimately linked and depend on narrow windows for synchronous development. Subtle shifts in host and parasitoid population cycles due to variable delay effects can have important consequences for these highly specialized and synchronized interactions,” says Danielle Salcido, lead author of the study.