"It's not just one species, it seems there's basically a kind of wholesale collapse of wild insects," says Dave Goulson, a co-author of a study published in the online journal PLoS ONE on Wednesday.

The study did not pinpoint a reason for the precipitous drop, but Goulson notes that many nature preserves are surrounded by agricultural lands.

"I think it's likely [that] it's how the surrounding land is being managed, because the nature reserves themselves haven't really changed, but the surrounding landscape is full of these big monoculture crops treated with lots of insecticides," says Goulson, a biology professor at the University of Sussex in Brighton, UK. "We've turned a huge proportion of the surface of the world into a fairly bleak and inhospitable place for life other than the crop."