The study, published on Wednesday in peer-reviewed journal PLOS One has found that, in German nature reserves, flying insect populations have declined by more than 75% over the duration of the 27-year study.
“The flying insect community as a whole… has been decimated over the last few decades,” said the study, which was conducted by Researchers from Radboud University in the Netherlands and the Entomological Society Krefeld in Germany.
“Loss of insect diversity and abundance is expected to provoke cascading effects on food webs and to jeopardize ecosystem services.”
Entomologists have long had evidence of the decline of individual species, says Tanya Latty, a research and teaching fellow in entomology at Sydney University’s School of Life and Environmental Sciences.
However, few studies have taken such a broad view of entire insect populations, she says.
“This study lumps all flying insects together,” she says, which gives researchers a more accurate picture of the overall decline.
“If you see these sort of dramatic declines in protected areas it makes me worry that this (trend) could be everywhere,” she says.
“There’s no reason to think this isn’t happening everywhere.”
The long-term study used Malaise traps — a sophisticated kind of insect net which catches a wide variety of insects — set up in 63 German nature protection areas over the course of 27 years.
By measuring the weight of the insect catch — known as the biomass — from each of the Malaise traps, researchers were able to ascertain the drop in insect numbers.
The study reported a seasonal decline of 76%, and mid-summer decline of 82% in flying insect biomass over the 27 years of study.
“We show that this decline is apparent regardless of habitat type,” the study says.
Latty says it’s particularly worrying that the study recorded the declines in protected areas, meaning that for agricultural or urban areas the trend could be even more pronounced.
The report suggests climate change, loss of insect habitats and potentially the use of pesticides, are behind the alarming decline. Latty says it’s unlikely there’s one “smoking gun,” but rather a combination of contributing factors.