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Insects are an integral part of life on Earth as both pollinators and prey for other wildlife, and it was known that some species such as butterflies were declining, but the newly revealed scale of the losses to all insects has prompted warnings that the world is “on course for ecological Armageddon,” with profound impacts on human society. The new data was gathered in nature reserves across Germany, but has implications for all landscapes dominated by agriculture, the researchers said. The cause of the huge decline is as yet unclear, although the destruction of wild areas and widespread use of pesticides are the most likely factors, while climate change might also play a role.
The scientists were able to rule out weather and changes to landscape in the reserves as causes, but data on pesticide levels has not been collected. “The fact that the number of flying insects is decreasing at such a high rate in such a large area is an alarming discovery,” said Hans de Kroon of Radboud University in the Netherlands, who led the new research. “Insects make up about two-thirds of all life on Earth, [but] there has been some kind of horrific decline,” said Dave Goulson of Sussex University in England, part of the team behind the new study. “We appear to be making vast tracts of land inhospitable to most forms of life and are currently on course for ecological Armageddon. If we lose the insects then everything is going to collapse.” The research, published in the journal Plos One, is based on the work of dozens of amateur entomologists across Germany who began using strictly standardized ways of collecting insects in 1989. Special tents called malaise traps were used to capture more than 1,500 samples of all flying insects at 63 different nature reserves.
When the total weight of the insects in each sample was measured a startling decline was revealed. The annual average fell by 76 percent over the 27-year period, but the fall was even higher — 82 percent — in summer, when insect numbers reach their peak. Previous reports of insect declines have been limited to particular insects, such European grassland butterflies, which have fallen by 50 percent, but the new research captured all flying insects, including wasps and flies which are rarely studied, making it a much stronger indicator of decline. The fact that the samples were taken in protected areas makes the findings even more worrying, said Caspar Hallmann of Radboud University, also part of the research team. “All these areas are protected and most of them are well-managed nature reserves, yet this dramatic decline has occurred,” Hallmann said.
The amateur entomologists also collected detailed weather measurements and recorded changes to the landscape or plant species in the reserves, but this could not explain the loss of the insects. “The weather might explain many of the fluctuations within the season and between the years, but it doesn’t explain the rapid downward trend,” said Martin Sorg of the Krefeld Entomological Society in Germany, who led the amateur entomologists. Goulson said a likely explanation could be that the flying insects perish when they leave the nature reserves.
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