The abundance of flying insects has plunged by three-quarters over the past 25 years, according to a new study that has shocked scientists.
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 and climate change may 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, at Radboud University in the Netherlands and 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 Prof Dave Goulson of Sussex University, UK, and 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 standardised 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% over the 27 year period, but the fall was even higher – 82% – 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% in recent decades. 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 at 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.”