Two scientific studies of the number of insects splattered by cars have revealed a huge decline in abundance at European sites in two decades.
The research adds to growing evidence of what some scientists have called an “insect apocalypse”, which is threatening a collapse in the natural world that sustains humans and all life on Earth. A third study shows plummeting numbers of aquatic insects in streams.
The survey of insects hitting car windscreens in rural Denmark used data collected every summer from 1997 to 2017 and found an 80% decline in abundance. It also found a parallel decline in the number of swallows and martins, birds that live on insects.
The second survey, in the UK county of Kent in 2019, examined splats in a grid placed over car registration plates, known as a “splatometer”. This revealed 50% fewer impacts than in 2004. The research included vintage cars up to 70 years old to see if their less aerodynamic shape meant they killed more bugs, but it found that modern cars actually hit slightly more insects.
“This difference we found is critically important, because it mirrors the patterns of decline which are being reported widely elsewhere, and insects are absolutely fundamental to food webs and the existence of life on Earth,” said Paul Tinsley-Marshall from Kent Wildlife Trust. “It’s pretty horrendous.”
The Danish research, published in the journal Ecology and Evolution, used data from an average of 65 car journeys a year on the same stretch of road and at the same speed between 1997 and 2017. Møller took account of the time of day, temperature, wind speed and date of the journey and found an 80% decline in insect abundance over the 21-year period. Checks using insect nets and sticky traps showed the same trend.
Møller said the causes were likely to be “a bit of everything”, but noted significant changes due to global heating. “In my 50 years, the temperature in April, May and June has increased by 1.5C [2.7F] on average in my study area,” he said. “The amount of rain has increased by 50%. We are talking about dramatic differences.”
The stream research, published in the journal Conservation Biology, analysed weekly data from 1969 to 2010 on a stream in a German nature reserve, where the only major human impact is climate change.
“Overall, water temperature increased by 1.88C and discharge patterns changed significantly. These changes were accompanied by an 81.6% decline in insect abundance,” the scientists reported. “Our results indicate that climate change has already altered [wildlife] communities severely, even in protected areas.”