Flying insects splatting on cars have declined by 60 per cent in the UK

A survey finds that between 2004 and 2021 there have been huge declines in the number of insect “splats per mile” on cars in the UK, with the fall particularly bad in England

By Adam Vaughan

New evidence suggests there is some truth to anecdotes about today’s car windscreens being covered in fewer dead insects than in the past.

A UK citizen science survey has found the number of flying insects splatted on cars dropped by 58.5 per cent between 2004 and 2021, after drivers counted how many were squashed on their number plates. “It’s dramatic and alarming,” says Matt Shardlow at Buglife, the charity that led the work.

Fears have grown in recent years that, due to a loss of pollinators, some food crops could be undermined by a global decline in insects, with one recent study finding climate change and agriculture have almost halved insect numbers in the worst-hit regions. But most monitoring of flying insects is based on their distribution, rather than their abundance.

To get a better handle on how flying insect populations are changing, Buglife enlisted drivers to wipe their number plate clean before a journey and then use a sampling grid (a “splatometer”) to count the number of dead insects when they reached their destination and upload the results to an app. Dividing the number of insects by the journey’s distance, researchers arrived at a “splats per mile” unit.

This measure fell from 0.238 per mile on average in 2004 to 0.104 per mile in 2021, or a 58.5 per cent drop UK-wide. “This confirms what we already knew – that insect populations are in free fall. There seems to be no credible explanation for these findings other than a massive decline in insect abundance,” says Dave Goulson at the University of Sussex, UK, who wasn’t involved in the research.

The rate of decline is similar to that reported by a 2017 study, which found a 76 per cent drop in flying insect biomass in Germany over 27 years.

The fall found by the Buglife survey was greatest in England at 65 per cent, reached 55 per cent in Wales and was smallest in Scotland, at 27.9 per cent. Shardlow says possible explanations for the regional differences are lower light pollution, lower insecticide use due to less arable farming and a lesser impact from climate change further north.

A paper published last month found that moth numbers in the UK more than halved between 1968 and 2016 in one of their key habitats, broadleaf woodland, despite the area of woodland expanding over the period. The authors said climate change could be partly to blame.