Flying bugs splatting on automobiles have declined by 60 per cent within the UK

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A survey found that between 2004 and 2021 the number of bug sprays per mile in the UK fell sharply, with the decline being particularly severe in England

Surroundings


May 5, 2022

Insects on a car number plate in the UK

David Chapman/Alamy

New evidence suggests there is some truth to anecdotes about car windshields being covered with fewer dead insects than in the past.

A UK Citizen Science survey has found that the number of flying insects sprayed on cars fell by 58.5 per cent between 2004 and 2021 after drivers counted how many were crushed on their license plates. “It’s dramatic and alarming,” says Matt Shardlow of Buglife, the charity that led the work.

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

To get a better handle on how flying insect populations were changing, Buglife had drivers wipe their license plates clean before a trip and then use a sampling grid (a “splatometer”) to count the number of dead insects when they achieved their goal and upload the results to an app. The researchers divided the number of insects by the distance traveled to come up with a “blobs per mile” unit.

This metric fell from an average of 0.238 per mile in 2004 to 0.104 per mile in 2021, a drop of 58.5 per cent across the UK. “This confirms what we already knew – that insect populations are in free fall. There seems to be no credible explanation for these results other than a massive decline in insect abundance,” says Dave Goulson of the University of Sussex, UK, who was not involved in the research.

The rate of decline is similar to that of a 2017 study that found a 76 percent decline in flying insect biomass in Germany over 27 years.

The decline found by the Buglife survey was greatest in England at 65 percent, reached 55 percent in Wales and was smallest in Scotland at 27.9 percent. Shardlow says possible explanations for the regional differences include lower light pollution, less use of insecticides due to less arable farming, and less impact of climate change further north.

A study published last month found that moth numbers in the UK more than halved between 1968 and 2016 in one of their most important habitats, the deciduous forest, although forest cover has expanded over the period. The authors said climate change could be partly to blame.

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