The citizen science Bugs Matter survey, led by conservation charities Kent Wildlife Trust and Buglife, found a 64% decline in insect numbers splatted on vehicle number plates between 2004 and 2022 across the UK.

The situation had worsened even since last year, when the survey recorded a nearly 59% drop in numbers since 2004.

Experts said it was not clear what proportion of the five percentage point drop between 2021 and 2022 was due to long-term trends or the result of record summer temperatures, but suggested climate change had a role in both issues.

The survey supports other scientific studies showing an ongoing decline in flying insects in western Europe this century.

The conservation groups said insects provided essential services, underpinning food chains, pollinating most of the world's crops and providing natural pest control and that without them, the ability of humans to survive on Earth would be under threat.

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They are in decline due to loss and damage of habitats, climate change, pollution of rivers and streams, pesticide use, and development - with growing evidence these have caused significant drops in insect numbers in the UK and worldwide, the conservationists warned.

The now-annual survey asked members of the public to record the number of flying insects squashed on their number plate, and compared it to data from an RSPB analysis in 2004 which used the same methods.

Before making an essential journey in their vehicle, drivers cleaned their number plate, recorded the route on their mobile phone, and afterwards counted the insects squashed on it using a "splatometer grid" supplied as part of the survey.

They then submitted a photo and count details via the Bugs Matter app and the data was converted into "splats per mile" to make it comparable between journeys.

The data gathered from the scheme revealed ongoing declines in insect splats in England, with a 68% reduction compared to 2004, seven percentage points worse than the 61% fall in 2021.

Wales saw a 75% decrease in bug splat numbers this summer, significantly worse than 2021's 55% fall, compared to 2004 figures.

But Scotland saw something of a reversal in the trend, with a 40% decrease when compared to 2004, better than the figures for 2021 where there was a 49% fall on 2004 numbers.

The findings were released as ministers gather in Montreal for the UN Cop15 nature summit, aimed at agreeing a deal to halt and reverse wildlife and habitat losses by 2030.

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Andrew Whitehouse, head of operations at Buglife, said: "For the second year running, Bugs Matter has shown potentially catastrophic declines in the abundance of flying insects.

"Urgent action is required to address the loss of the diversity and abundance of insect life.

"We will look to our leaders at Cop15 for decisive action to restore nature at scale - both for wildlife, and for the health and well-being of future generations."

The Bugs Matter team are now keen to develop their app further in time for the 2023 survey season. In the new changes, they are hoping to include a trial of artificial intelligence, which will automatically detect the number of splats on a number plate.