A project asking people to count squashed bugs on their car number plates suggests flying insects have declined by more than 75% in Scotland over the past two decades.

The citizen science survey led by Kent Wildlife Trust and Buglife showed a 78% decline in "bug splats" on number plates across the UK since 2004.

The conservationists warned the dramatic falls in flying insects were a "red flag" for the state of nature in the UK which should not be ignored.

The Bugs Matter survey is based on the windscreen phenomenon - anecdotal evidence from drivers that they collect fewer moths, flies, aphids, bees and flying beetles on their windscreens than they did in the past.

The conservation groups said insects pollinate crops, provide natural pest control, decompose waste, recycle nutrients and underpin food chains, and without them Earth's ecological systems would collapse.

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

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

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Since the original survey in 2004, records from nearly 26,500 journeys across the UK have been analysed.

To take part in the scheme, drivers cleaned their number plate before making an essential journey, 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.

Some 6,637 journeys were made in 2023, and the results showed England had the sharpest fall of 83% between 2004 and 2023, with the highest drop recorded in London, where there was a 91% reduction.

The Herald: An insect, unsplatteredAn insect, unsplattered (Image: Kent Wildlife Trust)

Wales saw a 79% decrease and Scotland a 76% drop over the same period, while Northern Ireland - which has limited data - saw a 54% decline between 2021 and 2023, the results revealed.

Dr Lawrence Ball, from Kent Wildlife Trust, said: "These results are extremely concerning, particularly if insect splats serve as an accurate measure of insect populations.

"This is a red flag for the state of nature in the UK that shouldn't be ignored.

"A decrease in the number of insects sampled of more than 75% in less than two decades is really alarming, and we're seeing fewer insects being sampled every year."

Andrew Whitehouse, from Buglife, said: "The latest Bugs Matter data suggests that the abundance of flying insects in our countryside has dramatically fallen.

"The consequences are potentially far-reaching, not only impacting the health of the natural world, but affecting so many of the free services that nature provides for us."

He said the findings were similar to studies which had documented declines in insect numbers around the world.

Mr Whitehouse added: "Human activities continue to have a huge impact on nature - habitat loss and damage, pesticide use, pollution, and climate change all contribute to the decline in insects.

"Society must heed the warning signs of ecological collapse, and take urgent action to restore nature."