A decade of mild winters and “pulses” of bad weather has caused a decline of butterflies and bees, the National Trust said.
The unsettled weather is impacting on many species because of the detrimental effects it has on small plants and wildflowers which are relied upon by insects for food.
The Trust’s nature and wildlife specialist Matthew Oates said the UK has not had a good summer for wildlife since 2006, with the mixed weather conditions over the past 12 months continuing the trend.
A mild winter, cold spring and a wet May and June meant a bumper year for grass growth which farmers have capitalised on by making more hay and silage, but the same weather has squeezed out smaller plants and flowers, the Trust said.
The unsettled weather in November brought a brief cold snap and four inches of snow to the Yorkshire Dales. At Hudswell Woods, near Richmond, the snow “came as a surprise to the wood”, said ranger Seb Mankelow, as many of the trees were still in leaf.
At the Trust-owned Lytes Cary in Somerset, 85 per cent fewer bumblebees were recorded this year as grass outgrew wildflowers in field margins, and meadow butterflies struggled on Purbeck, Dorset where marbled white numbers dipped by 73 per cent and sightings of common blue butterflies fell by 23 per cent.
It has been a poor year for field voles, the Trust said, and without them barn owls do not breed well. No barn owl broods were recorded at Malham in the Yorkshire Dales this year.
Wasp numbers have crashed too and the decline could impact on the food chain because of wasps’ role of eating pests and providing food for other species, the Trust warned.
Mr Oates said: “In the 10 years we’ve been reviewing wildlife at our places we’ve noticed pulses of unsettled weather become the norm.
“When you do get good weather during the brighter months of the year, it’s almost inevitably short-lived and finished with something nasty.
“During the brightest months, we do seem to be getting more extreme weather events, most of which aren’t nice.”
To offset the impact of the weather, Mr Oates said conservationists and farmers must work together and wildlife-friendly farming payments should not be lost post-Brexit.