There have been alarming declines this year in some insect species including bees, butterflies, moths and wasps, while many seabirds have also been “hammered” by unstable weather patterns caused by the climate emergency, a conservation charity has said.

In its annual report on the impact of the weather on flora and fauna, the National Trust highlights that numbers of bees and butterflies have “crashed” in some areas of the UK in 2024.

It describes the apparent decline of birds such as the globally threatened Arctic tern as “very shocking” and mentions diseases that are striking the white-clawed crayfish and sycamores.

There have been some bright spots, including a new breeding grey seal colony on the east coast of England, and the charity also recorded encouraging numbers of owls and other birds of prey, but overall the picture is grim.

The trust’s head of nature conservation and restoration ecology, Ben McCarthy, said the lurch from drier conditions since the summer of 2022 and through much of 2023 to a very wet and mild 2024 – bookended by fierce storms – had had a “devastating impact”.

“The unpredictability of the weather and blurring of the seasons is adding additional stresses to our struggling wildlife,” he said. “The overall trends are alarming.”

The trust said insects had had “a very poor year” with numbers widely observed below normal, particularly during the first half of the summer as a result of the cool and wet weather.

The gardens at Barrington Court in Somerset were almost bereft of butterflies until late August or the start of September. Species such as the adonis blue crashed in west Dorset, where only 92 were recorded this year in one area that is regularly monitored, compared with 552 in 2023.

Butterfly numbers at the Giant’s Causeway in Northern Ireland were half of their typical level, while at the Wicken Fen national nature reserve in Cambridgeshire the total in its traditional peak week was the lowest in 15 years of recording.

Not only insects were affected. There were no natterjack toadlets at Formby, compared with 60 last year. Bat numbers in roosts including Ennerdale in the Lake District were also down, most likely the result of fewer insects to feed on.

Ground-nesting waders including avocet, lapwing and redshank had a poor breeding season on the east coast of England as a result of the weather, which also affected the curlew population on the Ysbyty Ifan estate in north Wales, where nine chicks did not survive their first two weeks after hatching because of exposure or starvation.

In late September, around 70 white-clawed crayfish died in the River Wansbeck catchment, which runs through the Wallington estate in Northumberland. The UK’s only native freshwater crayfish has struggled to survive since the increase in numbers and range of the invasive signal crayfish. The cause of the deaths is so far unknown.

Cryptostroma corticale or sooty bark disease has started to affect sycamore trees weakened by drought in 2022 in the east of the country. The fungus infects the main living tissue of the tree. Sixty have so far been felled on National Trust land.

Terns suffered big losses on the Farne Islands, with numbers of common, sandwich and Arctic tern down by 70%, 66% and 51% respectively. They are the lowest numbers in modern history, with bird flu suspected to be a key factor.

Sophia Jackson, an area ranger, said: “The plummet in numbers is very shocking, especially because they have recently been added to the International Union for Conservation of Nature red list.”

McCarthy said: “Our seabirds have also been hammered in recent years by a mix of climate change impacts, poor weather and bird flu.”

There were some winners. Rangers at Orford Ness national nature reserve in Suffolk announced the establishment of Suffolk’s first grey seal colony. Seals have now bred there for three consecutive years and more than 130 pups were born there last winter.

It has also been a decent year for raptors, with five breeding pairs of little owls recorded at Sherborne Park estate in Gloucestershire. There was good news too for Cornwall’s chough population, which grew by more than 100 for the second year running.

The trust highlighted examples where its conservation and restoration work had encouraging results, including the appearance of the UK’s smallest dragonfly – the black darter – in newly-created pools at Great Gnats Head on Dartmoor in Devon.

Its climate change adviser, Keith Jones, said: “As the world continues to get hotter, this trend hides a world of extremes – both deluge and drought and shifting patterns. The reality is now playing out in real time, impacting landscapes, nature and the places we look after.”

The fabric of some National Trust properties also had a difficult year. Storm Henk caused flooding at Avebury manor in Wiltshire for the first time in three centuries at the start of the year, and Storm Darragh brought down 30 “significant trees” at Bodnant Garden in north Wales including a “monster” Greek fir – Abies cephalonica – planted about 130 years ago.