Butterflies are “failing to cope” with climate change and the pollution of the British countryside, experts have warned after a disastrous year saw population declines in 40 out of 57 species.
The UK Butterfly Monitoring Survey found it had been the fourth-worst year overall with six species – the heath fritillary, grizzled skipper, wall, grayling, white-letter hairstreak and white admiral – all suffering their most dramatic declines in the 41 years since records began.
Sixteen species saw increases with one remaining about the same, the annual survey found.
But Professor Tom Brereton, head of monitoring at Butterfly Conservation, said the results showed that the insects were in trouble.
“Worryingly, not even the pleasant summer weather of 2016 was enough to help butterflies bounce back from a run of poor years,” he said.
“The results show that butterflies are failing to cope with our changing climate and how we manage the environment.
“As butterflies are regarded as good indicators of environmental health this is hugely concerning for both wildlife and people.”
A mild winter is thought to have been the beginning of their troubles.
Research has suggested this leads to an increase in diseases and predation and a disruption of their over-wintering behaviour.
This was followed by a cold spring, which caused further problems as it can delay their emergence into the winged stage of their life, leading to shorter lifespans.
Some of the declines in population numbers found by the survey before were jaw-dropping.
The gatekeeper was down 48 per cent on the year before, while other similarly widespread species like the meadow brown and wall butterfly (both down 31 per cent) also struggled.
The white admiral, white-letter hairstreak and grayling numbers also fell by 59 per cent, 42 per cent and 27 per cent respectively.
The heath fritillary, now found in just a few sites in southern England, fell by 27 per cent between 2015 and 2016, raising fears for its long-term future in the UK. Its numbers have fallen by 82 per cent in the last 10 years.
Dr Marc Botham, butterfly ecologist at the Centre for Ecology & Hydrology, which was also involved in the survey, said: “The weather at critical times of species development can cause dramatic changes in population numbers in the short term.
“What is of greatest concern is the regularity with which these short-term changes in recent years are negative, resulting in significant long-term declines for many species.
“Furthermore, this is becoming more and more commonplace for many of our most widespread and abundant species equating to large reductions in overall butterfly numbers with knock-on effects to their ecosystems.”
Animals in decline
Animals in decline
1/8 Harbour seal (Phoca vitulina)
Where: Orkney Islands. What: Between 2001-2006, numbers in Orkney declined by 40 per cent. Why: epidemics of the phocine distemper virus are thought to have caused major declines, but the killing of seals in the Moray Firth to protect salmon farms may have an impact.
2/8 African lion (Panthera leo)
Where: Ghana. What: In Ghana’s Mole National Park, lion numbers have declined by more than 90 per cent in 40 years. Why: local conflicts are thought to have contributed to the slaughter of lions and are a worrying example of the status of the animal in Western and Central Africa.
3/8 Leatherback turtle (Dermochelys coriacea)
Where: Indonesia, Malaysia, Mexico, Costa Rica. What: Numbers are down in both the Atlantic and Pacific. It declined by 95 per cent between 1989-2002 in Costa Rica. Why: mainly due to them being caught as bycatch, but they’ve also been affected by local developments.
4/8 Wandering albatross (Diomedea exulans)
Where: South Atlantic. What: A rapid decline. One population, from Bird Island, South Georgia, declined by 50 per cent between 1972-2010, according to the British Antarctic Survey. Why: being caught in various commercial longline fisheries.
5/8 Saiga Antelope (Saiga tatarica)
Where: Kazakhstan, Mongolia, Russia, Turkmenistan, Uzbekistan. What: fall in populations has been dramatic. In the early 1990s numbers were over a million, but are now estimated to be around 50,000. Why: the break up of the former USSR led to uncontrolled hunting. Increased rural poverty means the species is hunted for its meat
6/8 Swordfish (Xiphias gladius)
Where: found worldwide in tropical, subtropical and temperate seas. Why: at risk from overfishing and as a target in recreational fishing. A significant number of swordfish are also caught by illegal driftnet fisheries in the Mediterranean
7/8 Argali Sheep (Ovis mammon)
Where: Central and Southern Asian mountains,usually at 3,000-5,000 metres altitude. Why: domesticated herds of sheep competing for grazing grounds. Over-hunting and poaching.
8/8 Humphead Wrasse (Cheilinus undulatus)
Where: the Indo-Pacific, from the Red Sea to South Africa and to the Tuamoto Islands (Polynesia), north to the Ryukyu Islands (south-west Japan), and south to New Caledonia. Why: Illegal, Unregulated and Unreported (IUU) fishing and trading of the species
On the positive side, the large blue, which was reintroduced after extinction in the UK, recorded its second best year on record with numbers up by 38 per cent on 2015 after conservation work to improve the type of grassland habitat the still-rare insect needs.
The widespread red admiral recorded a rise of 86 per cent compared to 2015 and the clouded yellow, another mainly migrant species, saw its numbers rise by 35 per cent.
Anna Robinson, monitoring ecologist at the Joint Nature Conservation Committee, thanked people for helping carry out the survey.
“We are really grateful to the thousands of volunteers who get involved in monitoring the UK’s butterflies,” she said.
“The evidence provided by the [survey] is of great importance in showing the need for conservation action to improve the situation.”
The survey has run since 1976 and involves thousands of volunteers collecting data through the summer. Last year a record 2,507 sites were monitored across the UK.
The scheme is organised and funded by Butterfly Conservation, the Centre for Ecology & Hydrology, the British Trust for Ornithology and the Joint Nature Conservation Committee.Reuse content