Half of Britain’s butterfly species are now listed as endangered after five more joined the new ‘red list’ of endangered butterflies.
The rise in the number of species listed as ‘vulnerable’ from nine in 2011 to 16 today is a warning that time is running out to save the 58 resident species, according to Butterfly Conservation, which compiled the Red List from data scientific monitoring according to criteria established by the International Union for Conservation of Nature (IUCN).
But there are positive trends on the list, which covers data from 2010 to 2019, with two of the most endangered species, the greater blue fritillary and the greater brown fritillary, moving out of the most at-risk category. after targeted storage.
The big blue, which went extinct in 1979 but was reintroduced from Sweden, has been upgraded from “critically endangered” to “near threatened”, the least risky of the IUCN’s assessments as endangered apart from ” least worrying”. It thrives in restored wildflower meadows in the Cotswolds and Somerset.
In recent years, the tall brown fritillary has been considered the species most likely to become extinct since the big blue.
But conservation efforts in the southwest of England and at its only remaining site in Wales have proven successful. The butterfly has rebounded, although its distribution at sites continues to decline, meaning it is now ‘vulnerable’ rather than ‘critically endangered’.
“Given that the overall picture is one of increasing risk, the fact that highly threatened species that have been the focus of conservation efforts have become less threatened is a real benefit,” said Richard Fox of Butterfly. Conservation. “With considerable effort and resources, we can at least conserve these species and, in some cases, reverse them.”
Other success stories include the Duke of Burgundy and the Pearl-lined Fritillary, which were upgraded from ‘endangered’ to ‘vulnerable’ after targeted conservation actions by charities and local communities.
But there are growing concerns for other once-thriving species that have slipped into the “vulnerable” category. Adonis blue, chalk blue and silver speckled skipper has moved despite decades of conservation work increasing their numbers.
All three species require warm, short, flower-rich chalk grasslands, and all declined disastrously in the mid-20th century with the loss of these grasslands and a reduction in traditional grazing.
Since the 1980s, all three have been revived and seemed to benefit from global warming, moving north to new locations. However, their decline over the past decade may be caused by new factors, such as increased nitrogen deposition – from agricultural fertilizers and vehicle pollution – which lead to vigorous grasses crowding out caterpillars. more delicate wildflower moths that wildflower moth caterpillars need to survive.
“It’s disappointing to see these species return to the threatened group,” Fox said. “Insidious changes in the environment due to climate change or nitrogen or both mean that the habitat created by conservation management 20 years ago does not necessarily produce the same results today.
“Land managers must continually experiment to produce suitable habitats for species like these, because everything else changes. In the Nederlands, scientists are convinced that nitrogen deposition is a major factor in the decline of some of their rare butterflies.
The negative impact of global warming is evident in the inclusion in the threatened categories of the four butterflies found in cooler northern habitats. Greater heather, scotch argus and northern brown argus are now listed as ‘threatened’ and ringlet as ‘near threatened’. ”. All four species are likely to disappear from southern parts of their range.
The Red List requires five years of positive data before an endangered species can be considered reviving, so the new list does not yet reveal any improvements.
These include a resurgence for whitewood after intensive conservation management. While another butterfly, the large tortoiseshell, listed as extinct, has mysteriously reappeared in several locations in southern England as a breeding butterfly since 2019.