Return of the large blue

A large blue butterfly in one of two new colonies re-introduced to a National Trust Cotswold site.

Rare large blue butterflies return to the UK in flourishing numbers on restored grasslands.

The unprecedented success of this project is testimony to what large scale collaboration between conservationists, scientists and volunteers can achieve.

The large blue butterfly, once-extinct in the UK and reintroduced in 1983, flew in its greatest numbers on the largest number of sites  in 2022 since records began.

Thanks to meticulous conservation management by a partnership of scientists and conservation bodies, south-west England now supports the greatest concentration of large blues known in the world.

Twelve new sites are being restored to flower-rich meadows suitable for large blue's breeding, either ‘starting from scratch’ on arable land, failed conifer plantations and railway constructions, or by restoring bespoke grazing to degraded downland. Already, these support up to a third of the UK population of large blues, up from just seven percent in 2019.

Re-emergence 

These restorations of a disappearing type of wild meadowland have also provided ideal breeding grounds for numerous other rarities that share the large blue’s habitat.

Nikki Jeffery, executive director of the Prince of Wales’s Charitable Fund“This project has been a great example of what sensitive habitat restoration can achieve, resulting in record new populations of the Large blue butterfly as well as the re-emergence of other rare insect and plant species.

"PWCF is delighted that our funding, in collaboration with the Royal Entomological Society and other partners, has had such a significant impact.”

Among plants, the extremely rare Pasqueflower and Cut-leaved self-heal have reappeared during management of the project.

Thriving

So have up to twelve species of orchid; Musk, Fly, Bee, Green-winged, Scented, Pyramidal, Spotted, Early purple, Greater butterfly, Autumn lady’s tresses, Narrow-leaved helleborine and White helleborine. 

A remarkable number of other insects have increased on the sites, while others newly colonised some of the twelve restoration spots. 

These include nationally threatened species such as the Shrill carder bee, which is the UK’s second most endangered bumblebee, and the Downland villa beefly, which has not been recorded in UK for 50 years prior to 2000. 

Eight Red Data-listed butterflies - Duke of Burgundy, small blue, Adonis blue, brown hairstreak, white-letter hairstreak, small heath, grizzled skipper, dingy skipper – are also thriving alongside abundant displays of more common or local insects and plants.

Testimony 

These restorations represent the largest and most innovative next phase of the re-establishment of the large blue in Britain.

Aside from the gains of other rare species, they are important internationally because the large blue is listed as one of Europe’s most endangered species of insect, and similarly worldwide.

Professor Jeremy Thomas, emeritus professor of Ecology, said: “The unprecedented success of this project is testimony to what large scale collaboration between conservationists, scientists and volunteers can achieve.

The unprecedented success of this project is testimony to what large scale collaboration between conservationists, scientists and volunteers can achieve.

"Its greatest legacy is that it demonstrates that we can reverse the decline of globally-threatened species once we understand the driving factors."

Promising 

The twelve sites link or extend more-established populations spanning two landscapes in mid Somerset and, more recently, in the Cotswold Hills of Gloucestershire where a most promising toehold is now established.

The new restoration sites are managed, owned or administered by six partner organisations – National Trust, Somerset and Gloucestershire Wildlife Trusts, J & F Clark Trust, Natural England and Oxford University.

The restorations are led, supervised and monitored by the Royal Entomological Society’s David Simcox and Sarah Meredith, who also designed the bespoke management plan needed for each site.

Enigmatic 

Mr Simcox said:  “We have welcomed the opportunity to continue working on this iconic and difficult butterfly and to lead this diverse and energetic partnership.

"We are extremely proud that the partnership’s efforts have enabled hundreds of people to see this stunning and enigmatic butterfly flying on some of the most beautiful grassland sites in the country.

"The greatest challenge ahead is to secure this expansion in a warming climate and to develop strategies to mitigate the impacts of extreme weather events.”

Climate 

After a promising start, the next phase of restoration is to extend the large blue and associated wildlife across three landscapes in its former stronghold of the Cotswold Hills.

A greater understanding of the threats posed by global heating is needed, in order to further restore eco-systems that are having to adapt to increasingly changing weather patterns. 

Future research will again be led by the Royal Entomological Society and funded by Natural England’s Species Recovery Programme - so that more plants and insects can flourish under the wing of the large blue project. 

This Author 

Yasmin Dahnoun is the assistant editor of The Ecologist. This article is based on a press release from the Royal Entomological Society.

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