Conservationists working to protect Broads butterflies

The Broads Authority and partners are ramping up efforts to protect the area’s butterflies, including the iconic swallowtail.

Late last month, the charity Butterfly Conservation declared a national “butterfly emergency” after the lowest Big Butterfly Count since records began.

Although the exact data for butterflies counted in the Broads will not be available until later this year, Broads Authority ecologists and volunteers report that they have recorded much lower numbers of butterflies during this summer’s Broads’ surveys, and particularly low numbers of swallowtails.

CONCERNS: A swallowtail butterfly and a swallowtail caterpillar. Pictures: BROADS AUTHORITY

The wet winter, cold wet spring and early summer weather meant that significantly fewer numbers of caterpillars have survived the waterlogged conditions in the Broads. Broads Authority Ecologist Hannah Southon said: “We are concerned by the reported decline in butterfly numbers and hope that conservation efforts with our partners will help them recover next year.

“While no one wants this year’s decline to indicate a long-term trend, it should raise alarm bells because swallowtails in particular are so sensitive to annual environmental changes and face multiple threats. By far the largest threat is the impact of climate change upon milk parsley – its preferred food source and where it lays its larvae.

“Other threats include habitat loss and fragmentation, pupa predation by released game birds and the fungal pathogen diaporthe, which has caused milk parsley die-back in previous years.”

Key to securing future swallowtail populations are widescale biosecurity improvements to stop the diaporthe fungus, which can be spread via shoes and boots.

To tackle this, the Authority has installed a boot cleaning station at How Hill. Swallowtail larvae monitoring takes place across Reedham Marshes at How Hill and surveillance monitoring of milk parsley plants has also been heightened across the Broads since milk parsley die back in 2021. Natural England and RSPB may also translocate milk parsley further north in the UK as a long-term precaution in response to climate change.

Working with Broads’ landowners, new butterfly-friendly habitats are being created and restored at nature reserves, fens, mashes and wet woodlands, such as at Wheatfen Nature Reserve in the Yare Valley. Encouraging sustainable woodland management also benefits butterflies by providing healthy environments for feeding, breeding, and overwintering.

The low butterfly numbers appear consistent with reports from volunteers at How Hill and Wheatfen. Weekly butterfly counts at How Hill typically record around 150 in July and August, when butterfly numbers peak. However, this year the most recorded by volunteers was 46. There were also very few swallowtails and only one white admiral recorded.

At Wheatfen Nature Reserve there were very few small tortoiseshells, brimstones, comma and peacock butterflies during April and May. Citizen science projects such as the Big Butterfly Count at How Hill and swallowtail monitoring across the Broads are extremely valuable for guiding conservation efforts because they engage so many volunteers in monitoring butterfly populations and recording sightings.