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09 December 2022

Creating spaces for rare butterflies on the Dorset-Hampshire border

The team at the Cranborne Estate in Dorset, have created two new butterfly banks on their farm. As part of the Martin Down Farmer cluster, the project is designed to help rare butterflies and bees to find refuge. Funded by Natural England, the effort is part of a wider project of species enhancement, through the ‘Creating Spaces for Species’ project.

Chalk banks for the Small Blue Butterfly, were part of a family of projects including scraping away soil and sowing juniper seeds on the Martin Down National Nature Reserve, which are planted with kidney vetch and seven species of native wildlife. The rare Small Blue Butterfly lays its eggs, lives and feeds exclusively on kidney vetch.

The Martin Down Farmer Cluster is a collective of 15 farmers who farm around the area of the nationally important Martin Down National Nature Reserve. Since 2017 they have worked together to support the wildlife which make their home on the reserve and surrounding farmland, by improving and developing wildlife-friendly habitat alongside productive agriculture.

Megan Lock, Farmland Biodiversity Advisor with the Game & Wildlife Conservation Trust (GWCT), is the Farmer Cluster Facilitator. She provides conservation advice and support to the farmer cluster and helped facilitate the project. Megan said: “After the banks were constructed, we planted nearly 400 kidney vetch plug plants, as well as seeding the banks with Horseshoe and Tufted Vetches, Common Bird’s-foot-trefoil, Self-heal, Lady’s Bedstraw, Devil’s-bit Scabious and Salad Burnet.

“These plants should thrive in the nutrient-poor soil but still leave lots of bare earth for mining bees and burrowing wasps. The Small Blue Butterfly has been chosen by the cluster farmers as one of their priority species. This new habitat should help them increase their range around the Martin Down NNR. The new butterfly banks will also be included in our monitoring programme so we will be able to measure the impact of this conservation work.”

The Small Blue Butterfly is known for being the smallest butterfly found in the UK and despite its name, is not particularly blue in colour. The chalk downland of the Martin Down National Nature Reserve, is a key stronghold for this threatened species.

The banks are approximately 30m long and 1-2m high but, are situated on slopes to look much larger with a south-facing flank. Constructed by digging a trench and burying the topsoil from the bank and adjacent scrape, the chalk sub-soil is then mounded on top covering the topsoil. This creates bank and scrape features that are approximately 600-900 sq m in size.

The Martin Down Farmer Cluster is one of around 200 similar groups of farmers working together for wildlife in the UK. Farmers from the cluster, have chosen turtle dove, hedgehogs, harvest mice, arable flora, bumblebees, small blue butterfly, dark-green fritillary, Duke of Burgundy and lapwing, soil organic matter and chalk downland, as the priorities for their conservation work.

Since forming the farmer cluster in 2017, their achievements have included: planting more than 10km of new hedgerows and increasing pollinator habitat by 50%, installing barn owl boxes, creating 21 turtle dove puddles and ponds, five new butterfly banks, creating habitat for grey partridge and monitoring hedgehogs. As facilitator, Megan carries out wildlife monitoring to measure the impact of their work.

The new butterfly banks were created with the help of the staff of Cranborne Estate and Footprint Ecology.

Cranborne Estate

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