Northern Brown Argus: Borders is home to threatened butterfly

Butterfly Conservation Scotland (BCS) says the Borders is home to “significant nationally important colonies” of the Northern Brown Argus butterfly.

However, the organisation adds that 54 out of 92 colonies identified have been deemed under long-term threat, due to unsuitable grazing and afforestation of its favoured habitat – species-rich grassland.

BCS conservation officer David Hill said: “Tree planting is being carried out by landowners and investors across the Borders on land formerly used for grazing, usually supported by Forestry Grant Schemes.

“Some consultation will be carried out on all large planting schemes but, due to lack of awareness about species-rich grassland and Northern Brown Argus, BCS are not always included in the consultation process and there are numerous examples of trees being planted directly upon important habitat in recent years.”

Many Scottish sites of the Northern Brown Argus colonies – one third of which are believed to be in the Borders – are also being lost to gorse and bracken invasion, on land formerly used for grazing sheep and cattle.

Mr Hill added: “Volunteer surveys have so far identified around 150 potential colonies of Northern Brown Argus in the Borders, although some have already been lost and many other are threatened.

“Even small patches of species-rich grassland can provide vital habitat and be important stepping stones increasing connectivity between populations of Northern Brown Argus across the wider landscape.

“If even a few colonies are lost then surviving populations become very isolated and less resilient.”

The BCS’s Saving the Northern Brown Argus in the Scottish Borders project, which received funding from The National Lottery Heritage Fund, has been working with landowners and woodland agents to adapt planting plans to leave pockets of species-rich grassland habitat for the Northern Brown Argus to survive.