Northern Ireland’s Marsh Fritillary Butterfly Population Rises Amidst Broader Decline

While a “butterfly emergency” has been declared this year, one species in Northern Ireland is defying the general trend. The marsh fritillary butterfly demonstrated its presence during the autumn season, a time when its caterpillars construct noticeable webs within long grass. Surveys in 2024 identified a total of 679 webs across 20 locations, marking an increase of 423 webs compared to the count in 2023. Despite this, the species remains vulnerable, as the number of sites where it is present throughout the UK nearly halved between the years 1985 and 2019. Butterfly Conservation, a charitable organization, advocates for increased support for agri-environment schemes to expand the grassland habitat essential for this butterfly. The charity monitors this species, which was formerly so prevalent in Northern Ireland that farmers in the 1850s documented fields teeming with caterpillars during autumn. Similar to numerous other butterfly species, its population figures significantly decreased across the 20th century. Currently, the marsh fritillary is categorized as stable within Northern Ireland, yet its overall population continues to decline. Environmental classifications, such as Area of Special Scientific Interest (ASSI), contribute to safeguarding locations where this species might be present. This butterfly feeds almost exclusively on the leaves of a plant known as devil’s-bit scabious, a plant that has also experienced habitat reduction and alterations in agricultural methods. During September, thirteen volunteers and two staff members from Butterfly Conservation conducted surveys at 20 locations, observing that the recorded numbers had more than doubled. A brief period of dry, mild weather in June is believed to have contributed to the butterfly’s population increase, alongside effective site management. Rose Cremin, Butterfly Conservation’s Northern Ireland Conservation Manager, stated that the findings represented “a good sign” indicating the effectiveness of habitat protection efforts. She added, “Now we need the government to continue to reward farmers for farming with nature.” Cremin further urged, “We urge the government to put more money into agri-environment schemes aimed at not just maintaining but increasing the grassland habitat which can provide a home for marsh fritillary and a host of other species.” The Northern Ireland Environment Agency (NIEA) provides funding for this monitoring initiative. Pauline Campbell of the NIEA commented that it was “brilliant” to witness the butterfly’s flourishing. She explained, “Northern Ireland has a network of sites designated as ASSIs to support marsh fritillary through careful management their preferred habitat.” Campbell also noted, “The continued management of our species-rich grasslands which support species such as Marsh Fritillary is also delivered through agri-environment schemes such as Environmental Farming Scheme. EFS supports farmers and land managers to carry out environmentally beneficial farming practices.”