Ennerdale's Marsh Fritillaries
Ennerdale is home to a number of species of butterfly including Red Admiral, Small Pearl Bordered Fritillary, Green Hairstreak, Ringlet, Green Veined White and Marsh Fritillary, to name a few.
Apart from their intrinsic beauty, butterflies are an important part of the ecosystem for pollinating flowers and provide a food source for birds.
The Marsh Fritillary is one of most highly protected species of butterfly in Europe and their ideal habitat is lightly grazed wetland, untreated by chemicals. Such habitats as these have declined rapidly since the 1940’s due to drainage and the general intensification of agriculture.
Marsh Fritillary were last recorded on a single site in Ennerdale in the 1970s, becoming extinct in the valley primarily due to habitat loss and fragmentation. Fragmentation leads to the isolation of the colony and genetic weakness as a result of inbreeding.
A few cows will do the trick
More recently, and with thanks to a local farmer, some changes in land management, including the introduction of light cattle grazing, kick-started some much needed habitat restoration. Longmoor Common was identified, by Natural England, to be a suitable site for a re-introduction of this beleaguered butterfly. Marsh Fritillary larvae from a captive bred population were brought in to Longmoor and other suitable sites in Cumbria in 2007 as a consequence of partnership working with National Trust, Butterfly Conservation, Natural England, local farmers and volunteers.
The butterfly population is monitored by counting the number of larval webs present on a site. These webs are highly visible to a trained eye and reflect the number of butterflies present and the breeding success of the colony.
Over the last 8 years, the monitoring results have shown a vast increase in the population size in Ennerdale. This positive trend has been due to a phased approach of release across a number of sites and the provision of a mosaic of suitable habitat for the butterfly to thrive. Although performance on individual sites has been variable, reflecting difficulties in establishing the optimum level of grazing, overall there was a large increase in larval webs from 120 webs in 2013, to 820 in 2014.
Wet summers also have an adverse impact on the butterflies and 2012/13 saw the butterfly numbers struggle. However despite this natural fluctuation the overall increase in numbers gives hope that the butterfly continue to thrive in Ennerdale.
Devils and dams
Gillerthwaite Mire, in the middle valley, used to sit under a blanket of spruce trees. It is now well on its way to being restored thanks to the hard work of various volunteers and help from Cumbria Wildlife Trust. The plantation has gone and dams are being re-instated to block drains and wet the area. This was a naturally boggy mire site and one of the few in the valley, and is now evolving into great habitat for both Devils Bit Scabious (food plant) and Marsh Fritillary.
The future's bright
Viewed in the long term, it's great to see that the one successful site at Longmoor has had a ripple effect in allowing new colonies to become established, both through intervention and natural process. The River Liza corridor and surrounding adjacent fields provides plenty of Devils Bit Scabious. The three herds of Galloway Cattle are also doing their bit by disturbing the ground for new vegetation growth. The future is looking good for the Marsh Fritillary butterfly in Ennerdale.