Adrian Spalding explains how Natural Areas are providing a framework for the future of conservation, and how this works beautifully for butterflies.
Natural Areas are zones of recognisable character whose boundaries do not follow existing administrative boundaries, but are defined by their wildlife, natural features, land use and human history. Natural Areas already provide the framework for much of English Nature's work, and provide a context for the setting of conservation and biodiversity objectives.
Cornwall's seven Natural Areas
There are seven Natural Areas in Cornwall, comprising five inland areas (the Cornish Killas and Granites which cover the bulk of Cornwall - Bodmin Moor, the Culm, The Lizard and West Penwith) and two coastal areas (Land's End to Minehead and Start Point to Land's End). The coastal areas extend inland as far as the coastal influence and out to sea for 12 miles. English Nature is currently preparing Natural Area profiles for Cornwall. These will contain lists of key species characteristic of each area, and will be highly useful to the general public and wildlife conservation bodies alike.
Butterflies as habitat indicators
Many of these key species are butterflies, which are popular and easy to identify. Butterflies are also easy to monitor and, since many species respond quickly to changes in habitat, they can be useful indicators of habitat deterioration. The Species Recovery Programme, led by English Nature in partnership with other agencies, includes five Cornish species - large blue, heath fritillary, high brown fritillary, pearl-bordered fritillary and marsh fritillary.
The large blue, last definitely recorded in Cornwall in 1973, is characteristic of the maritime grassland of the north coast (Land's End to Minehead), where colonies of up to 10,000 once occurred. Now successfully reintroduced to six sites in England, it is hoped that reintroduction into Cornwall will occur within the next three years.The heath fritillary, characteristic of the Killas areas of East Cornwall, has been a success story in which the Cornwall Wildlife Trust has participated.
The high brown fritillary is characteristic of the fringes of Dartmoor, but records from the south east of Cornwall, The Lizard and the extreme north of Cornwall suggest that it still occurs here. The pearl-bordered fritillary is associated with the wooded rides of the Killas, but is fast disappearing as woodland management changes. The marsh fritillary has suffered a 60% national decline over the last 25 years. It is a sporadic butterfly, living in dispersed groups with limited mixing known as meta-populations, and may apparently disappear from sites for a few years before reappearing. Associated in Cornwall with wet heathland on The Lizard, the Mid-Cornwall Moors and Bodmin Moor, many former sites on the Culm have now disappeared.
Besides these species, there are five locally important butterflies characteristic of Natural Areas in Cornwall, for which Butterfly Conservation (Cornwall) is currently preparing action plans. Current declines in these species indicate that wildlife is still under threat in the Natural Areas of Cornwall as we approach the end of the century
Well known as an authority on butterflies and moths, and as Academic Director of the Cornish Biological Records Centre before its merger with the Trust, Adrian Spalding is currently working under contract to English Nature on Cornwall's Natural Areas.
Cornwall is an important stronghold for the scarce marsh fritillary butterfly in the UK, and until recently little was known about its preferred breeding areas in Cornwall. I have recently completed a preliminary study on Goss Moor National Nature Reserve that has produced some interesting results.
The caterpillars spin a web over their favourite food - devil's-bit scabious leaves - between late July and early October, and move from leaf to leaf, leaving a trail of derelict webs and skeletal leaves behind them. Devil's-bit scabious is common in damp grassland and heaths throughout Cornwall, but the butterflies choose specific places to lay their eggs.
Sward structure is important. Patches of short grass with abundant devil's-bit scabious surrounded by a taller sward, often dominated by purple moor-grass and on exposed sites close to a scrub edge, are ideal. This study showed that the type of vegetation in these breeding areas has more in common with that used by marsh fritillaries in South West Scotland than in West Wales or Devon. The type of management of this wet heath/mire vegetation is significant. Summer burning (which is illegal) and/or horse grazing is disastrous because it destroys the sward structure. The best form of management appears to be light burning in early spring (no more than once every fifth year) followed by cattle grazing in the summer. The adults, which appear from late May to early July, need nectar, which is why overgrazing or illegal burning pose the additional threat of destroying the adults food supply