Loss of habitat and farming practices are thought to be causing a decline in butterfly numbers in Ireland, according to a new survey.
"Butterflies are a lot less frequent than they used to be," according to Dr David Nash, a past president of the Dublin Naturalists' Field Club, who was involved in a recent field project called "Butterflies for the New Millennium".
The survey covered over 200 people and was the only such project in the last 20 years, Dr Nash says. The last was published by An Foras Forbartha in 1982 and there has been "no systematic study or national database since that time", Dr Nash says.
The survey is a joint effort between Butterfly Conservation in Britain and the Dublin Naturalists' Field Club in Ireland to create distribution maps of butterflies for the UK and Ireland. The findings will be compiled in the Butterfly Atlas of Britain and Ireland, which will be published by the end of next year.
The atlas will include photos of the 28 species native to Ireland, information on their status, life cycles natural habitats and trends in their distribution.
The atlas will also include data on the Orange Tip butterfly (Anthocharis cardamines), which was collected for a project funded by the Heritage Council.
Habitat loss is described as the main cause for concern and is regarded as a "major worry" by Dr Nash of the Dublin Naturalists' Field Club. Bogs and wetlands are the natural habitat of two out of six species that are extremely rare in Ireland.
"We would be concerned about the Large Heath (Coenonympha tullia), which has suffered major habitat loss due to the exploitation of our raised and blanket bogs," Dr Nash says.
The Marsh Fritillary (Eurodryas aurinia), another species that is scarce in Ireland and known to be threatened in Britain, is the only species listed under the EU Habitats Directive and the Berne Convention. However, like other species in Ireland it is offered no special protection.
"What has been happening in farming has had a major effect on butterfly numbers," Dr Nash says. Many species are dependent on a narrow range of meadow plants for feeding during both the caterpillar and adult stages. If the insect can't find meadows with the plants it needs then its survival is threatened.
An example is the Small Blue Butterfly (Cupido minimus), which lives along coastal margins and eats and lays its eggs on only one plant which grows on the dunes. Removal of this plant would wipe out the butterfly. Loss of coastal sand dune systems to developments such as golf links is extremely worrying, says Dr Nash.
He is concerned that many of Ireland's meadows have been cleared and "re-seeded with agricultural crops such as rye-grass". Drainage of land, bulldozing of scrub, afforestation and spraying pesticides were also contributing to the problem.
Butterflies are extremely sensitive to changes in temperature and weather conditions, according to Dr Nash. There is a possibility that climate change may be affecting Ireland's butterfly species.
This vulnerability to weather was demonstrated by the high pressure and cool weather during June and July. As a result certain species such as the Small Tortoise Shell (Aglais urticae), which would normally be common in Ireland, were found in lower than normal numbers.
This year's survey was carried out over the summer months, and is part of a long-term project that began two years ago. It would need to be continued for several years in order to successfully monitor butterfly populations in Ireland, Dr Nash says.