Initial population trends from a 5-year butterfly monitoring scheme

Abstract

The Irish Butterfly Monitoring Scheme started in 2007. The main objective of this study was to examine initial population trends from data gathered over 5 years (2008–2012) by approximately 150 volunteers across the Republic of Ireland. Nine of the 15 species analysed showed changes in population over the 5-year period; three species showed steep or moderate increases while six species showed moderate or steep declines in population. Some of these population changes are due to the highly variable weather conditions over the five years of monitoring, particularly the unusually cool, wet summer of 2012. However, factors affecting butterfly population trends are many and varied, so longer-term data are required to assess trends more reliably. A further six species had indeterminate trends over the 5-year period however, as the scheme develops, longer-term trends will have greater statistical reliability and give a clearer insight into Irish butterfly populations. The Irish Butterfly Monitoring Scheme is important in the national context, as there is little other countrywide systematic monitoring of insect populations. Furthermore, with a growing number of such standardised monitoring schemes internationally and development of bioindicators, it is now possible to monitor and track butterfly populations at larger spatial scales. We recommend that the Irish Butterfly Monitoring Scheme is continued over the long term and expanded to ensure that more Irish butterfly species are sufficiently monitored. However, in addition to monitoring population trends, basic research is still needed into the ecology and population dynamics of common butterfly species.