Climate association with fluctuation in annual abundance of fifty widely distributed moths in England and Wales: a citizen-science study

Variation in annual abundance of 50 widespread moths in England and Wales was assessed from the area under the log(10)(moth count + 1) versus time curve (abundance index) for adult moth count data reported between 2003 and 2013 to the UK and Ireland Garden Moth Scheme; a citizen science project. Associations between abundance index and the abundance index of the previous generation, with inward migration, and with UK Met Office data for rainfall, mean temperature and sunshine were sought by multiple linear regression. Sixty-eight generations from univoltine or bivoltine species were analysed with a median range in abundance index between equivalent generations of 98 %. Significant (P < 0.05) single or multiple relationships were identified for all species. In 66 of the 68 generations, there was an association to one or more climate variable, four to the previous generation, and one to a measure of inward migration. Most frequently, moth abundance was increased by colder winters, a warm and sunnier spring, and wetter summers, though contrary conditions favoured some species. The time period over which significant climate variables were operating included some that were effective on generations during the preceding season, over the winter, and before and during the adult flight season. A significant difference in frequency of the different climate variables was identified between life-cycle stages in the winter and between larval food plants during the spring and summer. Unknown factors driven by variations in climate were responsible for 72 % of the annual variance in moth abundance in urban gardens.