Habitat and landscape-scale effects on the abundance and diversity of macro-moths (Lepidoptera) in intensive farmland

Since 1968 UK macro-moths have declined by 28%, with the most notable trends revealed for the south of England; the dual influences of climate change and intensive land use are thought to be the main drivers for this trend. This study aimed to determine the landscape and local-scale factors influencing moth abundance and species richness in intensive Northamptonshire farmland. The research consisted of four parts: 1. the analysis of historic county moth records using landscape-analysis, 2. Moth trapping in areas of intensive lowland farmland and subsequent local and fine-scale landscape-scale analysis of trap yields, 3. Moth movement studies along farmland hedgerows and 4. Moth visitation surveys of hedgerow flora. The results of the analysis of county moth records revealed that land-use statistics had a highly significant relationship with the abundance of moths across Northamptonshire. Woodland cover was found as having a positive relationship with the abundance of moths, but that urban cover was negatively associated. The farmland moth trapping study recorded a total of 121 species, the majority of which were generalist (98%) and none of which have Biodiversity Action Plans. For this trapping, hedgerow length, width and cross-sectional area, vegetative diversity and the numbers of hedgerow gaps all had an influence on the abundance of some of the species trapped, but no hedgerow or margin variables had a significant influence on overall abundance or species richness. Moth movement surveys found that a significant proportion of moths were travelling parallel along hedgerows (69% of moths observed at 1m from the hedgerow) in farmland and that moth activity was higher close to hedgerows. Nocturnal visitation surveys of hedgerow flora found that 53% of visitors were Lepidoptera and that the most visited species was Bramble (Rubus fruticosus agg.). The results of the combined studies suggest that land use influences moth abundance at a range of spatial scales and that hedgerows may be providing sheltered dispersal routes and nectar resources for these species.