Shelter benefits less mobile moth species: The field-scale effect of hedgerow trees

Abstract

Agri-environment schemes are the main policy instruments for reversing declines in farmland biodiversity, but there is scope for improvement. Within an intensive agricultural landscape, a mark-release-recapture experiment was used to investigate the relative effects on the number of adults of 23 moth species of two landscape features (wide field margins and hedgerow trees) that may feature within agri-environment schemes. Species belonged to either the grass/herb- or shrub/tree-feeders’ guild. Margin width did not affect the number of individuals, in either guild. Numbers of shrub/tree-feeding individuals were higher at sites with hedgerow trees, but not so for this guild's two most mobile species, nor for the grass/herb-feeders, which were 30% more mobile. The results show that hedgerow trees increase adult moth numbers because they are shelter-providing resources in typically exposed agricultural landscapes, rather than due to being larval food resources. Hedgerow tree retention and establishment options should be part of efficient general agri-environment schemes, while grassy wide field margins may not always deliver gains, at least not when implemented at the field-scale.