Corridor width determines strength of edge influence on arthropods in conservation corridors

Abstract

In fragmented landscapes, edge influence (EI) can be an important driver of ecological change. Multiple edges can interact so that distance to the nearest edge is not an accurate predictor of EI, an issue referred to as ‘interactive EI’. This is especially important in conservation corridors, since their linear nature puts multiple edges in close proximity. We assess how corridor width, an important design variable in conservation corridors, influences EI on arthropod diversity. Arthropods were sampled along the edges of grassland corridors of different widths, and from nearby protected areas (PAs) as reference. The influence of corridor width on edge-related change in arthropod diversity was assessed. This was done at the scale of single corridors, and in comparison to nearby PAs. Corridor width influences EI strength. This was apparent at the local scale, and for those species associated with the corridor interior. At the landscape scale, distance to the nearest edge was more important for the similarity of corridors to PAs than corridor width. This was driven by edge specialists rather than grassland interior species. Interactive EI influences local edge responses, especially for species which avoid edges. Future assessments should incorporate processes operating across larger scales into edge responses. We show that there is much greater conservation value in larger corridors for grassland specialists than smaller corridors, and for a given area of set-aside conservation land, we support the establishment of a few wide corridors over many narrow corridors in production landscapes.