The impact of a utility corridor on terrestrial gastropod biodiversity

Utility corridors are often thought to be disruptive to biodiversity because they cause habitat fragmentation that may lead to increases in predation, parasitism, disease transmittance and vagrant species while decreasing migration rates, gene flow and genetic diversity for interior species. Species with poor dispersal abilities, sedentary lifestyles, and specialized habitats have been thought to be potentially the most vulnerable to these effects. Terrestrial gastropods thus serve as a valuable system in which to investigate these impacts because they are among the poorest active dispersers in the animal kingdom. To document the impact of corridor formation on land snail biodiversity, a 75-year old powerline right-of-way in the eastern Upper Peninsula of Michigan was chosen for analysis. While terrestrial gastropod richness and abundance was significantly reduced for corridor as compared to adjacent control subsamples, with a 2/3 turnover in species composition, the corridor fauna is similar to nearby native grassland sites in terms of species composition, abundance distribution, and numbers and abundance of species of conservation concern. The fauna of control subsamples immediately adjacent to the corridor remained similar to other undisturbed sites in the region, with multiple species of conservation concern persisting at distances of only 30 m from the corridor. Thus, the net impact of corridor generation has been arguably positive: while the surrounding forest fauna has not been degraded, within the corridor the reduction of forest species has been compensated for by establishment of even rarer grassland species.