The importance of artificial drains for macroinvertebrate biodiversity in reclaimed agricultural landscapes

Abstract

Artificial drainage networks, ubiquitous within lowland agricultural landscapes in Europe and North America, exhibit a range of physical and chemical conditions, and may provide important habitat for aquatic organisms. Drains share hydromorphological characteristics with both lotic rivers and lentic ditches, potentially providing opportunities for a diverse range of taxa. However, little is known about the communities they support. A 23-year benthic macroinvertebrate dataset from four English catchments was used to determine the contributions of drains to biodiversity in a reclaimed agricultural landscape through a comparison of catchments, drain and river channels. A lack of significant differences in gamma diversity and high compositional overlap between rivers and drains showed that drains were not depauperate, and consistently contributed a richness comparable to that of rivers. High-compositional overlap suggested that drains from different catchments contributed comparably to aquatic biodiversity at the landscape scale. Significant differences in environmental conditions (inferred from biotic indices) between catchments may have marginally increased landscape gamma diversity through turnover. Despite similarities in community composition, non-native species were less abundant in drains. This study demonstrates the importance of drains for habitat provision in intensively farmed catchments, and highlights the need for focused research into their management and conservation potential.