Comparative biodiversity of aquatic habitats in the European agricultural landscape

Recent evidence has begun to call into question the assumption that aquatic biodiversity is concentrated exclusively in larger rivers and lakes, instead showing that it is distributed throughout the landscape and that small waterbodies, such as ponds and ditches, make a significant contribution to biodiversity. We compared the physicochemical and aquatic biodiversity characteristics of ditches, lakes, ponds, rivers and streams in five locations in Europe in three biogeographic zones. At the individual site level (alpha diversity), rivers were found to be the most species-rich waterbodies; however, at the regional level (gamma diversity), ponds were the most species-rich aquatic habitat for both wetland plants and macroinvertebrates. In terms of rare species, ponds also had a higher rarity value, measured by a Species Rarity Index, than other habitat types, although data for this analysis were only available from the United Kingdom. The high biodiversity values of ponds suggest that they should be more central to strategies for the protection and management of aquatic biodiversity. (C) 2007 Elsevier B.V. All rights reserved.