Constructed wetlands: high-quality habitats for Odonata in cultivated landscapes


In Norway and throughout the rest of Europe, a continuous decline in the number of small lakes and ponds has taken place. As a consequence, many pond-dwelling organisms have become rare or extinct. Constructed wetlands (CWs) have since the 1990s been used as a remedial action against agricultural runoff. This study has investigated the potential these wetlands have as habitat for freshwater organisms, exemplified by Odonata. Four different CWs in southern Norway were investigated, and larval Odonata species composition was related to a wide range of environmental variables. The material was ordinated using Detrended Correspondence analysis (DCA) and Canonical Correspondence analysis (CCA). All the CWs had high nutrient values and high diversities of aquatic plants. Of the 11 Odonata species found, the richest CW contained 10 species. During the study, one of the CWs was exposed to diazinon (an insecticide). Sun exposure and nutrient content were the most important variables determining species composition. The species that dominated the wetlands were typically euryoecious species, indicating harsh living conditions. Despite the high nutrient content, the results clearly indicate that CWs have an obvious role in pond habitat creation, especially in areas managed according to pesticide-free management.

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