A comparison of created and ancient fenland using ground beetles as a measure of conservation value

1. Ground beetles (Coleoptera: Carabidae) were used to assess the conservation value of created and undrained fenland on Wicken Fen, UK. We investigated whether the number of years since agricultural use affected the numbers of Nationally Scarce and wetland ground beetles on created fens. We also compared the created wetland with ancient undrained fenland. 2. Common wetland ground beetles increased with time since agricultural use. However, Nationally Scarce ground beetles did not increase over time. All areas of created wetland had fewer Nationally Scarce and common wetland ground beetles than undrained fenland except for the area not used for agriculture for 60 years. This area had fewer Nationally Scarce ground beetles than undrained fenland but not significantly fewer common wetland ground beetles. 3. The proportion of wetland ground beetles with high dispersal abilities did not vary in relation to time since agricultural use or distance from the nearest drainage ditch, indicating that dispersal did not limit colonisation. Therefore, proximity between the created wetland and established fenlands was not essential for wetland species to colonise the new habitat. 4. The ground beetle assemblage was influenced by soil moisture, cover of grasses and vegetation density. Of these variables, high soil moisture and low vegetation density increased the abundance of Nationally Scarce and common wetland ground beetles. High vegetation density was more detrimental to Nationally Scarce ground beetles than to common wetland beetles. Decreasing the vegetation density by increasing the grazing intensity on created wetland may increase the abundance of Nationally Scarce ground beetles.