Response of carabid beetles to wetland creation in an intensive agricultural landscape

Abstract

In order to reduce the farming intensity and increase habitat heterogeneity, wetlands are often created in agricultural landscapes. This is because wetlands in agricultural landscapes can decrease sediment deposition, i.e., phosphorus and nitrogen, released as a result of cultivation and fertilization. Additionally, the creation of wetlands can improve heterogeneity within an agricultural landscape. We investigated the response of carabid beetles to restoration and creation of wetlands in a paddy field-dominated agricultural landscape in South Korea. Degraded wetlands, paddy fields, and dry fields (previous habitats) were converted to wetlands, including an abandoned paddy field that existed as a spontaneously restored wetland. Carabid beetle diversity significantly increased with wetland restoration and abandonment of farming practices, while the wetland creation did not have a significant effect. Carabid species composition, from nestedness and co-occurrence indices, did not show significant segregation patterns. Carabid assemblages in the previous habitats and current wetlands were similar to the previous habitats and current wetlands. Only flying carabid beetles showed a significant response to both wetland restoration and creation. Species capable of flight can migrate from surrounding habitats or closely connected habitat areas. Carabid abundance was only elevated with reduction of disturbance by wetland restoration and abandonment, although re-colonized carabid beetles were the dominant species in paddy fields and their landscape. The reduction of farming intensity creates the heterogeneity within restored wetlands and abandoned paddy fields, significantly improving carabid diversity. Our results suggest that in order to achieve the ecological benefits from restoration and creation of wetlands in paddy field-dominated landscapes, the farming intensity should be reduced. The complex configuration of agricultural landscapes can improve carabid diversity therein.