Changes in carabid diversity indicate successful restoration of riparian habitats

Abstract

Natural rivers offer riparian habitats to many highly specialised, rare, and endangered insect species and are extremely important for ecosystem services. In the past, these ecosystems have been heavily degraded by anthropogenic use and run the risk of losing their favourable ecological conditions. For this reason, restoration measures are urgently needed and strongly demanded politically as well as legally, for instance, through the European Union Water Framework Directive. This is also important because nowadays, we are confronted with increasing insect declines.Using a Before-After-Control-Impact approach, we studied the effects of a riverbank restoration (complete removal of a large gravel embankment) on carabid assemblages of riparian habitats along the Mulde River in central Germany in 2017 and 2019. We collected 86 species in three site types (managed, natural, and restored) by pitfall trapping and found numerous species of conservation concern. Our analyses showed that the percentage of species of conservation concern was significantly higher after restoration in restored compared to managed sites. Furthermore, after restoration, the percentage of indicator species for natural sites increased significantly in restored sites while the abundance of indicator species characteristic for managed sites decreased in these sites. Species assemblage composition significantly changed in response to restoration approaching nearnatural conditions. The creation of habitat mosaics with open gravel and sand patches as well as the re-establishment of river dynamics were likely the most significant drivers for restoration success. We were able to show how important the restoration of riparian habitats is to promote populations of endangered, rare, and specialised species. Our results highlight that positive effects of a river restoration measure can be observed after a relatively short time. Ground beetles can thus be viewed as early indicators for restoration success, but we see a need for long-term monitoring to evaluate long-term effects reliably.

Effective restoration measures in river‐floodplain ecosystems: Lessons learned from the ‘Wilde Mulde’ project

“…In addition, longer‐term evaluations are also necessary to assess ecosystem services to gain valid conclusions (MEA, 2005). In any case, the results from projects such as the ‘Wilde Mulde’ contribute to our understanding of drivers and their multiple effects and interactions in riverine landscapes (e.g., Anlanger et al, 2022; Gapinski et al, 2022; Kretz et al, 2021; Schnauder et al, 2021; Seele‐Dilbat et al 2022; Sprössig et al, 2022). During the scientific monitoring, we measured many indicators that contain proxies for immediate success, such as flow diversity and the diversity of riverbed topography and those that attracted keystone species such as fishes and birds.…”

Special issue editorial: Revitalisation of dynamic riverine landscapes—Evaluation of the effects of hydromorphological restoration measures

“…Two contributions describe the early effects of rip‐rap removal in the Mulde River. Sprössig et al (2022) compare carabid communities and Seele‐Dilbat et al (2022) vegetation communities in riparian habitats before and after the removal of rip‐rap. Two years after restoration, both communities at restored sites differed clearly from those at unrestored sites.…”