title: Time is no healer: increasing restoration age does not lead to improved benthic invertebrate communities in restored river reaches.
abstract: Evidence for successful restoration of riverine communities is scarce, particularly for benthic invertebrates. Among the multitude of reasons discussed so far for the lack of observed effects is too short of a time span between implementation and monitoring. Yet, studies that explicitly focus on the importance of restoration age are rare. We present a comprehensive study based on 44 river restoration projects in Germany, focusing on standardized benthic invertebrate sampling. A broad gradient ranging from 1 to 25years in restoration age was available. In contrast to clear improvements in habitat heterogeneity, benthic community responses to restoration were inconsistent when compared to control sections. Taxon richness increased in response to restoration, but abundance, diversity and various assessment metrics did not respond clearly. Restoration age was a poor predictor of community composition and community change, as no significant linear responses could be detected using 34 metrics. Moreover, only 5 out of 34 tested metrics showed non-linear shifts at restoration ages of 2 to 3years. This might be interpreted as an indication of a post-restoration disturbance followed by a re-establishment of pre-restoration conditions. BIO-ENV analysis and fourth-corner modeling underlined the low importance of restoration age, but revealed high importance of catchment-scale characteristics (e.g., ecoregion, catchment size and land use) in controlling community composition and community change. Overall, a lack of time for community development did not appear to be the ultimate reason for impaired benthic invertebrate communities. Instead, catchment-scale characteristics override the effectiveness of restoration. To enhance the ecological success of future river restoration projects, we recommend improving water quality conditions and catchment-scale processes (e.g., connectivity and hydrodynamics) in addition to restoring local habitat structure.
authors.affiliation: Senckenberg Research Institute and Natural History Museum Frankfurt, Department of River Ecology and Conservation, Clamecy Strasse 12, 63571 Gelnhausen, Germany; Johann Wolfgang Goethe University of Frankfurt am Main, 60629 Frankfurt am Main, Germany. Electronic address: Moritz.Leps@senckenberg.de.
authors.forename: Moritz
authors.initials: M
authors.lastname: Leps
authors.affiliation: Senckenberg Research Institute and Natural History Museum Frankfurt, Department of River Ecology and Conservation, Clamecy Strasse 12, 63571 Gelnhausen, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Sundermann
authors.affiliation: Senckenberg Research Institute and Natural History Museum Frankfurt, Department of River Ecology and Conservation, Clamecy Strasse 12, 63571 Gelnhausen, Germany; Oregon State University, Department of Integrative Biology, 3029 Cordley Hall, Corvallis, Oregon 97331, USA.
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Tonkin
authors.affiliation: University of Duisburg-Essen, Faculty of Biology, Universitätsstrasse 5, 45141 Essen, Germany.
authors.forename: Armin W
authors.initials: AW
authors.lastname: Lorenz
authors.affiliation: Senckenberg Research Institute and Natural History Museum Frankfurt, Department of River Ecology and Conservation, Clamecy Strasse 12, 63571 Gelnhausen, Germany; University of Duisburg-Essen, Faculty of Biology, Universitätsstrasse 5, 45141 Essen, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Haase
mesh_terms: D000818:Animals; D004463:Ecology; D052918:Environmental Restoration and Remediation; D005858:Germany; D007448:Invertebrates / Q000502:physiology*; D045483:Rivers / Q000737:chemistry; D060753:Water Quality / Q000592:standards*
keywords: Macroinvertebrates; Revitalization; Species traits; Stream; Time effect