Abstract
The Loire, the last wild river in Western Europe, undergoes recurrent maintenance operations of bed to improve flow and to avoid reduction of the main stem. Thus, the territorial collectivities carried out levelling of one island in autumn 2012 in the Natural Reserve of Saint-Mesmin (France). We took advantage of this work to launch a long term survey of the island recolonization by plants, birds, beavers and insects. We report here the impact on insect populations taking ground beetles (Coleoptera : Carabidae) as a model study. We compared assemblages (communities) before and just after the levelling. Sampling was done with Barber traps and quadrats in eight habitats of the island as well as in various sites located upstream or downstream. We found high levels of species richness within these pioneer and ephemeral habitats. Several species of ground beetles appeared to be good indicators of sampled habitats where extreme environmental conditions generally prevail. Community analyses indicated that ground beetle very quickly colonized newly created habitats and allowed us to identify species being very good pioneers of early successional habitats.