Stream restorations with meanders increase dragonfly and damselfly diversity and abundance, including an endangered species

Abstract This study presents examples of successful restoration projects for biodiversity conservation. In West France, the Pinail National Nature Reserve is a protected wetland interspersed with more than 6000 ponds. This wetland is inhabited by 50 species of Odonata and thus is a key biodiversity area for damselflies and dragonflies conservation. In the past, when the limestone was exploited, the streams of the plateau were artificially channeled rectilinearly, running to the Vienne River. Eventually streams were blocked by biomass and sediments resulting in water flowing mainly underground. In 2011, two restoration projects dug and recreated lost habitats such as running streams and meanders by openly reconnecting bodies of standing water (two sites: Rivau (20 m) and Hutte (400 m) streams). The Odonata species diversity and abundance are annually monitored following transect inventories since 1995 and still ongoing. Diversity and abundance were compared before and after the restoration. The abundance and species diversity increased at both sites due to the addition of lotic habitats and consequently additional new species. The number of observed species almost doubled on the Rivau (from 5.4 observed species to 9.9 spp). By extrapolation the total species number on site increased from 15 to 18 spp to 29–37 spp. The abundance also greatly increased with 770 % more individuals on the Rivau. Similarly, on the 400 m Hutte stream, the extrapolated diversity increased from 31 to 38 spp to 35–43 spp; as well as the abundance with 475 % more individuals. These restoration projects created new habitats leading to local biodiversity enrichment and conservation success. More specifically, Coenagrion mercuriale (Odonata: Zygoptera), one of Europe's most threatened damselflies and listed in the European Habitats directive, successfully recolonized the Rivau stream and colonized the Hutte stream.