De libellen van de Gelderse Poort: natuurlijk rivierenlandschap soortenrijker dan verwacht

In 2003 fieldwork was carried out to learn about the dragonfly biodiversity in the Gelderse Poort. In this area floodplain restoration projects were realised on a large scale (ca. 800 ha) since 1990. The nature reserves in the Gelderse Poort consists of floodplains with some alluvial forests and river dunes, as well as (reed) marshes in former floodplains. In total 43 species have been observed since 2000 of which 37 have populations in the area. Seven Dutch Red Listed species occur in the Gelderse Poort: Aeshna isoceles, Brachytron pratense, Gomphus flavipes, Gomphus vulgatissimus, Lestes virens, Libellula fulva and Sympecma fusca. This investigation shows the high species richness in dragonflies of natural floodplains. Recently this phenomenon was not well known in The Netherlands. The popular opinion was a rather low biodiversity in dragonflies due to regular flooding and bad water quality. Also the presence of Beavers (Castor fiber) has positive effects on the habitats of some species, for example on Libellula fulva. Males of this species use dead branches cut by Beavers as perches.