Success of managed realignment for the restoration of salt-marsh biodiversity: preliminary results on ground-active spiders

Since the early 1990s managed realignment, where formerly reclaimed land is re-exposed to tidal inundation through breaching of coastal embankments, has been increasingly used throughout Northern Europe as a cost effective and sustainable response to biodiversity loss and flood management. This study aimed to evaluate the success of managed realignment schemes that resulted in salt-marsh development for the restoration of spider assemblages. Restoration of saltmarsh fauna was studied by comparing ground-active spiders between recently inundated land (3–14 years old) and pairmatched, adjacent natural salt marshes. Natural reference salt marshes were characterized by a relatively low species richness, the dominance of late-successional stage species such as Pirata piraticus (Clerck 1757), and the presence of species preferring a closed vegetation canopy like Arctosa fulvolineata (Lucas 1846) and Pardosa nigriceps (Thorell 1856). Restored habitats were characterized by greater species richness than in reference habitat and by the presence of halophilic species (Enoplognatha mordax (Thorell 1875) and Erigone longipalpis (Sundevall 1830)) and abundance of Pardosa purbeckensis (Westring 1861). These preliminary results argue for maintaining a maximum of successional stages in salt marshes, as they increase the diversity of halophilic spiders.