Protecting the North Sea: Borkum Stones

Borkum Stones (Borkumse Stenen in Dutch, and Borkum Riffgrund in German) is a shallow, transboundary area shared between the Netherlands and Germany, and is one of the few remaining areas of natural geogenic reef in the southern North Sea. The seabed of Borkum Stones is heterogeneous, comprising a mix of hard substrates (ranging from cobbles and pebbles to large stones) surrounded by sand and gravel. This mosaic of substrates, in turn, supports a diverse benthic community with higher biodiversity levels than in neighbouring areas. Moreover, Borkum Stones is home to biogenic reefs formed by sand mason worm (Lanice conchilega), fragile structures that serve as important habitat for associated marine fauna. In 2007, the German side of the area was designated as a Natura 2000 site (Borkum-Riffgrund), based on the presence of reefs and sandbanks, as well marine mammals, birds, and benthic invertebrates and fishes. Research surveys on the Dutch side of Borkum Stones have also revealed the presence of reefs and sandbanks, thus making the area eligible for similar protection. However, the Dutch side of the area remains unprotected, despite its recognised biodiversity value and ecological similarity to the German side. In 2017, Oceana carried out a research expedition in the Dutch waters of Borkum Stones, to gather further information about the area’s benthic species and communities. This research represented the first time that a remotely operated vehicle was used in the area, with further surveys carried out via filming by SCUBA divers, infaunal grab sampling, and seafloor imaging with a multibeam echosounder. In total, 148 taxa were identified, including 21 species that are priorities for conservation and 20 commercial species, some of which have nursery and/or spawning areas within Borkum Stones. Three habitat types were also documented that are priorities for conservation: sandbanks, and geogenic and biogenic reefs (i.e., stone fields and sand mason worm reefs, respectively). Both sandbanks and reefs are declining in the Netherlands due to human impacts. Oceana recommends that the Dutch waters of Borkum Stones be protected, in order to safeguard their valuable benthic biodiversity. By protecting the area’s sandbanks and reefs, and the species associated with them, the Netherlands would also enhance the ecological coherence of its network of marine protected areas and advance towards the fulfilment of its legal commitments at both the national and EU level. In particular, the protection and restoration of biogenic reefs is a target of the Dutch government under the EU Marine Strategy Framework Directive, and the presence of such reefs in Borkum Stones makes the area a strong candidate for protection. To effectively conserve this transboundary area, Germany and the Netherlands must ensure the greatest possible consistency in terms of designated features and the development and implementation of management measures to protect them from human impacts. In parallel with these efforts, Oceana urges the Dutch and German governments to carry out comprehensive benthic habitat mapping of Borkum Stones, particularly to determine the full extent and condition of the fragile reefs formed by sand mason worm (L. conchilega)