North Sea nature is under pressure as a result of intensive human use, including fisheries, sand extraction, shipping and the construction of offshore wind farms. Within the Natuurversterking Noordzee (NN) programme, measures are being developed to support the recovery and strengthening of the marine ecosystem.
For Natuurversterking Noordzee, OR ELSE researchers Marcel Rozemeijer and Martin Baptist investigated whether seabed engineering could also actively contribute to nature enhancement through targeted manipulation of sandy seabeds, both on the natural seabed and in existing, paused sand extraction pits.
Sandy seabeds are the dominant habitat type in the North Sea and play a crucial role in the ecosystem, but they are under pressure from human activities that disturb the seabed. Sand extraction has demonstrated negative ecological impacts, but at the same time it also creates opportunities for nature-inclusive design. Rozemeijer and Baptist explore the possibility of deliberately steering sediment characteristics — such as grain size, stability and silt content — in order to optimise habitats for specific target species.
This proposed approach focuses on key species that fulfil important ecological functions within the ecosystem. One primary target species is Spisula subtruncata (truncate surf clam). This species is ecologically valuable and serves as an important food source for protected seabirds such as the common scoter. Research shows that Spisula beds occur approximately 30% more frequently on sandy seabeds with a grain size of 180–230 µm. The targeted placement of sediment with these characteristics could stimulate the establishment and development of Spisula beds.
In addition, sandeel is an important species within the North Sea ecosystem because of its key role in the marine food web. This species prefers coarse sand with low silt content. In paused sand extraction pits, leaving behind a thick layer of coarse sand could contribute to habitat improvement. Researchers are also investigating to what extent the design of sand extraction pits influences the behaviour and distribution of pelagic fish species.
The proposed measures will initially be tested through pilot projects, both on the natural seabed and in paused sand extraction pits near Ameland. Experimental plots will be created in which sediment characteristics are deliberately modified. The pilots will be scientifically supervised and include an integrated monitoring programme.
A key question is whether these manipulated locations will actually lead to the sustainable establishment of target species and a measurable improvement in biodiversity. The results of the pilot projects will form the basis for decision-making on possible upscaling. Based on a first estimate, only around 1% of the annual sand extraction volume would be required to realise 100–200 hectares of nature enhancement each year on a larger scale. This offers prospects for a cost-efficient and spatially feasible measure within existing sand extraction activities.
This proposed approach demonstrates how economic activities and nature enhancement do not necessarily have to be in conflict. By linking sand extraction to ecological design principles, it may be possible to contribute to a more resilient North Sea ecosystem. Targeted sediment management therefore offers a concrete pathway within broader policies for nature restoration and the sustainable use of the North Sea.
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