Wageningen University & Research: Research on ecological effects of sand extraction granted in NWA ORC-call

A study on ecologically optimising sand extraction in the North Sea has been accepted within the National Science Agenda. The study aims to keep the marine ecosystem healthy while continuing to supply us with food. Governments, fishers, dredgers, nature protection organisations and researchers see that the global supply of sand is shrinking, while increasing volumes of sand from the North Sea are needed to protect our coasts from the rising sea levels. This is why we will develop new knowledge on the effects of sand mining in a five-year interdisciplinary consortium project with a 5.1 million euro budget. Wageningen Marine Research will lead the project, which was accepted simultaneously with 28 other research applications within the framework of Research by Consortia (NWA ORC-call 2020/2021).

In the Netherlands, as in other regions, we extract sand, mainly from the North Sea. We mine some 12 to 15 million cubic metres per annum to protect our coasts and a further 15 million cubic metres to serve as fill sand for roads and residential areas as well as for concrete and construction sand. Every year, we remove a volume of sand equal to the area of Schiermonnikoog and 80 cm deep. But our demand for sand is increasing. Not just because we want to construct more roads, residential projects and houses, but also because we need an increasing volume of sand to protect our coastal areas from the rising sea levels.

Impact of sand mining in the North Sea
The Randstad is protected by dunes. Beautiful, natural systems that protect us from the sea. Dunes are a self-restoring sea defence, but the rising sea levels mean we have to replenish this sand constantly. To this end, we extract sand from the North Sea at a depth of at least twenty metres in an area specifically designated for this purpose. Sand mining damages marine life in and on the sea bed. The suction of sand takes shells, worms, sea stars and fish with it, who perish. Sand mining can render the water so turbid that it has an adverse impact on algae growth, the very foundation of the marine food chain—moreover, the marine animals’ habitat changes due to a change in the size of sand grains. Finally, the pits and gulleys thus created alter the sea currents.

Considering how to leave the North Sea bed
Because we need increasing volumes of sand, we must carefully consider how we wish to leave the Nort Sea bed behind, says coordinator Martin Baptist. ‘If you mine sand in shallow waters, the ecological impact occurs over a huge area. If you mine in deeper waters, less marine life is killed, but the sea bed requires more time to recover, and the currents are influenced, he says. ‘We have already seen that the sand mining pit off the Tweede Maasvlakte, which had a depth of some twenty metres, contains much sludge, which is concerning since the Dutch coast is a key nursery for commercial flatfish such as sole and plaice.’ These fish’s larvae travel from the North Sea to the coast on the currents along the seafloor. Deep pits and gulleys could easily disturb these currents.

Baptist indicates that the research consortium will study how, in what direction, under what angle and at what depths sand can best be extracted to avoid endangering plaice and sole. However, sand mining also offers opportunities for fishers. They know, like no other, near what pits and slopes their catch is best. ‘We could thus create an underwater landscape that benefits fish, and by this the fisheries sector’, he states.

Global issue
Sand extraction is a global issue. It is a resource that is not easily extracted anywhere and that we need in increasing quantities. Sand can be compared to fossil fuels: We mine more sand than nature is capable of replenishing. The great demand means rivers and beaches are excavated, with severe implications for the

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