Disappearing or diminishing populations of whelks have been observed since the early 1970s, especially in the North Sea and the Wadden Sea.
The German part of the Wadden Sea was the setting for the 1903 Erskine Childers novel The Riddle of the Sands.
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Large and well-developed meadows can primarily be found in the Wadden Sea, Limfjord and Isefjord areas and on the islands of Læsø and Lolland, but there are many other smaller beach meadows throughout this lowlying country.
Mellum formed as an island off the end of the Butjadingen peninsula – which divides the outflows into the Wadden Sea of the Jade and Weser rivers – only at the end of the nineteenth century.