The Wadden Sea, a 450 km coastal wetland along the North Sea coasts of Denmark, Germany, and the Netherlands, is one of the largest continuous tidal flats in the world and one of the last areas in Europe where nature can still develop to a great extent without human influence. To preserve this unique ecosystem, the German coastal states declared it as National Parks and, moreover, the Wadden Sea in Schleswig-Holstein, Lower Saxony and the Netherlands was placed on the UNESCO World Heritage List in 2009. It forms the transition zone between the North Sea and the mainland and is characterized by large changes in water coverage due to the semi-diurnal tides.
The Wadden Sea is a highly dynamic area with habitats comprising tidal channels, sandbars, mudflats, and saltmarshes. Its physical characteristics provide the base for a high primary productivity, which in turn leads to a high biodiversity and makes the Wadden Sea an important site for bird migration.