Wadden Sea

A vast intertidal wetland along the North Sea coast of the Netherlands, Germany and Denmark, the Wadden Sea is the largest unbroken system of intertidal sand and mud flats in the world, sheltered by a chain of barrier islands and threaded by tidal channels, salt marshes and estuaries. It began taking its present shape only around 8,000 BC, as Holocene sea-level rise drowned the lower reaches of rivers such as the Elbe, Weser and Ems into tidal basins, with wind- and tide-driven sediment then building the barrier islands and mudflats that followed. The site supports roughly 2,700 marine species and at least 5,000 semi-terrestrial and terrestrial species, and serves as a critical stopover for 10 to 12 million migratory birds each year. UNESCO inscribed the Wadden Sea as a World Heritage Site in 2009 under natural criteria (viii), (ix) and (x).