The amount of biomass found on mussel beds is 2,000 g per m², compared to about 65 g per m² on tidal flats.

The Wadden Sea is one of the most important areas for migratory birds in the world. Around 6 million migratory birds can be found in the Wadden Sea at one time, and an average of 10-12 million pass through it in autumn and spring every year.

The Wadden Sea demonstrates high faunal diversity compared to other coastal wetlands, with over 10,000 species found. The availability of food and the low level of disturbance are essential factors supporting survival of migratory species. Global biodiversity is reliant on the Wadden Sea.

Many of the 140 fish species recorded in the Wadden Sea are visiting from the North Sea. Others use the Wadden Sea as a passage during their migration from the sea to the rivers, as an important nursery area for juveniles or as a spawning area in the North Sea. About 20 species are resident in the Wadden Sea and leave the tidal area only during exceptionally cold winters.