extent in August eelgrass covers up to 13% of the North Frisian Wadden Sea. Eelgrass areas provide habitats for marine organisms and are an important food source for barnacle geese (Branta leucopsis). Salt marshes are the dominant landscape in the transition zone between open sea and inland. They are regularly flooded between 10 and 250 times a year depending on the tidal range. Salt marshes build different zones relative to the local salinity. The lower marsh zone which is flooded the most has a higher salinity than the upper marsh zone which is less frequently flooded because of the higher elevation. In total about 50 species of flowering plants can be found in the local salt marshes. In low elevation areas plants like common salt marsh grass (Puccinellia maritima), sea-aster (Hordeum marinum), sea-blite (Sueda maritima) and sea-purslane (Halimione portulacoides) are characteristic. High elevation areas are a lot more diverse in plant species. Common plants are seaside centaury (Centaurium littorale), red eyebright (Odontites rubra), see plantain (Plantago maritima) and distant sedge (Carex distans). In the dunes small amounts of plants can be found; due to the extreme conditions only some dune heaths grow there. The rain-laden dune valleys resemble the vegetation of a marsh, with plants like cotton grass (Eriophorum angustifolium), drosera or marsh gentian (Gentiana pneumonanthe). Animals Mammals A great number of harbour porpoises live in the national park. The Wadden Sea is also home to harbour seals and grey seals. According to the official counting of the National park Administration, about 13.000 harbour seals are living in the Wadden Sea of Schleswig-Holstein (2017). Nearly half of the seal population died during the "Seehundstaupe" epidemic in 1988 and 2002. The National Park Administration assumed that one third of the harbour seal population was swimming or hunting during the counting so the number had to be adjusted. The grey seal population consists of 140 animals and is mainly located on the "Jungnamensand" sand bar and the "Knobsand" sand bars near the island Amrum. Insects The Wadden Sea only has a few places where insects are found. Nearly all of the 2000 highly specialized species which are known to live in the national park can be found in salt marshes. Due to the difficult environmental conditions (for example salinity or frequent flooding), it is hard to survive for insects, especially in the larval state. The main survival strategy is hiding in the