The Netherlands is a country in northwestern Europe with overseas territories in the Caribbean. The country is home to 21 national parks and numerous nature reserves, most of which are owned by Staatsbosbeheer, the National Department of Forestry and Nature Conservation, and Natuurmonumenten, a private group that purchases, defends and manages nature reserves. The Wadden Sea, located in the northern part of the country, is a UNESCO World Heritage Nature Site known for its biodiverse mudflats and wetlands. The Oosterschelde, formerly an estuary of the Scheldt, is the largest national park in the Netherlands, covering an area of 370 square kilometers. The Dutch plant species mainly belong to the Atlantic district within the Euro-Siberian phytogeographic region. Vegetation in coastal sand dunes, muddy coastal areas, brackish lakes and river deltas is particularly unique in comparison to the surrounding countries. Inland vegetation is influenced by soil factors such as clay, peat and sand. Animal life in the Netherlands is classified based on region and vegetation. The Wadden Sea and the extreme southwest are rich in seabirds, marine life and mollusks. The country is also a hub for migratory birds, with many species passing through or staying the summer or winter. Waterfowl, marsh birds, and grassland birds are common. Larger mammals like Roe Deer, Red Deer, foxes and badgers are mostly found in nature reserves, while species like Wild Boar, beaver, Fallow Deer, mouflon and muskrat have been introduced or reintroduced. Some reptiles, amphibians, river fish and lobsters are threatened or rare due to factors like water pollution.