FEN is a type of wetland habitat that is characterized by low-lying areas filled with water and vegetation. It is also known as a swampy bog, which is a type of wetland that is often found in areas with poor drainage. The water in a FEN is usually stagnant and the vegetation is typically composed of grasses, sedges, and other marsh plants. Fens are important habitats for many species of wildlife, including amphibians, reptiles, birds, and mammals.