Nematodes of the
	Formation	Fens, are peat-forming wetlands that receive nutrients from sources other than precipitation: usually from upslope sources through drainage from surrounding mineral soils and from groundwater movement. Fens differ from bogs because they are less acidic and have higher nutrient levels. They are therefore able to support a much more diverse plant and animal community. Over time, peat may build up and separate the fen from its groundwater supply. When this happens, the fen receives fewer nutrients and may become a bog.
	Benefits	Fens, like bogs, provide important benefits in a watershed, including preventing or reducing the risk of floods, improving water quality, and providing habitat for unique plant and animal communities. Like most peatlands, fens experienced a decline in acreage at a rate of about eight percent from 1950 to 1970, mostly from mining and draining for cropland, fuel, and fertilizer. It is important to recognize that while mining and draining these ecosystems provide resources for people, up to 10,000 years are required to form a fen naturally.
	Preservation  qualities	Fen and bogs are areas of soft, waterlogged land, usually containing large amounts of organic acids and aldehydes in layers of Sphagnum and peat. This environment often acts to preserve the soft tissues of a cadaver even after the bones have dissolved away; such things as skin, eyes, intestines, brains and hair are sometimes so well preserved as to appear almost modern. First, the bog-watery environment does not permit the growth of bacteria that will help decay flesh. Second, the bog water contains certain acids that act to tan the skin (much the same way as cowhide is tanned to produce leather). If the natural bacteria action is prevented and the skin is tanned, the conditions are right for producing a mummy. One such human bog-mummy is the Grauballe man of Denmark. Similarly mummified nematodes have been found in the peat from Jumbo Valley fen in the Nebraska sand hills.