The marshes form part of the open coastal fen landscape type within Suffolk which is predominantly open with few trees.[11] They were drained for use as cattle grazing at some point before 1587 but have reverted to fen land after mid-20th century reflooding.[11]
Habitat
The marshes include a mixture of coastal and freshwater wetland habitats, including brackish pools.[12] These provide breeding habitats for birds such as bitterns, marsh harriers and bearded tits as well as mammals such as European otters and water vole and over-wintering locations for species such as pied avocets, white-fronted geese, northern lapwings and redshanks.[1][3][12] The site is an internationally important habitat of the starlet sea anemone, the rarest sea anemone in Britain.[1][3] The reserve is bordered by heathland and forest on the landward side and includes a vegetated shingle bank on the seaward side. Little terns often nest along the bank.[12]
Flooding
Coastal flooding has affected the marshes in recent years, including in 2003, 2006 and 2007.[13][14] The shingle bank was breached in 2006 and 2007 leading to concerns that vulnerable freshwater habitats could be lost, including the breeding grounds of species such as bitterns.[13][14][15] Emergency flood defence works were carried out by the Environment Agency following the 2006 breach,[15] and these were extended in 2012 to provide additional flood defences for the reserve.[16]
Facilities
The reserve is accessed from the south at Dunwich beach where a car park and other facilities are maintained by East Suffolk council. A circular walk is waymarked around the marshes. The RSPB maintains a hide overlooking the marsh.[12]