Malltraeth Marsh (also spelled as Malldraeth; or ) is a large marsh area in Anglesey, North Wales, north-east of Malltraeth village, along the flatlands of Trefdraeth, Bodorgan, Llangristiolus and south of Cefn Cwmwd, Rhostrehwfa. It was reclaimed from estuarine marshes after the construction of the Malltraeth Cob (dyke), a long embankment, and the subsequent canalisation in 1824 of the Afon Cefni. The name Malltraeth comes from mall ('bad'), and traeth ('sandy shore'). The marsh measures in area. The area is recognised as a Site of Special Scientific Interest (SSSI), and has a range of reedbeds, marshes, wet grassland and small pools/lakes. History In the Middle Ages the Malltraeth estuary was tidal, stretching as far inland as Llangefni and Ceint. In 1790, an act of Parliament was obtained for more effectually embanking the marshes called Malltraeth and Corsddeuga, under the provisions of which were allotted to the several proprietors of land in the parish of Llangaffo. The of reclaimed alluvium at the mouth of the River Cefni subsequently underwent considerable improvements in the late-18th century and early-19th century with the introduction of embankments and flood mitigation measures. During World War I, further improvements were made due to the concerns of farmers. However the reclamation became neglected and by the end of the war, it had fallen into a bad state and was subject to numerous heated conflicts between the drainage engineer, the CWAEC, and the underfunded catchment board managing the drainage of the marsh. Bitter disputes over the marsh reached a climax with the chairman resigning from the Malltraeth Marsh and Cors Ddyga subcommittee in March 1942 and unusually high rainfall during the harvest in the following year devastating most of the cereal crops in the area. Due to pressure from local farmers, Lord Anglesey met with Robert Hudson and Megan Lloyd George in 1944 to outline ideas for improving the local habitat. Some £100,000 was allocated to developing what was about 50% derelict marsh during the war and by 1947, £147,000 had been spent on the scheme. Geography Located in the cwmwd of Malltraeth, Cors Malltraeth Marsh is on the west side of the Afon Cefni valley which crosses Anglesey parallel to the Menai Straits, approximately to the north-west. The habitat of Cors Ddyga on the east side of Afon Cefni has been reverted to wetlands and reeds. The wetland reserve is officially called RSPB Cors Ddyga. It consists of