Laguna Madre. 02/02/04; Tamaulipas; 307,894 ha; 24°44'N 97°35'W. The largest water body in the country, on the Gulf of Mexico near the Texas border, it is a coastal lagoon system bordered by a sand barrier 223km long. Salinity varies greatly depending on rainfall. The site is of critical importance to resident and migratory waterbirds, especially shorebirds such as Pluvialis squatarola, Calidris alba, Calidris minutilla and the endangered Piping Plover Charadrius melodus. 26 waterfowl species are found on the lake, where concentrations of over 100,000 individuals of Redheads Aythya americana and Northern Pintail Anas acuta stand out. Desert scrub of mesquite Prosopis glandulosa, Blackbrush Acacia rigidula, Castela tortuosa, amongst others, is the most representative terrestrial vegetation. Seagrass beds of Halodule wrightii and others cover large areas. Fishing is by far the most important human activity on the site, yet the over-exploitation of resources has diminished stocks. The Intracoastal Waterway project from Tampico to Brownsville would seriously alter the site's character. The area is regarded as the first priority wetland for migratory birds in Mexico by Ducks Unlimited, which contributed towards the site designation. Ramsar site no. 1362. Most recent RIS information: 2004.