Designated in 1975

Located in the far south-east corner of Portugal, the Nature Reserve spreads over a large flat area with a minimum altitude of bathymetric 2.5 m. It consists of alluvial plains in the wetland of the Guadiana estuary, seaside dunes (the National Dune Woods of Vila Real de Santo António), and areas of sand and pebbles. The area is characterised by a complex system of channels, inlets, salt marshes and salt-works, which allow the influence of the tides to reach the whole Nature Reserve. In the salt marshes, we find cord grass Spartina maritima, part of the halophyte vegetation adapted to the high salt content of the soil. Being a refuge and nursery for a great number of fish, shellfish and bivalve molluscs, this area has great international importance for many birds, such as the black-winged stilt Himantopus himantopus, Kentish plover Charadrius alexandrinus, avocet Recurvirostra avosetta, little tern Sterna albifrons, white stork Ciconia ciconia and flamingo Phoenicopterus ruber. We should also mention the chameleon Chamaeleon chamaeleon, which, in Portugal, can only be found along the Algarve coastline and has its greatest population in these woods. The areas surrounding the wetland contain numerous species of the ancient Mediterranean forest, such as cork oak Quercus suber, holm oak Quercus rotundifolia and dwarf fan-palm Chamaerops humilis.
Castro Marim village near the mouth of the river Guadiana, one of the oldest in the Algarve, has evidence of a very early human presence in the region, the result of the region’s natural wealth and its strategic military importance and advantageous position for trade. Archaeological remains confirm the presence of humans in this area since the Bronze Age, like the castros and Roman paths, the castle (16th century) and the fort of S. Sebastião (18th century). From ancient to present times, farming, fishing and salt extraction have been traditional economic activities in the region.