The reserve is one of the few places in Portugal where the salt-making process has remained virtually unchanged since the Roman era.
It is a designated Ramsar site, identifying it as a wetland of international importance.
The high salinity of the salt pans encourages the growth of Artemia salina, a brine shrimp that gives flamingos their characteristic pink coloration.
The reserve spans across the borders of the municipalities of Castro Marim and Vila Real de Santo António.
The Guadiana river estuary marks the natural border between Portugal and Spain.
The reserve's ecosystem is classified as a Special Protection Area (SPA) for wild birds.
The Castro Marim and Vila Real de Santo António Marsh Natural Reserve covers approximately 2,000 hectares of wetlands, salt pans, and lagoons along the Guadiana River estuary. Established in 1975, it was the first nature reserve created in Portugal. The habitat supports over 150 species of birds, including significant populations of greater flamingos, avocets, and spoonbills. The landscape is dominated by traditional salt pans, where salt production has been an economic activity for centuries. Freshwater, brackish, and saltwater environments coexist within the reserve, creating a unique biodiversity hotspot. The reserve serves as a critical nesting and migratory stopover point on the Atlantic Flyway. Much of the vegetation consists of halophytic plants adapted to high salinity levels. The area is intersected by several walking trails that provide access to both salt marshes and agricultural lands.
The elevated observation decks overlooking the geometric salt pans during the golden hour.
Bring binoculars as the best wildlife observation points are often distant from the main trails.
Apply sunscreen and bring a hat, as there is almost no natural shade throughout the exposed marshlands.
Check the tide charts before visiting, as high tide can submerge lower-lying sections of the footpaths.
Attempting to walk through the muddy areas near the water's edge, which can be unstable and damage the salt pan infrastructure.
Maintain a quiet distance from bird nesting areas, stay strictly on marked paths to protect fragile salt-crust soil, and refrain from feeding wildlife.
