Straddling the municipalities of
Isla Cristina and
Ayamonte, between the mouth of the River Guadiana and
that of the River Carreras, lies the Isla Cristina Salt
Marshes Area of Outstanding Natural Beauty, measuring 2,145 hectares. These are tidal marshes of high ecological value, because in them birds either usually live, or
breed, or spend seasons.
Although some areas are occupied by salt flats, they're populated by shrubby glasswort, cordgrasses, bulrushes, common reeds and rushes, stone
pines, Aleppo pines, savin juniper trees, broom, sea rockets, and sand stocks. In them you can find molluscs such as razor clams; a few crustaceans; fish such as sea
bass, eels or sole; and birds such as little egrets, white storks, black-winged stilts, terns, dunlins, flamencos, Kentish plovers, avocets, spatulas, purple
swamphens, shovelers, cormorants, lesser black-headed gulls, yellow-legged gulls, and birds of prey such as ospreys.
This area of outstanding natural beauty also has a wealth of fish, and in it stands an 18th-century tide mill.