The Parque Natural de las Marismas de Santoña, Victoria y Joyel is the most important wetland on the Spanish Cantabrian coast, covering 6,745 hectares of tidal marshes, estuaries, lagoons, beaches and coastal woodland in eastern Cantabria. It encompasses the estuaries of the Asón and Clarín rivers and the Santoña estuary, forming a shallow-water system with muddy and sandy floors where the tidal range reaches four metres. This cyclical inundation and exposure creates exceptional biological productivity, directly feeding wintering and migratory birds from northern Europe, Siberia and the Arctic.
The Santoña marshes have held Ramsar wetland status since 1993, placing them in the international inventory of wetlands important for waterbirds. The park regularly receives over 10,000 waders and waterbirds at migration peaks, with concentrations of spoonbill, Platalea leucorodia, great egret, Ardea alba, and great cormorant, Phalacrocorax carbo, in the interior channels and pools. In winter, the estuary holds large numbers of shoveler, Spatula clypeata, pintail, Anas acuta, and teal, Anas crecca. Marsh harrier, Circus aeruginosus, hunts over the reedbeds and is visible in low flight throughout the year. Common tern and Sandwich tern are present during spring and summer migration.
Intertidal seagrass meadows of Zostera noltii and Zostera marina cover thousands of square metres on the marsh floor and form the base of the wetland food chain. Canal banks are edged with common reed, Phragmites australis, and sea rush, Juncus maritimus. On the upper marsh, above the reach of ordinary high tides, halophyte communities including Spartina densiflora, Salicornia europaea and Limonium vulgare paint the high-marsh strips lilac and grey-green in summer. Sections of coastal woodland within the park — Peña Ganzo, Monte Buciero — carry holm oak and laurel forest that contrast with the horizontality of the marsh and offer elevated viewpoints from which the entire system can be read in a single glance.
Monte Buciero, closing the estuary from the north, is itself a site of considerable botanical and cultural interest. Its position at the estuary mouth, Atlantic-exposed on one side and sheltered on the other, creates a variety of microclimates reflected in its flora. Remains of the San Martín coastal battery and a medieval castle add a historical layer to the whole. From the Buciero summits (224 m), the view takes in the full estuary, the town of Santoña, the Berria dune bank and the coastline to Laredo. The anchovy of Santoña, fished and artisan-processed in spring, carries a protected geographical indication and its production follows the rhythm of anchovy migration through the Bay of Biscay.
