This site is located at north bank of Tejo Estuary. Is formed by two salinas (salt pans) complexes: Salinas de Alverca and Salinas do Forte da Casa, extensive agricultural landscapes that separe them, and the final part of Verdelha river; it represents the only bird refuge in this riverbank. In the surrounding zone, the strongly built up and industrializated area of Alberca contrasts with the Natural Reserve of Tejo Estuary and Portuguese Air-Force installations. Besides the salinas banks and landscapes, there are also drainage trenchs and a stream with an important water fringe vegetation. Now, salinas are abandoned and water lever is conditioned by precipitation. Vegetation inside the banks is mainly constituted by aquatic plant, namely rushes and reeds. In the edges salt-marshes vegetation and rarely tamarisks are found.
The salinas of Alberca and Forte da Casa costitute one of the most important nesting site in Tejo Estuary for aquatic-birds like Himantopus himantopus whose colonny could ever hold thousands of breeding pairs. This is the only nesting place of Netta rufina in estuary. Circus aeruginosus, Recurvirostra avosetta, Glareola pranticola, Sterna albifrons and also Ixobrichus minutus, Anas strepera, Fulica atra are present here in significative numbers. The whole zone is important as feeding area for Ardea purpurea and C.aeruginosus who breed in Natural Reserve; and also for passerines and waders during wintering or migration seasons.
Pressure/threats to key biodiversity
Part of the area was included in the National Ecologic Reserve, not now. The whole area is highly threatened by infrastructures namely a sewage-farm, a housing and respective gateways. The absence of management and the abandonement of the salinas, make the site short of its birdlife potential. Industrial and domestic pollution is mainly negative, significantly affecting Verdelha river and drainage trenchs. Garbage and ruins dumps are also visible. In the whole agricultural area hunting is avoid, beeing an important threat and a main disturbance to birds. The presence of people and four-wheels in specially sensitive areas (like banks) could be negative for some species nesting.