The order determines that the Institute for Nature and Forest Conservation (ICNF) promotes the carrying out of an integrated study that “evaluates the ecological and landscape values ​​of this territory, also identifying the main risks and threats to its preservation, proposing strategic guidelines for its safeguarding, in conjunction with local authorities and other relevant entities”.

The study must be presented within nine months and, based on its technical and scientific conclusions, the ICNF must “present a proposal for classification as a protected area”, determines the order signed by the Minister of the Environment, Maria da Graça Carvalho.

The Salir do Porto Dune, in the municipality of Caldas da Rainha, in the district of Leiria, is the largest in Portugal, stretching for around 200 metres in length and 50 metres in height above sea level.

According to historical records, it may have been the largest in Europe and “its size would have been reached around 100,000 years ago with sand from the lagoons that existed between Óbidos and Nazaré”, says the dispatch.

The dune's ecological and scenic value is added to the fact that it is flanked by ruins of the old customs house and shipyards and naval repair workshops where, according to the dispatch, “in the time of D. Afonso V, caravels were built with wood from the Leiria Pine Forest and which were part of the maritime expansion”.

Also nearby is the Chapel of Sant’Ana.

The Salir Dune is located at the mouth of the Tornada River, near the confluence of the bay of S. Martinho do Porto (in the municipality of Alcobaça), constituting “an area that serves as a habitat for numerous species, with emphasis on the abundance of birdlife”.

The ministry highlights in the dispatch that “the pressure of human activities, especially trampling on the dune area, puts this ecological structure at risk” so the natural potential of this territory “must be evaluated in order to take measures for its protection and environmental enhancement”.

In 2021, a resolution of the Assembly of the Republic recommended that the Government safeguard and enhance the dune and the surrounding landscape, with a view to classifying it as a Protected Landscape.

The resolution also recommended that the ICNF, the Portuguese Environment Agency, the National Maritime Authority, the National Energy and Geology Laboratory, the Directorate-General for Cultural Heritage and the Lisbon and Tagus Valley Regional Development Coordination Commission provide technical support to the Caldas da Rainha municipality in carrying out a diagnosis.

Finally, he suggested handing over to the Council the ruins of the old 18th century customs house, so that an Interpretation Centre for the Caldas da Rainha Typhonic Valley could be created there.

In 2023, the Union of Parishes of Tornada and Salir do Porto warned, at the Municipal Assembly of Caldas da Rainha, about the increase in signs of dune erosion.