The marshes originate in calm water coastal areas. The low tidal flow facilitates the deposition of debris and suspended sediments, thus creating mud banks where, at some point, there is substrate for vegetation. The colonization is pioneered by a Spartina grass (in Ria Formosa, S. maritima), which withstands long periods of submergence and, therefore, settles in lower areas, where it forms vast dark green meadows. in the middle of the waters, which constitute the low marsh or parchal Once established, vegetation dampens the force of the stream and sedimentation accelerates; At the same time, by removing moisture from the vessels through the root system, it consolidates them. Where the substrate is less resistant to the erosive action of the waters, the typical canals and ditches that form the marshland in a dendritic tangle form. The continuous accumulation of sediment considerably raises the level of the bottoms, with a consequent reduction in submersion time and salt content. The end result is gradual changes in vegetation, in a succession that will lead to the zonation observed in the marshes. Still in the lower marsh but on slightly higher bottoms, Spartina may appear accompanied by Arthrocnemum perenne, alone or in association with other Quenopodiaceae such as Salicornia nitens, Suaeda maritima and Halimione portulacoides, and a Plumbaginaceae, Limonium algarvense, which constitutes an Algarve endemism. In the middle marshland, the previous species are gradually being replaced by Sarcocornia fruticosae Arthrocnemum macrostachyum and, finally, Suaeda vera. It is evident that, depending on the location, there is some variation in floristic composition. Large portions of the high marsh border appear dominated by another Plumbaginaceae, but in this exotic case, Limoniastrum monopetalum, which forms dense thickets in which the pink-lilac color of the flowers, gathered in abundant ear, stands out.