The salt marshes are the result of human action, in search of an ancient remedy: salt. In essence, how the Mediterranean salt marshes work is simple: it consists of the progressive concentration of sea water, stored in large shallow ponds where evaporation eliminates the liquid. This continues until the concentration gradient necessary to induce crystallization sodium chloride is reached.
The salt marshes are located in low and flat coastal areas, usually at levels at or below sea level, which can draw water directly or with little energy expenditure. They appear divided in deposits, large pools or evaporators, which often have gaps between them, allowing the direct passage of water through gates. The soil is of clay, which helps prevent the loss of stored water.
The traditional salt marshes, given their ecological, environmental, cultural and ethnographic interests, have been listed by the European Union (EU) as an ecosystem of community interest. Moreover, they constitute a clear example of sustainability and being environmentally friendly, which has allowed the proliferation of biological communities and species, such as stilt adapted to peculiar conditions with progressive increases in salinity, semi-permanent or shallow waters, high productivities, etc.
The Isla Cristina salt marshes date back to Roman times. Used for the conservation of fish, they were originally the most characteristic industry within the area. Their greatest economic splendour was from the mid-nineteenth to the mid-twentieth century, when they came to occupy 30% of the marshes territory. It is currently much lower. The Vista Hermosa Salt Marshes, Manna Salt Marsh and Biomaris Sea are currently still in operation. The latter offers the possibility to visit and observe the artisanal extraction of the Flower of Salt (Fleur de Sal, Flor de Sal)
In the Odiel Marshes Natural Park one can find the industrial Aragonesas salt marshes where salt extraction is mechanized. It is also home to the Bacuta salt marshes where salt is traditionally extracted through the action of the sun and the wind. Isla Cristina - Huelva, Natural Park of the Odiel Marshes