The history of the salt marshes | Destination Île de Ré

The history of the salt marsh

Salt marshes are landscapes that have been shaped by human activity for centuries to produce salt from seawater. Their origins date back to the Gallo-Roman period, around the 1st century. It was mainly along the French Atlantic coast that salt marshes subsequently developed. From the very beginning, this system relied solely on the natural energy of the sun and wind, making it a sustainable method ahead of its time.

In the Middle Ages, salt production became a major economic activity, essential for preserving food. Salt workers have passed down their traditional skills from generation to generation. Today, salt marshes represent a living heritage, often maintained using traditional and sustainable methods.

Today, salt marshes are not only places of production, but they are also protected natural areas rich in biodiversity. Salt harvesting here remains a manual and sustainable process, which gives traditional salt, such as coarse salt or “fleur de sel”, a quality and purity that are highly sought after.

Did you know?

The difference between coarse salt and “fleur de sel”

Coarse salt (or grey salt) is found at the bottom of the ponds where salt crystallizes.
“Fleur de sel” is the fine white layer that floats on the surface.

Birds

Salt marshes are not just places of production: they are also true havens for wildlife. They serve as breeding grounds, stopover points and wintering grounds for many waterbirds.

Pied Avocet
An iconic bird with a long, upward-curving beak.
Grey Heron
Lying in wait in the marshes or on the ridges, it feeds on both aquatic and terrestrial wildlife, particularly field mice.
Blue-Throated
A discreet little bird that fills the marsh with its melodic song in spring.
Common Shelduck
One of the few ducks whose female plumage is practically identical to that of the male. It nests in the shelter of thickets or rabbit burrows.
Black-winged Stilt
Large red-legged crayfish, commonly found in the shallow ponds of the salt marches in spring.
Little Egret
A small white heron that nests in trees in the forest but feeds on small fish and shrimp in the marshes.
European Herring Gull
An increasingly rare breeder in marshes, this iconic seashore bird should not be confused with the black-headed gull.

Other marsh animals

Artemia and eels
The iconic species of this habitat is the eel, which lives in mudflats. Artemia (Artemia salina: species of brine shrimp), which is adapted to hypersaline environments, is also found there.
Midge
Like mosquitoes, midges are an important source of food for birds, whether in larval form for avocets and stilts, or in their adult form for passerines such as the bluethroat and the common bat.
Bats and foxes
May also hunt in the marshes.

The structure of a salt marsh

Each of the six ponds has a specific role: settling, concentration and crystallisation. Each stage facilitates the formation of salt crystals.

Pond 1 – The seawater inlet
(the channel)

This is the inlet channel (often referred to as the ‘essai’) that carries seawater into the marsh. The water flows in at high tide and is then directed into the ponds via gate valves.

Pond 2 – Mudflats or silt flats

These are the first ponds where seawater settles. Silt and sand particles settle here, making the water clearer. This is a pre-treatment stage prior to evaporation.

Pond 3 – The evaporation ponds

The water begins a long journey; warming and evaporating under the action of wind and sun.

Pond 4 – The salt pans

The water then flows into the salt pans, which form compartments where the salt continues to concentrate.

Pond 5 – The evaporators

The water then flows into these intermediate ponds. Here, it heats up and evaporates slowly, increasing its salt concentration. The main purpose is to gradually concentrate the brine.

Pond 6 – The crystallisation ponds

These are the small final ponds where the salt crystallises under the influence of the sun and wind. This is where coarse salt and “fleur de sel” are harvested.

The canals and lock gates

These are used to regulate the flow of water between the different ponds. Salt producers open or close the locks to control water levels and salt content.

Pathways and dykes

They mark out the ponds and allow the salt worker to move around and maintain the salt marsh. The dykes prevent flooding and protect the working areas.

Typical plants

The vegetation is adapted to salt and moisture: these are halophilic plants (which tolerate salt).

Salicorna
Known as the “sea pickle”, an edible plant with a salty taste.
Obione
A shrub with silvery leaves. A plant with roots anchored in the salty mud, growing at the edge of the marsh.
Sea aster
A salt-tolerant purple flower also known as “pig’s ear”. It grows on the upper parts of the salt marsh and in the less salty areas of the marsh.
Suaeda maritima and common sea-lavender
– Suaeda Maritima: grows on the edges of marshes or on deposits of salt mud and has no visible flowers.
– Common Sea-Lavender: several species grow in the marshes, but the largest is generally harvested, preferably in moderation.

Their ecological role

These plants stabilise the soil and filter water. They provide shelter and food for birds and insects. They help maintain the balance of the marsh ecosystem.