The French Marshes along the Atlantic Coast

The Atlantic coast gives you the opportunity to discover different astonishing natural marshes. All along the western coast of France, these authentic, preserved salt marshes and swamps offer you incredible views and interesting elements about the French fauna, flora and history.

The Mont Saint Michel


The famous Mont Saint Michel is a rocky tidal island connected to the Lower Normandy region of France, about one kilometre away from the French North coast, at the mouth of the Couesnon River near Avranches. The bay shared by Normandy and Brittany received the name of the authentic Saint Michael's Mount which has been part of the UNESCO World Heritage Sites since 1979, making the pride of both Breton and Norman people!


In prehistoric times the bay was covered by the sea. Water had been retreating over many years and erosion eventually formed the Northern French coastal landscape. Some massive blocks of granite emerged in the bay, having resisted the ocean's activity when the surrounding rocks collapsed. Such small mounts included Lillemer, the Mont-Dol, Tombelaine and Mont Tombe, later gathered up into the "Mont Saint-Michel".

Dangerous tides

The tides in the Saint Michael's Mount area are considered dangerous because they change very quickly, described by the famous French writer Victor Hugo as changing à la vitesse d'un cheval au galop ("as swiftly as a galloping horse")!

The tide can actually move forward at one metre per second, causing about 14 metres between the highest and lowest water marks. It is not surprising then that the French mount used to be called "St. Michael in peril of the sea" by medieval pilgrims! Tides in the Mont Saint Michel area indeed still cause damage, especially during the tourist overflow in summer, when visitors do not pay enough attention to the currents.

Even for the most athletic of you, walking across the sandy marshes to join the mount is actually quite dangerous; every year, some people get trapped by coastal tides or quicksands.

Brière Marsh


Brière is a French marsh area situated at the North of the Loire estuary. Briere area includes vast wetlands from the Gulf of Morbihan in Brittany to the salt marshes of Guérande in the Pays de la Loire region, to the mouth of the Loire River in the Atlantic Ocean. The Brière area - commonly called Grande Brière - streches over 490 square kilometres, including 170 km² of swamps.

This Western coastal area is appreciated for its rich flora and fauna, but also for boating (with exclusively small pleasure boats called chalands).

Breton-Vendéen Marsh


The Breton-Vendéen marsh represent wetlands located on the Atlantic French coast. Forming originally the border between the Brittany and Poitou former provinces, this vast marshland now stretched over the Loire-Atlantique and Vendée departments of Pays de la Loire.

The Marais Breton Vendéen is surrounded by protected by dykes and dunes which actually serve as protection - a plus for sea salt exploitations (especially around the Noirmoutier island). Biodiversity is also an important characteristic of the Breton-Vendéen marshes.


Until the XVIII century, this marsh was very famous for its salt marshes (the first in France!). Unfortunately, silt piled up and the boats were not able to access to the harbour. Thus, they modified their activity and arranged the territory (with coastal defences to evacuate the sea salt) to develop agriculture.


Today, the main activity is tourism thanks to attractive seaside towns such as Saint Jean de Monts, Notre Dame de Monts, Les Moutiers en Retz, and to the lovely Ile de Noirmoutier. The Western region is also appreciated for the traditionally produced oysters and salt.

Olonne Marsh


Olonne marshes formed around the French towns of Olonne sur Mer, Les Sables d’Olonne, l’Île d’Olonne and Vairé, in the South of the Pays de la Loire region. Such vast swamp lands have been for a long time exploited for salt, fishing and oyster farming. Nowadays, many local producers keep on using authentic methods, which makes the Marais des Olonnes area well-known.

The discovery

These Western wetlands host many migratory birds - you can sometimes catch sight of them in the stretched marsh areas that offer a wide range of protected plants.

Tourism is now a valuable way to develop the Olonne marsh's activity. Exceptionally calm, this region is indeed highly appreciated by nature lovers who fancy hiking, boating or horse riding.

The Marais Poitevin


The Poitevin Marsh, also known as the Venise Verte (Green Venice) or Marais Poitevin, includes wetlands in the former Gulf of Poitou region. With a surface area of 970 km², the renowned Marais Poitevin is the largest marsh on the Atlantic French coast.

Situated at the north of La Rochelle and the south of the Vendée department, those wetlands were turned into a Regional Natural Park in 1979, but this quality status was finally removed in 1996 because of too intensive agricultural activity.


The Poitevin Marsh is split in two lands: the dry marsh and the wet one.

The dry marsh actually contains water, its name originates from the fact that there is only enough water to provide irrigation. It is not surprising that you will only see large and high fields of corn and sunflower there. During heavy rains, the "dry" marshland can be flooded, and in that case, the wet one is to capture the excess water to avoid damage (hence its name in fact). This second part of the Marais Poitevin is indeed flooded for the most of the year; nonetheless in summer, when the levels go down, you can have the chance to use the thousands of kilometres of waterways for pleasant, tourism activities.


The Poitevin Marsh is a remnant of the former Gulf of Poitou. This swamp of the French West coast was originally completely covered by the Atlantic Ocean. As the sea level dropped over the centuries, the level of the surrounding rivers'mouths also was increasingly lower, causing excess waters in that region of the West coast.

In the 7th century, local monks dug waterways to evacuate waters and drain some lands to enable exploitation. They also built dykes to protect the dry marsh against the floods.

Nowadays, these two distinctive marshes still ensure the main activities of the region, agriculture and tourism.

Fauna and Flora

The inhabitants used to fish eels, but unfortunately the fishing on the French coast has been too intense and the species is gradually disappearing. The coypu is also a serious matter; as it destroys the banks of the marshes, this mammal is today widely hunted in the region.

The Poitevin Marsh is one of the most important areas in France in terms of biodiversity. The best way to discover it is during pleasure boat trips; you may really take the most of the multiple canals covered with green moss (hence the nickname "Venise Verte").


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