Pays de la Loire

Marais Breton-Vendeen and Baie de Bourgneuf

This page was updated on: Friday, January 10, 2020 at: 11:29 am

What is the Marais Breton-Vendeen?

The Marais Breton-Vendeen is a vast natural wetland situated between Brittany and Poitou.

It extends over 45,000 hectares, mostly at sea level, distributed in the departments of Vendée and Loire Atlantique.

The Marais Breton-Vendeen is part of the Baie of Bourgneuf.

This vast bay stretches from Pointe Saint-Gildas, near the Loire estuary, to Beauvoir-sur-mer to the south.

The sea once covered the whole region and the sites of Bouin, Sallertaine and Beauvoir were then islands.

Noirmoutier is the only remaining of these islands.

The alluvial deposits of the Loire and Charente gradually reclaimed land from the sea and created the Baie de Bourgneuf.

Their accumulation eventually caused the siltation of the bay.

This zone, however, remained at sea level.

It thus flooded at high tides and isolated the many islands and islets.

The salt marshes in the Marais Breton

The Romans built the first dikes and created the first salt marshes some 2000 years ago.

The Benedictine monks extended the network of pits and canals and developed the Marais Breton-Vendeen between the 11th and 13th centuries.

They turned the local salt production into a thriving industry.

By then, the sea still covered part of the bay.

The towns of Bourgneuf-en-Retz and Beauvoir-sur-Mer were therefore sea ports as they were located on the littoral!

So were Challans and Machecoul, today located 20km inland.

Bouin and Bourgneuf, the main local salt producers, shipped most of their salt to the Nordic countries.

Demand for salt was very high during the Middle-Ages because it was mainly used for preserving meat and fish.

The Marais Breton-Vendeen then produced 300,000 tons of salt per year.

It remained the largest salt producer in Europe from the 15th to the 18th century!

Decline in salt production and conversion of the salt marshes

Natural siltation was amplified by the tons of bilge ballast the vessels dropped before loading the salt.

This ultimately prevented them from accessing the ports and consequently led to the decline of the local salt production!

The salt marshes were consequently converted for agricultural activity.

However, some areas of the marsh were below sea level.

A network of canals (étiers) and locks was therefore put in place in order to send salty water back towards the sea and replace it with rain water.

As a result, the Marais Breton is today essentially made up of fresh water.

A vast network of dykes as well as dunes planted with pines, such as the Forêt des Pays-de-Monts, shelters it from the sea.

The good news is that the salt marshes are gradually redeveloped because of the growing demand for natural and tourist products.

A protected natural wetland

The Marais Breton-Vendeen is also part of the Natura 2000 programme.

This natural wetland attracts a rich fauna that includes ducks, herons and egrets, but also storks!

The flora is of course mainly represented by  species that thrive in salty soil (halophyte) such as salicornia and obione.

The Marais Breton, Baie de Bourgneuf and Ile de Noirmoutier are now registered on the Ramsar list of wetlands of international importance*.

This global label rewards and enhances sustainable wetland management actions.

You’ll enjoy discovering the natural and historical heritage of the marsh by visiting the Ecomusée du Marais Vendéen, Le Daviaud.

Coordinates: Lat 46.850793 - Long -2.053546

*https://www.ramsar.org/document/the-list-of-wetlands-of-international-importance-the-ramsar-list
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