The Poitevin marshes is a natural region of France located in the regions of Nouvelle-Aquitaine and Pays de la Loire. Spread over the departments of Vendée, Deux-Sèvres and Charente-Maritime, the Poitevin marshes, also known as the “Green Venice”, together with the Bay of Aiguillon, form a regional nature park covering nearly 100,000 hectares. Developed by man since the 11th century, marshes are composed of three main areas linked to its hydraulic functioning: the maritime marsh, the dry marsh and the wet marsh. In this article, we will look at the history of the marshes and the development of this natural region made up of kilometers of canals and rivers and home to a wide variety of flora and fauna, including many rare or threatened species.
The history of the Poitevin marshes and its development
In Gallo-Roman times, it is estimated that the tide went up to Marans, on the side of the Sèvre Niortaise, a river that crosses Niort, as well as on the side of the Vendée. The region is also famous for its exploitation of sea salt, called “salt of Poitou”. From the 7th century, the great feudal lords proceeded to concessions and donations of parts of the marsh to local abbeys, such as the abbey of Maillezais or the monastery of Luçon. Works of development of the marshes are carried out in order to optimize the productivity of the cultures, the breeding, the fishing and to develop the activity related to the salt marshes. From the end of the 10th century, works of dyking of dried marshes are carried out in order to exploit more easily the lands of the region. In 1189, the Bot-Neuf canal, today called the Clain canal and 14.2 kilometers long, was dug by the abbot of Moreilles. The canal of the 5 abbots, intended to dry the marshes of Langon and Vouillé, was dug between 1200 and 1217. Later on, other large evacuation canals were also dug.
Under Henry IV, the work of draining the Poitevin marshes intensified, supervised by Humphrey Bradley, a Dutch engineer specialized in hydraulics. Under the impetus of Pierre Siete, the first marshland syndicates, composed of groups of owners, were created in the 17th century. The “contrebot de vix”, one of the longest canals in the Poitevin marshes, was dug in 1662. Similarly, aqueduct works are implemented in order to improve water management, and in particular the evacuation of water from wet marshes. By the end of the 17th century, the dry and wet marshes were completely dependent on each other.
Development of the wet marshes
In 1808, Napoleon I decreed the development of the Sèvre Niortaise in order to make the river navigable, a period that marked the beginning of a campaign of major works that would last for nearly a century. The French revolution and the creation of the departments artificially divided this space between the Vendée, the Charente-Maritime and the Deux-Sèvres. Important works to improve the discharge of water to the ocean during floods are carried out, as well as widening, straightening and deepening of some canals. However, these canals, which were specially built for navigation, were only rarely used for maritime transport, which was competing with the development of rail transport in the Poitou region. In the 1960s, major hydro-agricultural works were carried out (consolidation, creation of new spillways, recalibration of canals…). The wet marsh disappears around the river Vendée. In 1975, the elected officials mobilized to create a mixed syndicate intended to take into account the problems of development respectful of the environment on the Poitevin marsh, the valleys of the catchment area and the forest massifs around. The regional natural park of the Poitevin marshes is thus born. However, the forced draining of the Poitevin marshes has an impact on biodiversity, especially on more than 250 species of birds.
The typology of the marshes of the natural park of the Poitevin marshes
Unlike wet marsh, the term desiccated marsh does not mean that the marsh no longer has water, but that in theory it is no longer floodable. Similarly, there can be no dry marsh without a wet marsh, the latter allowing the regulation of water inflow from the watershed to avoid flooding. In fact, the dried marshes are artificial areas surrounded by dikes that protect them from both the sea and the watersheds. Dependent on flooding, the wet marsh has allowed the development of short-cycle crops, such as the famous mogettes (white beans) whose cycle is three months.
The natural marsh has been developed by man. It is supplied with fresh water by the rivers and coastal streams of the Sèvre Niortaise, Vendée and Lay watersheds. Complex, these channels are similar to those of the blood vessels of the human body. Thanks to a subtle management of fresh water, the natural marsh requires the evacuation of the overflow of water in case of flood, as well as the regulated feeding in periods of drought.
The fauna and flora of the marsh
As the marsh is artificially drained, regular maintenance is necessary. The banks must be consolidated to prevent them from collapsing and the ditches must be regularly cleaned to prevent them from silting. This is why many species of trees have been planted for the biodiversity of the Poitevin marshes.
- Poplars: the numerous poplars of the Poitevin marshes help to structure the landscape. The poplar named “blanc du Poitou” is traditionally the most sought-after species of poplar, although today it is little used.
- Ash trees: ash trees are pruned in pollard, that is to say regularly pruned so that the height of the trunk does not exceed two meters. The cut branches are used as firewood. The stubby roots of ash trees also help to maintain the banks.
- Willows: Willows are found mainly along stream edges and some produce wicker.
We also find other tree species such as the common hornbeam, the black poplar, the white willow, the pedunculate oak or the maple or the country elm.
The name “Green Venice” comes from the duckweed, a floating aquatic plant found in wet marshes. The Poitevin marsh has no less than six species of duckweed. There are also prairie plants, coastal plants, aquatic plants, shoreline plants and dune plants.
The European otter, a rare and threatened protected species, is very present in the Poitevin marshes. Six species of herons are also present in the marsh, the best known being the grey heron and its 760 annual couples. Since 2007, the great egret is also present in the Poitevin marsh. In the past, the marsh was also home to many eels, a species now threatened by overfishing of elvers (eel alvins). The dragonfly contributes to reduce the proliferation of mosquitoes in the Poitevin marsh.
The traditional marsh boat
For several centuries, the boat was the only means of transport for the inhabitants of the Poitevin marshes, until the 1960s. Then, the construction of paths and footbridges allowed access to the marshes by vehicle. The traditional boat is made of wood or iron and some were built to transport animals or heavy materials. From the 1920s, the boat became a means of tourist transport and nowadays, boats are mainly made of resin. It is difficult today to get a wooden boat built in the rules of art. The boats can be steered standing up or sitting down and the tapered stern of the boat allows for exceptional maneuverability with an oar (the shovel, a wooden oar) or a pole (wooden with a metal tip).
The boats, depending on their use, have different dimensions: they measure from 9 to 22 feet for market gardening, and from 8 to 12 feet for fishing. The boats intended for tourism are 13 feet long. In the past, boats measuring 20 to 22 feet were used to transport animals across the Poitevin marshes. Generally speaking, each family living in the marshes owned several types of boats, depending on their daily needs.
Tourism and the Poitevin marshes
Each year, the regional natural park of the marshes attracts nearly 1.4 million tourists. It is possible to navigate on the canals of the Poitevin marshes by boat, with or without a boatman. Some villages like Coulon or Magné have piers and offer different options to visit the marshes:
- Exceptional walks: these 2-3 hour walks, accompanied by experienced guides, are organized at dawn or dusk, with a breakfast or a tasting of regional products.
- Group tours: this option allows you to embark on a boat that can accommodate up to 12 people. The group walks last from 1 to 2 hours and are led by a guide-worker.
- The Prada Pier: created in 1977, this pier offers boat rentals, with or without a guide.
- The traditional walk: this formula allows you to visit the Poitevin marshes alone, with your family or in a small group, on board a boat accompanied by a guide.
- The legendary monster of the Poitevin marsh: this formula, lasting 2 to 3 hours, allows you to embark and discover the legendary monsters of the Poitevin marsh.
It is also possible to visit the Poitevin marshes by canoe or kayak. The map of the canals, the list of landing stages as well as the rates and rental formulas can be consulted on the website www.marais-poitevin.com