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Biodiversity/Les milieux humides et aquatiques
Les milieux humides et aquatiques

Les milieux humides et aquatiques

Commissariat général au développement durableDec 18, 2025

Les milieux humides et aquatiques continentaux sont variés, naturels ou artificiels. La présence d’eau peut être permanente ou temporaire : cours d’eau, étangs, marais, canaux, retenues d’eau, etc. L’eau peut y être stagnante ou courante, douce ou salée.

Inland wetlands and aquatic environments are varied, whether natural or artificial. Water presence may be permanent or temporary: rivers, ponds, marshes, canals, reservoirs, etc. Water may be stagnant or flowing, fresh or saline.
2 chapters
  • What is a "wetland"?
    Definition and fauna
    Wetlands are identifiable by the presence of water on the surface or in the soil. Fauna and flora adapted to these environmental conditions develop there. These species contribute to the formation of highly diverse ecosystems.
    Area and forms
    Today, no study provides a precise assessment of the area of wetlands across mainland France and overseas territories. The most recent surveys estimate that wetlands cover approximately 23% of mainland territory, or nearly 13 million hectares, roughly 8 times the size of Brittany. Wetlands take different forms: marshes, peatlands, mudflats, and floodplain forests.
  • The benefits of wetlands
    Water regulation and quality
    • Wetlands play a role in storing and improving surface water quality. They save the equivalent of €2,000 per hectare annually in drinking water treatment costs. Vegetation in these ecosystems participates in the water cycle through roots that cause water to evaporate or infiltrate. According to the latest national assessment of emblematic wetland sites from 2010-2020, 86% of sites evaluated in 2020 provided water regulation and supply services. Their degradation could compromise the services these environments offer to society. • Wetlands experience seasonal flooding necessary for their proper functioning. Wetlands also help reduce flood intensity. Wetlands buffer the effects of climate change. They replenish groundwater and watercourses, delaying drought effects and preserving water. Every year in France, services provided by wetlands and aquatic environments in nitrogen retention save taxpayers 2 billion euros.
    Peatlands and carbon
    For example, peatlands are wet areas containing peat, a spongy material formed from decomposed vegetation and protected from air. Peatlands are carbon sinks. They cover only 0.2% of mainland France but store 0.5 tons of CO₂ per hectare annually, equivalent to the emissions of a television. Disruption or degradation of peatlands would release into France a stock estimated at 3,214 tons of CO₂ per hectare destroyed, equivalent to emissions from 6,400 Paris-New York round trips by plane. These environments must therefore be protected, at the risk of releasing very large quantities of greenhouse gases into the atmosphere.
    Biodiversity and fishing
    • Inland wetlands and aquatic environments are places of rest, reproduction, and feeding for a wide diversity of animals. It is estimated that more than one-third of metropolitan species benefit from these habitats. Among them, 80 fish species found in French rivers and over 90 nesting bird species depend on them. • Fishing for wild species in inland wetlands and aquatic environments (mainly fish) represents an annual commercial value of approximately 240 million euros. Professional freshwater fishing is an activity practiced today by nearly 400 professionals in France and generated revenue of approximately 27.7 million euros in 2020.
    Recreation and green tourism
    These environments also offer multiple recreational activities, such as swimming, fishing, and water sports. In 2022, over 1.4 million fishing licenses were issued in France. There is also green tourism that is currently thriving. The Loire à Vélo initiative, for example, offers a non-polluting cycling experience to discover natural heritage across 900 km of cycling trails. This destination attracted 1.8 million cyclists in 2022 and generated 54.5 million euros in direct returns to the regions traversed.

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