Grand-Lieu Lake, located south of Nantes in Loire-Atlantique, is one of France’s richest wetland ecosystems. It hosts exceptional biodiversity and a unique natural heritage shaped by shallow waters, dense aquatic vegetation, and carefully managed habitats.
Exceptional biodiversity
This “haven for wildlife” supports an extraordinary range of species:
- 550 plant species recorded on and around the lake.
- 270 bird species, making it the second most important site in France after the Camargue.
- In spring, around 2,000 pairs of grey herons gather; Eurasian spoonbills also nest on site.
- In winter, up to 25,000 ducks rest on the lake.
- 50 mammal species, including the otter.
- 30 fish species, including the European eel.
- 12 amphibian species, including the common frog and the common midwife toad.
A unique natural heritage
In winter, Grand-Lieu Lake covers around 6,000 hectares, making it the largest natural lowland lake in France. It is designated as a Ramsar site and a Natura 2000 site. Nearly 2,700 ha are classified as a National Nature Reserve, and about 660 ha as a Regional Nature Reserve (RNR).
Four main habitats can be distinguished:
- Open water at the centre, covering more than 1,200 ha.
- Along the edges, around 1,300 ha of aquatic plant beds dominated by white and yellow water lilies, water caltrop, and fringed water lily—forming the largest aquatic plant bed in France.
- A large reed bed covering about 1,500 ha.
- Flood meadows submerged for six to eight months each year, where Vache nantaise (Nantes cows), a threatened breed, graze.
The lake’s shallow depth (around 1 metre in summer and 3 metres in winter) explains the density of vegetation. Ecologically, the lake is often compared to certain African lake systems due to its productivity and habitat structure.
Management of the Regional Nature Reserve
The Grand-Lieu Lake Regional Nature Reserve (RNR) is managed by the Loire-Atlantique Hunters’ Federation. With the classification of 656 hectares (owned by the Foundation for the Protection of Wildlife Habitats) as an RNR, the broader Grand-Lieu Lake area is now subject to specific conservation measures and close surveillance.
Management is carried out in scientific partnership with the French Biodiversity Office (OFB), and includes several essential roles:
- Monitoring and counting species, in close collaboration with the National Nature Reserve.
- Managing meadows used for summer grazing and implementing a “mow-and-graze” system recognised as highly effective for supporting birdlife.
- Health monitoring, including collecting dead birds to reduce the risk of botulism.
Concrete actions for the future of the lake
The reserve’s management plan is based on the active participation of local stakeholders and focuses on practical, measurable actions:
- Scientific work: botanical surveys, monitoring of overwintering birds, and tracking breeding success—particularly among waterfowl (Anatidae).
- Invasive species control: monitoring and action against invasive animals such as the nutria and Louisiana crayfish, and invasive plants such as creeping water primrose. Trapping and removal campaigns are conducted and monitored to assess impacts on populations and biodiversity outcomes.
- Sustaining grazing: since 1997, a herd of Nantes cows (a threatened local breed) has helped maintain meadow habitats exposed for roughly six months per year.
- Opening to the public: to combine discovery with respect for the site’s tranquillity, a mobile bird observatory has been created, supported by educational tools and guided activities.
This approach is described as conservative and heritage-oriented, enhancing fauna through inventories and naturalist monitoring. These tools support targeted conservation measures for species showing demographic decline or potential future risk. The same approach protects rare flora by managing invasive alien species that can damage reeds and shorelines and degrade plant communities.
Sharing knowledge and engaging citizens
Beyond habitat and species management, the Loire-Atlantique Hunters’ Federation actively shares expertise with the public through educational nature outings and outreach activities, strengthening the connection between French citizens and wetland conservation.
Policy relevance
The conservative and heritage-based management of Grand-Lieu Lake aligns with key objectives of the EU Biodiversity Strategy, notably reversing biodiversity loss, restoring ecosystems, and promoting the multifunctionality of rural landscapes. The project shows how local initiatives can translate broader EU ambitions into effective on-the-ground conservation.
Maintaining grazing systems and generating robust scientific knowledge on sensitive species are major challenges addressed by the project, reflecting EU goals to reconnect ecosystems and support vulnerable biodiversity. The collaborative work with farmers to sustain grazing practices also illustrates how local initiatives can complement EU policies such as the Common Agricultural Policy (CAP) by integrating biodiversity considerations into day-to-day land management.
Finally, the Grand-Lieu model offers a practical example for other hunting associations and local land managers across Europe, demonstrating how structured monitoring, habitat maintenance, invasive species management, and public engagement can deliver tangible conservation benefits.
