La Claireau

La Claireau is a small managed biological reserve (réserve biologique dirigée) located within the Hardelot State Forest, in the municipality of Condette, in the Pas-de-Calais department of the Hauts-de-France region in northern France. The site sits less than 3 kilometers from the English Channel coast, at an altitude of 24 to 28 meters. The reserve covers 5 hectares and borders the Marais de Condette nature reserve.

When was the reserve established and why?

La Claireau was created on February 16, 1982, and is classified under IUCN protected area category IV. The site also forms part of the Natura 2000 network, within the area known as "Estuaire de la Canche, dunes picardes plaquées sur l'ancienne falaise, forêt d'Hardelot et falaise d'Equihen." The reserve was established specifically to protect a population of royal fern, a species considered rare in France, and its habitat.

What geology shapes this landscape?

The reserve sits on sedimentary formations dating from the Upper Jurassic and Cretaceous periods. Its defining physical feature is a seepage zone that forms where permeable sandy layers meet underlying impermeable clay and marl. This constant groundwater seepage keeps the soil permanently waterlogged in parts of the reserve, which in turn determines the type of vegetation that grows there.

What forest habitats are found here?

Two main forest habitats characterize La Claireau. The first is wet alder-birch woodland, found in the permanently waterlogged sections, with an understorey rich in sedges and royal fern. The second is oak-ash woodland, occupying the drier parts of the reserve. Old, multi-stemmed pollarded hornbeams — a legacy of traditional coppicing — provide important habitat for wood-boring insects, cavity-nesting birds, and bats.

What plants and animals live in the reserve?

Alongside royal fern, the species the reserve was created to protect, the forest floor supports other ferns including lady fern and bracken, as well as alternate-leaved golden saxifrage. Bird species recorded here include honey buzzard, black woodpecker, wood pigeon, lesser spotted woodpecker, and bullfinch. The old hollow trees also support saproxylic insects and roosting bats.

How is the reserve managed?

La Claireau is managed under a "free evolution" (libre évolution) approach, meaning human intervention is kept to a minimum so natural processes can continue undisturbed. Management goals focus on preserving the wet forest habitats and maintaining the hydrological conditions that royal fern and its associated plant community depend on. The reserve is overseen by the Office National des Forêts (ONF), the French public body responsible for managing state-owned forests.

Frequently asked questions

Where exactly is La Claireau located? Within the Hardelot State Forest, in the municipality of Condette (Pas-de-Calais), less than 3 km from the coast.

How large is the reserve? It covers 5 hectares, at an altitude of 24–28 meters.

Why was the reserve created? To protect a population of royal fern and the wet alder-birch forest habitat it depends on.

Is the site open to visitors? The reserve is managed with minimal human intervention under a free-evolution approach, typical of protected areas managed by the ONF.