Réserve naturelle régionale du marais de Wagnonville: Protected Wetland Geography and Map

The hydrological history of the Wagnonville area goes back far beyond formal nature protection. The Escrebieux basin was once a vast alluvial wetland, a character still echoed in the name of Flers-en-Escrebieux, derived from the old word fleot, meaning water-covered terrain. In the nineteenth century, the marsh supported fish farming, with English monks establishing ponds that gave rise to the surviving local place name 'bois des Anglais'.

Throughout the twentieth century, the wetlands shrank steadily. Draining, drying, filling, and crop conversion reduced the once extensive marshes of the Escrebieux valley. In 1955 a landfill was established on the eastern edge of the Wagnonville marsh and expanded for several decades until its closure in the late 1980s. In 1960 the Escrebieux itself stopped flowing, as the creation and intensive use of drinking-water boreholes at Flers-en-Escrebieux, with annual extractions of around 18 million cubic meters by 1986, depressed the local water table and dried the river. Wagnonville thus became a rare surviving fragment of a much larger lost wetland network.

Recognition of the site's natural value emerged in 1990, when members of the GON (Groupement Ornithologique Naturel) carried out the first inventories, highlighted the ornithological interest of the marsh, and alerted the municipality of Douai. In 1994 this concern translated into formal protection with the creation of the Réserve naturelle volontaire du marais de Wagnonville. Following the 2002 'démocratie de proximité' law, which abolished all voluntary reserve classifications, the site was re-examined and, on 12 November 2007, was officially classified by the Nord-Pas-de-Calais regional council as a Réserve naturelle régionale, with the operational reference RNR23.

Ecologically, the reserve is defined by its juxtaposition of wetland, woodland, and open-ground habitats within a very small area. The aquatic core is the most distinctive element: ponds and ditches fed by the local water table support emergent vegetation, while the sphagnum bog and associated muddy edge form a specialized micro-habitat that has no real equivalent left in the surrounding region.

The woodland component includes acidiphilous willow stands that thrive on the wetter, more acidic soils, mixed shrub formations, an older park-like wooded sector, and poplar plantations planted before the site's formal protection. The open habitats on the hill support hygrophilous meadow species and graminoid communities; the meadow has been actively restored, while the fallow areas reflect a more transitional character.

Botanical surveys in 2015 identified around 220 plant species across these zones. At least three are considered patrimonial for the region: the marsh willowherb Epilobium palustre, found in wet meadows and the bog; Rorippa palustris, growing in marshy conditions; and Sphagnum russowii, whose tiny bog station is the only known occurrence of this moss in northern France, alongside four other sphagnum species also recorded in the peat bog. The marsh also supports the locally uncommon Hippuris vulgaris, sometimes called mare's tail or aquatic bread, which has become rare across much of its natural range. The site is, however, also affected by invasive plants, including Japanese knotweed, Sakhalin knotweed, smooth goldenrod, and black locust, all of which are monitored as ongoing management concerns.

The animal life of the Wagnonville marsh mirrors the diversity of its habitats. Around 140 animal species have been recorded on or around the 20-hectare site, with birds forming the most conspicuous element: 87 bird species overall, including waterfowl and wetland raptors that find refuge in the ponds, ditches, and reed-fringed bog.

The most easily observed species are visible waterbirds such as the northern shoveler and the grey heron, which use the open water and muddy edges. Four species have regional heritage value: the reed grasshopper Conocephalus dorsalis, the common pochard, the whiskered bat Myotis mystacinus, and the marsh harrier, a wetland raptor especially dependent on the reed and sedge habitats the reserve protects.

Mammal records include eight species, with bat presence confirmed through the whiskered bat record. Five amphibian and reptile species complete the vertebrate list. The invertebrate fauna is also substantial for such a small reserve, with 19 butterfly species, 7 grasshopper and cricket species, and 12 dragonfly and damselfly species documented, the latter reflecting the quality of the standing water and bog habitats that the site continues to support within an otherwise heavily urbanized landscape.

From a conservation perspective, the Wagnonville reserve matters because it preserves, in a small envelope, a habitat type that has otherwise almost disappeared from its region. The Escrebieux valley once held an extensive alluvial wetland, but successive waves of drainage, agricultural conversion, landfill expansion, and groundwater extraction reduced it to scattered fragments; the Wagnonville marsh is now one of the very last of these fragments and effectively serves as a reference site for the lost Escrebieux wetlands.

Its designation reflects a layered legal and institutional effort. National recognition came first through a voluntary reserve in 1994, and regional recognition followed in 2007 after the voluntary designation framework was reformed. IUCN protection is registered as Category IV, recognizing the site as a habitat and species management area. The Conservatoire d'espaces naturels du Nord et du Pas-de-Calais and the Commune of Douai share management responsibilities, with detailed management plans guiding habitat restoration, invasive species control, and long-term monitoring of flora, fauna, and habitats.

Equally important is the conservation work focused on the bog itself, which shelters the only known population of Sphagnum russowii in northern France and which therefore has an interest well beyond regional boundaries. Active management of hygrophilous meadows, control of invasive knotweeds and goldenrod, and ongoing faunal and floral inventories sustain the site's ability to function as a refuge for wetland species in a heavily modified peri-urban environment.

The cultural context of the reserve is woven into the older landscape rather than into recent human activity. The Escrebieux basin is associated with medieval and early modern land use, and the nineteenth-century fish ponds dug by English monks explain the persistence of the local place name 'bois des Anglais' within the protected area, a small linguistic trace of the site's pisciculture past.

The town's name Flers-en-Escrebieux preserves a more ancient layer of meaning: the toponym fleot, meaning water-covered ground, reflects how dominant wetland once was in the local identity. Today, the reservoir's cultural role is more contemporary, linked to environmental awareness and education, with guided visits allowing local residents, school groups, and naturalists to engage with a piece of living wetland history surrounded by the dense and heavily industrialized Hauts-de-France urban fabric.

Among the strongest distinguishing traits of the reserve is its peat bog, only 20 hectares in total yet hosting the only known station of Sphagnum russowii in northern France. Equally notable is the site's densely packed habitat mosaic, in which ponds, ditches, sphagnum bog, willow woodland, poplar plantation, and restored hygrophilous meadow coexist within walking distance of Douai's center. The reserve is also remarkable as a recovery story, achieved despite the loss of the Escrebieux river and the legacy of a long-running landfill on its eastern edge, both of which shaped its twentieth-century history.

The Wagnonville reserve is most rewarding in late spring and early summer, when sphagnum bog vegetation, marsh plants such as marsh willowherb, and restored hygrophilous meadows are at their most visible, and when dragonflies, damselflies, and wetland birds are most active around the ponds and ditches. Migratory and breeding waterbirds are also typically easier to observe during this window. Because access is limited to guided visits, visitors generally experience the site as a quiet, structured outing rather than a freely walked landscape; late spring through summer highlights the bog and meadow flora, while visits in late autumn or winter can offer a calmer atmosphere and good viewing conditions for overwintering waterfowl. Detailed seasonal access is best confirmed through the Conservatoire d'espaces naturels du Nord et du Pas-de-Calais, which organizes public events on the site.