Sonsfeldsches Bruch, Hagener Meer und Düne: A Protected Landscape in North Rhine-Westphalia

The reserve is best known for the Hagener Meer, a former Rhine arm that today functions as a still-water oxbow with extensive floating leaf vegetation and a diverse fringe of reeds and marsh plants. It is also known for its fragment of inland dune, a sandy elevation in the northern part of the protected area that has retained dry, light-demanding plant communities unusual for the generally wet Lower Rhine plain. Together, these features make the site a textbook example of how a very small protected area can combine aquatic, wetland, and sandy dry habitats within a single continuous landscape. The dune fragment in particular gives the reserve an unexpected seminatural open-sand character that contrasts sharply with the surrounding marsh and woodland.

The landscape around the nature reserve reflects the long history of the Rhine reshaping its floodplain. The Hagener Meer originated as an active arm of the Rhine that was eventually cut off as the main river migrated across its broad lower valley, leaving a long, narrow oxbow that gradually became a backwater environment. The dune in the northern part of the area is thought to have formed when sand deposited during floods was later shaped by wind into a small dune within the floodplain forest belt.

Modern protection of the site began in the early 1990s, when the area was formally designated as a nature reserve to safeguard the old Rhine channel, its adjacent wetland margins, and the inland dune remnant. The landscape plan for Rees was revised in 2010, which reaffirmed and updated the protected status of the area. The reserve has since been managed under the supervision of the Naturschutzzentrum Kreis Kleve, with a strong emphasis on maintaining open dune habitat, conserving aquatic plant communities, and protecting breeding and resting bird populations.

The protected area comprises three clearly distinct landscape elements within a small footprint. The dominant feature is the Hagener Meer, a long, narrow oxbow lake that curves through the reserve and is lined by reeds, marsh, and wet woodland. Its calm water surface and gradual banks contrast with the surrounding lowland agricultural plain east of Rees.

Around the oxbow, the Sonsfeldsches Bruch forms a zone of soft, wet ground historically influenced by the flood regime of the Rhine. Here, marsh forest, damp meadows, and reed beds create a transitional belt between open water and drier land. Near the edges of the reserve, land use becomes more agricultural, but the wooded and marshy core maintains a continuous green corridor along the old river arm.

In the northern part of the area rises the Düne, a low sand dune whose flanks support open sandy vegetation. Its relief subtly interrupts the otherwise level floodplain and creates a small but ecologically significant dry habitat surrounded by wet woodland and water. The contrast between the dune's dry, sun-warmed sand and the moist marsh and still water around it gives the reserve much of its landscape character.

Ecologically, the reserve serves as a refuge for habitats that have become scarce in the broader Lower Rhine landscape. The Hagener Meer supports well-developed floating leaf vegetation and a varied reed structure, including the white water lily, yellow water lily, and frogbit, all of which are considered threatened in North Rhine-Westphalia. Senecio sarracenicus, the river ragwort, also finds a foothold here, an indicator of the site's value for aquatic and riparian flora.

Marsh forest, damp grassland, and wet shrub communities fringe the oxbow, providing habitat continuity for amphibians, invertebrates, and birds that depend on a gradient between open water and shaded riparian woodland. Many of the plant species recorded for the protected area are associated with these transitional wetland environments, including yellow iris, purple loosestrife, marsh marigold, hemp agrimony, and various sedges and bulrushes.

The dune fragment at the northern edge of the reserve introduces a fundamentally different habitat into the same protected area. Its open, acidic sand supports light-demanding species such as early hair grass, sand sedge, spring spurrey, and shepherd's cress, plants that are unusually drought-tolerant for the region and have become rare in North Rhine-Westphalia. Maintaining these dune species requires active management, because natural succession toward woodland would otherwise quickly shade them out.

The Hagener Meer and its surrounding marshland provide a particularly favorable environment for waterbirds, reedbed species, and migratory birds. The reserve lists a number of specially protected species, including the marsh harrier, white stork, common kingfisher, bittern, bluethroat, white-tailed eagle common snipe, ruff, and golden plover, as well as breeding or passage migrants such as little ringed plover, wood sandpiper, common redshank, northern lapwing, and black-tailed godwit. Sedge warbler, garganey, common teal, Eurasian wigeon, and garganey-like species also pass through or nest in the area, alongside swans such as whooper and tundra swans.

The slow-flowing oxbow water is also valuable for aquatic fauna. Several fish species of conservation concern are associated with the water bodies and connecting drainage systems, including allis shad, asp, spined loach, bullhead, white-finned gudgeon, river lamprey, sea lamprey, bitterling, and salmon in their freshwater phase. These species depend on clean, well-oxygenated water and continuity with the broader river system, and their presence reflects the importance of the reserve within the Lower Rhine fish fauna.

The dune area supports a distinct invertebrate community adapted to warm, open sand. Though the source documentation emphasizes plants more than animals for the dune habitat, the persistence of specialized sand fauna is one of the reasons regular clearing of encroaching shrubs is carried out. Together, waterbirds, wetland-dependent birds, fish, and sand-loving invertebrates give the reserve a varied and ecologically meaningful fauna.

As a formally designated nature reserve under North Rhine-Westphalian law, Sonsfeldsches Bruch, Hagener Meer und Düne is managed primarily for habitat and species conservation. It is classified as IUCN Category IV, indicating that its purpose is the active management of particular habitats and species rather than the protection of a large untouched landscape. The reserve aims to maintain and, where necessary, restore favorable conservation status for natural habitats of community interest.

A core conservation focus is the oxbow lake and its associated plant communities. The protection order seeks to ensure the preservation and recovery of well-developed floating leaf vegetation, diverse reedbeds, and the rare aquatic plants that characterize the Hagener Meer. Because these communities depend on stable hydrology and minimal disturbance, the surrounding wetland margins are included in the protected area to buffer the lake from agricultural and other local pressures.

Equally important is the conservation of the inland dune remnant. Dunes in the Lower Rhine depend entirely on open conditions, and without intervention they quickly become overgrown by shrubs and trees. The protection order therefore requires ongoing habitat management, including the removal of encroaching woody vegetation, to keep the dune flora and its associated sand fauna viable. Together, these active measures ensure that the reserve maintains its unusual combination of open water, wet marsh, and dry sand within a small but ecologically rich footprint.

The Sonsfeldsches Bruch takes its name from local historical features: the 'Bruch' refers to wetland or boggy terrain, the Hagener Meer is named after the nearby locality, and the 'Düne' reflects the sand dune still preserved within the reserve. The area lies between two former aristocratic estates, Schloss Sonsfeld to the north and Schloss Bellinghoven to the south, a reminder that the modern nature reserve sits within a centuries-old cultural landscape shaped by noble landholdings, agriculture, and the management of the Lower Rhine floodplain.

The names of nearby protected areas and waterways, such as the Haffensche Landwehr-Sonsfeldsche Weiden and the long sequence of Altrhein and Meer sites around Rees, speak to a long regional tradition of recognizing the ecological value of former Rhine channels. The Lower Rhine identity of the region, with its network of old river arms, wet pastures, and estate-based landholdings, forms an important cultural backdrop to the conservation efforts of the present-day reserve.

Three contrasting habitats in one compact reserve: a Rhine oxbow with floating leaf vegetation, a marsh forest belt along the Sonsfeldsches Bruch, and a small inland sand dune with open sand flora. Particularly notable for rare and threatened wetland and aquatic plants such as the white water lily, yellow water lily, frogbit, and river ragwort. The dune fragment makes the reserve unusual among Lower Rhine nature areas, since light-demanding sand vegetation is rare in the region.

The nature reserve can be appreciated year-round, but the seasons give it quite different character. Spring and early summer are the best times for the wetland flora of the Hagener Meer and the surrounding marsh forest, when floating leaf vegetation, reeds, and woodland wildflowers are most active and migratory birds are present.

Late summer and autumn highlight the contrast between the lush wet habitats and the drier dune, when warm sand conditions favor the specialized dune plants and their associated fauna. Winter can also be rewarding for birdwatchers, as the open water and undisturbed marsh attract waterfowl, swans, and other winter visitors that use the sheltered corridor of the old Rhine arm.