Réserve naturelle régionale des marais et landes du Rothmoos Protected Area and Map Geography

The history of the Rothmoos reserve is closely tied to the industrial past of the Alsace potash basin. Original ground subsidence caused by the mines destabilized the subsoil, transforming what had been forestland into a fluctuating marsh. The unstable water levels initially favored proliferation of mosquitoes that disturbed nearby residents, prompting action by the potash company and the Conservatoire des Sites Alsaciens. In 1984, a joint effort stabilized the water levels to prevent mosquito breeding, but this technical intervention had a major ecological side effect: stable open water bodies began to support rich populations of dragonflies and other aquatic life.

On August 4, 1988, the prefecture formally created a voluntary nature reserve (réserve naturelle volontaire) covering a 21-hectare triangle bordered by railway lines within the Nonnenbruch forest massif, on the commune of Wittelsheim. Over the following decades, the site manager expanded the protected zone through land acquisitions, reaching northward to the Cité Amélie neighborhood and eastward to the Rothmoos spoil heap.

In 2012, the voluntary reserve was reclassified as a regional nature reserve by deliberation on March 16, 2012, consolidating the legal protection that the earlier designation had provided and giving the site its current institutional form. The first formal management plan covered the period from 1999 to 2004, providing the framework for ongoing conservation work by the Conservatoire des Sites Alsaciens.

The Rothmoos landscape is shaped by an unusual combination of forest, wetland, and industrial legacy. The reserve lies within the Nonnenbruch, one of the larger forest massifs of the Alsatian plain, and includes sections of oak woodland that transition abruptly into open wetland depressions. These depressions were originally created or accentuated by underground potash mining subsidence, and the resulting uneven topography defines much of the site's character.

Open water pools, reedbeds, and tall-herb marshes occupy the lowest areas, while slightly higher ground supports drier vegetation including heathland and oak-dominated woodland. A particularly visible feature within the perimeter is an old mining spoil heap, the terril de Rothmoos, which adds mineral color and elevation contrast to an otherwise low-lying landscape.

The brackish quality of some soils and waters, inherited from the region's mining history, creates rare inland salt-influenced habitats that would not otherwise occur in this part of France. Together, these features give Rothmoos a discontinuous, mosaic-like scenery where forest patches, marshy clearings, and industrial relics coexist within a small geographic footprint.

Rothmoos is defined above all by its mosaic of wetland habitats. The principal ecological interest of the reserve lies in the diversity of wet environments it contains, including extensive reedbeds and tall-herb fens, alongside drier areas of oak woodland and heath. Together these habitats form a complex patchwork across the protected perimeter.

The salinity of certain soils and waters, a legacy of the potash industry, allows for halophilic species typically associated with coastal or estuarine environments to grow inland. This unusual ecological profile supports a flora of around 329 species, among them regionally notable plants such as Schultz's violet, marsh sow-thistle, and marsh spurge. The combination of reedbed, marsh, heath, oak woodland, and saline clearings makes the reserve a compact node of habitat diversity within the Nonnenbruch forest.

Rothmoos supports rich wildlife relative to its size. Surveys have documented around 173 animal species across the site, including 17 mammals, 7 amphibians, 6 reptiles, and 3 fish species. The amphibian fauna includes the tree frog, while reptile and mammal communities reflect the wider mosaic of forest and wetland habitats.

The avifauna is particularly significant, with about 140 bird species recorded. The open pools and reedbeds act as attractive stopover and wintering sites for many migratory and overwintering waterbirds, complementing the more typical forest birds of the surrounding Nonnenbruch woodland.

Among invertebrates, dragonflies are a key feature of the reserve. The stabilization of water levels in the 1980s, originally a mosquito-control measure, allowed dragonfly populations to flourish, and other notable insects such as the purple-shot copper butterfly, the praying mantis, and the yellow-winged darter dragonfly are also recorded. Together these groups give the reserve a strong identity tied to wetland-dependent fauna.

The primary conservation purpose of the Rothmoos reserve is the protection of an unusual habitat mosaic in a region under significant urban pressure. The surrounding Nonnenbruch forest, one of the larger forested massifs of the Alsatian plain, has long been threatened by expanding urbanization, and the reserve is explicitly intended to act as a refugium for biodiversity within this landscape.

Protection of the saline and brackish wetlands, which depend on a fine-tuned hydrological regime inherited from former mining activity, is a particular concern. Maintaining stable water levels is essential both for the rare halophilic flora and for the dragonfly and bird communities that depend on open water and reedbeds.

By acquiring additional land over the years, the managing body, the Conservatoire des Sites Alsaciens, has steadily increased the protected surface and created a continuous buffer against infrastructural pressure from nearby towns and mining-related sites.

The reserve's standout feature is the unusual inland brackish and saline wetland complex, a direct legacy of the region's potash mining history, which now supports a remarkable concentration of biodiversity within a small area.

Equally notable are the dense dragonfly populations that emerged after water levels were stabilized in the 1980s, and a diverse avifauna of around 140 species that uses the pools and reedbeds for migration and wintering. The presence of an old mining spoil heap within the protected perimeter gives the site a strong industrial-to-natural heritage that is increasingly rare in mainland European conservation.

Wetland sites in northeastern France are generally most rewarding in late spring and early summer, when reedbeds are in full growth, dragonflies are at their most active around the pools, and migrant bird activity is high. Early morning visits during this period offer the best chances to observe both breeding wetland birds and insects.

Autumn can also be rewarding for birdwatchers, as the open water and reedbeds attract migratory and wintering species. Because the reserve's most distinctive ecological assets, including its saline habitats, dragonfly populations, and rare plants, are tied to specific seasonal conditions, visiting outside the warmest months may limit wildlife encounters but still allow appreciation of the broader landscape mosaic.