Hofermühle Süd Nature Reserve: A Detailed Geographic Overview of the Mettmann District Landscape

Hofermühle Süd is best known for an abandoned limestone quarry that has been allowed to return to a wild state, providing a refuge for amphibians such as the great crested newt and the midwife toad, and for a nutrient-poor calcareous flora that includes several rare orchids and the unusual adder's-tongue fern.

The reserve's recent history begins with the closure of the quarry around 1945. What had been an active limestone extraction site was simply abandoned, allowing its rock faces, floor and former workings to revert gradually to a wild state with minimal human intervention.

Formal protection came in 1984, when the area south of central Heiligenhaus and adjacent to the historic Hofermühle was designated as a Naturschutzgebiet under the code ME-009. It was incorporated into the wider Mettmann landscape plan, with a revised framework issued in 2012. Administration lies with the Untere Landschaftsbehörde, the lower landscape authority of the Mettmann district. The reserve also sits alongside the larger Naturschutzgebiet Angertal, whose designation added roughly 387 hectares of additional protected land to the surrounding valley.

The landscape of Hofermühle Süd is shaped almost entirely by its industrial past and the geology that made extraction worthwhile. Steep, near-vertical quarry walls of Middle Devonian limestone cut into a small valley, while the quarry floor has settled into a mosaic of bare rock, lean soil and a small standing-water body.

At the surface the reserve sits between roughly 104 and 145 metres above sea level, on gently sloping terrain at the southern edge of Heiligenhaus. The western third of the area is crossed by the Anger, which on this 400 metre stretch winds tightly through its small floodplain, undercutting banks and building them up again in classic meander form. Together the bare rock faces, the sheltered pond, the creek's tight loops and the floodplain margins create a dense micro-topography that, despite the small footprint, contains a noticeable diversity of exposures and moisture conditions.

Ecologically, Hofermühle Süd is defined by the contrast between the very dry, calcareous quarry habitats and the wetter Anger floodplain. On the rock faces and thin soils, the limestone produces nutrient-poor, base-rich conditions that favour a specialised flora of lime-loving plants, including several orchid species and an assemblage of rare wildflowers. Shrub encroachment has not yet eliminated these open communities, so light-loving, calcareous grassland species continue to thrive alongside the bushes.

The wet side of the reserve is equally important. The Anger's meanders and soft banks support characteristic riparian habitats, while the quarry pond and the old angling pond, now fully dedicated to nature, provide still water for amphibians and dragonflies. Together these habitats form a near-natural complex that acts as a stepping-stone within the regional biotope network, linking the quarried slope directly to the broader Anger valley system.

The reserve hosts a notably broad fauna for its size, precisely because the combination of dry rocky habitat, ponds and a meandering stream creates very different ecological niches within a few hundred metres of each other. The pond at the quarry's foot and the old angling pond together make the area an important amphibian breeding site, supporting species such as the great crested newt and the midwife toad.

Reptiles are also represented, with the grass snake using the warmer rocky slopes and pond edges. Birds benefit from the largely undisturbed conditions; the little woodpecker, the woodcock and the little owl are among the species documented in the area, several of them classified as endangered or vulnerable on the North Rhine-Westphalian Red List. The quarries and waters are additionally noted for their insect life, including dragonflies linked to the ponds.

Hofermühle Süd is designated as an IUCN Category IV Habitat/Species Management Area, a status that reflects its role in actively maintaining specific habitats and species rather than preserving a broad, untouched landscape. Its formal protection objectives are deliberately targeted: safeguarding and improving the abandoned limestone quarry as a habitat for rare animals and plants, preserving the orchid and adder's-tongue populations, and maintaining and developing the near-natural section of the Anger creek with its associated floodplain forest.

In practical terms, this means that public access is restricted by fencing and a prohibition on entering the site. The lack of disturbance is itself a management tool, allowing sensitive amphibian populations, ground-nesting birds and rare plants to persist without trampling or collecting pressure. The reserve also has a clear landscape-level function: as part of the Angertal system and a regional biotope network, it provides a stepping-stone habitat that supports populations in the larger surrounding protected areas, reinforcing the conservation value of the whole valley.

The name Hofermühle itself points to a long-standing human connection with the valley: it refers to a historic mill on or near the Anger, and the reserve sits in the Angertal just to the south of Heiligenhaus's old centre. The quarry, on the other hand, is a reminder of a more recent industrial past. Limestone was extracted here until around the end of the Second World War, and the reserve's current ecological identity is, in effect, a byproduct of that earlier economic activity. The present-day conservation story is therefore one of taking an exploited industrial site and allowing it to revert to a wild state that is now valued primarily for its biodiversity.

A protected, abandoned Devonian limestone quarry with steep walls and a base pond, acting as a quiet refuge for amphibians, reptiles and breeding birds.

A 400 metre stretch of the Anger creek running in a near-natural, tightly meandering course through the western edge of the reserve, with associated floodplain habitat.

A sharply specialised calcareous flora on the thin, base-rich quarry soils, including several orchid species and rare plants such as the adder's-tongue fern.

The reserve itself is closed to visitors, so any experience of Hofermühle Süd is essentially appreciation of the protected area from the outside, supported by the surrounding Angertal landscape. Vegetation in and around the quarry will be most expressive in late spring and early summer, when orchids and other calcareous wildflowers are in bloom, and when amphibian activity around the ponds is at its peak. Cooler months are better for observing wintering and passage birds in the wider valley, while the meanders of the Anger are visually clearest when foliage is lower. Because the quarry is fenced and access is prohibited, the experience is best framed as a scenic landscape walk through the surrounding Angertal rather than a direct visit to the protected core.