Kalkarer Moor / Tongrube Toni Nature Reserve and Wetland Landscape in North Rhine-Westphalia

The Kalkarer Moor has a deep land-use history, visible even in early mapping. The Tranchot map, created between 1801 and 1828, already records the area as being used predominantly as meadow and pasture. Botanical literature from the mid-nineteenth century mentions the site because of its unusual flora for the region, establishing its scientific reputation long before formal protection existed.

By the early twentieth century, draining of the surrounding land had begun to take a toll on the mire. Lowering of the water table through increased groundwater extraction caused the spring-fed parts of the moor to dry out substantially by 1918, accompanied by a documented decline in species. In the early 1950s the Mersbach stream was straightened and deepened to improve drainage of the surrounding farmland, and further drying of the source fen was observed during this period. Until the early twentieth century peat was also reportedly cut here for fuel.

Recognition of the area's natural value gradually translated into legal protection. In 1935 the Kalkarer Moor was placed under landscape protection (Landschaftsschutz), and in 1965 parts of it were formally designated as a nature reserve (Naturschutzgebiet), making it one of the older protected sites in the Kreis Euskirchen.

A more recent chapter in the reserve's history is tied to clay extraction. Aerial photographs from 1945 already show the Toni pit and adjacent agricultural parcels. Clay mining continued there until 1974, when the operation was closed. Because the pit was simply abandoned rather than filled, groundwater seeped in and created a new aquatic habitat, effectively expanding the wetland complex.

The single biggest modern turning point came with groundwater management reform. From 2010, after a two-year pause in extraction, the local water association conducted a trial phase that concluded in 2015 with a new extraction plan. Instead of allowing withdrawals of up to 2.5 million cubic metres per year, future use was capped at up to 750,000 cubic metres per year, significantly reducing pressure on the reserve's hydrology and giving the mire a better chance of recovery.

The landscape of Kalkarer Moor / Tongrube Toni is a quiet, low-lying wetland mosaic set within the gently rolling terrain of the western Eifel foothills. The reserve lies in a shallow valley position at the foot of the surrounding agricultural and wooded uplands of Bad Münstereifel, with the Mersbach cutting across its northern edge from west to east.

The defining surface feature is the calcareous flat mire itself (Kalkflachmoor). Its central and southeastern sections are largely covered by tall reed stands that have expanded across the open fen surfaces, creating dense, seasonally swaying stands of common reed. Around this core, the terrain transitions into different habitat types. To the northeast, an extensively managed fresh meadow lies open and flat, framed by a path-side hedgerow that softens the boundary between the reserve and surrounding farmland. In the south, wetter ground supports dense stands of black alder, while along the edges the soil dries out enough for shrub thickets and successional woodland dominated by trembling aspen, sycamore and silver birch to take hold.

The Tongrube Toni introduces a different element of relief. Where the former clay pit lies, the ground drops into a basin, now holding standing groundwater rather than active industrial infrastructure. This sunken pit adds open water and gently sloping shorelines to the mosaic, producing habitat that is structurally distinct from the surrounding marsh and reed.

Overall, the landscape reads as a compact patchwork of small, contrasting features rather than a single broad panorama. The visual strength of the area lies in the way reedbeds, wet woodland, water-filled quarry and managed grassland sit close together, defined by subtle changes in water level, soil chemistry and vegetation height rather than dramatic topography.

Ecologically, the reserve is unusual for the region because the groundwater feeding it is rich in dissolved carbonates. This produces a calcareous, spring-fed fen, a habitat type that has become rare across much of the western Eifel. The combination of stable hydrochemistry and a long history of low-intensity land use has allowed a relatively rich specialist flora and fauna to persist.

Inventories have documented 419 vascular plant species, around 70 moss species and a Charophyte algae (Armleuchteralge), some of which do not occur naturally elsewhere in the broader region. The vegetation mosaic includes reed-dominated fen surfaces, moist and nutrient-poor grassland, black alder swamp woodland, and drier successional woodland of aspen, sycamore and silver birch. The result is a layered vegetation pattern where open fen, marsh, wet woodland and dry woodland meet within a short distance.

The wet conditions also shape nutrient dynamics. The management plan explicitly aims to prevent further eutrophication and the spread of dense reed stands, both of which can displace the more diverse fen communities. Maintaining low nutrient input from surrounding farmland and avoiding further drainage are central to keeping the habitat spectrum intact.

The slightly acidic and base-rich mosaic supports a range of invertebrates, mosses and algae that depend on stable, clean water conditions, which is a key reason why the area has been flagged as regionally important for conservation.

The reserve is particularly notable for its birdlife, which depends on the combination of reedbeds, wet woodland, open water and damp grassland. Species recorded within the area include common snipe (Bekassine), grasshopper warbler (Feldschwirl), common nightingale (Nachtigall), golden oriole (Pirol), reed bunting (Rohrammer), white ermine moth (Schwarzspanner), short-eared owl (Sumpfohreule), marsh warbler (Sumpfrohrsänger), Eurasian reed warbler (Teichrohrsänger), and water rail (Wasserralle).

Several of these species are tied closely to specific structural elements within the reserve. Marsh warbler, reed warbler, reed bunting and water rail depend on the extensive reedbeds along the fen, while short-eared owl and common snipe favour the more open marsh and rough grassland. Common nightingale and golden oriole are typically associated with the wet woodland edges and shrubby transitions, illustrating how the different habitat patches within the small reserve support distinct bird communities.

Beyond birds, the mosaic of fen, water-filled quarry and woodland edges provides habitat for a range of invertebrates and small wetland-dependent mammals, although detailed information on these groups is limited. From a conservation standpoint, the continued presence of marsh-nesting birds and mire-associated species is one of the strongest indicators that the reserve still functions as a viable wetland refuge in this part of North Rhine-Westphalia.

Kalkarer Moor / Tongrube Toni is designated as a nature reserve (Naturschutzgebiet) under North Rhine-Westphalian conservation law, and its core objective is the long-term preservation of the calcareous flat mire and its associated flora and fauna. Protection aims to prevent further eutrophication, to halt excessive expansion of reed stands at the expense of more diverse fen communities, and to maintain the high species diversity that has drawn botanists to the site for more than a century.

Active management is closely tied to hydrology. Because the area's botanical value depends on calcareous spring water reaching the surface, the reserve plan calls for refraining from further watercourse engineering on the Mersbach, from fertilizing the surrounding grassland, and from any land-use change that would further lower the water table. Where the original spring-fed fen had partly dried out in the twentieth century, the plan envisages targeted restoration of the source mire (Quellmoor) so that characteristic mire species can recolonize.

A major conservation milestone came in 2015, when a new groundwater extraction plan capped withdrawals at up to 750,000 cubic metres per year, roughly one third of the previously permitted maximum of up to 2.5 million cubic metres. This change is expected to gradually improve the water supply to the reserve and to support recovery of degraded parts of the fen. A 2019 management and development plan published by Kreis Euskirchen lays out the detailed steps for monitoring, restoration and ongoing protection of the site.

The cultural context of Kalkarer Moor / Tongrube Toni is closely tied to long-standing rural land use in the western Eifel. Historical maps from the early nineteenth century show the area already shaped by meadow and pasture management, while the mid-1800s botanical literature indicates that the site attracted scientific attention from outside the region because of its unusual plant communities. Peat cutting is also reported from earlier in the twentieth century, reflecting a tradition of small-scale, local use of mire resources.

Industrial activity is represented by the Tongrube Toni itself. Clay mining left a visible mark on the landscape during the mid-twentieth century, and although extraction ended in 1974, the abandoned pit has been incorporated into the protected area rather than erased from it. The result is a reserve where centuries of agricultural use, brief industrial use and modern conservation management overlap in the same small catchment.

The reserve's biggest highlight is the juxtaposition of an ancient calcareous spring-fed lowland moor with a modern open-water wetland created from a former clay pit. Together they provide a layered habitat mosaic of reedbeds, wet meadows, black alder woods and successional shrub in an unusually compact area.

It is also one of the historically and scientifically significant wetland sites in the Kreis Euskirchen, with botanical references dating back to the mid-nineteenth century and formal protection stretching back to 1935. The 2015 reform of groundwater extraction, which sharply reduced permitted withdrawals, gives the reserve an unusually clear story of conservation-driven hydrological recovery.

Late spring and early summer are generally the most rewarding periods for visiting a calcareous wetland reserve of this type, when the reedbeds are at their tallest and wetland birds such as reed warblers, marsh warblers and reed buntings are most actively calling and breeding. Early mornings tend to be the most productive time for observing these species.

Outside the breeding season, the reserve still has visual interest: autumn brings colour changes in the wet woodland of black alder, aspen and birch, and winter can offer a stark, open view of the fen structure once the reed has died back. Visitors should expect damp, sometimes boggy ground and water-filled sections around the former clay pit regardless of season, so solid footwear is appropriate throughout the year.