Großer Heuberg und Donautal: An Integrated Protected Area of the Swabian Alb and Danube Valley

The protected area in its current form is relatively young in administrative terms. It was formally established as the FFH-Gebiet Großer Heuberg und Donautal on 1 January 2015 through a deliberate merger of three pre-existing FFH areas that were imposed in 2005: the former site Hohenkarpfen (7918-341), the Südwestlicher Großer Heuberg (7918-342) and the Donautal und Hochflächen von Tuttlingen bis Beuron (7919-341). The merger was carried out through the Regierungspräsidium Freiburg, the regional authority responsible for the site.

Before 2005 the various landscape elements that now make up the site were already protected as individual nature reserves, including areas such as the Irndorfer Hardt, the Buchhalde-Oberes Donautal, the Stiegelesfels-Oberes Donautal and the Hohenkarpfen. After 2005 the habitats fell under the umbrella of the EU Habitats Directive through the earlier smaller FFH designations, and after 2015 they have been managed jointly as a single large-scale Natura 2000 site. The official management plan for the combined FFH area was finalised in late 2015, prepared by the planning office PAN Planungsbüro für angewandten Naturschutz on behalf of the Regierungspräsidium Freiburg.

Ecologically, Großer Heuberg und Donautal is defined by the coexistence of calcareous dry habitats, open juniper heaths, montane hay meadows and species-rich broadleaf forests. The plateau's thin, base-rich soils have produced a remarkable diversity of habitat types within a relatively compact area, including European dry heaths (4030), juniper formations on calcareous soils (5130), pioneer calcareous grasslands (6110), orchid-rich calcareous dry grasslands (6210*), species-rich Nardus grasslands on siliceous substrates (6230*) and both flatland and mountain hay meadows (6510, 6520).

Forests form an equally important component. The site includes Asperulo-Fagetum beech forests (9130), orchid-rich calcareous beech forests (9150), Galio-Carpinetum oak-hornbeam forests (9170), and the priority habitat of Tilio-Acerion slope and ravine forests (9180*). Along the Danube and its tributaries there are alluvial forests dominated by alder, ash and willow (91E0*), while in drier, more continental-influenced places one finds steppe pine forests listed as 91U0.

Wet habitats are also represented, including naturally nutrient-rich lakes (3150), rivers with Ranunculus vegetation (3260), tall-herb humid meadows (6430) and transition mires with quaking mats (7140). Calcareous springs (7220*) and limestone scree slopes (8160*) add further habitat diversity. Together these habitat types make the site a near-textbook example of the ecological mosaic that the European Habitats Directive was designed to protect.

The wildlife profile of Großer Heuberg und Donautal is shaped by the variety of habitats listed above. Calcareous grasslands, juniper heaths and cliff forests support a wide range of protected invertebrates, including the Spanish flag moth (Callimorpha quadripunctaria) and the Alpine longhorn beetle (Rosalia alpina), while the rare snail Vertigo angustior benefits from the site's humid microhabitats. The Danube and its tributaries host fish species such as the bitterling (Rhodeus sericeus) and the bullhead (Cottus gobio), along with amphibians such as the northern crested newt (Triturus cristatus).

Bats are particularly important in the area. The site regularly supports the greater horseshoe bat (Rhinolophus ferrumequinum), Bechstein's bat (Myotis bechsteinii) and the greater mouse-eared bat (Myotis myotis), often roosting in caves, balmen and old forest stands. The presence of the Eurasian beaver (Castor fiber) along the Danube adds a further conservation milestone to the area, as does the rich bryophyte flora, including Dicranum viride and Buxbaumia viridis, both indicators of old, ecologically intact forests.

Among the plants, the yellow lady's slipper orchid (Cypripedium calceolus) and the threatened grass Bromus grossus are among the most notable species of community interest recorded in the standard data form for the site. Forest herbs, orchids in beechwoods and the rich calcareous grassland flora contribute to a botanical diversity that, together with the fauna, gives the site a strong conservation identity within the broader Swabian Alb Natura 2000 network.

From a conservation standpoint, Großer Heuberg und Donautal is one of the most habitat-rich FFH sites along the southwestern Swabian Alb. Its significance rests on the unusually large concentration of Annex I habitats and Annex II species within a single Natura 2000 area, including several priority habitat types marked with an asterisk, such as orchid-rich calcareous grasslands (6210*), Tilio-Acerion slope forests (9180*), alluvial forests (91E0*), calcareous pioneer grasslands (6110*) and species-rich Nardus grasslands on siliceous substrates (6230*). The combination of these habitats within a relatively compact administrative boundary greatly increases the site's overall ecological importance.

Protection of the area is realised through the European Habitats Directive (92/43/EEC) and is nationally administered by the Regierungspräsidium Freiburg. The official management plan, completed in late 2015, coordinates habitat and species conservation across the former FFH sites Hohenkarpfen, Südwestlicher Großer Heuberg and Donautal und Hochflächen von Tuttlingen bis Beuron. Conservation measures focus on maintaining open habitats such as juniper heaths and calcareous dry grasslands, preserving old-growth forest structures for bats and bryophytes, protecting river corridors for the beaver and fish species, and integrating nineteen pre-existing nature reserves into a unified Natura 2000 framework.

Although the area is primarily recognised for its ecological value, the landscape reflects a long history of agricultural use. The juniper heaths, dry grasslands and hay meadows are not natural wilderness, but cultural landscapes that have been maintained by centuries of grazing, mowing and traditional land management. Place names such as Heuberg, literally 'hay mountain', point to the historical role of hay production in the local rural economy, while long-standing settlements such as Fridingen an der Donau, Mühlheim an der Donau and Beuron are closely tied to the Danube gorge and its historic traffic routes. The Beuron area, in particular, has long been famous for its monastery and its role in shaping the cultural identity of the Upper Danube valley.

Großer Heuberg und Donautal combines the open juniper heath and dry grassland plateau of the Großer Heuberg with the steep rocky slopes and meanders of the Upper Danube. It contains no fewer than nineteen integrated nature reserves and a remarkable range of priority habitat types under the EU Habitats Directive. Among its most distinctive features are orchid-rich calcareous grasslands, juniper heaths on limestone, beech and oak-hornbeam forests, floodplain woodlands along the Danube, and calcareous cliffs with cave vegetation. The site is particularly notable for its bat fauna, its populations of the Eurasian beaver, its populations of rare orchids such as Cypripedium calceolus, and its old-growth forest bryophytes like Buxbaumia viridis.

The character of Großer Heuberg und Donautal shifts clearly with the seasons. Late spring and early summer are the most rewarding time for the calcareous grasslands and hay meadows on the Großer Heuberg plateau, when orchids and other herb-rich flora are in full bloom and the juniper heaths contrast vividly with the flowering meadows. Summer offers the strongest experience of the Danube break-through, with the cliffs above Fridingen and Beuron best appreciated in long daylight and warm weather. Autumn is the most atmospheric season for the beech and oak-hornbeam forests, when fruiting bodies appear and the lime-rich forests turn colour. Winter brings a quieter but striking landscape of frost-covered juniper heaths and bare cliff faces along the Danube.