The core area “steep slopes north of the Edersee” is characterized by the last remnants of real virgin forests. The steep slopes, which are difficult to access, are characterized by a mosaic of oak, beech and hornbeam dry forests, hardwood log and ravine forests as well as rocky and rubble plains and log heaps. Biotopes of national importance (value level 20) are located on over 209% (5 ha) of the area. Jungle relict species such as the hermit (Osmoderma eremita) or the violet-blue root-neck beetle (Limoniscus violaceus) were able to survive here and are representative of many other xylobiont beetle species. A botanical treasure of the rocky meadows is the rare Pentecost carnation.

In order to improve and preserve habitats, large-scale process protection was implemented as a practical model for “networking and optimization of virgin forest sites” in the large-scale nature conservation project in collaboration with the large forest owners and the Vöhl Forestry Office. In the predominantly forest-dominated complex of measures, the focus of the work carried out was on process protection and the restoration of near-natural forest complexes and special locations such as rocky areas. Non-native conifers were removed using complex special technology, partly due to the steep terrain, and forest stands were developed according to the potential natural vegetation.

The development and promotion of extensive grassland management of lean grassland biotopes on base-rich sites played an important role, particularly in the open land measure complexes, but also in measure complexes with a proportion of open land. The focus of the work here was on bush removal measures and agreements with managers.

In autumn 2020, the entire core area was declared part of the National Park Kellerwald-Edersee expelled.

Covering an area of ​​7.688 hectares, the national park protects one of the last large, natural beech forest stands in Central Europe. In addition to the acidic beech forests, dry, warm extreme locations, rocks and log heaps can be found here and there. The award in 2011 by UNESCO as a world natural heritage site "Primeval Beech Forests of the Carpathians and Old Beech Forests of Germany" for parts of the national park, the high proportion of old and dead wood and the large uncut area further emphasize the importance of the area.

At the beginning of the implementation phase of the large-scale nature conservation project, extensive water ecological measures were carried out in the core area “Kellerwald-Edersee National Park”. The focus was on hydromorphological measures to improve the permeability of the low mountain streams Banfe, Keßbach and Heimbach. Dams and pipes were removed and fords and wooden bridges were created instead, and adjacent floodplains were modeled or watered. By improving the continuity of rivers, the networking function of rivers as linear landscape elements increases. As valuable species listed in Annex II of the Habitats Directive, the stream lamprey and bullhead in particular benefit from the measures.

Furthermore, the planned measures to promote the Whitsun rock meadows (national species of responsibility) and dry forests (hawkweed-sessile oak forest) were fully implemented in the measures area “Ptecostal rock meadows on Bloßenberg” and are being expanded to neighboring areas by the national park. Special technology was sometimes used to remove the planted or naturally flown conifers and the trees were gently removed from the steep slopes using a helicopter.

For the area of ​​measures at “Fahrentriesch”, an open area complex interspersed with historic hate trees, in combination with the Altenlotheimer Heiden in the border area, the implementation of the development measures (exemption/bush removal, clearing of pests and grazing) was partly implemented with volunteer supporters, while the Financing and planning of the measures was guaranteed via the NGP.

Overall, the planned measures in the national park were almost completely implemented. The expansion and regeneration of the Triescher was complemented by a Hessian arnica species protection project.

The core area “Frankenau and Wesetal” differs significantly from the other three core areas with its large proportion of open land.

The varied cultural landscape is characterized by numerous valleys with natural watercourses and a high proportion of extensively used meadows and pastures. The well-structured Wesebach and a wet meadow complex in the Weidengrund achieve the highest value due to their faunistic and floristic features. Silicate lean grasslands and heaths with development potential enrich the value of the natural area.

Bristly grass lawns, juniper heaths, wet meadows and hedges contribute to the good structure of the funding area. Individual forest complexes with valuable springs, wet and floodplain forests, log heaps and rocky cliffs as well as individual remnants of former forms of use such as low, medium and high forest management complement the open land biotopes.

As a rural low mountain landscape, the focus of the measures was on the development and promotion of extensive grassland biotopes such as species-rich submontane smooth oat meadows, red fescue poor meadows, wet and alluvial meadows as well as bristly grass lawns and heaths. To the east of Frankenau there are several complexes of measures that can be summarized as the “arch landscape near Frankenau”. By purchasing land as part of land consolidation, a large number of areas in this area have already been renatured and further developed. In particular, bush removal measures and intensive cooperation with the managers of the open areas have been and will continue to be major work-intensive focuses in the future. In open areas, continuous extensive management of the areas is important for the preservation of biotopes and species and can therefore be viewed as a permanent task that can never be completed. The creation of Hesse's first Arche region according to the GEH standard (Society for the Preservation of Old and Endangered Domestic Animal Breeds) and networking with regional development and value creation initiatives play a role in long-term security of care and use measures as well as operational and framework structures Advising land users plays a central role.

The small-scale structures in the core area also include some forest areas and complexes of measures with different objectives. A challenge in implementation was the different ownership structures and, in some cases, the owners' lack of willingness to implement the measures.

What should be highlighted in this core area is the very positive development in terms of the identity and awareness of the local people for a unique space in the cultural landscape. With the founding and establishment of the Arche Association, the Arche Path and the Archetag, which takes place every two years, a significant step was taken towards the preservation of old farm animal breeds.

Extensive, beech-rich deciduous and mixed forests determine the image of the central and southern cellar forest. Here, due to base-rich locations, demanding, partly geophyte-rich forests of the 'woodruff beech forest' type (and related communities) are quite widespread and developed extensively. Orchid and pea-beech forests occur in intercalated areas of Devonian limestone in the breakthrough of the central Urff valley. The highest point in the nature park is marked by the large, closed deciduous forest complex of the eponymous “Hohen Keller”. Along the striking quartzite ridge (desert garden), forest border stages as well as dwarf shrubs and sour humus lawns occur. In the Hoher Keller there are numerous wet forests characterized by springs, watercourses and moors.

Extensive nature conservation measures have been implemented, particularly in the state forest. Between 2012 and 2016, large areas of spruce trees were removed from the “Desert Garden and Ridge” complex and the quartzite ridge and block heaps were cleared. Since then, a natural rowan-birch successional forest has developed.

The renaturation of the streams (e.g. Koppbach, Schieferrainsgraben) was carried out from 2012 to 2014. The gradual moorland revitalization was designed in cooperation with the Kassel Nature Conservation Authority and the Jesberg Forestry Office. The continuity of the Urff has also been improved. A lot has been achieved in the area of ​​public relations with the creation of a “moor path”, a boardwalk and the “Wildromantisches Urfftal” hiking trail as well as the development of a visitor guidance concept for the Hoher Keller.

The “nature conservation-optimized forest management” formulated in the application over a large area was difficult to implement due to the controversial definition of this form of management and the lack of consent from the forest owners. Instead, however, process protection areas were designated on an area of ​​45 hectares in return for compensation. With the additional areas brought in by the state of Hesse, a total of 280 hectares of process protection areas were established.