This is one of the last intact active blanket bog systems in Ireland and Western Europe and is an important scientific and scenic feature of the National Park. The Park also protects a variety of other important habitats and species. These include alpine heath, upland grassland, heath and lakes and river catchments. Greenland White-fronted Geese, Golden Plover, Red Grouse and Otters are just some of the important fauna found within the Park. The National Park is itself part of the Owenduff/Nephin Complex Special Area of Conservation (SAC) and Special Protection Area (SPA). These European designations are part of the Natura 2000 Network, which protect rare and important habitats and species under the EU Habitats and Birds Directives.
There is a diversity of habitats within the National Park. On the highest peak, Slieve Carr, alpine heath is found. Other habitats include upland grassland, wet and dry heath, lakes, and the Owenduff and Tarsaghaun rivers that flow into the sea northwest of Ballycroy. However, with as much as 2000mm of rainfall per year, the predominant habitat is the active Atlantic blanket bog, which covers much of the Park area.
A variety of interesting plants are found within the bog habitat. These include spaghnum mosses, black bog rush (a notable component of Atlantic blanket bog), purple-moor grass, bog cotton, deer-grass, cross-leaved heath, bell heather, white-beaked sedge, bog asphodel, bog myrtle, orchids, lousewort, milkwort, lichens, sundew and butterwort. Sundew and butterwort are insectivorous plants that have adapted to the nutrient poor bog environment by trapping and digesting insects caught on their leaves. The blanket bog contains an extensive mosaic of bog pools, which are base poor in nutrients. They are important habitats for bog bean. In the lakes, where the diversity of plants is low, there is a well-developed flora on the margins. These include water lobelia, pipewort, common spike-rush, and bulbous rush. Rare plants found in the Park include the ivy-leaved bellflower, which flowers during July and August. This is found on wet grassland along the banks of the Tarsaghaun and Owenduff rivers.. Another rare plant, the marsh saxifrage, protected under the Flora Protection Order (1999), occurs on flushes on the blanket bog, where there is an upwelling of nutrients to the surface. Purple saxifrage, alpine meadow rue, least willow and stiff sedge are examples of rare alpine heath plant species, which have been recorded from the National Park mountains. These alpine plants are more commonly found at altitude in colder areas of Europe. The dominant plants that are also found in the mountain areas include bell and ling heather, crowberry and bilberry.
Mammal species found in the Park include the fox, badger, mountain hare, otter, and feral American mink, pygmy shrew and bat species including the most common bat found in Ireland, the pipestrelle. Non-native red deer, which were introduced in the locality of Bellacorick in recent years, can now be found on the margins of the Park. Pine marten are present in the conifer plantations on the boundary of the Park. The Owenduff and Tarsaghaun rivers are renowned for salmon and sea trout while the rivers and lakes contain brown trout. Otters feed in the rivers on eels and salmon and can be occasionally seen on the blanket bog among bog pools. The bog pools are an important habitat for much of the invertebrate life in the Park. The predatory larval stages of dragonflies and damselflies feed on waterborne insects before metamorphosing into winged adult dragonflies and damselflies. These colourful and distinctive insects are good indicators of the diversity of the Park’s ecosystem. Species found include moorland hawker, heathland skimmer, four-spotted chaser, common darter, black darter, banded jewelwing, common bluet, common bluetip, spring redtail and common spreadwing. The adult dragonflies and damselflies prey on other insects. Some species eventually lay their eggs directly into stems of vegetation in bog pools, while others scatter their eggs over the water.
The National Park supports a variety of bird species including dippers, common sandpipers, woodcock, dunlin, skylarks, meadow pipits, ravens, hooded crows and whooper swans. Birds of prey found include kestrels and sparrowhawks while rare species such as merlin and peregrine falcon are also resident. Hen harriers are winter visitors. Red grouse are resident in the Park and rely on a mix of different heights of heather. High heather provides cover from predators while young shoots are necessary for the chicks to feed on. Rarer species utilise the area either as winter feeding grounds or as summer breeding grounds. Greenland White-fronted Geese are winter visitors from Greenland and are present in the Park from October until April. They feed on the roots of bog cotton and white-beaked sedge found on quaking bog. Golden Plover are common winter visitors to Ireland but only a small population breed in the summer on the upland areas of the west of Ireland including Wild Nephin National Park.