GEOLOGICALLY-LIMITED HABITATS IN THE NATIONAL PARK SYSTEM

The distribution and abundance of numerous rare and sensitive habitats are defined by geological conditions. Specific rock outcrops or geologic formations support unique habitats for threatened, endangered, and rare species of plants, fish and wildlife. Rare plant communities are found only on outcrops of serpentine, shale, traprock, travertine, sandstone or limestone (Great Smoky Mountains NP, Yellowstone NP, Capitol Reef NP). Sand barrens occur on glaciofluvial outwash. Caves host a number of endemic species found only in individual cave systems (Mammoth Cave NP, Russell Cave NM, Carlsbad Caverns NP). Balds are sparsely vegetated community types located on montane bare rock exposures (Great Smoky Mountains NP). Cliffs and ledges can support sparsely vegetated communities of rare plant assemblages (Capitol Reef NP). Coastal formations such as overwash fans, barrier spits, tidal flats, shoals and inlets provide essential habitats for numerous vulnerable shorebirds, waterbirds, plants and aquatic fauna (Cape Cod NS, Gateway NRA, Assateague Island NS, Cape Hatteras NS, Cape Lookout NS, Cumberland Island NS, Canaveral NS, Gulf Islands NS, Padre Island NS). Marine hardbottoms generate incredibly diverse ecosystems that require outcrops of rock, typically calcareous (Biscayne NP, Dry Tortugas NP, Virgin Islands NP, Buck Island Reef NM). Geologic structures that create particular river bottom morphology support habitats for some threatened and endangered aquatic species (Dinosaur NM). The National Park System has protected many examples of these habitats, but their geologically-limited nature poses unique resource management issues.