Southern Blue Ridge Ecoregion
Description & Physiography
Spanning over 9.4 million acres in size across portions of Virginia, Tennessee, South Carolina, and Georgia, with the greatest portion falling in North, the Southern Blue Ridge is one of the most biologically significant ecoregions in the United States.
The SBR ecoregion is unique because of the spatial and temporal heterogeneity of its geology, topography (slope, aspect and elevation) and floristics. This ancient remnant mountain region has undergone a myriad of geologic processes from the uplift of the earth’s crust to volcanic intrusions and alluvial depositions, while escaping glaciation in the Pleistocene Period. These processes have produced a landscape of extreme variation with elevations ranging from 1500 feet to 6684 feet at the peak of Mt. Mitchell, the highest point in the eastern United States. The substrate includes a wide range of metamorphic, acid rocks with occasional inclusions of mafic and ultramafic rocks. Moreover, the region receives the highest rainfall in the U.S. east of the Cascades, and is home to a range of climate types from warm temperate to boreal. The combination of these conditions and the fact that this region escaped glaciation has provided specialized habitat for the evolution and persistence of a vast flora and fauna, including over 400 endemic species—the most found in any ecoregion in North America
Almost 35% of the ecoregion is owned and managed by public agencies. The largest land management agency is the U.S. Forest Service (USFS), managing 26% of the land in the SBR. The extensive land ownership by public agencies and the re-growth of the forest from turn of the century logging has resulted in an ecoregion that is predominately forested.
The region receives the highest rainfall in the U.S. east of the Cascades, and is home to a range of climate types from warm temperate to boreal.
Plants & Animals
The SBR is one of the most biologically significant ecoregions in the U.S. for vascular and nonvascular plants, natural communities, amphibians, snails and neotropical migrant birds. Of the approximately 4,000 plant species occurring in the ecoregion, there are nearly 400 rare plant species and over 250 endemics. The SBR ecoregion has the second highest hardwood and conifer diversity in North America as well as the third highest number of hardwood and conifer endemics. It is the center of the world’s salamander diversity, having the highest number of snail species and endemics of any ecoregion in the U.S. Moreover, 136 natural terrestrial communities have been defined using the U.S. National Vegetation Classification and over 90% of these are considered endemic or limited to the ecoregion. Overall, 66 at-risk aquatic species occur in the ecoregion, 20 of which are federally-listed as threatened or endangered.
Several unique ecological communities are characteristic of the SBR, providing the wide diversity of habitat which supports the rich biodiversity of the ecoregion. For example, the communities found in association with the highest peaks of the SBR include relicts of the most recent Ice Age, when spruce and fir spread throughout the southern Appalachian highlands, and alpine tundra occupied slopes and peaks above 4000 feet. Some of the notable high elevation communities include spruce/fir forests, beech gap forests, high elevation rocky summits, heath and grass balds.
These communities harbor plants and animals characteristic of more northern latitudes as well as many species that are endemic to the Southern Appalachians. Another significant community type is the mountain cove forest found in cool, moist, sheltered valleys and low slopes with highly fertile soil, comprising the most diverse forests in Eastern North America. Geologic substrate define other rare communities such as serpentine barrens, shale barrens, mafic glades and woodlands, and granitic domes which provide habitat for many rare endemic and disjunct species. Non-alluvial wetlands provide habitat diversity in an ecoregion dominated by steep topography and upland habitats. These communities, including spray cliffs, mafic and calcareous fens, bogs, forested seeps, swamp-forest bog complexes, and upland pools, serve as important nodes of species diversity, and despite their very small acreage in the ecoregion, are among the most important habitats for rare plant and animal species.
Humans & History
The human population of the ecoregion is an estimated 1.3 million and the economy is dependent primarily on tourism, timber production, the nursery industry, and agriculture and grazing in the lowlands.
Overall, the SBR ecoregion is one of the more ecologically functional and intact ecoregions in the U.S. Natural disturbances such as fire, ice storms, and wind have historically been determinants of complex landscape patterns at different spatial and temporal scales. However, over the course of the past century, its ecosystems and ecological communities have been adversely affected and continue to be threatened by several anthropogenic disturbances. For example, almost all of the forests of the SBR were rapidly and intensely logged in the earlier part of the century, abruptly shifting temporal patterns of forest succession. Moreover, these patterns were forever altered by the dramatic decline of the former dominant canopy species American chestnut (Castanea dentata) over the past century due to the Chestnut blight (Endothia parasitica)—an introduced exotic pest from Asia.
A World Wildlife Fund study identified this ecoregion as globally outstanding, requiring immediate protection or restoration based on the extraordinary endemism and species richness of the forests. The SBR and surrounding Southern Appalachian mountains have been found to have some of the highest concentrations of endangered species in the United States. In addition, the ecoregion’s ecosystems and species are considered at extreme risk for biotic impoverishment due to the risk of development.