The Virginia Gap Analysis Project (VA-GAP) was initiated as a cooperative effort between the Biological Resource Division of the U.S. Geological Survey, and state, federal, and private natural resources groups in Virginia. The major objectives of the project were to (1) produce GIS-databases describing the actual land cover type, predicted distributions of terrestrial vertebrates, land ownership, and land management status at a scale of 1:100,000, (2) identify land cover types and terrestrial vertebrate species that currently are not represented or are underrepresented in areas managed for long-term maintenance of biodiversity (i.e., “gaps”), and (3) facilitate cooperative development and use of information so that institutions, agencies, and private land owners may be more effective stewards of Virginia’s natural resources. The VA-GAP project is a preliminary step toward the more detailed efforts and studies needed for long-term planning for biodiversity conservation in Virginia.

The system used to classify the land cover consisted of 26 classes (14 forest classes, 4 herbaceous/agriculture, 3 wetland, 2 developed, 1 non-vegetated, 1 open water, and 1 mixed/unknown) and 2 forest complexes. Landsat Thematic Mapper (TM) imagery from 1986 to 1994 (mostly 1992-1993), in conjunction with aerial videography and field data collection, was used to identify and map the land cover types. The mapping of wetlands was facilitated by a direct overlay of the US Fish and Wildlife Service’s National Wetlands Inventory (NWI). Topography and phenological index (related to changes in latitude, longitude, and elevation) also were important tools for mapping diverse forest types across the state. A comparison of vegetation and land cover types mapped from TM data to the known points database gave an overall accuracy of 67.5% before spatial error correction and 87.1% after correction of potential spatial errors.

Individual distributions of 566 vertebrate species (67 reptiles, 78 amphibians, 107 mammals and 314 birds) were predicted using both county occurrence records and habitat associations contained within the Biota of Virginia (BOVA) database that was set up and is maintained by the Virginia Department of Game and Inland Fisheries. Range limits of each species were delineated based on county lines and the presence of a either a “known” or “likely” occurrence of a species within each county. Within counties, species distributions were modeled based on species-land cover associations also available in BOVA that were cross-walked with the VA-GAP land cover classification system. Southeast Virginia was found to be the most diverse area of the state. Comparisons of species predicted to occur to species lists maintained for 6 sites (mammals and herpetofauna on Fort A.P. Hill; birds on 5 eastern Virginia National Wildlife Refuges) indicated an overall accuracy ranging from 76.8% to 96.2%. Uncertainties in modeling strategies and final species distribution maps are discussed.

A GIS database of private and public conservation lands was assembled in cooperation with the major federal, state, and private land management agencies managing land for conservation purposes in Virginia. Conservation lands mapped by VA-GAP make up 8.9% of the total state area. By far, the U.S. Forest Service is the largest land managing entity in Virginia, with 66% of all conservation lands mapped in VA-GAP. The Virginia Department of Game and Inland Fisheries holds the next largest amount of property with 14.5%. Of all the conservation lands mapped by VA-GAP, federal agencies control about 82% and state agencies 18%. Lands were denoted as to the degree to which they are managed for maintenance of biodiversity and long-term ecological processes. The Gap Analysis Program requires use of a 1 through 4 scale to denote high to low management for biodiversity maintenance based on legal and management status. Status 1 lands (primarily wilderness areas within National Forests) make up only 3.4% of all conservation lands, with 10.1% in Status 2 and 86.5% in Status 3. Conservation lands are concentrated primarily in the western mountainous portion of the state (98% of status 1 lands and 89% of status 3 lands), especially along the ridge tops, with only small portions of land in the central Piedmont region (1.2% of Status 3 lands, no Status 1 or 2) and eastern Coastal Plain (3% in Status 1-3). The land ownership map should not be interpreted as a legal document, but as a representation of general ownership patterns.

Only 3 land cover types in Virginia have more than 10% of their areas protected under Status 1 or 2. These are the Red Spruce-Fraser Fir type (found exclusively on mountaintops) with 80% of their distribution found in National Forests, Tupelo-Red Maple type (found in extreme southeastern Virginia) with 30% of its distribution found within the Great Dismal Swamp National Wildlife Refuge, and the Coastal Shrub type has over 10% protection afforded by the Assateague and Chincoteague Island National Seashores. Montane Mesic Coniferous, and Riparian Forest, herbaceous, and wetland (especially in central and western Virginia) types are especially underrepresented in conservation lands given their overall proportion of the landscape. When Status 3 lands are included in this analysis, many types appear protected in proportion to their distribution. However, the Riparian Forest and submontane forest (particularly deciduous) types remain poorly protected.

Of the 566 species modeled in VA-GAP, more than one-third (35%) have <1% of their predicted distribution within status 1 and 2 lands. By taxa, this represents 35.9%, 43.3%, 43.0%, and 30.3% of the total number of amphibians, reptiles, mammals, and birds respectively. Sixteen species have almost no protection (<0.1%). No species were predicted to have >50% of their distributions on status 1 and 2 lands. We identified species with moderate or restricted distributions and low representation on status 1 and 2 lands to be at greater risk. Although we did not select a specific threshold for determining significant risk, we considered any species whose protected distribution (as a percentage of all protected lands) is less than its total distribution across the state (as a percentage of the total state area) to be at increased risk. Among birds, 4 groups of species were identified as being at risk: grassland species (e.g., Bachman’s sparrow, Eastern meadowlark, upland sandpiper), agricultural/forest mix species of the Piedmont region (e.g., pine grosbeak, rough-legged hawk, rough-winged swallow), mountain species that use agricultural, open, or wetlands for some component of their habitat (e.g., common raven, willow flycatcher, warbling vireo), and agricultural/forest mix species with statewide distributions (e.g., barn swallow, sharp-shinned hawk, orchard oriole). Several reptile species also are underrepresented. The black racer, corn snake, mole kingsnake, and the southeastern crowned snake all utilize agricultural/open areas mixed with forest and, with the exception of the black racer, are all found in the Piedmont region of Virginia and eastward. The bog turtle and wood turtle (found in wetlands types of the mountains), eastern river cooter and stripe-necked musk turtle (found in waterways and riparian areas of the mountains), and the red-eared slider are turtle species with low representation on conservation lands. Most amphibian species are well represented on conservation lands, with a few widespread species (e.g., gray tree frog and spotted salamander) appearing underrepresented only because of their wide distribution and presence throughout the poorly protected Piedmont region. Mammals identified at increased risk include those that utilize agricultural and open areas (e.g., eastern harvest mouse, common muskrat, common pine vole, star-nosed mole) and those with widespread distributions that utilize agricultural-forest mixed lands (e.g., meadow vole, northern white-footed mouse, Kirtland’s short-tailed shrew). In summary, species that tend to use mountain wetland riparian areas or agricultural/open areas (esp. in the Piedmont) appear to be the least represented in conservation lands and are at greatest risk.

Important implications of this VA-GAP study can be drawn for each of the three physiographic provinces in Virginia. In the western mountain region, riparian and agricultural/open land is predominantly privately owned and poorly represented in conservation lands. Species requiring these lowland habitats typically do not receive concerted protection efforts and may be susceptible to changing land use practices such as urbanization, which typically are restricted to flatter, inter-mountain terrain. The Piedmont region in central Virginia has very little land in public ownership, regardless of the cover type, and any species or habitat type restricted to this region receives little protection. Habitat loss due to agriculture and timber production, as well as rapid urbanization, continues in this area and threatens to remove existing natural habitats. The public land on the Coastal Plain is predominantly comprised of herbaceous and forested wetlands. Very little upland is included with these properties. As a result, species requiring these habitats are not well represented in the protection network, and these species are susceptible to rapidly encroaching human development. Although this study has provided an important foundation for future land management and acquisition decision-making, it is only that – a foundation. In order to make smaller scale decisions and fine-tune the species models, more research is needed in the arenas of species/habitat relationships, fine-scale habitat delineations, and sub-parcel stewardship mapping. More detailed work in defining species ranges in Virginia will also improve prediction models.