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WWRC 96-15
Wyoming Gap Analysis


The Wyoming Gap Analysis project (WY-GAP) was initiated in 1991 as a cooperative effort between the Biological Resource Division of the U.S. Geological Survey, and state, federal, and private natural resources groups in Wyoming. The major objectives of the project were to (1) produce GIS-databases describing actual land cover type, terrestrial vertebrate species distributions, land stewardship, 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 under-represented 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 Wyoming's natural resources. The WY-GAP project is a preliminary step toward the more detailed efforts and studies needed for long-term planning for biodiversity conservation in Wyoming.

The map of actual land cover was the first GIS layer completed for WY-GAP. This data layer includes the distribution of 41 land cover types, mapped as polygons with minimum mapping units (MMU) of 100 ha for uplands and 40 ha for wetlands. Map polygons were drawn and described using manual digitizing of polygon boundaries and on-screen, visual interpretation of Thematic Mapper (TM) imagery. Attributes assigned to each polygon describe primary, secondary and "other" land cover, crown closure for forested primary types, and the types of wetlands and/or disturbance found in the polygon, if any. Polygon attributes were assigned using image interpretation, existing maps, field reconnaissance (> 16,000 km of road transects), and literature sources. Formal state-wide validation of the land cover maps was not a requirement for this phase of the project, but will be conducted in conjunction with the Colorado Gap Analysis Project (CO-GAP) in 1996-1998. Informal field checks of 1809 of the 14,490 polygons from the map by agency personnel and volunteers during the summer of 1994 indicate > 79% accuracy of primary cover mapping, but this accuracy does not have a formal statistical foundation.

Individual distributions of 445 vertebrate species were predicted using both point locality records and habitat associations. Range limits of each species were delineated within a grid of 436 hexagons (635 km2) based on > 700,000 locality records and review by > 60 local experts. Within hexagons, species distributions were modeled based on species-land cover associations, elevational restrictions, and the presence of riparian areas. Comparisons of species predicted to occur in 8 field sites to species lists maintained for the sites indicated an overall accuracy of 79.5%. Uncertainties in modeling strategies and final species distribution maps are discussed.

The Gap Analysis Program (GAP) uses a scale of 1 through 4 to denote the relative degree of management for biodiversity maintenance for each tract of land, with "1" being the highest, most permanent and comprehensive level of maintenance, and "4" being the lowest, or unknown status. Status codes were assigned to public lands cooperatively with state and federal land management agencies based on legal and intended management and using a key developed by the New Mexico Gap Analysis Project (NM-GAP). Most private lands were assigned status 3 or 4 depending on the availability of information on their intended long-term management Land management status was overlayed with land cover and vertebrate species distributions to conduct a gap analysis of Wyoming. We considered land cover types and vertebrate species as under-represented (i.e., "gaps") in management areas if < 1% or < 50,000 ha of the land they occupied or their habitat in Wyoming fell within status 1 and 2 lands.

Less than 10% of the state of Wyoming is classified as status 1 and 2 lands and 90% of these lands occur in the Greater Yellowstone Ecosystem (GYE) in the northwestern portion of the state. Seven of the 41 land cover types occur at high elevations and are well (> 50%) protected in Wyoming because they occur in national parks and wilderness areas. Sixteen (44%) of 36 natural (non-anthropogenic) land cover types have ~ 1% or < 50,000 ha of the area they occupy in status 1 and 2 lands. The highest priority for further protection is recommended for vegetated dunes, active dunes, forest-dominated riparian, shrub-dominated riparian and grass-dominated wetlands because their current protection is low and they are the most vulnerable to ongoing land management practices. Wetland types are not satisfactorily mapped at our current MMU, and further efforts are needed to provide an adequate spatial description of their location before long-term planning for their conservation can be accomplished. Bur oak woodland. Great Basin foothills grassland, xeric upland shrub, limber pine woodland, saitbush fans and flats, desert shrub, greasewood fans and flats, and unvegetated playas were identified as second in priority. Management of the last four types could easily be accommodated in conjunction to one another along topographic gradients, and the Bureau of Land Management (BLM) is likely to play an important role in their conservation since they are largely under BLM's stewardship. Because of their restricted distributions, opportunities for the conservation of bur oak and Great Basin foothills grasslands are more limited and are likely to reside with the U.S. Forest Service (USFS). Third priority for further protection is recommended for shortgrass prairie, mesic shrubland and ponderosa pine and the conservation of these types will require working cooperatively with private land owners.

On average, a smaller percent of the potential habitat of amphibians (8.8%) and reptiles (2.6%) occurs in status 1 and 2 lands than either birds (14.4% ) or mammals (14.5%). Species that have a high level of habitat protection (> 50%) were restricted to the GYE. Habitats of 6 (50 %) amphibians, 8 (31%) reptiles, 25 (22 %) mammals, and 41 (14%) birds that are not considered peripheral in Wyoming merit increased management attention. The habitat of most of these species is primarily at low elevations in the eastern portion of the state or in the Green River area where status 1 and 2 lands are uncommon. Management on multiple-use lands under the stewardship of the USPS in the Black Hills and the BLM in the Green River area, and cooperative efforts with private land owners in both the eastern portion of the state and in the Green River area, will be important to the long-term conservation of a large number of vertebrate gap species in Wyoming. Some species, such as the bats and rodents, were inadequately mapped resulting in an overestimation of habitat in status 1 and 2 lands. Additional efforts to survey and map these species will be necessary to reliably evaluate their current status.

With the completion of the Wyoming Gap Analysis Project, two initiatives have been established under the direction of the Wyoming Water Resources Center to promote the long-term maintenance and application of the WY-GAP databases. First, the Spatial Data and Visualization Cluster (SDVC) is a project funded by the National Science Foundation's Experimental Program for the Stimulation of Competitive Research (EPSCoR) program and the Wyoming Science Technology and Energy Authority (STEA) for developing spatial geologic and natural resource databases (Gloss et al. 1996). Second, a partnership with the USGS Biological Resource Division has been established to develop a Wyoming Bioinformation Node (WBN) as part of the National Biological Information Infrastructure (NBH) (Kohley et al. 1996). The purpose of the WBN is to help facilitate the dissemination and use of WY-GAP databases by developing a coordinated approach to provide increasing access to the WY-GAP and other natural resource databases.

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