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Southwest Regional Gap Analysis Project: The Nevada Ecoregional Component

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Nevada Geospatial Data Browser


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References and Reports

Clark County, NV/Eastern Mojave Ecoregion Report: Habitat Distribution Models for 37 Vertebrate Species in the Mojave Desert Ecoregion of Nevada, Arizona, and Utah (PDF) (156 pp. 5.28MB), EPA/600/R-08/117, October 2008.

Special SWReGAP Session (IALE Annual Symposium - March 30–April 2, 2004, Las Vegas, NV) [PDF, 8 pp., 135 KB]

Southwest Regional Gap Analysis Project


The Gap Analysis Program (GAP) is a national program of the U.S. Geological Survey (USGS) Biological Resources Discipline that maps the distribution of plant communities and selected animal species and compares these distributions with land stewardship to promote conservation by providing broad geographic information on biological diversity to resource managers, planners, and policy makers who can use the information to make informed decisions. GAP uses satellite imagery and Geographic Information System (GIS) technology to assemble and view large amounts of biological and land management data to identify areas (gaps) where conservation efforts may not be sufficient to maintain diversity of living natural resources.

Historically, GAP has been conducted on an individual state basis. Because of differences among the states in the imagery used for mapping and differences in mapping and modeling protocols, mapped distributions of vegetation types and animals species are often surprisingly inconsistent across state lines. Moreover, the vegetation is not classified the same among the states. In response to these limitations, GAP has embarked on a second-generation effort to conduct the program at a regional scale using 1) a vegetation classification scheme applicable across the U.S.; 2) ecoregional units as the basis for segmenting the landscape into manageable units; and 3) interagency investigator teams with land cover analysis, habitat modeling, and environmental management expertise. The program’s first formalized multi-state regional effort includes the five states ( Arizona, Colorado, Nevada, New Mexico, and Utah) comprising the Southwest Regional Gap Analysis Project (SWReGAP).

NERL-ESD-Las Vegas began leading the Nevada portion of the SWReGAP Project in September 2000. Project responsibilities during the initial year included building a cooperative network, field data acquisition, and providing assistance to the regional laboratory for imagery analysis (RS/GIS Lab at Utah State University). The majority of imagery organization and pre-processing during the first year was completed by the regional lab, based on Landsat 7 TM satellite data (Figure 1) acquired during 1999-2001 by the USGS EROS Data Center (Figure 2). Classification of land cover was conducted by ESD-Las Vegas within individual mapping zones that reflect ecoregional units, many of which extend across state boundaries. Fifteen mapping zones were consolidated into five mega-map zones that lie mostly in Nevada and comprise the responsibility of the Nevada team. Land cover was classified to the "Ecological System" level using the national classification scheme developed by NatureServe. Based on land cover mapping and other data sets, wildlife habitat models were developed and mapped by the SWReGAP investigator group for 819 terrestrial vertebrate species that reside, breed, and use habitat in the 5-state area for a substantial portion of their life history, including important migration stopovers. Approximately 520 species are estimated to occur within the state of Nevada.







Clark County, NV/Eastern Mojave Ecoregion Report

Vertebrate species in the Clark County Multiple Species Habitat Conservation Plan (MSHCP) were previously modeled through the Southwest Regional Gap Analysis Project (SWReGAP, Prior-Magee et al. 2007) using a deductive approach. To increase the applicability of such habitat models to the MSHCP, we revised these 37 deductive models specific to the Mojave Desert Ecoregion using additional information and finer scale datasets that were not available for the original SWReGAP models (e.g., SSURGO [soils], mesquite/acacia). We also explored an inductive modeling approach (Maximum Entropy) using locality records for four species: desert iguana (Dipsosaurus dorsalis), common chuckwalla (Sauromalus ater), phainopepla (Phainopepla nitens), and desert kangaroo rat (Dipodomys deserti).

For the four species addressed by inductive modeling, locality records were obtained from a number of sources and varied considerably in accuracy. Inductive modeling was an iterative process using these locations and available datasets from SWReGAP and more localized datasets specific to the Mojave Desert Ecoregion. Area-Under-the-Curve (AUC) values ranged from 0.750 to 0.951 for the four species with omission error rates ranging from 11% to 67%. The final models corroborated the deductive models in the sense that environmental variables in the inductive models generally included the major variables in the deductive models. The habitat distributions predicted by the inductive models largely overlapped that predicted by the deductive models, but for three of the four species the extent of predicted habitat differed considerably between the two types of models. Future improvement of the inductive models will require obtaining more accurate species locality records, identifying habitat associations that can be mapped, obtaining better digital datasets for key habitat features, and conducting ground-based accuracy assessments. All deductive (original and modified) and the inductive habitat models and datasets for this project can be downloaded from: http://fws-nmcfwru.nmsu.edu/kboykin/MSHCP/Index.htm.Exit EPA Disclaimer

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