20260316 15505200 1.0 FALSE Desert_Tortoise_Core_Habitat 002 410627.390294 565645.714583 3938271.297798 4134209.295059 1 Geographic GCS_North_American_1983 Angular Unit: Degree (0.017453) <GeographicCoordinateSystem xsi:type='typens:GeographicCoordinateSystem' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xmlns:xs='http://www.w3.org/2001/XMLSchema' xmlns:typens='http://www.esri.com/schemas/ArcGIS/3.5.0'><WKT>GEOGCS[&quot;GCS_North_American_1983&quot;,DATUM[&quot;D_North_American_1983&quot;,SPHEROID[&quot;GRS_1980&quot;,6378137.0,298.257222101]],PRIMEM[&quot;Greenwich&quot;,0.0],UNIT[&quot;Degree&quot;,0.0174532925199433],AUTHORITY[&quot;EPSG&quot;,4269]]</WKT><XOrigin>-400</XOrigin><YOrigin>-400</YOrigin><XYScale>999999999.99999988</XYScale><ZOrigin>-100000</ZOrigin><ZScale>10000</ZScale><MOrigin>-100000</MOrigin><MScale>10000</MScale><XYTolerance>8.983152841195215e-09</XYTolerance><ZTolerance>0.001</ZTolerance><MTolerance>0.001</MTolerance><HighPrecision>true</HighPrecision><LeftLongitude>-180</LeftLongitude><WKID>4269</WKID><LatestWKID>4269</LatestWKID></GeographicCoordinateSystem> 20260316 13243000 20260316 13243000 Jamie Weleber Death Valley National Park NEPA & GIS Specialist 760-786-3200 P.O. Box 579 Death Valley CA 92328 US 20260211 ArcGIS Metadata 1.0 Death Valley National Park 760-786-3200 P.O. Box 579 Death Valley CA 92328 US Feature Class https://deva.maps.arcgis.com https://deva.maps.arcgis.com File Geodatabase Feature Class DEVA GIS Desert Tortoise Core Habitat 2026-02-11 Death Valley National Park - NEPA & GIS Specialist National Park Service - Death Valley National Park Death Valley, California vector digital data Core habitat areas for desert tortoise (Gopherus agassizii) in Death Valley National Park. This layer identifies concentrated zones of moderate and optimal habitat quality based on a multi-variable habitat suitability index (HSI) model. Core areas represent locations where suitable habitat is spatially concentrated rather than scattered or fragmented, indicating higher-quality habitat zones for tortoise populations. The layer was derived through focal density analysis of classified habitat suitability rasters, using a 450-meter radius neighborhood (approximately 64 hectares) to identify areas where at least 40% of the surrounding landscape consists of moderate or optimal habitat. This density-based approach distinguishes between core habitat areas (concentrated suitable conditions) and edge/marginal areas (isolated or scattered suitable pixels), providing a more ecologically meaningful representation of tortoise habitat than simple pixel-based classification. Core habitat categories: - Moderate Core: Areas with concentrated moderate-quality habitat (HSI scores 2.00-2.49) - Optimal Core: Areas with concentrated optimal-quality habitat (HSI scores 2.50-3.00) The underlying HSI model integrates eight environmental variables weighted according to published desert tortoise habitat research: soil depth to bedrock (20%), winter precipitation (15%), summer precipitation (10%), elevation (18%), slope (8%), aspect (7%), surficial geology (12%), and vegetation community type (10%). The model is based on Nussear et al. (2009) methodology adapted for Death Valley conditions. This layer supports wildlife management planning, environmental compliance review (NEPA/NHPA), and conservation prioritization for desert tortoise populations in Death Valley National Park. It provides park managers and planners with a scientifically defensible representation of core tortoise habitat areas for evaluating potential project impacts, identifying conservation priorities, and supporting species management decisions. The density-based approach reduces visual clutter from thousands of fragmented pixels while maintaining ecological relevance by focusing on spatially concentrated habitat zones. Created by Jamie Weleber (NEPA & GIS Specialist, Death Valley National Park) using habitat suitability modeling methodology adapted from Nussear et al. (2009). Input data sources: USGS surficial geology, PRISM climate data, USGS 3DEP elevation, NPS Vegetation Mapping Inventory (Cogan 2024). Jamie Weleber Death Valley National Park NEPA & GIS Specialist 760-786-3200 P.O. Box 579 Death Valley CA 92328 US Death Valley National Park California Nevada Mojave Desert Inyo County San Bernardino County Nye County desert tortoise Gopherus agassizii habitat suitability wildlife habitat core habitat focal density habitat modeling threatened species Mojave Desert species management environment biota ISO 19115 Topic Categories desert tortoise Gopherus agassizii habitat suitability wildlife habitat core habitat focal density habitat modeling threatened species Mojave Desert species management environment biota Death Valley National Park California Nevada Mojave Desert Inyo County San Bernardino County Nye County The National Park Service shall not be held liable for improper or incorrect use of the data described and/or contained herein. These data are not legal documents and are not intended to be used as such. The information contained in these data may be dynamic and could change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and consistent with the limitations of geospatial data in general and these data in particular. The related graphics are intended to aid the data user in acquiring relevant data; it is not appropriate to use the related graphics as data. The National Park Service gives no warranty, expressed or implied, as to the accuracy, reliability, or completeness of these data. It is strongly recommended that these data are directly acquired from an NPS server and not indirectly through other sources which may have changed the data in some way. Although these data have been processed successfully on computer systems at the National Park Service, no warranty expressed or implied is made regarding the utility of the data on other systems for general or scientific purposes, nor shall the act of distribution constitute any such warranty. This disclaimer applies both to individual use of the data and aggregate use with other data. The National Park Service shall not be held liable for improper or incorrect use of the data described and/or contained herein. These data are not legal documents and are not intended to be used as such. The information contained in these data may be dynamic and could change over time. The data are not better than the original sources from which they were derived. It is the responsibility of the data user to use the data appropriately and consistent with the limitations of geospatial data in general and these data in particular. Esri ArcGIS Pro 3.3.0 true -117.58 -115.63 37.20 35.60 publication date 2026-02-11 METHODOLOGICAL BACKGROUND: Traditional raster-to-polygon conversion of habitat suitability models produces thousands of small, fragmented polygons that do not reflect how desert tortoises actually use landscape-scale habitat. Desert tortoises require contiguous areas of suitable habitat within their home ranges (typically 20-50 hectares), making habitat concentration and connectivity more important than isolated pixels of suitable conditions. WORKFLOW SUMMARY: Step 1 - HSI Model Creation: Eight environmental variables were processed to 30-meter resolution and classified into suitability scores (1=Poor, 2=Moderate, 3=Optimal): • Soil depth to bedrock - derived from USGS surficial geology mapping (94 geologic units classified by depth) • Winter precipitation - PRISM 30-year normals (November-April) • Summer precipitation - PRISM 30-year normals (May-October) • Elevation - 30m DEM from USGS 3DEP • Slope - calculated from 30m DEM • Aspect - calculated from 30m DEM • Surficial geology - substrate permeability and thermal properties • Vegetation - NPS Vegetation Mapping Inventory (creosote-burrobush communities, density classes) Variables were combined using weighted overlay with published tortoise habitat model weights (Nussear et al. 2009). The continuous HSI output (1.0-3.0) was classified into Poor (<2.0), Moderate (2.0-2.49), and Optimal (≥2.5) habitat categories. Step 2 - Binary Raster Creation: Moderate and Optimal habitat classes were extracted into separate binary rasters (1=habitat present, 0=habitat absent), isolating pixels meeting each quality threshold. Step 3 - Focal Density Analysis: Focal statistics with a 450-meter circular neighborhood (15 cells at 30m resolution) calculated the proportion of surrounding area classified as habitat for each pixel. This radius approximates small desert tortoise home ranges and captures local habitat concentration patterns. The density output ranges from 0.0 (no habitat in neighborhood) to 1.0 (100% habitat coverage). Step 4 - Core Area Definition: A 40% density threshold was applied to identify core habitat areas. Pixels where ≥40% of the surrounding 450m radius consists of moderate or optimal habitat were classified as "core" areas. This threshold balances ecological relevance (sufficient habitat concentration to support tortoise populations) with spatial coverage (identifying meaningful core zones without excessive fragmentation). Step 5 - Polygon Conversion: Core area rasters were converted to simplified polygon features using single outer part geometry. The RasterToPolygon tool with simplification reduces vertex density while preserving essential polygon boundaries. Step 6 - Attribute Enhancement: Polygons were attributed with habitat category (Moderate Core or Optimal Core), calculated area measurements (acres and hectares), and descriptive fields for management applications. PARAMETER JUSTIFICATION: Neighborhood Radius (450m): Selected to approximate small desert tortoise home ranges (20-50 hectares) and capture local habitat patterns. Smaller radii (<300m) produced excessive fragmentation; larger radii (>600m) over-smoothed important habitat gradients. Density Threshold (40%): Balances ecological significance with spatial coverage. Higher thresholds (50-60%) identified only the densest core zones but excluded substantial areas of concentrated habitat. The 40% threshold captures areas where habitat is clearly concentrated rather than scattered while maintaining conservative criteria for "core" designation. LIMITATIONS AND APPROPRIATE USE: This layer identifies core habitat zones at the landscape scale (30m resolution with 450m focal analysis). It is appropriate for: • Regional planning and prioritization • NEPA compliance review for project-level analysis • Identifying potential restoration or conservation areas • General tortoise habitat mapping It is NOT appropriate for: • Fine-scale site-specific decisions (<1 hectare) • Individual tortoise location prediction • Regulatory take determinations (requires field surveys) • Year-to-year population monitoring (static model based on environmental variables) Field validation is recommended for projects within or adjacent to core habitat areas. The model does not account for temporal variation in habitat quality (e.g., drought effects on forage), anthropogenic disturbances (roads, developments), or direct tortoise population data. RELATED DATASETS: Users should also reference: • DEVA_Tortoise_HSI_Classified_Final (underlying classified habitat suitability raster) • DEVA_Tortoise_HSI_Continuous (continuous suitability scores 1.0-3.0) • Individual environmental variable layers (soil depth, precipitation, vegetation, etc.) • Known tortoise observation locations (if available and permitted for sharing) DATA QUALITY STATEMENT: Input data sources vary in resolution, accuracy, and collection date: • Soils: Derived from 1:100,000 surficial geology mapping (USGS) • Climate: PRISM 30-year normals (800m resolution, resampled to 30m) • Vegetation: NPS Vegetation Mapping Inventory (2019-2020 NAIP imagery, 82% thematic accuracy) • Topography: USGS 3DEP 30m DEM (vertical accuracy ~7m RMSE in desert terrain) The model assumes current environmental conditions and does not project future climate scenarios or landscape changes. Periodic updates are recommended as improved data sources become available (e.g., updated vegetation mapping, refined climate data). SCIENTIFIC REFERENCES: Nussear, K.E., T.C. Esque, R.D. Inman, L. Gass, K.A. Thomas, C.S.A. Wallace, J.B. Blainey, D.M. Miller, and R.H. Webb. 2009. Modeling habitat of the desert tortoise (Gopherus agassizii) in the Mojave and parts of the Sonoran Deserts of California, Nevada, Utah, and Arizona. U.S. Geological Survey Open-File Report 2009-1102. Longshore, K.M., J.R. Jaeger, and J.M. Sappington. 2003. Desert tortoise (Gopherus agassizii) survival at two eastern Mojave Desert sites: death by short-term drought? Journal of Herpetology 37:169-177. USFWS. 1994. Desert Tortoise (Mojave Population) Recovery Plan. U.S. Fish and Wildlife Service, Portland, Oregon. Cogan, D. 2024. Vegetation Classification and Mapping Project Report, Death Valley National Park. Natural Resource Report NPS/SR—2024/223. National Park Service, Fort Collins, Colorado. METADATA CONTACT: Jamie Weleber NEPA & GIS Specialist Death Valley National Park P.O. Box 579 Death Valley, CA 92328 Phone: 760-786-3200 Email: via NPS DEVA main contact 1 -118.009091 -116.258781 37.354589 35.584126 Attribute accuracy is dependent on the accuracy of source data layers and the appropriateness of model parameters. Habitat categories (Moderate Core, Optimal Core) are based on density thresholds (40%) applied to habitat suitability classifications. The 40% threshold was selected through iterative testing to balance ecological relevance with spatial coverage. Area calculations (ACRES, HECTARES) are derived from polygon geometry and are accurate to the precision of the coordinate system (NAD 1983 UTM Zone 11N). Polygon topology has been validated. All features are single-part polygons with no gaps or overlaps between Moderate Core and Optimal Core categories. Each polygon has complete attribute values for Habitat_Category, ACRES, and HECTARES fields. Core habitat areas are mutually exclusive (a given polygon cannot be both Moderate Core and Optimal Core). This layer includes all core habitat areas meeting the 40% density threshold for moderate and optimal habitat categories within Death Valley National Park boundaries. Areas classified as Poor habitat (HSI < 2.0) are not included. The layer does not represent all suitable habitat in the park, only areas where suitable habitat is spatially concentrated. Edge and scattered habitat zones are excluded by design. Horizontal positional accuracy is dependent on source data layers, particularly the 30-meter DEM and vegetation mapping. The underlying HSI model uses 30-meter resolution rasters aligned to USGS 3DEP standards. Focal density analysis using 450-meter neighborhoods smooths fine-scale positional errors but does not improve absolute accuracy. Polygon boundaries are approximate representations of habitat concentration zones and should not be interpreted as precise habitat edges. Estimated horizontal accuracy: ±50 meters for polygon boundaries. Eight environmental variables were processed to 30-meter resolution with consistent extent and spatial reference (NAD 1983 UTM Zone 11N, EPSG 26911): soil depth, winter precipitation, summer precipitation, elevation, slope, aspect, geology, and vegetation type. Each variable was classified into suitability scores (1=Poor, 2=Moderate, 3=Optimal) based on desert tortoise habitat requirements from published literature. 2026-01-05 Jamie Weleber Death Valley National Park Weighted overlay analysis combined eight suitability variables using published model weights: soil depth (20%), winter precipitation (15%), summer precipitation (10%), elevation (18%), slope (8%), aspect (7%), geology (12%), vegetation (10%). Output continuous HSI values (1.0-3.0) were reclassified into Poor (<2.0), Moderate (2.0-2.49), and Optimal (≥2.5) categories. Output: DEVA_Tortoise_HSI_Classified_Final. 2026-01-10 Jamie Weleber Death Valley National Park Created binary rasters for Moderate and Optimal habitat classes using conditional statements (Con tool). Pixels classified as Moderate (value=2) or Optimal (value=3) were assigned value=1; all other pixels assigned value=0. Output: Moderate_Binary and Optimal_Binary rasters. 2026-01-11 Jamie Weleber Death Valley National Park Calculated focal density using Focal Statistics tool with circular neighborhood (radius=15 cells at 30m resolution = 450 meters). Statistics type=MEAN calculated the proportion of the neighborhood classified as habitat (range 0.0-1.0). Output: Moderate_Density and Optimal_Density rasters showing habitat concentration gradients. 2026-01-11 Jamie Weleber Death Valley National Park Applied 40% density threshold to identify core habitat areas. Pixels with density ≥0.40 (40% or more of surrounding 450m neighborhood is suitable habitat) were classified as core areas (value=1); pixels below threshold classified as non-core (value=0). Output: Moderate_Core and Optimal_Core rasters. 2026-01-11 Jamie Weleber Death Valley National Park Converted core area rasters to polygon feature classes using Raster to Polygon tool with simplification and single outer part geometry. Added attribute fields: Habitat_Category (text), ACRES (double), and HECTARES (double). Calculated geometry attributes for area measurements. Output: Moderate_Core_Polygons and Optimal_Core_Polygons. 2026-02-11 Jamie Weleber Death Valley National Park Merged Moderate_Core_Polygons and Optimal_Core_Polygons into single feature class. Final output: DEVA_GIS_Desert_Tortoise_Core_Habitat containing all core habitat polygons with habitat category attributes. 2026-02-11 Jamie Weleber Death Valley National Park Surficial geology mapping (94 geologic units) used to derive soil depth to bedrock classifications Surficial Geology Mapping, Death Valley Region USGS Geology USGS vector digital data ground condition 1990 2010 Winter and summer precipitation 30-year normal datasets (800m resolution) PRISM Climate Data: 30-Year Normals PRISM Climate 2024 PRISM Climate Group, Oregon State University raster digital data ground condition 1991 2020 30-meter elevation data used for elevation, slope, and aspect calculations USGS 3D Elevation Program (3DEP) 1/3 arc-second DEM USGS DEM 2023 USGS raster digital data publication date 2023 Vegetation mapping inventory (90 map units, 82% thematic accuracy) used to identify creosote-burrobush communities and vegetation density classes Death Valley National Park Vegetation Classification and Mapping NPS Vegetation 2024 National Park Service vector digital data Natural Resource Report NPS/SR—2024/223 ground condition 2019 2020 0 DEVA_GIS_Desert_Tortoise_Core_Habitat Core habitat areas for desert tortoise based on focal density analysis of habitat suitability model outputs Death Valley National Park Feature Class 0 OBJECTID Internal feature number Esri Sequential unique whole numbers that are automatically generated OBJECTID OID 4 0 0 Shape Feature geometry Esri Coordinates defining the polygon features Shape Geometry 0 0 0 Id Id Integer 4 0 0 gridcode gridcode Integer 4 0 0 Habitat_Category Classification of core habitat quality based on underlying HSI scores Death Valley National Park Moderate Core Areas where at least 40% of the surrounding 450m neighborhood consists of moderate-quality habitat (HSI scores 2.0-2.49). Represents concentrated zones of habitat with moderate suitability for desert tortoise populations. Death Valley National Park Optimal Core Areas where at least 40% of the surrounding 450m neighborhood consists of optimal-quality habitat (HSI scores 2.5-3.0). Represents concentrated zones of highest-quality habitat conditions for desert tortoise populations. Death Valley National Park Habitat Designation String 50 0 0 ACRES Area of the core habitat polygon in acres Death Valley National Park 0.01 varies acres ACRES Double 8 0 0 HECTARES Area of the core habitat polygon in hectares Death Valley National Park 0.01 varies hectares HECTARES Double 8 0 0 Shape_Length Perimeter length of polygon feature Esri Positive real numbers that are automatically generated Shape_Length Double 8 0 0 Shape_Area Area of polygon feature in square meters Esri Positive real numbers that are automatically generated Shape_Area Double 8 0 0 globalid globalid GlobalID 38 0 0 Priority Priority String 20 0 0 Description Description String 500 0 0 dataset EPSG 6.5(3.0.1) Simple FALSE 0 TRUE FALSE