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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. |
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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. |
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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). |
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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. |
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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. |
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DEVA GIS Desert Tortoise Core Habitat |
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["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"] |
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en-US |
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