Using GIS to Detect Changes in Desert Tortoise Habitat from Unrectified Imagery 1982-1995

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Committee Chair

Mark P. Kumler, Ph.D.

Committee Members

Karen K. Kemp, Ph.D.
Lisa Benvenuti


Since 1990, the U.S. Army National Training Center at Fort Irwin has documented the degradation of the land and wildlife caused by human activities. The desert tortoise is one of the threatened species. According to the impacts ranked by Dr. William Boarman, a leading expert in desert tortoise biology and management, urbanization and development is a high threat and roads and highways is a medium threat.

The southeastern quadrant of the California City North quadrangle in Kern County is the study area for this project. The project data (1982 aerial photographs, a 1995 digital orthophoto quarter quadrangle, a road feature class, a point shapefile to help locate the BLM air photos in the digital raster graphic (DRG), and the digital raster graphic) were provided by the Redlands Institute. Processed with ERDAS IMAGINE 8.7, the 1982 and 1995 land use and land cover data were interpreted from the image and photographs. A land use and land cover scheme that considers factors of declining tortoise populations was developed to digitize interesting data using heads-up digitizing. Manipulated with the geoprocessing tools in ArcGIS 9.0, the land changes during those years were generated. A geodatabase was created to store interpreted photos and images, including change detection.

The increase and reclassification of the land use/land cover features are divided into four change categories: transportation routes, off-road use, residential area, and shrub and brush rangeland. These changes indicate potential urbanization of the study area. This affects the decrease in the Mojave Desert tortoise population because the tortoises’ lives are at risk, their habitats are being encroached upon, and their food supply is dwindling.

Full text is available at the University of Redlands


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