Why focus on low-density residential buildings? Low-density housing by definition requires more land Low-density rural home development is the fastest-growing form of land use in the United States since 1950.* Developed with the automobile in mind, low-density residential housing requires land-intensive automobile infrastructure like roads and parking Attracts low-density commercial development * http://www.esajournals.org/doi/full/10.1890/05-5221 Many native species have reduced survival and reproduction near homes* Recent trends suggest people are moving to rural areas to live in low-density housing Exurban development has a large potential to alter biodiversity* Residential development poses a significant threat to native biodiversity
Mapping Definitions and Metrics Urbanization and Growth (Source: U.S. Census Bureau) Areas categorized as “urbanized” in 2000 Population Density in 2000 Projected Total Population Growth for 2010 and 2015 Low-Density (Source: U.S. Census Bureau) Percentage of housing composed of detached single-unit structures will serve as a proxy of overall low-density development. Critical Habitats (U.S. Department of Fish and Wildlife) Areas the Endangered Species Act deems “(I) essential to the conservation of the species and (II) which may require special management considerations or protection” for species classified as “Endangered” or “Threatened”.
Aggregate #1 Method Purpose To show where low-density development is most intense Total Population of Census Tract multiplied by Percentage of housing categorized as “occupied structure with 1- unit detached”
Aggregate #2: Projecting Growth Methodology Based on Census estimates for 2010 and 2015 Purpose Show where the greatest level of low-density development is expected. Exclusion: Census tracts that underwent (a) negative population growth AND (b) percentage of low-density housing decreased Total Population Increasemultiplied by Percent Increase of “occupied structure with 1-unit detached”
Isolate the Areas of Low-Density Growth in Existing Urbanized Areas
Areas of Growth within 1-mile of Critical Habitats Over-layed on Urbanized Areas
Where is it most urgent to set limits on growth? 1. Within 1 mile of a critical habitat 2. Designated as urbanized by 2000 Census 3. Exhibits greatest trend of land intensive (low- density) growth * http://www.esajournals.org/doi/full/10.1890/05-5221 Why limit growth and not just promote density?
GIS Skills Inset Aggregating attribute fields Attribute sub-selections o Urban areas map was created by selecting areas classified as “urban” (U) from a map featuring both urban and rural areas. Boundary sub-set selections o Urban areas map further trimmed to only include urbanization within five miles of critical habitats. Distance o Buffering Extracting Information from a buffer Geoprocessing o Dissolved all Census Tracts in CA into a 10-county “Southern California” region o Upper two quantiles from aggregate #2 clipped by urban areas Charts Elevation Google Mash-up