1. Low-Density Urbanization and Critical Habitats
Steven Guerry
UP206a
Winter 2011

2. Objective
Highlight specific urbanized areas within Southern California where projected low-density growth is most likely to threaten critical habitats.

3. 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
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”.
- Difficulty of classifying growth.

4. Introduction to Region of Analysis
How did you determine the geographical area? To be honest, arbitrary. I like the way the straight line looks at the top.

5. Overview of Urbanized Land and Critical Habitats
Why the specific inset? While I would like to highlight critical habitats throughout Southern California, this area at first glance shows the greatest intersection between urbanized land and critical habitats.

6. Population Density vs. Total Population
It’s useful to know what density and population look like for the region in question but I would argue neither is appropriate to measure how low-density growth affects surrounding critical habitats. Density’s very definition people using a smaller amount of land and I’m focusing on areas that use land in a low-density fashion. Likewise, simple population doesn’t give you the correct information because it fails to take into account the size of census tracts in relation to population.

7. Aggregate #1
Method
Total Population of Census Tract multiplied by percentage of housing categorized as “occupied structure with 1 unit detached”
This shows where the most amount of people are living and using the greatest amount of land. It’s a contrast to the previous density slide which shows relatively little encroachment on critical habitats.

8. This indicates regions fair differently than when we looked at density
This indicates regions fair differently than when we looked at density. Darker portions of the map indicate where there is both a relatively high combination total population and single unit detached housing. These are the tracts I’d like to focus on since this is the type of housing that requires the most land area.

9. Comparison between Density and Aggregate #1

10. Aggregate #2: Growth 2010 - 2015 Projecting Low-density Growth
Based on Census estimates for 2010 and 2015
Total Population Increase multiplied by percentage increase of “occupied structure with 1 unit detached”
Exclusion: Census tracts that underwent (a) negative population growth AND (b) percentage of low-density housing decreased
Just a variation on the first aggregate to account for growth.

12. 1-mile buffer around Critical Habitats

13. Greatest Future Threats to Critical Habitats
Requirements
within 1-mile buffer of Critical Habitats
Located on land designated as urbanized by the 2000 census
Located within the top two quantiles as determined by Aggregate #2 (Total Population Growth multiplied by percentage growth of low-density housing)

15. Skills Inset Aggregating attribute fields Attribute sub-selections
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
Urban areas map further trimmed to only include urbanization within five miles of critical habitats.
Buffering
Geoprocessing
Dissolved all Census Tracts in CA into a 10-county “Southern California” region
Upper two quantiles from aggregate #2 clipped by urban areas

16. Potential Themes for Future Analysis Within Threatened Areas
Zoning
Average household income
Commuting distance to work and number of residents who work in surrounding area
Land Value
Resource consumption (energy and water)