The 2000 Wildland-Urban Interface in the U.S.

Contact: Volker C. Radeloff

Collaborators: Jason F. McKeefry, Sherry S. Holcomb, Roger B. Hammer, Susan I. Stewart

The Wildland-Urban Interface (WUI) is the area where houses meet wildland vegetation (interface WUI) or where houses and vegetation are mixed together (intermix WUI). This makes the WUI a focal area for human-environment conflicts such as wildland fires, habitat fragmentation, invasive species, and biodiversity decline. For this project we conducted a spatially detailed national assessment of the WUI across the coterminous U.S in order to provide a framework for inquiries into the effects of housing growth on the environment. We used the results of this assessment to map WUI in the coterminous US at 2000 Census block resolution. With this information we hope to inform both national policy and local land management concerning the WUI and associated issues. To accomplish our objectives, we combined housing counts from the U.S. 2000 decennial Census at the block level with vegetation data from the USGS National Land Cover Data (NLCD). We then calculated housing density and percentage of wildland vegetation for each census block, and identified the blocks within or in the vicinity of a certain threshold percentage of wildland vegetation. This enabled us to classify each block as either intermix or interface WUI or non-WUI. Non-WUI areas were heavily urbanized, had low or zero housing density, or contained non-wildland vegetation, such as agriculture, or water. Our analysis shows that across the coterminous U.S., WUI covers nearly 9% of the land area and contains 38% of all housing units. All 48 states contain WUI, but the eastern U.S. has the greatest extent of WUI. Intermix WUI accounts for the majority of WUI area (82%) nationally, and housing units are evenly split between interface and intermix WUI (51% versus 49%). State-level analysis ranks California first in number of homes in the WUI (5.1 million), North Carolina first in WUI land area (51,700 km2), Connecticut first in proportion of land in the WUI (72%), and New Hampshire first in proportion of housing units in the WUI (82%).

Acknowledgements:
This research was funded by the North Central Research Station of the U.S. Department of Agriculture Forest Service.

WUI definitions:
          Wildland-Urban Interface definitions

Publications:
Radeloff, V. C., R. B. Hammer, S. I Stewart, J. S. Fried, S. S. Holcomb, and J. F. McKeefry. 2005. The Wildland Urban Interface in the United States. Ecological Applications 15:799-805. PDF (contains color, 0.3 Mb)