00 250 250 500 500 km km

Scale: 1:7,143,240

Projection: Albers Equal Area

Central Meridian: 98.35° W

Latitude of Origin: 39.5° N

Datum: NAD 1983

Cartography by the University of Wisconsin Cartography Lab

This assessment was conducted by the Silvis Lab. 

All data can be downloaded at http://www.nrs.fs.fed.us/data/WUI.

Forest Service Northern 

Research Station

Research Map

NRS-8

Publication Date 

June 2015

United States Department of Agriculture

The 2010 Wildland-Urban Interface of the Conterminous United States

Wildland-Urban Interface (WUI)

Non-WUI Vegetated

Non-vegetated or Agriculture

Interface

Intermix

No housing

Water

Medium and high housing density

Very low housing density

Low and very low housing density

State Border

Wildland-Urban Interface (WUI)

Non-WUI Vegetated

Non-vegetated or Agriculture

Interface

Intermix

No housing

Water

Medium and high housing density

Very low housing density

Low and very low housing density

State Border

20%

14%

2%

4%

60%

Housing Units

2%

8%

33%

29%

24%

2%

2%

Area

19%

13%

2%

6%

60%

Population

 Geographic extent Houses Population

 km2 % Total % of U.S. Total % of U.S.

Conterminous U.S. 7,827,696 100.0 130,878,255 100.0 306,675,006 100.0

WUI 771,066 9.9 43,832,007 33.5 98,714,846 32.2

 Interface WUI 157,619 2.0 25,911,583 19.8 59,422,925 19.4

 Intermix WUI 613,447 7.8 17,920,424 13.7 39,291,921 12.8

The 2010 WUI in Numbers: Area, Houses, and Population in the WUI

0

10,000

20,000

30,000

40,000

60,000

80,000

100,000

Area of Fires (km2

)

Number of Fires

2002 2003 2004 2005 2006 2007 2008 2009 2010

Wildfire History

Map Description

The wildland-urban interface (WUI) is the area where 

structures and other human development meet or 

intermingle with undeveloped wildland, and it is a 

significant zone for wildfire management and impact (Bar 

Massada et al. 2014, Radeloff et al. 2005, Syphard et al. 

20091

). This map displays the extent of the WUI in the 

conterminous United States for the year 2010.

Defining the WUI

The WUI is composed of both interface and intermix 

communities (Stewart et al. 20071

). In the WUI, housing 

must meet or exceed a minimum density of 6.18 houses 

per km2

 (one structure per 40 acres). The distinction 

between interface and intermix is based on the 

distribution of houses and wildland vegetation across 

the landscape. Intermix WUI is where housing and 

vegetation intermingle, while in interface WUI, housing is 

in the vicinity of a large area of wildland vegetation. Areas 

that do not meet the WUI requirements represent other 

land-use classes.

Land Use Definitions

WUI

• Intermix: Area with ≥6.18 houses per km2

 and ≥50 

percent cover of wildland vegetation.

• Interface: Area with ≥6.18 houses per km2 and <50 

percent cover of vegetation, located <2.4 km of an 

area ≥5 km2 in size that is ≥75 percent vegetated.

Non-WUI, Vegetated

• No Housing: Area with ≥50 percent cover of wildland 

vegetation and no houses (e.g., protected areas, steep 

slopes, mountain tops).

• Very Low Housing Density: Area with ≥50 percent 

cover of wildland vegetation and <6.18 houses per km2

(e.g., dispersed rural housing outside neighborhoods).

Non-Vegetated or Agriculture

• Low and Very Low Housing Density: Area with 

<50 percent cover of wildland vegetation and 

<49.42 houses per km2 (e.g., agricultural lands and 

pasturelands).

• Medium and High Housing Density: Area with <50 

percent cover of wildland vegetation and ≥49.42 

houses per km2

 (e.g., urban and suburban areas, 

which may have vegetation but not dense vegetation).

Mapping Approach

Mapping the WUI requires spatially explicit information 

on housing density and wildland vegetation cover. We 

used housing density information from the 2010 U.S. 

Census (http://www2.census.gov/census_2010/04-

Summary_File_1) at the census block level, and 

wildland vegetation cover from the 2006 National Land 

Cover Dataset (http://www.mrlc.gov/nlcd2006.php).1

“Wildlands” represent vegetation cover types for which 

human manipulation is minimal, including forests, native 

grasslands, shrubs, and wetlands. 

1 See Literature Cited in main document for full citations.

Data Sources

Shapefiles for North America and major cities from 

Natural Earth Data version 2.0.0. 

The Great Lakes and state boundaries taken from Natural 

Earth Data version 3.0.0. All Natural Earth Data from 

www.naturalearthdata.com accessed 6/17/2014.

Fire data from National Interagency Fire Center 

(http://www.nifc.gov). Layers of WUI and non-WUI 

classes were developed by this study.