Homes and forests intersect in the WUI, a geography that now includes one-third of all homes in the United States within just 10 percent of the nation’s land area. For the first time, scientists with the USDA Forest Service and the University of Wisconsin-Madison have been able to track change in the nation’s WUI over a 20-year period, revealing that new WUI area expanded by more than 46 million acres, an area that is larger than Washington State.
Wildland-urban interface is an area close to or intermingled with forests and grasslands, with at least one home per 40 acres. Scientists distinguish between “intermix” WUI, in which housing and vegetation intermingle, and “interface” WUI, where housing is near a large area of wildland vegetation. From 1990 to 2010, both types of WUI grew rapidly, increasing from 30.8 to 43.4 million homes (41 percent growth) and expanding in area from 143,568,227 acres to 190,271,144 acres (33 percent growth). Ninety-seven percent of new WUI areas were created by housing development, not an increase in wildland vegetation. The greatest expansion of WUI area occurred in the East, with the highest gains in houses and people in the South and Southwest.