The Forest Service and the University of Wisconsin — Madison have released scientific maps depicting the communities and lands within the wildland-urban interface across the lower 48 states. This is the first consistent nationwide representation of the interface as defined in the Federal Register and makes possible mapping and analysis at national, state and local levels.

In all, 42 million homes or 37% of the nation are in the interface. These lands comprise 273,000 square miles or 9% of the 48 states.

While this research delineates the interface, it does not depict wildland fuel conditions or wildland fire risk or define communities at risk. The risk of fire varies widely across WUI areas.

Using geographic information systems, Forest Service and university researchers integrated Census Bureau housing data and U.S. Geological Survey National Land Cover data to map the interface. While California leads the nation with more than five million homes within the interface, North Carolina has the greatest area at more than 12 million acres. In 20 states, 50% or more of all homes are in the WUI.

“Our research provides the most current data on shifting population patterns and gives us the ability to analyze the growth and size of the WUI,” said Dr. Roger Hammer, assistant professor and researcher at the University of Wisconsin's Applied Population Laboratory.

The findings include analysis of how areas burned during previous fire seasons. For example, while the devastating 2003 California wildfires affected 132,000 acres of interface areas and burned more than 3,600 structures, it represented only about 5% of Southern California's total WUI area. Analysis of the Cedar Fire in San Diego County showed nearly the entire periphery of the fire was along the interface.

This research was accomplished using National Fire Plan dollars.