Public lands are typically established in recognition of their unique ecological value, yet ecological values of public lands change over time, along with human distribution and land use. These transformations are evident even in developed countries with long histories of public land management, such as the United States. The wildland-urban interface (WUI), i.e., where houses are in or near wildland vegetation, has expanded tremendously over the past two decades in the U.S., with widespread ramifications for ecological processes and functions, on public and private land, including fire regimes and wildfire management. However, it is unclear how this expansion has been located in proximity to protected areas, and relative to other intensities of land use. We analyzed WUI expansion within 10 km of all National Forests over the past two decades, focusing on National Forests because of their primary role in federal wildfire spending and because they have the highest number of private land inholdings. We used Census data on homes and National Land Cover Data on vegetation to construct the first WUI change data set from 1990-2010, at the Census block level.
Results/Conclusions
We found that housing growth within and around National Forests over the past two decades was predominantly WUI growth, with WUI homes outnumbering non-WUI homes, urban and rural combined, by 4:1. Urban development, where housing growth led to the loss of forest or grassland land cover, was rare. The WUI homes and area around National Forests in 2010 still comprised a small proportion of the national extent of WUI (16% and 20% of WUI homes and area, respectively), but WUI growth in proximity to National Forests for the past two decades exceeded national WUI growth rates. Expansion of this type of development, where homes and natural vegetation are intermingled, is likely to continue, and will have significant ecological impacts on adjacent public lands.