The wildland-urban interface (WUI) is the area where houses and wildland vegetation meet or intermingle, and where wildfire problems are most pronounced. Here we report that the WUI in the United States grew rapidly from 1990 to 2010 in terms of both number of new houses (from 30.8 to 43.4 million; 41% growth) and land area (from 581,000 to 770,000 km; 33% growth), making it the fastest-growing land use type in the conterminous United States. The vast majority of new WUI areas were the result of new housing (97%), not related to an increase in wildland vegetation. Within the perimeter of recent wildfires (1990-2015), there were 286,000 houses in 2010, compared with 177,000 in 1990. Furthermore, WUI growth often results in more wildfire ignitions, putting more lives and houses at risk. Wildfire problems will not abate if recent housing growth trends continue.
Globally, and in the US, wildfires pose increasing risk to people and their homes. Wildfire management assumes that buildings burn primarily in the wildland–urban interface (WUI), where homes are either ignited directly (especially in intermix WUI areas, where houses and wildland fuels intermingle), or via firebrands, the main threat to buildings in the interface WUI (areas with minimal wildland fuel, yet close to dense wildland vegetation). However, even urban areas can succumb to wildfires. We examined where wildfire damages occur among urban, rural and WUI (intermix and interface) areas for approximately three decades in California (1985–2013). We found that interface WUI contained 50% of buildings destroyed by wildfire, whereas intermix WUI contained only 32%. The proportion of buildings destroyed by fires among classes was similar, though highest in interface WUI areas (15.6%). Our results demonstrate that the interface WUI is where most buildings were destroyed in California, despite less wildland fuel. Continued advancement of models, mitigation and regulations tailored for the interface WUI, both for California and elsewhere, will complement the prior focus on the intermix WUI.
Over the past 30 years, the cost of wildfire suppression and homes lost to wildfire in the US have increased dramatically, driven in part by the expansion of the wildland–urban interface (WUI), where buildings and wildland vegetation meet. In response, the wildfire management community has devoted substantial effort to better understand where buildings and vegetation co-occur, and to establish outreach programs to reduce wildfire damage to homes. However, the extent to which the location of buildings affected by wildfire overlaps the WUI, and where and when outreach programs are established relative to wildfire, is unclear. We found that most threatened and destroyed buildings in the conterminous US were within the WUI (59 and 69% respectively), but this varied considerably among states. Buildings closest to existing Firewise communities sustained lower rates of destruction than further distances. Fires with the greatest building loss were close to outreach programs, but the nearest Firewise community was established after wildfires had occurred for 76% of destroyed buildings. In these locations, and areas new to the WUI or where the fire regime is predicted to change, pre-emptive outreach could improve the likelihood of building survival and reduce the human and financial costs of structure loss.
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