Defensible-space treatment of < 114,000 ha 40 m from high-risk buildings near wildland vegetation could reduce loss in WUI wildfire disasters across Colorado's 27 million ha.

Context: WUI wildfire disasters are increasing, as fires are pushed by strong winds and drier fuels across landscapes and into communities. Possible disasters make maintaining and restoring landscape-scale fire in fire-adapted ecosystems difficult. Rapid action is needed to reduce building loss in WUI wildfire disasters. Objectives: In a Colorado study, I used distance-based empirical modeling to refine potential risk of building loss in WUI wildfire disasters to focus risk-reduction efforts. Methods: New empirical modeling showed 95% of USA building loss in WUI wildfire disasters was within 100 m of wildland vegetation. I used modeling to estimate and map potential relative risk of a WUI wildfire disaster for each of 2,185,953 buildings in Colorado. Results: High-risk buildings were 241,375 or 11% of total buildings. However, the 20–40 m essential defensible space around these buildings covered only 46,767–114,084 ha. Area within 100 m of wildland vegetation, containing these buildings, covered 475,840 ha or 1.8% of Colorado&#39;s 27 million ha. About 95% of at-risk land within 100 m of wildland vegetation is not federally owned, and WUI wildfire disasters are mostly from fires started on private land. Conclusions: Treating ≤ 114,084 ha of defensible space could leave the 27 million ha of Colorado with lower WUI wildfire disaster-risk to buildings. High risk of building loss is rarely a federal land-management problem. If the goal is rapid reduction of building loss in WUI wildfire disasters, focus resources on defensible space 20–40 m from WUI buildings within 100 m of wildland vegetation. [ABSTRACT FROM AUTHOR]