Do Standard Ignition Indicators Hold in Densely Settled Landscapes? Forest Edges, Trails and Roads in Human-Caused Wildfires of Gyeonggi-Do, Republic of Korea

The wildland–urban interface (WUI) and road accessibility are standard explanations of human-caused ignition but are rarely tested where forest and settlement intermix. We analyzed 1043 ignitions recorded in Gyeonggi-do, Republic of Korea, between January 2016 and February 2026. Because coordinates were displaced, each fire was represented by random points within its cadastral parcel, and a weighted case–control model estimated relative ignition intensity. The Radeloff housing-density threshold, applied to households, was exceeded across about three-quarters of the province. Road distance differed between ignitions and controls but, assuming uniform location within parcels, added little information beyond the forest edge and settlement. Among the landscape, access, and settlement variables, proximity to the forest edge had the strongest association. This association arose on non-forest burnable land adjoining forest rather than within forest, persisted when cases and controls were limited to land within 100 m of forest, and partly reflected parcels straddling the forest boundary. Trail proximity was associated with hiker-caused ignition but not detectably with debris burning, although the difference was not distinguishable among small parcels. These findings call for interpreting standard indicators alongside forest-edge land cover and ignition cause.