Spreading Like Wildfire: Developing a wildfire directional vulnerability assessment for English forest managers

ABSTRACT
Background.  Driven by a warming climate and land–use changes, fire regimes are changing, with direct and indirect environmental, social and economic impacts.  The UK is increasingly vulnerable; despite policy guidance, forest managers prioritise more pressing issues.  Exposure mapping was traditionally omnidirectional; the directional vulnerability assessment maps potential wildfire trajectories and encroachment on communities.  Aim.  This study tests the transferability of the directional vulnerability assessment to England’s temperate deciduous context, focusing on the New Forest, and evaluates its effectiveness as a framework for strategic wildfire risk assessment for forest managers.  Methods.  Wildfire exposure was assessed using the UKCEH Land Cover Map and a vegetation hazard classification; exposure assessments were validated against 2014–2021 burned–area data.  An ArcGIS Pro trajectory delineation method and R validation script were developed for the directional vulnerability assessment; high–exposure and viable trajectory thresholds were defined.  Directional vulnerability assessments were run for community and environmental values; outputs with varying segment lengths were compared and a synthesis of radial graphs analysed.  Key results.  The wildfire exposure assessment was validated for short–range exposure but not long–range.  Resolution effects were small; 10 m was adopted for the community scale.  The high–exposure threshold was defined at ≥ 0.8 and 61% of viable trajectories overlapped high–exposure areas for 100% of their length.  The most informative segment length was 1 km.  Mapping radial graphs revealed informative intersecting trajectories.  Conclusions.  Vegetation fires burn preferentially in high–exposure areas, validating the exposure assessment.  The directional vulnerability assessment is customisable to the English context; a modified short–range assessment is informative at the community scale, with multiple intersecting radial graphs further supporting management decisions.  Implications.  The directional vulnerability assessment is straightforward, flexible, reproducible, and scalable with minimal data requirements.  It supports forest management planning and multiple stakeholders with various responsibilities.