National Snag Hazard 2026 (Image Service)

Snags are a hazard to firefighters that has traditionally been managed at the field level through scouting, rapid assessment, and mitigation by avoidance or by elimination though felling. Widespread wildfires and insect/disease disturbances have resulted in an accumulation of snags across many forested landscapes, raising the risk of injury or death for firefighters and other forest workers. The National Snag Hazard Map (Riley et al. 2022) is intended to provide a landscape level view of current snag hazard to encourage awareness, assessment, and planning to mitigate snag-related risks. The National Snag Hazard Map is based on the estimated density and median height of snags greater than or equal to 7.9-in diameter at breast height and at least 10-ft tall. Snag density and median snag height are classified into hazard levels based on the logic that hazard increases with snag density and height (Dunn et al. 2019). Snag hazard is a landscape level decision support tool intended to help firefighters consider the magnitude and spatial distribution of snag hazard in their incident response strategy planning. Valid uses include identifying areas of higher snag hazard on the landscape that may require extra mitigation for safe operation, or that could be avoided to reduce risk to firefighters. The snag hazard map is not meant for tactical planning. A rating of low snag hazard does not mean that no overhead hazards are present and should not be interpreted as judgement that an area is safe to occupy. Conditions should always be verified in the field. Maintaining high situational awareness for overhead hazards is recommended regardless of the snag hazard rating. Dunn CJ, O’Connor CD, Reilly MJ, Calkin DE, Thompson MP (2019) Spatial and temporal assessment of responder exposure to snag hazards in post-fire environments. Forest Ecology and Management 441, 202-2014. DOI:10.1016/j.foreco.2019.03.035 Riley KL, O’Connor CD, Dunn CJ, Haas JR, Stratton RD, Gannon B (2022) A national map of snag hazard to reduce risk to wildland fire responders. Forests 13, 1160. DOI:10.3390/f13081160枯立木（snag）对消防员而言是一类危险源，传统上通过野外巡查、快速评估，并采取规避或伐除的方式进行防控。 大范围野火与病虫害扰动导致诸多森林景观中枯立木大量堆积，加大了消防员及其他林业从业人员的伤亡风险。 《国家枯立木危险地图》（National Snag Hazard Map，Riley等，2022）旨在从景观尺度呈现当前枯立木危险状况，以提升相关人员的风险认知、评估与规划能力，从而降低与枯立木相关的各类风险。 该地图基于胸径≥7.9英寸、高度≥10英尺的枯立木的估算密度与中位高度进行绘制。 枯立木密度与中位高度依据“危险程度随枯立木密度及高度升高而增加”的逻辑被划分为不同危险等级（Dunn等，2019）。 枯立木危险评估是一种景观尺度的决策支持工具，可辅助消防员在制定火情应对策略时，考量枯立木危险的规模与空间分布特征。 其合理应用场景包括：识别景观内枯立木危险等级较高的区域，此类区域或需额外开展防控以保障作业安全，或可通过绕行规避来降低消防员所面临的风险。 但该枯立木危险地图不可用于战术层面的规划。 枯立木危险等级为“低”的区域，并不意味着不存在高空危险源，也不应被解读为该区域可安全进驻的判定。 所有现场情况均需实地核验。 无论枯立木危险等级如何，均建议持续保持对高空危险源的高度态势感知。 Dunn CJ, O’Connor CD, Reilly MJ, Calkin DE, Thompson MP (2019) Spatial and temporal assessment of responder exposure to snag hazards in post-fire environments. Forest Ecology and Management 441, 202-2014. DOI:10.1016/j.foreco.2019.03.035 Riley KL, O’Connor CD, Dunn CJ, Haas JR, Stratton RD, Gannon B (2022) A national map of snag hazard to reduce risk to wildland fire responders. Forests 13, 1160. DOI:10.3390/f13081160