Higuera Philip E, Cook Maxwell C, Balch Jennifer K, Stavros E Natasha, Mahood Adam L, St Denis Lise A
Department of Ecosystem and Conservation Sciences, University of Montana, 32 Campus Drive, Missoula, MT 59812, USA.
Earth Lab, Cooperative Institute for Research in Environmental Sciences, University of Colorado Boulder, 4001 Discovery Drive, Suite S348, 611 UCB, Boulder, CO 80303, USA.
PNAS Nexus. 2023 Feb 1;2(3):pgad005. doi: 10.1093/pnasnexus/pgad005. eCollection 2023 Mar.
Structure loss is an acute, costly impact of the wildfire crisis in the western conterminous United States ("West"), motivating the need to understand recent trends and causes. We document a 246% rise in West-wide structure loss from wildfires between 1999-2009 and 2010-2020, driven strongly by events in 2017, 2018, and 2020. Increased structure loss was not due to increased area burned alone. Wildfires became significantly more destructive, with a 160% higher structure-loss rate (loss/kha burned) over the past decade. Structure loss was driven primarily by wildfires from unplanned human-related ignitions (e.g. backyard burning, power lines, etc.), which accounted for 76% of all structure loss and resulted in 10 times more structures destroyed per unit area burned compared with lightning-ignited fires. Annual structure loss was well explained by area burned from human-related ignitions, while decadal structure loss was explained by state-level structure abundance in flammable vegetation. Both predictors increased over recent decades and likely interacted with increased fuel aridity to drive structure-loss trends. While states are diverse in patterns and trends, nearly all experienced more burning from human-related ignitions and/or higher structure-loss rates, particularly California, Washington, and Oregon. Our findings highlight how fire regimes-characteristics of fire over space and time-are fundamentally social-ecological phenomena. By resolving the diversity of Western fire regimes, our work informs regionally appropriate mitigation and adaptation strategies. With millions of structures with high fire risk, reducing human-related ignitions and rethinking how we build are critical for preventing future wildfire disasters.
建筑物损失是美国西部本土（“西部”）野火危机造成的一种严重且代价高昂的影响，这促使人们有必要了解近期的趋势及成因。我们记录了1999 - 2009年至2010 - 2020年间美国西部因野火造成的建筑物损失增长了246%，这主要是由2017年、2018年和2020年的火灾事件推动的。建筑物损失增加并非仅仅因为燃烧面积的增加。野火变得更具破坏性，在过去十年中，建筑物损失率（损失/烧毁公顷数）高出160%。建筑物损失主要由与人类相关的意外点火引发的野火所致（例如后院焚烧、电线等），此类野火造成了所有建筑物损失的76%，并且每单位燃烧面积所摧毁的建筑物数量是雷击引发火灾的10倍。每年的建筑物损失可以很好地由与人类相关点火引发的燃烧面积来解释，而十年间的建筑物损失则由易燃植被中各州层面的建筑物数量来解释。近几十年来，这两个预测因素都有所增加，并且可能与燃料干旱加剧相互作用，从而推动了建筑物损失趋势。虽然各州在模式和趋势上存在差异，但几乎所有州都经历了更多与人类相关点火引发的火灾和/或更高的建筑物损失率，尤其是加利福尼亚州、华盛顿州和俄勒冈州。我们的研究结果凸显了火灾 regime（火灾在空间和时间上的特征）从根本上说是社会生态现象。通过解析西部火灾 regime 的多样性，我们的工作为因地制宜的减灾和适应策略提供了信息。鉴于数百万建筑物面临高火灾风险，减少与人类相关的点火行为以及重新思考我们的建设方式对于预防未来的野火灾难至关重要。
