After the ‘Black Summer’ fires: faunal responses to megafire depend on fire severity, proportional area burnt, and vegetation type

Climate change and human activities have disrupted historical fire regimes, leading to complex and far-reaching impacts on global ecosystems. Despite extensive research in fire ecology, studies exploring vertebrate responses to megafires, and to nuanced fire characteristics, remain limited. We collected camera trap data 3–27 months following Australia’s 2019–20 ‘Black Summer’ megafires from 30 burnt sites and 10 unburnt sites. Our data included 14 animal species/groups, encompassing mammalian predators, small and medium-sized mammals, large herbivores, and birds. We used generalised additive mixed models to assess the influence of time-since-the-fires, burn status, fire severity, proportional area burnt, and vegetation type on species' activity. Models that included fire variables were well-supported for all species. The proportional cover of low-moderate or high-extreme severity fire had substantial support for five species, particularly herbivores, which generally showed a preference for burnt sites but at differing fire severities. The proportional area burnt, disregarding severity, was well supported for four species. At highly burned sites, fox activity peaked shortly after the fires, while small to medium-sized mammal activity increased more gradually. Vegetation type strongly influenced the response of four species to fire; in particular, wet forest birds preferred unburnt areas. Policy implications. We document variable short- to medium-term responses of a range of species to fire which could help guide management interventions. We demonstrate that animal species’ responses to fire are diverse and better captured using broader landscape-scale fire variables. We found that species were strongly influenced by proportional area burnt, fire severity, and vegetation type. Introduced foxes were attracted to recently burnt areas, so timely predator control may benefit vulnerable prey species. Wet forest species were sensitive to fires and could benefit from preservation and restoration of these habitats. Some species exploited low-moderate severity burnt areas, while others preferred high-severity burns. This suggests that species will face diverse challenges and opportunities in future extreme fire events. We emphasise the importance of using multi-faceted approaches to account for the complex responses of co-occurring species to fire events.

气候变化与人类活动已打破了历史火灾制度，对全球生态系统造成复杂且影响深远的后果。尽管火生态学领域已开展大量研究，但针对脊椎动物对巨型野火（megafire）及精细化火灾特征响应的相关研究仍较为匮乏。本研究于澳大利亚2019-2020年“黑色夏季”巨型野火发生后的3至27个月内，在30个过火样地与10个未过火样地采集了红外触发相机（camera trap）监测数据。本次采集的数据涵盖14个动物类群/物种，包含哺乳类捕食者、中小型哺乳类、大型植食动物与鸟类。本研究采用广义加性混合模型（generalised additive mixed models），评估了火灾后时长、过火状态、火灾烈度（fire severity）、过火面积占比及植被类型对物种活动的影响。纳入火灾相关变量的模型对所有物种均表现出良好的拟合优度与支持性。低-中度或高-极高烈度火灾的覆盖占比对5个物种具有显著的模型支持度，其中植食动物类群普遍偏好过火样地，但对火灾烈度的偏好存在差异。不考虑烈度的过火总面积占比对4个物种具有良好的模型支持度。在重度过火样地中，狐的活动强度在火灾后短期内达到峰值，而中小型哺乳类的活动强度则呈现更为平缓的上升趋势。植被类型对4个物种的火灾响应具有显著影响；其中，湿润林鸟类普遍偏好未过火区域。

政策启示：本研究记录了多类物种对火灾的多样化中短期响应，该结果可为管理干预措施提供重要指导依据。研究表明，动物物种对火灾的响应具有多样性，采用更大尺度的景观火灾变量可更全面地捕捉该类响应特征。本研究发现，物种活动显著受过火面积占比、火灾烈度及植被类型的影响。外来入侵狐会被新近过火区域吸引，因此及时开展捕食者防控或可帮助受胁猎物种群。湿润林物种对火灾较为敏感，对其栖息地的保护与修复将有助于这类物种的存续。部分物种会利用低-中度烈度的过火区域，而另一些物种则偏好高烈度过火区域。这表明在未来的极端火灾事件中，不同物种将面临多样化的挑战与机遇。本研究强调，需采用多维度研究方法以解析共存物种对火灾事件的复杂响应机制。