The effects of fire severity and heterogeneity on post-fire occupancy of a terrestrial wildlife community in the Northwestern United States

Wildfire management must adjust to rapidly changing wildfire regimes by reducing the risk of large, high-severity wildfires, and understanding wildlife responses to post-disturbance environments is critical to effectively balance wildlife and wildfire management. The variation in responses to fire severity and heterogeneity across wildlife taxa and ecosystems underscores the need for region-specific knowledge that can guide fire management plans that integrate fire prevention and recovery. Therefore, we evaluated how fire severity and heterogeneity influenced wildlife occupancy across four recent (4–5 years old) mixed-severity wildfires in the Colville National Forest, Washington, USA. In the summers of 2019–2020, we distributed 207 cameras across four fire severities (unchanged, low, moderate, high). We used a spatial multi-species occupancy model to quantify the effect of fire severity at two spatial scales (landscape and local) and fire heterogeneity on species- and community-level occupancy and detection. Probability of occupancy declined with increasing fire severity at the landscape level both for the wildlife community and for most species groups, but we did not find any support for an effect of local wildfire severity. Additionally, fire heterogeneity did not influence probability of occupancy for the community and increased probability of occupancy for only two species. Recent increases in high-severity fires will likely reduce wildlife occupancy in our area up to five years post-fire. Fire severity plays a fundamental role in species- and community-level occupancy and must be considered in management regimes aimed at balancing wildlife habitat and wildfire risk, including fuels reduction treatments like mechanical thinning and prescribed burning. • Wildlife avoid areas characterized by high-severity wildfire 4–5 years post-fire. • Wildlife respond differently to fire severity measured at different scales. • Wildlife species may benefit from heterogeneous post-fire environments. • Multi-species occupancy models improve community-level understanding • Understanding fire impacts on wildlife requires a focus on severity