OOS 42-5 - Emerging conservation technologies reveal that pyrodiversity mediates short-term biodiversity losses caused by megafires

Changing fire regimes are rapidly and extensively reshaping dry forest ecosystems across the Western US. Understanding the implications of contemporary fire regimes for biodiversity is necessary both for the direct conservation of species and to make informed decisions about the costs and benefits of potential forest management actions. However, the hypothesis that atypically large, severe fires in the Sierra Nevada are influencing overall biodiversity – beyond just a few priority species – has proven difficult to test. We used an ecosystem-scale passive acoustic monitoring program to collect pre- and post-fire data inside and outside two Sierra Nevada megafires; we used the BirdNET algorithm to extract detection/non-detection data for >70 species of birds from the audio; we used a novel multispecies, false-positive, dynamic occupancy model to quantify the effects of fire on avian diversity. The 129,000 ha North Complex Fire (2020) and 390,000 ha Dixie Fire (2021) caused site extinction probabilities to increase significantly for 26 species and caused site colonization probabilities to increase significantly for eight species, leading to significant decrease in biodiversity. However, site extinction rates were mediated by the composition and configuration of high severity fire (“pyrodiversity”). Conservation of avian diversity in the Sierra Nevada and potentially other dry forest ecosystems will be improved by management that mitigates the occurrence of large, uniform patches of high-severity fire.