Mammalian resilience to megafire in western U.S. woodland savannas

Abstract

Increasingly frequent megafires, wildfires that exceed the size and severity of historical fires, are dramatically altering landscapes and critical habitats across the world. Across the western U.S., megafires have become an almost annual occurrence, but the implications of these fires for the conservation of native wildlife remains relatively unknown. Woodland savannas are among the world’s most biodiverse ecosystems and provide important food and structural resources to a variety of wildlife, but they are threatened by megafires. Despite this, the great majority of fire impact studies have only been conducted in coniferous forests. Understanding the resistance and resilience in wildlife assemblages following these extreme perturbations can help inform future management interventions that limit biodiversity loss due to megafire. We assessed the resilience of a woodland savanna mammal community to the short-term impacts of megafire using a before-after-control comparison. Specifically, we utilized a 5-year camera trap data set (2016-2020) from the Hopland Research and Extension Center to examine the impacts of the 2018 Mendocino Complex Fire, California’s largest recorded wildfire at the time, on the distributions of 12 observed mammal species. We used single species occupancy models to quantify the effect of megafire on species’ space use and a multi-species occupancy model for robust estimates of fire’s impacts on species diversity across space and time. Megafire had a strong, negative effect on mammalian occupancy and activity directly following wildfire, but most species showed high resiliency and returned to were resilient and returned to activity and occupancy levels comparable to unburned sites by the end of the study period. Following fire, species richness was highest in burned areas which retained some canopy cover. Change in habitat use following wildfire varied by species: several species temporarily reduced their use of severely burned areas, while others became more active in those areas. Fire management that prevents large scale canopy loss is critical to providing refugia for vulnerable species immediately following fire in oak woodlands, and likely other mixed-forest landscapes.

Neotropical mammal responses to megafires in the Brazilian Pantanal

“…Only jaguars had the fire covariate of AB in the extinction parameter in their top model, despite negative trends in occupancy for many of the species post‐fire and relatively high extinction values. We attribute this to the limited number of post‐fire records for many species, and the entire area being affected by the high burn severity (an average of 70% of the AB for the buffer area considered each camera), thus reducing differentiation by site (Calhoun et al., 2023). Additionally, ΔNBR should be individually calibrated in each vegetation type because of the difference in their chlorophyll and density values (Kokaly et al., 2007; Miller & Quayle, 2015; Picotte & Robertson, 2011), but such measures do not exist for Brazil.…”

“…Mammal responses to fire vary depending on their habitat and resource requirements, their dispersal ability, and other trait‐based characteristics (Calhoun et al., 2023). Mammal communities in non‐fire‐adapted regions may lack sensory cues to detect and flee from fires.…”

Mammalian resistance to megafire in western U.S. woodland savannas

“…The species record table, species detection histories, camera operation log, taxonomic group information, camera station metadata, and novel code (Calhoun et al, 2023) are available from Dryad: https://doi.org/10.6078/D1W70R.…”