Spatial overlap of wildfire and biodiversity in California highlights gap in non‐conifer fire research and management

Abstract

Aim Global change has spurred the escalation of megafires in California over the last 20 years throughout a variety of ecosystems. Here, we examine the spatial distribution of California wildfires and megafires from the last two decades (2000–2020) in relation to ecosystem types and biodiversity metrics. We offer insights into the prevalence of fire across vegetation types and its potential implications for biodiversity, and for fire and land management. These results challenge the prevailing discourse that wildfire in California is chiefly an issue of forest management. Location California, United States of America. Methods We calculated burned area across vegetation types from 2000 to 2020 by integrating fire perimeter and land cover data and compared this to a content analysis of coverage of wildfires by media and scientific research across California. We then compared the distribution of fire perimeters across biodiversity metrics (richness and endemism) for five terrestrial taxonomic groups (birds, reptiles, plants, mammals and amphibians) and against the distribution of the wildland‐urban interface (WUI). Results Total burned area from 2000 to 2020 was highest in shrubland ecosystems (38%), followed by conifer (36%), hardwood (17%) and grasslands (9%). In aggregate, ecosystems other than conifer make up the majority (64%) of the area burned in wildfires over the last 20 years. Fires most likely to impact endemic species, overlap areas of high species richness or burn within the WUI occurred predominantly in non‐conifer ecosystems. Main Conclusions Fires outside of forests have burned biodiverse areas critical to endemic species, but recent research and management in fire ecology continues to focus disproportionately on forests. Non‐conifer forested areas in California represent an important gap in fire research and management. As fire regimes shift dramatically in the state, other ecosystem types must be part of the wider conversation on fire management and policies to better protect people and biodiversity.

The importance of habitat type and historical fire regimes in arthropod community response following large‐scale wildfires

“…Historical wildfire regimes in Southern California scrublands have been estimated to feature more frequent fire, but with small, patchy, and low‐intensity wildfires that contrast the more catastrophic fire occurring today (Keeley & Fotheringham, 2001; Moritz, 2003). Scrublands were the most frequently burned habitat type from 2000 to 2020 in California (Calhoun et al., 2022). Because early successional stages are more sensitive to perturbations, fire before robust recovery will alter the successional trajectory (Kröel‐Dulay et al., 2015).…”

“…While prescribed fire has been a regular part of management, the application of such management strategies in habitats with different fire regimes like scrubland will have consequential ecological effects (Calhoun et al., 2022). Fires are infrequent in some scrubland, with intervals between 325 and 450 years for low sagebrush (Baker, 2006).…”

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

“…Translating these potential benefits into management guidelines, however, requires more specific knowledge of what burn severities and burn patch sizes create the desired benefits for wildlife at the community scale without harming species resistance and resilience (Donaldson et al, 2019). These recommendations are plentiful for conifer ecosystems in California, but rarer in other fire‐prone ecosystems such as oak woodland landscapes (Calhoun et al, 2021). Future work that specifically examines how fire severity and size across a breadth of oak woodland wildfires impact wildlife will help steer guidelines for prescribed burning that best enhance wildlife habitat in these landscapes.…”

“…Changes in historic fire regimes may pose a greater threat to woodland savanna ecosystems and their wildlife communities relative to other ecosystem types worldwide (Calhoun et al, 2021; Kelly et al, 2020). Due to the key services and habitat they provide around the world (Eastburn et al, 2017; Veldman et al, 2015), it is essential that we prioritize developing effective fire management tools for woodland savannas to protect their long‐term ecological integrity against shifting fire regimes.…”

Spatial and temporal patterns of wildfire burn severity and biomass burning-induced emissions in California

“…The concept of megafires has not been formally defined but most frequently characterized by size. They have been classified by fire size larger than 10 000 ha (24 710 acres) (Jones et al 2016, Stevens et al 2017 and over 40 468 ha (100 000 acres) in more recent years (Weber and Yadav 2020, Jones and McDermott 2021, Calhoun et al 2022. We defined megafires as fire size over 40 468 ha here to capture the effects of the most extreme fires.…”