Managing fire for plants and animals
Western forests face an escalating crisis of larger and more severe wildfires, threatening communities, water supplies, and wildlife habitat. Managed wildfire—guiding naturally-ignited fires burning under predetermined conditions—offers a promising solution in remote areas by restoring fire's ecological role while building forest resilience to future megafires. Rocky Mountain Research Station scientists demonstrated that managed wildfire can be designed to maximize biodiversity by creating varied patterns of fire frequency, severity, and spatial arrangement across the landscape. Different species thrive under different fire characteristics—some benefit from frequent, low-severity burns while others need occasional high-severity patches—meaning that diverse fire patterns support the richest array of plants and animals.
A pyrodiverse landscape in the Sierra Nevada mountains created by multiple managed wildfires. The variable fire effects and timing supports habitat for species of plants and animals with different resource needs.
Forest Service scientists studied two wilderness areas in California's Sierra Nevada where lightning-caused fires have been managed for decades. These managed wildfires have created a landscape mosaic of different fire histories, from unburned patches to areas burned at various severities over different time periods.
These fire-restored landscapes support high levels of plant, bird, and bat species richness. Unexpectedly, biodiversity peaked under conditions with somewhat more frequent and moderately severe fires than was historically typical. This challenges the long-held assumption that returning forests to their historical state is always the best conservation strategy for biodiversity.
Fire-Adapted Plants and Animals
Different species groups thrive under different fire conditions. Bird richness peaked in recently burned areas with moderate severity, utilizing a mix of live trees, snags, and understory vegetation for nesting and foraging. Plants preferred recent, low-severity burns that reduced competition for resources. Bats favored complementary mature forests with longer intervals between and patches of severe burns. This diversity of preferences means that landscapes with varied fire patterns (aka "pyrodiversity") support the most species overall.
“Forest managers are often tasked with restoring low-severity fire regimes, which is becoming increasingly difficult. These findings provide some flexibility, showing that somewhat higher frequency and severity still supports plant and animal communities,” says lead author, Forest Service scientist Dr. Zack Steel. While managed wildfire isn't feasible everywhere, where it can be safely implemented, restoration of beneficial fire is a valuable tool for multi-resource management.
The Bigger Picture
These findings come from wilderness areas that have experienced a 50-year natural experiment, and which represent rare examples of active fire regimes in the west. “Western forests are increasingly becoming landscapes of extremes – characterized by overly dense fire-suppressed conditions or subjected to catastrophic megafires. Getting ‘good fire’ back on the landscape is helpful for both forest health and biodiversity,” says Dr. Steel.
The research reveals that managing exclusively for the frequent, low-severity fires that were historically common may not always optimize biodiversity. Instead, accepting patches of moderate and even limited high-severity fire within a diverse mosaic can enhance species richness. This "Goldilocks" approach to fire—not too little, not too much, but varied across the landscape—offers a blueprint for building resilient forests that can withstand future disturbances while supporting diverse plant and animal communities. This research supports expanding managed wildfire and prescribed burning, showing these tools achieve multiple objectives when guided by robust science.