Uncontrolled wildfires, like the ones wreaking havoc in California, are dangerous and unwelcome. They destroy homes, worsen pollution and threaten the lives of both humans and animals. The narrative is different, though, for managed wildfire programs or large-scale prescribed burning efforts in forests that historically experienced frequent fire before human expansion. Wildfire is actually an important ecological process that influences biodiversity and habitat quality. In a new study, researchers found bats have responded positivity to the wildfires plaguing the Sierra Nevada Mountains, and suggest beneficial fire as a way to conserve bat populations and further manage their habitats.
Following a century of human-aided fire suppression, much of Sierra Nevada forests have experienced an absence of wildfire, and have become denser and more dominated by small trees. This is detrimental to many bat species who require uncluttered forests for foraging and large live and dead trees for roosting. In addition to this habitat loss, bat species—who are vital to the ecosystem and provide benefits to society—are threatened by climate change and diseases such as white-nose syndrome. White-nose syndrome has plagued bats since as early as 2006, but became prominent in the second decade of the 2000s, killing almost 7 million bats in that time. Fortunately, Zack Steel’s study, recently published in Scientific Reports, offers renewed hope for select bat species.
“In the short- to medium-term, this is somewhat of a good story in terms of climate change,” Steel, a postdoctoral student at UC Berkeley, told Laboratory Equipment. “In contrast to more fire-sensitive species, if wildfires continue to burn more severely, bats may be okay. That being said, other environmental shifts associated with climate change, such as increased frequency and severity of drought, may be a threat. In the short term, we are more concerned with threats such as the expansion of white-nose syndrome, which is just starting to appear in the west. Improving forest habitats for bats will help these species and populations weather white-nose syndrome and other treats associated with global change.”
Steel and colleagues used bat surveys conducted during the spring/summer seasons of 2014 to 2017 within three areas burned by large wildfires within the Sierra Nevada Mountains in California to assess species occupancy rates. Occupancy increased for 6 species (35 percent of the community), with only one species experiencing a decrease. According to the study, an average of 8 species were detected in unburned areas. In areas with moderate to high burn severity, the species count was calculated as high as 11.
Previous, unrelated studies have found that the number of species of Sierra Nevada birds also increases in areas with high burn severity; and plant community richness is also maximized in these forests. Of course, managed nor naturally occurring wildfires are good for all species. For example, lichen diversity has been found to be extremely sensitive to wildfire, with significant declines with increasing fire severity.
Steel says the key is to promote variation in fire history and patterns on the landscape, also known as "pyrodiversity". When there are unburned areas as well as high-severity patches within the same landscape, habitats exist for a range of species.
“Currently our forests mostly have a dearth of fire due to fire suppression and occasionally these fire-suppressed forests experience uncharacteristically large and severe fires with large patches of complete vegetative mortality. These "mega-fires" are a result of both this history of fire suppression with the associated densification of forests and fuel build-up, and a warming climate. If we can reintroduce fire, either through managed wildfire programs or large-scale prescribed burning efforts, we will simultaneously reduce the risk of mega-fires and increase pyrodiversity on the landscape,” Steel concluded.