Megafire and megafauna: How ecological disturbances impact wildlife resilience to climate change

This story is from The Quadrat, a biannual newsletter published by the UC Berkeley Natural Reserve System. The Quadrat features undergraduate writing and reporting on work conducted at the seven UC Nature reserves managed by UC Berkeley.

I met Kendall Calhoun on a particularly cold day on the western slopes of the Diablo Range in California. My team and I had arrived at Blue Oak Ranch Reserve—one of Calhoun’s research field sites—and we were getting our equipment ready: microphone, notebook, tripod, camera…check, check, check, check. The plan was to visit a few spots on the reserve where Calhoun had set up some wildlife monitoring equipment. Our car, lovingly named Keanu (after the actor), had trouble navigating the reserve’s steep and rocky terrain, so we piled into Calhoun’s (nameless) four-wheel drive. 

I was nervous. This was the first time I would be interviewing a research scientist, and I did not know what to expect. Here was a researcher who had spent years dedicating himself to scientific pursuits, and here I was, just in my third year in college.  

“One, two, three–,” the Bluetooth car stereo murmured. Calhoun reached towards the stereo to change the channel, putting on an ambiguous radio tune. 

“Was that the new Beyoncé album?” I asked. We had been blasting the newly released Cowboy Carter on repeat during our drive to the reserve. I immediately recognized the four-count intro to the song “Bodyguard”, one of my favorites. 

“Yes, I recently started listening to it,” Calhoun replied. “Should I put it on as we drive?”

“I would love that!” I answered, emphatically. As we launched into a discussion of our favorite tracks on the album, my previous anxieties were suddenly calmed: our shared love for Beyoncé had bridged the gap between our identities. I was reminded of the fact that researchers are people, too, with interests beyond their scientific pursuits. We hit the unpaved road with me riding shotgun and a smile on my face. 

As we drove through Blue Oak, I gazed out across the terrain. If you look closely enough, the echoes of a massive wildfire peek through that sprawling green landscape. Not long ago, Blue Oak was charred and battered by the 2020 Santa Clara Unit (SCU) Lightning Complex Fire (Stephens, 2020), which sprawled across multiple northern California counties, including Santa Clara, San Joaquin, Alameda, Contra Costa, and Stanislaus. The SCU complex quickly escalated into one of the largest and most destructive wildfire events in the state’s recent history, encompassing over 396,000 acres of land (CAL FIRE). Like many recent wildfires in California, its ferocity consumed everything in its path, reducing houses to ash and shattering livelihoods. 

Thousands of people faced evacuations, injuries, and the daunting task of rebuilding their homes. However, most news coverage of the impacts of this fire largely ignored the fact that other kinds of homes were also destroyed. Across the state, wild animals often bear the brunt of ecological crises like wildfire. And their habitats take much longer to recover.

Remnants of the impacts of the SCU complex are obvious with a closer look, and Calhoun patiently pointed out these signs on the landscape, from scars on trees to burnt wood pieces on the ground. Calhoun’s research aims to address the gap in our knowledge of how ecological disturbances influence wildlife community assemblages in habitats across California. He notes that the consequences of anthropogenic change on the frequency and intensity of wildfires have the potential to drastically alter the dynamics of human-wildlife conflict.

Like the subjects he studies, Calhoun is from California. He grew up in Tracy, a city in the Central Valley, and was always interested in wildlife. For many kids of his generation, if you liked animals and wanted a job working with them, you were told to become a zookeeper or a veterinarian. He didn’t really know there were other career paths that would allow him to explore these interests. This quickly changed when he attended UC Berkeley as an undergraduate. It was at college that he was able to explore his childhood interests in wildlife biology. Through classes in the College of Natural Resources and the Department of Integrative Biology, he was able to do fieldwork and research, providing him with a myriad of opportunities to learn about natural history and ecology. In addition to his coursework, the Biology Scholars Program was absolutely critical to launching his career as a wildlife biologist. This initiative opened the doors to a field of study that has historically had limited participation by people of color and other minorities. It was through this program that he could finally see a future for himself as a researcher. 

Calhoun graduated with a degree in Molecular Environmental Biology in 2015 and went on to pursue graduate studies at UC Berkeley in the Department of Environmental Science, Policy, and Management, working with Professor Justin Brashares. For his PhD dissertation research, Calhoun examined the impact of recent megafires on oak woodland habitats and the resilience of native Californian mammal and bird populations (Calhoun et al., 2023). His work on the reserves was partially supported by the Carol Baird Student Award for Field Research.

As a postdoctoral scholar jointly based at UC Davis and UC Los Angeles, Calhoun is planning to develop management plans for various fire scenarios. He aims to identify how we can use prescribed burns to promote healthy ecosystems and wildlife populations. This work requires him to consider how global change factors like rainfall and drought patterns might influence how wild animals are interacting with people in the long term.

To this end, Calhoun is examining the effects of different types of fire across several protected areas. His study will tease apart how certain fire characteristics influence the behavioral responses of different species of mammals, including black-tailed deer (scientific name: Odocoileus hemionus columbianus), wild boars (Sus scrofa), mountain lions (Puma concolor), bobcats (Lynx rufus), coyotes (Canis latrans), gray foxes (Urocyon cinereoargenteus), western gray squirrels (Sciurus griseus), California ground squirrels (Otospermophilus beecheyi), and black-tailed jackrabbits (Lepus californicus). He is now working across four field sites managed by the University of California, which include three Natural Reserves (Blue Oak Ranch Reserve, Hastings Natural History Reserve, Quail Ridge Reserve) and one Agricultural and Natural Resources (ANR) site (Hopland Research & Extension Center). These sites have all burned within the last 5 to 10 years and will serve as natural experimental replicates in his study.

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With the help of a handheld GPS device, Calhoun is able to navigate the landscape with ease. After a short 20-minute drive, we arrived at one of his study sites on the reserve, which was directly within the fire scar of the SCU Complex. To monitor large mammal biodiversity, Calhoun has set up several camera traps across Blue Oak in both experimental areas that had previously burned as well as control areas that were unburned. Calhoun usually sets up his cameras in areas with high animal traffic, often near roadways. These motion-triggered infrared cameras allow him to take photos of animals in the wild without disturbing them. This data can be used to determine species richness, habitat usage, and animal activity patterns.

These devices are secured on trees, at approximately hip height, with screws and a lock, not because of the threat of human theft but rather the mortal enemies of camera trapping: wild pigs and tall grass. Camera traps are not a fool-proof method for wildlife monitoring. If not properly secured, curious animals can easily knock them down. Another challenge is due to the very nature of motion detection: tall grass will bend easily with the wind and trigger the sensors. Although new software like Wildlife Insights can be used to discard “empty” camera trap images (i.e., without any animals), Calhoun and his team still have to comb through thousands of photos. To reduce this risk, Calhoun uses a thin blade to trim any overgrown foliage in front of the camera’s line of sight. 

In addition to using camera traps to monitor mammal activity, Calhoun utilizes acoustic monitoring devices to record bird songs and calls. He places small devices called  AudioMoths near the camera traps, securing them firmly to the branches of trees. The devices are programmed to record only in the early morning hours to capture the dawn chorus, the collective cacophony of birdsong that commences at the start of the day. This leads to hours of recordings that Calhoun and his team of undergraduate interns will have to sort through, and these birds are no Beyoncé! Analyzing this kind of acoustic data can be long and arduous. Fortunately, new technology and deep learning AI tools such as BirdNET are rapidly being developed to help classify the calls and songs of different bird species. This means that researchers may no longer have to manually sift through recordings for hours on end.

Though his postdoctoral research project is still ongoing, Calhoun plans to use multiple years of data previously collected during his PhD dissertation to understand the long-term effects of fire in oak woodland habitats. This is important because much of the existing research has examined wildlife diversity in burned conifer habitats, which is what people typically imagine when they think of a forest fire. This perspective provides a much more nuanced story of the impact of megafire on wildlife.

There is no future without fire in California. We need to learn how to adapt and coexist with wildlife in this new shared reality. Calhoun hopes that his work will help inform management decisions to create more resilient ecosystems. “It’s really important to me to do research that’s relevant to California because I grew up here, and I care about the biodiversity of our incredible state. That’s really near and dear to me, and I think that’s why I do what I do and why I think investigating how fire and drought are influencing these wildlife communities is important for the future of conservation.” As Calhoun packs up his field backpack, I look out across the hills, hoping for a glimpse of coyote or bobcat. The city of San Jose glimmers in the distance. I know Calhoun’s work here today will have a meaningful impact on both the human and non-human residents near Blue Oak.

References
CAL FIRE. Santa Clara Unit. (2020, October 21). SCU Lightning Complex. The California Department of Forestry and Fire Protection. https://www.fire.ca.gov/incidents/2020/8/16/scu-lightning-complex

Calhoun, K. L., Goldstein, B. R., Gaynor, K. M., McInturff, A., Solorio, L., & Brashares, J. S. (2023). Mammalian resilience to megafire in western US woodland savannas. Ecosphere, 14(7). https://doi.org/10.1002/ecs2.4613

Stephens, T. (2020) Wildfire expands Blue Oak Ranch hydrology study. UC Nature Newsletter. November 5, 2020. https://ucnature.org/wildfire-expands-hydrology-study-at-blue-oak-ranch/