Wildfires In The Inland Deserts Region
Guadalupe Sanchez, Ryan Sendejas, Francesca Hopkins
Greenhouse Gas Emissions Lab, University of California, Riverside
Hi, my name is Guadalupe Sanchez! I’m an undergraduate student at the University of California, Riverside, studying environmental sciences. My goal is to become an environmental scientist who focuses on protecting and supporting the needs of our natural and built systems. I’m especially interested in finding solutions that balance the health of the environment with the well-being of the people who depend on it. In the future, I hope to work on projects that address issues like climate change, community health, and actionable solutions. Above all, I want to make a lasting, positive impact on the natural environment and the communities connected to it.
Background
Climate change is increasing the number, size, and intensity of wildfires in California. Increasing trends have been observed in forests and grassland, but less is known about fires in desert ecosystems. We examined recent trends in fires in the Inland Deserts region to help understand how climate change might influence fires in the future. Fires pose a large risk to communities, so understanding changes to fires is critical to increasing community resilience under climate change.
Research Questions
Fire Cycles?
How have wildfire frequency and intensity, measured as burned area, changed in the Inland Deserts?
Where?
Where are wildfires burning with respect to population centers?
Climate and Wildfires?
How are wildfires correlated with temperature and precipitation?
Methods
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Number and fire perimeters for 1900-2024 are from the CalFire Fire and Resource and Assessment Program (FRAP) data
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Population data is from the US Census & ARCGIS Living Atlas
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Climate data is from NOAA's NClimGrid
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Vulnerable communities identified using CalEnviroScreen4.0 percentiles and risks
Results
Our findings show that there has been an overall increase in frequency and fire size (Figure 1 & 2) along with decreased precipitation and higher maximum temperatures (Figure 3 & 4).
Historical data
The largest wildfire during the 20th century was 58,790 acres (1944) versus in 2020, the largest wildfire was about 115,998 acres.
The highest number of fires a year in the 20th century occurred in 1980: 41 fires recorded.
Meanwhile, the highest recorded fires for the current century were 73.
1990-2024
There are five main peaks for this time period for wildfire count: 1995 (39), 2005 (56), 2011 (50), 2021 (39), and 2024 (73).
Fires and the
Wildland Urban Interface
The wildland–urban interface (WUI)—where homes and wildlands meet—is growing, putting more people and buildings next to flammable vegetation. This expansion increases human-caused ignitions and raises the risk of fast-moving fires and harmful smoke reaching neighborhoods.
Historic Fire Cycles
Both figures show generally modest activity through most of the 20th century, with notable historic anomalies: isolated large-acreage years in the 1920s–1940s and 1970s, and pronounced fire-count spikes around 1980 and the early 2000s.
In contrast, 2020–2024 forms an anomalous cluster of extremes, with record-high fire counts and several of the largest acreage years, indicating a recent shift toward more frequent and larger fires.
Historic Climate
Temperature averages were early on in the historic data, but since the late 1990s, they’ve elevated above average, with the hottest years in the 2010s–2020s. Rainfall oscillations change from wet years followed by dry ones, leading to increased fire load, and followed by hot and arid years, which give rise to a higher fire risk.
Discussion & Conclusion
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Fires are mostly occurring near populated areas, with implications for vulnerable communities such as elevated asthma risks. This may be due to a higher number of ignitions in the area, but also due to types of fuels present, including invasions of annual grasses and disruptions of native desert vegetation.
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The number and severity of fires is increasing with temperature. Higher temperatures dry out fuels earlier, expanding the fire season. Temperature increases fire risk through vapor pressure deficit; high vapor pressure deficit correlates with wildfire size and intensity because of high evaporation rates. It’s established that higher temperatures will increase the vapor pressure deficit, and dry out vegetation.
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High fires years occurred following a year that experienced heavy precipitation. Said precipitation aids in the growth of vegetation in the area, increasing fuel load and increasing wildfire size and occurrences. Many of the incidents with high precipitation happen after El Nino events.
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Further investigation is required to fully assess the increasing patterns of wildfires in this region regarding ecosystem shifts and urban expansion. Future projections for this region are crucial for planning efforts.
Acknowledgments
These findings will go into the Inland Deserts Regional Report for California’s Fifth Climate Change Assessment and guide planning where wildfire danger overlaps with vulnerable communities. The Fifth California Climate Assessment is supported by funding from the Governor’s Office of Land Use and Climate Innovation.
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