20 Years of Impact

The Age of Climate Change and Megafires

Around the turn of the 21st century, scientists and land managers became increasingly concerned about the significant increase in the number of acres within a forest fire burning at high severity, from an average of 20 percent in the mid-1980s to over 30 percent by 2010. This concern exploded into the public consciousness in 2013 when the Rim Fire burned 257,000 acres, nearly 40 percent at high severity, in and around Yosemite National Park. At the time, it was the largest fire in recorded history of the Sierra-Cascade and prompted publication of our 2014 report The State of the Sierra Nevada’s Forests.

The following year, the King Fire burned nearly 100,000 acres at 50 percent high severity. The 2017 Railroad Fire was the first to burn so hot as to wipe out entire stands of giant sequoia. Then the 2018 Camp Fire burned over 153,000 acres, killing 85 people and destroying more than 18,000, structures including 95 percent of the towns of Paradise and Concow. The age of Sierra Nevada megafires had arrived.

Over a similar time period, much of the southern Sierra was gripped by an unprecedented multi-year tree mortality event. Unnaturally dense stands of trees proved no match for the stress of competing for scarce water during a multi-year drought, leaving entire landscapes vulnerable to pine beetle outbreaks. As reported in our 2017 update to The State of the Sierra Nevada Forests, 83 million trees died in the Sierra Nevada from overgrown forests, bark beetles, and drought between 2014 and 2016. Previously green hillsides turned brown with dead pine trees.

Compounding Crises

In 2020, somehow, it got worse. An August lightning storm ignited fires across the state, leading to a record-breaking 2020 fire season in the Sierra-Cascade. More than 3,500 structures were lost in the North Complex Fire, the Creek Fire blackened vast landscapes, and thousands of mature giant sequoia were killed in the SQF Complex Fire.

The season doubled the previous record for acres burned (set in 2018) and the amount, and arrangement, of high-severity fire in 2020 was unlike anything the region had experienced in the past. Scientific literature describing historical fire regimes refers to high-severity burn "patches", relatively small areas within a mosaic of fire effects where nearly all vegetation is killed. In contrast, these megafires created large high-severity burn landscapes that contained small patches of other, less severe, fire effects.

That was followed by another record-setting fire year in 2021, when more than 1.5 million acres burned in the Sierra-Cascade. The Dixie Fire became the largest single (non-complex) fire in state history, burning 983,309 acres across five counties, which included a single, 290,000-acre, high-severity patch and the destruction of the historic town of Greenville. It was one of two fires, the other being the Caldor Fire that consumed the town of Grizzly Flats and burned more than 220,000 acres, to burn up and over the crest of the Sierra Nevada—the first time in recorded history. The Windy and KNP Complex fires struck in the southern Sierra Nevada, killing thousands more giant sequoia.

These fires burned during, and were influenced by, another extended, extreme drought. From 2020 to 2022, California experienced the driest three-year period on record, leaving reservoirs depleted and the Sierra-Cascade almost devoid of snowpack. Although the dramatic tree mortality event of 2012-2016 has not been replicated, rates of mortality continue to rise: aerial detection surveys show generally elevated non-wildfire mortality, with moderate to very severe mortality in the central and northern Sierra Nevada.

Elevated tree mortality is concerning in and of itself, but is also as a catalyst of high-severity fire: researchers found that high levels of tree mortality in the southern Sierra Nevada strongly correlated with high-severity fire in the 2020 Creek Fire.

Sierra-Cascade Communities Grapple with a new Normal

Naturally, these events carry consequences for the people who live and work in the Sierra-Cascade, reflecting the interdependencies of the natural and human communities of the region. Despite covering one quarter of the state’s land mass, the region is home to around 880,000 people, just over two percent of California’s population. Most residents rely on healthy forests and watersheds for their security, livelihoods, and recreation. Although socioeconomic data specific to Sierra-Cascade communities is limited, residents struggle with issues shared by other rural Californians, including housing costs disproportionate to local incomes, limited access to healthcare services, rural school closures, and limited broadband internet.

Vulnerable residents—including people with disabilities or chronic illness, unhoused people, Indigenous people and people of color, people with limited English proficiency, households without a car, housing- and energy-burdened households, people living in poverty, and the elderly and children—face disproportionate impacts from these circumstances. Many communities suffer from interacting stressors exacerbated by climate change, like extreme heat, excessive wildfire smoke, record-setting snowfall, and destructive landslides. These are just some examples of climate-related trends that regularly threaten communities in the region.

The COVID-19 pandemic further compounded ecological and socioeconomic stressors. Early in the pandemic, lockdowns grounded recreation-driven economies to a standstill. Then, as urbanites sought outdoor space and clean air as a respite from pandemic confinement, demand for recreation surged, raising questions about how to manage use while mitigating negative impacts.

In both 2020 and 2021, visitation was interrupted, and businesses suffered their own form of whiplash during public safety power shutoffs, suffocating wildfire smoke, and the unprecedented closure of national forests across the region (and state) due to extreme wildfire conditions. Meanwhile, some communities struggled to navigate an influx of higher-earning remote workers who contributed to a national trend of spiking housing costs.

A Time of Reckoning

The Sierra-Cascade region is facing tree mortality events and megafires more intense than anything in its recorded history. The threats from wildfire and climate driven stressors facing the area are accelerating at a scale, severity, and pace unimaginable even five years ago. We find ourselves at an inflection point in the most transformative period for the Sierra-Cascade since European settlement in the 1800s and the attempted genocide of California’s Indigenous population.