The West’s forever fire season

How climate change makes wildfire more likely to happen all year round.

On April 5, the Santa Fe National Forest put out two press releases. One announced that it would conduct the long-planned Las Dispensas prescribed burn west of Las Vegas, New Mexico, the following day, “if forecasted conditions stay in place.” The low-intensity burn was intended to reduce fuel buildup — and therefore lower the risk of a catastrophic wildfire --—  in the Gallinas Watershed, Las Vegas’s primary drinking water source. The other press release, from its “Wildfire Preparedness is Year-Round” campaign, urged residents to prepare homes and yards for fire, since wildfire season was “just around the corner.” 

That corner turned out to be a bit closer than anticipated.


On the morning of April 6, the weather conditions were favorable for burning, so, after a successful test burn, the fire crews got to work. But that afternoon, erratic winds kicked up unexpectedly, blowing embers from the intended burn into unintended places and igniting spot fires that could not be contained. The Hermits Peak Fire was officially declared a wildfire that same day and would soon merge with the Calf Canyon Fire — ignited later by still-smoldering slash piles the Forest Service had burned back in January — to become New Mexico’s largest fire on record. That the Hermits Peak Fire was sparked by a prescribed burn is clear. But the reasons it blew up so calamitously are a bit more complicated. More than a century of fire suppression and the long absence of Indigenous fire stewardship, which together increased the buildup of hazardous fuels, certainly contributed, as did the string of dry years the region has experienced. And then there was the Forest Service’s miscalculation that fire season was still “just around the corner.”

In fact, there is no end or beginning to fire season anymore. It’s year-round. And while neither the Hermits Peak Fire or the Black Fire in New Mexico, or Arizona’s Pipeline and Tunnel fires — all big blazes that burned across the West before summer even began — can be tied directly to climate change, this new forever fire season can. Warming temperatures can affect snowfall, cause snow to melt earlier, and increase atmospheric thirst, thereby drying out all the fuels that have built up over the last hundred years or more, making them that much more flammable — even during early spring. 

And had forest officials working the Hermits Peak Fire acknowledged the long-term effects of climate change, rather than thinking about the short-term weather forecasts, a Forest Service investigation of the Hermits Peak Fire noted, it “would have led ... to more favorable outcomes.” Policymakers, take note: Climate change is here, and it’s time to recognize it. 


The Cause

Fossil fuel burning has caused the atmospheric concentration of carbon dioxide to soar to more than 400 parts per million — about 1.5 times pre-industrial revolution levels. Carbon dioxide and other greenhouse gases trap heat, causing the planet’s temperature to rise.

“These higher evaporative demands mean that, for every drop of precipitation that falls, less water is likely to drain into streams, wetlands, and aquifers across the region. Soils and vegetation spend more time in drier conditions, increasing potential for forest fire, tree mortality, and tree regeneration failure.”

—Christine M. Albano et al., JHM,
 Recent Trends in Evaporative Demand, 2022.




This April, even as fires raged in New Mexico, the Desert Research Institute published a study that found climate change was increasing evaporative demand, or atmospheric thirst, causing more water to be sucked from the soil into the air via evaporation and transpiration from plants (and snow and reservoirs), leaving less water in the streams and soil. Crops in the Rio Grande Basin, for example, where some of New Mexico’s blazes burned this spring, need 8% to 15% more irrigation now than they did in 1980. 



The Connection

“Since the 1970s, human-caused increases in temperature and vapor pressure deficit have enhanced fuel aridity across Western continental U.S. forests, accounting for approximately over half of the observed increases in fuel aridity during this period. These anthropogenic increases in fuel aridity approximately doubled the Western U.S. forest fire area beyond that expected from natural climate variability alone during 1984–2015.” — John T. Abatzoglou and A. Park Williams, PNAS, 2016

The Effect

In the 1970s, the first fires of the year typically were reported in April or even May, with the last ones occurring before mid-October. By 2012, fire season had grown by at least a few weeks on either end, with starts as early as March and as late as November. Climate change continues to extend the season today: The Marshall Fire in Colorado destroyed 1,000 homes at the end of December 2021, and New Mexico’s two largest fires on record had together burned nearly 700,000 acres before this summer even began.


After the Big Burn, aka the Great Fire, charred 3 million acres in the Northwest in 1910, the U.S. Forest Service began suppressing wildfires as quickly as possible. For decades, this resulted in much smaller fires, but the “fire deficit” also allowed fuels to build up in the forests. Warmer temperatures caused by climate change dried out the fuels and made them even more flammable, ultimately leading to larger and larger fires. Most of the region’s biggest fires on record have burned in the last two decades, and the most mega of those mega-fires occurred between 2020 and 2022.

Number of acres that have burned in U.S. wildfires as of July 15 this year.

865,620 acres 
Size of the Lime Complex Fire, currently the largest of several wildfires burning in Alaska this summer, as of July 19.



Sources: “Gallinas-Las Dispensas Prescribed Fire Declared Wildfire Review,” by the U.S. Forest Service; Santa Fe National Forest; Desert Research Institute; “Increasing western US forest wildfire activity: sensitivity to changes in the timing of spring,” by A.L. Westerling; NOAA; EPA; National Interagency Fire Center; CalFire; “Impact of anthropogenic climate change on wildfire across western US forests,” by John T. Abatzoglou and A. Park Williams; A Multidataset Assessment of Climatic Drivers and Uncertainties of Recent Trends in Evaporative Demand across the Continental United States,” Christine M. Albano et al.
Infographic design by Luna Anna Archey

Jonathan Thompson is a contributing editor at High Country News. He is the author of Sagebrush Empire: How a Remote Utah County Became the Battlefront of American Public Lands.