Climate change has exacerbated heat waves and droughts, fueling a surge in california's unusually large-scale and destructive fires, but climate isn't the only factor contributing to the surge, according to foreign media reports. More than a century of firefighting operations have resulted in the accumulation of too many dead trees, fallen leaves and dried shrubs in the forest. At the same time, California's growing population means that more people now live and work in fire-prone areas.
The consequences of all fires are significant, even when viewed from space. The false color image at the top of the page shows burn "scars" left by fires that have burned in recent years, including two of the largest events on record in California: the Auguste Compound Fire and the Dixie Fire. The image was taken by a medium-resolution imaging spectrometer (modis) on NASA's Terra satellite on Sept. 21, 2021.
"Over the past few years, most of the activity has been in two-thirds of California's northern forest areas," said John Abatzoglou, a climate scientist at the University of California Merced, "and many of these forests have accumulated large amounts of biomass as a result of a century of successful firefighting." Now the bill is coming due. ”
Before firefighters began to intervene and stop fires in the early 20th century, low-intensity fires were regularly ignited by lightning or tribal peoples of Northern California. These fires regularly burn along the surface and remove fallen leaves, shrubs and saplings, reducing the risk of severe fires.
Daniel Swain, a climatologist at the University of California, explains: "Low-intensity fires close to the surface don't cause much ecological damage and can even help forests thrive. However, for most of a century, we have followed a policy of complete fire extinguishing, with few prescribed fires. This leaves California with many unnatural dense and overgrown stands. ”
Too much "trapezoidal fuel" makes it easier for the flame to move upward along the trunk and turns what may be a low-intensity surface fire into a fire that spreads along the treetops. These "canopy" fires are the hottest, most intense, and most destructive type. "They burn so hot that they consume most of the biomass, essentially disinfecting the soil."" Unfortunately, the California Fire Department doesn't neatly list the most intense fires, but from anecdotally, severe fires seem to be on the rise. "
According to Jon Keeley, an ecologist at the U.S. Geological Survey, according to some estimates, the buildup of fuel is at least five times more than could have been possible in history. "When you consider that California has been in a severe drought since 2012 and has added about 100 million dead or dying trees to the fuel load, you can see why so many fires are so difficult to control," he said. ”
Natasha Stavros, a fire ecologist at the University of Colorado, said: "The intensity of these extreme fires, combined with frequency and proximity to people, is what worries me the most. Frequent and intense fires mean ecosystems may not have time to recover. In some areas, the ecosystems we know today may be very different from what our children know. ”
Another key factor in understanding the devastation of recent California fires is the expansion of the Badlands-Cities Interface (WUI). As California's population has grown in recent decades, more people have built homes and businesses in and around fire-prone wastelands. According to an analysis, the number of housing units in California's WUI has increased by one million, or 34 percent, over a two-decade period. More development on wasteland also means more power lines in fire-prone areas. Power lines and electrical equipment have sparked several incidents on the California Fire Department's list of the most devastating fires.
Keeley said the real fires in California are not a completely new phenomenon. His lab searched old newspaper archives and federal and state records and found massive fires in 1868, 1889, 1891, and 1909. Each one may be listed in the California Fire Department's top ten fires, but records begin in 1919. "But these fires didn't cause much damage to people because they were less intense, and because there were fewer people at the time, there was a lot less infrastructure around them," Keeley said.
He added: "In recent decades, the frequency of fires and the level of damage they cause have risen dramatically. Given fuel loads and wind capabilities, we now often build and live in places where destructive fires are more likely to occur. (Extreme winds make it difficult for buildings to be protected because embers can spread quickly and widely along the fire.) )
An example of this is the Tubbs fire, which raged in suburban Santa Rosa after it was ignited by a spark from an electric system in October 2017. Unusually strong winds caused the fire to rapidly push down Santa Rosa Hill, where it tore through several zoning recently built on former forest land. An early fire roughly burned down the same area in the 1960s, but only destroyed a few dozen buildings. The 2017 tubbs fire destroyed more than 5,000 buildings as a lot of new developments took place. In the aftermath of the recent fire, charred vegetation and damaged houses can be seen in the landsat image.
And how people build is also important. Stavros said: "The problem is not just that we are building on the wasteland. It's also that we don't always enforce adequate building codes to protect people and homes – for example, making sure gutters and vents have low-light guards; making sure wooden sheds and barns aren't built near houses, or making sure houses have enough air filters to filter out smoke. ”
"Population growth and expansion into the WUI is especially important in Southern California, where much of the landscape is shrubland (shrubs, grasses, and small trees). Almost all fires there are caused by people, not lightning. Keeley explains: "They are usually wind-driven events that propagate extremely quickly. In some cases, wind-driven fires spread regardless of what happens in terms of climate or forest management. ”
Keeley said the best way to fight wind-fired fires is to stop people from starting fires and retrofit infrastructure to reduce risk. This means laying wires, enforcing fire safety rules during bad weather, ensuring that homes have fire barriers and preventing embers, and preventing communities from being built in fire-prone areas.
In Northern California, many fire experts believe that the risk can be greatly reduced by adopting the right deforestation regime and regulating fires in wet weather. Keith Weber, a remote sensing ecologist at Idaho State University and lead investigator of NASA's Resilience Convergence Ecosystem Project, said: "We need more projects to start using fires as a tool to reduce the occurrence of mega and mega fires." The photo above shows the fire that was set in January 2021 as part of a regulated fire in Nevada's Humboldt-toiyabe National Forest. Fires like these can clear surface fuels that could make future fires more intense.
"The problem we're seeing is not just fuel accumulation, not just population growth, not just climate change," Keeley said. We are facing all three problems at the same time, and we will have to find a solution to all of them. ”
And, in the coming decades, it's not just California that will face this challenge. "There's really nothing unique about California," Weber warned. "The same story can be played almost anywhere else in the Western United States."