Here’s a long-read from Alejandra Borunda that’s running in National Geographic. Click through for the photographs and to read the whole article. Here’s an excerpt:
Overgrown forests and climate change are making record-breaking wildfires commonplace, but land managers can “treat” forests to change their behavior during burns.
California’s Caldor Fire ripped its way across the Tahoe Basin this week, forcing thousands to evacuate, burning homes and communities in its path, and staining Lake Tahoe’s iconic blue waters with falling ash.
The fire, like many others burning across the U.S. West this year, spread rapidly in part because it’s burning intensely, propelled by hot, dry, windy weather conditions and forests overpacked with trees—food for hungry fire.
But it has also run up against some areas that have been “treated” to reduce their fire risk, patches of forest—some big, some not so big—that have been trimmed in the past, either by hand with chainsaws and masticators or with carefully managed prescribed fire. These treatments are intended to make forests healthier and more resilient to all kinds of pressures, including fire.
In the fires burning across California this year, and in other major recent fires, experts say these treatments may have done their job—which is not to stop the fires but to lower their intensity enough that they can be controlled.
The treatments serve many purposes, but one crucial role is that “they’re meant to give firefighters an opportunity to defend life and property,” says Kelly Martin, the former chief of fire for Yosemite National Park. “Now what we’re seeing is, we have several hundred-thousand-acre fires bearing down on these communities—for what it’s worth, they’ve done their job.”
The megafire era
Fires in the West are getting bigger and more intense. 2020 saw the country’s first “gigafire,” a burn that spanned more than a million acres, much of which burned at high severity—the kind of fire that generally causes great harm to homes and ecosystems alike.
The reasons for these changes are many. Crucially, the weather conditions that spur fast-spreading and intensely burning wildfires are becoming more common as climate change heats up and dries out many parts of the West. The fire season overall is lengthening, starting earlier in summer and stretching later into fall, so long that it’s essentially fire season year-round, a captain in California’s firefighting service has said. Dry air is becoming even drier; summer rainfall is sparser; nights are staying warmer, keeping fires active through times that used to provide a window in which to fight them; and the winds that fan the flames are as strong as ever during summer and fall, the riskiest times in much of the region.
At the same time, the West is facing a “fuels” overload. The region’s landscapes used to burn frequently; estimates suggest at least four million acres of California used to burn annually from a combination of fires set intentionally by Native Americans and natural lightning ignitions. Native American fire practitioners say that many areas burned every few years or sometimes even more often. In the northern Sierra Nevada, where the Caldor and Dixie Fires burn now, lower elevation forests probably burned every five to 30 years or so. But from the early 1900s until the late 1970s, federal policy dictated that any and all fires should be suppressed thoroughly and quickly; the “10 a.m. rule”—that any new fire needed to be out by 10 the following day—guided the U.S. Forest Service until 1978…
“The average fuel load right now is probably something like 50 tons per acre. Under the old fire regime,” when Native people managed the land, “it was probably more like 7 tons per acre—an order of magnitude less than what it is now across large areas,” says Rob York, a forestry expert with the University of California, Berkeley.
Such fuel loads change the way fire behaves. Super-charged burns that get up into tree crowns can not only damage the trees but also help kick off embers that can fly miles ahead of the fire front, starting new blazes and driving quick expansion…
Fuels treatments aren’t a panacea. Super hot fires or wind-driven spread can overwhelm even a treated area. But treatments—either mechanical thinning or prescribed fire, or ideally a combination—can help drop flame lengths and the “fireline intensity,” measures of how intensely a fire burns. In turn, that can help slow the pace of fire spread.
While we can’t change the weather patterns or climate pressures, York says, at least not in the short term, we can control the fuels. It’s possible to thin out the region’s overloaded landscapes, using chainsaws, masticators, and other tools to thin trees and lower-level brush, and setting carefully managed, low-intensity “good fire.” Research suggests that in overgrown areas, using both strategies may improve outcomes.