How to Save a Forest by Burning It

GEORGETOWN, Calif. — Waves of fire swept through the Sierra Nevada forest, kicking up smoke and leaving charred vegetation in its wake — all under the watchful eye of a high-powered drone. Instruments around the rim took samples of the scorched particles thrown into the air.

Mandatory burning, an age-old practice that rids forests of small trees, brushwood, and other materials that can fuel wildfires, gets a 21st-century upgrade.

As climate change dries the land and the risk of wildfires increases, scientists are beginning to use cutting-edge technology and computer modeling to make controlled, low-intensity burns safer, more effective, and less disruptive to surrounding communities.

“Fire made us civilized, but we still don’t fully understand it,” said Tirtha Banerjee of the University of California, Irvine, as he watched a large pile of dead branches burst into flames.

As useful as mandated burns can be for forest conservation, they are difficult to implement – ​​costly, labor intensive, dependent on narrow windows of favorable weather. And even well-planned fires can turn disastrous, like when a fire started by the United States Forest Service this spring was turned by gusty winds into New Mexico’s largest wildfire on record.

Scientists think we can do better. Several teams recently met at the Blodgett Forest Research Station northeast of Sacramento, an area teeming with towering ponderosa pines, Douglas firs, and incense cedars. A planned fire at Blodgett was a valuable opportunity to collect data on site, and researchers packed truckloads of equipment, including GoPro cameras, drone-mounted sensors to map the terrain in minute detail, a sonic anemometer to measure wind, and an assortment of machines to pick out the particles collected in the air.

While researchers have long used advanced techniques to study wildfire behavior, fewer have addressed issues specific to mandated fires, such as whether debris should be cleared up in advance with chainsaws and bulldozers, said Robert York, a forest ecologist at the University of California. Berkeley.

Preemptive dilution could allow more wind to flow through during a fire, creating hotter flames and making the fire harder to control. But it could also help the burn use up more of the remaining food, creating a longer-lasting buffer against barrel burns.

“For prescribed fire, I think there really is everything to explore,” said Dr. Banerjee.

When Prometheus stole fire from the gods and gave it to humans, he probably had no idea how difficult it would be to manage on a planet heated by burning fossil fuels.

Global warming has led to more extremely hot and dry conditions that can turn wildfires into deadly disasters. Flames as ferocious as last year’s Dixie Fire that burned nearly a million acres in northern California were not part of the picture for scientists half a century ago, when the Forest Service and other agencies developed their mathematical models to predict wildfire spread.

Scientists were “just amazed at how quickly things are changing,” said James T. Randerson, a geoscientist at the University of California, Irvine.

The forest service has acknowledged that its methods are not keeping pace with the planet’s warming. The agency’s investigation into the ill-fated New Mexico fire that spring found that the resulting fire, although properly planned, proved more dangerous and quicker than expected.

To teach land managers how to burn in increasingly volatile landscapes, J. Kevin Hiers, a fire scientist at the United States Geological Survey and Tall Timbers Research Station in Tallahassee, Fla., has spent years working with other researchers on fire’s equivalent of a flight simulator — a video game -like training system that would be “a Minecraft-like experience for burning bosses,” as Dr. Here’s it called.

Better fire modeling is important, but so is incorporating that knowledge into user-friendly tools for fire teams, he said. “We should be able to represent in a training environment, in a very sophisticated way, what fire should or could do long before we strike a match.”

The scientists who traveled to Blodgett Forest spent their first two days on site setting up equipment and carefully examining the landscape before it burst into flames – something that would have been impossible if they were trying to study wildfire .

dr Banerjee and his team of PhD students and postdocs repeatedly flew their drone over the area and mapped it using lidar, a technology for capturing detailed three-dimensional images; a thermal imaging camera; and a multispectral camera that told them how dry the brush was. By comparing images before, during and after the fire, Dr. Banerjee to determine exactly how the fire had changed the forest floor.

In the evening the team of Dr. Banerjee small piles of deadwood and shot GoPro videos of the flickering flames and embers being thrown into the air. The footage would help the team study how embers travel, which could reveal fires spreading out of control.

In another piece of forest, Dr. Randerson and Audrey Odwuor, a Ph.D. Candidate in Irvine, stuffing twigs and pine needles into Ziploc bags like collecting evidence from a crime scene. They planned to burn the material back in their lab to analyze the chemical makeup of the resulting emissions. They had also brought instruments to Blodgett to collect smoke samples. One day, Ms Odwuor said, such methods could help assess how effectively a prescribed fire has burned the fuels it was designed to get rid of.

dr York, who works at Blodgett most of the year, took the researchers through an area of ​​forest that he said hadn’t burned in three years. Burning now would help keep the property in a healthy, natural state, even if all the planning, coordination, and effort that went into it was anything but natural.

The morning of the fire was sunny and hot. The researchers donned flame-retardant shirts and hard hats, and Dr. York led the group to high ground as chief of the incineration. He lowered his driptorch and a thin stream of fuel dripped out, catching the flame on the flashlight’s wick. Rags of fire sprouted from the dead brown ground. The burning had started.

dr York and a small experienced team walked perpendicular to the slope of the forest and used their torches to draw lines of flame that burned uphill. The landscape changed quickly. The tall trees cast wispy, dramatic shadows across the off-white curtains of smoke. Dense haze diffused the sunlight and bathed the forest in a deep orange glow. The crackle of burning bushes mingled with the low mechanical howl of the drone overhead.

For a while the flames had a gentle, almost dainty quality; the vegetation was too damp to burn very fiercely. But as the day got warmer, fires began blackening the slopes at a rapid pace. The scientists carefully surveyed the scene while their machines collected data.

In the late afternoon, Dr. York and his team burned down about 13 acres and he sat down for a breather. His face was slippery with sweat and dirt. The forest smouldered around him.

dr Randerson took a moment to admire the brutal raw power of the fire they were studying – a natural but also unnatural way of protecting the land. “The older I get,” he said, “the more I appreciate how much science is like an art.”