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Native Americans managed wildfire risk with controlled burns for hundreds of years

Can "prescribed burns" prevent massive wildfires? A study of the Native American practice of starting small, contained blazes suggests it can.

(CN) — Wildfires have so regularly devastated the drought-stricken American West, they've become expected. It's wildfire season — it's just what happens. California's fire seasons even have their own wikipedia pages, as if they were Oscar ceremonies or seasons of Grey's Anatomy.

There has been much debate over whether California should be using more "prescribed burns," or controlled burns — that is, using "good fire" to prevent bad fire. It's a practice that's routinely used in Florida and other southeastern states, but is less common in the southwest. And it is known that Native Americans would routinely use prescribed burns, though the scale of these burns has been the subject of some debate.

A new study, published Wednesday in Science Advances, seeks to measure the scale of those burns, as well as to quantify their usefulness in preventing climate-induced wildfires.

"These were fires — some of them of them were tens of acres," said Christopher Roos, an environmental archaeologist and Professor of Anthropology at Southern Methodist University, and the lead author of the paper. "Some were up to a few hundred acres." Which is to say, they were fairly small fires. "Now when we do prescribed burns, they aim for thousands, tens of thousands of acres," said Roos.

The result: a sprawling patchwork of charred land that reduced the risk of large wildfires set off by droughts.

Roos and a team of researchers studied nearly 5,000 fire-scarred trees in Arizona in New Mexico, in areas inhabited by the Apache, Navajo and Jemez tribes over the course of 400 years, between roughly 1500 and 1900. A key part of their work involved looking the "tree ring record." Tree rings can not only tell you how old a tree is, but can also reveal if the year was especially wet or dry and when the tree was damaged by flames. The scientists obtained ancient tree-ring data from the International Multiproxy Paleofire Database, which was compiled by the North American Fire Network. They also looked at paleoclimate records and talked to members of the tribes as well.

“We found that during periods of intensive use [of controlled burns], most of the discrete stands of trees we looked at don’t have any significant fire-climate patterns,” Roos said. “So, in this case, the absence of significant climate patterns when Native Americans were managing fire is taken as strong evidence that Native American fire management itself is creating that lack of fire-climate patterns, since all other places and time periods show those significant climate associations.”

In other words: the good fires prevented bad fires.

"Even strong droughts didn't illicit a strong fire reaction, because the source of fuels was very fragmented," said Roos. "It shows that one of the goals of contemporary prescribed burning actually works. It worked for these communities for hundreds of years."

The tribes performed controlled burns for a variety of reasons, some economic — clearing the land of debris, for example, or herding animals into certain areas for hunting — and some were cultural or religious.

Chris Toya is a member of the Jemez Pueblo tribe in New Mexico, an archaeologist who serves as the tribe's Historic Preservation Officer. He worked with Roos on the study and was amazed to learn its findings, because they seemed to confirm a story of his village's founding that's been passed down for generations.

"When my ancestors came to this area, they had to clear the debris," said Toya. "That's the oral tradition we hear today. But we didn't really know what they were talking about. Until now. It's science and oral history coming together."

"Putting it all together paints a picture in color," he added. "You start to understand, hey man, this is what our ancestors were doing."

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