By Stephen E. Nash

Currently, the American West is engulfed in over 100 significant wildfires, many of which are unprecedented in scale and intensity. Some blazes, including one in Colorado, have been so severe that they have generated their own storms.

Research indicates that wildfires have become increasingly destructive in recent decades. This raises the question: Is this escalation due to climate change, human encroachment on previously untouched forests, or ironically, the federal policies aimed at wildfire suppression?

Forest fire management in the U.S. has its origins in the 1880s, shortly after the establishment of Yellowstone National Park in 1872. Following a period of allowing some wildfires to burn, the U.S. Forest Service implemented the “10 a.m. policy” in 1935, which mandated that all fires be extinguished by the following morning. To engage the public in these suppression efforts, the iconic Smokey Bear was introduced in 1944, promoting the message that “Only YOU can prevent forest fires!” However, this premise is based on the flawed notion that all forest fires are detrimental to both people and the environment.

This view contrasts sharply with the Traditional Ecological Knowledge held by many Native American tribes, who have historically utilized fire as a critical component of land management. In recent years, even the U.S. Forest Service has begun to recognize this understanding, advocating for prescribed burns to restore forest health.

Recent archaeological research in New Mexico supports this perspective, indicating that forests in the American West are severely out of ecological balance, partially due to federal fire suppression policies. How have these archaeologists gathered compelling evidence for this assertion?

The investigation starts at Wabakwa, an archaeological site in northern New Mexico, dating from around A.D. 1140 to A.D. 1470. This site was a large village with 800 to 1,000 rooms, situated on a ridge within a fire-prone ponderosa pine forest in the Jemez Mountains. The Ancestral Puebloans who inhabited Wabakwa cultivated maize and other crops and engaged in hunting and gathering. Their descendants now reside in communities such as Walatowa (Pueblo of Jemez) in northern New Mexico.

For archaeologist and “human pyrogeographer” Christopher Roos, Wabakwa offered an excellent opportunity to examine the unintended effects of fire suppression policies. Roos investigates ancient fire regimes—the historical patterns and occurrences of fires in a given area—to understand the role that Native Americans have played in forest management over time. In a recent study, Roos and his colleagues analyzed how varying fire management strategies have influenced the health of the forest ecosystem at Wabakwa over the past nine centuries.

Employing dendrochronology, or tree-ring dating, the team studied fire-scarred trees around Wabakwa and identified three distinct fire patterns. From approximately A.D. 1100 to A.D. 1650, small, sporadic fires were common, likely set by the village’s inhabitants to manage plant resources and optimize agricultural output.

Once the Native Americans vacated the area, these small fires ceased, allowing natural processes to take over. From the late 1600s to about 1880, fire scars indicated widespread, low-intensity wildfires impacting larger numbers of ponderosa pines—a pattern consistent with other North American forests, where wildfires typically occur every 15 to 20 years.

From the late 19th century onward, coinciding with the advent of federal fire suppression and intensified livestock grazing and logging (primarily by Euro-Americans), significant alterations to the forest structure were observed. The absence of low-intensity fires led to denser, overgrown forests, with many new trees sprouting since the last recorded wildfire in 1893. The amount of combustible materials, or “fuel load,” also increased considerably due to this lack of fire.

In 2012, after 119 years of fire suppression in the Jemez Mountains, the U.S. Forest Service allowed a fire to traverse Wabakwa once more. This prescribed burn, part of the Jemez Mountain Restoration Project, aimed to reduce the excessive fuel loads accumulated since the 1890s.

With various fire management practices evident at this site, Roos and his team had an ideal setting to test their hypothesis. They employed a groundbreaking technique for dating pottery sherds: optically stimulated luminescence (OSL) dating. This method, while complex, is fascinating.

OSL dating relies on pottery and similar objects containing specific sediments. The quartz grains in these sediments retain a record of their last exposure to intense heat or light. When subjected to ionizing radiation, stray electrons become trapped in flaws within the quartz crystals. These electrons accumulate over time until a burst of light or heat releases them, resetting the crystal's internal clock.

Using OSL dating, researchers provide a resetting energy through light exposure under controlled conditions. When the light is applied, trapped electrons are released, emitting luminescence that scientists measure to determine the duration since the quartz crystal was last reset.

Typically, this technique is used to ascertain when pottery was created, as the quartz clock resets when clay is fired at high temperatures. However, Roos and his team applied this method to ascertain when the last intense fire in the Wabakwa area occurred, which could indicate the impact of modern fire suppression practices on wildfire behavior.

The team collected 32 pottery sherds from Wabakwa. About one-third had experienced intense heat during the 2012 burn, another third had been subjected to historical wildfires but missed the recent burn, and the final third had remained buried and untouched since their creation.

After submitting these samples for OSL dating, results confirmed that the quartz clocks of the sherds exposed to the 2012 fire had indeed been reset. In contrast, those that had undergone previous wildfires without being burned in 2012 did not show a reset, nor did those that remained buried.

Thus, the 2012 prescribed burn was more intense than any fire in the region over the past 900 years, likely a consequence of federal fire suppression policies leading to excessive fuel buildup.

Reflecting on a TV commercial from 1970, I recall a slow-motion match igniting, followed by a stern reminder that “Matches don’t start forest fires. People do.” The message was clear: it was up to individuals like me to safeguard the forests.

At that young age, I lacked an understanding of irony and unintended consequences. Now, it is evident that over a century of fire suppression in the American West has created a precarious ecological imbalance. The work by the archaeologists at Wabakwa provides compelling evidence that once well-managed ponderosa pine forests have become dangerously flammable.

Addressing this issue will be challenging. However, collaborative efforts among federal agencies, universities, and Native American tribes indicate that a return to Indigenous fire management practices could effectively alleviate our current predicament. I hope we are not too late.

Stephen E. Nash is a historian of science and archaeologist at the Denver Museum of Nature & Science, author of several books, including Stories in Stone: The Enchanted Gem-Carving Sculptures of Vasily Konovalenko and An Anthropologist’s Arrival: A Memoir. He resides in Denver with his wife and three sons. Follow him on Twitter @nash_dr.

Originally published at www.sapiens.org on September 9, 2020.