Indigenous Land and Historical Wildfire Management

A recently-released chapter in the book Climatic and Ecological Change in the Americas, completed with contributions from NCEI and partner scientists, explored the “fire resilience” of dry conifer forests, specifically Southwest U.S. ponderosa pine forests, and how Indigenous land management practices over past millennia may have enhanced the fire resilience of these forests. Since time immemorial Native Americans have lived on and used southwestern forest lands, and their practices included the addition of fires to landscapes. But over the past 150 years, these practices have been largely eliminated through the removal of Indigenous peoples from their ancestral lands and the suppression of traditional practices, along with the settlement of Euro-Americans that brought livestock grazing, logging, and fire suppression. This prolonged period of lumber extraction and lack of burning changed the forest ecology and led to higher severity fires that have killed large areas of ponderosa pine dominated forest in recent decades.

In their chapter, the authors explored time periods over the last 2,000 years when fires may not have been as frequent as historical norms and whether Indigenous fire stewardship in specific areas might have maintained those forests’ resilience to fires when they returned. The answer could address if modern fire management could emulate or bring back cultural burning and whether that would lead to enhanced forest resilience to fire as the climate changes and the region gets warmer, drier, and more fire-prone.  

The areas of focus in this study were the Jemez Mountains in New Mexico and the Mogollon Rim in east-central Arizona. These locations were home to ancestors of the Pueblo and Western Apache peoples, among other Native American groups, and utilizing new insights into Indigenous cultural burning, the researchers could now begin to address the effects of those fire regimes on the forests. 

What is “fire resilience?”

Historically, frequent and low-intensity surface fires occurred throughout the Southwest U.S. ponderosa pine forests, and have contributed to the overall wildfire resilience of the forests. Fire resilience means that areas are less vulnerable to devastating wildfires that destroy ecosystems, lead to large-scale vegetation type changes, and threaten lives.

Frequent surface fires reduce and break up the continuity of fire fuels across landscapes. This keeps most fires relatively cool and small in size, which are easy to manage and can lessen the negative effects of fires we now experience on forests, communities, watersheds, and infrastructure. Frequent surface fires also clear many small and young trees in the forests and promote a more open forest in which fires tend to remain on the ground, instead of the far more destructive fires that move rapidly through tree canopies. Ponderosa pine and many dry conifer forest tree species can resist the impacts of fires that stay on the ground, but will be killed by fires through their canopies. Unlike many higher elevation tree species, such as lodgepole pine, ponderosa pines have trouble regenerating following high-severity fires because of the loss of the seed source from mature overstory trees.

Some clear shifts in the fire resilience of the ponderosa pine forests have occurred with Euro-American settlement and land use changes within the past 150 years. These have interrupted the process of recurrent fire that is key to the ecological health of most ponderosa pine and dry conifer forests of the western U.S. Across vast areas in recent decades, extensive high-severity crown fires have begun to convert the forests to other types of vegetation.

Climate-fire connection

Variation in climate over years and decades also helps to regulate the growth and abundance of fire fuels. In the Southwest, researchers have successfully reconstructed this variability going back 2,000 years and longer in some areas. It is common practice to compare fire histories from tree-ring fire scars and these climate reconstructions, but such analyses are often limited to the length of the fire scar record, roughly 300–400 years in most cases.

In this study, the researchers used a model of fire extent and frequency calibrated on the relationship between historical fires and drought (Roos and Swetnam 2012). The model extends back over two millennia and reveals time periods when fires may not have been so extensive or frequent because the climate was less suitable to that pattern. These multi-decadal time spans likely created areas where fuels could build up and young trees could grow, reducing the fire resilience in those areas when a large fire returned. Numerous high-severity fires occurred over the past two millennia, though the study also found it likely that even those past high-severity fires burned smaller areas than modern high-severity fires.

Impacts of Indigenous land use on fire resilience

A key example of the impact of Indigenous land use can be found in the eastern Mogollon Rim area, where multiple studies have found evidence of high-severity fires in the mid-1400s, but only in areas that were distant from areas of intensive Native American settlement and land use (Roos, Laluk, et al. 2023; Roos 2008).

Despite the climate being less suitable for widespread burning over annual to decadal time scales, Indigenous peoples could get fire on the ground during shorter weather windows not seen in the fire-climate model. These fires enhanced the forest resilience where they used them the most, often near village sites and in hunting grounds. In more distant areas the researchers found high severity fires had similar effects on the forests as modern fires, specifically leaving behind other forms of vegetation, such as grassland.

Other studies have noted that cultural burning can have an influence on fire-climate relationships, even in areas where Indigenous and lightning-dominated fires occur at similar rates (Bliege Bird et al. 2012; Roos, Guiterman, et al. 2022; Swetnam et al. 2016; Taylor et al. 2016). There is evidence that land areas used by Native Americans and subject to Indigenous fire management practices were more fire-resilient, even during climate periods that favored longer fire-free periods.

Informing modern fire management

The same type of dry pine forests featured in this study are widespread across North America, and many of them are in close proximity to homes, roads, and other human infrastructure. Fires have been absent and actively suppressed in many of these areas for many decades, even approaching a century or more, allowing large amounts of fuel to build up in these forests.

Although some forest management techniques today can help resilience, much can be learned from the Native American practices of land management in these forests. Lessons learned from cultural burning practices support the call for more prescribed burning and can ensure fires happen when and where they are needed to aid in fire resilience.