Understanding Urban Wildfires

Director's Note

By Alan Barton

The wildfires that tore through neighborhoods around Los Angeles in January are yet another tragic reminder of the risks we live with in, what author Stephen Pyne calls the Pyrocene – the era of wildfires. From all of us at the NMFWRI, where wildfires are on our minds every day, our hearts go out to all who were affected by the Los Angeles fires.

For me, these fires truly hit home. Growing up on the west side of Los Angeles in the 1960s and 1970s, I witnessed occasional wildfires that would burn through the chaparral ecosystem in the coastal mountains above Malibu and the Pacific Palisades. These fires burned homes that people built up in the hills, in what today we would call the “wildland-urban interface (WUI),” places where people live and recreate in natural areas near cities. I remember how many conversations following these fires focused on whether people should be allowed to build in these wild areas. But back in those days, I don’t recall any conversations about the risk of these fires entering the urban areas and destroying entire neighborhoods. That seemed unlikely and people just couldn’t imagine something like that happening.

Fast forward 50 years. What has changed that led to fires moving quickly from open lands into densely populated areas and burning up entire neighborhoods, displacing families, businesses, schools, churches, and the lives many residents were accustomed to? The answer is complex; a full explanation draws on changes in population patterns, human behaviors, ecological conditions, and climate. The immediate effect is that wildfires that ignite today have the potential to burn hotter, stronger and faster than in the past. Years of suppressing wildfires in fire-prone ecosystems built up fuel loads that facilitate explosive, fast-moving wildfires.  Plus, drought and a warming climate that dry out vegetation, increasing its propensity to burn and reducing its ability to withstand a fire; stronger winds also contribute to dryer vegetation and move a fire quickly across a landscape. Humans have made themselves more vulnerable to fire as well, building neighborhoods on the edge of wildlands, and moving into or recreating in the WUI areas, thereby increasing the risk of a human-caused ignition.

Today, if a fire ignites in an open area near a city, under the right conditions it can burn intensely and quickly into a neighborhood, spreading from home to home. Cities have some natural defenses, for example, paved roads can serve as a firebreak; city fire departments often can respond more quickly than rural fire departments that rely on volunteer firefighters and may have to travel long distances to respond to a fire. However, urban areas adjacent to forests and open grasslands, including New Mexico’s largest cities like Albuquerque, Las Cruces, Santa Fe and Rio Rancho, can fall victim to a high-intensity and fast-moving wildfire, just as we’ve seen in other places around the West in recent years.

What can we do to reduce the risk of a fire burning through urban neighborhoods? A common recommendation given to homeowners in WUI areas is home hardening, ensuring that a home is resilient to a fire by avoiding combustible materials in home construction, including decks and roofs; screening vents and windows to prevent embers from entering; reducing easily flammable vegetation near the home; and eliminating or moving wooden patio furniture, wood piles, and other items that might easily catch fire. Homeowners in neighborhoods around the edges of cities can take these steps as well. What is much more important, though, is to treat the natural areas around the cities to reduce the likelihood that a wildfire will grow and pick up enough steam to burn through a vulnerable neighborhood.

In the past, it was fire itself that reduced the chance that an ignition would grow into a megafire. On landscapes around the West, fires burned frequently so that excessive fuel loads in forests never built up, and fires burned at a low intensity, rarely climbing into the crowns of trees and spreading more rapidly. Today, the goal of controlled burns is to mimic this natural process, and to reduce fuel loads and therefore fire risk in areas near human values. Understandably, controlled burns make residents in both urban and WUI areas nervous, due to the potential that a burn could escape and grow into a damaging wildfire – as happened with the 2022 Hermit’s Peak/Calf Canyon fires. Fire managers who work on controlled burns take many precautions to prevent this from happening, and as a result there is a low risk (less than 1%) that a controlled burn will grow into a large, destructive wildfire. Managers also aim to reduce the possibility of smoke blowing into populated areas. In sum, while an intentionally set burn seems risky, the greater risk is not carrying out a controlled burn and leaving conditions in wildlands near cities vulnerable to a large, fast-moving wildfire that could burn into the city.

 

The fires that I witnessed decades ago in the mountains above the Pacific Ocean never reached the intensity that we see with some fires today. They burned frequently enough that they kept the natural vegetation under control, and while they caused some damage, they did not burn into neighborhoods and cause the tragedies that we see today. In the Land of Enchantment, our large state with a relatively small population, we enjoy spectacular beauty in our abundant natural areas. And, we have seen our fair share of large, damaging fires that burned buildings in Los Alamos, Ruidoso, and elsewhere. A rare few, like the Hermit’s Peak-Calf Canyon Fire, started as prescribed burns, and these are tragic for those affected by these fires and for the state. However, fire is an integral part of nature in our state. And while it may seem counterintuitive, one of the best ways we have to avoid more tragedies is to burn more areas under carefully controlled conditions. Controlled burns will keep our forests healthy and functioning, and reduce the risk of more destructive urban wildfires.