Smoke rises from a brush fire near Hollywood Hills in Los Angeles in 2007. 

9 07 2023
Smoke rises from a brush fire near Hollywood Hills in Los Angeles in 2007. Hector Mata/AFP via Getty Images
Over the past two decades, a staggering 21.8 million Americans found themselves living within 3 miles (5 kilometers) of a large wildfire. Most of those residents would have had to evacuate, and many would have been exposed to smoke and emotional trauma from the fire. By Mojtaba Sadegh, Associate Professor of Civil Engineering, Boise State University via The Conversation • Reposted: July 9, 2023

Over the past two decades, a staggering 21.8 million Americans found themselves living within 3 miles (5 kilometers) of a large wildfire. Most of those residents would have had to evacuate, and many would have been exposed to smoke and emotional trauma from the fire.

Nearly 600,000 of them were directly exposed to the fire, with their homes inside the wildfire perimeter. 

Those statistics reflect how the number of people directly exposed to wildfires more than doubled from 2000 to 2019, my team’s new research shows. 

But while commentators often blame the rising risk on homebuilders pushing deeper into the wildland areas, we found that the population growth in these high-risk areas explained only a small part of the increase in the number of people who were exposed to wildfires.

Those statistics reflect how the number of people directly exposed to wildfires more than doubled from 2000 to 2019, my team’s new research shows. 

But while commentators often blame the rising risk on homebuilders pushing deeper into the wildland areas, we found that the population growth in these high-risk areas explained only a small part of the increase in the number of people who were exposed to wildfires.

nstead, three-quarters of this trend was driven by intense fires growing out of control and encroaching on existing communities.

An aerial view of a community of small, closely built houses, with half the homes in the photo burned.
A wildfire in 2017 destroyed more than 3,000 homes in Santa Rosa, Calif., a city of over 180,000 people. Marcus Yam / Los Angeles Times via Getty Images

That knowledge has implications for how communities prepare to fight wildfires in the future, how they respond to population growth and whether policy changes such as increasing insurance premiums to reduce losses will be effective. It’s also a reminder of what’s at risk from human activities, such as fireworks on July 4, a day when wildfire ignitions spike. 

Two charts show wildfire counts by day of the year over 20 years. July 4 stands out as a clear spike, both looking at fires US-wide and just in the US West.
Mojtaba Sadegh, CC BY-ND

Where wildfire exposure was highest

I am a climate scientist who studies the wildfire-climate relationship and its socioenvironmental impacts. For the new study, colleagues and I analyzed the annual boundaries of more than 15,000 large wildfires across the Lower 48 states and annual population distribution data to estimate the number of people exposed to those fires.

Not every home within a wildfire boundary burns. If you picture wildfire photos taken from a plane, fires generally burn in patches rather than as a wall of flame, and pockets of homes survive.

We found that 80% of the human exposure to wildfires – involving people living within a wildfire boundary from 2000 to 2019 – was in Western states. 

California stood out in our analysis. More than 70% of Americans directly exposed to wildfires were in California, but only 15% of the area burned was there. 

https://datawrapper.dwcdn.net/K1mPs/2/

What climate change has to do with wildfires

Hot, dry weather pulls moisture from plants and soil, leaving dry fuel that can easily burn. On a windy day – such as California often sees during its hottest, driest months – a spark, for example from a power line, campfire or lightning, can start a wildfire that quickly spreads.

Recent research published in June 2023 shows that almost all of the increase in California’s burned area in recent decades has been due to anthropogenic climate change – meaning climate change caused by humans.

Our new research looked beyond just the area burned and asked: Where were people exposed to wildfires, and why?

A landscape view across a neighborhood with gold courses, lakes and hills in the background. In the foreground is burned cul de sac that appears to be at the edge of the city.
New homes on the edges of cities have been caught in some fires, like the one in Santa Rosa in 2017. But most of the people exposed were in neighborhoods existing well before 2000. George Rose/Getty Images

We found that while the population has grown in the wildland-urban interface, where houses intermingle with forests, shrublands or grasslands, that accounted for only about one-quarter of the increase in the number of humans directly exposed to wildfires across the Lower 48 states from 2000 to 2019.

Three-quarters of that 125% increase in exposure was due to fires’ increasingly encroaching on existing communities. The total burned area increased only 38%, but the locations of intense fires near towns and cities put lives at risk.

In California, which was in drought during much of that period, several wildfire catastrophes hit communities that had existed long before 2000. Almost all these catastrophes occurred during dry, hot, windy conditions that have become increasingly frequent because of climate change.

The 2018 fire that destroyed Paradise, Calif., began as a small vegetation fire that ignited new fires as the wind blew its embers. NIST

Wildfires in the high mountains in recent decades provide another way to look at the role that rising temperatures play in increasing fire activity.

High mountain forests have few cars, homes and power lines that could spark fires, and humans have historically done little to clear brush there or fight fires that could interfere with natural fire regimes. These regions were long considered too wet and cool to regularly burn. Yet my team’s past research showed fires have been burning there at unprecedented rates in recent years, mainly because of warming and drying trends in the Western U.S.

What can communities do to lower the risk?

Wildfire risk isn’t slowing. Studies have shown that even in conservative scenarios, the amount of area that burns in Western wildfires is projected to grow in the next few decades.

How much these fires grow and how intense they become depends largely on warming trends. Reducing emissions will help slow warming, but the risk is already high. Communities will have to both adapt to more wildfires and take steps to mitigate their impacts.

Developing community-level wildfire response plans, reducing human ignitions of wildfires and improving zoning and building codes can help prevent fires from becoming destructive. Building wildfire shelters in remote communities and ensuring resources are available to the most vulnerable people are also necessary to lessen the adverse societal impacts of wildfires.

To see the original post, follow this link: https://theconversation.com/human-exposure-to-wildfires-has-more-than-doubled-in-two-decades-who-is-at-risk-might-surprise-you-207903


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Western wildfires destroyed 246% more homes and buildings over the past decade – fire scientists explain what’s changing

5 02 2023

A fire burned in a national forest in southern New Mexico.Credit…USDA Forest Service, via Associated Press

By Philip Higuera, Professor of Fire Ecology, University of Montana; Jennifer Balch, Associate Professor of Geography and Director, Earth Lab, University of Colorado Boulder; Maxwell Cook,Ph.D. Student, Dept. of Geography, University of Colorado Boulder and Natasha Stavros, Director of the Earth Lab Analytics Hub, University of Colorado Boulder via The Conversation * Reposted: February 5, 2023

It can be tempting to think that the recent wildfire disasters in communities across the West were unlucky, one-off events, but evidence is accumulating that points to a trend.

In a new study, we found a 246% increase in the number of homes and structures destroyed by wildfires in the contiguous Western U.S. between the past two decades, 1999-2009 and 2010-2020.

This trend is strongly influenced by major fires in 2017, 2018 and 2020, including destructive fires in Paradise and Santa Rosa, California, and in Colorado, Oregon and Washington. In fact, in nearly every Western state, more homes and buildings were destroyed by wildfire over the past decade than the decade before, revealing increasing vulnerability to wildfire disasters.

What explains the increasing home and structure loss?

Surprisingly, it’s not just the trend of burning more area, or simply more homes being built where fires historically burned. While those trends play a role, increasing home and structure loss is outpacing both. 

Streets with burned cars and nothing left of homes but ash.
Entire neighborhoods were reduced to ash when a wildfire spread into Santa Rosa, California, in 2017.  Photo: Justin Sullivan/Getty Images

As fire scientists, we have spent decades studying the causes and impacts of wildfires, in both the recent and more distant past. It’s clear that the current wildfire crisis in the Western U.S. has human fingerprints all over it. In our view, now more than ever, humanity needs to understand its role.

Wildfires are becoming more destructive

From 1999 to 2009, an average of 1.3 structures were destroyed for every 4 square miles burned (1,000 hectares, or 10 square kilometers). This average more than doubled to 3.4 during the following decade, 2010-2020.

Nearly every Western state lost more structures for every square mile burned, with the exception of New Mexico and Arizona. 

Charts showing rising trend of loses from fires.
Adapted from Higuera, et al., PNAS Nexus 2023, CC BY

Humans increasingly cause destructive wildfires

Given the damage from the wildfires you hear about on the news, you may be surprised to learn that 88% of wildfires in the West over the past two decades destroyed zero structures. This is, in part, because the majority of area burned (65%) is still due to lightning-ignited wildfires, often in remote areas. 

But among wildfires that do burn homes or other structures, humans play a disproportionate role – 76% over the past two decades were started by unplanned human-related ignitions, including backyard burning, downed power lines and campfires. The area burned from human-related ignitions rose 51% between 1999-2009 and 2010-2020.

This is important because wildfires started by human activities or infrastructure have vastly different impacts and characteristics that can make them more destructive. 

Unplanned human ignitions typically occur near buildings and tend to burn in grasses that dry out easily and burn quickly. And people have built more homes and buildings in areas surrounded by flammable vegetation, with the number of structures up by 40% over the past two decades across the West, with every state contributing to the trend.

Human-caused wildfires also expand the fire season beyond the summer months when lightning is most common, and they are particularly destructive during late summer and fall when they overlap with periods of high winds. 

As a result, of all the wildfires that destroy structures in the West, human-caused events typically destroy over 10 times more structures for every square mile burned, compared to lighting-caused events.

Map showing where fires burned in 1999-2009 and 2010-2020, comparing lightning-sparked to human-ignition and the amount of structures burned from each. More structures were burned in human-started fires.
Adapted from Higuera, et al., PNAS Nexus 2023, CC BY

The December 2021 Marshall Fire that destroyed more than 1,000 homes and buildings in the suburbs near Boulder, Colorado, fit this pattern to a T. Powerful winds sent the fire racing through neighborhoods and vegetation that was unusually dry for late December. 

As human-caused climate change leaves vegetation more flammable later into each year, the consequences of accidental ignitions are magnified.

Putting out all fires isn’t the answer

This might make it easy to think that if we just put out all fires, we would be safer. Yet a focus on stopping wildfires at all costs is, in part, what got the West into its current predicament. Fire risks just accumulate for the future.

The amount of flammable vegetation has increased in many regions because of an absence of burning due to emphasizing fire suppression, preventing Indigenous fire stewardship and a fear of fire in any context, well exemplified by Smokey Bear. Putting out every fire quickly removes the positive, beneficial effects of fires in Western ecosystems, including clearing away hazardous fuels so future fires burn less intensely.

How to reduce risk of destructive wildfires

The good news is that people have the ability to affect change, now. Preventing wildfire disasters necessarily means minimizing unplanned human-related ignitions. And it requires more than Smokey Bear’s message that “only you can prevent forest fires.” Infrastructure, like downed power lines, has caused some of the deadliest wildfires in recent years. 

Reducing wildfire risks across communities, states and regions requires transformative changes beyond individual actions. We need innovative approaches and perspectives for how we build, provide power and manage lands, as well as mechanisms that ensure changes work across socioeconomic levels.

Dot chart showing how each state's area and buildings burned changed. Calfiornia, Oregon and the West overall had above average loss and above average burning. Colorado had above average loss and below average burning.
Adapted from Higuera, et al., PNAS Nexus 2023, CC BY

Actions to reduce risk will vary, since how people live and how wildfires burn vary widely across the West. 

States with large tracts of land with little development, like Idaho and Nevada, can accommodate widespread burning, largely from lighting ignition, with little structure loss. 

California and Colorado, for example, require different approaches and priorities. Growing communities can carefully plan if and how they build in flammable landscapes, support wildfire management for risks and benefits, and improve firefighting efforts when wildfires do threaten communities.

Climate change remains the elephant in the room. Left unaddressed, warmer, drier conditions will exacerbate challenges of living with wildfires. And yet we can’t wait. Addressing climate change can be paired with reducing risks immediately to live more safely in an increasingly flammable West.

To see the original post, follow this link: https://theconversation.com/western-wildfires-destroyed-246-more-homes-and-buildings-over-the-past-decade-fire-scientists-explain-whats-changing-197384


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