Climate Matters•September 4, 2024
Wildfire Risk to Homes, Roads, and Power Lines
KEY CONCEPTS
Human-caused climate change is increasing the frequency and intensity of wildfires — putting U.S. homes, roads, power lines, and other critical infrastructure at risk.
One-third of U.S. homes are in counties with high wildfire risk, according to the U.S. Forest Service.
Research estimates that more than 265,000 miles of U.S. roads and power lines were exposed to large wildfires between 2000 to 2019.
Children are especially vulnerable to the harmful health impacts of wildfire smoke.
Climate Central’s fact sheet, Climate Change & Children’s Health: Air Quality, details how climate change worsens air quality and impacts children’s health and well-being.
Hotter, drier weather amplifies wildfire risk
Fire weather — the hot, dry, windy conditions that prime the landscape for more extreme wildfires — is amplified in a warming world. Warmer temperatures and increasingly dry air, vegetation, and soils in some regions make fires easier to spread, and more difficult to fight or prevent.
Fire weather seasons have grown longer and more intense since the 1970s, particularly in the western U.S.
Explore interactive maps showing trends in fire weather across the U.S.
Human-caused climate change accounts for at least two-thirds of the rapid increase in fire weather in the western U.S. in recent decades — and contributes to the rising frequency and intensity of wildfires globally.
Meanwhile, as the population has grown and development has expanded into fire-prone areas, so has the overall number of people, homes, and businesses at risk when wildfires occur.
One-third of U.S. homes are in counties with high wildfire risk
Climate Central explored data published by the U.S. Forest Service to understand fire risks to homes across the U.S.
The data show wildfire risks (ranging from low to very high) to homes, residential buildings, and potential development areas.
More than one-third of the U.S. population (nearly 116 million people) and about one-third of all buildings (around 48 million homes and residential structures) are in counties with high or very high wildfire risk to homes.
Western states see some of the greatest risks to homes and other buildings. About 62% of counties in the western U.S. and 13% of counties in the eastern U.S. face a high or very high risk to homes.
Homes in all five counties in Hawaii have a high or very high risk of wildfire.
Nearly all (97% or 56) of California’s 58 counties have a high or very high wildfire risk to homes.
California has the highest population living in counties with high or very high risk: more than 38 million people, or around 97% of the state’s population.
About 87% of Florida counties (58 of 67) have high or very high wildfire risk to homes.
Nearly all Floridians — more than 21 million people or almost 99% of the state’s population — live in counties with high or very high risks.
The top five riskiest states, in terms of counties and people exposed are:
State | Number (percent) of counties with high or very high wildfire risk to homes | State | Total (percent) population in counties with high or very high wildfire risk to homes |
|---|---|---|---|
Hawaii | 5 (100%) | California | 38,325,490 (97%) |
California | 56 (97%) | Florida | 21,332,806 (99%) |
Oklahoma | 74 (96%) | Texas | 10,314,210 (35%) |
Idaho | 42 (95%) | Arizona | 6,951,227 (97%) |
Nevada | 15 (88%) | Colorado | 4,271,467 (74%) |
Download the data to explore other states.
More than 265,000 miles of fire-exposed roads and power lines
When a community experiences a large wildfire, access roads in and out of town may be impacted, blocking evacuation routes and access to critical services. Power lines downed or damaged by fire can cause outages that extend well beyond the burned area.
Research published in 2023 estimated the cumulative total length of roads and power lines exposed to large fires in the contiguous U.S. during the 20-year period from 2000 to 2019.
During the 20-year period (2000-2019), more than 256,000 miles of roads across the contiguous U.S. were exposed to large fires. That’s more than 10 times the circumference of Earth.
The total length of fire-exposed roads during the 20-year period included around 190,600 miles in western states and more than 65,400 in eastern states.
More than 9,200 miles of power lines across the contiguous U.S. were exposed to large fires from 2000 to 2019. That’s more than three times the length of I-80, the highway that spans the country, from San Francisco, California to Teaneck, New Jersey.
The total length of fire-exposed power lines during the 20-year period included around 2,600 miles in western states and nearly 6,600 miles in eastern states.
California, Texas, and Idaho had the most miles of roads and power lines exposed to wildfire during the period of analysis.
Top states with the most miles of road and power lines exposed to large wildfires between 2000-2019.
State | Total miles of road exposed to large wildfires, 2000-2019 | Total miles of power lines exposed to large wildfires, 2000-2019 |
|---|---|---|
California | 45,597 | 2,176 |
Texas | 27,705 | 1,139 |
Idaho | 26,145 | 984 |
More people in fire-prone areas
Overall wildfire risk in any community is a combination of three dynamic and interacting factors:
Hazards: changes in physical wildfire hazards, especially due to climate change.
Exposure: the number of people, homes, and infrastructure in wildfire-prone areas.
Vulnerability: a community’s capacity to prepare for and recover from wildfires — affected by local resources, access to recovery assistance, and the fire-resilience of critical infrastructure.
As climate change worsens wildfire hazards and more people and infrastructure are exposed to fire, communities across the U.S. are at greater risk from dangerous, damaging blazes.
The expansion of the wildland-urban interface — areas where buildings and wildland vegetation overlap — contributes to higher fire exposure and overall risk.
Between 1990-2020, land that falls within the wildland-urban interface expanded about 31% to cover about 293,000 square miles of the contiguous U.S.
Globally, the wildland-urban interface covers less than 5% the land surface but is home to about 3.5 billion people — nearly half of the global population.
LOCAL STORY ANGLES
How many people live in areas prone to wildfire in your state?
Explore interactive maps of the wildland-urban interface (WUI) across the U.S. These maps from the University of Wisconsin-Madison’s SILVIS Lab provide data on national WUI growth from 1990 to 2020.
What can communities do to adapt to wildfire risks?
The U.S. Fire Administration outlines steps communities can take toward being wildfire adapted. A number of fire adaptation strategies include increased use of land management techniques that eliminate excessive fuels, such as prescribed burns, or creating defensible space around homes and other structures. There are toolkits to prepare homes and create evacuation plans.
What are the health impacts of wildfire smoke exposure?
Fine particle pollution from wildfire smoke is a nationwide health concern. The western U.S. has more large fires and local smoke-related pollution. Wildfire smoke, however, can travel hundreds or thousands of miles — fires from the western U.S. and Canada can affect the entire contiguous U.S. Children are especially vulnerable to the harmful health impacts of wildfire smoke. Climate Central’s fact sheet, Climate Change & Children’s Health: Air Quality, details how climate change worsens air quality (including from more and worse wildfires) and impacts children’s health and well-being. Find wildfire smoke tracking maps through the NOAA Office of Satellite and Product Operations and AirNow.
CONTACT EXPERTS
Arash Modaresi Rad, PhD
Water Resource Data Scientist at Lynker
Relevant expertise: Data scientist specializing in hydrology, flood, and wildfire analytics
Contact: amodaresirad@lynker.com
FIND EXPERTS
Submit a request to SciLine from the American Association for the Advancement of Science or to the Climate Data Concierge from Columbia University. These free services rapidly connect journalists to relevant scientific experts.
Browse maps of climate experts and services at regional NOAA, USDA, and Department of the Interior offices.
Explore databases such as 500 Women Scientists, BIPOC Climate and Energy Justice PhDs, and Diverse Sources to find and amplify diverse expert voices.
Reach out to your State Climate Office or the nearest Land-Grant University to connect with scientists, educators, and extension staff in your local area.
METHODOLOGY
Wildfire risk to homes data for counties and states were obtained from the USDA Forest Service’s Wildfire Risk to Communities (WRC). Risk is estimated by modeling wildfire likelihood, intensity, exposure, and susceptibility. Population estimates come from the 2018-2022 American Community Survey. For more information about the methodology, visit the WRC Methods page.
Estimates of cumulative total roads and power lines exposed to large wildfires from 2000-2019 in the contiguous U.S. and in 48 states were obtained from Rad et al., 2023. Exposure is defined as the length of roads and power lines (medium and high voltage, >= 10kV) located within the perimeter of large fires. These figures represent the cumulative total mileage of roads and power lines exposed to large wildfires over the 20-year period of analysis. Note this study classifies the western and eastern regions of the U.S. in a slightly different way (see Figure 2c) than we typically do.