Wildfires and Climate Change
Large wildfires burn more than twice the area they did in 1970, and the average wildfire season is 78 days longer.
Research shows that changes in climate, especially earlier snowmelt due to warming in the spring and summer, have led to hot, dry conditions that boost this increase in fire activity in parts of the West. For much of the West, projections show that an average annual temperature increase of 1 °C would increase the median burned area per year. The increase could be as much as 600 percent in some types of forests.
Wildfire risk depends on a number of factors, including temperature, soil moisture, and the presence of trees, shrubs and other potential fuel. All these factors have strong direct or indirect ties to climate variability and climate change. Warmer temperatures and drier conditions increase the chances of a fire starting, or help a burning fire spread. Such conditions also contribute to the spread of the mountain pine beetle and other insects that can weaken or kill trees, building up the fuels in a forest. Although our choices regarding land use and firefighting tactics can also play a role in lowering or raising risks, observed and anticipated changes in climate have and are expected to increase the area affected by wildfires in the United States.
Threats Posed by Wildfires
Since 2000, 10 forest fires in the United States have caused at least $1 billion in damages each, mainly from the loss of homes and infrastructure, along with firefighting costs.
- In 2015, wildfires burned more than 10.1 million acres across the country, the highest annual total acreage burned since record-keeping began in 1960. The costliest fires occurred in California, where more than 2,500 structures were destroyed in the Valley and Butte wildfires.
- In 2011, the Las Conchas Fire in New Mexico became the state’s largest in history by a factor of three. In 2012, that record was broken as the Whitewater-Baldy Complex fire burned nearly twice as many acres as the Las Conchas Fire.
- Wildfires burned more than 9 million acres in 2012. Colorado’s two most destructive fires ever—the Waldo Canyon and High Park fires -- happened during this particularly destructive season.
Estimates of the percentage increase in the area burned in regions across the West for a 1.8 degrees Fahrenheit, 1 degree Celsius warming. The different regions correspond to different “ecoprovinces,” which distinguish areas with distinctive vegetation types and climate conditions. Values are drawn from median burn estimates from a fire model. All areas exhibit increases; many of them exceed a doubling (i.e., value shown is more than 100%) and some areas show a five-fold increase (i.e., value shown is more than 400%). Source: National Research Council, "Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia ( 2011 ).
Damage to homes and other buildings can be substantial, in part from the recent and rapid development of areas near fire-prone forests. As the number of homes located near forests at risk of wildfire has increased over the past two decades, U.S. Forest Service fire suppression expenditures have risen from 16% of their appropriated budget to more than 50 percent. State wildfire expenditures also increased substantially. While more buildings add to the risk of damage from natural fires, the presence of people in wildlands increases the risk of fires starting. In fact, as many as 90 percent of wildfires in the United States are caused by people.
Beyond direct damage to the landscape, several public health risks are related to wildfires. Smoke reduces air quality and can cause eye and respiratory illness, especially among children and the elderly. Wildfires can also hasten ecosystem changes and release large amounts of CO2 into the atmosphere—contributing to further climate change.
How to Build Resilience
Communities, builders, homeowners and forest managers can reduce the likelihood and impacts of wildfires by:
- Discouraging residential developments near fire-prone forests through smart zoning rules.
- Increasing the space between structures and nearby trees and brush, and clearing space between neighboring houses.
- Incorporating fire-resistant design features and materials in buildings.
- Increasing resources allocated to firefighting and fire prevention.
- Removing fuels, such as dead trees, from forests that are at risk.
- Developing recovery plans before a fire hits, and implementing plans quickly after a fire has occurred to reduce erosion, limit flooding, and minimize habitat damage.
To Learn More
Cal-adapt Wildfire Risk Map
NASA Wildfires: A Symptom of Climate Change
USFS Climate Change Resource Center: Wildland Fire and Climate Change