Here’s how we analyzed the Colorado wildfire data
CPR News analyzed forest fire data from the US Forest Service Fire Program Analysis – Fire Database, or FPA-FOD. Federal, state, and local agencies have separate systems for reporting wildfires, and the FPA-FOD is the only database that contains records of wildfires and their sources of ignition reported by each level of government. The most recent version, released in 2021, includes forest fire records from 1992 to 2018. Records submitted to the database are cleaned up to remove duplicates and forest fires with inaccurate starting locations. Only forest fires where the ignition point is accurate within a mile radius are included. A full description of how the data is cleaned can be found here.
The records include the coordinates of the ignition point and the date of discovery of each forest fire. Each record contains information indicating whether the fire was started naturally, by humans, or whether the cause is unknown; as well as a separate field for information on the specific cause of the inflammation, such as lightning, vehicles, arson, or railroads. The agency that reported the fire, the agency that responded to the fire, and the final burn area are also included.
In some states, forest fire reporting is voluntary. An estimate by Thomas and Butry (2012) showed that only two-thirds of fires of any type, including forest fires, are reported to the US fire service registration system, the NFIRS. Subsequently, this dataset – and all other U.S. wildfire datasets – provide an incomplete picture of U.S. wildfires. Researchers estimate that small, man-made fires make up the bulk of unreported wildfires.
Numerous forest fire databases have been created to organize emergency response teams and recover costs associated with extinguishing fires. As a result, these wildfire records are not frequently updated to reflect the results of origin and cause investigations.
To control the different reporting requirements between states, CPR News limited its analysis to wildfires that started on or after January 1, 2000 and burned 1,000 acres or more. It is unlikely that a fire of this size will not be recorded in the FPA-FOD database. Fires of this size are also the most likely to have accurate data on the cause and source of ignition.
CPR News separately analyzed all wildfires in the FPA-FOD database without a size constraint and found Colorado still had the highest rate of man-made fires without a listed ignition source. A separate analysis of data from the National Interagency Fire Center, using fires that burned 1,000 acres or more that were classified as man-made and a general cause that was lacking data or “investigated but not known,” showed that Colorado was tied with New Mexico for the highest percentage of man-made forest fires with an unknown or undetermined ignition cause.