California's fire season is the worst on record. Still more wildfires rage through the state now, spurred by the Santa Ana winds. Over and over, I've read that the predominant causes of the fires are human.
This was true even in the late '80s, as John McPhee noted, "Ignitions are for the most part caused by people—through accident or arson."
I decided to find some data to see how those causes stacked up.
The highest and lowest ranked causes are highlighted when the chart loads. These represent the cumulative ranking across all years. Lightning, a natural cause, often floats to the top, but that's only because on the human side, the vote is split between more than twenty options. Lightning doesn't predominate in all states, though. In Alabama, the number one cause is pyromania. In Indiana, it's brakeshoes. In Minnesota, it's field burning. There are a couple of overall trends, too. Smoking is going down as a cause, and powerlines are going up.
Use the dropdown to filter by state. Hover to see the rest and to get a tooltip with additional information. To see a more detailed geographic presentation of the data, take a look at the map.