There have always been forest fires, of course. But their patterns are changing because of people.

Humans are often responsible for starting the fires, accidentally or intentionally; some spin out of control. The suppression of smaller fires can lead to buildups of burnable brush that can feed a huge, destructive blaze when it is sparked. That is true of the California blaze and many others in the American West; it is also what has happened in significant recent blazes in Turkey, according to Chadwick Oliver, director of the Global Institute of Sustainable Forestry at Yale University.

“We don’t need much of a spark to set off a fire that spreads long distances through the crowded, continuous forests,” Dr. Oliver said.

And climate change, to which humans contribute, is heating up and drying out some — though not all — areas.

Global studies of wildfire patterns are rare. But a paper published last year in the journal Ecosphere predicted that climate change would have an effect on wildfires that varies widely, especially in accordance with a given region’s precipitation patterns.

The paper — which focused on climate change but not other variables, like changing land management — projected that dry parts of the middle latitudes and Australia are likely to see more fires over the long term. The American West, already a tinderbox, will become more fire-prone. So, too, will high-latitude areas, the study found, partly because the carbon-rich peat soil there will burn under extreme weather conditions.