Why were California's wine country fires so destructive?

As of late October more than a dozen wildfires north of San Francisco had killed more than 40 people, burned approximately 160,000 acres and destroyed more than 7,000 structures.

This tragic loss of life and property is unprecedented in California. However, the fires are not anomalous events in terms of their size, intensity or the speed with which they spread. Indeed, the path of the destructive Tubbs fire in Napa and Sonoma counties mirrors that of the Hanley fire of 1964. This extreme wind-driven fire burned under similar conditions, across much of the same landscape and covered an area substantially greater than the recent Tubbs fire.

Strikingly, though, no lives were lost during the Hanley fire and only 29 structures were destroyed. Why did these two fires, 50 years apart, burn on the same general landscape, under similar extreme winds, with such different human impacts? Fire scientists will study these events intensively to parse out the relative importance of various factors. But it is clear that two factors probably were major contributors: wind and population growth.