A data analysis by the CBS News Data Team shows a growing number of Bay Area homes are facing increased wildfire risk.

In the 1990s, about 917,000 homes in the Bay Area were in Wildland Urban Interface areas, or WUI. Those areas are on land that sits on the edge or within wilderness, putting it at high fire risk.

By 2020, there were 1.2 million homes in the WUI, a 27% increase.

In some areas, more than 80% of homes are in the WUI:

In terms of growth, Alameda County saw a 40% increase in the number of homes in the WUI (between 1990 and 2020).

Contra Costa County saw a 33% increase in the same time frame.

In Alameda County, about 1 in 3 homes are in the WUI. In Contra Costa County, about 2 in 3 homes are in the WUI.

The city of Brentwood, which has a population of 65,126, saw a 23x increase:

Andy Bozzo, a battalion chief at the Contra Costa County Fire Protection District, knew well about the WUI even before he was a firefighter. Bozzo, a biology major in college, wrote about "forest succession in a wildfire environment" for his final senior paper.

"Most plant species [native to California] are born to burn. They're evolved to burn and live in a fire environment. We also need to evolve to live in a fire environment in California. That can be tough sometimes," Bozzo said. "Now, we're creating these dense neighborhoods and pushing really deep into these wildlands that it's just a fact of life… When you push into wildland, you're going to have higher encounters with things like wildfire."

Last June, the Empire Fire sparked near homes in Brentwood, including Rodney Griffin's.

Griffin, who moved into his Brentwood home in 2002, said it was the worst fire he'd seen from his home.

"We've had fires within a couple of miles of the place that I've often watched from upstairs burn, but none have really quite threaded our home quite like (the Empire Fire)," Griffin said. "We could've had quite a lot of destruction."

No homes or structures were destroyed in the Empire Fire, which was fully contained after burning 250 acres.

"[These neighborhoods are] beautiful. They have beautiful views. But in the summer time, if a fire gets a good head of steam, it can spot ahead of itself," Bozzo said. "That's what we worry about in neighborhoods like this."

Separately, for the first time in 15 years, Cal Fire also released a new fire-risk map for the Bay Area. The red areas on the map represent very high-risk fire zones.

Sonoma County saw the biggest increase with that designation, while Oakland saw its fire hazards reduced.

Homeowners in the danger zones will eventually have to use more fire-resistant building materials and landscaping and create a five-foot "ember-resistant" zone around their homes.

In the Los Angeles wildfires earlier this year, fences fueled the spread of the flames.

The state will also require fences that connect to homes to be made out of something other than wood.

Cal Fire is still rolling out its fire-risk maps through the rest of the state. The new maps are not expected to change how insurance companies make their policy decisions.