Why do houses burn but trees remain? Photos from California wildfires reveal lessons for B.C.
Retired U.S. Forest Service scientist examines wildfire footage to find ways to reduce burn risk
The wildfire situation in California is now the deadliest in the state's history, with at least 50 people killed, more than 100 missing or unaccounted for and the town of Paradise almost entirely destroyed.
But the footage coming out of affected communities tells an unexpected story, says a U.S. fire expert — one that could have lessons for wildfire prevention measures.
Jack Cohen, a retired U.S. Forest Service scientist, focuses his research on investigating how homes ignite during extreme wildfires and how fires move through communities.
He says fireproofing individual homes may be the most critical part of preventing the spread of wildfires.
"Our perception is that this wall of fire comes through and destroys everything, and yet what I'm seeing is that there couldn't have been a wall of fire," Cohen told Stephen Quinn, the host of CBC's The Early Edition.
"The thing that would have carried the wall of fire is still there: The trees are still there and the structures are destroyed."
Instead of a wall of flames descending, burning embers blow downwind and ignite many spot fires over a wide area.
"That's how the whole area can be burning at the same time," Cohen explained.
That's also why, from the photos coming out of the damaged communities, it looks almost as though there were hundreds of individual house fires rather than one fire sweeping through the entire town.
Removing clutter around homes that could become combustible is crucial, he said, and making sure there is nothing touching a structure that could ignite it.
"We make sure that we have no debris on the structure. We make sure that nothing can burn ... within the first metre to metre-and-a-half [of the house]," he said.
But that doesn't necessarily mean cutting back all vegetation.
As the photos show, large trees will still remain standing after a building burns down.
"Don't just look at destroyed structures," Cohen said. "Look at the area around the destroyed structures and what you see is unconsumed vegetation."
Instead, he suggested, keep a 30 metre buffer around buildings by clearing debris and surface fuels like old firewood, twigs and dried grasses.
"Ignition-resistant communities, that gives us an option for safety."
With files from The Early Edition