Maui wildfires burned trees, despite claims online
- This article is more than one year old.
- Published on August 17, 2023 at 22:56
- 4 min read
- By Manon JACOB, AFP USA
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"Everything was burnt down except the trees in Maui. Something doesn't add up here," says an August 13, 2023 Instagram post sharing footage of the wildfire damage.
Other social media users shared similar posts, often alluding to theories that the inferno could have been an intentional attack -- a claim that AFP has previously debunked.
Blazes decimated the historic seaside town of Lahaina in early August, killing more than 110 people -- the deadliest US wildfires in more than a century.
Authorities are still probing the cause of the Hawaii disaster, but The Washington Post and other US media have reported that fallen power lines may have triggered the first blazes.
The fires reduced homes and businesses to ashes, and -- despite the claims swirling online -- damaged local vegetation such as a 150-year-old banyan.
The state's lead arborist, Steve Nimz, told local news outlet KITV that the iconic tree in Lahaina, whose canopy was blackened and scorched by the fire, is "in a coma."
As for why the flames spared some trees, experts told AFP that phenomenon is not out of the ordinary.
"There is a physical explanation why trunks and large branches of trees don't burn and why houses do," said Ernesto Alvarado, a research associate professor in the University of Washington's School of Environmental and Forest Sciences, on August 15. "It has to do with moisture content, residence time of the fire and composition."
"Residence time" refers to how long a fuel particle spends in a flame (archived here). Alvarado said some trees can become "snags" for fires due to their root systems.
"If the trees are alive, the fire does not burn the roots," he said. "But they can snap from the base if the winds are too strong."
Camille Stevens-Rumann, assistant director of ecological research and monitoring at the Colorado Forest Restoration Institute, told AFP on August 15 that different types of vegetation also react in various ways.
Some trees native to Maui, including the mamane, have fire-resistant properties (archived here), research shows.
"Many tropical trees like those that grow in Hawaii often have really high water content, meaning they are less likely to burn even when it is dry compared to grass and all the dry timber homes and structures are often built for," Stevens-Rumann confirmed.
Susan Buchanan, director of public affairs for the National Weather Service, previously told AFP that "a mix of dry vegetation, strong winds, dry subsiding air and low relative humidity helped to spread the deadly fires once they were ignited."
Experts have said non-native grass in old sugarcane fields fueled the flames.
'Better ignition sources'
Unlike trees, homes have "lots of nooks and crannies that wind-blown embers can land on and ignite, from the roof to the foundation," said Courtney Peterson, a climate adaptation specialist at Colorado State University, in an August 15 email.
Post-fire studies also indicate a variety of factors contribute to a home's "ignition zone," including the amount of debris around the property, how trees are spaced out and whether there is flammable material on or near the structure (archived here).
Wildfires may even spread from house to house in a "domino effect" if they are close together, leaving surrounding vegetation intact. The US Department of Agriculture has reported similar burn patterns in places such as Grass Valley, California (archived here).
That is "essentially a result of homes sometimes being better ignition sources and often built in nice rows," said Stevens-Rumann of the Colorado Forest Restoration Institute.
AFP has debunked additional claims about the Hawaii wildfires here and here.
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