Why Maui's deadly wildfires spread so quickly
Strong winds, dry weather and the spread of non-native grasses all cited as factors
The wildfires that rapidly swept across Maui this week led to thousands of evacuations, burnt-out homes and the deaths of at least 55 people.
The fires started Tuesday and took the island by surprise, ripping through the town of Lahaina, a historic former capital that dates back to the 1700s and has long been a favourite destination for tourists.
The flames came so quickly that some residents sought refuge by jumping in the Pacific Ocean.
It was the latest in a series of extreme weather events around the globe this summer, including the record-setting wildfires in Canada.
Experts say climate change is increasing the likelihood of such events. Here's a closer look at the factors that led to the situation in Hawaii.
Dry, hot weather
Hawaii isn't traditionally known as a wildfire hotspot, though researchers have noted a steep increase in recent years.
One study cited deforestation, the abandonment of agricultural lands and the introduction of non-native, fire-prone grasses as factors that have made Hawaii more susceptible to fire.
The precise cause of the fires has not yet been determined, but the U.S. National Weather Service had issued warnings for the Hawaiian Islands for high winds and dry weather — conditions ripe for wildfires.
Vegetation in Maui's lowland areas was particularly dry this year, after below-average precipitation this spring and summer, experts said.
The U.S. drought-monitoring service lists Maui as being in a state of "moderate" to "extreme" drought.
Ze'ev Gedalof, an associate professor researching forestry and climatology at the University of Guelph, described the wildfires as an "accident waiting to happen."
The natural vegetation is not adapted to wildfire, he said, pointing out that nearly all wildfires in Hawaii are caused by human action.
When a fire does start, he said, "the landscape is ready to burn and people are living in places that are vulnerable to those burns."
The wet season can spur plants like Guinea grass, an invasive species found across parts of Maui, to grow as quickly as 15 centimetres a day and reach up to three metres tall, said Clay Trauernicht, a fire scientist at the University of Hawaii.
When those grasses dry out, it creates a tinderbox that's ripe for wildfire, he said.
"These grasslands accumulate fuels very rapidly," Trauernicht told The Associated Press. "In hotter conditions and drier conditions, with variable rainfall, it's only going to exacerbate the problem."
High winds from Hurricane Dora
Trade winds are a normal feature of Hawaii's climate. They're caused when air moves from the high-pressure system north of Hawaii to the area of low pressure at the equator, at the south of the state.
But Hurricane Dora, which passed south of Hawaii earlier this week, contributed to unusually strong winds that helped spread the fire.
Experts say it exacerbated the low-pressure system and increased the difference in air pressure.
Céline Villeneuve, a Quebecer who lives in Maui, said she got an alert on her phone in the middle of the night.
She wasn't in the evacuation area, with the winds pushing the fire south.
"I woke up because I could smell the smoke. And I went outside and I could see the red sky and the moon was red, and the fire was right there," she told CBC Montreal's Daybreak.
"Many of our friends lost their homes … It's just absolutely devastating."
Climate and fire
Climate change not only increases the fire risk by driving up temperatures, but also makes stronger hurricanes more likely. In turn, those storms could fuel stronger wind events like the one behind the Maui fires.
In this case, the University of Guelph's Gedalof said, a multitude of factors created a "perfect storm" for a devastating fire.
The situation drives home the idea that nowhere is immune to such extreme events, said Kelsey Copes-Gerbitz, a postdoctoral researcher at the University of British Columbia's faculty of forestry.
"It's leading to these unpredictable or unforeseen combinations that we're seeing right now and that are fuelling this extreme fire weather," Copes-Gerbitz told The Associated Press.
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With files from CBC Montreal's Daybreak, The Associated Press and Reuters
