20230810 wildfires
An aerial view shows smoke as wildfires ravage the island in Maui, Hawaii. Image Credit: Reuterse

After winds from a 2018 hurricane helped fuel wildfires in Hawaii, researchers pored over scientific literature for examples of similar disasters. They only found two.

Now, wildfires fanned by winds connected to a hurricane have torched communities in Hawaii for a second time in five years. At least 36 people are dead, and the historic town of Lahaina is all but leveled.

Scientists and wildfire activists say a confluence of factors heighten fire risks in the Aloha State and could trigger more disasters if action isn't urgently taken. These include the spread of flammable nonnative grasses across abandoned farm fields and a failure to manage the vegetation and harden communities. In addition, changes in the climate are fueling stronger hurricanes and may be contributing to drier conditions in Hawaii.

read more

Elizabeth Pickett, co-director of the Hawaii Wildfire Management Organization, said while this week's fires caught many off guard, they should not have been a surprise given all of those conditions. Despite its association with rainforests and waterfalls, Hawaii is a place that burns and is becoming more so.

"We haven't all adjusted, but it's predictable," Pickett said.

Fires began spreading on Maui, Oahu and the Big Island on Tuesday as the National Weather Service issued red-flag warnings. Much of the state has been experiencing months of drought, and the conditions were considered "severe" in parts of Maui around Lahaina.

That meant that whatever sparked the fires lit up dried-out vegetation quickly. And the flames had strong winds to push them toward communities, in some cases sending residents fleeing to the ocean for safety.

Strong winds are common in Hawaii, even during typical summer weather often gusting up to 40 mph. But the breezes buffeting the islands and fanning the flames this week were severe as gusts reached 82 mph on both the Big Island and Oahu, and 67 mph on Maui, according to Weather Service data.

Some Hawaii officials acknowledged Wednesday the severity of the fire conditions caught the state by surprise.

"We never anticipated in this state that a hurricane, which did not make impact on our islands, would cause this type of wildfires," said Lt. Gov. Sylvia Luke, who served as acting governor while Gov. Josh Green (D) was preparing to return to Hawaii.

The winds, at least partly, were the product of a dramatic difference in air pressure between an area of high pressure over the North Pacific and the intense low pressure at the center of Hurricane Dora, which passed hundreds of miles south of the Hawaiian Islands on Tuesday. The greater the difference, the stronger the winds.

Some meteorologists have questioned the role Dora could have played from so far away, suggesting the high-pressure system alone was enough to provide a strong fan for the flames. Alison Nugent, a University of Hawaii meteorologist who led study of the 2018 hurricane and fires, said that even without Dora's influence, the effect of normal winds, dry and racing down Hawaii's mountain slopes, could have been enough to make flames rage. But she said Dora probably contributed to the intensity of the winds, at least.

Similar scenarios occurred in the two examples the researchers found: In 2007, an early-season tropical system fanned existing fires in Florida and Georgia. A decade later, fires across Portugal and Spain killed more than 30 people as a hurricane passed well off shore.

Nugent said it's safe to suspect future hurricanes - which rarely hit Hawaii directly, but often skirt past it - could cause more damage.

"If in the future we have stronger storms, then we could expect stronger winds," she said.

At the same time, there are trends that suggest drought conditions will continue to coincide with hurricanes. The summer is both Hawaii's dry season and hurricane season.

While there is not a clear link between human-caused climate change and drought in Hawaii, the overall trend in the region is declining precipitation and increasing numbers of consecutive dry days. This year, the wet season brought below-normal precipitation, meaning conditions were already unusually dry going into the summer, said Ian Morrison, a meteorologist at the National Weather Service in Honolulu.

But perhaps a bigger change in fire risk than any trends in weather and climate: the spread and growth of nonnative fire-prone grasses.

Like much of Hawaii, Maui once saw its native vegetation replaced by plantations for sugar, pineapple and cattle grazing. In recent decades, those farming activities have been on the decline.

Nugent's research found that before Hurricane Lane hit in 2018, Hawaii had seen more than a 60 percent decline in land used for farming and ranching. Much of that cleared and abandoned land became covered with grasses such as guinea grass and fountain grass, which were introduced to the islands to cover pasture and as ornamental plants.

Both species are adapted to thrive after fire.

When they burn, it creates what is known as the "grass-fire cycle": In the wake of a fire, the invasive grasses bounce back most easily, creating more fuel for the next blaze - and crowding out regrowth of native species.

"It's like throwing a ton of weeds in your backyard and then planting a couple of really fragile plants," said Lisa Ellsworth, an associate professor of fire ecology at Oregon State University who has studied the invasive grasses in Hawaii. "It's a self-perpetuating cycle of more invasive grasses and more wildfire."

Nonnative fire-prone grass and shrub lands accounted for more than 85 percent of the area burned during the Hurricane Lane-induced fires in 2018, researchers found. The fire management group estimates such plants now cover about a quarter of Hawaii.

This vegetation often runs up against populated areas with valuable real estate, and little in the way of fire prevention strategy, such as defensible space around homes. Pickett said significant investments and new policies are needed for those communities to catch up with the fire risks they face.

Beyond the death and damage caused when those fires spread into communities, their effect on Hawaii's landscape is lasting.

Unlike in the western United States, where moderate blazes can improve the health of forests, Hawaii's ecosystems are not adapted to coexisting with wildfire, said Melissa Chimera, the Pacific Fire Exchange coordinator for the wildfire management group.

Native flora that are burned don't grow back but get replaced with invasive plants. One fire in 2007 burned nearly all of the yellow hibiscus, Hawaii's state flower, on Oahu, according to the Pacific Fire Exchange.

Eventual rains can also wash debris into the oceans and smother corals and ruin water quality.

"In terms of the ecology of the area, there is no upside to fire," Chimera said. "There absolutely isn't."