Why Hawaii’s wildfires are so devastating — and ‘predictable’ (2023)

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

Elizabeth Pickett, a co-executive director of the Hawaii Wildfire Management Organization, said that although 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 into 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 the Big Island and Oahu, and 67 mph on Maui, according to Weather Service data.

Some Hawaii officials acknowledged Wednesday that 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 away and 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 in pressure, the stronger the winds.

Some meteorologists have expressed doubt about the role Dora could have played from so far away, suggesting that the high-pressure system alone was enough to provide a strong fan for the flames. Alison Nugent, a University of Hawaii meteorologist who led the 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, to some degree.

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 offshore.

Nugent said it is safe to suspect future hurricanes — which rarely hit Hawaii directly, but often skirt 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, some trends suggest that 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. Research has found that from 1920 to 2012, more than 90 percent of the state experienced drying trends and that no wet season has delivered above-normal precipitation since 2006; instead, there have been 10 drier-than-normal wet seasons in that span.

Scientists say there is no smoking gun linking climate change to those trends. Hawaii precipitation levels have been more closely linked to broader climate patterns such as El Niño, which developed in June and is known for bringing dry conditions to the islands.

Whether climate change may be affecting the frequency or the duration of El Niño is an open question for researchers. The last major El Niño occurred in 2015 and 2016, spurring major weather disasters around the world; climate forecasters say there is a 50 percent chance that the current El Niño episode becomes “strong” or “very strong.”

This year, the wet season brought below-normal precipitation to Hawaii, meaning that conditions already were unusually dry going into the summer, said Ian Morrison, a meteorologist at the National Weather Service in Honolulu.

As the landscape dried out, it intensified the fire threat posed by a Hawaii invader — nonnative fire-prone grasses that have spread in the islands.

Nugent’s research found that before Hurricane Lane hit in 2018, Hawaii had experienced more than a 60 percent decline in the agricultural use of land previously devoted to farming and ranching. Much of that cleared and abandoned land became covered with vegetation 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, what is known as the “grass-fire cycle” is accelerated: In the wake of a fire, the invasive grasses bounce back most easily, crowding out the regrowth of native species and creating more fuel for the next blaze.

“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 that 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 coexist with wildfire, said Melissa Chimera, the coordinator of the Hawaii Wildfire Management Organization’s Pacific Fire Exchange project.

Native flora that are burned do not regrow but are replaced by 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 also can wash debris into the oceans and smother corals and ruin seawater quality.

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