How Bad Are U.S. Wildfires? Even Hawaii Is Battling a Surge.

PA’AUILO, Hawaii — The blaze first swept across parched fields of guinea grass. Then the flames got so close to Emma-Lei Gerrish’s house that she feared for her life.

“I was terrified it was going to jump the gulch,” said Ms. Gerrish, 26, whose Quaker family raises cows and sheep in the hills above Pa’auilo, a ranching outpost on Hawaii’s Big Island. “I’ve never seen a fire this large in my lifetime.”

By the time firefighters got the wildfire under control last month — with a mix of helicopters dropping water while residents drove bulldozers to create firebreaks — more than 1,400 acres had been burned, adding to the tens of thousands across the state since 2018.

Hawaii may be graced with tropical forests, making parts of the islands some of the wettest places on the planet, but it is also increasingly vulnerable to wildfires. Heavy rains encourage unfettered growth of invasive species, like guinea grass, and dry, hot summers make them highly flammable.

Similar to the American West, where dozens of large blazes have raged in recent weeks and fire seasons have grown worse over the years because of extreme weather patterns and climate change, about two-thirds of Hawaii faces unusually dry conditions this summer.

Some of the recent fires, especially on the Big Island and the island of Maui, ravaged areas spanning some 10,000 acres. Since 2018 through last year, at least 75,107 acres across the islands have been lost to wildfires, by far the most devastating stretch in a decade and a half.

While the fires showcase several challenges that Hawaii shares with states in the West, including the spread of highly flammable invasive grasses, the authorities in Hawaii also cite other factors that make Hawaii unique. Those include big shifts in rainfall patterns over the archipelago and tourism’s eclipse of large-scale farming in Hawaii’s economy, allowing nonnative plants to overtake idled sugar cane and pineapple plantations.

Firefighters also have to operate across exceptionally diverse climate zones, extinguishing blazes everywhere from thick tropical forests to semiarid scrublands to chilly elevations where frost can be seen on trees along the slopes of the Mauna Kea volcano.

Even before the latest surge, the area burned annually in Hawaii by wildfires had already climbed fourfold from previous decades, according to Clay Trauernicht, a tropical fire specialist at the University of Hawaii at Manoa. Mr. Trauernicht, who analyzed more than a century’s worth of wildfire records, also found that the area burned each year in Hawaii from 2005-2011 was about 0.48 percent of the state’s total land area, roughly the same as in fire-prone western states on the mainland during the same period.

More than 60 percent of land across Hawaii is currently considered “abnormally dry,” according to the National Drought Mitigation Center, and the vegetation in some of the pasture lands and fallow plantations on the Big Island has the yellow-hued look of arid ranches in the American West.

Even so, greater rainfall during the state’s winter, or wet season, may be just as responsible for Hawaii’s growing wildfires.

A lot of rain helps grass species such as guinea and kikuyu thrive. Both were introduced to the state decades ago, as both forage for livestock and to curb erosion. Some grow up to six inches in a day and provide fuel for fires to quickly leap out of control. Before this year brought dry conditions across much of the state, last winter figured among the wettest in three decades.

“The biomass out there is off the charts,” Mr. Trauernicht said. “When you have a huge wet winter, that will influence fire risk to a greater degree than actual drought conditions.”

Volcanic eruptions and tsunamis also threaten Hawaii, but natural causes such as lightning or flowing lava account for only a small fraction of wildfires in the state, according to fire prevention officials. Instead, people ignite more than 90 percent of Hawaii’s wildfires.

The results can be disastrous for native species steeped in the islands’ culture, like the ohia, a tree that grows easily on new lava flows, featuring flowers which are often scarlet red.

In 2018, for instance, a worker repairing a bulldozer with a plasma cutter, a tool used to cut metal, accidentally sparked a blaze that spread into the Hawaii Volcanoes National Park. The fire burned 3,572 acres of largely native forest.

“Some of these invasive species are actually colonizing barren lava flows, taking away these natural fuel breaks,” said Greg Funderburk, the park’s fire management officer. “Now we have a sea of grass in what would have been barren rock with sparse ohia trees.”

While the cause of the fire in Pa’auilo last month remains under investigation, the blaze in a rural area that normally has wetter weather this time of year — and where wildfires were once a rarity — has alarmed officials.

Adding to concerns, the National Oceanic and Atmospheric Administration warned in its latest forecast that drought conditions should intensify this summer on the Big Island and some other parts of Hawaii.

Authorities in at-risk areas are already pleading with residents to avoid watering yards or washing cars to conserve water. On Molokai, Hawaii’s fifth-largest island, residents are fretting about dry conditions after hundreds of axis deer were found dead of starvation last year.

Whatever the cause, a buildup of guinea grass fueled the Pa’auilo blaze. The voluminous underbrush in an inoperative eucalyptus plantation quickly allowed the fire to swell in size, stunning residents of the village, which has a few hundred residents.

“This whole town would have been gone if the fire got much closer,” said Jodi de Luz, 36, who works at a feed store that is a gathering place to buy livestock supplies and exchange gossip. “It’s dryer than it’s ever been here.”

The blaze got within about a half-mile of the town’s lone public school before firefighters laboring through the night were able to contain it. Local residents with bulldozers helped the crews construct fire lines that are still visible around Pa’auilo.

The expense of renting helicopters, which can cost more than $1,000 an hour, plus the geography of the state, an island chain in the Pacific, also weigh on the minds of firefighters.

“It’s not like the mainland where you can drive in crews from other states,” said Kevin Kaneshiro, 37, the captain at the nearby fire station in Honoka’a, which responded to the Pa’auilo fire. “You have to make do with what you have.”

Mr. Mora, who has a project to bolster native vegetation by planting thousands of trees around Hawaii, said that the spike in wildfire activity also stems from social problems, such as the islands’ acute housing shortage.

“Many of the wildfires here get triggered by the homeless, who mean no harm,” Mr. Mora said. “These people need to eat, they need to cook their own food, next thing you know a tiny accident triggers a blaze.”

In Pa’auilo, residents remain unnerved by just how close the recent wildfire got to their homes. Some areas alongside the fire scar were still smoldering in late June, with residents calling the local fire station to extinguish the pop-up blazes.

As if highlighting the risks, guinea grass has already begun sprouting on land blackened by the fire. Cole Ahuna, whose home was almost consumed by it, wondered what could happen if the grasses continue to grow, the dry weather persists and the winds pick up again.

“The fire got all the way to the horse pasture before the dozers came and cut if off,” said Mr. Ahuna, 19. “Something like this was unheard of around here when I was growing up. Now it’s a different world.”