A brush fire that scorched at least 40,000 acres on Hawaii’s Big Island is the largest ever on the island, officials said, and the area burned may pose a risk for mudslides if there are heavy downpours in coming months.

Mandatory evacuations forced residents in three communities out of their homes over the weekend, but the orders were lifted late Sunday as conditions stabilized.

Cyrus Johnasen, a spokesperson for the Hawaii County mayor’s office, said Tuesday that the confirmed area burned remained around 40,000 acres. Johnasen told The Washington Post that the fire was 75 percent contained, and that officials expect the blaze to be 85 to 90 percent contained by the end of Tuesday, local time. Officials say that the fire is no longer a threat to residences or homes but that there is concern about an effect on forest reserves and species habitats.

He also warned of “after effects” even when the flames are curbed. For the next two or three months, heavy rains could cause mudslides, he said.

“All the areas that have burned, the soil no longer has roots to hold it in place,” he said. “ … So that 40,000 acres of burned soil could translate to mudslides anywhere along the west side of the island, resulting in potential road closure or hazardous conditions.”

He said residents should be cautious on roads if those heavy rains arrive.

The fire ignited amid recent drought conditions in parts of the state of Hawaii. Nearly 60 percent of the state is experiencing at least moderate drought, according to the U.S. Drought Monitor. Much of the Big Island is abnormally dry or experiencing moderate drought.

A National Weather Service forecast from early July warned of “increasing drought conditions” in parts of the state during the summer.

“It’s important to note that by no means are we out of this drought,” Johnasen said. “The threat of this particular fire is over, but folks should keep in mind who live in those dry areas that more forest fires and brush fires could spark over the course of the summer. We want folks to remain cautious and remain alert and have an evacuation plan in the event something becomes more of a threat to homes.”

Exceptional heat and drought also have created tinderbox conditions elsewhere, fueling wildfires across the western United States this year. The National Interagency Fire Center lists 97 active large fires burning in the country, mostly in Western states.

Clay Trauernicht, part of the extension faculty in ecosystems and fire at University of Hawaii at Manoa, said fires in Hawaii are fueled by widespread tropical grasses.

“That’s what drives our fire risk here,” Trauernicht told The Post.

“We’ve been in pretty deep drought conditions, especially in that part of the Big Island,” he added. “The other thing that hammers us is we’ve had an especially wet wintertime.”

Wet winters with excess rainfall lead to more tropical grass growing, accumulating more fuels that later dry out and can increase the chance of fires.

“What we’re seeing is that perfect one-two punch,” Trauernicht said.

He said there’s also been a long-term trend of grasslands expanding, in part driven by a reduction in agriculture and ranching operations over the past two or three decades. With less land under production, grasses have further filled in.

Trauernicht said there are occasional lightning strike-sparked fires, brush fires and fires from active lava flows. In 2018, an eruption from the Kilauea volcano on the Big Island devastated surrounding areas. Fissures opened up, spewing lava into residential roads and destroying structures in its path.

But a large majority of fires are started by people, Trauernicht said. “Human ignitions coupled with an increasing amount of nonnative, fire-prone grasses and shrubs and a warming, drying climate have greatly increased the wildfire problem,” notes the Hawaii Wildfire Management Organization website.

Roth pointed fingers at the drought as firefighters fought the record blaze in Hawaii County.

“With the drought conditions that we’ve had, it is of concern,” the mayor said, according to the Associated Press. “You see something like this where you’re putting thousands of homes in danger, it’s very concerning.”

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