Another wildfire burning in Hawaii threatens irreplaceable rainforest on Oahu

A screenshot of a video provided by the Hawaii Department of Land and Natural Resources shows a wildfire burning near Mililani, Hawaii, on Nov. 2, 2023. (Credit: Hawaii Department of Land and Natural Resources)

A wildfire burning in a remote Hawaii rainforest is underscoring a new reality for the normally lush island state just a few months after a devastating blaze on a neighboring island leveled an entire town and killed at least 99 people.

No one was injured and no homes burned in the latest fire, which scorched mountain ridges on Oahu, but the flames wiped out irreplaceable native forestland that's home to nearly two dozen fragile species. And overall, the ingredients are the same as they were in Maui's historic town of Lahaina: severe drought fueled by climate change is creating fire in Hawaii where it has almost never been before.

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"It was really beautiful native forest," said JC Watson, the manager of the Koolau Mountains Watershed Partnership, which helps take care of the land. He recalled it had uluhe fern, which often dominate Hawaii rainforests, and koa trees whose wood has traditionally been used to make canoes, surfboards and ukuleles.

"It’s not a full-on clean burn, but it is pretty moonscape-looking out there," Watson said.

The fact that this fire was on Oahu’s wetter, windward side is a "red flag to all of us that there is change afoot," said Sam ’Ohu Gon III, senior scientist and cultural adviser at The Nature Conservancy in Hawaii.

The fire mostly burned inside the Oahu Forest National Wildlife Refuge, which is home to 22 species listed as endangered or threatened by the U.S. government. They include iiwi and elepaio birds, a tree snail called pupu kani oe and the Hawaiian hoary bat, also known as opeapea. The U.S. Fish and Wildlife Service, which manages the refuge, does not know yet what plants or wildlife may have been damaged or harmed by the fire, spokesperson Kristen Oleyte-Velasco said.

The fire incinerated 2.5 square miles (6.5 square kilometers) since first being spotted on Oct. 30 and was 90% contained as of Friday. Officials were investigating the cause of the blaze roughly 20 miles (32 kilometers) north of Honolulu.

The flames left gaping, dark bald spots amid a blanket of thick green where the fire did not burn. The skeletons of blackened trees poked from the charred landscape.

The burn area may seem relatively small compared to wildfires on the U.S. continent, which can raze hundreds of square miles. But Hawaii's intact native ecosystems aren't large to begin with, especially on smaller islands like Oahu, so even limited fires have far-reaching consequences.

One major concern is what plants will grow in place of the native forest.

Hawaii’s native plants evolved without encountering regular fires and fire is not part of their natural life cycle. Faster-growing non-native plants with more seeds tend to sprout in place of native species afterward.

Watson said an Oahu forest near the latest fire had uluhe ferns, koa trees and ohia trees before a blaze burned less than a square mile of it 2015. Now the land features invasive grasses that are more fire-prone, and some slow-growing koa.

A much larger 2016 fire in the Waianae mountains on the other side of Oahu took out one of the last remaining populations of a rare tree gardenia, said Gon.

There are cultural losses when native forest burns. Gon recalled an old Central Oahu story about a warrior who was thrown off a cliff while battling an enemy chief. His fall was stopped by an ohia tree, another plant common in the incinerated area. Feathers from Hawaii's forest birds were once used to make cloaks and helmets worn by chiefs.

Watson's organization is coordinating with the Fish and Wildlife Service to conduct initial surveys of the damage. They'll devise a restoration plan that will include invasive species control and planting native species. But there are limits to what can be done.

"It’ll never be able to be returned to its previous state within our lifetimes," Watson said. "It's forever changed, unfortunately."

The Mililani Mauka fire — named after the area near where the fire began — burned in the Koolau mountains. These mountains are on Oahu's wetter, windward side because they trap moisture and rain that move across the island from the northeast.

But repeated and more prolonged episodes of drought are making even the Koolaus dry. Gon expects more frequent Koolau fires in the future.

"There has been a huge uptick in the last 10 years, largely in Waianae range, which is the western and drier portion of the island," Gon said. "But now we’re seeing fires in the wet section of the island that normally doesn’t see any fires at all."

Hawaii fires are almost always started by humans so Gon said more needs to be done to raise awareness about prevention. Native forests could be further protected with buffer zones by planting less flammable vegetation in former sugarcane and pineapple plantation lands often found at lower elevations, he said.

Many of these now-fallow fields sprout dry, invasive grasses. Such grasses fueled the blaze that raced across Lahaina in August, highlighting their dangers. The cause of that fire is still being investigated, but it may have been sparked by downed power lines that ignited dry grass. Winds related to a powerful hurricane passing to the south helped spread the blaze, which destroyed more than 2,000 buildings and homes for some 8,000 people.

The fire is likely to affect Oahu’s fresh water supply, though this is challenging to measure. Oahu’s 1 million residents and visitors get their drinking water from aquifers, but it usually takes decades for rain to seep through the ground to recharge them. Native forests are the best at absorbing rain so the disappearance of high-quality forest is certain to have some effect, Watson said.

State officials are seeking additional funding from the Legislature next year for updated firefighting equipment, firebreaks, new water sources for fire suppression, replanting native trees and plants, and seed storage.

Firefighters and rain last week finally tamped down the Oahu blaze, but Gon urged action now "to make sure that it doesn’t turn into yearly fires nibbling away at the source of our water supply."

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