The windshield wipers are set to intermittent, clearing spatters of rain as we set our sights on a patch of blue ahead. Assembled in the vehicle are a group of scientists and a forester, packed in alongside bulky containers of equipment. “The overstory here is all ‘ōhi‘a trees and it looks OK, but wait till you see where we’re headed,” says JB Friday, the forester, from the back seat of the Yukon.

I nod, looking at the canopy of native forest flying by. But then, about four miles in on Stainback Highway, the scenery changes abruptly, and I get my first glimpse of the devastation. The tall, verdant crown of ‘ōhi‘a lehua is gone. The tree’s telltale, slender trunks and bushy limbs, often festooned with fiery blooms of pink, orange, yellow or red, are leafless, shriveled skeletons—their bony, twisted branches like brittle fingers against the backdrop of a gray sky.

“All of these trees died in the past six years,” explains Friday, a forester with the University of Hawai‘i Cooperative Extension Service. “We’re talking thousands in this area. That number of trees dying in that amount of time is a disaster.”

Cause of death: an invasive microscopic fungus that prevents the ‘ōhi‘a from transmitting water from the roots to the leaves, killing it quickly, the arboreal equivalent of a heart attack. There are two species of the pathogen: Ceratocystis huliohia (“that which overturns ‘ōhi‘a”) and Ceratocystis lukuohia (“destroyer of ‘ōhi‘a”)—the second more virulent than the first—entering the tree through open wounds made by humans, animals or strong winds. Both forms of the pathogen cause the disease known as rapid ‘ōhi‘a death (ROD).

“What was so puzzling was that the onset of symptoms is really quick,” says Friday. “That’s what first convinced me that this was something different than we’d ever seen before. The tree will look perfectly green, and in two weeks it’s completely brown.” Since it was first detected in 2014, the more virulent ROD pathogen (C. lukuohia) has infected almost twenty thousand acres of forest and killed one million trees on Hawai‘i Island. If it can’t be stopped, it will irreversibly change the island’s ecosystems. The more virulent strain has also shown up on Kaua‘i, and the less virulent C. huliohia was discovered last year on Maui and O‘ahu.

It’s hard to overstate what’s at stake: ‘Ōhi‘a-dominated forests cover close to one million acres of land across the state and make up the largest portion of the canopy in native forests. ‘Ōhi‘a lehua are endemic to Hawai‘i—they’re found nowhere else on Earth. They are among the first trees to colonize new lava flows and are therefore essential to soil development. The trees also protect Hawai‘i’s watersheds, provide shelter and food for endemic birds, provide water for seedlings and are deeply rooted in Hawaiian culture and legend.

“If the ‘ōhi‘a are lost, the countless native species that grow in its shade will never be, the native birds that rest in its boughs will have no roost and rain that falls in Hawai‘i’s old-growth forests will merely rush away, taking delicate island soils with it,” says Cindy Orlando, superintendent for Hawai‘i Volcanoes National Park (HVNP). “Even the cycle of creation after a lava flow would be disrupted when there are no ‘ōhi‘a to help bring life back to the land.”

So it’s all hands on deck to protect the most important native tree in Hawai‘i’s forests, which is why HVNP, the US Department of the Interior Office of Native Hawaiian Relations, the Hakalau Forest National Wildlife Refuge and the National Invasive Species Council Secretariat worked in partnership with Conservation X Labs last year to send out an SOS—dubbed the ‘Ōhi‘a Challenge—across the world. The urgent call: to harness technology and ingenuity to help identify infected ‘ōhi‘a trees early, minimize the spread and eliminate the pathogens that are causing ROD altogether.

Fifty-six applications for the challenge were received from across the United States, Europe and Africa—everything from fungus detection dogs to screening methods for environmental DNA tracing. The winning entry came from right here at home. Unmanned aircraft systems and remote sensing to detect the pathogen earned Ryan Perroy of the University of Hawai‘i at Hilo the $70,000 ‘Ōhi‘a Challenge prize. Perroy is an associate professor and principal investigator with the Spatial Data Analysis & Visualization lab (SDAV), a research unit at the university that uses geospatial tools to solve local environmental problems in Hawai‘i and across the Pacific. Perroy’s ROD solution uses high-resolution cameras and other sensors to improve early detection. A second component involves a drone device he’s named Kūkūau, after a type of crab, to collect samples from the canopy of hard-to-reach ‘ōhi‘a trees for laboratory analysis. These innovations offer a glimmer of hope, a piece of the puzzle: How can we save Hawai‘i’s native forests?

We park beneath the husks of diseased ‘ōhi‘a—“ground zero,” Friday calls it—one of the first areas on Hawai‘i Island to be wiped out by ROD. Components of the system are actually built for drone racing and high-speed maneuvering, explains Perroy, as he attaches the star of the show, Kūkūau, to a hexacopter drone. This prototype brandishes a claw on one end for grasping an ‘ōhi‘a branch and a retractable saw mounted under the claw. Once the specimen is secured, the horizontal arm of Kūkūau swings around to spray pruning sealant on the open wound. When all the kinks are worked out, the final device will be made out of 3D-printed plastic, carbon fiber and aluminum.

The three scientists work together in a seamless, nearly nonverbal dance to launch Kūkūau. Geospatial research specialist Timo Sullivan flies the drone, Perroy operates Kūkūau and geospatial research associate Eszter Collier surveys the operation. The hexacopter whirs like a swarm of angry bees as it gently lifts Kūkūau into the air. Getting to the right spot takes a bit of work, but a few minutes into the flight, Kūkūau grabs hold of a branch. The spinning blade cuts, and when the drone pulls away with a large specimen in its claw, the crew erupts in cheers.

“Part of the problem with ROD is we can’t confirm that a tree is actually dying from the disease until we acquire a physical sample,” Perroy says. To build Kūkūau, he collaborated with ETH Zurich, a research university halfway across the world, which sent its original device, called the “Flying Treetop Sampler,” to Hilo. Perroy then modified it with the help of Hilo welder and machinist Russell Iyo. “How much would it cost to make this contraption … not counting the intellectual capital, which is priceless?” Perroy jokes. “Under $2,000?Unmanned aerosystems can do things that are dull, dirty and dangerous. This kind of technology can make it safer, faster, cheaper and easier to get the information we need.”

The ‘Ōhi‘a Challenge generated global interest and engagement, which has HVNP ecologist David Benitez excited. “Invasive species and fungal pathogens are not by any means unique to Hawai‘i,” he says. “Many other parts of the world are dealing with this. This challenge was a good model for developing innovative solutions to help protect our world’s forests.” Perroy’s technology addresses issues affecting both individual trees as well as entire landscapes, and it was that combination that made every one of the judges say, “Yeah! This is it!” says Benitez.

Hawai‘i’s native forests are dominated by ‘ōhi‘a, so it’s natural that any threat to their well-being would be a top priority. How the fungus spreads is still somewhat of a mystery. Boring beetles attack infected trees, and the dust they produce can be transported on the wind to infect new trees. Friday says it’s also likely the spores are spread through vehicles, equipment or soil on shoes or clothing. Moving infected logs or firewood could spread the disease as well, and there is a quarantine on ‘ōhi‘a plant parts, including wood, being transported among islands.

In heavily trafficked areas like Hawai‘i Volcanoes National Park, where approximately 30 percent of the vegetated portion of the park’s 323,431 acres is ‘ōhi‘a forest, there are boot brushing stations at key trailheads. Right now there are close to one hundred infected trees in the park’s Kahuku Unit and scattered trees elsewhere, including the summit area of Kīlauea, the main entry point into the park.

At the end of 2019, Sullivan completed his regular SDAV helicopter flight over Kalōpā State Recreation Area along the Hāmākua Coast, where ROD was detected a year ago. He shows me the progression of the infected trees on a computer monitor in the lab.

“See, dead tree there, dead tree there. It’s the strangest thing, though,” he says. “You’d think it would look like radiation spreading out from the center. But the diseased trees are like pockmarks, spread out in separate areas. There are virtually no ‘ōhi‘a left in the lowlands, so this park is very special. It is one of the most beautiful ‘ōhi‘a forests with some of the largest trees. Right now just a few trees are infected. But look at this tree here. It’s literally right next to the parking lot. So it’s not this far-removed idea of a sick tree somewhere in the forest. It’s a much more pressing, obvious disease.”

Kumu hula and lei maker Lorna Kapualiko Lim and I are huddled under one umbrella in the rain, looking up at the actual tree Sullivan showed me a few days earlier in the lab image. It’s right next to the parking lot, just as he said, completely brown, with a few tiny leaves left clinging to its decaying branches. Nearby ‘ōhi‘a lehua stand tall and unaffected, for now.

“I never noticed it before,” says Lim. “I’ve always just seen the beauty of this place.” Lim (who was named after a yellow ‘ōhi‘a lehua grove, “the budding flower that sits high atop Kohala”) has been coming to this forest for forty years. Kalōpā is still one of her favorite spots to take her dancers.“The original trees and places to gather are still here because we make sure to take care of the land,” she says.

In Hawaiian culture, ‘ōhi‘a are frequent symbols in mo‘olelo (stories), mele (songs) and oli (chants). They represent the kinolau (physical manifestations) of multiple Hawaiian deities. “At the Merrie Monarch Festival, you can see the blooms of the ‘ōhi‘a lehua in costuming and guess that the dance is probably about the volcano goddess Pele,” says Lim. “The way the ‘ōhi‘a lehua blooms, it looks like fire itself.”

We’ve spent the last hour in the park’s pavilion as Lim weaves a haku lei, worn on the head. “ROD is detrimental to the landscape, but it is also detrimental to us in hula,” she says. “There is a spiritual connection between the dancer, the mele and the adornments. They all work together to become one.” So with the ‘ōhi‘a quarantine in place, Lim realized she could not travel to neighbor island hula competitions with fresh blossoms for lei. “I had to do something,” she says. So she got creative: She dyed the taupe bark of the hau tree red using hibiscus flowers, then finely shredded the bark to resemble the delicate strands of the lehua blossom. “We can bring life to this form so that our people can still dance with the ‘ōhi‘a lehua, and we can also save our forests.”

Though building Perroy’s final drone will cost only a fraction of the ‘Ōhi‘a Challenge’s $70,000 award, the price of research and development, as well as new equipment for early detection imaging work and ongoing field operations, is high. Perroy’s data are currently being used to quickly identify suspect trees in new outbreak areas and to monitor how existing outbreaks change over time. His team has also been asked to help neighboring islands with early detection efforts through rapid deployment helicopter mapping. “This is helping us understand what to expect and how the pathogen is affected by different environmental settings,” explains Perroy. And while there is as yet no cure for a ROD-infected tree, “our monitoring data is also helping us learn about what our forests will look like in the future. If many of the ‘ōhi‘a die, what will take their place? Will new ‘ōhi‘a come back? Will there only be invasive species that fill in? So, there are longer-term questions our data can also help with.”

It will take ingenuity and perseverance to save Hawai‘i’s ‘ōhi‘a for future generations. “There’s still a lot that we don’t understand about ROD,” says Perroy. “What we’re doing is part of a much larger effort to combat this, but I’m hopeful that our contribution can be a game-changer.” HH