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WAIMEA, Kauai — Wielding a fruit picker, Seana Walsh cuts a branch from an old ohia lehua tree and thousands of golden seeds rain down. With gold flecks in her hair and on her shirt, she draws the branch close and peers into its capsules, where thousands more seeds like tiny dust particles appear ready to jump out.
Walsh, a conservation biologist, struggles to prevent more seeds from floating off in the wind. She is hiking Kauai’s wet mesic forest along the Kalalau Valley rim to collect ohia seeds — not disperse them.
“I’ve heard that if you pick the ohia lehua it will start to rain,” Walsh says, shaking seeds into a brown paper bag as silvery clouds hang heavy above her head.
Walsh and her fellow scientists are collecting seeds as part of their search for ways to reverse the spread of a disease that has wiped out vast numbers of ohia trees on the Big Island — and now imperils Kauai’s forests.
It’s hard to overstate the importance of ohia to Hawaii’s forests and its culture.
Ohia is the most dominant native tree in Kauai’s wet mesic forest. Its leaves and spiky, red flowers fill the forest canopy, protecting smaller native trees from the sun’s scorch and providing nectar to rare and endangered forest birds found nowhere else on earth.
The Kamehameha butterfly relies on the tree. Honeycreepers nest in its branches. Hula dancers wreathe their heads, ankles, wrists and necks with the ohia’s iconic buds and blossoms.
The tree plays an essential role in recharging the aquifer, boosting human access to irrigation and drinking water. The first plant to grow on a new lava field, ohia long ago secured a sacred place in Hawaiian chants and legends.
Although scientists didn’t know the cause at the time, reports of healthy ohia trees swiftly succumbing to early death sprung up on the Big Island in 2010. By 2015, plant pathologists had pinned the cause of these mysterious mortalities on a new disease named rapid ohia death.
The disease has two distinct pathogens: One that works slowly to sever the tree’s supply of water and a more aggressive fungus that makes the kill quick.
Today, rapid ohia death is present in approximately 135,000 acres of Big Island ohia forest. On most of that acreage, the disease has penetrated only a few trees per acre. But there are hundreds of acres with a mortality rate of 70 percent or higher. All told, hundreds of thousands of ohia trees have died across the island.
In May, rapid ohia death was detected on Kauai, marking the first confirmed presence of the disease outside the Big Island. The tree grows throughout the Pacific, and Hawaii researchers are partnering with scientists in places like Tahiti and New Zealand to restrain the disease’s spread.
“A lot can change when you start to lose native trees that are hundreds of years old.” — Lisa Keith, plant pathologist
Walsh, who is employed at the National Tropical Botanical Garden on Kauai, is one of more than 100 people across Hawaii working to contain rapid ohia death and prevent its creep onto new acreage.
Specifically, her seed collection contributions could provide scientists with the means to plant ohia in wild areas for restoration. This could be important if the small infected forest areas on the map grow broader and unmanageable.
Her work is bolstered by a $59,000 state tourism grant awarded to NTBG by the Hawaii Legislature. The money funds activities such as seed collection and storage, community education and helicopter flights that help scientists scout out diseased trees in hard-to-access valleys and cliff sides.
Despite the risk of losing vast amounts of ohia forest, Walsh has hope that science will outsmart the disease and find a way to stop it.
“We’re thinking maybe it’s still possible to contain it,” Walsh says. “Like, fell the trees, tarp them and just get rid of it, basically, before the disease spreads. What happened on the Big Island won’t necessarily happen here.”
A call from a pig hunter brought out the scientists who looked under the bark of the tree. There it was: a black stain radiating through the sapwood in a starburst shape — the telltale sign of this disease.
The staining inside the tree, located in Moloaa Forest Reserve, confirmed that a deadly fungus had traveled across the archipelago from the Big Island to the Garden Isle.
Six months later, the disease was confirmed on Kauai in two more locations — in the Lihue-Kaloa Forest Reserve and on private land in Halelea Moku.
The trees in these three areas are infected with Ceratocystis huliohia, the less virulent of two pathogens that cause rapid ohia death. This version of the pathogen causes a canker disease beneath the bark and works slowly to bring about the tree’s death.
A few days before Christmas, more bad news: the pathogen’s more bellicose form was detected on land owned by the Department of Hawaiian Home Lands behind Kalalea Mountain.
Once an ohia tree exhibits symptoms of Ceratocystis lukuohia, it can die in a matter of weeks. The disease spreads through the tree’s vascular system, cutting off its supply of water. There’s no stopping it.
“We cannot just depend on scientists.” — Kehaulani Kekua, kumu hula
On Kauai, more aerial surveys are needed to determine how widespread the rapid ohia death has become and whether it can be contained to the smattering of places where it exists today.
If the disease becomes pervasive, it’s possible that some of Kauai’s ohia forests could begin to look like those in Hilo and Puna, where the skeletons of deceased trees flank miles of highway.
Rapid ohia death enters the tree through a wound, which might be created by branches rubbing in the wind, a scratch from a feral animal, the knick of a tractor or the work of wood-boring beetles.
From the entry point, the fungus radiates through the tree, staining the sapwood hidden under the bark. Within weeks, the tree reaches a tipping point and displays its first external symptoms: the entire canopy of leaves wilt and turn brown. By then, it’s too late. No intervention will work.
“It’s almost like a heart attack,” explained J.B. Friday, a Big Island extension forester at the University of Hawaii Manoa. “You might not see the plaque building up, and then all of a sudden — bam.”
In addition to helicopter surveys to find sick trees, scientists on the Big Island, collaborating with researchers in Florida, have trained a dog to sniff out the smell of rapid ohia death that hides in the sapwood where humans can’t yet see it.
Whether by dog or by helicopter, earlier detection could help scientists halt the disease’s spread.
Another seed of hope: Some ohia varieties show signs of resistance to rapid ohia death.
“On Kauai, we need more information to see if the disease can be contained,” Friday said. “On the Big Island, it is a management issue now. It’s not something that we’re going to get rid of. We have a lot of invasive species, and this is another one that we’ll have to deal with from here on out.”
When the ohia canopy disappears, forests become overrun with weeds — strawberry guava, maile pilau, invasive grasses — that smother other important native trees. Native forest birds like apapane and iiwi lose a food source. Snails and insects lose a home. The watershed loses the tree that’s best equipped to funnel rainfall into the earth after a storm.
“I think many people, even people living in Hawaii, don’t understand how important the ohia tree is and what losing it could mean,” said Lisa Keith, a plant pathologist at the Big Island’s Daniel K. Inouye Pacific Basin Agricultural Research Center.
Like a doctor for trees, Keith has spent nearly two decades trying to diagnose and reverse the spread of a wide array of plant disease.
So it means something that she ranks rapid ohia death as the most potentially disastrous pathogen she’s ever studied — not only here in Hawaii, but worldwide.
“It’s a people issue with drinking water and it’s an agricultural issue with irrigation water,” she says. “A lot can change when you start to lose native trees that are hundreds of years old.”
Kauai kumu hula Kehaulani Kekua and members of her hula school, Halau Palaihiwa O Kaipuwai, no longer collect ohia blossoms. The red-bursting flower is now strikingly absent from their lei and hula shrine.
“For me, and in our hula tradition, we recognize the ohia lehua as the body form of gods themselves,” Kekua explained. “So it is of huge concern and a great sense of urgency when our deities are inflicted with diseases, such as rapid ohia death, because we see before our eyes the body forms of our deities dying.”
For centuries, the brilliant ohia flower has been regarded as a manifestation of Hawaiian gods and goddesses important to hula. Breaking the tradition of collecting the blossom, Kekua said, is a painful but necessary revision.
“I understand my relationship with the forest is way too sacred and special for me to take the risk of contributing to the mass destruction of ohia lehua,” she said. “I could not live with myself.”
Kekua now employs the power of Hawaiian prayer and chant as a spiritual force to protect ohia trees, and the deities represented in them.
“I believe it really will take a larger community of people to remedy this situation,” Kekua said. “Not just cultural practitioners and native Hawaiians, but everyone who makes their home in Hawaii. We all have a responsibility to the natural resources in a very Hawaiian way.”
She added: “We cannot just depend on scientists.”
Kekua recalls a favorite legend. It is the story of the goddess Pele, whose primary responsibility is to harness lava flows to create new land, and her younger sister Hiiaka, who lives in the forest tall with ohia lehua.
In this tale, the sisters are in the Big Island’s lower Puna district — now a hotbed for rapid ohia death — when Pele decides to send Hiiaka to Kauai. She asks her little sister to retrieve the handsome Lohiau, who has become the object of Pele’s affection.
Hiiaka agrees to the mission on a condition: Pele must look after Hiiaka’s beloved ohia trees.
The journey takes Hiiaka far longer than Pele anticipated. Pele grows impatient. So she sends her lava flows down the volcano to destroy Hiiaka’s ohia forest. Hiiaka returns with her sister’s task completed. But her ohia grove is already burned to a crisp.
This legend was at the forefront of Kekua’s mind when lava erupting from Kilauea volcano terrorized lower Puna last summer.
Although the lava brought horrific losses to homeowners, it gave the disease-plagued ohia tree a ray of hope.
When ohia trees die off, invasive species rush in to fill the forest in their place. Ohia does not have room to grow there again.
But on the fresh lava fields in the Lower East Rift Zone, many new ohia trees are likely to take root. One of the only tree species sturdy enough to sprout life on such barren earth is the ohia lehua.
“I sort of see it as Pele trying to make it up to her sister,” Kekua said.
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