Ten years prior, a perplexing new illness began ravaging Hawaii’s native ‘ohi‘a forests, annihilating a crucial species that forms the backbone of the islands’ ecosystem and holds significant cultural value for the state.
Now, researchers are racing against the clock, warning that unless the spread of what has become known as Rapid ‘Ohi‘a Death (ROD) is curtailed, most of the expansive ‘ohi‘a forests on Hawaii Island could be lost within two decades.
This urgency has led teams of scientists to investigate the mechanisms of this fungal disease, aiming to equip state and federal land managers with knowledge to safeguard these precious forests.
Recent strides have been made, including the development of an innovative beetle repellent designed to deter the small pests that facilitate the disease’s transmission to ‘ohi‘a trees, along with securing a $1 million grant to explore why certain trees exhibit heightened resistance to the fungus.
Ultimately, rescuing ‘ohi‘a, a species endemic to Hawaii upon which countless other flora and fauna rely, will necessitate additional funding.
A comprehensive five-year action plan is anticipated to be released by a multi-agency working group in January. State officials estimate that executing this strategy could require as much as $8 million annually, nearly double what was previously allocated in earlier plans.
The former Rapid ?Ohi?a Death Strategic Response Plan, implemented from 2020 to 2024, requested just over $4 million annually. However, Rob Hauff, a state protection forester, noted that funding fell short by nearly $1 million during that phase.
He expressed hope that state and federal leaders will fully fund the forthcoming five-year initiative, emphasizing that such critical issues can easily be overlooked. Meanwhile, climate change is accelerating the ‘ohi‘a decline, with rising temperatures promoting the growth of invasive plants such as ginger and strawberry guava that outcompete young ‘ohi‘a trees for resources, according to researchers.
Prolonged drought conditions, attributable to climate change, further weaken the ‘ohi‘a, while increasingly severe storms result in branch breakage and exposed bark, rendering the trees more susceptible to the disease, Sarah Knox, a project coordinator at the Akaka Foundation for Tropical Forests, explained.
“We all share an acute sense of urgency to address this from every possible angle,” Knox stated. “We are exploring every approach available.”
Central to the ecosystem, the ‘ohi‘a is termed a “keystone” species in Hawaii, sustaining numerous native plants, insects, birds, and the larger ecological framework.
The trees are notably strong, with unique papery bark and twisted trunks. Their versatile leaves can be either fuzzy or smooth, and their lehua flowers bloom in various shades, though most commonly red.
Once the trees fall, Knox points out, they serve a critical role on the ground, aiding in the growth of new trees and plants just as effectively as when they stood tall.
On Hawaii Island, ‘ohi‘a can thrive in a wide range of environments, from parched lava flows to damp bogs. Their canopy is vital for capturing fresh water as cloud mist passes through, preserving moisture in the forest floor and mitigating flooding risks.
The ‘ohi‘a is also woven into traditional Hawaiian beliefs, with deep connections to deities like Pele, the goddess of fire and volcanoes, and Ku, the god of primal energy and conflict. Hula dancers have historically gathered its flowers and foliage to create lei and make offerings to Laka, goddess of hula.
The wood from ‘ohi‘a was traditionally sculpted for adorning temples, bestowing sacred significance on these structures as they became homes for the akua, or divine spirits, according to Lilikala Kame?eleihiwa, a senior professor at the University of Hawaii’s Hawai‘inuiakea School of Hawaiian Knowledge.
Even today, hula groups collect ‘ohi‘a flowers for ceremonies; however, researchers now advise against transporting them to neighboring islands to minimize the risk of disease transmission.
Rapid ‘Ohi‘a Death, induced by the fungus Ceratocystis, has already infiltrated parts of Kauai, Oahu, and Maui, though it has not yet spread alarmingly across those islands as it has on the Big Island.
Over the last decade, the disease has claimed between 1 and 2 million trees in Hawaii, according to Flint Hughes, a research ecologist with the U.S. Forest Service.
Hawaii is home to roughly 300 million ‘ohi‘a trees, but Hughes notes that ROD significantly impacts the more limited population of 17 million mature trees that primarily constitute the forests. In forest plots under surveillance, around 10% of the trees fall victim to the disease annually.
“That’s the reason for the urgency,” Hughes emphasized.
There is ongoing debate within the Hawaiian hula community over what collection practices are still acceptable given the deforestation threat, prompting wildlife officials to outline clearer guidelines, according to Kylle Roy, a forest entomologist with the U.S. Fish and Wildlife Service.
Roy is also assessing the dynamics of disease transmission at higher forest elevations, expressing that various factors could contribute to spreading ROD depending on geographic location.
She is developing a wax-like repellent that, once applied, may deceive ambrosia beetles into neglecting an ‘ohi‘a tree’s trunk, utilizing pheromones that signal the tree is already dead.
For Roy, the fight against Rapid ‘Ohi‘a Death is deeply personal, as it connects to her Native Hawaiian roots.
“The significance of ‘ohi‘a is apparent on the Big Island; it is the native forest, and everything hinges on it,” she stated. “I’ve dedicated my life to saving ‘ohi‘a.”
Roy’s repellent awaits state approval for broader use, which could be granted later this year through a Special Local Need registration, according to Greg Takeshima, acting administrator of the state Department of Agriculture’s Plant Industry.
If approved, the repellent could be put to use in ‘ohi‘a forests even as it awaits final clearance from the Environmental Protection Agency.
However, should the EPA raise concerns, application would need to pause until those issues are clarified.
During a recent field survey at Hawaii Volcanoes National Park, stark contrasts were observed between healthy forest zones and areas grappling with disease and invasive pig activity.
“Looking up, you can see the sky,” Roy remarked, indicating the barren canopy where leaves once provided shade. In contrast, healthy sections shielded by fencing showcased thick fern cover, illustrating the stark disparity.
Many afflicted areas in the national park are inundated with invasive species. To counter this, Stacey Torigoe, a National Park Service ecologist, is implementing biocontrol methods.
This includes introducing specific insects that target strawberry guava, inducing the growth of galls that inhibit the spread of that invasive plant across the forest floor.
Maintaining a healthy understory devoid of invaders is crucial for ensuring the survival of native species and the new trees.
Efforts are also underway to identify what makes certain trees more robust than others.
Researchers at Purdue University and the University of Wisconsin have received a $1.1 million grant aimed at examining the chemical defenses of ‘ohi‘a trees and assessing their susceptibilities to disease.
Their research will investigate whether trees that can store more carbohydrates possess better defenses when faced with threats.
Previous aerial surveys of infected areas have highlighted a few resilient trees amidst widespread mortality caused by ROD.
“If the trees have higher carbohydrate reserves, they may be better positioned to fend off pathogens,” Furze observed.
This research will also assist forest managers in identifying when trees are most vulnerable to the disease, guiding timely fungicide applications.
Their three-year project complements efforts that involve collecting ‘ohi‘a cuttings and seeds to cultivate in nurseries, determining which trees are genetically more resistant to the fungus.
As the ROD Resistance Program advances, experts emphasize the significance of focusing on preserving existing ‘ohi‘a trees regardless of their genetic resistance.
“Protecting our forests outweighs the need to replant once they’re gone,” Friday acknowledged. “Although knowing resistant variants is crucial, the priority should always be on safeguarding the healthy forest.”
There is a consensus among experts, including Knox and other forest managers, that erecting fences across the expansive ‘ohi‘a forests would almost entirely eliminate the threat of Rapid ‘Ohi‘a Death. These barriers would prevent pigs, goats, and other invasive hoofed animals from transmitting fungal spores between trees.
Nonetheless, the task of installing and maintaining fences across all 800,000 acres of forests in such rugged terrain is impractical.
“Fences are effective, yet costly,” Torigoe explained.
Currently, the park service has approximately 170 miles of fencing in place within the Volcanoes National Park, aimed at deterring these invasive species, according to NPS spokesperson Jessica Ferracane. The challenge of upkeep demands significant resources and attention.
Since many of the park’s nearly 72,000 acres of ‘ohi‘a forests remain vulnerable to hoofed animals, ongoing research into the disease’s spreading mechanisms is vital.
Scientists recognize that wild pigs often contribute to disease transmission by creating wounds on trees when they rub against them and further dispersing spores by uprooting infected soil.
Understanding the interplay of beetles, pigs, climate change, and tree health in ROD transmission remains an area of active investigation, imperative for effective management.
“We possess a solid base knowledge. Now, we’re focusing on how various factors differ across landscapes and influence tree mortality,” Hughes noted.
Knox is particularly interested in discerning what attracts wild pigs to specific trees, employing cameras to study their behavior. She is also examining which specific wounds facilitate disease spread.
“We’re enhancing our arsenal of strategies as quickly as possible,” Knox concluded. “Given limited manpower, it’s vital to ensure we’re directing our efforts effectively.”
Recent summer surveys suggest that the trees’ deeper fine roots may also be at risk of infection, a pressing concern given the destructive behaviors of ungulates.
“If this is accurate, ungulates could severely threaten our forests through constant wounding of the roots,” Hughes warned.
According to Kame’eleihiwa, in Hawaiian tradition, the ‘ohi‘a trees symbolize the physical presence of Pele, encompassing all Hawaiian ancestry.
“The passing of each tree feels akin to losing a family member, and it’s profoundly painful for us,” she expressed. “These sacred trees house a spirit of Ku, bridging the earth and sky,” she added. “They serve as a sanctuary for these vital forces.”
“It would be an immense gift if scientists could discern how to halt the disease,” Kame‘eleihiwa shared.