ʻōhiʻa tree in bloom in Hawaii Volcanoes National Park
Photo: Ken Bosma

Over the last several years, a deadly fungal disease has killed hundreds of thousands of native Hawaiian ʻōhiʻa trees. Before now, the disease—Rapid ʻŌhiʻa Death—was limited to Hawaiʻi Island. But the disease-causing fungus has now been found on the island of Kauaʻi. And that’s a big problem, considering that ʻōhiʻa is arguably the most important tree in the archipelago’s sensitive island ecosystems and traditional Hawaiian culture.

ʻŌhiʻa (Metrosideros polymorpha) is a striking tree—gnarled, with small, plentiful leaves and a brilliantly colorful display of red to yellow blossoms that adorn the plant like firework bursts frozen in place. The tree is native to all the major Hawaiian islands (and nowhere else on Earth) where it can grow as everything from a low shrub to a towering rainforest giant.

The fungal scourge started with a handful of trees in 2010, and has now spread out to most parts of the Big Island. The culprits, Ceratocystis lukuohia (“destroyer of ʻōhiʻa) and Ceratocystis huliohia, invade the trees and grow in the wood, causing rapid wilting and browning of leaves, and often death.

According to J.B. Friday, an extension forester with the University of Hawaiʻi about 135,000 acres of forest are currently affected, representing about a quarter of the island’s forests. With the detection of one of the pathogens in dead trees in a forest preserve on Kauaʻi in January, there are fears that the same carnage will soon be visited there as well.

This continued spread of Rapid ʻŌhiʻa Death is a huge deal in Hawaiʻi because ʻōhiʻa isn’t just some native tree.

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“It’s a dominant, keystone species in Hawaiʻi,” Sam ʻOhu Gon III, a senior science and cultural advisor for the Nature Conservancy of Hawaiʻi and Hawaiian cultural practitioner, told Earther.

ʻŌhiʻa produces the main canopy in many of the islands’ forests, and grows over a wide range of rainfall regimes and elevations. Gon also notes that the tree is particularly important for the percolation of groundwater and the health of watersheds. And many of the islands’ native forest birds—the majority of which are threatened—rely on ʻōhiʻa nectar for food.

‘Ōhiʻa colonizes a more-than thirty year old pahoehoe lava flow from Kilauea at Kalapana, Hawaii.
Photo: Broken Inaglory

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ʻŌhiʻa also holds an unparalleled importance in traditional Hawaiian culture.

“One of the ways you can recognize the significance of a plant is to look in a variety of traditional works, chants, and stories, and search for the names of plants,” Gon said. “When you do that, you find that ʻōhiʻa is pretty much the most often mentioned plant. It’s not just ‘a tree’ in Hawaiian forests. It is probably the single most culturally significant tree in Hawaiʻi.”

The tree has a symbolic, “cosmogonic” significance—a connection to the whole worldview of the Native Hawaiian people, especially in regards to the ancient view of the akua (gods). Ōhiʻa’s symbolic prominence is inherently tied to its widespread presence in the islands, says Gon.

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“Forests in general, especially upland forests where ʻōhiʻa holds sway, are considered the wao akua—the realm of the gods—so upright trees are considered the physical manifestation (kinolau) of the gods,” Gon told Earther. “The yellow, orange, and red flowers evoke the fires of Pele [the goddess of fire and volcanoes], so the lehua [blossoms] are a major symbol of that goddess.”

He added that the tree is one of the first to come up on fresh lava after an eruption, strengthening its connection with the goddess Pele.

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The foliage and flowers of the tree have also been of paramount importance to the teaching and practice of hula (a traditional Hawaiian dance and storytelling form) and are one of the offerings one can make at the kuahu (altar) to sanctify the learning of hula.

Sadly, the spread of Rapid ʻŌhiʻa Death has already impacted the cultural uses of the tree. Since 2016, the Merrie Monarch Festival—hula’s most prestigious contest—has held a voluntary moratorium on the use of ʻōhiʻa lehua to minimize the dispersal of the fungus. The Hawaii Department of Agriculture has also taken action, educating the public on the disease and how it spreads, and instituting a quarantine of ʻōhiʻa products leaving the Island.

It’s unknown how the disease ended up on Kauaʻi, says Friday, or if it’s been there all along. For now, the plan is to assess how far the outbreak extends, as sampling has only occurred in one location, but trees nearby are showing symptoms.

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‘Ōhi‘a tree infected with Rapid ‘Ōhi‘a Death fungus
Photo: J.B. Friday

Despite this, and the tracts of ailing trees on the Big Island, Gon is optimistic about the future of the species, as even the hardest hit forests contain living, apparently healthy trees that may seed the next generation.

But he warns that even if the tree doesn’t go extinct, the effects of even temporary decline could be harsh for the islands.

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ʻŌhiʻa is a slow growing tree, so we’re talking about a decades or centuries-long process of recovery,” he explains. “If we get complacent and allow it to spread to all of the islands, in that time we’ll have damage to our watershed resources, to our cultural resources, and it will be a very sad thing.”

Jake Buehler is a science writer living on Washington’s Olympic Peninsula with an adoration for the Tree of Life’s weird, wild, and unsung—follow him on Twitter or at his blog.