There is a disturbance in the forest.
The native Hawaiian ʻōhiʻa (Metrosideros polymorpha) is the most abundant tree in the Hawaiian Islands, comprising about 62 percent of the total forest area.
The name Metrosideros is derived from Greek metra, heartwood, and sideron, iron, in reference to the hard wood of the genus. Known as ‘Ōhi‘a Lehua, the species is found on all major islands and in a variety of habitats. (Friday and Herbert)
‘Ōhi‘a lehua is typically the dominant tree where it grows. Although the species is little used commercially, it is invaluable from the standpoint of watershed protection, esthetics, and as the only or major habitat for several species of forest birds, some of which are currently listed as threatened or endangered.
ʻŌhiʻa is a slow-growing, endemic evergreen species capable of reaching 75- to 90-feet in height and about 3-feet in diameter. It is highly variable in form, however, and on exposed ridges, shallow soils, or poorly drained sites it may grow as a small erect or prostrate shrub.
Its trunk may range in form from straight to twisted and crooked. Because the species can germinate on the trunks of tree ferns and put out numerous roots that reach the ground, it may also have a lower trunk consisting of compact, stilt-like roots.
The hard, dark reddish wood of ʻōhiʻa lehua was used in house and canoe construction and in making images (ki‘i), poi boards, weapons, tool handles, kapa beaters (especially the rounded hohoa beater), and as superior quality firewood.
ʻŌhiʻa lehua, though of a very nice color, cracks or ‘checks’ too easily to be useful for calabash making. The foliage served religious purposes and young leaf buds were used medicinally. The flowers and leaf buds (liko lehua) were used in making lei.
To Hawaiians of old, the gods were everywhere, not only as intangible presences but also in their myriad transformation forms (kinolau) and in sacred images (ki‘i). Most of the large images were carved from wood of the ʻōhiʻa lehua, an endemic species that is regarded as a kinolau of the gods Kane and Kū.
The materials used in large part depended on the resources available nearby and whether a hale was for aliʻi or makaʻāinana, but in either case, hardwoods were selected for the ridgepoles, posts, rafters, and thatching poles. Hardwoods grew abundantly in Hawaiian forests, in terms of both number of species and the count of hardwoods as a whole.
ʻŌhiʻa lehua grew on all the major islands and was widely used in housebuilding. Canoe decking, spreaders, and seats were commonly made of ʻōhiʻa lehua, as well as for the gunwales.
ʻŌhiʻa lehua was one of the five primary plants represented at the hula altar (ʻōhiʻa lehua, halapepe, ‘ie‘ie, maile and palapalai.) The hālau hula, a structure consecrated to the goddess Laka, was reserved for use by dancers and trainees and held a vital place in the life of an ahupua‘a.
Inside a hālau hula was an altar (kuahu), on which lay a block of wood of the endemic lama, a tree whose name translates as “light” or “lamp” and carried the figurative meaning of “enlightenment.” Swathed in yellow kapa and scented with ‘olena, this piece of wood represented Laka, goddess of hula, sister and wife of Lono.
A number of other deities were also represented on the altar by plants: ʻōhiʻa lehua for the god Kukaʻōhiʻa Laka (named for a legendary ʻōhiʻa lehua tree that had a red flower on an eastern branch and a white one on a western branch) …
… halapepe (Pleomele aurea) for the goddess Kapo; ‘ie‘ie for the demigoddess Lauka‘ie‘ie; maile representirig the four Maile sisters, legendary sponsors of hula; and palapalai fern, symbolic of Hi‘iaka, sister of the volcano goddess Pele and the benefactor of all hula dancers.
Native Hawaiians consider the tree and its forests as sacred to Pele, the volcano goddess, and to Laka, the goddess of hula. ʻŌhiʻa lehua blossoms, buds and leaves were important elements in lei of both wili and haku types.
ʻŌhiʻa is the first tree species to establish on most new lava flows. As the entire portion of eastern Hawaii Island is a volcanic area, lava flows occasionally cover areas of forested land. Thus, while some forests are covered with lava, other forested areas serve as ‘seed banks’ and help to bring growth back life to the lava-impacted area.
There is a disturbance in the forest. Rapid ʻŌhiʻa Death is posing the greatest threat to Hawai‘i’s native forests. A newly identified disease has killed large numbers of mature ʻōhiʻa trees in forests and residential areas of the Puna, Hilo and Kona Districts of Hawaiʻi Island.
Pathogenicity tests conducted by the USDA Agriculture Research Service have determined that the causal agent of the disease is the vascular wilt fungus; although a different strain, this fungus has been in Hawaiʻi as a pathogen of sweet potato for decades.
It is not yet known whether this widespread occurrence of ʻōhiʻa mortality results from an introduction of an exotic strain of the fungus or whether this constitutes a new host of an existing strain. This disease has the potential to kill ʻōhiʻa trees statewide.
The disease affects non-contiguous forest stands ranging from 1 to 100 acres. As of 2014, approximately 6,000 acres from Kalapana to Hilo on Hawaiʻi Island had been affected with stand showing greater than 50% mortality. The disease has not yet been reported on any of the other Hawaiian Islands.
Crowns of affected trees turn yellowish and subsequently brown within days to weeks; dead leaves typically remain on branches for some time. On occasion, leaves of single branches or limbs of trees turn brown before the rest of the crown of becomes brown.
Recent investigation indicates that the pathogen progresses up the stem of the tree. Trees within a given stand appear to die in a haphazard pattern; the disease does not appear to radiate out from already infected or dead trees. Within two to three years nearly 100% of trees in a stand succumb to the disease.
The fungus manifests itself as dark, nearly black, staining in the sapwood along the outer margin of trunks of affected trees. The stain is often radially distributed through the wood.
Currently, there is no effective treatment to protect ʻōhiʻa trees from becoming infected or cure trees that exhibit symptoms of the disease. To reduce the spread, people should not transport parts of affected ʻōhiʻa trees to other areas. The pathogen may remain viable for over a year in dead wood.
UH scientists are working to protect and preserve this keystone tree in Hawaiʻi’s native forest. The Seed Conservation Laboratory at UH Mānoa’s Lyon Arboretum launched a campaign to collect and bank ʻōhiʻa seeds. They will collect and preserve ʻōhiʻa seeds from all islands for future forest restoration, after the threat of Rapid ʻŌhiʻa Death has passed.
I was happy to see the proactive actions taken by the Hawai‘i Department of Agriculture; on a recent trip to the Big Island, they handed out notices to travelers on Hawaiian Air, reminding them not to take ‘ōhi‘a off the island. (Lots of information here is from Abbott and CTAHR.)