For more than 1,000 years, Hawaiians sought sources of wood in their lowland rainforests. Acacia koa was the wood of choice for canoes, chipped and cut to form with various types of the basaltic stone adze.
Today's koa, with its signature curly grain and varied coloration that often create a three-dimensional sheen, is prized for furniture making and crafts. It is found on all the main Hawaiian Islands, including throughout the Ko'olau Range on O'ahu.
Unfortunately, koa's vitality is challenged by invasive plants such as strawberry guava, mule's foot fern, maile pilau and bushy beardgrass. The endemic evergreen hardwood is also susceptible to koa wilt disease (Fusarium oxysporum), a fungus whose origin is unknown and which causes crown and shoot dieback, root rot, bark and vascular system ruptures, branch discoloration and overall stunting. Even so, this favored species of tree is not without its champions.
Almost 20 years ago, nine kupuna and their families began camping one weekend a month in Halawa Valley, working to keep bushy beardgrass and other pest plants from competing with the koa trees growing there. As volunteers added to their numbers, the group worked to protect ancient Hawaiian cultural sites, clean the forest and restore it with native plants.
"We've been trying to take care of the valley for long time," says 70-year-old Sweets Matthews of Na Kupuna A Me Na Kako'o O Halawa, Hawaiian elders and volunteers who have become caretakers of the valley. "It's important to show how our ancestors lived, how they kept the forest, the streams and the ocean clean because they used everything."
Above the sweeping valley floor where the group labors spans the H-3 Freeway, stretching more than 15 miles from North Halawa Valley, through the Ko'olau Range, to Ha'iku Valley on the windward side. Interstate H-3, connecting leeward and windward O'ahu, was the largest project ever undertaken by the Hawai'i Department of Transportation (HDOT) and took years to complete.
Five years ago, Matthews gave HDOT Landscape Architect Chris Dacus and the O'ahu Invasive Species Committee (OISC) a tour of the area. The original construction staging area where equipment and material had once been stored had become a large stand of koa trees, regenerating on their own. There were approximately 50 koa trees standing 30 feet high, but at the mercy of encroaching pest plants, mostly bushy beardgrass, maile pilau and strawberry guava. Dacus launched a restoration project to clean up a four-acre site at the staging area.
"The common invasive species that plague all forests in the Ko'olaus also plague Halawa Valley," explains OISC Coordinator Rachel Neville. "Strawberry guava, mule's foot fern, Australian tree fern, albizia and bushy beardgrass all contribute in their own way to the destruction of the Hawaiian rainforest. We hope that removal of fire threats, like bushy beardgrass, also removes fire threats to the restoration site."
Hawaiian plant specialists Rick Barboza and Matt Schirman of Hui Ku Maoli Ola, were brought onboard to clear the area, collect koa seeds and plant 1,100 koa saplings that today stand two feet tall in the open areas and between existing trees. In the general vicinity, the hui also found fragrant native white hibiscus, koki'o ke'oke'o, growing among the brush. Cuttings were taken, nursery grown, and about 200 saplings were planted at the staging site.
"Being there, you really get a feeling that this is a very special place," Dacus recalls. "It's the only opportunity to drive through a koa 'ohi'a forest on the Island of O'ahu. The former staging area is now 100 percent koa. Now the work will be to maintain it, to ensure it only improves."
Add to this the work of Nick Dudley, a forester at the Hawaii Agriculture Research Center who heads the state's only koa disease screening program in collaboration with the U.S. Forest Service and the State's Division of Forestry and Wildlife. With the overall goal to establish healthy koa plantings, maintain high rates of growth and ensure high quality timber, Dudley did a preliminary seed collection from koa trees in Halawa Valley. By inoculating them with the pathogen that causes koa wilt, Dudley has identified individual trees with a higher potential for survival and has them ready for planting at the restoration site.
"Koa is one of the most important endemic Hawaiian timber species from an ecological perspective," Dudley says. "No other native Hawaiian wood is as abundant or as valuable."
According to Dudley, the native low elevation koa 'ohi'a forest in Halawa Valley is one of the most intact on O'ahu. He believes efforts toward koa restoration make sense, especially if continued screening work is done, so additional wilt resistant koa can be deployed. For the kupuna caretakers, making sense of restoration may take on a more esoteric meaning.
"We walk in the footsteps of our kupuna," says Matthews. "We will always be there to help keep the forest healthy and be there for each other."