They’ve been a known problem among Hawaii ecologists and arborists for decades, but most Hawaii residents were introduced to Falcataria moluccana, commonly called albizia, with this month’s destruction from Tropical Storm Iselle. The term "invasive species" usually doesn’t conjure images of a leafy, wide-canopied grove, but that’s what albizia is.
That’s because this fast-growing tree is brittle and top-heavy, and its graceful-looking umbrella of branches topples readily in high winds, as Puna, hardest hit by Iselle, discovered. The misfortune of those residents, some of whom lost property to felled trees and many of whom found roadways blocked and power lines downed, has rightly focused attention on the need for a comprehensive control of the infestation.
A bill to allot $5 million to remove albizia trees along key East Hawaii roadways died in legislative committee in the past session, but funding for a similar project deserves full consideration when lawmakers reconvene in January. Experts approached in recent weeks have made a compelling argument that this problem needs to be tackled.
Eradication is an unrealistic goal, because albizia trees have been growing here for nearly a century. Springer Kaye, Big Island Invasive Species Committee manager, said the Indonesian native was introduced to protect denuded areas of the watershed. In East Hawaii alone, the aggregate area overtaken by albizia has been estimated at 6,000 acres, she said.
Some targeted removal work has been underway for a few years already, especially along highways and near utility lines. Flint Hughes, an ecologist with the Institute of Pacific Islands Forestry, said it would be cost-effective to also remove the ones adjacent to them, to keep the cleared area from being quickly reseeded.
The planning should begin now for a strategy. One way to prevent regrowth, Hughes said, is to allow other plants to fill the void, because albizia does not sprout when shaded.
An effective method of killing the trees is to inject small amounts of a specialized herbicide through cuts in the trunk, roughly a milliliter per tree. The scientists said the compound, known commercially as Milestone, breaks down rapidly on-site through bacterial action, and added that there should be no residual problem.
But it hasn’t been cleared for residential use, they said, so property owners should consult an arborist to decide how to handle it.
Even those with approvals and expertise must proceed cautiously. For example, any notion of introducing other species as biological controls for albizia must be rigorously vetted and tested, to prevent yet another unintended consequence. Hawaii’s native species are under enough stress from alien competition.
Although not strong enough to yield structural lumber, albizia cuttings could have an application. A new venture, Bio-Tork Hawaii, just got legislative approval to develop uses for agricultural waste, including albizia as a feed stock for a fungus that produces biofuel. In more commonplace adaptations, the lightweight wood is good for craft items and furniture.
The hope is that something practical can come from the albizia, brought to Hawaii with good intentions, but not enough forethought.
Ira Zunin, M.D., M.P.H., M.B.A., is medical director of Manakai o Malama Integrative Healthcare Group and Rehabilitation Center and CEO of Global Advisory Services Inc. Please submit your questions to info@manakaiomalama.com.
