Control spread of invasive albizia

An albizia is easy to spot in Hawaii’s lineup of lush foliage. Fitted with a feathery, top-heavy canopy, it’s typically the tallest tree species dotting various roadways and ravines in the islands. They’re beautiful. But, alas, they’re also a dangerously brittle and a rapidly spreading invasive species.

The trouble the tree can cause was spotlighted by Tropical Storm Iselle in 2014. Hundreds of knocked-down albizias are blamed for tens of millions of dollars in damage — crushed rooftops, blocked roads and downed power lines on Hawaii island, leaving 30,000 people without electricity, some for weeks.

Stands of albizia can be found on all of the main islands except Molokai, Niihau and Kahoolawe. While eradication is out of the question at this time, the state must push forward management efforts aimed at minimizing potential risks.

The Hawaii Invasive Species Council recently released a report that maps a strategic plan for controlling the albizia problem — for the first time — on a statewide scale. In the works is an economic analysis that will put a price tag on executing the plan. Success will likely hinge on a long-term financial commitment as well as improved regulations tied to planting and real estate disclosure.

In the aftermath of the Iselle disaster, the Big Island Invasive Species Committee teamed up with the state Department of Transportation, Hawaii County Civil Defense, Hawaii Electric Light Co., U.S. Forest Service and other organizations to weed out albizia trouble spots in the Hilo area. Now about midway through a five-year plan, which was estimated to cost $26 million, all projects have so far come in under budget. A similar team should assemble on Oahu, which now has some 20,000 infested acres.

Right now, cost is tethered to location. Trees in undeveloped areas can be killed in place with herbicide for less than a dollar, but removal of those close to people and property can cost as much as $10,000 per tree.

In an extreme case, Lyon Arboretum in Manoa Valley inked a $980,000 contract to have 12 large albizia trees — ranging in height from 130 feet to 205 feet — removed to protect endangered, rare and irreplaceable plants below them. The Papua New Guinea native presents a death threat for some Hawaii-native trees as its broad canopy blocks sunlight and its shallow roots quickly drink available rainfall, essentially starving others, like the ohia.

Some removal costs could be trimmed if scientists are able to confirm that a bio-control agent, such as an insect attacking the tree’s ability to reproduce, can get the job done here without touching off harmful side effects. In the meantime, though, with no natural enemies here, albizia trees are multiplying at an alarming pace.

The species has the ability to “fix” nitrogen from the air, which enables speedy growth — up to 15 feet in its first year. But because the trees grow so fast, the wood it develops is weak. Also, wind-dispersed seeds can take root quickly. For instance, in the Rainbow Falls area of Hilo, the albizia population grew to 35 acres from 10 acres in just 15 years.

Since created by the Legislature 15 years ago, the Invasive Species Council has frequently been underfunded. It’s heartening that state lawmakers now seem poised to change that.

Senate Bill 2399 would restructure the council — an interdepartmental collaboration that guides policy direction and planning among state departments, federal agencies and other initiatives — as the “Invasive Species Authority.” The authority would be attached to the Agriculture Department and have more decision-making clout and a defined operating budget — unlike the council, which operates year-to-year on grant money.

Such a switch, which appears to have broad support at the state Capitol, could spur much-needed speed and efficiency in tackling growing infestations of albizia trees as well as other invasive species afflictions, ranging from little fire ants to the coffee berry borer.