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Residents band together to fight invasive albizia trees

Updated: 
December 10, 2013 - 10:14pm

About 20 people converged at the center of the Keauohana Forest Reserve at the intersection of Highway 130 and Upper Puna Road early Tuesday morning.

Armed with GPS units, hatchets and bottles of poison, they banded together to wage war against a fearsome enemy — one that seems intent on swallowing up Hawaii Island’s native forests and wreaking havoc upon homes and roadways.

The invasive species Falcataria moluccana, also known as the albizia tree, is rapidly spreading throughout Puna and other parts of Hawaii Island. The tree can grow quickly — about 15 feet per year — but is also very brittle and has a weak root system, posing a safety risk to people and property with its tendency to snap and drop large branches after even minor storms.

The tree can grow extremely tall, and lowland forests are experiencing a disturbing trend where stands of albizia advance and blot out the sun above the smaller native trees, such as ohia, effectively starving them to death.

Tuesday’s effort, organized by the Big Island Invasive Species Committee, was the result of a desire by the nearby residents of Black Sands Subdivision to try to control the spread of the albizia trees in the neighboring forest before their homes were endangered, said BIISC Manager Springer Kaye.

A combination of state, county and community groups came together to organize an albizia control demonstration to show area residents how to safely and easily do their part to prevent the trees from spreading into their neighborhoods.

The demonstration centered on methods for dealing with “nonhazard” trees, she said.

“Nonhazard trees are located where they can safely fall down without causing any damage,” she said. “Hazard trees require professional removal by a certified arborist.”

Participants were taught how to “hack and squirt,” by cutting angled notches every 6 inches around the circumference of the trees and then squirting between 0.5 and 1 milliliter of Milestone Specialty Herbicide into the cut.

Within two weeks, the tree will drop all of its leaves and appear dead. After about two years, it will have dried out to the point where it will be lighter and crumble away, posing less of a risk than a heavy tree that might snap and fall.

The procedure is a relatively cheap one, costing about $3.50 per tree to cover equipment and materials, Kaye said. In July, the state Legislature approved $35,000 to fund the demonstration project. Additional control funding is being supplied by the Hawaii Invasive Species Council.

State Sen. Russell Ruderman, D-Puna, was among those who showed up Tuesday to support the effort to control albizia. In May, he introduced Senate Resolution 41, calling for the state Invasive Species Council to develop a statewide strategic management plan for the invasive trees, beginning with Hawaii Island.

“This is a problem affecting all of us,” he said. “But if we’re going to confront it, let’s do it smartly.”

Among those members of BIISC who are working to generate information so the public can get a better handle on the albizia situation on Hawaii Island is Julie Gaertner. As a remote sensing and GIS analyst at the University of Hawaii Research Corporation, she is currently studying satellite imagery to try to obtain an accurate accounting of how big the albizia problem is in Puna.

Using computer software, she analyzes satellite images of large expanses of plants and trees and identifies them based on the spectrum of light they reflect. It’s a relatively accurate method, she said, and one which may allow her to obtain a count of albizias in any area, as well as determine how quickly they spread to new areas.

“Right now, all I have is a rough, rough estimate of how many there are, but I expect to have the mapping done soon,” she said.

Another albizia control demonstration will be held from 9 a.m. to noon Saturday at the intersection of Upper Puna Road and Highway 130. Participants are asked to bring sturdy shoes and pants, a long-sleeve shirt, hat, bug spray and sunscreen. Refreshments are provided.

BIISC is a voluntary partnership of private citizens, community organizations, businesses, land owners and government agencies who aim to address invasive species issues on Hawaii Island. For more information on the albizia control project or other BIISC business, call 933-3340.

Email Colin M. Stewart at cstewart@hawaiitribune-herald.com.