Albizia: Enemy No. 1? Troublesome trees made Iselle’s impact much worse


Big Island forestry and invasive species experts have been warning for years that albizia trees are a major threat to residents’ safety and property.

Now, after seeing the devastation wrought by falling trees in the wake of Tropical Storm Iselle, they say they have irrefutable proof.

“I’d say that well over 90 percent of the trees that did damage in the storm were albizia,” said Springer Kaye, manager of the Big Island Invasive Species Committee. “I think, now, we’ve firmly established that albizias are a threat. It’s very clear to everybody just how dangerous these trees are.”

Now, she said, it’s time to get serious about controlling the invasive trees, which can grow up to an inch in height a day and are notoriously brittle and unstable in high wind.

Albizias benefit from a natural advantage over native trees — a symbiotic relationship with nitrogen-fixing bacteria living within their roots. This gives albizia the nutrients they need to thrive in harsher soils that may impede the growth of other plants, allowing them to spread and grow rapidly, towering over and crowding out native species.

“It’s a mess out there (in Puna),” Flint Hughes, a research ecologist with the Institute of Pacific Islands Forestry, said on Tuesday. “I think we just had what it’s gonna take (to get county, state or federal funding for control efforts). We should be talking about what we need to do in the short term and the longer term, so we don’t experience this again — or even over and over again.”

During the past year, Kaye and Hughes have worked with county, state and community partners on a pilot program within the Keau‘ohana State Forest Reserve and Black Sands Subdivision that was designed to model how the trees may be controlled. The program was funded through legislation introduced by state Sen. Russell Ruderman.

Speaking about the destruction caused by falling albizias, Ruderman said Monday it was “kind of a miracle” that no one was killed.

“Thousands of trees fell down, so that’s great that no one was killed, as far as we know. … I’m very concerned about them (albizia trees). The problem is even bigger than we thought,” he said. “It was a nuisance and an eyesore before. Now everybody sees it as a disaster waiting to happen.”

At a cost of about $2 per tree, workers for the pilot program have cut trees with machetes and introduced the poison Milestone — an herbicide manufactured by Dow AgroSciences.

The results, Kaye said, have been encouraging. Once the poison has had a chance to take effect, the trees first drop their leaves and then proceed to dry out, losing much of their weight, which plays a large role in making them so dangerous. In addition to killing the tree, the process appears to have the added, and seemingly counter-intuitive, benefit of making the trees less likely to fall in high winds.

“When the trees drop their leaves, they’re losing their sail, which catches the wind. We found that they didn’t fall over (during the storm) nearly as much as the live trees,” she said.

Instead of cracking and falling, the dead trees have a tendency to crumble away slowly.

Despite these findings, Kaye warned that residents should not take it upon themselves to poison albizia trees near homes, roadways or utility lines. Known as hazard trees, they should be handled by certified contractors in order to prevent dangerous situations.

Over the course of the pilot program, she added, the cost of controlling such hazard trees has been estimated to be about $200,000 per mile of roadway, including a setback of about 150 feet to either side of the road.

“We’re really trying to get a handle on (the costs),” she said. “We need to be able to give a good number. … The cost goes up the more hazards you’re dealing with. When you have one large tree on the side of the road with no buildings or power lines nearby, it can cost $1,000-$1,200 for a really big tree. As soon as you get a power line or house involved, that cost can double or even triple.”

Currently, staff members are working to map areas of roadway and utilities surrounded by albizias to provide a better estimate of how much money would be needed to control the problem on the island. Then, she said, it will be time to seek funding from various county, state and federal sources to put a control program in place.

As for individual citizens, “there needs to be an organized effort,” Kaye said. “There are so many people who live in these private subdivisions, and they really need to put their foot down and say ‘Enough is enough. We’re not going to allow these trees to stay here anymore.’ They need to start putting pressure on every neighborhood organization to address the problem.”

Last year, the county passed a new law empowering the mayor to force land owners to address hazard albizia trees or to allow the county Department of Public Works to do so and then bill the landowners, but unfortunately, such efforts were not given any additional funding.

“They need to be funded to do that,” she said. “Additionally, there needs to be public support for the county having the right to enter private property whether they can get hold of private landowners or not.”

As of Monday, the Department of Public Works had received from residents 79 complaints about neighboring hazard trees since the new law went into effect. However, only 14 of those issues had been addressed, because of complications contacting land owners, Kaye said.

In an interview Tuesday afternoon, Mayor Billy Kenoi said he agreed that now was the time to address the albizia problem on Hawaii Island.

“When you drive through Puna, you see the impact of the storm,” he said. “When you do aerial assessments, you realize it’s an issue we have to address right away. The albizia threat to homes, communities and infrastructure in a hurricane or high wind storm, that’s a threat that still exists.

“We certainly have to take a look at our infrastructure and albizias and their proximity to roads, homes and businesses and really determine that we’ve gotta address that in as expedited and strategic a manner as possible.”

Complaints concerning hazardous trees may be filed at http://www.hawaiicounty.gov/pw-complaint/.

The Big Island Invasive Species Committee is available on Facebook and at biisc.org.

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

 

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