By Caroline Farley
Once a vibrant source of food and a tribute to the natural beauty and culture of the island, the Hule‘ia Watershed has been depleted of its resources and native vegetation due to a widespread red mangrove invasion.
This tall, highly invasive tree introduced to Kaua‘i about a century ago, now covers some 62 acres in the Hule‘ia Watershed, causing an environmental, cultural and economic havoc in the area.
But thanks to a resilient group of people, the watershed has a good shot at regaining much of its former glory. Volunteers at the nonprofit Malama Hule‘ia have already demonstrated what they can do by clearing two-and-a-half acres of a former mangrove-infested habitat at Niumalu Beach Park near Nawiliwili Harbor in the last two years. The goal now is to restore the entire watershed.
“You cannot imagine what this place looked like two years ago. One thing for me is that we got the beach back,” said marine biologist and Malama Hule‘ia Board Director Carl Berg.
“I can take my son fishing here now, whereas before the only fishing site was over at the canoe ramp,” he said while looking at the restored beach park.
On June 16, the nonprofit held an open meeting to share with the public a draft plan for an ambitious project to remove all the red mangrove from the entire watershed and promote native species reforestation.
The red mangrove was introduced to Kaua‘i by the sugar industry for soil stabilization purposes in the early 1900s. Since then, this rapidly growing tree has thrived in wet intertidal areas of the Hule‘ia Watershed and within Alakoko Fishpond, also known as Menehune Fishpond.
Malama Hule‘ia’s mission is to completely eradicate red mangrove within the ecosystem of Hule‘ia and Pu‘ali. The nonprofit works to promote the seriousness of replenishing the Hule‘ia Watershed through active community involvement and hands-on work to remove the spreading trees.
Since early 2013, Malama Hule‘ia has held monthly community workdays for volunteers to manually remove the mangrove and replant native species at Niumalo Beach Park. Some of those native species came back on their own once the mangrove was removed, Berg said.
The restoration project at the beach park — which two years ago was mostly blocked by red mangrove — is coming full circle, and will serve as a demonstration site for what is possible in the rest of the watershed.
“It is incredibly hard work, yet extremely rewarding. The volunteers are wonderful people truly dedicated to cleaning up the watershed,” said Ruby Pap, Coastal Land Use Extension Agent of University of Hawai‘i Sea Grant, Malama Hule’ia’s partner in the project.
“The improvement at the end of the day makes it all worth it to know we are that much closer to reaching our goal,” she said.
The “Draft Red Mangrove Invasive Species Action Plan for the Hule‘ia” presented to the public by Pap and Adam Asquith, also of UH Sea Grant, explores a few options to rid the watershed of mangrove trees, including injecting the trees with herbicides, manual removal of the trees, equipment removal and a mix of manual labor and equipment use.
Though the eradication at the demonstration site was accomplished mostly with volunteer work, the entire project would probably need to utilize contract work, according to Asquith.
Malama Hule‘ia preferred choice is a combination of hand-cutting the mangrove with the help of some equipment to carry out the job. This method can be dangerous to workers — some mangroves reach 40 feet in height — but there is minimal impact to the environment and the permits are somewhat easier to obtain than the herbicide method. Depending on several factors, including volunteer labor, paid labor and the extent of equipment use, the cost to remove the trees would be between $25,000 and $100,000 per acre.
Once approved and all the permits are in place, this method would use about 15 workers who would hypothetically take two-to-three years to finish the job, according to Asquith. The entire cost would fall somewhere between $1.55 million and $6.2 million, with more costs associated with planning and permitting. Additional one-to-two years for site maintenance would be necessary to ensure the mangrove doesn’t come back.
Asquith said at first he was skeptical about the project’s feasibility. But after reviewing other areas across the state where complete eradication of mangrove has been accomplished, he changed his mind. One potential hurdle is that the Hule‘ia Watershed is unique in a sense that there are 49 landowners in the area, which is an unprecedented challenge. The plan includes forming partnerships with landowners and other stakeholders.
Besides eradication methods, partnerships and fundraising efforts, the plan also includes the establishment of a stewardship organization to maintain the area free of Red Mangrove forever.
Continued efforts to clean the watershed will result in the return of native Hawaiian fish and endemic water birds such as the Hawaiian stilts, coots, Hawaiian ducks and moorhens.
A significant improvement in water quality is expected with the elimination of the mangroves, which currently devoid the water of oxygen needed for native species. The river cannot flush out sediment with the mangroves present, so by removing the invasive trees, water flow will pick up, replacing the current stagnant, sewage-smelling water with a healthy flow.
If no action is taken, the Alakoko Fishpond is at risk of being completely covered by mangrove, according to Berg. Not only the loss of the fishpond would be critical to the environment, the cultural loss would be irreversible. The legend behind the fishpond — one of the most valued Native Hawaiian historical and cultural sites — is that it was built by a mythical race of short humans called menehunes. They supposedly worked at night, and accomplished monumental tasks while everyone else was sleeping.
The next immediate step in Malama Hule‘ia’s plan is to begin clearing the fishpond in the same successful manner as the work that took place at Niumalu Beach Park.
Ongoing Malama Hule‘ia community workdays at the beach park are held on the third Saturday and Sunday of the month, starting at 8:30 a.m. In addition to scheduled regular sessions, there may be others held for special groups of volunteers.
Visit www.malamahuleia.org for more information or to download the draft plan.