Growing Progress: Utilizing Conservation and Community to Manage Albizia Trees
Posted on Jun. 27, 2024 / Invasive Species / Subscribe 0
By: Alanna Miyashiro
Hotspots of invasive species are spreading across Oʻahu. It has become apparent that the control of invasives is not only integral to ecological preservation but also to protecting our ways of life in Hawaiʻi and the health and safety of our people. How do we combat what seems like a never-ending list of pests that continue to grow? Conservation organizations cannot do it alone. It will take the collective efforts of organizations, legislators, and members of the public to collaborate on and enact long-lasting, effective solutions.
At the Koʻolau Mountains Watershed Partnership (KMWP), invasive albizia (Falcataria falcata) trees are an imperative target species. The work being done across the partnership demonstrates how united actions can lead to landscape-scale changes. These trees are being cleared one by one in summit regions by their field crew. In low-elevation urban areas, KMWP trains people to identify and eradicate albizia to protect their homes and loved ones.
Figure 1. A mature albizia (Falcataria falcata) tree. Photo by Forest & Kim Starr.
Albizia was introduced throughout Hawaiʻi in the early 20th century to reforest degraded watersheds with timber trees. They can be identified through their smooth, grayish bark, flat canopies, and compound leaves. Unfortunately, the timber industry never boomed in the state and the tree was left to spread across the islands. In Hawaiʻi, albizia is considered one of the fastest-growing trees in the world, growing as much as 15 feet in one year and to heights of over 100 feet tall. Due to its fast-growing nature, albizia has a brittle wood structure, making it prone to a phenomenon called “sudden limb shear” or “sudden branch drop.” This means that at any moment, albizia can drop large branches. Entire trees can tip over in high-wind events because of their shallow root systems, making them dangerous when growing over homes and roads. After Tropical Storm Iselle in 2014, large stands of albizia on Hawaiʻi Island blocked major roadways and fell on powerlines and homes, leaving some people without power for over three weeks. Ecologically, this species increases erosion and changes soil chemistry and light levels to allow other invasive plants to grow. Currently, about 20,000 acres of Oʻahu are considered infested with albizia.
Figure 2. A fallen albizia on Hawaiʻi Island after Tropical Storm Iselle. Photo by Star Advertiser.
For over a decade, albizia has been targeted by KMWP. Their field team controls this species throughout the Koʻolau mountain range. In total, over 11,000 trees have been treated so far. For their operations, the crew utilizes aerial imagery and drone footage. After picking out albizia hotspots, staff will fly by helicopter or hike into an area to individually treat each tree. Through their hard work and perseverance, KMWP has been able to successfully clear entire valleys and declare them “albizia free.” These valleys include Hālawa along the H3 highway, Moanalua, and portions of Waiawa and the State of Hawaiʻi Kaluanui Natural Area Reserve. The most recent success is the clearing of albizia in Waiʻalae Nui in 2023. “By finishing the last albizia in Waiʻalae Nui, it marks a big step in albizia control and management in the Southern Koʻolau. This is the catalyst to fully eradicate albizia south of Waiʻalae Nui,” remarks Jordan Lewis, the KMWP Wildlife Management Specialist. Areas that are deemed free of albizia will be continually monitored for any new regrowth. The field crew will continue with albizia control in areas like Mānoa, Waiheʻe, and Haʻikū. They have plans to expand to Pālolo and Wailupe within the next two years.
Figure 3. Map of Oʻahu showing current albizia infestations and KMWP albizia operations.
Figure 4. KMWP field crew members treating a large albizia in Waimalu.
The Rapid Albizia Death (RAD) program is KMWP’s outreach component connected to controlling this species. This effort targets “high priority” communities—those with large albizia infestations growing in and around an urban setting. These areas are the most at risk of having hazardous trees and mitigation there can have the greatest positive impact on public safety. Some factors complicate mitigation efforts, for example: contracting an arborist to remove a mature hazard tree can cost upwards of $10,000 or more, making it virtually impossible for any average homeowner to afford. After these areas are identified, informative mass mailers are sent to every home and KMWP collaborates with local legislators and community leaders to host public discussions and workshops. These events are the initial start for creating new RAD groups. They are meant to educate, train, and empower community members on identifying albizia, assessing their hazard levels, and treating non-hazard trees on their properties. These trainings hopefully lead to grassroots movements that are spearheaded by the community itself because they have the tools necessary to organize and advocate.
Figure 5. Albizia mass mailer postcard.
Figure 6. Previous KMWP Manager, JC Watson, demonstrating ring-barking technique on a young tree during an albizia workshop held at First Presbyterian Church 10/23/23.
The initial RAD Hui was first coordinated in Mānoa Valley. Mānoa has one of the largest urban-interfacing populations of albizia and numerous hazardous trees are growing throughout the community. Collaborating with the organization Mālama Mānoa, volunteers survey the length of Mānoa Stream and remove albizia seedlings. To date, over 2,400 albizia seedlings have been removed from the stream, preventing future hazards and saving thousands of dollars in future removal costs for homeowners. In 2025, KMWP and Mālama Mānoa will use State Grant-In-Aid funds to remove hazardous albizia along the stream, protecting homes and preventing future flooding impacts.
In Kāneʻohe, First Presbyterian Church leads a RAD Hui to remove large albizia during their monthly volunteer workdays. This will gradually transform the Koʻolau Ballrooms golf course into a more natural area for recreation, conservation, and research. So far, KMWP has also hosted community albizia events in Heʻeia, Waiāhole, Maunawili, Pālolo, and Kalihi. KMWP is hoping to continue supporting existing RAD efforts and expand into Koʻolauloa.
Figure 7. KMWP staff, Mālama Mānoa volunteers, Representative Andrew Garrett, and Representative Scott Matayoshi during the Mānoa Stream survey 11/11/23.
Numerous albizia movements are happening across the state as the topic of invasive species management continues to make headlines. Other organizations like the Albizia Project focus on using this species as a sustainable lumber and woodworking resource, integrating invasive species management as a tool for a more circular economy and reducing the reliance on imported materials. The founders of this organization also started Bizia Surf & Coffee Bar, a cafe and studio in Wahiawā, selling household goods and surfboards made out of this tree. On Hawaiʻi Island, the Big Island Invasive Species Committee (BIISC) coordinates the Albizia Assassins program which provides education, training, and volunteer events. Albizia Assassins served as a blueprint for KMWP’s RAD program.
There is some form of albizia management on almost all of the main Hawaiian Islands. Therefore, the State Wide Albizia Group (SWAG) was formed under the Hawaiʻi Invasive Species Council (HISC). It provides a space where organizations can regularly meet to share developments related to legislation, control techniques, and funding opportunities. Working in partnership, we can leverage our strengths and support one another in times of need, protecting our Hawaiʻi one tree at a time.
0 Comments