Native and Non-Natives Working Together

Staff Writer Jessica Zima-Lee

Photographs by Jessica Zima-Lee

tree fern in a forest

Back in 2004, researchers began looking at the state of East Hawai‘i’s lowland wet forests. Principle Investigators (PIs) Rebecca Ostertag (University of Hawai'i at Hilo), Susan Cordell (USDA Forest Service at the Institute of Pacific Island Forestry) and Peter Vitousek (Stanford University) examined data from forests at the Hawai’i Army National Guard Keaukaha Military Reservation (KMR).

These researchers were initially funded by SERDP, the Strategic Environmental Research and Development Program, from late 2011-2012 to look at the carbon storage characteristics of the forest plants. They came across data that showed a decreasing population of native species, like the ōhi’a and māmaki, whose tree saplings were not re-appearing to replace the dying elder trees. Their first attempt to remedy this problem was via the removal of invasive species in hopes of improving the native tree canopy.

However, the invasives grew back too quickly and their group realized that returning the forest to its all-native status was sadly unlikely. At that moment, they knew they needed to attack the problem from a different angle. With numerous projects and research from over the years, the Liko Nā Pilina project blossomed from the idea of a hybrid ecosystem.

The Liko Nā Pilina project’s goal is to bring together collaborating groups of people to create hybrid ecosystems, communities of native and non-native plant species that are non-invasive to restore the Hawaiian lowland wet forest (HLWF). In general, this means they are using plants that have not only evolved in Hawai‘i, but also plants like kukui and ‘ulu (Hawaiian breadfruit), which were introduced by the Polynesians.

Dead leaves on the ground on a hiking trail

More specifically, for one year, researchers collected data on 15 functional traits of 35 different plant species. These functional traits influence a plant’s growth, reproduction and survival. The plants were then grouped together based on these traits and whether they had slow or moderate carbon turnover. A total of 10 plants were placed in each forest plot: four core species plus six other species that either had complimentary (different) or redundant (similar) functional traits.

It’s all a bit confusing, so Ostertag often relates it to creating a fantasy football team with great offensive and defensive lines. She says, “If everyone is an offensive position…on defense, your team isn’t going to do well…but if you have a team that’s more balanced and diverse in their roles, we think the team will do better.” So if there is a mixture of species working together to use the environment’s resources more broadly, this may keep out the invasive plants. The invasives will no longer have a spot in the forest because it is taken by another species with similar traits. We’re trading an invasive offensive lineman for a non-invasive lineman.

After 10 months of clearing land and another year’s worth of planting in the KMR, the Liko Nā Pilina project finally came together in January of 2014. From then on, the forest plots have been maintained, protected from wild pigs, and monitored in their growth and reproduction rates.

DiManno came onto the project while they were still clearing forest land and designed the protocol used for planting their chosen species. She and Ostertag reported that the plots with moderate carbon turnover plants alongside plants with redundant traits, have now been producing fast growing trees that keep invasive species out. They also found it interesting that while invasives were kept out, non-invasive species were able to come in and take root. Among these fast growers are the false kamani, mango, and avocado trees, with the ‘ulu being the star quarterback of this species team.

Dead ohia tree amongst non native trees

Sadly, there is some bad news. DiManno says that there has been an almost 40% decrease in the ōhi’a population over the past four years of monitoring the KMR. This translates to a 12% decrease per year in the ōhi’a population mainly due to Rapid Ōhi’a Death (ROD). Similarly, she has seen other natives like the lama and kolea trend parallel to the ōhi’a even though they are not directly affected by ROD. DiManno says, “They could be dying off because they are not able to withstand the changes in the canopy dynamics. We’re all just keeping our fingers crossed that some of these trees will develop a resistance to it (ROD).”

Luckily, in 2017 Liko Nā Pilina has gained support and funding for five years from the Hawai‘i Army National Guard who is responsible for the KMR. DiManno says, “One of the coolest things about this project, is that on base, they want to incorporate similar plantings and restore the area. They’re working with us to learn how to manage their forest.” While the Hawai‘i Army National Guard is collaborating with the Pilina team, other groups have also come in to lend a hand. Alongside the PI’s, there have been post-docs, grad and undergrad students, technicians, interns from the US and abroad, numerous college and high school class volunteers, and Hawaiian summer school programs, all who have helped in hopes of bringing back the HLWF.

As the Liko Nā Pilina project has seen a diverse team of native, international, local, and visiting individuals collaborating together, there is great hope in their example that this diverse plant species “team”, a hybrid ecosystem, will lead to the regrowth of the Hawaiian lowland wet forests. The UH Hilo student body, UH Hilo clubs, the community, anyone and everyone is welcome to join the team in their forest preservation efforts. If you are interested in getting involved please contact Nicole DiManno by email at nicole.dimanno@gmail.com or check out the project website at https://hilo.hawaii.edu/faculty/ostertag/LikoNaPilina/.