The Hawaiian archipelago, like other oceanic islands, is very susceptible to biological invasions. Because of the archipelago’s long isolation, it became home to unique flora and fauna which evolved on the islands. Although Hawaii’s native biodiversity was relatively low (especially in comparison to other tropical biomes), the rates of endemism on the islands were very high. With the arrival of humans came a variety of new species and the extinction of some native species. In particular some species which have been introduced have become invasive- that is, they thrive in their new habitat to the extent that they are detrimental to native species and ecological functioning of native ecosystems. Lowland wet forests in Hawaiʻi have been hit especially hard by human activities and invasive species, to the point where there are very few of these forests left. In some lowland wet forests, there are still native species in the canopy, particularly ‘ōhi’a, lama (Diospyros sandwicensis) and kōpiko (Psychotria hawaiiensis). However, the presence of a multitude of invasive species means that even though the native species are present, there is very limited recruitment of seedlings happening. In other words, while the adults are surviving, few-if-any seedlings are surviving into adulthood. It’s a case of ‘dead men standing’: when the existing adults die, this forest will become wholly made up of exotic and invasive species. Our project has two main goals; the first is to restore the forest in line with the land manager’s wishes. This means putting together a forest community that minimizes ongoing management costs and effort, enhances carbon storage, creates an open understory and benefits native biodiversity. The second goal is to test hypothesis about community assembly in a complex rainforest environment. To accomplish these goals, the first step was to remove the invasive species from our study plots. While ‘weeding’ sounds fairly simple and straightforward, things become a little more complicated when your weeds happen to be ~30 meters tall and have multiple trunks which are fairly entangled with other trees in the high canopy!!
The Liko Nā Pilina project started with a grant to Rebecca Ostertag (University of Hawaiʻi at Hilo), Susan Cordell (USDA Forest Service at the Institute of Pacific Island Forestry) and Peter Vitousek (Stanford University) from the Strategic Environmental Research and Development Program (SERDP, Grant # RC-2117) and has continued from there. It is now funded by National Science Foundation DEB-1754844 for the arthropod component and the maintenance by the Hawaii Army National Guard.