Community-based streamside Albizia removal and restoration in Hawaiʻi

Abstract

Degraded watersheds and the associated loss of ecological services exacerbate erosion and fail to protect human infrastructure during extreme precipitation events which are becoming more frequent globally. Non-native plant invasions are a major contributor to watershed degradation, necessitating their removal to restore watershed function. In Hawaiʻi, Albizia (Falcataria moluccana) is a highly invasive and hazardous tree that can grow up to 5m annually. During high flow events, Albizia can clog streamways, damaging homes, and threatening human life. The objective of this project was to create an publicly accessible document on streamside Albizia in Hawaiʻi that outlines a framework for communities to follow and provides recommendations on (i) removal techniques, and (ii) streamside ecological restoration following Albizia removal. Recommendations were created by synthesizing information from a literature review of available resources on Albizia removal and restoration (e.g., peer reviewed documents, websites, management plans). In addition, interviews were conducted with local land practitioners (non-profit groups and small community groups) conducting Albizia management in Hawaiʻi. I assisted a case study site on the Kalihiwai River, Kauaʻi conducting similar work to test and refine recommendations. The literature review and interviews were used to create a streamside ecological restoration flowchart designed to guide community members in streamside Albizia removal and restoration projects. Resources in the flowchart include a compiled reference list of ecologically and culturally important plants to inform replanting of restoration sites. At the case study site, several hazardous trees were identified and removed along the streamside and non-hazardous tree removal techniques were shared with members of the community. The case study site highlighted the social intricacies of invasive species management as well as the foundational work needed to continue maintenance and monitoring of restoration projects. Most restoration projects lack funding for long-term restoration monitoring beyond the large initial cost of tree removal. In particular, conducting large-scale removal of mature, hazardous trees takes substantial effort and money from community groups to execute. Access to the results of this project can provide a framework for similar efforts in Hawaiʻi and on other Pacific Islands in cases that require community management with limited initial knowledge and funding.