Building Island Resilience against Climate Change: Integrating Science into a Community-Based Initiative Reviving Watersheds, Coral Reefs, and Fisheries in Guam

Shelton, Austin
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[Honolulu] : [University of Hawaii at Manoa], [December 2015]
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Climate change is a clear and present threat in small tropical islands, requiring solutions at both global and local levels. The goal of this research was to take a community-based approach to building island resilience against climate change. The removal of local environmental stressors helps to restore natural ecosystem functions, promoting resistance to and more rapid recovery from global climate change impacts. The Humåtak Project was developed as a community-based initiative directed at reviving coastal watersheds, downstream coral reefs, and nearshore fisheries in Guam, Micronesia. A sixpart community engagement strategy was created and serves as a model for other communities. The Humåtak Project addresses accelerated erosion, a major local environmental stressor caused by poor land-use practices. Erosion results in terrigenous sedimentation on coral reefs, which smothers and kills corals, interferes with coral reproduction and recruitment, and destroys essential fish habitat. Nearly 2,000 volunteer hours were contributed to reducing erosion in the La Sa Fu’a Watershed. Tree seedlings and sediment filter socks were tested as watershed restoration tools over a 21-month period. These tools were effective in trapping 112 tons of sediment on land. Previous studies indicate a 75% reduction in sedimentation rate is required to bring Fouha Bay below severe-catastrophic sedimentation stress (>50 mg cm-2 day-1). Based on the observed sediment trapping efficiency of restoration tools in this study, an estimated 0.05 km2 of severely eroding hillsides must be treated with 19 km of socks and 11,000 trees to trap 2,121 tons of sediment to achieve the necessary reduction. To inform future monitoring efforts as restoration of the watershed continues, deposited sediment in Fouha Bay was analyzed to determine grain size fractions and composition. If sediment input into the bay is controlled, existing sediment will clear out with storm-driven swells. As shown in other high islands, coral reefs are resilient and can recover after sedimentation stress is reduced, provided recruitment and survivorship remain viable. The community engagement strategy and data generated on the effectiveness of watershed restoration tools can be used in management plans to build resilience against climate change in other tropical islands.
Ph.D. University of Hawaii at Manoa 2015.
Includes bibliographical references.
watershed, coral reef, sediment, climate change, natural resource management, social-ecological resilience
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Theses for the degree of Doctor of Philosophy (University of Hawaii at Manoa). Zoology
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