Portland State University. Department of Environmental Science and Management
Elise F. Granek
Date of Award
Master of Science (M.S.) in Environmental Science and Management
Environmental Science and Management
1 online resource (x, 149 pages)
The formation of novel ecosystems by non-native species poses management challenges that are both socially and ecologically complex. This complexity necessitates consideration of both ecological dynamics and social attitudes and perceptions. Red mangrove propagules were introduced to Moloka'i, Hawaii in 1902 to mitigate the effects of soil erosion and they have since spread along the coast and to adjacent islands creating novel habitat. Non-native mangroves in Hawai'i present a unique case study to examine diverse social attitudes and perceptions resulting from a long history of land cover transformations on the Hawaiian Islands, socio-cultural diversity of involved stakeholders, and the potential array of ecosystem services they may provide under changing land use and climatic conditions.
Ecological dynamics were examined to (1) determine whether novel mangrove habitat affects zooplankton diversity and richness, (2) test the hypothesis that zooplankton community composition differs significantly among established mangrove and coastal non-mangrove habitat, and (3) assess other factors driving differences in zooplankton community assemblages. This study found no significant differences found between sites with and without mangroves in terms of richness, diversity, or community composition. However, lunar cycles and site dynamics, including fishpond structure, mangrove and open shoreline length, percentage of mangrove shoreline length, total percentage of carbon in mangrove leaves, and disturbance in the upstream watershed influenced zooplankton community composition. These findings suggest that non-native mangroves support community composition, richness, and diversity similar to non-mangrove areas, though some widespread taxa have lower abundances in mangrove habitat. My research suggests that in the face of declining fisheries, threatened reef habitat, and changing climate and ocean conditions, mangroves may provide zooplankton habitat in novel locations similar to that provided by native habitat, such that habitat availability for zooplankton is not hindered by non-native mangroves.
To understand social dynamics 204 residents of Moloka'i, Hawaii were surveyed to evaluate: 1) attitudes and perceptions about this non-native species, 2) what factors influence these attitudes, and 3) how attitudes influence perceptions about management. A belief that mangroves should be removed, concern about threats to Moloka'i's coast, and not relying on mangroves for benefit were the primary drivers of negative attitudes towards non-native mangroves. Support for management actions was predicted by attitudes towards mangroves, perception and concern about threats to Moloka'i's coast, and experiences involving mangroves. I propose a framework for assessing and incorporating diverse perceptions and attitudes into decision-making around non-native species that have created novel ecosystems.
An active management approach allowing mangroves to thrive in certain locations and to provide services such as habitat and crabbing access while in other locations limiting their extent to protect native bird habitat and cater for human needs, including safe beach and ocean access, may ultimately offer the greatest benefits to both the ecosystem and society. As environmental issues, such as species introductions, become increasingly complicated in the age of the Anthropocene, with intricate relationships made more difficult in the face of climate change, integrated research in socio-ecological systems may provide a comprehensive approach to better evaluate and understand our changing world.
Lewis, Casey Lynette, "Non-Native Mangroves (Rhizophora mangle) of Moloka'i, Hawai'i: A Socio-Ecological Analysis" (2017). Dissertations and Theses. Paper 4074.