Efficacy of alternative low-cost approaches to mangrove restoration,American Samoa |
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Authors: | Eric Gilman Joanna Ellison |
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Institution: | 1.IUCN (The World Conservation Union) Global Marine Programme and University of Tasmania School of Geography and Environmental Studies,Honolulu;2.University of Tasmania School of Geography and Environmental Studies,Launceston,Australia |
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Abstract: | Three mangrove restoration methods were tested at Nu’uuli, Tutuila Island, American Samoa. Since clearing 27 years ago converted
the mangrove into a mudflat, the ecosystem was sufficiently altered that it could not self-correct; the ecosystem showed no
natural regrowth despite an ample supply of propagules. While several years of monitoring may ultimately be required to determine
the project’s success, and several decades could be required to fully return the full suite of functions, the project’s low-cost,
nontechnical restoration techniques, using readily available materials, have proven to be modestly successful, with 38% sapling
survival after six months. Several years of monitoring will be necessary to determine if the restoration site’s small elevation
deficit relative to a reference site ultimately requires modifying the site’s physical structure to correct the hydrology.
Direct community participation in the project was critical to reduce the risk of human disturbance of the restoration site.
One year project costs were about USD 2,150 or USD2,150 or USD 13,030 ha−1. Labor comprised 84% of expenses; replicating the restoration project in developing countries would cost less due to lower
wage levels. Six months after initial restoration activities, there was a highly significant difference betweenBruguiera gymnorrhiza andRhizophora mangle sapling survival, with 21% and 45% of the original 42R. mangle and 95B. gymnorrhiza saplings remaining, respectively. The lowerR. mangle survival may have resulted from an unavoidable need to source saplings from an area with different environmental conditions
than the restoration site. Saplings were transplanted into tires filled with sediment as a simple, low-cost method to raise
the elevation of the sediment surface. Saplings were also transplanted adjacent to rebar and without any support mechanism.
There was no significant difference in sapling survival by treatment for individual or combined species. The restoration project
is a model for the community-based, simple, low-cost approaches to ecological restoration needed in the region. Pilot projects
using similar techniques may be worth pursuing at the other 15 Pacific Island countries and territories where mangroves are
indigenous. |
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