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Trends in surface elevations of American Samoa mangroves


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Gilman, E, Ellison, JC, Ierupaala, S and Tuaumu, S 2007 , 'Trends in surface elevations of American Samoa mangroves' , Wetlands Ecology and Management, vol. 15, no. 5 , pp. 391-404 , doi: 10.1007/s11273-007-9038-6.

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Rates of change in elevation of mangrove
surfaces, determined from observations of changes in
the height above the mangrove surface of stakes,
generally inserted through the organic peat layer to
reach consolidated substrate, were measured in one
fringe and one basin mangrove wetland on Tutuila
Island, American Samoa. Knowledge of trends in
elevation change of coastal wetlands contributes to
assessing vulnerability to projected relative sea level
rise. The fringe and basin mangroves had rates of
change in elevation of 0.6 mm yr1 (±2.0) and
2.2 mm yr-1 (±5.6), where a negative result means
lowering in elevation. These trends were not statistically
significant (P > 0.05) and the error intervals
around the point estimates of trends in change in
elevation overlap zero for both study sites, meaning
that it is not clear if the mangrove surfaces have been
lowering, rising or not changing. Despite the large
error intervals, likely due to short-term variability and
cyclical patterns in sedimentation, results indicate
that the fringe mangrove has been experiencing a rise
in sea level relative to the mangrove surface as the
relative sea level rise rate (+1.65 to +2.29 mm yr1)
has been exceeding the rate of change in elevation of
the mangrove surface (2.6 to +1.4 mm yr1). It is
unclear if the basin mangrove has been experiencing
a rise in sea level relative to the mangrove surface. If
upper projections for accelerated relative sea level
rise in American Samoa occur over coming decades,
American Samoa mangroves will migrate landward,
where unobstructed, as a natural response to relative
sea level rise.

Item Type: Article
Authors/Creators:Gilman, E and Ellison, JC and Ierupaala, S and Tuaumu, S
Journal or Publication Title: Wetlands Ecology and Management
Publisher: Springer Science+Business Media BV
ISSN: 0923-4861
DOI / ID Number: 10.1007/s11273-007-9038-6
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