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the “success” of natural recovery versus planted sites, we see that practitioners are still
faced with signifi cant challenges. This paper makes the case that observation and
monitoring of natural regeneration, and calculation of rates of recruitment after a
major disturbance event is equally or more important than mangrove planting, from
not only ecological but also social and economic points of view.
Keywords
Natural revegetation Post-tsunami Rehabilitation Mangrove
19.1
Background: The Impact of Aceh's Seismic Events
(Earthquake and Tsunami) on Mangrove Populations
19.1.1
Simeulue District
The Sunda Megathrust occurs along the Western Coast of Sumatra, and extends
northwards to Myanmar and Southeast along the Southern coast of Java and Bali,
terminating near Australia. It is a volatile region, as it represents the interface
between the overriding Eurasian plate and the subducting Indo-Australian plate
(Briggs et al.
2006
). Numerous large seismic events have occurred along this mega-
thrust, including the eruption of Krakatau, and the 2004 tsunami which claimed
over 225,000 lives. (Chlieh et al.
2007
).
By reading the corals, much like foresters read tree-rings in temperate latitudes;
researchers have been able to tell that major seismic uplift has occurred in 1370,
1600, 1797 and 1833, meaning this occurrence of tectonic emergence is cyclical
(Briggs et al.
2006
). Subsidence after uplift events occurs in each instance as the
Indian Ocean plate sinks and curves under the land mass of Sumatra. This submer-
gence takes somewhere between 75 and 150 years to return the islands to their
pre- earthquake position, after which the spring is again loaded and the plate ready
for another large earthquake (Briggs et al.
2006
).
Prior to the 2004-2005 seismic events, mangrove distribution on Simeulue island
occurred nearly entirely along the northern coast of the island, which is protected
from the strong waves and currents experienced on the southern coast (Fig.
19.1
).
As a result of the March 2005 earthquake, the island rose on average 100-150 cm
on the Eastern and Western ends, and around 25-75 cm along the central portion
(Fig.
19.2
). The entire annual tidal range of Simeulue Island, from Lowest
Gravitational Tide (LGT) to Highest Gravitational Tide (HGT) is only roughly
78 cm. Approximately 24 species of mangroves have been identifi ed on the island,
all of which must exist within that limited tidal range. In fact, the extent of their
habitat is narrower still, as they exist only from around Mean Sea Level (MSL) up
to HGT, or about 38 cm above LGT up to 78 cm above LGT. The author obtained
data points for uplift around the Simueule island, as well as recent tidal data
directly from Sieh K (2013, California Institute of Technology (USA), personal
communication), enabling the understanding of mangrove re-establishment.
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