Ulva sp. in the lower areas (Johansen, 1971). Some 5 years
after the quake, however, the original patterns of barnacle
distributions had reestablished, Fucus had returned to dominance, mussels had reestablished on rocks at lower tidal
levels, and the species diversity at MacLeod Island was
more diverse than it had been immediately post earthquake.
Generally, the effects on estuarine ecosystems of uplift
appear greater than those of subsidence, although relatively little attention has been paid to documenting the latter type of changes. In Prince William Sound, for example,
in areas where subsidence had occurred, the overlapping
of pre- and post-quake communities was observed, with
high intertidal snails found grazing among the submerged
terrestrial vegetation.
Wetlands
Coastal wetlands such as salt marshes are vulnerable to
earthquake damage and sea-level change since they represent a transition zone between tidal flats and uplands. Due
to land subsidence following earthquakes along the
Cascadia subduction zone approximately 300 years ago
and also in southern Chile (1960), coastal forests were
decimated and sedimentation from tsunami activity
resulted in the establishment of salt marshes in protected
locations with gently sloping shorelines and suitable sediment supplies (FitzGerald et al., 2008). The sudden relative sea-level changes that occur following an
earthquake, however, may not mimic models of climate
changes where the estimated rates of change are of the
order of millimeters to centimeters per year (Reed,
1990). In many areas, the natural recolonization of salt
marsh habitats following extreme events has been slow,
and intervention may become necessary to restore bird
habitats (unpublished data).
In the subtropics, following earthquake and associated
disturbances such as tsunami, salt marshes may be
replaced by mangroves, which are known to recover rapidly from other natural disturbances such as storms and
cyclones. Following the Boxing Day 2004 M w 9.1–9.3
Sumatra earthquake and subsequent Indian Ocean tsunami, Aceh Province soft-coast mangroves were assessed
as being more sensitive to disturbance than rocky headlands, with sandy coasts occupying an intermediate
position (Wong, 2009). Past and current records of
sea-level changes on soft coasts suggest that mangrove
forest resilience, where natural regeneration is expected
to take 10–15 years, allows this ecosystem to adapt to both
the incremental changes that are associated with global
change and the event-scale changes associated with earthquakes and tsunamis (Alongi, 2008). There have been
reports of extensive ecosystem damage, with 51–100 %
of mangroves destroyed in the Nicobar Islands following
the Sumatra 2004 earthquake and tsunami, with similar
damage to coral reefs (41–100 %) and to forests
(7–27 %) (Ramachandran et al., 2005). This damage,
however, is insignificant in comparison to the ecosystem
destruction produced in Indonesia over recent decades
by clearance for coastal development such as shrimp
farms (Idrus, 2009). Reports on the coastal protection
value of mangrove forests during the 2004 tsunami event
are mixed but, overall, suggest that they provided significant protection to landforms, either through the dissipation
of wave energy or through the pre-tsunami progradation of
shorelines, in several Indian Ocean countries. While some
studies indicate that mangrove forests can provide better
storm protection than concrete barriers, the effectiveness
will vary depending on location, previous history, and
presence of non-mangrove vegetation (Dahdouh-Guebas
et al., 2005). Also in the case of a large tsunami or storm
surge, coastal forests and dunes are generally believed
to have provided minimal hinterland protection, as
found during the devastating 2011 Tōhoku earthquakeinduced tsunami (Lavigne et al., 2007; Gomez et al.,
2010; Gomez, 2012).
Mudflat infauna
Shallow water estuarine mudflat habitats are exposed to
multiple environmental stressors, and, according to
Thrush et al. (2008), such communities can recover as
long as the recovery potential of the resident fauna
exceeds the disturbance effects. When this does not occur,
then the loss of species leads to habitat loss and fragmentation across landscapes. These types of changes have
been observed following earthquake events worldwide.
In shallow water soft sediments, the fauna is often dominated by bivalves which might be expected to have natural resistance to environmental perturbations. In Olsen
Bay, Prince William Sound, before the 1964 Alaska earthquake, there were five different species of clams, shellfish
resources for people and predators, representing different
feeding types; fast and slow burying species; and those
that bury to different sediment depths. Mortality patterns
after the 1964 Alaskan earthquake were species specific
and depended on the degree of sediment displacement
and bed uplift, which essentially raised or lowered the animals’ vertical distributions. High mortalities were
recorded in maximal uplift areas for butter clams
(Saxidomus giganteus) which, pre quake, were usually
buried at depths of 35 cm in the sediment (Baxter, 1971;
Hubbard, 1971). In places where the sediment had been
removed, shellfish were exposed on the surface and
displaced to higher tidal levels where they were unable
to bury. For the fast, shallow-burrowing, filter-feeding,
little-neck clam Protothaca staminea, there was high mortality at upper tidal levels but better survival for larger
individuals at lower levels. Post-earthquake surveys
suggested that there had been poor reproduction in this
species, and also in Clinocardium nuttallii, following the
quake and also little recruitment. Following the September
2010 and February 2011 earthquakes in Canterbury, New
Zealand, another little-neck clam Austrovenus stutchburyi
demonstrated a high tolerance to earthquake disturbance,
with changes in elevation ranging from À0.4 to +0.4 m
(Measures et al., 2011). These bivalves maintained their
EARTHQUAKE DISTURBANCES
209
after the quake, however, the original patterns of barnacle
distributions had reestablished, Fucus had returned to dominance, mussels had reestablished on rocks at lower tidal
levels, and the species diversity at MacLeod Island was
more diverse than it had been immediately post earthquake.
Generally, the effects on estuarine ecosystems of uplift
appear greater than those of subsidence, although relatively little attention has been paid to documenting the latter type of changes. In Prince William Sound, for example,
in areas where subsidence had occurred, the overlapping
of pre- and post-quake communities was observed, with
high intertidal snails found grazing among the submerged
terrestrial vegetation.
Wetlands
Coastal wetlands such as salt marshes are vulnerable to
earthquake damage and sea-level change since they represent a transition zone between tidal flats and uplands. Due
to land subsidence following earthquakes along the
Cascadia subduction zone approximately 300 years ago
and also in southern Chile (1960), coastal forests were
decimated and sedimentation from tsunami activity
resulted in the establishment of salt marshes in protected
locations with gently sloping shorelines and suitable sediment supplies (FitzGerald et al., 2008). The sudden relative sea-level changes that occur following an
earthquake, however, may not mimic models of climate
changes where the estimated rates of change are of the
order of millimeters to centimeters per year (Reed,
1990). In many areas, the natural recolonization of salt
marsh habitats following extreme events has been slow,
and intervention may become necessary to restore bird
habitats (unpublished data).
In the subtropics, following earthquake and associated
disturbances such as tsunami, salt marshes may be
replaced by mangroves, which are known to recover rapidly from other natural disturbances such as storms and
cyclones. Following the Boxing Day 2004 M w 9.1–9.3
Sumatra earthquake and subsequent Indian Ocean tsunami, Aceh Province soft-coast mangroves were assessed
as being more sensitive to disturbance than rocky headlands, with sandy coasts occupying an intermediate
position (Wong, 2009). Past and current records of
sea-level changes on soft coasts suggest that mangrove
forest resilience, where natural regeneration is expected
to take 10–15 years, allows this ecosystem to adapt to both
the incremental changes that are associated with global
change and the event-scale changes associated with earthquakes and tsunamis (Alongi, 2008). There have been
reports of extensive ecosystem damage, with 51–100 %
of mangroves destroyed in the Nicobar Islands following
the Sumatra 2004 earthquake and tsunami, with similar
damage to coral reefs (41–100 %) and to forests
(7–27 %) (Ramachandran et al., 2005). This damage,
however, is insignificant in comparison to the ecosystem
destruction produced in Indonesia over recent decades
by clearance for coastal development such as shrimp
farms (Idrus, 2009). Reports on the coastal protection
value of mangrove forests during the 2004 tsunami event
are mixed but, overall, suggest that they provided significant protection to landforms, either through the dissipation
of wave energy or through the pre-tsunami progradation of
shorelines, in several Indian Ocean countries. While some
studies indicate that mangrove forests can provide better
storm protection than concrete barriers, the effectiveness
will vary depending on location, previous history, and
presence of non-mangrove vegetation (Dahdouh-Guebas
et al., 2005). Also in the case of a large tsunami or storm
surge, coastal forests and dunes are generally believed
to have provided minimal hinterland protection, as
found during the devastating 2011 Tōhoku earthquakeinduced tsunami (Lavigne et al., 2007; Gomez et al.,
2010; Gomez, 2012).
Mudflat infauna
Shallow water estuarine mudflat habitats are exposed to
multiple environmental stressors, and, according to
Thrush et al. (2008), such communities can recover as
long as the recovery potential of the resident fauna
exceeds the disturbance effects. When this does not occur,
then the loss of species leads to habitat loss and fragmentation across landscapes. These types of changes have
been observed following earthquake events worldwide.
In shallow water soft sediments, the fauna is often dominated by bivalves which might be expected to have natural resistance to environmental perturbations. In Olsen
Bay, Prince William Sound, before the 1964 Alaska earthquake, there were five different species of clams, shellfish
resources for people and predators, representing different
feeding types; fast and slow burying species; and those
that bury to different sediment depths. Mortality patterns
after the 1964 Alaskan earthquake were species specific
and depended on the degree of sediment displacement
and bed uplift, which essentially raised or lowered the animals’ vertical distributions. High mortalities were
recorded in maximal uplift areas for butter clams
(Saxidomus giganteus) which, pre quake, were usually
buried at depths of 35 cm in the sediment (Baxter, 1971;
Hubbard, 1971). In places where the sediment had been
removed, shellfish were exposed on the surface and
displaced to higher tidal levels where they were unable
to bury. For the fast, shallow-burrowing, filter-feeding,
little-neck clam Protothaca staminea, there was high mortality at upper tidal levels but better survival for larger
individuals at lower levels. Post-earthquake surveys
suggested that there had been poor reproduction in this
species, and also in Clinocardium nuttallii, following the
quake and also little recruitment. Following the September
2010 and February 2011 earthquakes in Canterbury, New
Zealand, another little-neck clam Austrovenus stutchburyi
demonstrated a high tolerance to earthquake disturbance,
with changes in elevation ranging from À0.4 to +0.4 m
(Measures et al., 2011). These bivalves maintained their
EARTHQUAKE DISTURBANCES
209