climate change on UAE - Stockholm Environment Institute-US Center

Scientists have every reason to believe that, as
with the predicted terrestrial effects of global
<strong>climate</strong> <strong>change</strong>, impacts to seagrasses will be
great. Short and Neckles (1999) highlight a need
for more research directed toward the impact of
global <strong>climate</strong> <strong>change</strong> on seagrasses. Seagrass
habitats are influenced by sea temperature
regimes, tidal variations, salinity content,
changing water depths, as well as ocean carbon
dioxide content. Tidal height and tidal range
effects on available light, current velocities,
depth, and salinity distribution, are all factors
that regulate the distribution and abundance of
seagrasses.
These <strong>climate</strong> factors are all implicated in
expected regional <strong>climate</strong> <strong>change</strong>s. Organisms
in tropical waters are known to live much closer
to their upper thermal limits. An assumption
that follows is that as the waters of the Gulf reach
extreme limits of temperature and salinity, the
same would be true for the three seagrass species
that live in it. Change sea surface temperatures
could lead to altered growth rates and even
impair other physiological functions of the
plants like sexual reproduction or geographic
distribution. Temperature <strong>change</strong>s that lead
to increased eutrophication and <strong>change</strong>s in the
frequency and intensity of extreme weather
events indirectly affect seagrass ecosystems.
Numerous studies have shown an association
between seagrass distribution and water
depth (Short et al., 1999 cites the following:
Zimmerman and Livingston, 1976; Bay, 1984;
Averza and Almodovar, 1986; Dennison and
Alberte, 1986; Dawes and Tomasko, 1988; Orth
and Moore, 1988; Duarte, 1991). Sea level rise, as
it contributes to increased water depth, leads
to a subsequent reduction in light available for
seagrass growth. One study suggests that the
projected 50 cm increase in water depth due to
sea level rise over the next century could reduce
available light by 50%, which in turn may cause
a 30-40% reduction in seagrass growth and
productivity (Short and Neckles, 2002).
Changing tidal range is likely to exacerbate the
effects of increased water depth on seagrass
habitats; however, whether tidal range remains
the same but just shifts with sea level, or if sea
level rise actually influences high and low tide
levels is yet to be determined. Any decrease in
tidal range will decrease the amount of intertidal
exposure at low tide such that plant distribution
expands shoreward. In shallow waters, these
subtidal species may be able to expand inland
towards intertidal areas and continue to
thrive (Kentula and McIntire, 1986). Where
geomorphology or human infrastructure does
not permit successful ecosystem migration, the
UAE can expect a loss in seagrass areas.
3.4. Coral Reefs
Coral reefs are Abu Dhabi’s most diverse
marine ecosystem. The variety of life and the
complex interactions of reef organisms are of
major fisheries, scientific and tourism value to
the Emirate. Sea levels in the Arabian Gulf have
been near present levels for about 2000 years
(Lambeck, 1996), and have therefore provided
corals with a stable bathymetric environment
in which to develop into reefs (ADEA, 2006).
Corals are vulnerable to thermal stress and have
low adaptive capacity. Increases in sea surface
temperature of 1 to 3°C are projected to result
in more frequent coral bleaching events and
widespread mortality, unless there is thermal
adaptation or acclimatization by corals (IPCC,
2007). Coral bleaching and mortality appear
related to the frequency and intensity of ENSO
events in the Indo-Pacific region, which may
alter as a component of <strong>climate</strong> <strong>change</strong> (IPCC,
2007).
Since 1995, there has been a heat-induced
die-off of around 90 per cent of all coral in
the southern Gulf. In 1996 and 1998, the UAE
experienced two catastrophic coral bleaching
events associated with seawater temperature
anomalies. These prolonged higher-than normal
summer seawater temperatures (positive SST
temperature anomaly of over 2°C) led to the
catastrophic bleaching and death of a large
percentage of the previously living corals along
the length of Abu Dhabi Emirate. High seawater
temperatures have often been close to or may
have exceeded the physiological tolerance
limits.
The long-term prognosis for the survival of
coral reefs in the Emirates, if summer seawater
temperatures continue to rise, is not good.
In the past, poor development of reefs in the
southern Gulf has been attributed to high
Impacts, Vulnerability & Adaptation for
Coastal Zones in the United Arab Emirates
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