Vulnerability, Impacts and Adaptation of Coastal Zones to Global Change - Vulnerability of Coastal Ecosystems and Adaptation - page 140

triggered by climate change. The change in GMSL, or eustatic change,
is normally measured in relation to the center of the Earth and results
from a change in ocean water volume or in the volume of the oceanic
basins. Since the Industrial Revolution, the GMSL has increased by
about 20 cm. According to the IPCC AR5 report [IPC 13], during the
20th Century, the mean annual increase of the GMSL has been
1.7 mm, but since 1993 it has been between 2.8 and 3.6 mm. The
same report considers that probably in the period 2081-2100, the
GMSL will be 0.26 to 0.98 m higher than in 1986-2005.
On longer timescales, changes in the wave regime, resulting from
climate change, cause erosion and accretion along the coast, which are
variable at regional and local levels. Furthermore, the increase in
the sea surface temperature changes the distribution of species in the
medium and long term, leading to changes in the biodiversity of
coastal ecosystems. The increasing CO 2 atmospheric concentration
leads to an increase in the amount of CO 2 dissolved in seawater, where
it forms carbonic acid. This phenomenon, which is called the
acidification of the ocean, has the effect of decreasing the quantity of
carbonate, and has harmful consequences for marine biodiversity,
such as depressing metabolic rate and immune response in some
organisms, and causing coral bleaching. The combined effect of
increasing sea surface temperature and decreasing pH of the Earth's
oceans is very likely to have harmful consequences on the
physiological functions of numerous marine organisms.
Currently, the increase in GMSL is changing the frequency of the
most extreme sea levels during tropical and extratropical storms.
There are other potential impacts however. The rise in GMSL carries
significant risks for natural and human coastal systems at a regional
and local level, specifically a higher risk of flooding, erosion and
salinization of water resources and coastal agriculture soils. In the
long term, up to the end of the century, the increase in GMSL will
very probably become a major problem in low-lying coastal zones.
The situation will be particularly difficult for countries with a weak
capacity to adapt such as for example, small island developing states.
We can expect migratory movements from developing countries
where large populations are concentrated in coastal zones vulnerable