Geoscience Reference
In-Depth Information
one of the highest rates in the world. Using estimates of subsidence rate and global warm-
ing sea-level rise, the World Bank has estimated that by the end of the 21st century, the re-
lative sea level in Bangladesh could rise by as much as 1.8 m. In a worst-case scenario,
they estimated that this would result in a loss of up to 16 per cent of land, supporting 13
per cent of the population, and producing 12 per cent of the current GDP. Unfortunately,
this scenario does not take any account of the devastation of the mangrove forest and the
associated fisheries. Moreover, increased landward intrusions of salt water would further
damage water quality and agriculture.
Another example of a threatened coastline is the Nile delta, which is one of the oldest in-
tensely cultivated areas on Earth. It is very heavily populated, with population densities up
to 1,600 inhabitants per km
2
. Deserts surround the low-lying, fertile floodplains. Only 2.5
per cent of Egypt's land area, the Nile delta and the Nile valley, is suitable for intensive
agriculture. Most of a 50 km wide land strip along the coast is less than 2 metres above
sea level and is only protected from flooding by a 1-10 km wide coastal sand belt, shaped
by discharge of the Rosetta and Damietta branches of the Nile. Erosion of the protective
sand belt is a serious problem and has accelerated since the construction of the Aswan
dam in the south of Egypt. A rising sea level would destroy weak parts of the sand belt,
which are essential for the protection of lagoons and the low-lying reclaimed lands. These
impacts could be very damaging. About one-third of Egypt's fish catches are made in the
lagoons, and sea-level rise would change the water quality and affect most fresh-water
fish; valuable agricultural land would be inundated; vital, low-lying installations in Alex-
andria and Port Said would be threatened; recreational tourism beach facilities would be
endangered; and essential groundwater would be salinated. Many of these effects are pre-
ventable, as dikes and protective measures would stop the worst flooding up to a 50 cm
sea-level rise—although there may still be considerable groundwater salination and the
impact of increasing wave action could be serious.
The most important influence on the impact of sea-level rise on coastal regions is the rate
of change. At the moment, the predicted rise of about 50 cm in the next 100 years can be
dealt with if there is the economic foresight to plan for the protection and adaptation of
coastal regions. This then comes back to the development of regional economies and the
availability of resources to implement appropriate changes. If sea level rises by over 1 m
in the next 100 years, which is thought to be unlikely according to the IPCC, then human-
ity would doubtless have major problems adapting to it.
