The impacts ofsea level rise 153the importance of careful management of all activities influencing such
regions, and the necessity of making maximum use of natural processes
in ensuring their continued viability.
We now turn to The Netherlands, a country more than half of which
consists of coastal lowlands, mainly below present sea level. It is one
of the most densely populated areas in the world; eight of the fourteen
million inhabitants of the region live in large cities such as Rotterdam,
The Hague and Amsterdam. An elaborate system of about 400 km of
dykes and coastal dunes, built up over many years, protects it from the
sea. Recent methods of protection, rather than creating solid bulwarks,
make use of the effects of various forces (tides, currents, waves, wind
and gravity) on the sands and sediments so as to create a stable barrier
against the sea – similar policies are advocated for the protection of
the Norfolk coast in eastern England.^15 Protection against sea level rise
next century will require no new technology. Dykes and sand dunes will
need to be raised; additional pumping will also benecessary to combat
the incursion of saltwater into freshwater aquifers. It is estimated^16 that
an expenditure of about twelve thousand million dollars (US) would be
required for protection against a sea level rise of 1 m.
The third type of area of especial vulnerability is the low-lying small
island.^17 Half amillion people live in archipelagos of small islands and
coral atolls, such as the Maldives in the Indian Ocean, consisting of
1190 individual islands, and the Marshall Islands in the Pacific, which
lie almost entirely within 3 m of sea level. Half a metre or more of sea
level rise would reduce their areas substantially – some would have to
be abandoned – and remove up to fifty per cent of their groundwater.
The cost of protection from the sea is far beyond the resources of these
islands’ populations. For coral atolls, rise in sea level at a rate of up to
about half a metre per century can be matched by coral growth, providing
that growth is not disturbed by human interference and providing also
that the growth is not inhibited by a rise in the maximum sea temperature
exceeding about 1–2◦C.^18
These are some examples of areas particularly vulnerable to sea level
rise. Many other areas in the world will be affected in similar, although
perhaps less dramatic, ways. Many of the world’s cities are close to sea
level and are being increasingly affected by subsidence because of the
withdrawal of groundwater. The rise of sea level due to global warming
will add to this problem. There is no technical difficulty for most cities in
taking care of these problems, but the cost of doing so must be included
The overall impact of globalwarming
So far, in considering the impact of sea level rise, places of dense
population where there is a large effect on people have been considered.
There are also areas of importance where few people live. The world’s