152 The impactsof climate change
resources. At the present time, it is estimated that in some parts of
Bangladesh saltwater extends seasonally inland over 150 km. With a
1-m rise in sea level, the area affected by saline intrusion could increase
substantially^9 although, since it is also likely that climate change will
bring increased monsoon rainfall, some of the intrusion of saltwater
could be alleviated.^10
What possible responses can Bangladesh make to these likely future
problems? Over the timescale of change that is currently envisaged it
can be supposed that the fishing industry can relocate and respond with
flexibility to changing fishing areas and changing conditions.It is less
easy to see what the population of the affected agricultural areas can do to
relocate or to adapt. No significant areas of agricultural land are available
elsewhere in Bangladesh to replace that lost to the sea, nor is there
anywhere else in Bangladesh where the population of the delta region
can easily be located. It is clear that very careful study and management
of all aspects of the problem is required. The sediment brought down by
the rivers into the delta region is of particular importance. The amount
of sediment and how it is used can have a large effect on the level of the
land affected by sea level rise. Careful management is therefore required
upstream as well as in the delta itself; groundwater and sea defences
must also be managed carefully if some alleviation of the effects of sea
level rise is to be achieved.
A similar situation exists in the Nile delta region of Egypt. The likely
rise in sea level this century is made up from local subsidence and global
warming in much the same way as for Bangladesh – approximately 1 m
by 2050 and 2 m by 2100. About twelve per cent of the country’s arable
land with a population of over seven million people would be affected by
a 1-m rise of sea level.^11 Some protection from the sea is afforded by the
extensive sand dunes but only up to half a metre or so of sea level rise.^12
Many other examples of vulnerable delta regions, especially in south-
east Asia and Africa, can be given where the problems would be similar
to those in Bangladesh and in Egypt. For instance, several large and low-
lying alluvial plains are distributed along the eastern coastline of China.
A sea level rise of just half a metre would inundate an area of about
40 000 km^2 (about the area of The Netherlands)^13 where over thirty mil-
lion people currently live. A particular delta which has been extensively
studied is that of the Mississippi in North America. These studies under-
line the point that human activities and industry are already exacerbating
the potential problems of sea level rise due to global warming. Because
of river management little sediment is delivered by the river to the delta
to counter the subsidence occurring because of long-term movements of
the Earth’s crust. Also, the building of canals and dykes has inhibited
the input of sediments from the ocean.^14 Studies of this kind emphasise