Impacts of Climate Change on Agriculture - Climate Resilient Agriculture for Ensuring Food Security - page 79

modifi cation of sea defenses is relatively low or
nonexistent. Regarding crop productivity, vulner-
ability is clearly greatest where large sea-level
rise occurs in conjunction with low-lying coastal
agriculture. Many major river deltas provide
important agricultural land owing to the fertility
of alluvial soils, and many small island states are
also low lying. Increases in mean sea level
threaten to inundate agricultural lands and sali-
nize groundwater in the coming decades to centu-
ries, although the largest impacts may not be seen
for many centuries owing to the time required to
melt large ice sheets and for warming to pene-
trate into the deep ocean.
The potential sea-level rise associated with
melting of the main ice sheets would be 5 m for
West Antarctic Ice Sheet (WAIS), 60 m for East
Antarctic Ice Sheet (EAIS), and 7 m for Greenland
Ice Sheet (GIS), with both the GIS and WAIS
considered vulnerable. Due to the possible rate of
discharge of these ice sheets, and past maximal
sea-level rise (under similar climatic conditions),
a maximum eustatic sea-level rise of approxi-
mately 2 m by 2100 is considered physically
plausible, but very unlikely.
Water expands when heated and sea levels are
expected to rise due to climate change. Rising sea
levels will also result as the polar caps begin to
melt. Rising sea levels is already affecting many
small islands. The World Watch Institute reports
that “the Earth's ice cover is melting in more
places and at higher rates than at any time since
record keeping began” (March 6, 2000). Rising
sea levels will impact many coastlines, and a
large mass of humanity lives near the coasts or by
major rivers. Analysis by the World Wildlife
Fund has found that many cities are unprepared
for climate change effects such as rising sea
levels.
CO 2 -induced warming is expected to lead to
rises in sea level as a result of thermal expansion
of the oceans and partial melting of glaciers and
ice caps, and this in turn is expected to affect
agriculture, mainly through the inundation of
low-lying farmland but also through the increased
salinity of coastal groundwater. The IPCC esti-
mate of sea-level rise above present levels under

the business-as-usual scenario is 9-29 cm by the
year 2030 with a best estimate of 18 cm and
28-96 cm by 2090 with a best estimate of 58 cm
(Pearch and Bjorkman 1983 ).
Preliminary surveys of proneness to inunda-
tion have been based on a study of existing con-
toured topographic maps, in conjunction with
knowledge of the local “wave climate” that varies
between different coastlines. They have identi-
fi ed 27 countries as being especially vulnerable
to sea-level rise, on the basis of the extent of land
liable for inundation, the population at risk, and
the capability of taking protective measures
(UNEP 1989 ). It should be emphasized, however,
that these surveys assume a much larger rise in
sea levels (1.5 m) than is at present estimated to
occur within the next century under current
trends of increase of GHG concentrations. On an
ascending scale of vulnerability (1-10), experts
identifi ed the following most vulnerable coun-
tries or regions: 10, Bangladesh; 9, Egypt and
Thailand; 8, China; 7, western Denmark; 6,
Louisiana; and 4, Indonesia.
The most severe effects on agriculture are
likely to stem directly from inundation. Southeast
Asia would be most affected because of the
extreme vulnerability of several large and heavily
populated deltaic regions. For example, with a
1.5 m sea-level rise, about 15 % of all land (and
about one-fi fth of all farmland) in Bangladesh
would be inundated, and a further 6 % would
become more prone to frequent fl ooding (UNEP
1989 ). Altogether 21 % of agricultural produc-
tion could be lost.
In South, Southeast, and East Asia, about
10 % of the regional rice production, which is
enough to feed 200 million people, is from the
areas that are susceptible to 1 m rise in the sea
level. Direct loss of land combined with less
favorable hydraulic conditions may reduce rice
yields by 4 % if no adaptation measures are
taken, endangering the food security of at least 75
million people. Saltwater intrusion and soil sali-
nization are other concerns for agricultural
productivity.
In Egypt, it is estimated that 17 % of national
agricultural production and 20 % of all farmland,