Impacts of Climate Change on Agriculture - Climate Resilient Agriculture for Ensuring Food Security - page 80

especially the most productive farmland, would
be lost as a result of a 1.5 m sea-level rise.
Island nations, particularly low-lying coral
atolls, have the most to lose. The Maldives
Islands in the Indian Ocean would have one-half
of their land area inundated with a 2 m rise in sea
level (UNEP 1989 ).
In addition to direct farmland loss from inun-
dation, it is likely that agriculture would experi-
ence increased costs from saltwater intrusion into
surface water and groundwater in coastal regions.
Deeper tidal penetration would increase the risk
of fl ooding, and rates of abstraction of groundwa-
ter might need to be reduced to prevent recharge
of aquifers with sea water.
Further indirect impacts would be likely as a
result of the need to relocate both farming popu-
lations and production in other regions. In
Bangladesh, for example, about one-fi fth of the
nation's population would be displaced as a result
of the farmland loss estimated for a 1.5 m sea-
level rise. It is important to emphasize, however,
that the IPCC estimates of sea-level rise are much
lower than this (about 0.5 m by 2090 under the
business-as-usual scenario).
The rise in sea levels and tropical cyclones are
major threats to rice production in the Asian
mega deltas especially in Vietnam, Bangladesh,
and Myanmar.

4.13 Increasing Ocean

Acidifi cation

Although it has gained less mainstream media
attention, the effects of increasing greenhouse
emissions - in particular carbon dioxide - on the
oceans may well be signifi cant. The oceans are
taking up atmospheric CO 2 , but this uptake
results in chemical reactions which make the
oceans more acidic. Oceanic acidifi cation may
disrupt important marine ecosystems by interfer-
ing with the ability of marine organisms to
develop carbonate and by dissolving carbonate
sediments.
As explained by the US agency, the National
Oceanic and Atmospheric Administration
(NOAA) (Fig. 4.11 ), the basic chemistry of ocean
acidifi cation is well understood.
These are the three main concepts:
• More CO 2 in the atmosphere means more CO 2
in the ocean.
• Atmospheric CO 2 is dissolved in the ocean,
which becomes more acidic.
• The resulting changes in the chemistry of the
oceans disrupt the ability of plants and ani-
mals in the sea to make shells and skeletons of
calcium carbonate, while dissolving shells
already formed.

Fig. 4.11 Ocean acidifi cation; consumption of carbonate ions impede calcifi cation (Source: Pacifi c Marine Environment
Laboratory, NOAA)