164 The impactsof climate change
money, although they may be much more cost-effective ways of coping
with future change in water resources than attempting to develop major
new facilities.^31
In summary, what are the likely effects of global warming on water
supplies? Firstly, the current vulnerability of many communities to water
shortage should be noted. This is especially true of arid and semi-arid
regions where the increasing demands of human communities mean
that droughts, even for short periods, are more disastrous than before.
Vulnerability is well demonstrated in many areas of the world where the
amounts of groundwater extraction greatly exceed its replenishment – a
situation that cannot continue forvery long into the future. Because of
population growth these vulnerabilities will increase and will exacerbate
the negative effects of global warming.
Secondly, climate change because of global warming will result in
large changes in water supplies in many places. Although the present state
of knowledge regarding regional and local climate change does not allow
scientists to identify precisely the mostvulnerable areas, they are able
to indicate the sort of area which will be most affected. Such areas are
those arid and semi-arid areas with reduced rainfall leading to greater
aridity and even desertification; continental areas where decreased sum-
mer rainfall and increased temperature result in a substantial loss in soil
moisture and much increased vulnerability to drought; and areas where
increased rainfall could lead to a greater incidence of floods. The chang-
ing pattern of climate extremes, especially droughts and floods, will be
the cause of most of the problems. It is also the case that regions such
as southeast Asia that are dependent on unregulated river systems are
more sensitive to change than regions such as western Russia and the
western United States that have large, regulated water resource systems.
Thirdly, some of the adverse impact of climate change on water supplies
can be reduced by taking appropriate alleviating action, by introducing
more careful and integrated water management^32 and byintroducing
more effective disaster preparedness in the most vulnerable areas.Impact on agriculture and food supply
Every farmer understands the need to grow crops or rear animals that are
suited to the local climate. The distribution of temperature and rainfall
during the year are key factors in making decisions regarding what crops
to grow. These will change in the world influenced by global warm-
ing. The patterns of what crops are grown where will therefore also
change. But these changes will be complex; economic and other factors
will take their place alongside climate change in the decision-making
process.