Impacts of Climate Change on Agriculture - Climate Resilient Agriculture for Ensuring Food Security - page 66

temperature and precipitation regimes (Buol
et al. 1990 ). In tropical countries, where fertiliza-
tion level is not always adequate, the need for
fertilization will probably increase.
Sea-level rise, another predicted effect of
global warming, will cause increased fl ooding,
saltwater intrusion, and rising water tables in
agricultural soils located near coastlines. This is
particularly crucial in tropical countries such as
Bangladesh, with large agricultural regions and
high rural population located near current sea
level.

about 20 % of cultivated lands and 33 % of
irrigated agricultural lands worldwide are
affl icted by high salinity (Ghassemi et al. 1995 ).
In addition, the salinized areas are increasing at a
rate of 10 % annually; low precipitation, high
surface evaporation, weathering of native rocks,
irrigation with saline water, and poor cultural
practices are the major contributors to the increas-
ing soil salinity. In spite of the physiological
cause of ion toxicity, water defi cit, and/or nutri-
tional imbalance, high salinity in the root area
sternly inhibits normal plant growth and develop-
ment, resulting in reduced crop productivity or
total crop failure (Ghassemi et al. 1995 ).
Young seedlings and plants at anthesis appear
to be more sensitive to salinity stress than at the
mature stages (Lutts et al. 1995 ). Onions are sen-
sitive to saline soils, while cucumbers, eggplants,
peppers, beet palak, and tomatoes are moderately
sensitive. One of the most effective ways to over-
come salinity problems is the use of tolerant spe-
cies and varieties (Yilmaz et al. 2004 ). The
response of plants to increasing salt application
may differ signifi cantly among plant species as a
function of their genetic tolerance.

4.5.2 Erosion and Fertility

The warmer atmospheric temperatures observed
over the past decades are expected to lead to a
more vigorous hydrological cycle, including
more extreme rainfall events. Erosion and soil
degradation is more likely to occur. Soil fertility
would also be affected by global warming.
However, because the ratio of carbon to nitrogen
is a constant, a doubling of carbon is likely to
imply a higher storage of nitrogen in soils as
nitrates, thus providing higher fertilizing ele-
ments for plants, providing better yields. The
average needs for nitrogen could decrease and
give the opportunity of changing often costly fer-
tilization strategies.
Due to the extremes of climate that would
result, the increase in precipitations would prob-
ably result in greater risks of erosion while at the
same time providing soil with better hydration,
according to the intensity of the rain. The possi-
ble evolution of the organic matter in the soil is a
highly contested issue: while the increase in the
temperature would induce a greater rate in the
production of minerals, lessening the soil organic
matter content, the atmospheric CO 2 concentra-
tion would tend to increase it.

4.6 Extreme Weather Events

Most scientists believe that the warming of the
climate will lead to more extreme weather pat-
terns (heat waves, droughts, strong winds, and
heavy rains) such as:
• More hurricanes and drought.
• Longer spells of dry heat or intense rain
(depending on where you are in the world).
• Scientists have pointed out that Northern
Europe could be severely affected with colder
weather if climate change continues, as the
arctic begins to melt and send fresher waters
further south. It would effectively cut off the
Gulf Stream that brings warmth from the Gulf
of Mexico, keeping countries such as Britain
warmer than expected.
• In South Asia, the Himalayan glaciers could
retreat, causing water scarcity in the long run.
While many environmental groups have been
warning about extreme weather conditions for a

4.5.3 Salinity

Salinity is also a serious problem that reduces
growth and productivity of vegetable crops in
many salt-affected areas. It is estimated that