Regional Impacts - Climate Resilient Agriculture for Ensuring Food Security - page 91

et al. ( 2004 ) described the implications of the
IPCC's SRES scenarios for a river runoff projec-
tion for 2050 using the HadCM320 climate model.
These experiments indicate a signifi cant decrease
in runoff in the north and south of Africa, while the
runoff in East Africa and parts of semiarid sub-
Saharan Africa is projected to increase. However,
multi-model results show considerable variation
among models, with the decrease in northern
Africa and the increase in East Africa emerging as
the most robust responses. There is a widespread
in projections of precipitation in sub-Saharan
Africa, with some models projecting increases and
others decreases. Projected impacts should be
viewed in the context of this substantial
uncertainty.
A specifi c example is the southwestern Cape,
South Africa, where one study shows water sup-
ply capacity decreasing either as precipitation
decreases or as potential evaporation increases.
This projects a water supply reduction of 0.32 %
per year by 2020, while climate change associated
with global warming is projected to raise water
demand by 0.6 % per year in the Cape Metropolitan
Region. With regard to the Nile Basin, there is no
clear indication of how Nile River fl ow would be
affected by climate change, because of uncer-
tainty in projected rainfall patterns in the basin
and the infl uence of complex water management
and water governance structures.
Responses to rainfall shifts are already being
observed in many terrestrial water sources that
could be considered possible indicators of future
water stress linked to climate variability. In the
eastern parts of the continent, interannual lake
level fl uctuations have been observed, with low
values in 1993-1997 and higher levels (e.g., of
Lakes Tanganyika, Victoria and Turkana) in
1997-1998, the latter being linked to an excess in
rainfall in late 1997 coupled with large-scale
perturbations in the Indian Ocean. Higher water
temperatures have also been reported in lakes in
response to warmer conditions.
Impacts of climate change on growing periods
and on agricultural systems and possible liveli-
hood implications have been examined. A recent
study based on three scenarios indicates that crop
net revenues would be likely to fall by as much as

5.1 Africa

• Food insecurity worsening and number of
people at risk from hunger increasing.
• Agricultural production severely compromised
due to loss of land, shorter growing seasons,
and more uncertainty about what and when to
plant. By 2020, yields from rainfed crops could
be halved in some countries, and by 2100, net
revenues from crops could fall by 90 %.
• General decline in most subsistence crops
such as sorghum in Sudan, Ethiopia, Eritrea,
and Zambia; maize in Ghana; millet in Sudan;
and groundnuts in Gambia.
• Fish stocks already compromised will be
depleted further by rising water temperatures
and other physical and ecosystem changes.
Threats of inundation for coast of East Africa;
coastal deltas, such as the Nile; and degrada-
tion of marine ecosystems and other physical
and ecosystem changes.
• Grassland degradation, with widespread
drying and desertifi cation, particularly in the
Sahel and southern Africa.
• Forests face deforestation, degradation, and
increase in forest fi res.
In Africa, the IPCC ( 2007 ) projected that climate
variability and change would severely compromise
agricultural production and access to food. This
projection was assigned “high confi dence.”
Africa's geography makes it particularly
vulnerable to climate change, and 70 % of the
population relies on rainfed agriculture for their
livelihoods. Tanzania's offi cial report on climate
change suggests that the areas that usually get
two rainfalls in the year will probably get more
and those that get only one rainy season will get
far less. The net result is expected to be that 33 %
less maize - the country's staple crop - will be
grown (FAO Newsroom 2006 ).
Water is one of several current and future criti-
cal issues facing Africa. Water supplies from riv-
ers, lakes, and rainfall are characterized by their
unequal natural geographical distribution and
accessibility and unsustainable water use. Climate
change has the potential to impose additional pres-
sures on water availability and accessibility. Arnell