Transcript Drought and desertification anna

Drought and desertification in the
Sahel
Starter
What is drought?
• Drought is a period below average rainfall.
• Drought is period of unexpectedly low
rainfall.
• Therefore, what is considered to be a
drought may vary widely throughout the
world e.g. in an equatorial climate it could
mean 6 days without rain/in Libya it could
mean less than 180 mm in a year.
Introduction: Drought and
desertification in the Sahel
• The Sahel is a band of semi-arid land to the south of the
Sahara desert. This region includes the region of Darfur, in
Sudan, that we studied last lesson.
• The rainfall in the region is variable and falls mainly during
July and August.
• Rainfall levels used to be higher but now drought is
occurring.
• In wetter times, the Sahel became more populated. Trees
were cut down for fuel and cattle were introduced and the
vegetation became overgrazed and depleted.
• Now lower levels of rainfall are being experienced and
desertification is taking hold.
Causes of Drought
Watch the video clip and note down the
causes of drought in the Sahel.
Causes:
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The Sahel is the most drought prone region of the
world and has experienced below average levels of
rainfall for the last 30. Reasons for this are:
The area has experienced long periods of high
pressure. Clouds don’t form in these conditions and so
it does not rain.
Long periods of high temperatures have led to more
evaporation than precipitation.
Reduced vegetation as a result
deforestation/overgrazing means that more water
vapour is lost from the system reducing the potential
for rain.
Global warming could be making drought more
frequent in the Sahel.
Effects:
• People are forced to migrate wetter areas
or to refugee camps where there might be
water available
• Land that was fertile becomes eroded and
turns into desert (desertification)
• Livestock is not able to survive in these
conditions and many die
• Crops fail and this leads to hunger and
famine
Desertification
• Desertification is the process by which
productive land becomes dry and useless.
• There is no one reason we can point to as
the cause of desertification, but rather a
combination of climate and our own
mistakes, ignorance and actions.
Causes of desertification
• Desertification is triggered mainly by the overuse
of land and unsustainable agricultural practices
(overcropping, overgrazing, poor irrigation and
deforestation) which lead to a loss of natural
vegetation and healthy soil.
• An expanding human population and urban
living area as well as the low level of priority
placed on environmental protection efforts also
contributes.
Desertification Threat
While deserts expand and contract naturally, it's important to
understand that desertification is different from this natural cycle.
Desertification is also far from being a new global crisis: Ancient
empires, including Sumeria, Babylon and Rome, were dealt its
debilitating effects.
• Currently, the most endangered regions are near the world's five main
deserts, including the Sonoran Desert, (Mexico and the US), the
Atacama Desert (South America); the Kalahari Desert (Southern Africa);
most of Australia; and the large desert mass made up by the Sahara,
Arabian, Great Indian, Taklimakan, and Gobi deserts.
• Desertification is a looming crisis in Africa where almost 70 percent of
the continent is arid or semi-arid land. More than 30 percent of North
America is comprised of arid or semi-arid lands, with about 40 percent
of the continental United States at risk for desertification
The 1930s Dust Bowl
Watch the video clips to see the
causes and impacts of desertification
• http://www.youtube.com/watch?v=8mUhtF
e2ApE – Impact Senegal
• http://www.youtube.com/watch?v=DGGctK
4aWGg&feature=related – Animation –
grazing and desertification
• http://www.youtube.com/watch?v=icG7Olaum8&feature=autoplay&list=PL94647A6
99E6BB886&lf=results_video&playnext=1Desertification in Niger
Task
• Complete the flow diagram task to explain
the causes and affects of desertification.
How are the people of
the Sahel region of
Africa adjusting to a
changing and variable
climate?
Sahel: Reducing Drought and
Desertification
Measures and effectiveness of measures:
• Much of the aid provided to the region is the form of food donations
(emergency aid), which undoubtedly save lives but does nothing to
address people's vulnerability to future shocks.
• Irrigation and reservoirs have been constructed: These have
supplied water to some areas although only 4%, of a possible 20%, of
land has been irrigated. They have also served as breeding grounds
for disease carrying insects e.g. the tse tse fly.
• Bore holes and wells have been dug to access underground
sources of water again, this has provided more water to some
regions although increases in wells have led farmers to attempt to
raise larger herds on the land leading further over-grazing
• Governments in this region have introduced policies of afforestation
(planting new forests)
Suggestions for water management to ensure
food and water security in the future
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The Sahel has a tropical
climate is characterized by a
very long dry season and very
high temperatures reaching at
times 35 - 40° C in some
places. Thus, solar energy is
great, yet, it is under-exploited.
Access to water can be
improved by using solar
powered pumping stations that
pump water to areas of need in
order to irrigate crops, water
livestock or provide potable
water. This requires MEDCs to
provide the skills and
technological know-how
required and to support with
grants for equipment.
Watch the following video:
• http://www.youtube.com/watch?v=NgU1hzQc4YA
Draw a table to show the advantages and disadvantages of:
a) In the short‐term, provide food aid and temporary water supplies to prevent
suffering.
b) Improve water supplies by building large reservoirs and drilling deeper wells.
c) Conserve water in local small‐scale schemes e.g. ‘magic stones’ (stone walls)
in Burkina Faso.
d) Encourage sustainable farming practices (using locally‐made tools, not
costly machines).
e) Provide drought‐resistant seed such as millet (northern Nigeria), including
GM crops.
f) Tree planting schemes to reduce soil erosion (e.g. in Mauritania).
g) International action to reduce the causes of
global warming.
Scheme
Short term food aid and
temporary water supplies
Improve water supplies by
building large reservoirs
and drilling deeper wells
Conserve water in local
small‐scale schemes e.g.
‘magic stones’
Encourage sustainable
farming practices
Provide drought‐resistant
seed
Tree planting schemes
International action to
reduce the causes of
global warming.
Advantage
Disadvantage
Q - To what extent have drought and
desertification contributed to war in the
Darfur region of Sudan?