Summary
Summary Cambridge International AS and A Level Geography second edition - arid environments
- Module
- Arid environments
- Institution
- CIE
An indepth summary of the Sahel case study for CIE A2 geography students
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-
- Sahel desert runs parallel to the southern
edge of the Sahara Desert from the west coast
of the east coast of Africa
- average width of the Sahel is 500km
- due to its proximity to the Sahara, it is prone
to desertification
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RAINFALL :
Abidjan has around 1700mm of rainfall per year having a ↳
tropical rainforest climate. There are peaks of rainfall in
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both June and a smaller peak within October. This is due
to the ITCZ moving north in the early months of the RAINFALL :
year, bringing rain to the south, and moving receives 20mm of rainfall per year
southwards slightly in the latter months; however, This is because it is a hot arid environment located at around
→ 15°N of the equator. During the summer months of June -
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Abidjan remains south of the ITCZ so continues to
have precipitation. August, the sun will be directly over the Tropic of Cancer
.
(23degrees south), and so the ITCZ will migrate southwards.
TEMPERATURE : But due to the location of Gao, as seen on the ITCZ map on
Abidjan is on the coast, located 5° north of the the top left, it will still receive little rainfall due to the
equator. The average length of the day in Abidjan '
maximum north of the ITCZ still remaining beneath.
remains constant throughout the whole year, varying
is
by around 25 minutes in the summer to the winter. ARID
This is due to the tilt of the earth. The equator has
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a smaller surface area and therefore heats up B. because
found on the
.
at a faster rate than the poles, also there is less RAINFALL : descending
atmosphere to pass through. limb of the
receives more rain days and heavy summer precipitation from June M No
Hadley cell
n
30
.
- .
when the ITCZ is furthest north
- this brings rainfall to the area as the maritime air mass is 60
'
.
go
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dominant. TEMPERATURE
Located 15° north of the equator. Due to lack of cloud cover ,
TEMPERATURE the intense solar radiation heats the ground, then warms the air
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located 11° north above it increasing daytime temperature. At night, this heat
of the equator, dissipates into the atmosphere, cooling the region down.
"
having a semi
"
arid climate due . . . .
Aridity results from the presence of dry, descending air.
to its subtropical Therefore, aridity is found mostly in places where
anticyclonic conditions are persistent, as is the case in the
location.
regions lying under the anticyclones of the subtropics.
, ⑧BL⑧⑤G§→E§→⑥fG••*a.IM#I-BAA-HA--H----Eouerraiumtiu# ion
- rising populations have forced farmers to increase
the amount of land utilised for arable farming
pop gqr•☒#H - this has lead to the cultivation of marginal areas
Improved medical care resulting in a reduced death rate, and high birth rates has lead to (edge of Sahara)
rapid growth in the Sahel region - these are not a viable option in terms of sustained
- in countries such as Burkina Faso and Mali, populations are increasing by a rate at 2.5% crop production and as a result, cultivating them
per year (while at the same time food production increases by only 1% per year) accelerates the process of desertification
- population estimates place population figures for the Sahel at almost 140 million by 2020
- a disturbing projection is that projected populations of around 300 million are given for
2050
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overgrazing - during the 20th century, some farmers in the
Sahel moved away from traditional techniques
- overgrazing puts pressure on certain grazing areas, and began growing cash crops such as cotton
particularly around wells, lakes and rivers
- the concentration of herds in these areas result in
kNlMRANl and rice
- this monoculture often combined with
vegetation being stripped down to its roots, leaving soil
inappropriate farming techniques has rendered
exposed
the soil infertile in many areas
- compaction of soil by trampling reduced the infiltration
capacity of the soil and increases runoff
④forestation
'
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- urbanisation has led to an increased demand for
firewood
- since 1990, 90% of forests have been cleared in the Ethiopian highlands
- large areas of forest are cut down and the wood is - deforestation removed the binding effect of tree roots and prevents the trees from
often turned into charcoal for ease of transport reducing wind speed
- this process is extremely inefficient and half of the - the shortage of fire wood means that more and more families are having to resort
energy of the wood is lost during conversion to animal dung and crop residues for their domestic energy requirements
Eg. - the dung and crop residues would normally be used as a fertiliser so the soil is
further degraded as it is deprived of essential nutrients
- in the long term this will affect crop yields
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