Human-Environment
Interaction
Desertification of the Sahel
► The
Sahel in Arabic means “shore of the
desert.”
► It is a narrow band of dry grassland that
runs east to west on the southern edge of
the Sahara.
► Since the 1960s, the desert has spread into
this band of dry grassland.
Desertification of the Sahel
Desertification of the Sahel
► This
shift of the desert is called
desertification, which is an expansion of
dry conditions to moist areas that are next
to deserts.
Desertification of the Sahel
►Human Causes
 Overgrazing
of Desertification
 Farming
 Increasing Population
Desertification of the Sahel
► Farming
increases this
process. When
farmers clear land to
plant crops, they
expose the soil to the
wind, which can cause
erosion. In addition,
irrigation increases
salt levels which
prevent the growth of
vegetation.
Desertification of the Sahel
Animated
Clip
Desertification of the Sahel
► Food
and water
shortages lead to
malnutrition,
famine, disease
and high death
rates.
Desertification of the Sahel
Harming the Environment in Nigeria
► Another
environmental issue
has to do with the
discovery of oil in
Nigeria in 1956.
Rich oil deposits in
the Niger Delta
made Nigeria one of
Africa’s wealthiest
countries.
Harming the Environment in Nigeria
► The
damage caused by foreign oil
companies and the Nigerian government
has been severe. More than 4,000 oil
spills have been recorded in Nigeria over
the past four decades.
Shell oil spill in Nigeria
in 2004.
Harming the Environment in Nigeria
► Cleanup
operations have been slow
► Oil
spills have caused fires, acid rain, massive
deposits of soot
► Resulted
in high rates of respiratory disease
Controlling the Nile
Egypt has always depended
on the water of the Nile River.
The two main tributaries of
the Nile River are the White
Nile and the Blue Nile.
Lake Victoria is the source of
the White Nile and the Blue
Nile.
The Nile River has a total
length of 4,160 miles from
source to sea – the longest
river in the world.
Controlling the Nile
Sahara
Desert
The fertile
areas surrounding
the Nile River
Controlling the Nile
► Throughout
history, Egyptians have
experienced cycles of floods and droughts.
Controlling the Nile
► To
solve these
problems, they built
the Aswan High
Dam, which was
completed in 1970.
The dam gives
farmers a regular
supply of water.
Facts
• The Aswan High Dam is 2.2 miles long and
354 feet high.
• The Soviet Union helped the Egyptian
government to build the dam.
• The Aswan High Dam has 12 turbines which
generate over 10 billion kilowatts of electricity
every year.
• Construction started on the dam in 1960 and
it was completed in 1971.
• 30,000 Egyptian people worked day and night
to build the Aswan High Dam.
• Lake Nasser was created behind the Aswan
High Dam. It is the largest artificial lake in the
World (348 miles in length). It is named after
the former President of Egypt.
Controlling the Nile
The Advantages of the Aswan Dam
Controlling the Nile
Electricity for homes and
industry:
Generators in the dam are used to
generate electricity that is taken to homes
and industries by pylons.
Pylons
Aluminium and copper
smelting industry
Controlling the Nile
Flood control:
Control of flooding is
carried out by the dam.
By keeping so much
water back in Lake
Nasser, the River Nile
rarely floods the
surrounding farmland
any more.
Controlling the Nile
New farmland created:
The act of keeping
back the water
from the River Nile
has lowered its
level, effectively
creating new
farmland by the
river sides. This is
also less prone to
flooding.
Controlling the Nile
Irrigation water for
nearby farmland:
Development of irrigation
channels from Lake Nasser,
takes water from the
reservoir to the nearby
desert to make farmland for
watering crops. The
electricity pumps the water
there.
Controlling the Nile
Fish stocks in Lake
Nasser:
Also creates tourism via game fishing.
Fish live in the lake and can
be fished more easily by those
fishermen who used to fish in
the River Nile. This improves
their livelihoods and
fish stocks can be replaced
more easily.
Controlling the Nile
The Disadvantages of the Aswan Dam
Controlling the Nile
► Because
of the dam, the Nile River no longer
deposits its rich silt on the farmland.
Controlling the Nile
Water-borne diseases increase:
As the water in both the reservoir and irrigation channels is
contained and, in a lot of places, static, this promotes the
build-up of water snails which carry the disease bilharzia.
Many other diseases also increase as they are not 'flushed
away' by the flow of the River Nile.
Controlling the Nile
► Now,
farmers must rely on expensive
artificial fertilizer to enrich the soil.
Controlling the Nile
Land lost from flooding of Lake Nasser:
Although there were some land gains from the building
of the dam, there were much more losses behind the
dam where the land was flooded to make the reservoir
of Lake Nasser. Many people were moved and made
homeless as well as losing their farmland.
The temples of Abu Simnel had to
be moved.
New
Location
Old
Location
Controlling the Nile
Evaporation from Lake Nasser is very high:
This is an extremely hot area of the world.
Evaporation from Lake Nasser is very high as a
consequence and this means a lot of water is lost.
Controlling the Nile
►
Water pollutants –
treating municipal water
can often be too
expensive for the more
impoverished areas along
the Nile. Unfortunately,
these cities dump
polluted water,
containing human waste,
back into the Nile
untreated. This causes
disease to spread.
Controlling the Nile
► Also,
year-round
irrigation has
resulted in a rising
water table in
Egypt. As a result,
salts from deep in
the earth have
decreased the
fertility of the soil.