Transcript Land Degradation in North Africa
Higher Geography
Land Degradation in North Africa
Case Study: The Sahel
Introduction
When soil is bare, it can easily be blown away by the wind or washed away by rain.
This is called
soil erosion
.
If a lot of soil is eroded it becomes less and less fertile ( called degradation
desertification
.
) until the land cannot be farmed and it becomes useless, usually as a result of human activities. This is
Location
The Sahel runs parallel to the southern edge of the Sahara Desert from the west coast to the east coast of Africa.
The average width of the Sahel is 500km.
Its proximity to the Sahara is one of the principal reasons it is prone to desertification.
Climate
Total annual rainfall is low, ranging between 200mm in the northern Sahel to 500 mm in southern Sahel.
Rainfall is unreliable and highly variable.
Rainfall occurs in a very intense tropical downpour, creating high potential
erosivity .
ITCZ
The rainfall pattern in the Sahel region is a result of the
Intertropical Convergence Zone (ITCZ)
which migrates across the region each year.
During the dry season,
Tropical Continental air
the Sahara.
is dominant along with dry
Harmattan winds
blowing across
Natural Environment
Range of species and vegetation decreases Soil depth decreases and soil erodibility increases Total rainfall decreases and rainfall reliability decreases Soil moisture decreases due to increase in sand content
Traditional way of life
Most people are herders of sheep, camels or goats. They move from area to area to find enough water and grazing land.
They are called
nomadic herders
.
Causes of rural land degradation in the Sahel
The causes of rural land degradation in the Sahel cannot be attributed to any one factor, but an interaction of a wide range of both
physical
and
human
variables.
Physical Factors
Although the Sahel should get 100 500mm of rain each year, the rainfall is very unreliable.
Some years are wetter than average and some are much dryer.
Physical
Desertification
Although the Sahel should get 100 500mm of rain each year, the rainfall is very unreliable.
Some years are wetter than average and some are much dryer.
Physical
With very little rain, few crops can grow so there were few roots to hold the soil together.
The soil is eroded until some of the land is turned to desert.
At the same time, the soil dries out and is easily blown or washed away.
Unpredictable Climate
Burkina Faso’s cotton crop destroyed by flash floods in 1994, 1996 & 1997. 67, 000 tonnes of emergency food aid were required by Burkina Faso to deal with food shortages caused by drought.
Human Factors
Improved medical care resulting in a reduced death rate, coupled with high birth rates means that rapid
population growth
is occurring in the Sahel.
In countries such as Burkina Faso and Mali populations are increasing by at a rate of 2.5% per year (while at the same time food production increases by only 1% year)
Overcultivation
Rising populations have also forced farmers to increase the amount of land utilised for arable farming.
This has led to the cultivation of marginal areas (edge of the Sahara).
These are not a viable option in terms of sustained crop production and as a result cultivating them accelerates the process of desertification.
Overgrazing
Places pressure on certain grazing areas particularly around wells, lakes and rivers.
The concentration of herds in these areas results in vegetation being stripped down to its roots, leaving soil exposed.
Compaction of the soil by trampling reduces the infiltration capacity of the soil and increases run off.
Deforestation (1)
Since 1990, 90% of forests have been cleared in the Ethiopian Highlands.
Deforestation removes the binding effect of tree roots and prevents the trees from reducing wind speed.
The shortage of fire wood means that more and more families are having to resort to animal dung and crop residues for their domestic energy requirements.
Deforestation (2)
The dung and crop residues would normally be used as fertiliser so the soil is further degraded as it is deprived of essential nutrients.
In the long term this will affect crop yields.
Urbanisation
Urbanisation has led to an increased demand for firewood.
Large areas of forest are cut down and the wood is often turned into charcoal for ease of transport.
This process is extremely inefficient and half of the energy of the wood is lost during conversion.
Growth of cash crops
During the twentieth century some farmers in the Sahel moved away from traditional techniques and began growing cash crops such as cotton and rice.
This monoculture often combined with inappropriate farming techniques has rendered the soil infertile in many areas.
Physical consequences of land degradation
The increasing frequency of drought periods, the farming of marginal areas along the northern boundary of the Sahel and deforestation have led to the southwards expansion of the Sahara desert.
In Sudan the Sahara has advanced by 100km in 17years.
In the last 50 years, 65 million hectares of the Sahel have turned to desert.
Desertification is now estimated to be spreading at a rate of 1.5 million hectares per year in the Sahel.
Physical Consequences
Rills and gullies Loss of topsoil Salinisation
Social and economic consequences of land degradation
Malnutrition and starvation – The failure of crops year after year leads to starvation and death eg: Sudan and Ethiopia (mid 1980’s).
Cash crop farming can also lead to malnutrition.
Migration
Many people have now migrated away from the Sahel.
This has led to the loss of traditional farming techniques and in some cases (eg: northern Niger) a demographically imbalanced rural population.
Dependence on external support
Where the effects of land degradation and drought have been the most acute, people have come to rely on food and other aid sent from other countries, eg: the band aid campaign of 1983.
This can lead to
over dependency
external help.
on
Access to education and healthcare
In many Saheian countries such as Burkina Faso, education and health care must be paid for and therefore the loss of income brought about by the failure of crops and herds may mean that individuals have their schooling interrupted and individuals go untreated when ill.
Solutions to RLD
Solution 1 : Irrigation
There have been several expensive irrigation schemes where rivers have been dammed and reservoirs formed.
The water from the reservoirs is then taken by canals to irrigate large areas of farmland.
The Gezira Scheme
In Sudan the Gezira scheme allows one million hectares of land to be irrigated using water from the White Nile and Blue Nile.
The Gezira Scheme
The Gezira Scheme
Farmer income has increased considerably Wheat is grown for food Cotton is grown for export Farmers can have two harvests a year
Advantages
Crops grow even though there is little rain 150 000 people are now employed there.
The Gezira Scheme
The reservoir flooded land which had previously been used by local farmers Only helped people in one small area of the country
Disadvantages
Very expensive
Solution 2 - Terraces
There are over 200 000 kilometres of terraces in Ethiopia.
They help trap water, stopping it from washing the soil away.
Solution 3 – Afforestation
Planting new trees helps to bind the soil, and also provides shade, windbreaks, nutrients and fuel for families.
Depending on the species planted the trees may also provide nuts and fruit for humans and animals.
Tree planting needs to be sustainable if it is to be successful in the Sahel.
Solution 4 – Stone lines
In Burkina Faso and other Sahel countries local people have built lines of stones along contours on their sloping farmland.
These stone lines trap run-off after heavy rain so that the soil is not washed away.
Crops also grow much better in the deeper soil behind the stones.
This method requires a lot of labour but is cheap and simple to work.
Organisations such as Oxfam and Tear Fund, have used this method very effectively. In some cases crop yield has increased by as much as 50%.
Other methods (1)
Managed grazing areas Reduced herd sizes
Other methods (2)
Education Fuel efficient stoves