Presentation on theme: "Land Degradation in North Africa"— Presentation transcript:
1 Land Degradation in North Africa Knox AcademyHigher GeographyLand Degradation in North AfricaCase Study:The Sahel
2 IntroductionWhen soil is bare, it can be easily blown away by the wind or washed away by rain.This is called soil erosion.If a lot of soil is eroded the land cannot be farmed and it becomes a desert.This is called desertification.
3 LocationThe 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.
5 ClimateTotal 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.
6 ITCZThe 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 is dominant along with dry Harmattan winds blowing across the Sahara.
7 Natural Environment Range of species and vegetation decreases Soil depth decreases and soil erodibility increasesTotal rainfall decreases and rainfall reliability decreasesSoil moisture decreases due to increase in sand content
8 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.
12 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.
15 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.
16 Desertification Physical DesertificationSome years are wetter than average and some are much dryer.Although the Sahel should get mm of rain each year, the rainfall is very unreliable.PhysicalWith 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.
17 Human FactorsImproved 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)
18 OvercultivationRising 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.
19 OvergrazingPlaces 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.
21 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.
22 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.
23 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.
24 Growth of cash cropsDuring the 20th C 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.
25 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.
26 In Sudan the Sahara has advanced by 100km in 17years. FactsIn the last 50 years, 65 million hectares of the Sahel have turned to desert.In Sudan the Sahara has advanced by 100km in 17years.Desertification is now estimated to be spreading at a rate of 1.5 million hectares per year in the Sahel.
27 Physical Consequences Rills and gulliesLoss of topsoilSalinisation
28 Social and economic consequences of land degradation P.102 – 103Make notes on the 3 impacts.
29 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.
30 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.
31 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 campaigns of 1985 and 2005.This can lead to over dependency on external help.
32 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.
34 Solution 1 : IrrigationThere 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.
35 The Gezira SchemeIn Sudan the Gezira scheme allows one million hectares of land to be irrigated using water from the White Nile and Blue Nile.
37 The Gezira Scheme Advantages Farmer income has increased considerably Wheat is grown for foodCotton is grown for exportFarmers can have two harvests a yearAdvantagespeople are now employed there.Crops grow even though there is little rain
38 Only helped people in one small area of the country The Gezira SchemeThe reservoir flooded land which had previously been used by local farmersOnly helped people in one small area of the countryDisadvantagesVery expensive
39 Solution 2 - TerracesThere are over kilometres of terraces in Ethiopia.They help trap water, stopping it from washing the soil away.
42 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.
45 Solution 4 – Stone lines (Magic stones) p.104 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.
50 Other methods (1) Managed grazing areas Reduced herd sizes Education Fuel efficient stovesADD NOTES ON THE FOLLOWING
51 Other methods (2) http://www.youtube.com/watch?v=tDWS6AzEkE0 (ethiopia learning from other farmers) excellentMicro damsMicro basins
52 Past Paper 2006 In pairs Answer Q2 part (a) (i) (ii). Part (i) 6 marks Part (ii) 8 marks
53 Past Paper 2006(a) (i)Description could include the following points:the pattern shows constant fluctuationsfrom 1950 until about 1970 rainfall is above averageafter 1970 rainfall is consistently below average.6 marks
54 Past Paper 2006 (a)(i) Answers might include: During drier periods – soil will dry out – plants die – hence no root systems to protect the soil. The soil can easily be blown awayIt is often the most fertile topsoil which is affectedIf a heavy rain storm falls unprotected soil is easily washed awayReference might also be made to human responses – eg during periods of above average rain, cropping and animal husbandry boundaries can be extended into previously dry areas – when a climatic reverse occurs the resulting overcropping/ overcultivation can lead to considerable degradation.Award up to 2 marks for detail regarding erosion processes by wind or rain.Assess out of 4 4 marks
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