Presentation on theme: "Rural Land Degradation Revision"— Presentation transcript:
1 Rural Land Degradation Revision Higher GeographyRural Land Degradation Revision
2 RememberYou must know the causes, consequences and solutions to rural land degradation in North America and in Africa (north of the equator).Make sure that you know some examples.
3 The Dust Bowl (Kansas, Oklahoma, North Texas) North AmericaThe Dust Bowl(Kansas, Oklahoma, North Texas)
4 Physical Causes of soil erosion Relief – lack of shelter (flat featureless plains)Climate – prolonged drought & strong winds after several years of moist weather weather and problems of tornadoes.Vegetation – destruction of natural vegetation (grassland) which has anchored soils.Sandy soils – often depleted of moisture.
5 Human Causes of soil erosion Overcultivation – during years with plenty of rainfall in the 1920s marginal grassland areas were ploughed to increase crop production.Monoculture – planting only wheat or cotton without use of fallowing or crop rotation to restore soil moisture / fertility.
6 Consequences (1)Environmental – Topsoil blown away in huge duststorms (or ‘black blizzards) – the remaining soil was barren and infertile and therefore unsuitable for crop production.
7 Consequences (2)Social and economic : Crop failure – lack of income for farmers – as soil becomes infertile, farms were abandoned with unemployment amongst farm workers.Communities broke up and local shops etc. were forced to close through lack of business.The region was depopulated, with migration to find work in other states eg: California.
8 SolutionsThe US Soil conservation service was set up and used the following methods:-Anchoring the soilShelter beltsFallowingDiversificationIrrigationReturn marginal areasContour PloughingStrip cultivation
10 Physical causes and effects of degradation Fall in the water table – caused by major drought and use of wells – roots can no longer reach moisture and therefore vegetation dies.More frequent droughts – perhaps related to Global Warming – leaves soil vulnerable to wind erosion. Droughts also cause a fall in the water table.Intermittent flash floods cause soil erosion.As vegetation dies roots can no longer anchor the soil which in turn is easily blown away.
11 Human causes of degradation Population growth – a demand for more food requires farming on marginal land.Increased demand for food has shortened the fallow period – ie: the land does not have time to recover or regenerate.Increased demand for firewood leads to deforestation.Water shortages has lead to the need for more wells, lowering the water table further.As the best land is used for cash crops, marginal land more vulnerable to erosion is ploughed to grow food.Overgrazing destroys the vegetation cover.Poor irrigation methods lead to evaporation of stagnant water leaving a salty infertile crust.
12 Consequences (1)Environmental: As vegetation is removed the roots are no longer able to bind the soil together – vulnerable to wind erosion – fertile topsoil is blown away.Land becomes infertile and barren / unproductive turning to desert (desertification).
13 Consequences (2) Social: People forced to migrate as land becomes unproductive.Conflict over land between herdsmen and farmers.Males migrate to work in cities leaving villages with social disruption.Food shortages lead to malnutrition and famine.This can result in movement to refugee camps and abandoned villages.
14 Consequences (3) Economic: As the land becomes unproductive, farm income falls.Incomes are no longer able to support the population.This results in dire poverty and a reliance in overseas aid.Interest on loads to aid survival results in long-term debt.
15 Solutions Restore vegetation cover Self-help projects Drought-resistant shrubs and grasses planted – help bind the soilTrees plantedBuild dams