Fichas
ecosystems - desertification
Fichas del conjunto (23)
- 1What is desertification?When the climate of a dry region becomes even drier. Vegetation dies or is eaten by grazing animals and the soil Becomes vulnerable to soil erosion.
- 2Where is the Sahel?It is located in the North of Africa, it goes from the west coast in Mauritania to the east coast in Ethiopia and Eritrea. It is south of the Sahara desert.
- 3What are the causes of desertification?Long periods of drought .
Climate change.
Deforestation.
War.
Change of rainfall pattern.
Overgrazing.
Soil erosion.
Overpopulation.
Overcultivation. - 4What are the effects of desertification?If trees are cut down then there is no shade for the soil, so the sol heats up more which can lead to soil erosion.
Increased population means that there is more demand for water, firewood, food etc.
You get a famine.
Soil loses its vegetation cover, which leads to less humus and nutrients in the soil. - 5What is the Great Green Wall and how does it stop desertification?It began in Senegal.
It is a multistate project including all the countries in the Sahel. 700km long; 15kn wide. Stretching coast to coast through 11 states.
First seed planted in 2008.
It is an international cooperation.
Stops desertification, because of the biodiversity of species; prevents soil erosion as roots keep the soil together; every species using different nutrients in soil.
They grow fruit trees, which provide the local areas with fruit and veg, which improve their diet so they can be more healthy. - 6What are the trees in Ethiopia used for from deforestation?Use of scaffolding to build houses.
Fire wood to cook food and to provide light/heat.
Tooth brushes.
Houses.
Household items.
Ladders.
Building market stalls. - 7How do goats and baboons in Ethiopia cause desertification?In Ethiopia there are too many goats and baboons which cause overgrazing, because the goats eat the grass and the baboons scratch at the ground to get animals and roots from the soil.
- 8What are the physical processes which cause desertification?Annual rainfall totals are gradually falling.
The rain in the wet season is unpredictable and can be very heavy, causing soil erosion.
Less vegetation means less water is returned to the atmosphere by evapotranspiration. - 9What are the Human processes which cause desertification?Farmers allow their goats to overgraze shrubs, and vegetation is killed.
Trees and shrubs are burnt to clear land for farming or urbanisation.
Trees are cut down for firewood for cooking.
Commercial farms use the land so intensively that the soil is quickly worn out. - 10When farmers allow goats to overgraze, what is the effect on the vegetation?There will be less vegetation = less water returned to atmosphere by evapotranspiration.
- 11When farmers allow goats to overgraze, what is the effect on the soil?The surface of the soil becomes baked in the heat. Moisture in the soil is drawn upwards and evaporates from the surface.
- 12When farmers allow goats to overgraze, what are the effects on the climate?There will be a reduction in rainfall.
- 13How can rocks prevent gully erosion?The farmer is placing rocks (known as stone bunds) across the gully to prevent gully erosion. The rocks help stop this because when it rains the rocks stop the soil from getting washed away.
- 14What is infiltration? Will it increase or decrease during desertification?The movement of water from the ground surface into the soil.
Decrease. - 15What is interception? Will it increase or decrease during desertification?When water is prevented from falling directly to the ground. For example, the canopy of leaves in a forest intercepts the rainfall.
Decrease. - 16What is overland flow? Will it increase or decrease during desertification?The flow of water across the ground surface.
Increase. - 17What is the evaporation of soil moisture? Will it increase or decrease during desertification?When the soil is heated, the moisture in the soil is drawn upwards and evaporates from the surface.
Increase. - 18What is transpiration? Will it increase or decrease during desertification?Water loss from plants through pores in the leaves.
Increase. - 19What is gully erosion? Will it increase or decrease during desertification?It is when heavy rainfall erodes the soil, so on steeper slopes the power of the water picks up and carries soil particles and smaller rocks; it uses these to erode downwards into the soil in a process known as gully erosion. It is a common problem in areas suffering from desertification.
- 20Desertification means that soil erosion, vegetation dying will take place. How does this happen?There will be a decline in infiltration and interception which will cause the soil to become dry and erode; overland flow will increase and will wash away the nutrients in the soil, this can cause gully erosion. The evaporation of soil moisture will mean the soil will dry up and the transpiration of plants will mean plants will die. This can effect the rainfall by reducing it, because there will be less moisture in the air.
- 21Why does rainwater harvesting prevent desertification?Because it helps to maintain soil moisture by encouraging infiltration, collects and uses the rainwater. Also it helps to prevent soil erosion from taking place. (see diagram in book of how it works).
- 22How can we manage/ conserve the soil from desertification?Tree-planting schemes (afforestation).
Building small rock dams (bunds)
Collecting rainwater from the roofs of buildings.
Building terraces on steeper slopes.
Building stone lines on gentle slopes.
Planting grass strips along the contours of gentle slopes. - 23How do bunds work?Run-off is slowed by the bunds, giving more time for infiltration.
Rainwater infiltrates and recharges soil moisture.
Any soil that has been eroded by run-off is trapped by the bunds. Top soil and organic matter (e.g. leaf litter) is deposited here.
Bunds are placed 10-25m apart.
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- GCSE (Theme 2) Geography Fichas sobre ecosystems - desertification, creado por Rebecca Smith el 13/06/2016.
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- Rebecca Smith
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