Soil Erosion (Cambridge (CIE) IGCSE Environmental Management): Flashcards
Exam code: 0680
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Define soil erosion.
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Define soil erosion.
Soil erosion is the removal of the top layer of soil, usually by wind or water.
How does overgrazing lead to soil erosion?
Overgrazing removes vegetation, leaving soil exposed and loose, so wind or water can carry it away.
Excessive irrigation can cause soil , which makes soil dry, crumbly and easier to erode.
Excessive irrigation can cause soil salinisation, which makes soil dry, crumbly and easier to erode.
How do leaves and branches reduce soil erosion?
Leaves and branches slow down rainfall before it reaches the ground, which reduces soil loss.
True or False?
Tree roots loosen soil, which makes it easier to erode.
False.
Tree roots bind soil together; without them, soil becomes loose and more likely to erode.
How does using machinery on slopes increase soil erosion?
Tractors and other machines disturb the soil, creating loose soil that can wash downhill quickly.
On steep slopes, fast-moving rainwater can remove soil in layers or create deep .
On steep slopes, fast-moving rainwater can remove soil in layers or create deep gullies.
True or False?
Leaving fields bare between harvesting and the next planting reduces erosion risk.
False.
Bare fields increase erosion risk, because no plant cover protects the soil from rain impact or holds it in place.
Define wind erosion.
Wind erosion is the removal of dry, loose soil by strong winds, common in dry climates or during droughts.
How does heavy rain cause water erosion on exposed land?
Heavy rain splashes soil particles loose and washes them downhill.
How does silting increase the risk of river flooding?
Silt builds up on the riverbed and reduces the depth of the river, so it floods more easily during heavy rain.
Suspended silt particles clog fish , which makes it harder for fish to breathe.
Suspended silt particles clog fish gills, which makes it harder for fish to breathe.
Define desertification.
Desertification is the change of land into desert-like conditions as soil loss leaves dry, infertile land that cannot support crops.
What can trigger a landslide on a hillside cleared of vegetation?
Heavy rain can saturate the loose soil, which then slides downhill.
How does soil erosion reduce crop yield?
With less topsoil, crops get fewer nutrients, and roots cannot spread deeply or absorb enough water.
Define malnutrition.
Malnutrition is when people lack essential nutrients in their diets.
Why can soil erosion lead to the displacement of people?
When land becomes unproductive and crops fail, families may have to move elsewhere, often through rural-to-urban migration.
True or False?
Soil erosion can reduce biodiversity.
True.
Soil erosion destroys habitats and removes vegetation, which leaves fewer food sources for wildlife.
What three aims do soil erosion strategies share?
Soil erosion strategies aim to slow down water flow, reduce wind speed and protect soil structure.
Define terracing.
Terracing is cutting a hillside into flat steps.
How does terracing reduce soil erosion on steep slopes?
Each step slows water moving downhill, which reduces surface run-off and gives water more time to soak into the soil.
Define contour ploughing.
Contour ploughing is ploughing across a slope, following the natural shape of the land.
Contour ploughing creates small that slow down water flowing downhill.
Contour ploughing creates small ridges that slow down water flowing downhill.
True or False?
Contour ploughing reduces the amount of water that soaks into the ground.
False.
Contour ploughing increases the amount of water that soaks into the ground by slowing run-off.
Define bunds.
Bunds are small embankments or raised barriers built along field edges.
How do bunds improve soil moisture for crops?
Bunds trap water and reduce run-off, which helps collect water for crops.
Define windbreaks.
Windbreaks are rows of trees, shrubs or fences planted to block strong winds.
True or False?
Windbreaks protect soil but give no benefit to crops.
False.
Windbreaks also protect crops from wind damage and create sheltered areas where soil retains moisture.
How does vegetation cover protect soil during rainfall?
Vegetation cover reduces the impact of raindrops on the soil.
Plant roots the soil, which holds it firmly in place.
Plant roots bind the soil, which holds it firmly in place.
Why should farmers leave crop residues on fields after harvesting?
Crop residues cover the soil after harvesting, so it does not lie bare.
How does adding organic matter reduce soil erosion?
Organic matter, such as compost or manure, improves soil structure, so the soil is more stable and less likely to break apart.
True or False?
Earthworms supported by added organic matter make soil drainage worse.
False.
Earthworms improve the soil's aeration and drainage.
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