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Preventing Soil Erosion
What is erosion?
Erosion is the process by which rocks and soil are transported from one location to another.
The material moved by erosion is called sediment
What causes erosion?
• Gravity pulls everything to the center of the Earth
• Gravity causes sediment, water and other material to move downhill, causing mudflows or landslides.
What causes erosion?
• Moving water is the main cause of erosion
• As water moves over the land, it carries sediment with it. This moving water is called run-off
The effects of soil erosion
• Soil erosion is a major problem when you are trying to farm on a steep slope.
• Gravity and water cause the surface of the soil to fall down slope away from farming plots.
• The surface of the soil is called topsoil.
The effects of soil erosion
• Topsoil is rich in nutrients that plants need to grow.
• Runoff removes the topsoil from the farmland making it difficult to grow healthy plants.
The effects of soil erosion
• Removing vegetation (grass, trees etc.) from the land will increase soil erosion.
• The roots helps absorb water and traps sediment from flowing away.
Africa and Soil Erosion
• Soil erosion in Guinea
• Soil erosion in Zimbabwe
Africa and Soil Erosion
• drought and then an intense rainy season causes wide spread soil erosion issues (3 to 4 cm/hour) (http://www.public.asu.edu/~mschmeec/rainsplash.html)
Africa and Soil Erosion• Overgrazing of livestock• Over-ploughing of farmland• Global warming – dry lands are more vulnerable
• Wind erosion in dry flat areas• Slash and burn agriculture – too much bare soil
• Poor – depend on Africa’s natural resources for survival – exploit and overuse the land as situation worsens
Desertification
Desertification -Process by which a geographic region becomes a desert. The change may result from natural changes in climate or by human activity
Effects of Soil Erosion in Africa
• Widespread hunger and poverty• Food riots – violence, political instability• Less educated youth• Migrating farmers – border conflict• Plant loss – leads to widespread flooding• Annual income lost in areas affected by desertification = $ 42 billion (World Bank)
• From 1997 – 2000, 60 million moved from Sub-Saharan Africa
African Farmers Face Critical Loss of Fertile Landby Jason Beaubien
NPR Podcast April 27, 2006
Preventing Soil Erosion
• Reforestation – when farmland is planted with trees to return it to its original forested condition to control erosion
Preventing Soil Erosion
• Composting – fertilize the soil with organic matter
Preventing Soil Erosion
• Contouring – planting crops across the slope to prevent erosion
Preventing Soil Erosion
• Interseeding – growing a cover crop into a standing cash crop
Preventing Soil Erosion
• Vetiver grass – roots grow 2-4 meters downward, forms tight clumps
by Christopher Thomas, Masonga/Samhutsa, Zimbabwe
Over the years, the population of the Masonga area has increased and farmers here have begun using for farming more and more of the woodlands that are a part of the catchment area of the Tamganda and Nyamtikwa rivers. The woodlands are located in very hilly areas; as more and more trees are removed for agriculture, soil erosion has increased. To prevent soil erosion, farmers have erected stone contour ridges, or terraces. Some of them have planted a grass along them indigenous to Mozambique, called vetiver grass. But soil erosion is still a problem in the area, especially in gardens planted along the rivers. Soil erosion not only makes it harder for farmers to grow crops, but it also makes the water of the Tanganide and Nyamtikwa rivers less pure. The local farmers, led by the agricultural officer and the district natural resource conservation group, have begun to address the problem by planting more and more vetiver grass each year and by replacing highly cultivated riverside gardens with fruit tree plantations, which require much less cultivation and cause less soil erosion.
Terracing
