T18+notes

T18+notes - Soil Erosion (Topic 18) A nation that destroys...

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Soil Erosion (Topic 18) A nation that destroys its soils, destroys itself! (F.D. Roosevelt, 1937) Soil erosion is the most serious problem affecting the sustainable production of food and fiber. About 80% of the world's agricultural lands suffer moderate to severe erosion; an additional 10% suffer slight to moderate erosion. It is estimated that 54% of U.S. rangelands are over-grazed resulting in enhanced soil erosion and decreased productivity. Worldwide, about 12 million hectares of arable land are destroyed and abandoned annually because of nonsustainable farming practices. Total cultivated land is currently 1.5 billion hectares. Worldwide, about 75 billion metric tons (Mg) of soil are eroded annually: ± 2/3 eroded by water & 1/3 eroded by wind The annual cost of erosion is estimated at $44 billion in the U.S.; $400 billion worldwide (1995). Depending on soil forming factors, soils can sustain a loss of 1-10 Mg/ha/yr without losing significant productivity. A 1 mm (1/32 inch) thickness of soil over one hectare weighs approximately 12 Mg.
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T18+notes - Soil Erosion (Topic 18) A nation that destroys...

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