Soil
erosion is an urgent problem because new soil forms very slowly;
2.5 centimeters (1 inch) of topsoil may take anywhere from 20 to
1200 years to form. Soil erosion also has a number of serious
environmental impacts. For instance, soil particles attach to
pesticides. Transported to nearby waterways, these
pesticide-laden particles may contaminate fish and other aquatic
organisms, which, in turn, may be passed to birds and human
consumers in the food chain. Sediment deposited in waterways
also increases flooding, destroys breeding grounds of fish and
other wildlife, and increases the need for dredging harbors and
rivers. The World Resources Institute estimates the offsite
damage from soil erosion in the United States is over $10
billion a year.
Since 1880
one third of the top soil in the United States has been lost to
erosion, according to the U.S. Soil Conservation Service.
Unfortunately, soil erosion continues today. The U.S. Department
of Agriculture estimates about 1 billion metric tons of topsoil
were lost from U.S. farmland in 2000. Although, that is less
than the 1.45 billion metric tons lost in 1985, the current rate
of erosion remains too high. The average rate of erosion on U.S.
farmland is approximately seven times greater than soil
formation, a situation that is clearly unsustainable. Should
erosion continue, the U.S. agricultural system could experience
substantial declines in productivity.
Unfortunately, little information is available on soil erosion
rates throughout the world. Scientists currently estimate that
approximately one-third of the world's cropland topsoil is being
eroded faster than it is being regenerated.
Soil
erosion is especially rapid in many developing nations. In
China, for example, the Yellow River annually transports 1.6
billion metric tons of soil from badly eroded farmland to the
sea. In India, the Ganges carries two times that amount.
Overall, the Worldwatch Institute estimates that 24 billion
metric tons of topsoil are eroded from the world's cropland each
year. At this rate, the world loses about 7% of its cropland
topsoil every ten years.
Livestock