Unsustainable agricultural practices contribute to soil erosion.
"A nation that destroys its soils destroys itself," warned President Franklin D. Roosevelt in 1937. These words proved prescient: a 2006 study from Cornell University found that soil is eroding 10 to 40 times faster than it is replenished, resulting in the annual degradation of an area the size of Indiana. One inch of soil takes 1,000 years to form, but can wash or blow away in seconds. Since 99.7 percent of human food comes from cropland, soil erosion poses an environmental and public health issue. Does this Spark an idea?
Geological Erosion
Geological soil erosion is a natural process that takes place over millions of years. Bare soil is an anomaly in nature, as soils are usually covered by natural vegetation. In geological erosion, also called natural or background erosion, rain fall and wind gradually wash or blow the top layer of soil away but the natural vegetation keeps the erosion rate slow, allowing new soil to form through the weathering of parent rock material. Geological erosion is generally equal to or less than the rate of soil production.
Accelerated Erosion
Accelerated soil erosion is caused by human activities, such as agriculture, overgrazing or unsustainable cultivation. Accelerated soil erosion removes soil much faster than it can be formed. When human activity removes the protective, natural vegetative growth and residue from the top layer of soil, the bare ground is "vulnerable to removable by wind or water," according to Agaware. Over the last 40 years, accelerated erosion has resulted in the loss of 30 percent of the world's arable land.
Water Erosion
There are four types of water erosion. Rainsplash erosion takes place when raindrops fall on bare soil hard enough to splashes soil into the air and displace it. Any running water then carries the soil away and redeposits it. When enough water from rain or melting snow runs across the surface, it can take uniform sheets of soil from sloping land, called sheet erosion. Rill erosion takes place when enough rain falls to create rivulets of water that carve "small yet well-defined channels" into the land, according to the Ontario Ministry of Agriculture. When the rills grow large enough to interfere with farm machinery, the process is called gully erosion. Gully erosion can cause the loss of significant amounts of topsoil and subsoil, which are often redeposited in a lake or ocean.
Wind Erosion
When soil is stripped of its natural vegetative cover, it become susceptible to wind erosion. If the wind blows with enough force, it can pick up the topsoil and carry it great distances. Exposed areas with no windbreaks, areas suffering from drought and frozen soil surfaces are especially vulnerable. Along with loss of soil, wind erosion can cause public health problems because it "increases the amount of dust carried by wind, which not only acts as an abrasive and air pollutant but also carries about 20 human infectious disease organisms, including anthrax and tuberculosis," according to Cornell University.
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