What is Soil Erosion and Degradation
Soil erosion and degradation means wearing off of the topsoil by natural forces of wind and water. It is naturally occurring continuous process. It may be an extremely slow process that may go unnoticed or it sometimes may occur at an alarming rate. Reduced crop production and lower surface water quality reflect soil erosion. In last 150 years, almost half of the topsoil is lost.
While erosion is a natural process but human activities are speeding up the process by 10-40 percent globally. Deforestation, intensive agricultural practices, urban sprawl and climate change are among the common factors that are accelerating soil erosion.
The soil is considered a non-renewable resource, while technically it is a renewable resource. Because it takes many years to form a centimeter of soil, this makes it almost irreplaceable. The soil is a complex mixture, covering most of the land surface ranging from few centimeters to several meters deep. The soil is always changing as water comes and goes. Water, the wind, and gravity move in an out of the soil particles. But even though the soil changes occur, but the composition of soil layers remain almost the same in a human lifetime.
Causes of Soil Erosion and Degradation
The most common human activities that increase soil erosion are described below:
In undisturbed forests, the soil is protected by layers of humus and leaf litter. These layers absorb the impact of raindrops and form a protective mat over the soil. Deforestation can increase erosion rates due to exposure of mineral soil and removal of humus and litter layers. Removal of vegetation cover, which binds the soil together, causes more soil available for surface runoff.
Conversion of the natural ecosystem to pastures does not cause any damage to the land initially. But when it is practiced for many years it can adversely affect the soil causing high erosion rates and loss of topsoil and nutrients. It also reduces land cover which enables wind and water erosion and land compaction. This change makes it difficult for the plants to grow and water penetration becomes difficult which harms soil microbes, as a result, severe land erosion occurs.
Unsustainable agricultural practices are the biggest contributor to increasing the soil erosion rates globally. Tillage practice on agricultural lands breaks the soil up into smaller particles is the primary factor. Soil becomes more and more available for transfer by wind erosion by mechanized agricultural equipment and deep ploughing. Other factors affecting soil quality are mono-cropping (growing only one crop year after year on the same land), usage of pesticides and fertilizers that kill beneficial microbes which bind the soil particles, and surface irrigation (the irrigation practice in which water is applied on the soil surface by gravity).
Roads and Urbanization
Urbanization severely affects the erosion process. Land denudation by removing vegetation cover, changing drainage patterns, soil compaction during construction and then covering the land by impermeable layers of concrete or asphalt, all of them contribute to increased surface runoff and increased wind speeds.
Effects of Soil Erosion
Polluted and clogged waterways
Soil that is eroded from the land with fertilizers and pesticides washed off into rivers, streams, and other waterways. These in turn forms sediments in the waters and damage the quality of marine and freshwater and threatens the life that depends on them.
Arable land destroyed
Arable land means a land which is capable of being ploughed and used to grow crops. Many practices used in sowing and ploughing of crops can cause loss of topsoil and make agriculture difficult.
Erosion caused by deforestation can initiate increased flood rates. Land which is converted into a pasture or crop field from forests or another natural landscape is less able to absorb water, which makes floods more common.
Prevention and Remediation of Soil Erosion and Degradation
The most effective method to prevent erosion is to increase the vegetation cover on soil, thus preventing wind and water erosion. Leaving unploughed land strips between ploughed ones, known as strip cropping, also help reduce erosion. By making sure that the soil is rich in humus, that is, plants are always growing on the soil, avoiding overgrazing, conserving wetlands, rotating crops, practicing minimum or no-tillage, soil conservation can be ensured. Using mixed-cropping instead of mono-cropping is also considered significant measure reducing erosion.