Land is a valuable resource and its fertility lies in the quality of the soil. Soil is formed by the weathering of rocks. It has many layers. Topsoil is the topmost layer and it is most fertile. The removal of this topsoil by various agents of erosion is known as soil erosion. Water, wind, glaciers and gravity are the agents of erosion. In the following article there are causes and consequences of soil erosion.
Soil erosion is when the soil is washed away by the wind or rain. Soil erosion is ordinary in areas with steep slopes, where trees have been cut down, in droughts when crops and other vegetation grow poorly and in rural areas which are overpopulated. Erosion reduces soil productivity by removing the most fertile topsoil. The Mediterranean region is particularly prone to erosion as it is subject to long dry periods pursued by heavy bursts of erosive rain, falling on steep slopes with fragile soils. Soil erosion is classified into different types depending on the agent which triggers the erosion activity. There are four types of soil erosion, Water Erosion, Wind Erosion, Glacial Erosion and Gravitational Erosion.
Causes of soil erosion:
Gradient of Slope:
When it comes to soil erosion gradient of the slope is a significant factor. There is direct relationship between erosion and gradient. The steeper the gradient, higher is the rate of erosion and vice versa. In water erosion, glacial erosion, and gravitational erosion this factor plays an important role.
Soil Properties:
Soil erosion depends on the physical and chemical properties of the soil as well. Different types of soil have different properties. In formative whether the soil is vulnerable to erosion by various agents of erosion or not, the texture, structure, water retention capability, etc. play an important role.
Water Flow:
In soil erosion Hydrological cycle plays a major role, especially the surface flow as well as underground flow. The gradient of soil erosion is determined by variation in the velocity and type of the flow. When it comes to water erosion this is the major factor and sometimes even in case of glacial erosion.
Climate:
Climate is one of the major causes of soil erosion. It determines the rainfall levels and wind velocity which in turn effect soil erosion. More rainfall means more surface flow, and more surface flow means more area susceptible to erosion by running water. Equally, if the wind speed is high, erosion will also be high and eroded material will be carried farther. In case of wind erosion and water erosion the climate factor plays an important role.
Human activities:
Human activities which have either directly or indirectly weakened the topmost layer of the planet are faulty farming systems, deforestation caused by overgrazing, clearance of land for agricultural purposes and construction, dam construction and diversion of the natural course of river, and mining activities. For instance, tree roots help in holding the soil together, and therefore depletion of vegetation cover is bound to make soil vulnerable to erosion by running water.
Consequences of Soil Erosion
Loss of fertility:
Movement of fertile top soil from one region to another reduces its fertility. Only infertile sub-soil is left behind when the top fertile soil is constantly removed from a region. Only sparse vegetation can grow in such a soil. This way, soil erosion gradually turns lush green areas into deserts.
Landslides in hilly areas:
Barren hills or hills with sparse vegetation are continuously uncovered to heavy rain falls. The top surface of rocky mountains or top soil of hills made loose by this. Rock pieces of various sizes or loosen soil from hills suddenly slide down the steep slope of mountains/hills due to soil erosion. This is known as landslide. It results in floods if these rock pieces and soil block the narrow river bed. People living in the downhill areas are sometimes killed by landslides.
Flash floods:
Lot of rain water is absorbed by the plants on the hilly land and keeps the top soil intact. But barren much rain water is not absorbed by hills with sparse plants and thus cannot keep the soil intact. Thus, heavy rains result in fast movement of water resulting in flash floods in lower areas causing tremendous losses to life and property.
Famines:
Only infertile sub-soil is left behind when the top fertile soil is constantly removed from a region. Its water holding capacity is reduced by the texture change of eroded soil. Crops cannot grow in such infertile, dry soil leading to shortage of food grains in the region. Eventually it can result in famine.
Silting of water reservoirs:
When top soil is washed away by water its deposition clogs drains, water channels, etc. Water is also polluted by it. The water level in them is lowered by problem of silting in water reservoirs and it eventually leads to shortage of power production by the hydroelectric power stations.
Developmental Activities:
because of developmental activities like human settlements, mining, dams, canals, roads, railways, airports, playgrounds and industries The productive area of grasslands, croplands and woodlands is fast reducing. Through increased productivity the loss is compensated but this definitely has a limit. 15.12.4. Control of Land Degradation.
Other Consequences:
- It causes a decrease in crop production and crop quality.
- Soil erosion decreases the moisture supply by soil to the plants for their growth. It also affects the activity of soil micro-organisms.
- It can be a safety hazard as the eroding land can lead to accidents and soil that shifts and gets deposited on roads and streets can make driving difficult.
- Soil eroded by water gets deposited on river beds, thus increasing their level and causing floods.
- The soil particles stay suspended in water, preventing light from reaching marine plants to allow the photosynthesis process and also retaining heat and raising the water temperature. The soil particles are also abrasive on fish and plant tissue and can kill them off.
- Sandy storms are caused by soil erosion via wind, which damage the crops. Further these sandy storms reduce the rainfall in particular area.
- It can lead to financial issues. People need expensive filtration methods to get drinkable water. Soil loss leads to crop failure and more financial loss.
Prevention of soil erosion:
- The practice of growing different crops at different times on the same land is called crop rotation. This keeps the topsoil covered with vegetation.
- Grow cover crops on farm land. When land is not being used during the off season, cover crops can help prevent soil erosion due to wind and rain.
- Apply mulch to maintain moisture and also help prevent soil erosion.
- Fertile soil supports vegetation. Loss of fertility results in loss of vegetation and this exposes the land to erosion. Fertility of soil can be increased by addition of natural and synthetic fertilizers.
- Construct surface runoff barriers, such as edging made of bricks or stones, can help prevent soil erosion by minimizing runoff.
- Slopes are more subject to soil erosion by running water. Growing trees on lands which have lost their vegetation is called reforestation.
- Fields are cut at right angles to the slope. This slows down the flowing water and allows it to irrigate the crops, as well.
- The most common method followed is the contour farming where the strips of crop are at right angles to the slope. Wind-strip cropping is when the strips of crop are place at right angles to the direction of wind.
- Covering the land with small plants and grasses helps the topsoil to remain in place as the roots of these plants bind with the soil particles.
- Water flowing speed and amount can be controlled with the dams. This will control the soil erosion of the river banks.
- Trees are planted across the wind direction to protect against the high velocity winds. These rows of trees are called shelter belts or wind breakers.
Video of Soil Erosion from youtube:
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