Our natural environment comprises a number of elements that are affected in quantum by the presence of external forces like wind, water and ice. Soil, rock and sediments from river beds and mountainous terrain are displaced by these forces regularly, by the minute. While the force of gravity is the major influencing factor, burrowing animals and chemical or physical weathering are also responsible for erosion. Erosion occurs concurrently, with the slightest shift in velocity or movement of the force responsible. Wind erosion is a natural process, but can also be induced or magnified via indiscriminate land use, deforestation, unmonitored construction, overgrazing and urbanization.
What is Wind Erosion
Wind erosion means wind blowing away soil, sand or any substance that is light enough for the wind to carry it and deposit it at a different location. From a human perspective, wind physically removes the less dense, lighter soil constituents such as organic matter, clays, and silts thereby removing the most fertile part of the soil. This reduces the soil productivity and thus decreases potential soil productivity and increases economic costs.
There are primarily two types of wind erosion viz. Sweeping drift and Active drift. Sweeping drift is relatively gentle and causes loose, fine soil to go into suspension but with minimal development of drift banks. An active drift is more vigorous and involves the three particle movement processes (surface creep, saltation and suspension), and drift banks or blowouts. The ecosystem allows for a certain quantum of erosion; however, loss of soil in large quantities takes a long time to get replaced and causes damage to the delicate balance of nature. Conservative practices in agriculture for tilling and sowing are affected by wind erosion. The rate of wind erosion depends on precipitation, temperature, wind speed and soil and rock type.
Effects of Wind Erosion
- Wind erosion reduces the capacity of the soil to store nutrients and water, thus making the environment drier affecting the porosity and permeability of the surface.
- Detached and airborne soil particles break soil aggregate and lower infiltration rate. This results in surface runoff during the monsoons.
- Sand or dust traveling close to the ground can ruin entire crops (particularly millet or cotton seedlings in semi-arid zones), resulting in costly delays, reduced yields and loss in quality and market value of crops.
- Formation of spectacular dunes or mounds of sand which bury oasis or even entire villages when the wind blows.
- Soil erosion not only disturbs the balance between the soil structure and plant roots, but also disrupts terrace-cultivation in a major way. These geologic factors affect the well-being of natural vegetation, living organisms as well as human life.
Major Causes of Wind Erosion
- Wind velocity plays a very important role in the displacement of surface soil. Ecosystems with high-intensity winds are likely to be subjected to more erosion. Sediment and silt content on slopes are lost in the presence of strong winds. The resultant removal from one area and deposit in another .
- Construction of roads and buildings and wanton deforestation increased the rate of wind erosion. The wind is able to easily blow away the sediments and ground cover that has come loose due to human action. These actions also impact drainage patterns, embankments and soil compaction, leading to exposure of mineral soil.
- Heavy grazing and drastic changes in vegetation also magnify the rate of wind erosion. Slash and burn treatments and shifting cultivation not only expose the ground cover to greater wind erosion, but also affect the habitats of dependent living organisms. Increased human and animal activities make erosion by wind easier and damaging to the ecosystem.
Wind erosion is largely the result of many superimposed, interactive processes. Though wind erosion in some ways is said to be less destructive than the erosive influence of water, when the wind carries sand, it has a much greater frictional component as every grain acts like a cutting tool. The result of prolonged period of wind erosion is visible in most desert regions where the bases of rocks or cliffs have been sandblasted and eroded into spectacular rock formations and sculptures. The wind could not lift the fine grains of sand very high, but in places where it has been able to do its work, it has left an indelible mark.
Wind erosion is a serious problem in many parts of the world. It is worse in arid and semiarid regions. Wind erosion in the United States is most widespread on agricultural land in the Great Plains states. A prolonged dry spell in the 1930s resulted in the infamous black blizzards or Dust Bowl culminated in dust storms and soil destruction of disastrous proportions inflicting great hardships on the people and the land. Even today, according to the US Department of Agriculture, it is estimated that the total annual cost of erosion from agriculture stands at about US$44 billion per year. The impact of wind erosion on the environment and economy is large and it affects not only the site from which soil is removed but the air in which it is transported, and the site at which it is deposited.