Dust Storm

Causes and formation

The storms occur under certain circumstances when prolonged drought causes the soil surface to lose moisture and there is a co-occurrence of strong winds. ⁵   

Field observations and wind tunnel laboratory research explain the physical process of sand and dust blowing under the force of wind and moving over the land surface. “When the wind force reaches the threshold value, the sand and dust particles are transported from the surface and start to move.” Specifically, storms or dust consisting of particles are held in earth surface by their own weight and some inter-particle bonding. When the wind speed is slow, there will be no indication of motion. But when the wind force reaches the threshold value, a number of particles will begin to vibrate. As the wind speed is increasing, a number of particles will be ejected from the surface into the airflow. When these injected particles impact back on the surface, more particles are ejected and thus start a chain reaction. Ejected sands and dust can be transported by wind to other places. ⁶  

North America

One of the best known and best documented dust storms happened in human being history is the Great North American Dust Bowl in the early 20th century.During the World War I, the price of wheat was high and Allied troops encouraged farmers to grow more wheat by plowing and seeding areas in the Canadian prairies and the Great Plains in the U.S., which were formally used only for grazing. Those behaviors changed the structure of those lands and after years of yields, livestock were returned to graze the areas, which pulverized the unprotected soil. In 1930s, strong winds blew the soil into hugs clouds and serious dust storms happened in the following years resulting in a severe health hazard. ⁷

The dust bowl in Canada mainly happens in the Prairie Provinces of Manitoba, Saskatchewan and Alberta. A number of factors such as topography, climate, vegetation cover and soil types generate ideal conditions for dust storms in those regions. During  the “Dust Bowl” period of the 1930s, some areas were stripped entirely of topsoil, which amounted to about 2,000 t/ha, and almost 20% of the improved farmland of the Prairie Provinces were eroded by wind. ⁸

Severe dust storms occurred in the US during the 1930s and more recently in 1999, several notable sand and dust storms happened in western Texas and southeastern New Mexico. It is believed that serious drought and land misuse resulted in the Dust Bowl over large areas in the Great Plains in the U.S.. The Dust Bowl got its name on April 15, 1935, the day after Black Sunday and lasted about a decade.  Because of the Dust Bowl, a large number of farmland became useless and hundreds of thousands of people were forced to leave their homes.  ⁹

Australia

Dust storms are also often reported in Australia.  Central eastern Australia is a major global source region for atmospheric dust. Frequent dust storms have occurred since the late-1950s.  In 1982-1983, El Niño attacked Eastern Australia which brought exceptionally dry weather. As vegetation dried off, the topsoil was loosened. There were small dust storms reported in 1982. And in 1983, a strong, but dry cold front crossed Victoria and blown away and caused a severe dust storm. ¹⁰

China

The combination of over plowing and overgrazing to satisfy rapidly growing food demand causes severe dust storms in China. China has plowed large areas of the northwest, much of that is highly erodible and hard to recover. In addition to the direct damage from over plowing and overgrazing, the northern half of China is drying out water resources by over pumping. Those trends   result in the largest dust storms ever recorded.   Dust storms affect the cities of northeast China – threatening public health and reducing visibility.

There are also increased complaint from Korea and Japan, which are regularly impacted by the dust storm moving from China. ¹¹ In April 2001, scientists at the National Oceanic and Armospheric Administration laboratory in Boulder, Colorado, reported that a huge dust storm from northern China had reached the US. ¹²

Impact

Dust storm has a number of environmental and social impact.

Environmental impact:

• The main environmental impact of sand storm is the soil loss. Nutrients, organic matter and thus soil fertility are exported along with the dust storm generation. As a result, the original place where dust storm generated lost agriculture productivity.
• During the dust transportation, young plants are lost and result in a loss of productivity.
• Dust particles have a radioactive effect on climate through reflection and absorption of solar radiation. It can lead to severe cooling days or hot days depending on dust particles’ properties and in what part of the atmosphere they are found.
• When the dust storm moves close to populated areas, it contributes to urban air pollution and threatens public health. People with asthma and other respiratory disorders who breathe in dust particles will suffer.

Social Impact:

• The degradation of land can result in the reduction of livestock forage, availability of fuelwood material, biodiversity, water availability and yields of farmland. 
• The loss of land resources can increase the spread of poverty and hunger. 
• Migration in search for food and relief and environmental refugees can pose pressure on neighborhood areas and cause enormous social problems.

Footnotes

^{1 8 9}:Victor R. Squires,International Dryland Consultant, Chapter 2, "Physics, Mechanics and Processes of Dust and Sandstorms". Adelaide University, Australia,UNCCD project.

^{2 3 4 5 6}:Victor R. Squires,International Dryland Consultant, Part II, "The Great North American Dust Bowl: A Cautionary Tale". Adelaide University, Australia,UNCCD project.

⁷:Saskatchewan Environment: Comparing and Constrasting: The Dust Bowl of the 1930s, Celebrating Saskatchewan's Heritage.

¹⁰: Climate Education, Australia Government.

^{11 12}:Lester R. Brown, Eco-Economy, Chapter 1, The Economy and the Earth, p9.