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Most of us know about the Dust Bowl: the huge storms of dirt and dust that swept across America in the 1930's. But what I'm wondering is...
I've often heard that it was the farmers plowing up to much soil, but that doesn't make any sense to me because we're definitely plowing up more soil now than we were then.
The Dustbowl occurred during the 1930s because of a combination of man-induced drought and the (mis)use of relatively new farming practices.
In the 1920s, the spread of automotive (and tractor) technologies made it possible to "plow up" the Great Plains. This resulted in the loss of a lot of natural moisture and the creation of drought conditions in lands that had been marginal to begin with regarding the adequacy of the water supply.
Even by the 1930s we still had not learned our lesson. There were conservation techniques using the new technologies, but we weren't using them. For example, the tractors would still plow up and down slopes (the "easy" way) making it easy for topsoil to run down hills and into the rivers. More to the point, the newly dry and loosened topsoil would then go into the air and create a "Dust Bowl" when the winds kicked up. There was a real fear that the agricultural Midwest (basically the Plains states) would turn into a desert.
It was only after an additional half a decade of bitter trial and error (and a new generation of better educated farmers) that things changed. By the mid 1930s, it was a relatively new technique called contour farming, which consisted of using motor vehicles to plow horizontally around hills instead of vertically, that saved the day. Also, farmers started planting trees as "windbreaks" in strategic locations.
IMHO, it could happen again, probably in a developing country like China, which is trying to "catch up" to the United States, and has been prone to adopting our bad habits of an earlier era.
Bottom line, the Dust Bowl was (largely) a man-made, not a natural phenomenon. And the operative principle was attributed to Confucius:
"Men are the same everywhere. Only their habits are different."
The Dust Bowl was caused by farmers tilling up too much soil. However, there were also other factors. Weather also played a key role. Because there were several years of drought, and farmers had plowed up so much ground, when high winds came along the soil was blown off the ground, and the rest is history. This became somewhat of a vicious circle: no crops grew and so the dust could not be controlled.
As far as it happening again... Yes, I suppose it could and on a large scale, but run for cover. Because there would be some other very serious issues. Its occurrence would likely mean that there was little to no water available for irrigation. If that were the case, then I can not imagine how people would be responding to it.
There are two books I love to recommend on this. The Worst Hard Time is a history book with a lot of first-person reports and a summary of what people were thinking before the dust bowl -- what the optimism looked like. The saddest bit I remember was that there were responsible ranchers who didn't over-plow, who had intact prairie -- until their neighbor's dust buried them and killed their grass and herds.
The other is on huger scale, Dirt: The Erosion of Civilizations. Big erosive events are recorded in sediment fans (often in the ocean at river-mouths). Analyzing these, Montgomery argues that there have been six cases of organization->ag->regional market->over-farming->erosion->collapse, and that we're plausibly in the seventh.
Climate modelling by NASA suggests a change in the Jet Stream was partially responsible for the 1930s drought in the US.
Cooler than normal tropical Pacific Ocean temperatures and warmer than normal tropical Atlantic Ocean temperatures created ideal drought conditions due to the unstable sea surface temperatures. The result was dry air and high temperatures in the Midwest from about 1931 to 1939.
Sea surface temperatures create shifts in weather patterns. One way is by changing the patterns in the jet stream. In the 1930's, the jet stream was weakened causing the normally moisture rich air from the Gulf of Mexico to become drier. Low level winds further reduced the normal supply of moisture from the Gulf of Mexico and reduced rainfall throughout the US Midwest.
Other conditions at the time included:
a high-pressure system in winter sat over the west coast of the United States and turned away wet weather— a pattern similar to that which occurred in the winter of 2013-14. Second, the spring of 1934 saw dust storms, caused by poor land management practices, suppress rainfall.
Regarding the "and could it happen again" part of your question; possibly, due to climate change. As others on here have noted, the original dust bowl was a combination of crappy soil conservation practices and a prolonged drought. Our soil conservation practices have improved a lot, but we still plant water-intensive crops like monoculture corn in places where it historically never would have grown. For instance, in the southern Great Plains where it's really dry and native vegetation usually consists of low-shrubs and short grasses. We're able to grow crops in these areas now, because of center-pivot irrigation technology (started in the 1940's) and groundwater pumping. But as our global climate system continues to warm and our groundwater resources become increasingly scarce, it's unlikely that we will be able to continue these practices in the future. Some authors think that a sudden, sustained drought in these areas consistent with what was observed in the dust bowl could lead to similar problems in the Great Plains observed in the 1930's. Just finished reading this paper in Nature Plants on this very topic : https://www.nature.com/articles/nplants2016193
