Climate experts say that Oklahoma farmers caused the 1934 drought, which covered 80% of the US. Apparently they have been doing this for thousands of years.
A 1998 study by federal scientists, for instance, found that droughts as widespread and severe as that of the Dust Bowl of the 1930’s, when 65 percent of the country was affected at the drought’s peak in 1934, have occurred once or twice a century over the last 300 to 400 years. A decade-long drought, the study found, occurs about once every 500 years.
More recent analyses of tree-ring data have identified a 16th-century megadrought that affected much of the continent for years, far outstripping any drought of the 20th century in persistence and severity. It was during this drought that the first English colony in America, at Roanoke Island in North Carolina, disappeared, and experts now believe the drought is what killed it off.
The report, by Dr. David W. Stahle, a tree-ring analyst at the University of Arkansas, Dr. Edward R. Cook, an analyst of ancient climates at the Lamont-Doherty Earth Observatory of Columbia University, and six colleagues, appeared in the March 21 issue of Eos, a scientific publication of the American Geophysical Union.
Megadroughts lasting a century or two are known to have occurred in what is now California over the last 3,500 years. Droughts of similar severity have also been implicated in the downfall of the empire of the Maya in Central America a millennium ago; the Akkadian empire (the world’s first) in Mesopotamia 4,200 years ago (that drought lasted 300 years) and several pre-Inca cultures in South America.