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When megadroughts strike
Aug 10, 2012

 

The land was parched from days of hot temperatures in the mid-30°C. And then came high winds, which whipped up two dust storms that deposited 6,000 tonnes of silt in Winnipeg. What Winnipeggers observed in 1931 was the result of storms bearing topsoil from the plains of southern and central Saskatchewan, as well as North Dakota and South Dakota in the U.S. The infamous Dust Bowl of the Dirty Thirties had struck the prairies with a vengeance. 
Professor J.J. Jackson of the Manitoba Agricultural College collected the dust from one square yard of a downtown street and then calculated the extent of the silt that fell on the city, arriving at the figure mentioned above. Another storm, with winds from the east, blew much of the silt out of the city. 
According to a group of researchers, drought conditions on the Great Plains of North America that created the Dust Bowl of the 1930s will become the norm in the vast agricultural zone. But even the 1930s drought was not as intense as the one that struck western North America between 2000 and 2004, which the scientists now classify as the worst in 800 years. It was unmatched since the drought of AD 1146 to AD 1151 as determined by tree-ring growth analysis.
The 2000-04 drought affected soil moisture, river levels, crops, forests and grasslands, according to a recent article in the Globe and Mail by Renata d’Aliesio. Crop production in 2,383 counties in the western U.S. declined by five per cent. “As trees, plants and crops withered, more carbon dioxide (a greenhouse gas) was released into the atmosphere.”
During the late 20th-century event, the dust storms typical of the 1930s reappeared in parts of the prairies, as the soil was so dry that hot, dry winds picked it up and it swirled about like a “dust bowl.”
A “megadrought” that will severely cut crop production could be looming on the horizon, the scientists warned in an analysis by the Drought Research Initiative, a temporary program that includes university and government scientists. 
Although, there is no indication that the existing drought in the U.S. Midwest is part of a lengthy trend, corn and soy bean crops are again withering on the stem, driving the price of the much-used products (corn feeds livestock — hogs and cattle — and is used in a multitude of food products) to new lofty prices. Due to the devastating drought in the Midwest, the U.S. Department of Agriculture (USDA) has estimated that food prices will climb 2.5 to 3.5 per cent in 2012 and three to four per cent in 2013. Before the drought, the department had projected a near-record harvest.
In an August 6 Time magazine article, USDA Secretary Tom Vilsack said: “I get on my knees every day. If I had a rain prayer or a rain dance I could do, I would do it.”
Perhaps he should consult the elders of the File Hills First Nation in Saskatchewan. In 1931, Chief Buffalo Bow directed his tribe members to perform a sacred rain dance to alleviate the drought killing their cattle. For two days and two nights, they danced non-stop. Soon after, all of southern Saskatchewan was drenched in rain for two days.
Similar to the scientists, farmers across the U.S. and Canada are now worried that droughts will soon become commonplace.
To understand what the future may bring, it is necessary to return to another time when a megadrought dried up vast expanses of water in Manitoba. During the Altithermal, commonly referred to scientists as the Atlantic Episode, from 6540 BC to 3110 BC, the level of Lake Manitoba fluctuated from essentially a dry lake bed to a body of water essentially the same size of today. The southern basin of the lake was bone-dry in 5500 BC.
Lake Manitoba dried to the point that it became kilometres of mudflats and gravel banks dotted with brackish ponds for approximately 1,000 years.
The Northern Plains, including Alberta, Saskatchewan, North Dakota, South Dakota, Minnesota, Wyoming and Nebraska, were particularly hard hit by the megadrought during the Altithermal.
By 4500 BC the warming trend with temperatures about 4°C higher than the present expanded the treeline 240 kilometres north from where it now exists.
While much of southern Manitoba was in drought conditions, there were still oases that allowed early aboriginal hunters to flourish.
“Personally, I don’t think it was a thousand years of continual drought (at the height of the Altithermal), Leo Pettipas, an archaeologist then with the Manitoba Historic Resources Branch, told the WREN a few years ago. But, he added that droughts were more frequent and greater in severity than any over the past few thousand years.
Similar to the Dust Bowl of the 1930s, the archaeologist said the droughts of the Altithermal resulted in soil and sand being blown about and deposited over hundreds of kilometres. 
The sand dunes and hills of southwestern Manitoba were created during the Altithermal. It was also during the Altithermal that grasslands first appeared in Manitoba. The drought occurred due to the failure of summer rains brought about by an intrusion of Pacific air masses into the prairies, which allowed the expansion of the short-grass plains. 
Despite the continual threat of drought, southern Manitoba was actually more appealing to early hunters than the Great Plains and Dakotas area in the U.S.
“Human beings suffering from drought sought refuge in the more attractive areas such as in southern Manitoba where there were rivers and springs, and the lakes region,” said Pettipas. Basically, human habitation was in the fringe areas of the drought. Humans moved from the grasslands into the forests where water and shelter was found. They followed the buffalo (bison) , their main prey, which were also in search of more nutritious grasses to feed upon.
Essentially, during the Altithermal prolonged megadroughts, precipitation was at a minimum and temperature was at a maximum. Today in the U.S. Midwest, precipitation is again at a minimum and temperature at a maximum, but not yet at the megadrought level of the Altithermal. Still, the present drought is devastating.
Since the human population was extremely scant at the time of Altithermal, people were successively able to cope by moving to greener pastures. Today with millions of people and livestock occupying the Great Plains, a massive movement of people and animals is not an option. As a result, prairie dwellers will have to learn to adapt to more severe weather conditions and the possibility of megadroughts soon ravaging the land.