Distinguished Lecture Series: Dr. Richard Seager
The Dust Bowl and Other Great North American Droughts of the Past, Present, and Future
The Dust Bowl drought of the 1930s remains the worst environmental disaster in U.S. history. In the face of years of drought, searing temperatures and relentless dust storms, millions left their homes, hundreds of thousands emigrated out of the Great Plains and an unknown number (but probably in the thousands) died of 'dust pneumonia'. When it was over the agricultural, economic, social and cultural character of the Plains, and much of the U.S., was permanently transformed. While previous droughts left their mark on bison populations, settlers and ranching operations, the 1930s drought was the first to occur after the expansion of agriculture into the Plains had transformed the region by plowing the prairie and planting non drought-resistant wheat. Failed crops and exposed, disturbed soils were the raw material for the generation of dust erosion of Saharan-scale. Climate model simulations show that the dust clouds interacted with solar radiation to intensify the drought and move its center into the central Plains: the Dust Bowl drought was a combined natural-human disaster. The Federal Soil Conservation Service, founded in 1936, quickly understood the erosion problem and put in place conservation measures that controlled the problem. Despite subsequent droughts, there has been no repeat of the Dust Bowl. Since European settlement the timing and severity of western droughts have been orchestrated by persistent variations in tropical Pacific and Atlantic sea surface temperatures. However, tree ring and other records show that between about 800A.D. and 1500 A.D. western North America was struck by a series of devastating multidecadal droughts that, for example, turned prairies into dune fields. While the ultimate causes of these remain unknown, model simulations show that dust from the blowing dunes once more was a likely cause of drought persistence. The West is now faced with the new challenge of climate change induced by rising greenhouse gases. Snow pack is declining and temperatures rising and models robustly predict that in the near term future much of the southwest and southern Plains will become increasingly arid as precipitation drops of warmer air draws more moisture from the soils and vegetation. Soil moisture and streamflows will drop placing increasing stresses on agriculture, ecosystems and water resources. Once more the western landscape will be transformed, and again by human actions, though this time, unlike for the Dust Bowl, solutions will be harder to come by.