Will the Dunes March Once Again?
As recently as 200 years ago, dunes and sheet sand were active throughout the Great Plains. A serious drought could bring them back
Eastern Colorado rancher Brad Peterson likes to joke that farming there is just hydroponics: seeds, water and fertilizer in sand. Like any joke, this one contains hard truths. Only 150 years have passed since the Great Plains were known as the Great American Desert. The dunes and sheet sand that 18th- and 19th-century explorers reported still cover large areas of the plains, occasionally burying fences, roads and rangeland, but no one believed that much of this sand had been windblown (active) in the past 10,000 years. Now, from the Nebraska Sand Hills to the West Texas Monahans dunes, writer Daniel Jack Chasan follows the trail of U.S. Geological Survey geologist Daniel Muhs as he and other researchers tell a different tale.
By carbon-dating soils, bones and artifacts, and researching early writings, Muhs and his colleagues have identified much dune activity during the past 1,000 years--and, in places, during the past century and the drought of the 1930s. All the dunes need to start moving again is drought prolonged enough to liberate the sand from the fragile grip of vegetation.
Changes in temperature and rainfall (such as are predicted by some global warming models, or even that occur within historical variation) may do it nicely--and with serious consequences. Passing by sandy stretches as he drives along Interstate 76 in eastern Colorado, Muhs notes soberly, "If that sand ever starts moving, this Interstate is history."