Today the arid dust bowl years of the 1930s seem an anomaly. Now fields of grain cover the once parched plains of Oklahoma, Nebraska, the Dakotas, and other Plains states. But if Kathleen Laird is right, dust bowl conditions may be far from unusual for the Great Plains. Her research shows that the region has suffered repeated droughts for thousands of years, but the last 700 years have in fact been unusually wet.
Laird, an ecologist at Queen’s University in Ontario, reconstructed the Great Plains’ past climate by studying diatoms, water- dwelling algae marked by ornate microscopic silica cell walls. The researchers collected diatoms and water samples from 53 different lakes across the Great Plains. Since the saltiness of the lakes varied, Laird’s team could determine which species of diatom were most abundant at which levels of salinity.
They next looked for a small lake that had no streams running ...
