The scene Landry witnessed that day was the most severe example of a phenomenon that has overtaken parts of the West this year, one that could exacerbate a slew of environmental problems there in the years to come. More important, an increasing amount of airborne dust is blanketing the region, affecting how fast the snowpack melts, when local plants bloom and what quality of air residents are breathing.

The dust storms are a harbinger of a broader phenomenon, researchers say, as global warming translates into less precipitation and a population boom intensifies the activities that are disturbing the dust in the first place. Jayne Belnap, a research ecologist at the U.S. Geological Survey who has studied the issue, predicts that by mid-century, the fragility of the region?EUR??,,????'?????<