The snowcapped peaks of Colorado have been turned brown and pink by a series of dust storms that some warn is a hint of a grimmer future for the region.
Ever since European settlement of the west, dust kicked up in the deserts of Utah, New Mexico and Arizona has been pushed onto the southern Rockies by winds blowing from the southwest. But this year has already seen a high number of storms -- 12. Compare that to eight during all of last year or four in 2003.
The dark dust absorbs sunlight and hastens snowmelt by as much as 35 days. It's also been an unusually warm spring already in the southwest. Colorado rivers are cresting nearly a month early, stressing some water managers who fear they will not have enough for late-summer crops. "This whole system was built around the runoff coming pretty much as the crop came up," said Steve Vandaver, general manager of the Rio Grande Water Conservation District in Colorado's San Luis Valley.
There is actually less dust in the Rockies today than at the phenomenon's peak, in the early 20th century. Widespread cattle grazing stripped off the protective cover of the desert and churned the underlying soil. After Congress sharply limited grazing in 1934 the level of dust in the Rockies fell from seven times its historical norm to its current, still-high rate. There's about five times as much dust in the mountains than prior to the 19th century.
Scientists have only been tracking the number of storms since 2003, but their data matches anecdotal observations that the events are becoming more common. Any activity which disturbs soil that has had its surface layer stripped can kick up dust that contributes to the storms -- energy exploration, off-road vehicle use, driving on dirt roads, even hiking and mountain biking.
Thomas Painter, director of the Snow Optics Lab at the University of Utah, gives a presentation on the dynamic that includes a photo of his son hiking in Southern Utah, trailing a stream of dust. "All of us who are users [of public lands] are contributors," he said. "There are more ATVs on the landscape than 30 years ago. More mountain bikers, more hikers."
Those activities don't need to have risen that dramatically to bring about more frequent storms, some scientists say. The past few decades have been unusually wet in the west, but this one has been dry. That kills some of the vegetation binding the soil, which and makes it more likely to travel when disturbed. With climate change warming the west, the storms are likely to increase, experts say.
Jayne Belnap, a scientist with the USGS in Moab, sits in her yard staring at the 12,000-foot-high peaks of the La Sal range outside town. Normally white into the summer, they are almost bare. "I think it's just a harbinger of the future," she said.
Photo credit: McKenzie Skiles for the Los Angeles Times