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Greg Okin, a professor of geography at the University of California at Los Angeles, recalls being caught in a dust storm off Interstate 10 in the Coachella Valley some years ago. “You couldn’t see ahead of you, so you had to slow down. But when you did, you started thinking about what was behind you. What car was going to plow into you because it couldn’t see.”

What Okin experienced was just one gust in a gathering storm. Blowing dust and brownout conditions on January 19, 2009, created a chain reaction of fatal crashes on I-70 in eastern Colorado. In July a massive dust cloud descended on Iraq, forcing the police to wear masks while directing traffic through the strangely dark streets of Baghdad. In September one of Australia’s worst dust storms in 70 years clogged the skies over Sydney with 5 million tons of particles, causing international flights to be diverted and prompting a spike in emergency calls from people who were having trouble breathing. And such disruptions can take on a global dimension. Satellite images show storms in northern Africa blowing particles all the way to the Amazon Basin. Plumes from northern China can reach Hawaii and California. A 2002 dust storm from the Gobi Desert tracked east across the Pacific Ocean, past the United States, and out into the Atlantic.

The problem has been building for a long time. Wars, oil and gas exploration, agriculture, cattle production, and general development have broken up soil surfaces around the world. Drought, rising temperatures, and a shift in some regions from grasslands to shrublands have accelerated the problem in the past 10 to 15 years. In the United States, the loss of grasslands and other natural shields that hold arid soils in place is particularly pronounced in New Mexico, Arizona, and Nevada, where dust production has increased by orders of magnitude over the past several decades. And dust begets more dust: It reduces the reflectance of the winter snowpack and increases the absorption of sunlight, causing snow to melt sooner. Five times as much dust now falls on the snowpack in the Colorado Rockies as when the area was first heavily settled in the mid-19th century.


Hence dust is both symptom and cause of a grim type of environmental decline: desertification, the degradation of vital grasslands into barren and unproductive desert. This process unfolded with horrifying consequences in the 1930s, when large portions of the Great Plains states turned into the Dust Bowl as a result of lack of rain and poor farming practices. Millions of acres of fertile topsoil blew east, toward and into the Atlantic Ocean, devastating American agriculture.

Desertification is happening today around the world, most notably in northern China, home to much of that nation’s 1.2 billion citizens. “The world needs more food, more land to grow it, and more water to irrigate it, yet we have the same amount of land, less water, and higher temperatures,” Okin says. “This is a train wreck about to happen that will impact hundreds of millions of people now and perhaps billions in the future, because that’s how many live in dry lands worldwide.”

Last year was a record one for dust production in the United States, when sparse and badly timed desert rains produced the lowest vegetation cover on record and 5 to 20 times as much dust as usual from the Colorado Plateau into the mountains. The snowpack melted about 50 days early because dust put massive stress on high mountain vegetation and lowland farms and fields. In southern Colorado scientists reported the most rapid snowmelt since the mid-1980s, when records were first kept. “Increased runoff caused by dust on snowpack acts as a major leak in the reservoir system,” says Thomas Painter, a professor of geography at the University of Utah.

Okin thinks this may be just a hint of things to come. “Climate models predict that the Southwest should get warmer and drier,” he says. “By 2050 soil moisture could be lower than it was in the Dust Bowl era.”

Dust is two-faced—a lesson I am about to learn as my plane descends to the desert near Las Cruces, New Mexico, where I am to meet Okin and see his work. Dust can be beneficial to parts of the planet, as when it travels from the Sahara to the Amazon Basin, where it deposits phosphorus that helps keep the rain forest lush. Similarly, dust from northern China brings phosphorus and other vital nutrients to the Hawaiian Islands. Dust from the many continents ferries iron and phosphorus to the ocean surface, promoting the growth of phytoplankton and other marine plants that feed sea organisms and draw carbon dioxide out of the atmosphere. Fine bits of degraded rangeland in southern Africa, South America, and Australia blow into the Southern Ocean, helping to sustain the rich biodiversity of those waters.

But dust from the Sahara also blows up onto the snowpack in the Alps, causing early melting. Pesticide-laden particles from central Asia’s shrunken Aral Sea are harming the respiratory health of people in the region, Okin says. Dust from northern China worsens the heavy pollution in Beijing. As in the American Southwest, population growth and changing climate are likely to make matters worse.

Owens Lake, which lies at the base of the eastern side of the Sierra Nevada in California, offers one glimpse of the connection between dust and development. Water diversions for Los Angeles left the lake bone-dry by 1920. By the 1930s, the Owens Lake playa was the largest source in North America of PM10: particulate matter measuring 10 micrometers or less, small enough to readily enter human lungs.

“The material that began to blow was also very high in arsenic, lead, lithium, antimony—some very bad things,” says Marith Reheis of the U.S. Geological Survey (USGS) in Denver. “You wouldn’t want to be downwind from Owens in a dust storm.” These chemicals are natural environmental toxins, a problem endemic with dust sources worldwide. In August 2005 a California superior court judge compelled Los Angeles to start putting water back into Owens Lake. Only then did the dust plague diminish.