As difficult as conditions have become in the Southwest, western China, the Australian outback, and too many other locations, the worst-case scenario is probably North Africa’s Lake Chad. This once important lake has seen its problems grow steadily worse as population and water use have increased over the past century. Today the Bodele Depression—the low point of the vast ancient basin in which modern Lake Chad lies—is the most active dust spot in the world.

It is not hard to identify what went wrong. The amount of water flowing through the principal rivers that feed into Lake Chad has declined by 73 percent over the last 40 years. Falling water levels have exposed fine-grained sediments along the periphery of the lake; high winds whip up those sediments into nasty clouds of dust that cause health problems for residents throughout the region. There is not enough moisture to recharge the groundwater; without that, thirsty plants are disappearing, making it likely that dust will only increase.

The dusty troubles of the American Southwest stretch all the way back to the mid-1800s. Before then, the landscape was largely stable grasslands. But the arrival of the railroads in the 1860s and 1870s enabled ranchers to put large numbers of grazing animals on public ranges. “They’d fatten them up and then put them back on the trains to be taken to Chicago and Omaha for slaughter,” says Painter. “For some time this was all free since there were no charges for public grazing.” The result of this four-legged invasion was dust. If you were standing up on the summit of Snowmass Peak above Aspen in the 1870s, he notes, you would have seen a slight tinge of dust on the snow at winter’s end. By the 1890s there was a much heavier stain.

Until disrupted, that dust had been a stable part of the local environment for thousands of years. Reheis has studied the dust covering much of the western United States, analyzing its chemical composition to determine where it came from. Much of the dust deposit east of the Rockies arrived in the last ice age, which ended some 11,000 years ago, when particles that had been ground up and transported by glaciers were deposited by meltwater streams. That fine-grained material was then eroded by the wind as the land dried. Dust produced during the glacial era made major contributions to the soil in the southern Midwest prairies, the most important agricultural region in the country today. “Windblown dust is part of normal soil building. Our whole breadbasket is dust,” Reheis says. “The most fertile stuff in the central Plains is all eolian [windborne] dust, most of which was deposited during the last glaciation.”

Prairie grasses that formed over these deposits did a good job of holding the landscape down, says William Schles­inger, a biogeochemist at the Cary Institute of Ecosystem Studies in Millbrook, New York, and one of Okin’s mentors. “Anything that can slow winds down so they can drop some of their load of silt, clay, and nutrients is good, and clumps of grass are perfect barriers,” he says.

Even when grasslands begin to diminish due to overgrazing and drought, biological and mineral crusts help keep soil stable, reports Jayne Belnap, a USGS research biologist in Moab, Utah. A well-developed biological crust is nearly immune to wind and water erosion. “It’s tough as nails against all wind forces,” she says. “Tests in wind tunnels of undisturbed crusts in the national parks show that biological crusts can withstand winds up to 100 miles per hour.”

Compressional forces, on the other hand—forces that are delivered vertically, such as the impacts of hooves, tires, and feet—can break up the soil and make it vulnerable to wind erosion. And therein lies the problem. Areas that are grazed or plowed may take decades to recover. Human development and off-road vehicles contribute to the degradation. As a result, the desert rangelands are losing their fine-grained material.

On a summer day with temperatures rising to about 105°F, I take a dusty ride with Greg Okin out to his research site at Jornada Experimental Range near Las Cruces. He is going to show me up close the damage that wind erosion is doing in this part of the country. “Shrubs used to occur on these former grasslands, but they were rare. Now they dominate,” he says.

Jornada encompasses some 250,000 verdant acres of native shrubs and grasses under wide blue skies in the Chihuahuan Desert. For the last 14 years Okin has come here to study how windborne dusts are changing the face of arid regions here, throughout America, and around the world.

The Chihuahuan Desert covers portions of New Mexico, Arizona, Texas, and north-central Mexico. The wind here normally blows toward the northeast. It is generally steady and strong in spring, but in summer it occasionally twists into a convection storm—a small, circular weather system that can direct brief but powerful gusts at the ground. These winds kick up fast-blowing dust storms that can envelop the unwary.

Okin, a wind erosion expert, tells me he got caught in one such storm just the other day on a dry lake bed. He was with researchers from the University of Texas who had set out portable wind tunnels to measure dust movement. Suddenly a fierce wind arose. “We were smelling dust, tasting dust, and couldn’t see anywhere,” he says. “I actually like dust storms, but when this one started attacking the Texas folks’ equipment, it just wasn’t fun anymore.”

Okin points out the rugged terrain, a green mosaic of vegetation. Mesquite bushes have migrated out from dry streambeds and the edges of dry lakes into the valley floor and flatlands. Creosote and mesquite have moved closer together, squeezing the grass in the middle. Grass is important here because it keeps the desert soils in place.

Okin first came here in 1996 to work with Schlesinger, who had been studying the Southwest desert’s gradual transition from grass to shrubs since the 1980s. Schlesinger noted that as the ecosystem changed, key nutrients in the soil—such as nitrogen, phosphorus, and various organic elements—accumulated beneath the canopies of the mesquite bushes, forming what he called islands of fertility and starving out the surrounding grasses.

Okin is now studying how winds scour nutrients from grassy areas and deposit them around shrubs, gradually killing off the grass and changing the desert from grassland to shrubland. He calls the wind-scoured areas between these shrubs “streets” and takes me to one area where these streets are well defined with fertile soils piled like dunes under mesquite bushes. “Once it gets that bad, there’s not much chance for grasses to recover,” he says.

Mesquite-covered dunes like these produce 10 times as much dust as do areas covered with native grass. I ask Okin how the whole process got started. Fire suppression is one prime cause. “Before Europeans moved into the territory, fires regularly moved across the landscape, killing shrubs but not grasses, which had evolved to burn, but not die, during the process,” he says.

Shrubs like mesquite and creosote grow too far apart to sustain wildfires, but grass acts as kindling to move the flames from one shrub to the next. Cattle grazing has also upset the balance by eliminating a lot of the grasses. “Cattle like grass but won’t eat shrubs,” Okin says. “They provide a selective pressure against grass and in favor of shrubs, while also depleting the grasses that sustained fires and killed shrubs.”

One hot morning I accompany Ed Fredrickson, a range scientist with the U.S. Department of Agriculture, to look at the Criollo cattle he has brought up from Mexico. He hopes they can solve some of the problems that English breeds have created. Criollo cattle are a desert-adapted breed that eats less and walks greater distances. Here they are less social, do not group up as tightly, and so distribute their footfalls more evenly across the landscape. They also weigh about 800 pounds, much less than the 1,200 typical of their English cousins. “English breeds have a lot of fat on their backs,” Fredrickson says. ”Butchers end up cutting that away. Cattle don’t need so much back fat in the desert.”

According to Fredrickson, cattlemen do not want to be blamed for turning grasslands into dust-choked desert. They also do not want to lose their livelihood. As their lands deteriorate, some have begun looking at their grazing practices and options such as Criollo cattle to take better care of the land.

Later I drive with Okin back to Jornada, dodging jackrabbits jumping out of the brush. Early land managers misstepped by poisoning coyotes. Without those predators, small mammals such as jackrabbits bred rapidly and devoured much of the local grasses. Today new threats loom. Okin points to dust swirling around a new housing development. These areas generate 100 times as much dust as desert covered with vegetation.

Okin takes me to a number of experiments testing ways to beat back the dust. The most promising approach uses eight-inch-tall fences called Con-Mods, which have been set up to stop large bare gaps from developing between shrubs. At each site where these chicken wire–like fences have been installed, leaves, twigs, and other plant materials are caught in the barriers, build up at the base, and enrich the ground between shrubs. “That litter is where grasses can get going again,” he says.

I ask if he really believes we can gain the upper hand on dust. He tells me that during the Dust Bowl era, when land managers saw their lands blowing away, they got together in 1934 and promoted the Taylor Grazing Act, which set strict limits on grazing activities in the western U.S. “What we did then is a model of what we can do today. We had a problem, we took action, and for a long time things got better,” he says.

Now we have a more difficult situation, with desertification under way at locations around the world. Nevertheless, in the American Southwest and perhaps elsewhere, Okin thinks that it may be feasible to slow or even reverse the process. “When erosion is allowed to deplete the resources in the soil, grasses just can’t compete with shrubs,” he says. “But if we can find ways to retard erosion and trap plant materials that start to move, natural ecological processes might help grasses come back. It might be an opportunity to turn an inexpensive method into grass recovery.”

Our future does not have to be a dusty one. A little chicken wire, better grazing practices, leaner cattle, controlled development, and fewer off-road vehicles could help restore the grasslands. The tide could turn against the dust, Okin says. “It could happen.”