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.”