Originally hauled to the plains by glaciers thousands of years ago, this boulder is being cracked apart by frost. Photo © James R. Page
In 1960, 3 million acres of land were designated national grasslands, and put under U.S. Forest Service purview. There are twenty national grasslands, all managed by the Forest Service. They share a natural history characterized by remarkable ecological and economic value, political impact, biological diversity and resilience—and a vastness found in few other places in North America. Candace Savage’s book, Prairie: A Natural History explores these remarkable ecosystems, celebrating this oft-unsung landscape with perspective and affection.
The following excerpt is the second in a three-part series from Prairie.
If I had to name my favorite place on the prairies, it would be the high, arid benchlands that sweep along the rim of the Frenchman Valley in southern Saskatchewan. Climb up there on a blue day in early September, out and onto the bald steppe at the top, and the wind will slam against you as if it had a grudge against anything that dared to raise its head above the grasses. This is a landscape that has held to the horizontal for thousands of years, even resisting the torrents of meltwater that once rushed down from glaciers in the Cypress Hills and gouged out the wide, flat trench of the river valley. From up on the benches, you can see the descendant of this ancient flood, a soapy, sleepy little stream that writhes through its oversized course, as if trying to make up in complexity for what it has lost in force.
High on the benchlands, the grasses are stunted and crisp, and the ground bristles with clumps of prickly pear cactus. At one time, long before the Ice Age, this drought-stricken upland was itself the course of a great river that flowed down from the young Rocky Mountains across the northern plains, burdened with loads of gravel and debris. As stones were dropped by the river, they settled onto the riverbed, where they formed a thick layer of sediment. Millions of years later, the benches of the Frenchman Valley are still strewn with rounded, river-washed stones, most of them two or three times the size of a clenched fist, all speckled and splotched with lichens.
Grass, sky, rocks. This land has never been disturbed by the plow—not even a stone has been touched—and it would be easy to think of it as wild, the last stand of the great North American grasslands. In the beat of the wind, you can almost believe you are hearing the muffled drumming of a bison herd that, any minute now, will come rolling into view over the horizon. Through bones and stones and life forms, these lands conserve not only the memory of the past but the whole promise of a future for many grassland animals and plants. The surviving native grasslands bring us as close as we can now get to the prairie in its natural abundance. Yet when you walk toward that horizon and peer down into the valley beyond, you will not find wild herds or camps of nomadic hunters. Instead, you are very likely to see a bunch of cows. It’s still fabulous out there on the rangelands, but it ain’t exactly wild.
The Intercontinental Bovid Boogie
Rangelands—expanses of native grassland that are grazed by livestock—exist only where the prairie has somehow managed to escape the plow, usually because the soil is too dry, too thin, too rocky, or too steep to be suitable for crops. The greater the agricultural potential of a region, the less native prairie is left. Today, the only large, continuous blocks of tall grasslands lie in the Flint Hills of eastern Kansas and the Osage Hills of northeastern Oklahoma, where a stony rime of crystalline quartz just beneath the surface long ago put a dent in the enthusiasm of plowmen.
The surviving native grasslands span the complete spectrum of prairie types, from the stony benchlands of the Frenchman Valley and the rollicking dunes of the Nebraska Sand Hills to the sculpted badlands of the Palo Duro and beyond. Ecologically, they are as different from one another as big bluestem is from blue grama or as a sage grouse (a threatened bird of arid prairie) is from a prairie chicken (its threatened cousin on the humid tall grasses). Yet for the last century or so, these diverse grasslands have all answered in similar ways to one set of human demands—to produce food for the large numbers of cattle and ultimately for ourselves.
In some ways, the introduction of domesticated livestock onto the Great Plains was not much of a shock to the ecosystem. Bison and cattle belong to the family Bovidae, and trace their ancestry back to India and China some 2 million years ago. But whereas the ancestral bison headed north across the Bering land bridge into the Americas, cattle took a turn to the west and wandered through the Near East and into Europe. True to their common ancestry, the two species filled much the same ecological role on their respective continents, as large mammalian herbivores that specialize in consuming grasses.
Even though they spent the last half-million years or so on opposite sides of the Atlantic, bison and cattle are fundamentally alike. Removing wild American bison and replacing them with tame Eurasian cattle—though a stunning act of hubris—was ecologically relatively neutral, the substitution of one large, ruminant herbivore for another on a landscape that had sustained large herds of grazers since the retreat of the glaciers.
This is not to say that the introduction of cattle to the Great Plains has been completely benign—it has not. Cattle and bison, though similar, are not identical. A case in point: bison like to throw themselves on the ground and flail around in the dirt, a self-care routine that is thought to coat the skin with dust and offer protection from biting insects. In the process, they wear away shallow bowls, or “wallows” in the earth. By rubbing out the grasses from these hollows, bison create openings for other kinds of plants. The increased diversity of plants available for shelter and food also augments the diversity of insects, birds, and mammals. If the depressions fill with water, they provide seasonal habitat for aquatic insects and water-loving shorebirds. Or at least they used to.
Because cattle do not wallow, this dynamic has been lost. Meanwhile, cattle have pushed the ecosystem in new directions. Less well adapted than bison to extremes of temperature and drought, cows spend more of their time in the shelter of trees and around sloughs and watercourse. This behavior severely affects both water quality and the condition of riparian forests. What’s more, there are subtle but significant differences in their diets. Bison prefer a steady diet of grasses, with just a garnish of other plants. Cattle, by contrast, choose grass as their staple food but also enjoy a side salad of mixed greens (forbs and shrubs provide between 20 and 40 percent of their feed, as opposed to 5 to 10 percent for bison). No one knows how the vegetation of the rangelands has changed since the bison were displaced, but Bossy the Cow’s exotic dietary preferences must have had an impact.
Don’t Fence Me In
The main ecological challenge on the rangelands is not the absence of bison or the presence of cattle. It is barbed-wire fencing. The “devil’s rope” went into mass production in the mid-nineteenth century to meet the needs of settlers moving onto the treeless (and thus post- and-rail-less) plains. By the early 1880s, factories in Illinois were spinning out enough barbed wire every year to make twenty-five complete twists around the equator. The Great Plains were quickly crisscrossed with fences, and by the close of the decade, the era of the open range had ended. With it went the free interaction between grazers and grasslands.
Before fences, there had been movement. Every spring for millennia, the bison had poured out of their winter ranges on the foothills and parklands, massed together in vast herds, and flowed across the continent on a quest for greener pastures. They had charted new routes each year, jogging east to track recent rainstorms, north to follow the spring, south to savor the greenup after a fire. But wherever their travels took them, they always looped west again in the fall and followed a halting, zigzagging course back toward their wintering grounds. There, in the dead of winter, the bison sustained themselves on a steady diet of sun-cured, protein-rich blue grama and buffalo grass. The bison tracked the resources of the plains and responded to the interactions of the climate, the soil and the plants.
What happened wasn’t always pretty. Even with the freedom to move at will, 30 million-odd bison couldn’t always find enough to eat. During the ferocious winter in 1876, several million bison starved to death along the Brazos River of southern Texas—so many that their humped carcasses reminded one observer of a field of pumpkins.
If bison sometimes felt the sting of random misfortune, they could also dish it out. After a herd of bison had trundled across the prairie, it generally looked as if a herd of bison had trundled across the prairie. Fortunately, grasses are uniquely equipped to put up with this kind of abuse. If a grass is eaten, it can immediately send up fresh leaves. What’s more, grasses that have been defoliated often shift hormones and other resources from their roots to their new shoots, so their rate of photosynthesis increases dramatically. The loss of leaves to an herbivore causes some prairie grasses to grow so exuberantly that they slightly overcompensate for the tissues that have been removed. It probably doesn’t hurt that the saliva of some grass-eating mammals contains growth stimulants that encourage the grasses to send out new shoots.
The unexpected synergy between migratory herbivores and grasses is probably the result of a chain reaction that begins when the leaves are cropped. But this response only appears to happen if the herbivores are free to migrate and select grasses in the juicy prime of youth. If the stress of herbivory is delivered in a well-timed pulse, the plants actually seem to benefit from it.
Did the bison and the prairie grasses once engage in a similar interaction? The evidence is suggestive, though no one can say for sure. The loss of this cyclical rhythm may well be the price we pay for curbing the wild prairie with barbed-wire fencing.
Other Herbivory
Although cattle are the most conspicuous herbivores on the range, they are certainly not alone. Ounce for ounce, grasslands support a greater live weight of plant eaters than any other terrestrial ecosystem. The largest group of grassland herbivores, in numbers if not in mass, is insects. While there is not a complete catalog of prairie insects, the list of the herbivorous species alone would certainly contain several thousand entries, perhaps even tens of thousands. The second-most populous group of herbivores on the grasslands is rodents.
Of all the rangeland rodents—pocket gophers, jumping mice, pygmy mice, ground squirrels, voles and more—none is more remarkable than the black-tailed prairie dog of the western plains. Before the prairies were settled, this was the prairie dog’s world. Its population ran into the billions, and if all the colonies, or towns, had somehow been amalgamated into one great metropolis, they would have occupied an area as big as Texas. In reality, prairie dog towns were, and in some places are, dotted across the short- and mixed-grass prairies, where they look for all the world like moonscapes of closely cropped grass cluttered with craters of bare earth. Each of these earthworks marks the entrance to a shaft that plunges six to ten feet below the surface and then levels out to lead to a complex of nest chambers and latrines. Prairie dogs descend into their burrows to sleep, give birth, nurse their young and escape from predators, but they spend much of their lives on their earthworks—sprawled out on their bellies in the sun or upright and alert, ready to bark a warning at the first sign of danger.
In the last 150 years, any other danger to prairie dogs has been overshadowed by a great and persistent threat. To many cattlemen, a prairie dog colony represents little more than a terrible waste of grass, a view that has been seconded by range scientists. With that in mind, prairie dogs have been poisoned with bait, suffocated with gas, drowned, and shot. The result of this relentless and sometimes gleeful campaign of extermination has been a 98 percent reduction in the population since 1900.
The war against prairie dogs has been based on the premise that they destroy rangelands. And it is certainly true that a prairie dog colony bears a striking resemblance to a badly managed pasture. But recent research suggests that while prairie dogs can prevent the plants from recovering by keeping them snipped down, the rodents are rarely the primary cause of overgrazing. Because they cannot move into tall stands of dense vegetation, they can only follow where heavy grazing by cattle or bison has opened up a path. Ranchers who overtax their rangelands have effectively laid out a welcome mat and invited the prairie dogs to “infest” their land.
The ecological benefits of sustaining prairie dogs are incalculable. Prairie dogs are the beavers of the grasslands, in the sense that they reengineer the environment and create a living space for an astonishing variety of creatures. Through their constant gnawing, they not only maintain fresh fodder for cattle and bison but also increase the diversity of the vegetation by opening up space for life forms such as scarlet mallow and prickly pear cactus. These plants provide food and shelter for other herbivores. Cottontails are attracted by the shelter of prairie dogs’ mounds and burrowing owls lay claim to abandoned burrows. Carnivores, too, are supported by prairie dogs—black-footed ferrets, one of the rarest carnivores on Earth, depend on healthy prairie dog populations. As prairie dog populations decline, so do black-footed ferrets, burrowing owls, and countless other species.
Rangeland Successes
Happily, some species have bucked the dismal trends: the pronghorn is chief among them. Once as fantastically abundant as bison, with an estimated precontact population of 35 million, the species was decimated by overhunting during the settlement era. By 1900, the herds had been reduced to a tattered remnant of some 15,000. But a determined conservation effort turned the situation around, and the herds have rebounded. The count currently hovers around 1 million.
The pronghorn is a survivor. Although dozens of related species once roamed the Great Plains, only one, Antilocapra Americana, made it through the mass extinctions at the end of the Ice Age. In so doing, the pronghorn permanently outdistanced its most fearsome predators; yet even today, it flies across the prairie as if lions and wolves were still in hot pursuit. The fastest animal in North America, it can hit speeds of 60 miles per hour and maintain a blistering pace for miles. Running open-mouthed, it gulps air down its extra-large windpipe and into its extra-large lungs, as its powerful heart keeps its muscles fueled with oxygen. This is a species with the prairie in its blood, the animal world’s answer to wide-open spaces.
Pronghorns are not alone in their success on the range. Alongside the ranging herbivores, a number of predators make a successful life on the Great Plains. Think spiders, tiger beetles, robberflies and wasps; think snakes, toads, owls and hawks; think shrews, skunks, bobcats and wild dogs. Time was when the catalog would also have included wolverines, cougars, bears and wolves, but those species were pushed off the plains during the settlement era. Wolves in particular were targeted.
In the Bad Guy vs. Good Guy paradigm of the nineteenth century, the eradication of wolves should have been pure gain. Instead, it opened the way for a new breed of “outlaw” predator to move in. As long as wolves were the dominant canids on the prairie, their slightly smaller cousins, the coyotes, didn’t stand a chance. Any coyote that entered a wolf territory was likely to meet a bloody end.
After wolves were removed from the scene, the coyotes muscled in and the balance of power began to shift. Coyotes are versatile predators. Depending on the circumstances, they can band together to take deer or hunt alone to catch small rodents. So just as wolves had once impinged on coyotes, coyotes now aggressively take steps to limit the populations of their smaller competitors.
One thing we can be sure of is that coyotes are now securely ensconced in their position as top dog across the whole wide sweep of the rangelands. After a century or more on agriculture’s Most Wanted list as livestock predators, coyotes are still out there everywhere you look. By any sensible measure, attempts to limit their number have been a complete flop, much like trying to empty the bathtub without turning the water off. But control efforts continue, and inevitably trigger a cascade of subtle and unanticipated changes in middle-sized predators and their avian prey, wetland bird populations, rabbits and upland rodents. Far from being a dispensable animal (as one range manager called them) coyotes have become a keystone species in rangeland ecology.
Long honored as the Trickster, Coyote still walks the prairie with us, calling us to look beyond the obvious.