IT'S A FINE DAY FOR A PRAIRIE FIRE. Wind is steady at 10 to 15 miles per hour from the southeast, and the humidity hovers around 50 percent. For early August in Iowa the weather is cool and won't overheat the crew.
Kevin Pape, a ranger for Stone State Park, attired in a flame-resistant Nomex suit and broad-brimmed fire hat, exudes quiet confidence as he passes among the workers. He's handing out aerial photographs marked with letters and boundary lines of the next unit to be burned, a 13-acre parcel of prairie just four miles from downtown Sioux City. Across Talbot Road, today's firebreak, the last unit still smolders, blackened earth gently crackling, wisps of smoke still rising.
Pape and his crew are preserving prairie in the Loess Hills of Iowa by torching it.
These are some of Iowa's last and most ecologically diverse prairies, and they're disappearing like drops of water on a hot skillet. Of the vast prairie that once blanketed the Hawkeye State, less than one-tenth of one percent survives. Of that tiny remnant, more than half is here in the Loess Hills, a long band of steep peaks, some jutting up to 400 feet, hugging the Missouri River valley along the western edge of the state. The hills are Iowa's secret treasure, a 650,000-acre miniature mountain range that punctuates the famous flatness of the Midwest with sharp slopes and cool, sheltering hollows.
I came here by air, and so did the hills. They were blown in, particle by particle, on the winds. The Loess Hills get their name from the dirt they're made of. It's a German word, Lšss. It rhymes with "fuss" and means dust, literally "loose." Loess is fine yellowish mineral stuff, rock pulverized by glaciers over the 150 millennia of the last ice age and carried south by rivers. When the rivers dried, they left tons of this silt-like powder to be picked up by winds and scattered across the heartland.
Under the rich topsoil of its green croplands, most of Iowa is covered in a 50-foot-deep blanket of loess. Only here, though, where the winds from the west met the Missouri's eastern shore, was the loess dumped in great heaps. The only other landform like it is along the banks of China's Yellow River, named for its loess-clouded waters.
Fragile Giants is what scientific historian Cornelia Mutel titled her 1989 book, the best natural history yet of the hills. Fragile indeed. Where the loess is exposed, you can break it off in chunks and crumble it to a powder that disappears almost before it hits the ground. Occasionally a farmer carves "fragile giants" into a field of corn, a message to airplane passengers that this is not just flyover country but has a name, an identity.
From the ground, the topography calls to mind the intricate, pleated patterns of sand dunes. Long, meandering ridges are like spines with rows of smaller ridges projecting out like ribs, and even smaller spur ridges projecting from these in turn. Natural terraces follow the hills' contours because of the mineral soil's peculiar inclination to compact into straight vertical walls. These "catsteps" — unmistakable signatures of loess terrain — create a complex network of ridges, a hiker's dream of hilltop mazes with nonstop prairie vistas.
Most of Iowa's prairie long ago fell victim to the plow or the pavement. But because the Loess Hills are often too steep for row crops, pockets of high-quality virgin prairie remain. Big bluestem, little bluestem, sideoats grama, prairie clovers, lead plant, and dozens of other grasses, sedges, and flowering plants mottle the hills. Once fodder for long-vanished herds of bison, elk, and pronghorn, they still offer a rich harvest to wild turkeys, pheasant, and bobwhites, and refuge for foxes, mink, and badgers.
Herons and ducks shelter in the creeks and ponds. By day, birds of prey wheel overhead, vultures and many breeds of hawks. By night, great horned and barred owls take over. The hills are also home to some animals more common in the far West. In places, the parching winds from the western plains and the intense heat of the afternoon sun create a desert-like environment for plains pocket mice, ornate box turtles, Great Plains skinks, and prairie rattlesnakes.
Cattle have overgrazed some areas. Developers mine for fill dirt. Road construction leaves exposed cuts prone to erosion. Affluent homeowners fleeing the sprawl of Omaha, Council Bluffs, and Sioux City set up ten-acre ranchettes, "landscaping" their rural getaways with invasive trees and fragmenting habitat with new roads. All this settlement brings perhaps the most powerful threat to the survival of the prairie: fire suppression. Without the occasional blaze, prairie quickly becomes overgrown with trees, which can't hold the fragile loess soil the way prairie vegetation does.
When Lewis and Clark passed within a few miles of this spot 200 years ago, it was largely a treeless landscape. Back then, fire would scorch any given patch of prairie every four to seven years. In autumn, the dry plants could fuel towering flames and intense heat. In 1832, the painter George Catlin described one as a "Hell of fires." These conflagrations could advance faster than a man on horseback could flee, but they were as vital to the survival of a prairie as water itself. Prairie plants evolved root systems up to 15 feet deep to survive the flames.
To bring fire back, Pape and his crew are part of a network of prescribed-burn fire-setters called the Stewardship Committee. Of the hills' 650,000 acres, only about 18,000 — a patchwork of state, county, and privately owned parklands — are under any sort of conservation management. The committee does its best to burn those areas as regularly as nature once did. It's a sort of latter-day ecological posse, a band of professionals trained in fire management that convenes whenever and wherever conditions are right to incinerate bad guys like overgrown sumac, dogwood, eastern red cedar, and the invasive Siberian elm.
Members are a varied bunch: a Nature Conservancy land manager here, a county conservation worker there. No one has the equipment or staff to burn their individual acreage. But together, through an informal barter system, they form a roving prairie fire.
Pape's ignition crew pushes chest-deep into the grass, which is dense and stiff and pushes right back. Drip torches upended, they sprinkle liquid fire onto the vegetation as they walk. The wind picks up, and soon a solid line of flame sweeps down the hill and up the next. To control it, some of the crew become walking fire hydrants, strapping bladder bags of water on their backs or wielding long poles with large rubber flappers on the ends to smother stray fires.
It takes less than an hour to transform the patch of lush prairie into a smoking black blanket. All around, the scorched skeletons of hundreds of young sumac trees stand, still vertical but ready to disintegrate into ashes. In a few weeks, this area will be green again.
THE PERIPATETIC PYROTECHNICIANS aren't the only ones dedicated to greening the prairie. Love of the hills has also grown in natives like David Zahrt, who has changed over his lifetime from third-generation cattleman to ardent defender of the prairie. "People ask me where I'm from," he says, "I say I'm from the West Coast. Of Iowa."
Having spent a good part of his 67 years outdoors, Zahrt is mindful of the sun and stops for a smear of sunblock on his arms and face before stepping off the back porch and heading up into the hills about 45 miles south of Sioux City. His family acreage in the Loess Hills is now a bed and breakfast, where the price of an overnight stay often includes a guided prairie hike. Every ridge, every plant prompts a story.
"This is lead plant," Zahrt says, pulling at the seeds of a plant with tiny rows of dull blue leaves. "It appears as if it's already flowered." From here on, Zahrt grasps at lead plants left and right, raking the seeds off between his thumb and fingers and dumping them in a plastic jug hanging from his belt.
It's impossible to take in the beauty of a healthy prairie on a single day, not when it contains as many as 150 different species of plants, each with its own moment of glory in the passage of the year. "The procession starts way back in April," Zahrt says. "You get the pasqueflower, then the ground plum. Then you get the hoary puccoon, then the prairie ragwort and the prairie violet, and it's just one procession after another."
Some of these plants fill a hillside with color, some hide down among the grasses. Like a good pointillist painting, a healthy prairie needs to be appreciated both up close and from afar. When the flowers fade in autumn, the grasses take over, exhibiting rich russet tones. Even early winter has its display, as seed heads dry into intricate and pleasing shapes.
At the top of a particularly steep ridge, Zahrt spots an ecological oddity of the Loess Hills. It's yucca, a desert plant usually found a time zone or two west of here.
"Are you familiar with the yucca seed?" Zahrt asks, and scurries down a nearly vertical bluff better suited to a goat than to a potential AARP member. A few minutes later, he bounces up with his reward, a well-formed yucca seedpod. "This is what it looks like when it's all through, see." He splits the pod to reveal a tight stack of flat black seeds.
"There's a moth that has symbiosis with this plant," Zahrt says. "It depends on the yucca or it's not going to live. And the yucca depends on the moth for pollination." Unlike insects that pollinate a variety of flowers, the Pronuba moth seems designed to no end other than yucca propagation.
It gathers pollen from one yucca's stamen, stows it in a special appendage, and deposits it on another yucca's pistil. Then the female buries her eggs in a seedpod, where her larvae will feast on yucca seeds. Not too many seeds, though: The moth leaves enough pods egg-free to keep the plants coming. Sustainable agriculture, arthropod style. The next pod Zahrt splits open reveals no seeds, but a sodden mass of brown mush. "The moth takes his price, see?"
Later, back at the house, Zahrt shows off his prized player piano. From a red cardboard box, he extracts a paper roll, Cole Porter's "Don't Fence Me In."
"I claim that Cole Porter wrote this about the hills," Zahrt says. "In the chorus, it says, ÔI want to ride to the ridge where the West commences.' You find the yucca naturally along this ridge. You find the yucca in New Mexico. So there's botanical evidence that this is the ridge where the West commences." We sing.
And sing. Cole Porter gives way to the music of Sylvan Runkel, Iowa's late, revered state naturalist, a champion of prairies, and a friend of David Zahrt's. The piano is mute as Zahrt's smooth back-porch baritone rises into a rendition of Runkel's "Ode to the Loess Hills."
Away, away then I must go.
Up into these hills where the prairies grow.
And nature speaks to let us know
the wisdom in a flower.
Partway through, the leathery Iowa guy pauses to hold back the tears.