Nevertheless, the Great Wall has endured as a symbol of national identity, sustained in no small part by successive waves of foreigners who have celebrated its splendors—and perpetuated its myths. Among the most persistent fallacies is that it is the only man-made structure visible from space. (In fact, one can make out a number of other landmarks, including the pyramids. The wall, according to a recent Scientific American report, is visible only "from low orbit under a specific set of weather and lighting conditions.") Mao's reformist successor, Deng Xiaoping, understood the wall's iconic value. "Love China, Restore the Great Wall," he declared in 1984, initiating a repair and reconstruction campaign along the wall north of Beijing. Perhaps Deng sensed that the nation he hoped to build into a superpower needed to reclaim the legacy of a China whose ingenuity had built one of the world's greatest wonders.
Today, the ancient monument is caught in contemporary China's contradictions, in which a nascent impulse to preserve the past confronts a headlong rush toward the future. Curious to observe this collision up close, I recently walked along two stretches of the Ming-era wall, separated by a thousand miles—the stone ramparts undulating through the hills near Sun's home in eastern Hebei Province and an earthen barrier that cuts across the plains of Ningxia in the west. Even along these relatively well-preserved sections, threats to the wall—whether by nature or neglect, by reckless industrial expansion or profit-hungry tour operators—pose daunting challenges.
Yet a small but increasingly vocal group of cultural preservationists act as defenders of the Great Wall. Some, like Sun, patrol its ramparts. Others have pushed the government to enact new laws and have initiated a comprehensive, ten-year GPS survey that may reveal exactly how long the Great Wall once was—and how much of it has been lost.
In northwest China's Ningxia region, on a barren desert hilltop, a local shepherd, Ding Shangyi, and I gaze out at a scene of austere beauty. The ocher-colored wall below us, constructed of tamped earth instead of stone, lacks the undulations and crenelations that define the eastern sections. But here, a simpler wall curves along the western flank of the Helan Mountains, extending across a rocky moonscape to the far horizon. For the Ming dynasty, this was the frontier, the end of the world—and it still feels that way.
Ding, 52, lives alone in the shadow of the wall near Sanguankou Pass. He corrals his 700 sheep at night in a pen that abuts the 30-foot-tall barrier. Centuries of erosion have rounded the wall's edges and pockmarked its sides, making it seem less a monumental achievement than a kind of giant sponge laid across gravelly terrain. Although Ding has no idea of the wall's age—"a hundred years old," Ding guesses, off by about three and a half centuries—he reckons correctly that it was meant to "repel the Mongols."
From our hilltop, Ding and I can make out the remnants of a 40-foot-high tower on the flats below Sanguankou. Relying on observation sites like this one, soldiers transmitted signals from the front lines back to the military command. Employing smoke by day and fire at night, they could send messages down the line at a rate of 620 miles per day—or about 26 miles per hour, faster than a man on horseback.
According to Cheng Dalin, a 66-year-old photographer and a leading authority on the wall, the signals also conveyed the degree of threat: an incursion of 100 men required one lighted beacon and a round of cannon fire, he says, while 5,000 men merited five plumes of smoke and five cannon shots. The tallest, straightest columns of smoke were produced by wolf dung, which explains why, even today, the outbreak of war is described in literary Chinese as "a rash of wolf smoke across the land."
Nowhere are threats to the wall more evident than in Ningxia. The most relentless enemy is desertification—a scourge that began with construction of the Great Wall itself. Imperial policy decreed that grass and trees be torched within 60 miles of the wall, depriving enemies of the element of surprise. Inside the wall, the cleared land was used for crops to sustain soldiers. By the middle of the Ming dynasty, 2.8 million acres of forest had been converted to farmland. The result? "An environmental disaster," says Cheng.
Today, with the added pressures of global warming, overgrazing and unwise agricultural policies, China's northern desert is expanding at an alarming rate, devouring approximately one million acres of grassland annually. The Great Wall stands in its path. Shifting sands may occasionally expose a long-buried section—as happened in Ningxia in 2002—but for the most part, they do far more harm than good. Rising dunes swallow entire stretches of wall; fierce desert winds shear off its top and sides like a sandblaster. Here, along the flanks of the Helan Mountains, water, ironically enough, is the greatest threat. Flash floods run off denuded highlands, gouging out the wall's base and causing upper levels to teeter and collapse.
At Sanguankou Pass, two large gaps have been blasted through the wall, one for a highway linking Ningxia to Inner Mongolia—the wall here marks the border—and the other for a quarry operated by a state-owned gravel company. Trucks rumble through the breach every few minutes, picking up loads of rock destined to pave Ningxia's roads. Less than a mile away, wild horses lope along the wall, while Ding's sheep forage for roots on rocky hills.