Lovesick Grass, Foreign Tubers, And Jade Rice

TRADE BROUGHT MORE THAN SILVER ACROSS the Pacific. It also brought American plants to China, plants that would quickly change Chinese life.

Tobacco may have led the parade. It was as much a sensation in China as in England and Spain. One Chinese name for tobacco was “lovesick grass,” for the way users became addicted to it. Ming soldiers embraced tobacco and spread the practice of smoking it as they marched around the empire. The fashionable rich showed off their tobacco addictions. Men boasted of being unable to eat, talk, or even think without a lighted pipe. Women carried special silk tobacco purses with jeweled fastenings. China’s legions of enthusiastic smokers were not aware of tobacco’s toxic effect on human health—that fact about tobacco was not clearly established until the twentieth century. By that time, China had been shaped, for better and worse, by tobacco and the other plants that came to China as part of the Columbian Exchange.

Tobacco was only part of an unplanned ecological invasion that had far-reaching consequences. Tobacco sparked a smoking craze, but the other invaders changed China’s food supply.

At the time that the Columbian Exchange began, China had about a quarter of the world’s population. It had to feed these people on about a twelfth of the world’s farmable land. At least half of the national diet consisted of rice and wheat. Unluckily, the areas within China that have enough water to grow rice and wheat are rather small.

China has many deserts, few big lakes, and irregular rainfall. It has only two big rivers, the Yangzi and the Huang He (Yellow River). Both run long, looping courses from the western mountains to the Pacific coast, emptying into the sea scarcely one hundred fifty miles from each other. The Yangzi carries water from the mountains to the rice-growing flatlands near the end of its course. The Huang He carries water into the North China Plain, the center of wheat production. Both areas are vital to feeding the nation, and both are prone to catastrophic floods. The Chinese imperial dynasties managed huge, complex systems of dams and canals to control the rivers and irrigate fields.

With little good farmland relative to the size of its population, China saw the Columbian Exchange, which brought new food plants, as a gift—and raced to embrace it. Sweet potatoes, corn, peanuts, chile peppers, pineapples, cashew nuts, and manioc (also called cassava) poured into Fujian province through the galleon trade, which had brought these plants from the Americas to the Philippines. The same plants reached other provinces by way of Dutch and Portuguese traders. All became part of Chinese life, and have remained so. Today China grows three-quarters of the world’s sweet potatoes and is the second-largest producer of corn after the United States.

Sweet potatoes were probably native to Central America. Spanish ships carried them to the Philippines, where they were quickly adopted by the local people, who already grew the food plant taro, which has a big, starchy, sweet-tasting root. Like taro, the sweet potato has leaves and stems above the ground, while the edible part of the plant is a modified stem that stores nutrients below the surface. A Fujianese merchant had tasted sweet potatoes in the Philippines and liked them, so in the early 1590s he smuggled a few of the plants home past the Spanish cargo inspectors. (The inspectors did not mean to prevent the export of sweet potatoes specifically. They simply did not want to give away anything that might be profitable.)

Fujian was lucky that the sweet potato arrived when it did. The 1580s and 1590s were an intense part of the Little Ice Age in China. For two decades, hard floods had washed away the rice paddies of Fujian. Poor families were reduced to eating bark, grass, and insects. The son of the merchant who had brought the sweet potato to Fujian showed the tuber to the governor of Fujian, and soon the governor was instructing farmers to grow the new food crop. Before long, four-fifths of the people in the port city of Yuegang were living on sweet potatoes. The crop spread through the province just in time for the fall of Beijing to the Manchus in 1644, which ushered in decades of violent chaos.

A group claiming to be a continuation of the Ming dynasty took root in Fujian after 1644. At the same time, pieces of the Ming military splintered away and became wokou, or pirates—while the actual wokou also took advantage of the confusion to step up their activities. To cut off food supplies to all these groups, the new Manchu dynasty, the Qing, forced the population in a 2,500-mile stretch of China’s coastline to move into the interior of the country. Soldiers burned seaside villages and privately owned ships. Families had to leave with nothing but their clothing. Anyone who stayed behind was killed. For three decades the shoreline was empty of people for as far as fifty miles inland.

The coastal people flooded westward into the mountains of Fujian, Guangdong, and Zhejiang provinces. These highland areas were already inhabited, mostly by people from a different ethnic group, the Hakka. For a century poor Hakka and other mountain peoples had been migrating west into the mountains, renting highland areas that were too steep and too dry for rice farming. They cut and burned the tree cover and grew crops such as indigo (a plant that produces a blue dye) to sell. After a few years of slash-and-burn farming, the thin mountain soil was exhausted, and the Hakka moved on. Landless and poor, they were mocked as pengmin, or “shack people.”

Because the shack people could not grow China’s traditional wheat and rice on their steep rented fields, to feed themselves they turned to the new American crops. Corn can thrive in amazingly poor soil, and it grows quickly. Brought in from Portuguese traders, it became known in China as “jade rice.” Sweet potatoes will grow where even corn cannot, tolerating soil with few nutrients. Another American import, the potato, originally bred in the Andes Mountains, also took root in the mountains of China. Yet in the decades after the American crops swept into China’s highlands, the richest society in the world was thrown into turmoil by a struggle with its own environment—a struggle it lost.

A seventeenth-century portrait of the powerful Mingdynasty pirate king, Zheng Chenggong.

A TRUE PIRATE KING

WHEN THE QING DYNASTY FORCED THE people of coastal China inland in the middle of the seventeenth century, the evacuation brought an end to trade between the merchants of the coast and the Spaniards in Manila. The only ones able to carry on the trade were the wokou, or pirates.

The pirate trade came under the control of a man named Zheng Chenggong, who had spent his life breaking the laws of the Ming dynasty. When the Qing took over, Zheng realized that the wokou had been better off under the Ming. He led an enormous sea-based assault on the Qing that came close to toppling the new dynasty. Afterward he returned to piracy, with a fleet that one observer estimated at fifteen to twenty thousand vessels. Based in a palace across the river from the trade city of Yuegang, Zheng controlled China’s entire southeast coast. He was a true pirate king.

Starting in 1657, Zheng carried on trade with Manila, exchanging Chinese goods for silver. Perhaps he was distracted by his ongoing battle with the Qing, because it took him until 1662 to realize two things. First, the Spaniards had no other source but him for silk and porcelain. Second, he, Zheng, was a pirate king with a huge fleet and a large army. He suggested a new trade arrangement to Manila. The Spaniards would give him all their silver, as before. In return, he would not kill them. Panicked, the Spaniards forcibly rounded up the Chinese in the Philippines, slaughtering many and sending the rest away on packed ships. This precaution turned out to be unnecessary. Two months later, Zheng died unexpectedly, probably of malaria. His sons fought over their inheritance, and the Manila trade was left alone.

The Qing had ordered the removal of people from the Chinese coast, but this had disastrous effects on them. Closing off the silver trade froze China’s money supply. Because silver was always being wasted, lost, or hoarded and secretly buried, the pool of Chinese money was actually shrinking. The Qing reluctantly lifted the ban on the silver trade in 1681.

In addition to forcing coastal people to move to the highlands of the interior, the Qing dynasty encouraged an even larger wave of migration into the dry, mountainous west. The Qing believed that sending people from the center of the country to occupy the thinly settled western hills, home to many non-Chinese peoples, was essential to the nation’s destiny. Lured by tax benefits and cheap land, migrants from the east swarmed west. Most of the newcomers were as poor as the shack people. Like the shack people, they cut down trees and planted sweet potatoes, corn, and later potatoes on the steep slopes of their new homes. The amount of cropland in China soared. So did the amount of food grown—and the population. In some places the number of inhabitants grew by a hundred times in little more than a century.

For almost two thousand years, China’s population had risen very slowly. This changed during and after the violent Qing takeover. Between the arrival of American crops and the end of the eighteenth century, China’s population skyrocketed, possibly doubling to about 350 million people. Were the new crops the only reason for this population boom?

No. The crops arrived as the Qing were already transforming China. The ambitious dynasty fought disease and hunger in many ways. The Qing started the world’s first program of inoculations to protect people from smallpox. They enlarged the nationwide network of food storehouses that bought grain and sold it at low, state-controlled prices during shortages. Still, most of the population increase took place in areas with American crops. The families that the Qing encouraged to move west needed to eat, and what they ate, day in and day out, was sweet potatoes, corn, and later potatoes. Part of the reason China is the world’s most populous nation is the Columbian Exchange.

The huge increase in cropland came with consequences. Once trees were cut from steep slopes, rainwater rushed downhill, carrying soil nutrients with it. Farmers unfamiliar with raising corn did not at first realize that planting rows straight up and down the hills, rather than in lines across the slope, would channel the rain down the slope, worsening soil erosion. Also, people who merely rented their fields, unlike owners, were not strongly motivated to fertilize the soil with ashes and manure to replace the nutrients that went into their crops or were washed away by flowing water. As a result, soil in the newly farmed hills quickly deteriorated.

Deforestation in the hills also caused disaster below, in the flatlands along the rivers. Rainfall went down the hills in sheets, instead of being absorbed by trees. The rivers swelled and poured over their banks in devastating floods. Drowned rice paddies of the lower Yangzi drove up the price of rice, which encouraged more corn production in the highlands, which drowned more rice in the valleys. Floods became more frequent as more shack people moved into the mountains. Worse, the floods mostly targeted China’s major agricultural centers, the rich farmlands along the lower Yangzi and Huang He (Yellow) Rivers.

Part of the problem was large-scale immigration, but part of it was a legal loophole. The income from farms was taxed, but the income from rental property was not. Landowners who had property in the highlands had an easy source of untaxable income by renting that property out to shack people and migrants. The deforestation of their highland property might contribute to floods that would affect their own fields in the lowlands, but the risk of floods was spread across a whole region, while the income from their rental property was theirs alone. Local business interests with rental property beat down every attempt to rein in the shack people. It was an environmentalist’s nightmare. The shortsighted pursuit of small- scale profits steered a course for long-range, large-scale disaster.

Constant floods led to constant famine and constant unrest. Repairing the damage of the floods drained the resources of the state. American silver may have pushed the Ming dynasty over the edge. American crops certainly helped kick out the underpinnings of the tottering Qing dynasty, which collapsed in 1911. To be sure, other things contributed to the fall of the Qing. A rebellion led by a Hakka mystic tore apart the state, and a series of weak emperors did nothing to combat government corruption. The empire also lost two wars with Great Britain, which forced China to open its borders to the British-backed trade in the narcotic drug opium. Yet the path to the Qing downfall had been opened by the Columbian Exchange.

In 1963, floods ravaged Dazhai, a village of a few hundred people in the dry, knotted hills of north-central China. Standing in the wreckage, the local secretary of the Communist Party refused aid from the state and promised that Dazhai would rebuild itself—and create a new, more productive village. He was as good as his word. Harvests soon soared, in spite of the flood and the infertile soil.

Mao Zedong was the head of the Communist state that had taken control of China in the mid-twentieth century. He was delighted by Dazhai’s increase in food production. Mao bused thousands of local officials to Dazhai, telling them to copy what they saw there. Mainly, they saw peasants working furiously to build terraces from the top to the bottom of each hill. They vowed to do the same in their villages. Filled with excitement, and lashed on by their local officials, villagers fanned out across the hills, cutting the scrubby trees, slicing the slopes into terraces, and planting what they could on every surface. The terraces turned unplantable steep slopes into new farmland.

Dazhai is located in a geological formation called the Loess Plateau, an area about the size of France, Belgium, and the Netherlands combined. For ages, winds have swept across the deserts to the west, blowing grit and sand into the Loess Plateau. This has created vast heaps of packed silt—or loess, as geologists call it. Loess doesn’t form soil so much as pack together like wet snow—when it is dry. Yet silt piles are easy to wash away. They don’t clump together firmly. If silt grains are knocked free by flowing water, they move easily. Washed down steep hills, these particles can be carried great distances. The Huang He makes a big loop right through the Loess Plateau. It carries an enormous burden of silt from the plateau right into the North China Plain, the country’s agricultural heartland.

Because the plain is flat, the water slows down and deposits silt on the bottom and along the banks. The silt renews the soil, which is one reason the plain is so good for agriculture. At the same time, though, the silt builds up the riverbed and banks, raising the Huang He one to three inches above the surrounding countryside each year. Over time, the river has lifted itself as much as forty feet above the land around it. Every so often the Huang He overflows or breaks its banks, creating a ruinous flood. In the eighteenth and nineteenth centuries, erosion on the Loess Plateau caused more frequent, and more lethal, floods in the plain. Chinese court records show that excess silt made the Huang He overflow its banks in huge floods a dozen times between 1780 and 1850. A flood in 1887 was among the deadliest ever recorded, with the number of deaths estimated at up to a million.

The cause of the flooding (deforestation of the Loess Plateau to plant corn and sweet potatoes) was well known. Yet the government did nothing about it, and neither did the landlords who rented to the shack people. Instead, the floods continued until the Qing dynasty fell, an event that the floods had helped bring about—which made it all the more incredible when Mao Zedong ordered more land cleared in the Loess Plateau, in the Dazhai style. In the 1960s and 1970s the steepest hillsides were targeted to be turned into productive farmland. Yet the terrace walls, made of nothing but packed earth, constantly fell apart. During the “Dazhai era,” as this period was called, soil erosion into the Huang He increased by about a third.

The consequences were dire and easy to see. As nutrients washed out of the soil, harvests fell, forcing huge numbers of farmers to become migrants. The Loess Plateau, which once caught dust from the desert, began producing dust clouds of its own as its dry, exposed soil blew away. Vaclav Smil, a geographer who has made a long study of China’s environment, says, “It must be one of the greatest wastes of human labor in history. Tens of millions of people being forced to work night and day, most of it on projects that a child could have seen were a terrible stupidity. Cutting down trees and planting grain on steep slopes—how could that be a good idea?”

In an effort to halt deforestation, the government in 1981 required every able-bodied citizen older than eleven to plant three to five trees a year whenever possible. Three years earlier Beijing had launched what may be the world’s biggest ecological project: planting a 2,800-mile-long band of trees across northeast, north, and northwest China. Scheduled to be completed in 2050, this Green Wall of China is supposed to slow down the winds that drive desertification and dust storms.

To remedy the damage to soil in places such as Dazhai, farmers are now following the “3-3-3” system. They replant a third of their land (the steepest, most erosion-prone slopes) with grass and trees, which are natural barriers to erosion. They plant orchards of food-producing trees on another third. On the final, flattest third, they plant crops that they fertilize. Local officials are rewarded for the number of trees they plant, but unfortunately they have not been required to choose tree species that are suited to local conditions. Also, while the government has the power to order whole villages into the hills to plant millions of trees, farmers have little reason to water or care for trees they cannot use just because the trees supposedly stop erosion miles from their homes.

Beginning in the 1960s, farmers in China’s Loess Plateau stripped the forest and carved terraces out of the hills. Because the loess erodes easily, every rainfall caused damage to the terraces. Eventually, the terraces built on the steepest slopes collapsed. Farmers tried to make a living on hills almost too steep to stand on.

The result is fields of dead trees. When I visited Shaanxi province in the Loess Plateau, farmers told me, “Every year we plant trees, but no trees survive.” During my visit, lines of dead trees dotted the slopes, stretching for miles. The harvest was over, and farmers were about to be marched back for another round of planting. Despite previous failures, China’s government is trying, tree by tree, to undo the accidental legacy of the global silver trade.

Sweet potatoes in China are often eaten raw, the skin whittled until they look somewhat like ice-cream cones.