When Deng Xiaoping disbanded Chairman Mao’s “people’s communes” in the late 1970s, few realized that the act would lead to unprecedented mass migration. Few now grasp the implications. It’s conventional wisdom to say that China will be the superpower of the next century. For years, businessmen and Western politicians have been waiting–half in anticipation, half in dread–for the moment when China stirs. But unless Beijing can find a way to control the tidal wave of humanity heading for the coastal cities, China will be presented with vast breeding grounds of urban unrest. Teeming shantytowns with epidemics of disease, crime and inequality may threaten both the economic revolution Deng unleashed and China’s stability.

What explains such a dire prediction? In large part, the collapse of China’s experiment to organize agriculture on Maoist lines. For decades, collective farms doubled as a vast Chinese gulag. Unproductive peasants remained tied to the land–and were kept out of model cities. Deng, in effect, opened the prison door. When China’s manufacturing sector came alive in the 1980s, peasants began packing off to seek their fortunes in urban factories. Since Mao’s death in 1976 enough of the rural poor have fled the countryside to populate Shanghai five times over. Next year another Shanghai’s worth–about 15 million–might make the same journey.

For those in the paddy fields of the interior, the cities offered seductive promise. “Each time a migrant worker visits home in city clothes and jewelry, everyone asks the same question: ‘How can I go, too?’ " says Dai Yuanchen, a senior economist at the Chinese Academy of Social Sciences. One trailblazer is former Jiangsu peasant Zhou Di, 45, who has worked as a maid in Beijing since 1978. The $150 a month she now earns bankrolled her son’s wedding and a new farmhouse in her village, with flush toilets and running water. “I don’t buy clothes or wear makeup,” she says, “so things are a bit easier at home.”

Most peasants quit their ancestral homes out of economic necessity. In Duyun, a remote prefecture deep in the mountains of Guizhou province, half of the area’s 3.8 million people live below Beijing’s poverty line of $1 a week. Extraordinarily, ninny are worse off today than they were under Mao. The demise of communal farming has meant fewer entitlements–including guaranteed grain rations, subsidized medical care and free schooling. That has sent peasants scattering in search of wage-paying jobs. Duyun’s governor, Lan Tian-chuan, says that more than 300,000 locals have decamped to coastal cities since 1990–10 times more than the number employed by all the industrial enterprises in his prefecture.

But often, city life is no escape. Those neon lights that now shine as brightly in Shanghai as Hong Kong obscure more than they illuminate. Migrants are treated as second-class citizens. In China’s climate of endemic corruption, police routinely check new arrivals for resident permits (which most don’t have) simply to extract bribes. Migrant children don’t get vaccinations for polio and tuberculosis–because of either clinics that won’t accept them or parents who fear to go. Peasant girls fill the brothels of Shanghai. Gangs organize orphans who panhandle on the streets. Most city dwellers are unsympathetic. As one Beijing man put it: “These bumpkins cause chaos. They should go home.”

Such hostility has bred its own reaction. For their own security, peasant refugees now cluster in ethnic ghettos-virtual Chinatowns in China. The enclaves have effectively become the home of an urban underclass that shows every sign of being permanent. And this underclass threatens the old labor elite-workers in unprofitable state factories, 30 million of whom could be laid off by 2000. “Peasants will be their natural competition,” warns one State Council planner. “The coming conflict hasn’t yet been addressed.”

That conflict is the nightmare of foreign investors. At the best of times, it’s hard doing business in China. In the middle of an economic war between China’s workers and its underclass, investment won’t be worth the risk. In Maoist times, the solution would have been easy: the government in Beijing would have used internal passports and terror to keep peasants in the countryside. Not now; China’s changed too much. Instead, Beijing should try to balance development between the rich coast and the vast but poor interior. New inland jobs could keep peasants down on the farm. In an ideal world, China might start its own “New Deal” to upgrade roads, railways and power stations in the hinterlands. Yet China’s government is heavily in debt, Any additional spending on the scale required would probably just fuel inflation, with its own risks of social unrest. The alternative–increasingly likely–is poverty, disease and hopelessness, in the most populous cities that the world has ever known. Imagine that, in the first years of the next century–and keep your fingers crossed.