When observing the chaotic, burgeoning growth of the modern city, the more erudite urban planners will reminisce wistfully on how different it is from its ancient Greek counterpart, the polis, which Italian architect and historian Leonardo Benevolo once described as "dynamic but stable, in balance with nature, and growing manageably even after reaching large dimensions." The challenge facing modern society is to strike a balance between human needs and those of the physical surroundings.

The rapid and uncontrolled sprawl of today's cities breeds anxiety not only among urban planners and architects. Experts in the field of public health are alarmed as well, for the apparent randomness of the urban dynamic is robbing the population of its basic health and well-being through unregulated environmental pollution, shrinking green areas, inadequate housing, overburdened public services, a mushrooming of makeshift settlements on the outskirts lacking in both infrastructure and services, mounting anomie and the sheer numbers of neighbors who do not know their neighbors. As Li Keqiang, the outgoing premier of China has stated, “Urbanization is not simply about increasing the number of urban residents or expanding the area of cities. More importantly, it’s about a complete change from rural to urban style in terms of industry structure, employment, living environment and social security.”

The lesson in Beijing

Beijing, a city of 21,330,000 million inhabitants, exemplifies this social alienation. Until the early 1980s, the Chinese capital was constructed as a multitude of siheyuans, or one-story complexes built around a common courtyard that was inhabited by three or four families who shared a single kitchen and water spigot. These courtyards were connected by narrow streets called hutongs that formed a grid from north to south and east to west.

This open structure greatly facilitated contact between neighbors, encouraged the sharing of resources, fostered relations between contiguous families, and enabled the elderly to care for children and share with them their passion for songbirds. Because of these characteristics, these almost idyllic structures were described as "collections of small rural villages."

Until the mid-1980s, only a few skyscrapers disrupted the harmony of the landscape. Today that panorama has the look and feel of the ultimate modern city, where, with few exceptions, these "small rural villages" have been supplanted by sterile, towering skyscrapers. This striking change is not limited to external structure; it has dramatically altered the fabric of human relations as well.

Physical isolation has led to an increase in crime, destroyed the local sense of solidarity, and contributed to the fragmentation of what were once cohesive family groups. As the distance between home and the workplace has also increased considerably, workers now find themselves devoting what was once valuable family time to exhausting commutes in overcrowded buses or subways. According to Chen Xitong, former mayor of Beijing, "the capital is growing increasingly ugly and it is steadily losing its Chinese character. Most of the modern high-rise buildings, with their boring concrete facades, look like dominoes set down in the landscape without plan and without imagination."

Population growth

Rapid urbanization is related in part to population growth and rural migration to large cities. In mid-1994, the global population was 5,660 million; estimates from the United Nations place it at almost 8 billion by 2022. According to the United Nations Conference on Trade and Development (UNCTAD), the world population has increased by 2.5 billion people in the last 30 years. The bulk of this growth has occurred in the parts of the world least able to cope: Asia, Africa, and Latin America. This growth is particularly noticeable in Africa, where the rate of annual growth is 2.5 percent, more than double the rate of world growth. Africa has today 1.4 billion people and it is estimated that by the end of this century it will be home to 3.9 billion people, or 40 percent of humanity.

By 2050, an additional 2 billion people will live on earth. At the global level, a growing proportion of the population lives in cities. The increase is generally higher in the developed (79.2) percent in 2020) than in the developing world (51.6 percent). Even the term "urban sprawl" may soon require redefinition. The first urban zone described as a megalopolis was the continuous 400 miles stretch that goes from New York to Boston. Today, Rio de Janeiro and São Paulo have blended to form a continuous 350-mile-long megalopolis called the Brazilian Megalopolis, of over 40 million people. In Africa, another megalopolis starts in Abidjan, the economic capital of Ivory Coast, and extends east for 600 miles through Ghana, Togo and Benin, until arriving in Lagos, Nigeria. In Japan, the Taiheiyõ Belt, also known as the Tõkaidõ corridor, is the megalopolis in Japan that extends from Ibaraki Prefecture in the northeast to Fukuoka Prefecture in the southwest, running for almost 1,200 km. Its population is about 74.7 million. And new city clusters are now growing in India, China and Europe.

Migration

The unchecked growth of the cities is also due to migration, both domestic and external, that many countries are experiencing. The common denominators here are rural poverty, the search for better social and employment opportunities, and flight from political persecution and violence.

Colombia has a long history of rural violence dating back to the 1930s. Between 1948 and 1957, more than 250,000 murders were committed during an undeclared civil war between members of the liberal and conservative political parties. Caught in the middle were thousands of landless peasants who took flight for the relative safety of the larger cities.

Colombia's case is certainly not unique. More recently, the rural poor in many other countries of this hemisphere have been uprooted by violence and forced to flee en masse toward the large urban centers, where they all too often are forced into marginal areas.

These marginal areas, known as bidonvilles in French-speaking West Africa, ishish in some Arab countries, kampungs in Indonesia, villas miseria in Argentina, favelas in Brazil, pueblos jóvenes in Peru, and ranchitos in Venezuela, may contain from 30% to 60% of the population of many Third World cities, according to Worldwatch Institute.

Since the 1950s, many governments have attempted to discourage migration from rural areas to cities, but these measures are by and large unsuccessful. Since large cities enjoy preferential treatment in terms of infrastructure and industrial development, they serve as magnets for the poor.

Regardless of the big city's allure, many observers now feel that living conditions for the ever-growing numbers of urban poor are most likely worse than for their rural counterparts. The true dimensions of this phenomenon remain elusive, says World Health Organization expert Dr. I. Tabibzadeh, because the poor are either omitted from official statistics or are not considered separately.

Migrations between countries also continue unabated, usually stimulated by the same factors responsible for internal migration. Today, millions of people worldwide are living in a country not their own, in search of better economic and professional opportunities or to escape political violence.

The Latin American country that has produced the greatest number of migrants is Mexico. Out of a total of nearly 11.2 million Mexican emigrants around the world in 2020, almost 10.9 million relocated to the United States, where income opportunities are greater. In the Southern Cone, Argentina is the main destination for migrants from Paraguay, Uruguay, and Bolivia. In Central America and the Caribbean, the U.S. is the most frequent destination, although there are also significant migratory flows from the Dominican Republic to Venezuela and Puerto Rico, and from Haiti to the Dominican Republic.

The impact of rapid urbanization on health

Movements, whether from rural to urban areas or from one country to another, often alter the characteristic epidemiological disease profile at the same time that new diseases appear, and old ones reemerge. For example, large-scale migrations to Costa Rica in the 1980s stemming from conflicts in other Central American countries produced a palpable increase (especially along border areas) in the prevalence of malaria and other infectious and parasitic diseases.

While it is true that the more obvious ill effects of urban life (emotional stress, loss of family structure, congested traffic, noise, environmental pollution) are democratic in their distribution pattern, many city dwellers take for granted access to basic public services, such as drinking water supply, housing, solid waste disposal, transportation and health care. For the poor, however, these are either deficient or nonexistent. Instead, those in poverty zones usually receive an extra dose of environmental pollution, since industries tend to cluster in outlying areas where regulations are laxer.

Horror stories abound concerning the effects on humans of environmental degradation. For example, studies show that exposing pregnant women to carbon monoxide can damage the health of the fetus. Scientists also agree that the lead particles released as a result of gasoline combustion pose a significant potential threat to children, whose behavior and psychosocial development can be seriously affected. In Mexico City, a city notorious for its air pollution, children are exposed to an average of 4.5 million tons of contaminants.

Yet Mexico City's pollution problem is hardly unique; virtually every major city in the hemisphere is fighting the same battle. Residents of Santiago, Chile, are afflicted with a host of chronic respiratory infections caused by large concentrations of particulate pollutants in the atmosphere, whose persistence is, in turn, facilitated by the area's unique topographical and climatic circumstances. Buenos Aires is not exempt from this problem either, and its toxic gas and noise pollution levels make the Argentine capital one the most polluted cities in the world.

Air pollution is running a neck-and-neck race with other forms of pollution stemming from solid waste, pesticides, and toxic industrial waste. In Santiago, an estimated 300 million cubic meters of untreated waste are discharged annually into the metropolitan area's two rivers and the principal irrigation canal, while in Nicaragua, DDT levels in breast milk are 45 times higher than the World Health Organization limit. This toxic waste affects wildlife as well. At the Silva Dam near Guanajuato, Mexico, more than 40,000 birds in a seasonal migration from Canada and the U.S. died as a result of pollution by chromium and other substances used in the processing of hides and skins.

In addition, many houses in developing countries’ disaster-prone areas are built with fragile materials and construction, which makes them more vulnerable to natural disasters such as earthquakes, floods and hurricanes, which leads to the loss of many lives. Even people in developed countries are now suffering the effect of these natural disasters which are becoming more frequent and their consequences more serious.

Benefits of urbanization

Not all are disadvantages in the rapid urbanization process of modern cities, however. What determines if urbanization is beneficial or not are the particular conditions in which it occurs.

While planned urbanization can be very beneficial, unplanned or poorly planned urbanization can lead to unwelcome results. Cities offer governments cost advantages in the delivery of goods and services, such as easier access to health facilities which are a hindrance in many rural areas. In addition, cities play an important role in reducing fertility levels, thus slowing population growth. Urban women more frequently use modern reproductive health methods than their rural counterparts. Social and cultural norms make it more acceptable for couples to have smaller families in urban than in rural areas. Women in urban areas also take advantage of better educational opportunities. When properly planned, immigration to cities of people from different cultural backgrounds increases opportunities for cultural integration and brings exciting new habits, such as new foods and beliefs, that enrich people’s cultural and social perspectives.

Outlook

The chaotic growth of today's cities can no longer be ignored. The great challenge is how to improve the quality of urban life while ensuring harmonious growth. Cities’ government officials should learn from the experiences of other cities with similar characteristics. This effort requires not only the participation of urban planners but public health and environmental experts, politicians, and fundamentally, the communities themselves. Only when these actions become a reality will it be possible to reach that almost ideal situation heralded by Hippocrates some 2,600 years ago: a balance between the human organism and its environment.