Image of the New York City skyline.
Image of the New York City skyline.

A hundred years ago, only 20 percent of the world's population lived in urban areas, but the 20th century saw a dramatic shift that marks a turning point in history. Today, more people live in cities than in rural areas, and urbanization continues to grow around the world. According to the World Bank, city living is much more efficient in a variety of ways. It's easier to provide services when people live closer together. However, cities also change the way that humans interact with each other and the environment, often causing multiple problems.

Health and Human Services

When families move into urban areas, they automatically place themselves in closer proximity to basic services such as hospitals and schools -- urbanization often brings health care and educational opportunities to those who might not have had access to them in rural areas. Cities also offer public transportation, government run sanitation services and social programs such as libraries, health clinics and children's programs. For many people, especially in developing countries, access to these services offers many advantages in terms of creating opportunities.

Job Opportunities

As large-scale agriculture displaces many traditional farmers from the rural lifestyle, the tremendous growth of modern industry in large urban areas attracts people with the promise of employment. In general, urban wages are significantly higher, so moving to the city is an opportunity to earn that was impossible in rural areas. However, the wage difference is often offset by the higher cost of living and absence of self-produced goods, including subsistence farming.

Inequality, Crime and Poverty

Those who move from rural areas to urban ones sometimes find themselves living in shanty towns or slum areas. These new city residents are faced with problems that do not exist in the countryside: street crime, including gangs, as well as social inequality and discrimination. The urban poor struggle to make a living, even if they do earn more than they did in rural areas, because the cost of city life is significantly higher and the opportunities to produce their own food and other basic necessities is greatly reduced.

Pollution and Contamination

Traffic congestion and industrial manufacturing, prominent features of the urban landscape, also take their toll on the natural environment and those who depend on it. Lack of clean water is a major problem among the urban poor in major cities around the world, as is air pollution from both cars and factory emissions. In fact, according to an article in the "British Medical Journal," almost 10 percent of the world's disease burden is now caused by pollution and contamination, and the number is significantly higher among the poor in developing countries. For many, and especially those who moved to urban areas for opportunity, city living proves deadly in ways not known in the countryside.