A megacity is pegged as any city with more than 10 million residents. Another term often used to describe this is conurbation, a somewhat more comprehensive label that incorporates agglomeration areas such as the Rhine-Ruhr region in Germany’s west, which has 11.9 million inhabitants.

Of the 30 biggest megacities worldwide, 20 of them are in Asia and South America alone, including Baghdad, Bangkok, Buenos Aires, Delhi, Dhaka, Istanbul, Jakarta, Karachi, Kolkata, Manila, Mexico City, Mumbai, Osaka-Kobe-Kyoto, Rip de Janeiro, Sao Paulo, Seoul, Shanghai, Teheran, and Tokyo-Yokohama. European megacities include London and Paris, and the UN estimates that the number of megacities worldwide will only increase.

The explosive growth of these and other cities is a rather new phenomenon, a result of industrialization. The megacities of the world differ not only according to whether they lie in the southern or northern hemisphere, but also by country, climatic, political, economic, and social conditions. Megacities can be productive, poor, organized, or chaotic. Paris and London are megacities, but it is difficult to compare them demographically or economically with Jakarta or Lagos. Vibrant megacities tend to stretch out further than their poorer counterparts: Los Angeles’ settlement area is four times as big as Mumbai’s despite its population being relatively smaller. Wealthy city inhabitants have a much higher rate of land consumption for apartments, transport, business, and industry. The situation is similar in terms of water and energy consumption, which is much higher in affluent cities. Cairo and Dhaka are without doubt ‘monster cities’ in terms of their population size, spatial, and urban planning. However, they are also “resourceful cities,” home to millions of people with few resources.

The high population levels in megacities and mega-urban spaces are leading to a host of problems, such as guaranteeing all residents a supply of essential foods, drinking water, and electricity. Related to this are concerns about sanitation and disposal of sewage and waste. There is not enough living space for incoming residents, leading to an increase in informal settlements and slums. Many urban residents get around via bus, truck, or motorized bicycles, leading to chaos on the streets and CO2 emissions leaking into the air.

The faster a city develops, the more critical these issues become. Due to their rapid growth, megacities in developing countries and the southern hemisphere have to battle in order to provide for their inhabitants. Between 1950 and 2000, cities in the north have grown an average of 2.4 times. In the south, they have grown more than 7-fold over the same period. Lack of financial resources and sparse coordination between stakeholders at different levels intensify the problems. Megacities usually do not represent one political-administrative unit, instead of dividing the city into parts such as with Mexico City, which is made up of one primary core district (Distrito Federal) and more than 20 outlying municipalities, where differing planning, construction, tax, and environmental laws are carried out than in the core district.

Two critical causes behind city growth are high rates of immigration as well as growing birth numbers. People move to the city with the hope of a more prosperous life and leave the country in search of brighter prospects. Without careful planning and infrastructure in place, this road can often lead to another poverty trap. As cities grow, so too do the unplanned and underserved areas, the so-called slums. In some regions of the world, more than 50 percent of urban populations live in slums. In parts of Africa south of the Sahara, that number jumps to around 70 percent. In 2007, a reported one billion people lived in slums, and by 2020, that figure could grow to 1.4 billion, according to the UN.

Gated communities are also on the rise. These are fenced and well-monitored communities in which affluent members live, further driving the trend towards separation among urban populations.

However, it is not just living spaces splitting the cities, globally; there is a significant push towards big new building projects like über, modern banks, and business districts, which stand in stark contrast to informal areas for the poor. These central business districts (CBD) are often siloed off from the central part of the city and migrate, along with the gated communities, towards the outskirts of town, as is the case in Pudong, Shanghai, and Beijing.

For the most part, urban planning is based on the needs of the consumer and culture-oriented upper classes and economic growth sectors, with the result being that the gap between rich and poor continues to grow. Such fragmented cities are a fragile entity in which conflicts are inevitable.

Because most people on the planet are city-dwellers, questions are starting to be asked about how to develop and design urbanization and urban migration in a sustainable way. Urban residents, the world over, require good air to breathe, clean drinking water, access to proper healthcare, sanitary facilities, and reliable energy supply.

The current situation in cities in developing countries can be precarious: the air is thick enough to touch; sewage treatment plants, if any, are overloaded, and industrial factories secrete virtually unregulated highly toxic waste and wastewater. Also, climate change will likely hit more impoverished cities harder. However, cities in the developed countries have to deal with environmental challenges in the areas of transport, energy and waste and wastewater.

On an international level, there are countless efforts currently being undertaken to support sustainable urban development. Several large UN projects, such as the UN-HABITAT Program and the Sustainable Urban Development Network, are endeavoring to improve and strengthen governmental and planning abilities. One of the goals of the UMP is also to implement the Millennium Development Goals at the city level.

Many urban problems can be explained not only at the city level, but must be regarded as results of political disorder and economic instability on a global and national level – and that this is where the solutions lie!

Challenges to Urban Growth

One of the major problems that cities face is deteriorating areas, high crime, homelessness, and poverty. As noted in the urban models, many lower-income people live near the city, but lack the job skills to compete for employment within the city. This often results in a variety of social and economic problems. Census data shows that 80 percent of children living in inner cities only have one parent. Because childcare services are limited in the city, single parents struggle to meet the demands of childcare and employment. Problems associated with lower-income areas are often violent crime (assault, murder, rape), prostitution, drug distribution, and abuse, homelessness, and food deserts.

Slums and Shanty Towns

The United Nations defines slums as overcrowded, inadequate, informal forms of housing that lack reasonable access to clean drinking water and sanitary facilities and deprive residents of power of the land. Above all, slums are an architectural and spatial expression of lack of housing and growing urban poverty. The well-known symbols of this are makeshift huts, such as the favelas in Brazil, but also desolate and overcrowded apartment buildings in major Chinese cities where the growing army of migrant workers and workers find makeshift accommodation.

Slums are densely populated urban informal settlements consisting of poor, inadequate living standards. Most slums lack proper sanitation services, access to clean drinking water, law enforcement, or other necessities of living in an urban area.

A shantytown, also known as a squatter, is a slum settlement that usually consists of building material made from plywood sheets of plastic, cardboard boxes, and other cheap material. They are typically found on the periphery of cities or near rivers, lagoons, or city trash dumps.

The reasons so many of these cities are poor include underemployment and insufficient pay as well as low productivity within the informal sector. Around half the people in megacities that lie in the southern hemisphere are employed in the informal sector, many of whom are coerced into accepting any employment. They sell various products – cigarettes, drinks, food, bits, and pieces – simple services like shoe cleaning and letter writing as well as smuggling goods or ending up in prostitution. Exploitation is, at times, rife in slum settings due to insecure residences, lack of legal protection, poor sanitation, and unstable acquisition conditions.

When residents in a neighborhood lack the money, political, organizational skills, or the motivation to protect themselves from disamenities, defined as drawbacks or disadvantages, especially about location, significant neighborhood degradation is possible. Poor people of all ethnicities can rarely afford to live in neighborhoods that have outstanding schools, parks, and air quality. So they are often able to afford to live only in the most dangerous, toxic, degraded neighborhoods. Racism is undoubtedly a common variable in the poverty equation, but it is rarely the only one.

Gentrification and Redlining

As a way for city officials to deal with inner-city problems, there has been a push recently to renovate cities, a process called gentrification. Middle-class families are drawn to city life because housing is cheaper, yet can be fixed up and improved, whereas suburban housing prices continue to rise. Some cities also offer tax breaks and affordable loans to families who move into the city to help pay for a renovation. Also, city houses tend to have more cultural style and design compared to quickly made suburban homes. Transportation tends to be cheaper and more convenient, so that commuters do not spend hours a day traveling to work. Couples without children are drawn to city living because of the social aspects of theaters, clubs, restaurants, bars, and recreational facilities.

The logic behind gentrification is that it not only reduces crime and homelessness; it also brings tax revenue to cities to improve the city’s infrastructure. However, there has also been a backlash against gentrification because some view it as a tax break for the middle and upper class rather than spending much-needed money on social programs for low-income families. It could also be argued that improving lower-class households would also increase tax revenue because funding could go toward job skill training, childcare services, and reducing drug use and crime.

The Federal Housing Authority (FHA), created in 1934 as one of Franklin D. Roosevelt’s New Deal projects, was tasked with ensuring that housing was built safely while encouraging banks to make loans to people seeking to buy new homes or repair older homes, so they were suitable to sell. The FHA was part of a grand scheme to stimulate the housing sector of the economy during the Great Depression, but also to provide government help and oversight to the home loan industry. Since many of those who qualified for loans were white and not in poverty, the government helped increase residential segregation by encouraging white flight from the cities. Meanwhile, minorities faced still with racist deed restrictions in many new suburbs, found themselves stuck in the city, where the FHA’s mortgage assistance programs were far less helpful.

Some have argued that FHA policies encouraged a series of discriminatory mortgage and insurance practices, known as redlining. During the Depression, the federal government refinanced more than a million mortgages to stem the tide of foreclosures, but not everyone was eligible for this help. Neighborhoods with poor terrain, old buildings, or those threatened by “foreign-born, negro or lower grade population” were judged to be too risky for government help. They appeared on government maps of cities in red. After the war, banks, insurance companies, and other financial institutions also mapped out where not to do business.

Residents in neighborhoods with a “red line” drawn around them would not be able to get loans to buy, repair, or improve housing. Some could not get insurance on what they owned. If they could, the terms of the loan or the insurance rates were higher than those outside the zone; a practice called reverse redlining. It appears that the main criteria for inclusion in a redlined neighborhood were the percentage of minorities. Therefore, most of the people who suffered from the ill-effects of redlining were minorities. African-Americans were harmed most often. Individuals with good credit histories and a middle-class income could find it impossible to buy homes in specific neighborhoods. Redlining was a death sentence to neighborhoods.

In 1968, the Fair Housing Act tried to outlaw redlining (and other forms of housing discrimination), but new laws were needed to bolster the language in the 1970s. However, by that time, long-term damage was evident in inner cities across the United States. Although it is illegal to discriminate against minorities (or anyone really) for non-economic characteristics, there is ample evidence to suggest it still occurs.


Homelessness is another primary concern for citizens of large cities. More than one half- million people are believed to live on the streets or in shelters. In 2013, about one- third of the entire homeless population were living as a member of a family unit. One-fourth of homeless people were children. In Los Angeles County, at the same time, there were somewhere around 40,000 homeless people living either in shelters and on the street. Another 20,000 persons were counted as near homeless or precariously housed, typically living with friends or acquaintances in short-term arrangements.

There are multiple reasons why people become homeless. The Los Angeles Homeless Authority estimates that about one-third of the homeless have substance abuse problems, and another third are mentally ill. Nearly a quarter have a physical disability. A disturbing number are veterans of the armed forces or victims of domestic abuse. Economic conditions locally and nationally also have a significant impact on the overall number of homeless people in a particular year, not only because during recessions, people lose their jobs and homes, but because the stresses of poverty can worsen mental illness.

The government plays a significant role in the pattern and intensity of homelessness. Ronald Reagan is the politician most associated with the homeless crisis both nationally and in California. When Reagan became governor of California in the late 1960s, the deinstitutionalization of people with a mental health condition was already a state policy. Under his administration, state-run facilities for the care of mentally ill persons were closed and replaced by the for-profit board and care homes. The idea was that people should not be locked up by the state solely for being mentally ill and that government-run facilities could not match the quality and cost-efficiency of privately run boarding homes. Many private facilities, though, were severely run, profit-driven, located in poor neighborhoods, and had little professional staff. Patients could, and did, leave these facilities in large numbers, frequently becoming homeless or incarcerated. Other states followed California’s example. By the late 1970s, the federal government passed some legislation to address the growing crisis, but sweeping changes in governmental policy at the federal level during the Regan presidency shelved efforts started by the Carter administration. Drastic cuts to social programs during the 1980s ensured an explosion of mental illness related homelessness. Most funding has never been restored, though the Obama administration has aggressively pursued policies aimed at housing homeless veterans.

Though homeless people come from many types of neighborhoods, facilities for serving homeless populations are not well distributed throughout the urban regions. Many cities have a region known as Skid Row, a neighborhood unofficially reserved for the destitute. The term originated as a reference to Seattle’s lumber yard areas where workers used skids (wooden planks) to help them move logs to mills. Today, many of the shelters and services for the homeless are found in and around skid row.

Food Deserts

A food desert is an area, especially one with low-income residents, that has limited access to affordable and nutritious food. In contrast, an area with supermarkets or vegetable shops is termed a food oasis. The term food desert considers the type and quality of food available to the population, in addition to the number, nature, and size of accessible food stores. Food deserts are characterized by a lack of supermarkets, which decreases residents’ access to fruits, vegetables, and other whole foods.


In 2010, the United States Department of Agriculture reported that 23.5 percent of Americans live in a food desert, meaning that they live more than one mile from a supermarket in urban or suburban areas, and more than 10 miles from a supermarket in rural areas. Food deserts lack whole food providers who supply fresh protein sources along with whole food such as fresh fruits and vegetables, and instead provide processed and sugar- and fat-laden foods in convenience stores.

As noted in the NPR video, a food desert more often occurs in low-income communities, where people do not have access to a vehicle, and must travel over half a mile to reach a grocery store. For those who live in food deserts, access to food can only be found at fast food places or small convenience stores. Those in food deserts seeking healthy food options may have to travel several miles, often by mass transit, to reach grocery stores.

The video by Penn State University, called the Geospatial Revolution, highlights how Philadelphia and Pennsylvania are using geospatial technology such as geographic information systems to help fund and locate supermarkets in underserved communities.

In Mari Gallagher’s Ted Talk, she focuses on “food desert  awareness and solutions,” provides a critical examination of the Supplemental Nutrition Assistance Program (SNAP), and emphasizes the need for improving public health through “Truth in Data for the Common Good.” Mari is the author of Examining the Impact of Food Deserts on Public Health in Chicago, a study that popularized the term “food desert” across the country.

Ron Finley returns to reinforce the importance of community gardens as a way to combat food deserts, or what he calls, food prisons. He talks about how growing gardens empowers your life and local communities. The self-proclaimed Gangsta gardener says, “All of life starts from a garden. Planting your food equates to growing your life, and Ron encourages everyone to create their own opportunities.”

Urban and Suburban Sprawl

Not all of a city’s residents live within the urban cores. Over half of all people live in the suburbs rather than in the city or rural areas. There was a suburban sprawl model developed to explain U.S. development called the peripheral model. This model states that urban areas consist of a CBD followed by sizeable suburban areas of business and residential developments. The outer regions of the suburbs become transition zones of rural areas.

The attraction to suburbs is low crime rates, lack of social and economic problems, detached single-family housing, access to parks, and usually better schooling. These are universal generalizations and not necessarily true everywhere. Suburbs also tend to create economic and social segregation, where tax revenues and social resources provide better funding opportunities than in inner cities.

Of course, there is also a cost to suburban sprawling. Developers are always looking for cheaper land to build, which usually means developing rural areas and farmland rather than expanding next to existing suburbs. Air pollution and traffic congestion also become a problem as working households are required to travel farther to and from work. Suburbs tend to be less commuter-friendly to those who walk or bike because the model of development is based around vehicle transportation.

Water is another challenge to urban growth. It is an elemental part of the fabric of urban lives, providing sustenance and sanitation, commerce, and connectivity. Our fundamental needs for water have always determined the location, size, and form of our cities, just as water shapes the character and outlook of their citizens. Urban health is inextricably linked with water. From the first cities, planners have appreciated the potential linkages of water with health and the need for consistent water supplies. Indeed, the modern field of public health owes a substantial debt to the sanitary engineers who strove to provide potable water and safe disposal of human wastes in burgeoning cities of the Industrial Revolution.

Scientists and decision-makers have recently begun to appreciate that, as in the case of other urban systems, the linkages between water management, health, and sustainability are involved in ways that undermine the effectiveness of traditional approaches. Unprecedented urban populations and densities, urban inequities, and urban mobility pose new problems, and climate change adds a novel and uncharted dimension. This has, in some cases, led to worsening urban health, or increased risks. For instance, some water-associated diseases like dengue are on the rise globally, while others, like cholera, continue to pose serious threats elsewhere. Many regions face increased food and water scarcity, and many urban slums present conditions that challenge effective water management.


Icon for the Creative Commons Attribution 4.0 International License

Introduction to Human Geography Copyright © 2019 by R. Adam Dastrup, MA, GISP is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.

Share This Book