Urbanization

Global urbanization map showing the percentage of urbanization and the biggest global population centres per country in 2018, based on UN estimates.

Guangzhou, a city of 14.5 million people, is one of the 8 adjacent metropolises located in the largest single agglomeration on earth, ringing the Pearl River Delta of China.

Mumbai is the most populous city in India, and the eighth most populous city in the world, with a total metropolitan area population of approximately 18.5 million.

Moscow, the capital and largest city of Russia, is the largest metropolitan area in Europe; with over 20 million residents in its metropolitan area.

Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly the process by which towns and cities are formed and become larger as more people begin living and working in central areas.

Although the 2 concepts are sometimes used interchangeably, urbanization should be distinguished from urban growth. Urbanization refers to the proportion of the total national population living in areas classified as urban, whereas urban growth strictly refers to the absolute number of people living in those areas. It is predicted that by 2050 about 64% of the developing world and 86% of the developed world will be urbanized. That is equivalent to approximately 3 billion urbanites by 2050, much of which will occur in Africa and Asia. Notably, the United Nations has also recently projected that nearly all global population growth from 2017 to 2030 will be by cities, with about 1.1 billion new urbanites over the next 10 years.

Urbanization is relevant to a range of disciplines, including urban planning, geography, sociology, architecture, economics, education, statistics and public health. The phenomenon has been closely linked to modernization, industrialization, and the sociological process of rationalization. Urbanization can be seen as a specific condition at a set time (e.g. the proportion of total population or area in cities or towns), or as an increase in that condition over time. Therefore, urbanization can be quantified either in terms of the level of urban development relative to the overall population, or as the rate at which the urban proportion of the population is increasing. Urbanization creates enormous social, economic and environmental changes, which provide an opportunity for sustainability with the "potential to use resources more efficiently, to create more sustainable land use and to protect the biodiversity of natural ecosystems." Developing urban resilience and urban sustainability in the face of increased urbanization is at the center of international policy in Sustainable Development Goal 11 "Sustainable cities and communities."

Urbanization is not merely a modern phenomenon, but a rapid and historic transformation of human social roots on a global scale, whereby predominantly rural culture is being rapidly replaced by predominantly urban culture. The first major change in settlement patterns was the accumulation of hunter-gatherers into villages many thousand years ago. Village culture is characterized by common bloodlines, intimate relationships, and communal behaviour, whereas urban culture is characterized by distant bloodlines, unfamiliar relations, and competitive behaviour. This unprecedented movement of people is forecast to continue and intensify during the next few decades, mushrooming cities to sizes unthinkable only a century ago. As a result, the world urban population growth curve has up till recently followed a quadratic-hyperbolic pattern.

History

Urbanization over the past 500 years

A global map illustrating the first onset and spread of urban centers around the world, based on.

From the development of the earliest cities in Indus valley civilization, Mesopotamia and Egypt until the 18th century, an equilibrium existed between the vast majority of the population who were engaged in subsistence agriculture in a rural context, and small centres of populations in the towns where economic activity consisted primarily of trade at markets and manufactures on a small scale. Due to the primitive and relatively stagnant state of agriculture throughout this period, the ratio of rural to urban population remained at a fixed equilibrium. However, a significant increase in the percentage of the global urban population can be traced in the 1st millennium BCE. Another significant increase can be traced to Mughal India, where 15% of its population lived in urban centers during the 16th–17th centuries, higher than in Europe at the time. In comparison, the percentage of the European population living in cities was 8–13% in 1800. Urbanization of the human population accelerated rapidly beginning in the middle of the eighteenth century.

With the onset of the British agricultural and industrial revolution in the late 18th century, this relationship was finally broken and an unprecedented growth in urban population took place over the course of the 19th century, both through continued migration from the countryside and due to the tremendous demographic expansion that occurred at that time. In England and Wales, the proportion of the population living in cities with more than 20,000 people jumped from 17% in 1801 to 54% in 1891. Moreover, and adopting a broader definition of urbanization, while the urbanized population in England and Wales represented 72% of the total in 1891, for other countries the figure was 37% in France, 41% in Prussia and 28% in the United States.

As labourers were freed up from working the land due to higher agricultural productivity they converged on the new industrial cities like Manchester and Birmingham which were experiencing a boom in commerce, trade, and industry. Growing trade around the world also allowed cereals to be imported from North America and refrigerated meat from Australasia and South America. Spatially, cities also expanded due to the development of public transport systems, which facilitated commutes of longer distances to the city centre for the working class.

Urbanization rapidly spread across the Western world and, since the 1950s, it has begun to take hold in the developing world as well. At the turn of the 20th century, just 15% of the world population lived in cities. According to the UN, the year 2007 witnessed the turning point when more than 50% of the world population were living in cities, for the first time in human history.

Yale University in June 2016 published urbanization data from the time period 3700 BC to 2000 AD, the data was used to make a video showing the development of cities on the world during the time period. The origins and spread of urban centers around the world were also mapped by archaeologists.

Causes

Population age comparises between rural Pocahontas County, Iowa and urban Johnson County, Iowa, illustrating the flight of young adults (red) to urban centres in Iowa.

The City of Chicago, Illinois is an example of the early American grid system of development. The grid is enforced even on uneven topography.

Urbanization occurs either organically or planned as a result of individual, collective and state action. Living in a city can be culturally and economically beneficial since it can provide greater opportunities for access to the labour market, better education, housing, and safety conditions, and reduce the time and expense of commuting and transportation. Conditions like density, proximity, diversity, and marketplace competition are elements of an urban environment that deemed beneficial. However, there are also harmful social phenomena that arise: alienation, stress, increased cost of living, and mass marginalization that are connected to an urban way of living. Suburbanization, which is happening in the cities of the largest developing countries, may be regarded as an attempt to balance these harmful aspects of urban life while still allowing access to the large extent of shared resources.

In cities, money, services, wealth and opportunities are centralized. Many rural inhabitants come to the city to seek their fortune and alter their social position. Businesses, which provide jobs and exchange capital, are more concentrated in urban areas. Whether the source is trade or tourism, it is also through the ports or banking systems, commonly located in cities, that foreign money flows into a country.

Many people move into cities for economic opportunities, but this does not fully explain the very high recent urbanization rates in places like China and India. Rural flight is a contributing factor to urbanization. In rural areas, often on small family farms or collective farms in villages, it has historically been difficult to access manufactured goods, though the relative overall quality of life is very subjective, and may certainly surpass that of the city. Farm living has always been susceptible to unpredictable environmental conditions, and in times of drought, flood or pestilence, survival may become extremely problematic.

Thai farmers are seen as poor, stupid, and unhealthy. As young people flee the farms, the values and knowledge of rice farming and the countryside are fading, including the tradition of long kek, helping neighbours plant, harvest, or build a house. We are losing what we call Thai-ness, the values of being kind, helping each other, having mercy and gratefulness – Iam Thongdee, Professor of Humanities, Mahidol University in Bangkok

In a New York Times article concerning the acute migration away from farming in Thailand, life as a farmer was described as "hot and exhausting". "Everyone says the farmer works the hardest but gets the least amount of money". In an effort to counter this impression, the Agriculture Department of Thailand is seeking to promote the impression that farming is "honorable and secure".

However, in Thailand, urbanization has also resulted in massive increases in problems such as obesity. Shifting from a rural environment to an urbanized community also caused a transition to a diet that was mainly carbohydrate-based to a diet higher in fat and sugar, consequently causing a rise in obesity. City life, especially in modern urban slums of the developing world, is certainly hardly immune to pestilence or climatic disturbances such as floods, yet continues to strongly attract migrants. Examples of this were the 2011 Thailand floods and 2007 Jakarta flood. Urban areas are also far more prone to violence, drugs, and other urban social problems. In the United States, industrialization of agriculture has negatively affected the economy of small and middle-sized farms and strongly reduced the size of the rural labour market.

These are the costs of participating in the urban economy. Your increased income is canceled out by increased expenditure. In the end, you have even less left for food. – Madhura Swaminathan, economist at Kolkata’s Indian Statistical Institute

Particularly in the developing world, conflict over land rights due to the effects of globalization has led to less politically powerful groups, such as farmers, losing or forfeiting their land, resulting in obligatory migration into cities. In China, where land acquisition measures are forceful, there has been far more extensive and rapid urbanization (54%) than in India (36%), where peasants form militant groups (e.g. Naxalites) to oppose such efforts. Obligatory and unplanned migration often results in the rapid growth of slums. This is also similar to areas of violent conflict, where people are driven off their land due to violence.

Cities offer a larger variety of services, including specialist services not found in rural areas. These services require workers, resulting in more numerous and varied job opportunities. Elderly people may be forced to move to cities where there are doctors and hospitals that can cater to their health needs. Varied and high-quality educational opportunities are another factor in urban migration, as well as the opportunity to join, develop, and seek out social communities.

Urbanization also creates opportunities for women that are not available in rural areas. This creates a gender-related transformation where women are engaged in paid employment and have access to education. This may cause fertility to decline. However, women are sometimes still at a disadvantage due to their unequal position in the labour market, their inability to secure assets independently from male relatives and exposure to violence.

People in cities are more productive than in rural areas. An important question is whether this is due to agglomeration effects or whether cities simply attract those who are more productive. Urban geographers have shown that there exists a large productivity gain due to locating in dense agglomerations. It is thus possible that agents locate in cities in order to benefit from these agglomeration effects.

Dominant conurbation

See also: List of largest cities throughout history and Primate city

The dominant conurbation(s) of a country can benefit to a greater extent from the same things cities offer, making them magnets for not just the non-urban population, but also urban and suburban population from other cities. Dominant conurbations are quite often primate cities, but do not have to be. For instance Greater Manila is rather a conurbation than a city: its 20 million overall population (over 20% national population) make it very much a primate city, but Quezon City (2.7 million), the largest municipality in Greater Manila, and Manila (1.6 million), the capital, are not. A conurbation's dominance can be measured by output, wealth, and especially population, each expressed as a percentage of an entire country. Greater Seoul is one conurbation with massive dominance over South Korea, it is home to 50% of the entire national population.

Though Greater Busan-Ulsan (15%, 8 million) and Greater Osaka (14%, 18 million) exhibit strong dominance in their respective countries, they are losing population to their even more dominant rivals, Seoul and Tokyo respectively.

Economic effects

A crowded BTS Station during the rush hour in Bangkok, Thailand

As cities develop, effects can include a dramatic increase and change in costs, often pricing the local working class out of the market, including such functionaries as employees of the local municipalities. For example, Eric Hobsbawm's book The age of revolution: 1789–1848 (published 1962 and 2005) chapter 11, stated "Urban development in our period was a gigantic process of class segregation, which pushed the new labouring poor into great morasses of misery outside the centres of government, business, and the newly specialized residential areas of the bourgeoisie. The almost universal European division into a 'good' west end and a 'poor' east end of large cities developed in this period." This is likely due to the prevailing south-west wind which carries coal smoke and other airborne pollutants downwind, making the western edges of towns preferable to the eastern ones.

Similar problems now affect the developing world, rising inequality resulting from rapid urbanization trends. The drive for rapid urban growth and often efficiency can lead to less equitable urban development. Think tanks such as the Overseas Development Institute have proposed policies that encourage labour-intensive growth as a means of absorbing the influx of low-skilled and unskilled labour. One problem these migrant workers are involved with is the growth of slums. In many cases, the rural-urban low skilled or unskilled migrant workers, attracted by economic opportunities in urban areas, cannot find a job and afford housing in cities and have to dwell in slums.

Urban problems, along with infrastructure developments, are also fuelling suburbanization trends in developing nations, though the trend for core cities in said nations tends to continue to become ever denser. Urbanization is often viewed as a negative trend, but there are positives in the reduction of expenses in commuting and transportation while improving opportunities for jobs, education, housing, and transportation. Living in cities permits individuals and families to take advantage of the opportunities of proximity and diversity. While cities have a greater variety of markets and goods than rural areas, infrastructure congestion, monopolization, high overhead costs, and the inconvenience of cross-town trips frequently combine to make marketplace competition harsher in cities than in rural areas.

In many developing countries where economies are growing, the growth is often erratic and based on a small number of industries. For young people in these countries, barriers exist such as lack of access to financial services and business advisory services, difficulty in obtaining credit to start a business, and lack of entrepreneurial skills, in order for them to access opportunities in these industries. Investment in human capital so that young people have access to quality education and infrastructure to enable access to educational facilities is imperative to overcoming economic barriers.

Environmental effects

Urbanization may improve environmental quality as a result of numerous reasons. For instance, urbanization upsurges income levels which instigates the eco-friendly services sector and increases demand for green and environmentally compliant products. Furthermore, urbanization improves environmental eminence through superior facilities and better-quality living standards in urban areas as compared to rural areas. Lastly, urbanization curbs pollution emissions by increasing R&D and innovations. In his book Whole Earth Discipline, Stewart Brand argues that the effects of urbanization are primarily positive for the environment. First, the birth rate of new urban dwellers falls immediately to replacement rate and keeps falling, reducing environmental stresses caused by population growth. Secondly, emigration from rural areas reduces destructive subsistence farming techniques, such as improperly implemented slash and burn agriculture. Alex Steffen also speaks of the environmental benefits of increasing the urbanization level in "Carbon Zero: Imagining Cities that can save the planet", .

However, existing infrastructure and city planning practices are not sustainable. In July 2013 a report issued by the United Nations Department of Economic and Social Affairs warned that with 2.4 billion more people by 2050, the amount of food produced will have to increase by 70%, straining food resources, especially in countries already facing food insecurity due to changing environmental conditions. The mix of changing environmental conditions and the growing population of urban regions, according to UN experts, will strain basic sanitation systems and health care, and potentially cause a humanitarian and environmental disaster.

Urban heat island

The existence of urban heat islands has become a growing concern over the years. An urban heat island is formed when industrial and urban areas produce and retain heat. Much of the solar energy that reaches rural areas is consumed by evaporation of water from vegetation and soil. In cities, where there are less vegetation and exposed soil, most of the sun's energy is instead absorbed by buildings and asphalt; leading to higher surface temperatures. Vehicles, factories, and industrial and domestic heating and cooling units release even more heat. As a result, cities are often 1 to 3 °C (1.8 to 5.4 °F) warmer than surrounding landscapes. Impacts also include reducing soil moisture and a reduction in reabsorption of carbon dioxide emissions.

Water quality

The occurrence of eutrophication in bodies of water is another effect large urban populations have on the environment. When rain occurs in these large cities, the rain filters down the pollutants such as CO₂ and other greenhouse gases in the air onto the ground below. Then, those chemicals are washed directly into rivers, streams, and oceans, causing a decline in water quality and damaging marine ecosystems.

Eutrophication is a process which causes hypoxic water conditions and algal blooms that may be detrimental to the survival of aquatic life. Harmful algal blooms, which produce dangerous toxins, thrive in eutrophic environments that are also rich in nitrogen and phosphorus. In these ideal conditions, they overtake surface water, making it difficult for other organisms to receive sunlight and nutrients. Overgrowth of algal blooms causes a decrease in overall water quality and disrupts the natural balance of aquatic ecosystems. Furthermore, as algal blooms die, CO₂ is produced, causing a more acidic environment, a process known as acidification.

The ocean's surface also has the ability to absorb CO₂ from the earth's atmosphere as emissions increase with the rise in urbanization. In fact, it is reported that the ocean absorbs a quarter of the CO₂ produced by humans. This has been useful to the environment by decreasing the harmful effects of greenhouse gases, but also further perpetuates acidification. Changes in pH inhibit the proper formation of calcium carbonate, a crucial component for many marine organisms to maintain shells or skeletons. This is especially true for many species of molluscs and coral. Regardless, some species have been able to instead adapt or thrive in a more acidic environment

Food waste

Rapid growth of communities create new challenges in the developed world and one such challenge is an increase in food waste also known as urban food waste. Food waste is the disposal of food products that can no longer be used due to unused products, expiration, or spoilage. The increase of food waste can raise environmental concerns such as increase production of methane gases and attraction of disease vectors. Landfills are the third leading cause of the release of methane, causing a concern on its impact to our ozone and on the health of individuals. Accumulation of food waste causes increased fermentation, which increases the risk of rodent and bug migration. An increase in migration of disease vectors creates greater potential of disease spreading to humans.

Waste management systems vary on all scales from global to local and can also be influenced by lifestyle. Waste management was not a primary concern until after the Industrial Revolution. As urban areas continued to grow along with the human population, proper management of solid waste became an apparent concern. To address these concerns, local governments sought solutions with the lowest economic impacts which meant implementing technical solutions at the very last stage of the process. Current waste management reflects these economically motivated solutions, such as incineration or unregulated landfills. Yet, a growing increase for addressing other areas of life cycle consumption has occurred from initial stage reduction to heat recovery and recycling of materials. For example, concerns for mass consumption and fast fashion have moved to the forefront of the urban consumers’ priorities. Aside from environmental concerns (ex. climate change effects), other urban concerns for waste management are public health and land access.

Habitat fragmentation

Urbanization can have a large effect on biodiversity by causing a division of habitats and thereby alienation of species, a process known as habitat fragmentation. Habitat fragmentation does not destroy the habitat, as seen in habitat loss, but rather breaks it apart with things like roads and railways This change may affect a species ability to sustain life by separating it from the environment in which it is able to easily access food, and find areas that they may hide from predation With proper planning and management, fragmentation can be avoided by adding corridors that aid in the connection of areas and allow for easier movement around urbanized regions.

Depending on the various factors, such as level of urbanization, both increases or decreases in "species richness" can be seen. This means that urbanization may be detrimental to one species but also help facilitate the growth of others. In instances of housing and building development, many times vegetation is completely removed immediately in order to make it easier and less expensive for construction to occur, thereby obliterating any native species in that area. Habitat fragmentation can filter species with limited dispersal capacity. For example, aquatic insects are found to have lower species richness in urban landscapes. The more urbanized the surrounding of habitat is, the fewer species can reach the habitat. Other times, such as with birds, urbanization may allow for an increase in richness when organisms are able to adapt to the new environment. This can be seen in species that may find food while scavenging developed areas or vegetation that has been added after urbanization has occurred i.e. planted trees in city areas