A future of sprawling unending cities is already a bleak reality in other parts of the world. In Latin America, Mexico City (Mexico) has encroached upon two different states, while Buenos Aires (Argentina) covers 30 different municipalities.
A major feature of North American cities is urban sprawl, which has been attributed to permissive land-use planning and the growth of affluent households. By 2000, sprawl was increasing at twice the rate of urban population growth in the United States, with Las Vegas being the fastest growing metro area. Canada currently has three of the world's 10 urban areas with the most extensive sprawl. They are Calgary, Vancouver and Toronto.
Fifty-two per cent of the world's 3.3 billion urban population live in cities and towns of fewer than 500,000 people. In developed and developing countries 54 per cent and 51 per cent of urbanites, respectively, live in such cities.
However, as city populations grow, so cities expand by consuming most of the previously separated towns and cities. In some cases this results in turning such areas into metropolises, and others into peri urban entities. Either way, the process of urban sprawl is presenting a major challenge for urban planners and urban management worldwide.
Urban sprawl is one of the challenges facing urban planners and local authorities according to the new UN-HABITAT report Planning Sustainable Cities: Global Report on Human Settlements 2009. The report argues that increasing socio-spatial challenges, especially social and spatial inequalities, urban sprawl and unplanned peri-urbanization are some of the key challenges facing the 21st century city.
"There are a number of key messages emerging from the Global Report, all of them contributing towards finding a new role for urban planning in sustainable urban development," says Anna Tibaijuka, executive director of UN-HABITAT.
"One important message is that governments should increasingly take on a more central role in cities and towns in order to lead development initiatives and ensure that basic needs are met. It is clear that urban planning has an important role to play in assisting governments to meet the challenges of the urban century."
Asia is home to the most megacities in the world. A major trend is that urbanization is pushing past metropolitan borders, leading to the formation of enormously extended mega-urban regions (such as Shanghai and Beijing in China) that have developed along infrastructure corridors, then radiating over long distances from core cities.
This has created complex planning and governance problems within the region. In Asia, urbanization is taking ruralopolitan urban forms, an entirely new phenomenon. This is occurring in Bangladesh, China, India, Indonesia and Pakistan where vast stretches of rural lands are being engulfed by expanding cities. Sprawl of this kind, then, explains the unique mixture of rural and urban land use in this region.
Urban sprawl in Sub-Saharan Africa is not as drastic but it is occurring. Many cities are spreading out and engulfing surrounding rural land and adjacent towns, leading to continuous belts of settlements. This process is largely informal and is driven by the efforts of low-income households to secure affordable land at reasonable locations.
Another facet of sprawl characteristic of the region is the growth, primarily, in the capital city.
One consequence of this merging of previously non-adjoining towns and cities around the world is metropolitanization. The process refers to the conversion of rural land into urban uses and the engulfment of adjacent municipalities by larger cities to constitute new metro areas.
Developed countries present a contrasting picture of urban sprawl. A common feature of developed countries is that urban densities have been declining, and this has been contributing to urban sprawl. Between 1960 and 1990, Amsterdam (the Netherlands) experienced a 10 per cent reduction in its population density, but expanded its land area by more than 60 per cent.
One factor that accounts for urban sprawl in these countries is economic prosperity. The problem has been more acute in North America, where a significant segment of the population owns cars. Another reason for sprawl is that population growth has intensified the density of some inner-city areas, prompting the wealthy to relocate to suburbs. Consequently, in Western Europe, sprawl is acute in Belgium; the Netherlands; eastern, southern and western Germany; northern Italy; the Paris and Madrid regions; Ireland; and Portugal.
A major determinant of sprawl is government policy, which has been more tolerant in North America, but more stringent in Western Europe. Development of core areas of many Western European and Japanese cities before the era of the automobile explains their relative compactness, compared to Australia, New Zealand, Canada and the United States. However, the need in European cities today to commute is evidence of sprawl of the North American kind.
Oceania and Japan: Sprawl is a major environment concern. Throughout this region, sprawl has become a major planning concern, as traffic congestion and pollution have worsened. In New Zealand, cities are expanding and blurring urban-rural boundaries, as peri-urban populations grow.
This complicates municipal governance. In Australia, annexation and consolidation are resulting in the "disappearing towns syndrome". There, Hursbridge, Bellowie, Adinga Beach and Golden Bay-singleton disappeared and became parts of Melbourne, Brisbane, Adelaide and Mandurah, respectively.
Transitional Countries: During the communist era, centralized decision-making structure permitted the state to establish compact, highly dense cities with functional public transport. However, since the political and economic reforms of the 1990s, which presided over the whittling away of communism in these areas, low-income families and lower-level retail business has moved form inner city to low-cost neighbourhoods on the urban fringes. Here also, sprawl has been encouraged as private developers erect exclusive and high-income suburban enclaves.
The report concludes by calling on urban planners to encourage more compact cities in a bid to reduce green house gases and emissions. UN-HABITAT report Planning Sustainable Cities: Global Report on Human Settlements 2009