urbanization and sustainable cities miller (2003): chapter 11
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Urbanization
An urban (or metropolitan) area = a town or a city plus its adjacent suburbs with a population of >2,500 people
A rural area = an area with < 2,500 people
A country’s degree of urbanization = percentage of its population living in an urban area
Virtually all the population growth expected during the next 30 years will be concentrated in urban areas
What Is Urban?
Definition of “urban” varies widely from country to country. Some countries distinguish between rural and urban based on:
Size or density of localities Administrative considerations (only major cities are
classed as urban) The percentage of persons not dependent on
agriculture Some nations define all of their population as living in
urban areas (e.g. Singapore). Some nations define none of their population as urban (e.g. Polynesia (South Pacific Islands))
Urban Growth
Urban areas grow in 2 ways:1. Natural increase of its population (births)
2. Immigration (mostly from rural areas – the biggest cause of urban growth)
Proportion of the global population living in urban areas: 2% (pre-industrial period) 46% (2001) (~160,000 people added to world’s urban areas each day)
UN projections: by 2050, ~63% of world’s people will be living in urban areas, with 90% of this urban growth in developing countries
Number of large cities (>1 million people): increasing rapidly throughout the 20th century
Urban growth is much slower in developed countries than in developing countries (still, projection: 79% (current) 84% (2025) in developed countries)
Megacities
1900: 19 cities had >1 million people (95% of the population then were rural)
2001: more than 400 cities have >1 million people
Increasingly, there are more megacities (cities with populations >10 million people)
1985: 8 megacities 2001: 16 (13 of them in developing countries) As they grow and sprawl outward, separate urban areas
may merge to form a megalopolis (= a very large city, or a region made up of several large cities and their surrounding areas in sufficient closeness to be considered a single urban complex)
Tokyo – world’s largest megacity
Japan: one of the most highly urbanized countries in the world
Nearly 80% of Japan's 125 million people: live in cities throughout the country
The three largest urban centres in Japan: Tokyo, Osaka and Nagoya metropolitan areas
Tokyo: by far the largest metropolitan area with >25% of the total population living in its centre and surrounding areas
Urban Poverty
Poverty is becoming increasingly urbanized as more poor people migrate from rural to urban areas.
U.N. estimates ~ 1 billion people live in slums (heavily populated urban areas characterized by substandard housing) of inner cities, or in vast illegal squatter settlements (squatter = person who takes unauthorized possession of unoccupied premises) and shantytowns (slum areas of a town or outskirts of a town, consisting of huts or shanties)
Often the land in squatter settlements is not suitable for human habitation because of:
air and water pollution hazardous wastes from nearby factories the land is prone to natural disasters (earthquakes,
volcanoes, flooding)
Diseases are common and frequent in squatter settlements and shanty towns
Many cities do not provide adequate services (drinking water, sanitation facilities, electricity, food, heath care, housing, schools, jobs) to squatter settlements (lack money, and fear even more rural poor moving in)
Many city governments try to destroy squatter settlements or send police to drive illegal settlers out (people then move back in or develop another shantytown somewhere else)
Case Study: Mexico City
Population: ~18 million people (the world’s second most populous city, ~1/5 Mexicans live in Mexico City) >2000 people move into the city from poor rural areas every day
Mexico City suffers from severe air pollution:
Some 4 million motor vehicles and 30,000 factories pour pollutants into the atmosphere The city lies in a natural basin surrounded by mountains, frequent thermal inversions trap polluted air at ground level
Living in Mexico City and breathing the air
= smoking 3 packs of cigarettes a day!
Government has tried to improve this (e.g. having buses and trucks running on LPG, enforcing stricter industrial emission standards, planting trees), still, fail to meet minimum air quality standards on average 300 days a year
Mexico City, with the volcano Popocatépetl in the background
Mexico City – Urban Problems
Mexico City also suffers from:
Very high unemployment (~50%)
A soaring crime rate (robbery, assault, murder)
Severe noise pollution
Bad traffic congestion
Inadequate housing (>1/3 of the people living in slums with no running water or electricity)
Inadequate sanitation ( widespread infectious diseases such as hepatitis)
Environmental Problems
Urban areas are not self sustaining!
Survive only by importing food, water, energy, minerals, and other resources from somewhere else
Produce vast quantities of wastes Affect the health of their inhabitants
but also the environmental health of rural areas
and the health of the planet
Often, agriculture and cities develop in similar areas
expanding urban areas = using up agricultural land
Water625,000 tonnes
Fuel9,500
tonnes
Food2,000
tonnes
Daily Inputs
U.S. city of 1
million people
Daily Outputs
Air pollutants950 tonnes
Rubbish9,500
tonnes
Sewage500,000tonnes
Environmental Problems Of Cities
Most cities: have few trees and other plants
Most cities: produce little of their own food
Many cities: have water supply and flooding problems
Many coastal areas: popular for urban development
Many natural coastal habitats have been cleared, drained, and filled in for urban development
Urban Microclimate
Materials used in urban construction: conduct more heat than vegetated areas
Buildings and vehicles: release significant amounts of heat energy from burning of fossil fuels
Urbanization can therefore its own microclimate
Temperature of a city: several degrees warmer than surrounding rural areas
Cities are urban heat islands
Urban Pollution
Urban residents suffer higher pollution levels than surrounding rural areas.
Sheer numbers of people in cities mean urban areas are major contributors to air pollution and enhanced greenhouse effect.
Most urban residents suffer from excessive noise.
0 15085
Normal breathing
Quiet ruralarea
Vacuumcleaner
Permanentdamage begins
after 8-hrs
Rockconcert
Noise levels in decibels (dbA)
Militaryrifle
Environmental Benefits
Recycling is more feasible economically - large concentration of materials.
Environmental pressures from population growth are reduced - because birth rates are usually much less in urban
areas. Spending per person on environmental protection is
higher in urban areas.
But, concentrating people in urban areas may not help preserve biodiversity or restrict habitat loss because of all the land needed to support urban residents.
Transportation and Urbanization
Motor vehicles provide convenient transport and mobility
Much of the world’s economy built on producing automobiles and supplying roads and services for them
Transport causes many deaths and accidents per year
Also biggest source of air pollution (15% of CO2 emissions), producing smog
Worldwide, 1/3 of urban land is devoted to roads, car parks, gas stations.
Urban Transport
Dispersed car-centred cities use 10 times more energy per person for transport than more compact cities with mass-transit transport systems
In North American, Australia and some European cities - have dispersed, car-centred cities with low population density
The outskirts of the urban areas, or suburbs, spread out to cover large amounts of former ‘green spaces’, this is urban sprawl
Sustainable Cities
Sustainable city: takes only the resources that are needed, can be continuously recycled, or returned to the environment in the least harmful way
In reality, no city is completely sustainable.
Curibita: located in S. Brazil, population 1.6 million One of the fastest growing cities in Brazil, but has
managed to expand while maintaining a good quality of urban life
Has consistent planning and innovative urban solutions – high praise and environmental awards as an ecocity (or ‘green city’)
The Greening of Curibita
From 1974: large tree planting scheme. Now has high ratio of green area per inhabitant (52 m2), with large parks and recreational areas.
Low air pollution: Curibita is not built around the car but is people-oriented.
Integrated land-use and transportation system Flooding problems solved by diverting water to lakes in
the parks
Strict water pollution control laws
In 1989: a “garbage that is not garbage” campaign, in which city residents recycle one-third of all solid waste.