Lecture 13Lecture 13Urbanization & Urban GrowthUrbanization & Urban Growth

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Urbanization & Urban GrowthUrbanization & Urban Growth

Urban area is that area usually having a population of over Urban area is that area usually having a population of over 2,500, but Britain’s smallest city St David’s has a population 2,500, but Britain’s smallest city St David’s has a population of only 1’797of only 1’797

UrbanizationUrbanization——transformation of rural areas into urban areatransformation of rural areas into urban area Urban growthUrban growth——rate of increase of urban populationrate of increase of urban population

CausesCauses1. Natural increase (more births than deaths)1. Natural increase (more births than deaths)2. Immigration, mostly from rural areas2. Immigration, mostly from rural areas Migration is influenced by Migration is influenced by ‘‘push factorpush factor’ (’ (poverty, lack of poverty, lack of

land, declining agricultural jobs, famineland, declining agricultural jobs, famine)) ‘‘pull factorpull factor’ (in search of jobs, housing, health care, better ’ (in search of jobs, housing, health care, better

life, entertainmentlife, entertainment))

Trends important in understanding the problems & Trends important in understanding the problems & challenges of Urban Growthchallenges of Urban Growth

1.The global proportion of urban population rose dramatically1.The global proportion of urban population rose dramatically

from13% (220 million) in 1900, to 29% (732 million) in1950, tofrom13% (220 million) in 1900, to 29% (732 million) in1950, to

49% (3.2 billion) in 200549% (3.2 billion) in 2005

According to UN, currently 25% people live in urban area ofAccording to UN, currently 25% people live in urban area of

Bangladesh, 50% of the urban people live in 4 large citiesBangladesh, 50% of the urban people live in 4 large cities

According to UN projections, According to UN projections, by 2050by 2050 over 6 billion people, two over 6 billion people, two

thirds of the humanity, will be living in towns and cities, with thirds of the humanity, will be living in towns and cities, with 93%93%

of this urban growth occurring in developing countriesof this urban growth occurring in developing countries

2 .The number of large cities mushrooming2 .The number of large cities mushrooming In 1900, only 19 cities had a million or more people and more than In 1900, only 19 cities had a million or more people and more than

95% of humanity lived in rural communities95% of humanity lived in rural communities In 2003 more than 400 cities had a million or more people and In 2003 more than 400 cities had a million or more people and

projected to 564 by 2015projected to 564 by 2015 As they grow and sprawl outward separate urban areas merge to As they grow and sprawl outward separate urban areas merge to

form form megalopolismegalopolis

Trends important in understanding the problems & Trends important in understanding the problems & challenges of Urban Growthchallenges of Urban Growth

33. Urbanization and urban population increasing rapidly in . Urbanization and urban population increasing rapidly in developing countriesdeveloping countries

Currently about 40% of the people in developing Currently about 40% of the people in developing

countries live in urban areascountries live in urban areas

4. Urban growth is slower in developed countries4. Urban growth is slower in developed countries Still developed countries are projected to reach 84% Still developed countries are projected to reach 84%

urbanization by 2025urbanization by 2025 PovertyPoverty is becoming increasingly urbanized as more people is becoming increasingly urbanized as more people

migrate from rural to urban areasmigrate from rural to urban areas According to UN at least According to UN at least 1 billion1 billion people live in crowded people live in crowded

slums of central citiesslums of central cities

Centre of Sao Paulo, one of the largest metropolis in the world

Major Environmental Pros & ConsMajor Environmental Pros & Cons

Most cities are not self-sustaining systems because of their Most cities are not self-sustaining systems because of their high resource input and high waste outputhigh resource input and high waste output

Urban dwellers occupy only Urban dwellers occupy only 2%2% of Earth’s land area but they of Earth’s land area but they consume about consume about 75%75% of Earth’s resources of Earth’s resources

To provide urban dwellers with food, water, energy, minerals, To provide urban dwellers with food, water, energy, minerals, & other resources large areas are & other resources large areas are disturbed disturbed and and degradeddegraded, , hence hence decreases biodiversitydecreases biodiversity

As cities expand they As cities expand they destroy destroy rural croplands, fertile soil, rural croplands, fertile soil, forests, wetlands, and wildlife habitatsforests, wetlands, and wildlife habitats

Major Environmental Pros & ConsMajor Environmental Pros & Cons Water resource problemsWater resource problems Increased demand is met through heavy extraction of groundwater Increased demand is met through heavy extraction of groundwater

depletingdepleting this resource this resource faster than is replenishedfaster than is replenished City pavement increases the chances of local flooding within the City pavement increases the chances of local flooding within the

city by overloading the storm drainscity by overloading the storm drains Increased runoff from the city can increase the chances of Increased runoff from the city can increase the chances of

flooding downstream as wellflooding downstream as well High population densities and high resource consumption in cities High population densities and high resource consumption in cities

produce most of the world’s air pollution, water pollution, solid and produce most of the world’s air pollution, water pollution, solid and hazardous wasteshazardous wastes

Spread of infectiousSpread of infectious diseases & physical injuries causing diseases & physical injuries causing hundreds and thousands of premature deaths each year hundreds and thousands of premature deaths each year

Life in a city is riskierLife in a city is riskier because of pollution and pollution and because of pollution and pollution and pollutant-related diseasespollutant-related diseases

High unemploymentHigh unemployment, , deafening noisedeafening noise, and , and soaring rate ofsoaring rate of crimecrime

Noise pollution

Urban pollution

Urban smog

Noise Pollution

Urban slums, Dhaka CO2 emission

Human wasteSlum, Waste, water pollution

Massive urbanization in Dhaka resulted in tremendous strain on the city’s infrastructure

Major Environmental Pros & ConsMajor Environmental Pros & Cons

Less windyLess windy because tall buildings and other because tall buildings and other structures obstructstructures obstruct the the flow of airflow of air

Keeps polluted area from being diluted and cleansedKeeps polluted area from being diluted and cleansed Enormous amounts of Enormous amounts of heat generatedheat generated by vehicles, factories, by vehicles, factories,

furnaces, lights, air conditioners, and heat absorbing dark furnaces, lights, air conditioners, and heat absorbing dark surfaces, and lack of vegetation in cities surfaces, and lack of vegetation in cities create an urban heat create an urban heat islandisland surrounded by cooler suburban and rural areas surrounded by cooler suburban and rural areas

This effect causes the city to become 1 to 6 This effect causes the city to become 1 to 6 ºº C warmer than C warmer than surrounding landscapessurrounding landscapes

Reduces soil moisture and intensifies COReduces soil moisture and intensifies CO22 emissions emissions Traffic congestion, increased pollution, limited real estate, and Traffic congestion, increased pollution, limited real estate, and

decreasing resources are all possible side effects of urbanizationdecreasing resources are all possible side effects of urbanization Can intensify poverty and social problems which can increase Can intensify poverty and social problems which can increase

civil unrest and undermine governmentcivil unrest and undermine government

City PlanningCity PlanningInIn city planningcity planning environmental factors, city’s site and situation environmental factors, city’s site and situation should be taken into considerationshould be taken into consideration

It is important to combine the physical and aesthetic needs of a It is important to combine the physical and aesthetic needs of a citycity

Although it is impossible to eliminate exposure to pollutants in Although it is impossible to eliminate exposure to pollutants in urban areas it is possible to reduce the exposure by careful urban areas it is possible to reduce the exposure by careful planning, design, and developmentplanning, design, and development

A practical solution to the problems associated with A practical solution to the problems associated with urbanization can be achieved by involving several specialized urbanization can be achieved by involving several specialized professions including urban forestry, landscape architecture, professions including urban forestry, landscape architecture, city planning, and city engineerscity planning, and city engineers

Trees and plants adapted to local climate and soil should be Trees and plants adapted to local climate and soil should be planted to provide shade and beauty, supply wildlife habitats, planted to provide shade and beauty, supply wildlife habitats, reduce pollution, noise, and soil erosionreduce pollution, noise, and soil erosion

Stream and marsh habitats should be maintained or created so Stream and marsh habitats should be maintained or created so that they can become habitats for fish and mammalsthat they can become habitats for fish and mammals

Aesthetic to our urban area

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