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How Fast Are Urban Areas Growing?

Cities have been centers of commerce, communication, technological developments, education, religion, social change political power and progress, as well as centers of crowding, pollution, and disease.

Urban areas have populations of more than 2500 people (some countries it's 10,000-50,000) and a rural area is fewer than 2500 people. Degree of urbanization is the percentage of a population living in an urban area. Urban growth is the rate of increase in urban populations. By 2025;the number of people living in urban areas is projected to reach 5.5 billion, with 90% of this urban growth to occur in developing countries.

Trends in understanding the problems and challenges of urban growth: More than 70% of the global population is expected to occur in urban areas and by 2000 more people will be living in urban areas than rural areas.

The number of large cities is mushrooming. One person out often lives in a city with a million people, and many live in the world's 15 megacities (10 million or more). The urban population of developing countries is growing at 3.5% per year and is projected to reach 57% urbanization by 2025, and large cities already have trouble supplying water, food, housing, jobs and sanitation. Urban growth in developed countries is less than 1%, and should reach 84% urbanization by 2025. Poverty is becoming urbanized as poor people migrate from rural to urban areas. The United Nations estimates that 1 billion people live in (1 )crowded . slums of inner cities or (2) in mostly illegal squatter settlements and .,shantytowns - shacks on undeveloped land, often unsuitable for human habitation.

In Manila, Philippines, 20,000 people live in shacks built in city dumps. In 1984, at Bhopal, India, a toxic gas accident killed 5100 people living in shantytowns near the factory. In Cairo, Egypt, kindergarten age children can be found digging through ox dung, looking for undigested kernels of corn to eat.

Many city governments bulldoze shacks and send police to drive the illegal settlers out, who then develop another shantytown somewhere else. Shanty towns are also found in developed countries, and most inner cities in the United States have concentrations of poor.

Despite squalor and disease, most slum residents are better off than the rural poor. With access to family-planning, they tend to have fewer children, who have better access to schools; a hope for a better future. A few squatter communities have organized to improve their living conditions (Villa El Salvador, Lima, Peru).

What Causes Urban Growth?

Improved conditions in urban areas lower the death rate, and populations tend to grow, in two ways; natural increase (more births than deaths) and by immigration (mostly from rural areas). People are pulled to urban areas in search of jobs and a better life, or pushed from rural areas by poverty, lack of land, famine and war.

Modern, mechanized agriculture uses fewer farm laborers, and allows large landowners to buy out smaller farmers who cannot afford to modernize. The urban poor often have to work long hours for low wages, often in hazardous conditions.

Case Study: Mexico City

About one of every six Mexicans (15.6 million) live in Mexico City, due to immigration. Every day 2000 rural peasant pour into the city, hoping to find a better way of life. Mexico City has severe air pollution, high unemployment, congestion and high crime. More than one-third live in slums (barrios) without water, electricity, or sewers. Human waste is deposited in gutters and the winds pick up dried excrement, fecal snow that falls on the city spreading salmonella and hepatitis. Air pollution from vehicles, factories and stoves is intensified because Mexico City lies in a basin, and thermal inversions trap pollutants at ground level. Plus, engines burn gasoline less efficiently at the high altitudes of the city. Breathing the air is like smoking two packs of cigarettes a day. Many foreign companies give imported workers additional "hazard pay" for working in Mexico City. Mexico City is far from self-sufficient. Most of the nearby forest has been cut, cropland has been converted to urban development, lakes have dried up and water comes from other water-scarce basins. The Mexican government is industrializing other areas in an attempt to slow migration to Mexico City. Cars have been banned from a 50-block central zone. Unleaded gas began being phased in 1991, and since 1993, all new cars must have catalytic converters. The government planted 25 million trees to help clean the air.

How Urbanized Is the United States?

There have been three population shifts in the U.S.: migration to large central cities - 75% live in metropolitan areas(50,000 people.) migrating from large central cities to suburbs and smaller cities - since 1970 migration from the north and east to the south and west - 80% of population increase since 1980.

What Are the Major Urban Problems in the United States?

Since 1920, most people have better working and housing conditions; air and water quality have improved. Death rates have dropped, along with malnutrition and diseases. Concentrating population in small urban areas has also helped protect the degradation of wildlife habitat.

The problems facing the cities today are aging infrastructures (streets, schools, bridges, housing, sewers), lost tax revenues as businesses and affluent people move out, and rising poverty. Violence, drug traffic and abuse have increased in Some areas. Unemployment rates are as high as 50% in Some inner-city areas.

What Are Major Spatial Patterns of Urban Development? Three models of urban structure: concentric-circle city (New York City) - develops outward from its central business district (CBD) in a series of rings as population grows. The CBD and inner-city housing are ringed by housing zones that become more affluent.

sector city (San Francisco to San Jose)- grows in pie-shaped wedges or strips along major transportation routes. multiple-nuclei city (Metropolitan Los Angeles) - develops around a number of independent centers (satellite centers).

Separate urban areas may join to form a megalopolis; Boston and Washington DC (called Bowash). If a city cannot spread out, it must grow vertically - upward and below ground - so it occupies a small area with a high density. People in compact cities walk, ride bicycles or use mass-transit. Heating and cooling costs are reduces in multistory apartment buildings (more energy-efficient).

Urban sprawl is automobile-oriented with low density (cheap gasoline and plentiful land). People live in single-family houses that lose heat rapidly. Urban sprawl also gobbles up natural habitats, farmland and promotes dependency on the automobile.


What Are the Environmental Effects of Urban Areas?

Urban environmental problems can be grouped into two categories (both are often found within the same city): those associated with poverty those associated with economic growth or affluence: increases resource use per person

Most cities are not close to being self-sustaining (import food, water, energy, minerals), and they produce wastes that pollute air, water and land. But, they also have some benefits: recycling is more feasible (large concentrations of recycle material) population growth is reduced education and mobilization regarding environmental issues helps preserve biodiversity (reduces stress on wildlife habitats), but large areas must be disturbed to provide resources (also become polluted)

The 43% of the world's urban dwellers occupy only 5% of the earth's land area. The harmful environmental impacts varies from city to city, depending on a city's size and wealth. Wealthy cities are major contributors to global problems, while poor cities can have severe local impacts.

To reach a sustainable relationship between cities and the living world, cities with a high-waste, linear metabolism (increasing resources and wastes) need to convert to low-waste, sustainable cities with a circular metabolism.

Why Are Trees and Food Production Important in Cities?

"Most cities are places where they cut down the trees and then mane the streets after them." According to the American Forestry Association, one tree provides over $57,000 worth of air conditioning, erosion and stormwater control, wildlife shelter, and air pollution control over 50 years (plus aesthetic pleasure). Most cities produce little of their own food, but individuals can plant community gardens, use window boxes or gardens on roofs of apartments. Farmers' markets allow farmers to sell directly to consumers.

What Are the Water Supply Problems of Cities?

Most cities have water supply and flooding problems: to meet demand expensive reservoirs and canals must be build transfer of water from rural areas deprives wild areas of surface water and can deplete groundwater concrete and asphalt causes run-off (overloads sewers and causes flooding) many cities are built on floodplains (flat, accessible, near rivers) coastal cities could be flooded if sea level rises

What Are the Pollution Problems of Cities?

Urban residents are generally subjected to higher concentrations of pollutants: litter and garbage accumulate in slums (spread of disease) 1.1 billion live in areas where air pollution exceeds healthful levels two-thirds of residents in developing countries do not have adequate sanitation facilities (water purification and wastewater treatment) and 90% of all sewage is discharged directly into rivers, lakes and coastal waters 220 million do not have safe drinking water (buy from expensive vendors)

Urbanization also alters the local climate. Cities create an urban heat island (warmer, rainier, foggier and cloudier than suburbs) due to heat generated by cars, factories, furnaces and concrete. A dust dome above urban areas traps tiny solid particles (pollutants), and if winds increase it forma a dust plume, spreading pollutants.

Heat islands can merge as urban areas grow and merge, which affects climate and keeps polluted air from being diluted. Cities can counteract the heat-island effect by tree-planting, lighter (more reflective) paints, adding sand to asphalt (more reflective), and energy-efficient standards for cars, buildings and appliances.

How Serious is Urban Noise Pollution ?

Nearly half of all Americans are regularly exposed to noise pollution -unwanted , disturbing, or harmful sound that impairs or interferes with hearing, causes stress, hampers works efficiency, or causes accidents. Noise is the most widespread occupational hazard.

Prolonged exposure to excessive noise can cause permanent hearing loss, high blood pressure, muscle tension, migraine headaches, higher cholesterol levels, ulcers, irritability, insomnia and psychological disorders, including increased aggression

Sound pressure is harmful at 75 dbA, painful at 120 dbA and can kill at 180 dbA (logarithmic scale). Levels are harmful if you have to raise your voice to be heard, a noise causes your ears to ring, or speech seems muffled.. There are 5 ways to control noise. moderate activities and devices to produce less noise shield noisy devices shield workers from the noise move noisy things away from people use antinoise - technology that cancels out one noise with another

How Does Urban Life Affect Human Health?

Some benefits or urban life include better access to education, social services, and medical care. But, high-density city life can increase the spread of infectious diseases, physical injuries (industrial and traffic accidents) and health problems caused from exposure to pollution and noise. In developing countries many people lack safe drinking water and or sanitation, and therefore live and work in life-threatening environments.

How Does Urban Growth Affect Nearby Rural Areas and Small Towns?

Each year, about 526,000 hectares of rural land is converted to urban development, rights-of-way, highways and airports. This agricultural or forestland is lost for food production. More energy is needed to transport food, which causes more pollution. Urban growth destroys wetlands in coastal areas. As land becomes more valuable, increased taxes force many farmers to sell their land, often to developers. Suburbs must raise taxes to meet the demands for new public services and long-rime residents may be forced out. Old and new residents may eventually face the inner-city problems they sought to avoid (harmful positive feedback).