Geog. 309: Urban Environmental Pollution Lecture 1- The Urban Ecosystem “Cities are nodes of man’s greatest impact on nature, the places where he has most altered the essential resources of land, air, organisms, and water.” - Marcus and Detwyler, Urbanization and Environment

The Urban Ecosystem

The city consists of two components: urban man and urban environment Ecosystem: the organisms of a locality together with their related environment, considered as a unit. The urban ecosystem is also subject to the principle of environmental unity: all the elements and processes of environment are interrelated and interdependent, and that a change in one will lead to changes in the others.

Three self-evident interactions in an urban ecosystem (1) urbanization involves a modification of the environment; (2) physical environment may influence the form, functions, and growth of the city; and (3) continuous feedback occurs in the city between man, cultural, and physical environments.

The city is an open system: not self-contained; it cannot operate independently and in isolation from other parts of the world. positive and negative feedback: Positive feedback : is vicious circle or deviation amplification; changes occur in the same direction at a compounding rate. Example: Population-modernization-migration-population Negative feedback: equilibrating; dampen fluctuations in the system and maintain a stead state. Example: Population-air pollution-discomfort and disease- mortality

Urban environment is divided into two classes: 1.cultural (formed by man; it comprises the external cultural attributes of a given community); and 2.physical subsystem (nature’s elements; exist whether or not man is one on the scene The role of environment in the urban ecosystem can be shown by a schematic representation of feedback loops resulting from interaction of the environmental and cultural subsystem (a) Population-modernization-migration-population (increase) (b) Population-air pollution-discomfort and disease-copulation-population (decrease)

The requirements of urban man: Biological and cultural requirements: -Air, water, space, energy (food and heat), shelter, waster disposal -Political organization,economic system (including labor, capital, materials, and power), technology, transportation and communication, education and information, social and intellectual activities (including recreation, cultural facilities, religion, sense of community), safety.

Fig 1. Inputs and Outputs in an Urban Ecosystem

Resource or Waste Product (tonnes) Inputs Total tonnes of fuel, oil equivalent20,000,000 Oxygen 40,000,000 Water 1,002,000,000 Food 2,400,000 Timber 1,200,000 Paper 2,200,000 Plastics 2,100,000 Glass 360,000 Cement 1,940,000 Bricks, blocks, sand and tarmac6,000,000 Metals (total) 1,200,000 Table 1: The Metabolism of Greater London Amount per year

Industrial and demolition wastes 11,400,000 Household, civic, and commercial wastes3,900,000 Wet, digested sewage sludge 7,500,000 CO 2 60,000,000 SO 2 400,000 NOx 280,000 Table 2. Wastes

Figure 2. Urban Energy Production

Tremendous resource input into a modern city: The average urban dweller in the united states uses about 150 gallons of water (directly or indirectly), 4 pounds of food, and 19 pounds of fossil fuels each day Each American consumes 1,400 pounds of steel, travels 5,300 miles between cities, receives 400 pieces of mail, and makes 700 telephone calls per year; and in an average day, city’s inputs are converted into 120 gallons of sewage per person, 4 pounds of refuse per capita, and 1.9 pounds of air pollutants per inhabitant (outputs)

Four spheres of physical environment 1. lithologic environment: solid, nonliving portion of the earth; including landforms, bedrock, and soil 2. atmospheric environment: the gaseous envelope of air (and suspended small solid and liquid aerosols) that surrounds the earth 3. hydrologic environment: consisting of the water portion of the earth 4. Biological environment: living things.

Table 3. Population, Land Area, and Density for the 20 Largest Cities: 1990 RankCity Population (thousands) Land area (sq. miles) Density (average population per sq. mile) New York, NY Los Angeles, CA Chicago, IL Houston, TX Philadelphia, PA San Diego, CA Detroit, MI Dallas, TX Phoenix, AZ San Antonio, TX 7,323 3,485 2,784 1,631 1,586 1,111 1,028 1, ,700 7,400 12,300 3,000 11,700 3,400 7,400 2,900 2,300 2, San Jose, CA Baltimore, MD Indianapolis, IN San Francisco, CA Jacksonville, FL Columbus, OH Milwaukee, WI Memphis, TN Washington, DC Boston, MA ,600 9,100 2,000 15, ,300 6,500 2,400 9,900 11,900

Total increase Major area, region and country World 2,845,049 4,889,393 2,044,344.0 More developed regions 902,993 1,009, ,815.0 (percent) Less developed regions 1,942,056 3,879,585 1,937,529.0 (percent) Least developed countries 167, , ,741.0 (percent) Total World Population 6,055,049 8,111,980 Percent Urban Source: UN World Urbanization Prospects, 1998 Revisions, Electronic Files Table 4: Urban Population by Region,