Transcript geog309_ecosystem_lecture1 - Cal State LA

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
: A special combination of a place and its people
Urban place: (similar to city): the space occupied by a city.
Urban area: a group of coalescent cities or the space occupied by
them.
Urbanization: process of city establishment and growth; the term
commonly connotes population increases in the city, resulting from
both internal growth and immigration, as well as spatially expansion
of the city.
Environment: the aggregate of external conditions that influence the
life of an individual or a population, specifically the life of man.
Includes physical and cultural components.
Cultural components: encompasses the totality of man’s way of living
built up by a human group and transmitted from one generation or
group to another.
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 diseasemortality
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
Table 1: The Metabolism of Greater London
Amount per year
Resource or Waste Product
(tonnes)
Inputs
Total tonnes of fuel, oil equivalent
20,000,000
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 tarmac
6,000,000
Metals (total)
1,200,000
Table 2. Wastes
Industrial and demolition wastes
11,400,000
Household, civic, and commercial wastes
3,900,000
Wet, digested sewage sludge
7,500,000
CO2
60,000,000
SO2
400,000
NOx
280,000
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.
http://www.classzone.com/books/earth_science/terc/content/investigations/es0103/es0103
Table 3. Population, Land Area, and Density for the 20 Largest Cities: 1990
Rank
City
1
2
3
4
5
6
7
8
9
10
New York, NY
Los Angeles, CA
Chicago, IL
Houston, TX
Philadelphia, PA
San Diego, CA
Detroit, MI
Dallas, TX
Phoenix, AZ
San Antonio, TX
11
12
13
14
15
16
17
18
19
20
San Jose, CA
Baltimore, MD
Indianapolis, IN
San Francisco, CA
Jacksonville, FL
Columbus, OH
Milwaukee, WI
Memphis, TN
Washington, DC
Boston, MA
Population
(thousands)
Land area
(sq. miles)
Density
(average
population
per sq. mile)
7,323
3,485
2,784
1,631
1,586
1,111
1,028
1,007
983
936
309
469
227
540
135
324
139
342
420
333
23,700
7,400
12,300
3,000
11,700
3,400
7,400
2,900
2,300
2,800
782
736
731
724
635
633
628
610
607
574
171
81
362
47
759
191
96
256
61
48
4,600
9,100
2,000
15,500
800
3,300
6,500
2,400
9,900
11,900
Table 4: Urban Population by Region, 2000-2030
Total increase
Major area, region and country
World
More developed regions
(percent)
Less developed regions
(percent)
Least developed countries
(percent)
Total World Population
Percent Urban
2000
2,845,049
902,993
31.7
1,942,056
68.3
167,421
5.9
6,055,049
47.0
2030
4,889,393
1,009,808
20.7
3,879,585
2000-2030
2,044,344.0
106,815.0
5.2
1,937,529.0
79.3
94.8
527,162
359,741.0
10.8
17.6
8,111,980
60.3
Source: UN 2000. World Urbanization Prospects, 1998 Revisions, Electronic Files