Environmental Science - 12e - Chapter 07.pdf - po ang - Januszek66

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Applying Population

Ecology: Human Population

and Urbanization

The Ecocity Concept in Curitiba, Brazil

CORE CASE STUDY

Hardly any of today’s urban areas, where half of the world’s peo-

ple live, are environmentally sustainable, although some are

striving to become more sustainable. During this century, envi-

ronmental and urban designers envision more of the world’s

growing urban population living in more environmentally sustain-

able cities, called ecocities or green cities. This is not

just a futuristic dream. One such ecocity is Curitiba, a

city of 2 million people that is known as the “ecologi-

cal capital” of Brazil.

Planners in this city, with its clean air and tree-

lined streets, decided in 1969 to focus on an inexpen-

sive and efficient mass transit system rather than on

the car. Curitiba now has the world’s best bus system,

in which clean and modern buses transport about

72% of the population every day throughout the city

along express lanes dedicated to buses (Figure 7-1).

Only high-rise apartment buildings are allowed near

major bus routes, and each building must devote its

bottom two floors to stores—a practice that reduces

the need for residents to travel. Bike paths run throughout most

of the city. Cars are banned from 49 blocks in the center of the

downtown area, which has a network of pedestrian walkways

connected to bus stations, parks, and bicycle paths.

The city transformed flood-prone areas along its rivers into a

series of interconnected parks crisscrossed with bicycle paths.

Volunteers have planted more than 1.5 million trees throughout

the city, none of which can be cut down without a permit, and

two trees must be planted for each one cut down.

Curitiba recycles roughly 70% of its paper and 60% of its

metal, glass, and plastic, which is collected from households

three times a week. Recovered materials are sold mostly to the

city’s more than 500 major industries, which must meet strict

pollution standards.

The city uses old buses as roving classrooms to train its poor

in the basic skills needed for jobs. Other retired buses have be-

come health clinics, soup kitchens, and day-care centers, which

are open 11 hours a day and are free for low-income parents.

The city tries to provide water, sewage, and bus service for

most of its growing and unplanned squatter settlements. It has

designed tracts of land for settlements with clean running water

as a way to reduce the spread of infectious disease. The city has

a build-it-yourself system that gives a poor family a plot of land,

building materials, two trees, and an hour’s consultation with

an architect.

About 95% of its citizens can read and write, and 83% of

adults have at least a high school education. All school children

study ecology. Polls show that 99% of the city’s inhabitants

would not want to live anywhere else.

This internationally acclaimed model of urban planning

and sustainability is the brainchild of

architect and former college teacher

Jaime Lerner, who has served as the

city’s mayor three times since 1969. It

will be an exciting challenge during

this century to reshape existing cities

and design new ones using the

Curitiba model.

City

center

Route

Express

Interdistrict

Direct

Feeder

Workers

Figure 7-1 Solutions: bus system in Curitiba, Brazil. This system moves

large numbers of passengers around rapidly because each of the five

major spokes has two express lanes used only by buses. Double- and

triple-length bus sections are hooked together as needed to carry up to

300 passengers. Boarding is speeded up by the use of extra-wide doors

and raised tubes that allow passengers to pay before getting on the bus

(top left).

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Key Questions and Concepts

7-1 How many people can the earth support?

CONCEPT 7-1 We do not know how long we can continue

increasing the earth’s carrying capacity for humans without seri-

ously degrading the life-support system for us and many other

species.

7-5 What are the major population and

environmental problems of urban areas?

CONCEPT 7-5 Cities can improve individual lives, but most cities

are unsustainable because of high levels of resource use, waste,

pollution, and poverty.

7-2 What factors influence population size?

CONCEPT 7-2A Population size increases because of births and

immigration and decreases through deaths and emigration.

CONCEPT 7-2B The average number of children born to

women in a population ( total fertility rate ) is the key factor that

determines the population size.

7-6 How does transportation affect urban

development?

CONCEPT 7-6 A combination of plentiful land, inexpensive fuel,

and an expanding network of highways results in dispersed cities

that depend on motor vehicles for most transportation.

7-7 How can cities become more sustainable

and livable?

CONCEPT 7-7 An ecocity allows people to: choose walking,

biking, or mass transit for most transportation needs; recycle or

reuse most of their wastes; grow much of their food; and protect

biodiversity by preserving surrounding land.

7-3 How does a population’s age structure affect

its growth or decline?

CONCEPT 7-3 The numbers of males and females in young,

middle, and older age groups determine how fast populations grow

or decline.

7-4 How can we slow population growth?

CONCEPT 7-4 Experience indicates that the most effective ways

to slow population growth are to invest in family planning, to

reduce poverty, and to elevate the status of women.

Note: Supplements 3 and 4 can be used with this chapter.

The problems to be faced are vast and complex,

but come down to this:

6.7 billion people are breeding exponentially.

The process of fulfilling their wants and needs

is stripping earth of its biotic capacity to produce life;

a climactic burst of consumption

by a single species is overwhelming

the skies, earth, waters, and fauna.

PAUL HAWKEN

How Many People Can the Earth Support?

7-1

CONCEPT 7-1 We do not know how long we can continue increasing the earth’s carrying

capacity for humans without seriously degrading the life-support system for us and many

other species.

Human Population Growth Continues

But Is Unevenly Distributed

For most of history, the human population grew slowly

(Figure 1-1, left part of curve, p. 5). But for the past

200 years, the human population has experienced

rapid exponential growth reflected in the characteristic

J-curve (Figure 1-1, right part of curve, p. 5).

Three major factors account for this population in-

crease. First, humans developed the ability to expand

into diverse new habitats and different climate zones.

Second, the emergence of early and modern agriculture

124

Links:

refers to the Core Case Study.

refers to the book’s sustainability theme.

indicates links to key concepts in earlier chapters.

83376_08_ch07_p123-148.ctp 8/10/07 12:22 PM Page 125

allowed more people to be fed per unit of land area.

Third, the development of sanitation systems, antibi-

otics, and vaccines helped control infectious disease

agents. As a result, death rates dropped sharply below

birth rates and the population grew rapidly.

About 10,000 years ago when agriculture began,

there were about 5 million humans on the planet; now

there are 6.7 billion of us. It took from the time we ar-

rived until about 1927 to add the first 2 billion people to

the planet; less than 50 years to add the next 2 billion

(by 1974); and just 25 years to add the next 2 billion (by

1999)—an illustration of the awesome power of expo-

nential growth ( Core Case Study , p. 5). By 2012 we will

be trying to support 7 billion people and perhaps 9.2 bil-

lion by 2050.

The rate of population growth has slowed, but the

world’s population is still growing exponentially at a

rate of 1.23% a year. This meant that 82 million people

were added to the world’s population during 2007—an

average of nearly 225,000 more people each day, or 2.4

more people every time your heart beats.

Geographically this growth is unevenly distributed.

About 1.2 million of these people were added to the

1.2 billion people living in the developed countries

growing at 0.1% a year. About 80.8 million were

added to the 5.6 billion people in developing countries

growing 15 times faster at 1.5% a year. In other

words, most of the world’s population growth takes

place in already heavily populated parts of the world,

which are the least equipped to deal with the pres-

sures of such rapid growth.

NATURAL CAPITAL

DEGRADATION

Altering Nature to Meet Our Needs

Reduction of biodiversity

Increasing use of the earth's net primary productivity

Increasing genetic resistance of pest species and disease-

causing bacteria

Elimination of many natural predators

Deliberate or accidental introduction of potentially

harmful species into communities

Using some renewable resources faster than they can be

replenished

Interfering with the earth's chemical cycling and energy

flow processes

Relying mostly on polluting fossil fuels

We Do Not Know How Long

the Human Population Can

Keep Growing

To survive and provide resources for growing numbers

of people, humans have modified, cultivated, built on,

or degraded a large and increasing portion of the

earth’s natural systems. Our activities have directly af-

fected to some degree about 83% of the earth’s land

surface, excluding Antarctica (Figure 3 on p. S16–S17

in Supplement 4), as our ecological footprints have

spread across the globe ( Concept 1-3 , p. 11,

and Figure 1-8, p. 13).

We have used technology to alter much of the rest

of nature to meet our growing needs and wants in

eight major ways (Figure 7-2).

Active Figure 7-2 Major ways humans have altered the rest of nature

to meet our growing population and its resource needs and wants ( Concept 7-1 ) See

an animation based on this figure at ThomsonNOW. Questions: Which three of these

items do you believe have been the most harmful? Why? How does your lifestyle con-

tribute directly or indirectly to each of these items?

continue increasing the earth’s carrying capacity for

our species by sidestepping many of the factors that

sooner or later limit the growth of any population?

No one knows, but mounting evidence indicates

that

are

steadily

degrading

the

natural

capital

( Concept 1-1A , p. 6, and Figure 1-6, p. 12)

that keeps us and other species alive and

supports our economies ( Concept 7-1 ).

How many of us are likely to be here in 2050? An-

swer: 7.2–10.6 billion people, depending mostly on

projections about the average number of babies

women are likely to have. The medium projection is

9.2 billion people (Figure 7-3, p. 126). About 97% of

this growth is projected to take place in developing

countries, where acute poverty is a way of life for

about 1.4 billion people. Are there too many people on

the earth? Some say yes and some say no, as discussed

in the Case Study that follows.

Examine how resources have been depleted or

degraded around the world at ThomsonNOW.

Scientific studies of populations of other

species tell us that no population can continue

growing indefinitely ( Concept 6-5 , p. 117), which

is one of the four scientific principles of sustain-

ability (Figure 1-13, p. 20). How long can we

125

CONCEPT 7-1

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As a result, they see no need for controlling the

world’s population growth. Some people also view any

form of population regulation as a violation of their re-

ligious or moral beliefs. Others see it as an intrusion

into their privacy and personal freedom to have as

many children as they want.

Proponents of slowing and eventually stopping

population growth have a different view. They point

out that we now fail to provide the basic necessities for

about one of every five people—a total of about 1.4 bil-

lion (Figure 1-11, p. 16). They ask, how will we be able

to do so for the projected 2.5 billion more people by

2050?

They also warn of two serious consequences if we

do not sharply lower birth rates. First, death rates may

increase because of declining health and environmental

conditions in some areas, as is already happening in

parts of Africa. Second, resource use and environmental

degradation (Figure 1-6, p. 12) may intensify as more

consumers increase their already large ecological foot-

prints in developed and rapidly developing cou ntries

( Concept 1-3 , p. 11, and Figure 1-8, p. 13). This

could increase environmental stresses such as

infectious disease, biodiversity losses, water shortages,

traffic congestion, pollution of the seas, and climate

change.

This debate over interactions among population

growth, economic growth, politics, and moral beliefs is

one of the most important and controversial issues in

environmental science.

High

10.8

High

Medium

Low

Medium

9.2

Low

7.8

1950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050

Year

Figure 7-3 Global connections: UN world population projections,

assuming that by 2050 women have an average of 2.5 children

(high estimate), 2.0 children (medium), or 1.5 children (low). The

most likely projection is the medium one—9.2 billion by 2050. (Data

from United Nations)

■ CASE STUDY

Are There Too Many of Us?

Each week about 1.6 million people are added to the

world’s population. As a result, the number of people

on the earth is projected to increase from 6.7 to 9.2 bil-

lion or more between 2007 and 2050 (Figure 7-3), with

most of this growth occurring in developing countries.

This raises an important question: Can the world provide

an adequate standard of living for a projected 2.5 billion more

people by 2050 without suffering widespread environmental

damage? There is disagreement over the answer to this

question.

According to some analysts, the planet already has

too many people collectively degrading the earth’s natu-

ral capital. To some, the problem is the sheer number of

people in developing countries with 82% of the world’s

population. To others, it is high resource consumption

rates in developed countries—and to an increasing ex-

tent in rapidly developing countries such as China and

India—that magnify the environmental impact of each

person (Figure 1-8, p. 13, and Case Study, p. 13). To

many, both population growth and resource consump-

tion per person are important causes of the en viron-

mental problems we face ( Concept 1-5A , p. 15).

Others point out that technological ad-

vances have allowed humans to avoid the environ-

mental resistance that all populations face (Figure 6-11,

p. 119) and increase the earth’s carrying capacity

for humans. They see no reason for this to end and be-

lieve that the world can support billions more people.

They also see more people as a valuable resource for

solving environmental and other problems and for

stimulating economic growth by increasing the number

of consumers.

■ ✓

HOW WOULD YOU VOTE?

Should the population of the country where you live be

stabilized as soon as possible? Cast your vote online at

www.thomsonedu.com/biology/miller .

How many people can the earth support indefi-

nitely? Some say about 2 billion. Others say as many as

30 billion.

Some analysts believe this is the wrong question.

Instead, they say, we should ask what the optimum sus-

tainable population of the earth might be, based on the

planet’s cultural carrying capacity. Such an optimum level

would allow most people to live in reasonable comfort

and freedom without impairing the ability of the planet

to sustain future generations. (See the Guest Essay on

this topic by Garrett Hardin at ThomsonNOW™.)

THINKING ABOUT

Population Growth

What do you think is (a) the maximum human population

size and (b) the optimum human population size? How do

your answers reflect your position on whether the world is

overpopulated?

RESEARCH FRONTIER

Determining the optimum sustainable population size for the

earth and for various regions

126

CHAPTER 7

Applying Population Ecology: Human Population and Urbanization

83376_08_ch07_p123-148.ctp 8/10/07 12:22 PM Page 127

What Factors Influence Population Size?

7-2

CONCEPT 7-2A Population size increases because of births and immigration and

decreases through deaths and emigration.

CONCEPT 7-2B The average number of children born to women in a population ( total

fertility rate ) is the key factor that determines population size.

Populations Can Grow, Decline,

or Remain Fairly Stable

On a global basis, if there are more births than deaths

during a period of time, the earth’s population increases

and when the reverse is true, it decreases. When births

equal deaths, population size stabilizes ( Concept 7-2A ).

In particular countries, cities, or other areas, hu-

man populations grow or decline through the interplay

of three factors: births ( fertility ), deaths ( mortality ), and

migration. We can calculate population change of an

area by subtracting the number of people leaving a

population (through death and emigration) from the

number entering it (through birth and immigration)

during a specified period of time (usually one year)

( Concept 7-2A ).

Population

change

affect a country’s population size and growth rate. The

first type, called the replacement-level fertility rate,

is the average number of children that couples in a

population must bear to replace themselves. It is

slightly higher than two children per couple (2.1 in de-

veloped countries and as high as 2.5 in some develop-

ing countries), mostly because some children die before

reaching their reproductive years.

Does reaching replacement-level fertility bring an

immediate halt to population growth? No, because so

many future parents are alive. If each of today’s couples

had an average of 2.1 children, they would not be con-

tributing to population growth. But if all of today’s girl

children also have 2.1 children, the world’s population

will continue to grow for 50 years or more (assuming

death rates do not rise).

The second type of fertility rate, the total fertility

rate (TFR), is the average number of children born to

women in a population during their reproductive

years. This factor plays a key role in determining popu-

lation size ( Concept 7-2B ). The average fertility rate has

been declining. In 2007, the average global TFR was

2.7 children per woman: 1.6 in developed countries

(Births

Immigration)

(Deaths

Emigration)

When births plus immigration exceed deaths plus emi-

gration, population increases; when the reverse is true,

population declines.

Instead of using the total numbers of births and

deaths per year, population experts (demographers)

use the birth rate, or crude birth rate (the number

of live births per 1,000 people in a population in a

given year), and the death rate, or crude death rate

(the number of deaths per 1,000 people in a population

in a given year).

What five countries had the largest numbers of peo-

ple in 2007? Number 1 is China with 1.3 billion people,

or one of every five people in the world. Number 2 is

India with 1.1 billion people, or one of every six people.

Together China and India have 37% of the world’s pop-

ulation. The United States, with 300 million people in

2007, has the world’s third largest population but only

4.5% of the world’s people.

Can you guess the next two most populous coun-

tries? What three countries are expected to have the

most people in 2025? Look at Figure 7-4 to see if your

answers are correct.

1.3 billion

1.5 billion

China

1.1 billion

India

1.4 billion

302 million

349 million

USA

232 million

271 million

Indonesia

169 million

229 million

Pakistan

189 million

229 million

Brazil

144 million

205 million

Nigeria

149 million

190 million

Bangladesh

Women Are Having Fewer Babies

But Not Few Enough to Stabilize

the World’s Population

Another measurement used in population studies is

fertility rate, the number of children born to a

woman during her lifetime. Two types of fertility rates

142 million

128 million

Russia

2007

2025

128 million

119 million

Japan

Figure 7-4 Global connections: the world’s 10 most populous

countries in 2007, with projections of their population sizes in 2025

(Data from World Bank and Population Reference Bureau)

127

CONCEPTS 7-2A AND 7-2B

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