10/20/2014

1

Chapter 8Population Change

Overview of Chapter 8

Principles of Population Ecology

Factors that Affect Population Size

Reproductive Strategies

The Human Population

Demographics

Principles of Population Ecology

Population Ecology

Study of populations and why their numbers change over time

Important for

Endangered species

Invasive species

Population

Group of individuals of same species living in the same geographic area at the same time

10/20/2014

2

Population Density

Population density

The number of individuals of a species per unit area or volume at a given time

Ovals below have same population, and different densities

Change in Population Size

Change in Population Size

10/20/2014

3

Growth

rate

Birth

rate

Death

rate

Immigration

rate

Emigration

rate

r = (b – d) + (i – e)

Calculating Population Change

Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 people

Maximum Population Growth

Intrinsic Rate of Growth (Biotic Potential)

Growth rate under ideal conditions

J- Shaped Curve (exponential growth)

Environmental Resistance

Environmental Resistance

Prevent indefinite reproduction

Available food, water, shelter, predation, etc.

Carrying Capacity (K)

Maximum # of individuals an environment can support

Causes leveling off of exponential growth

S-shaped curve of logistic population growth

10/20/2014

4

Population Crash

Overshooting carrying capacity can lead to population crash

Abrupt decline in population density

Boom and Bust = rapid population growth and consumption followed by sudden collapse

Often caused by density-dependent factors

Effect on population changes as population density changes

Examples:

Predation

Disease

Competition

Boom and Bust Population Cycles

10/20/2014

5

Human Population

Human population in modern age is J-shaped curve

Population Increase in Mexico

Projecting Future Populations

Population is increasing

Growth rate (r) has started to decline

Projections for 2050

Low = 7.7 billion

High = 10.6 billion

Most likely = 9.1 billion

10/20/2014

6

Demographics of Countries

Demographics of Countries

Demographic Stages

Pre-industrial Stage

Birth and death rates high, modest population growth

Transitional Stage

Lowered death rate, rapid population growth

Industrial Stage

Birth rate decline, population growth slow

Post Industrial Stage

Low birth and death rates, population growth very slow

10/20/2014

7

Demographic Stages

Age Structure Diagrams

Population and Quality of Life

Difficult to meet basic needs in developing countries

Problems associated with overpopulation: Environmental

degradation

Hunger

Persistent poverty

Economic stagnation

Urban deterioration

Health issues

10/20/2014

8

Food insecurity

In shaded countries, more than 20% of population is undernourished

Reducing the Total Fertility Rate

Three major influences on total fertility rate

1. Cultural traditions

2. Social & economic status of women

3. Family planning

Single most important factor = low social status of women worldwide

Cultural influences: Marriage age

Number of children – often related to infant mortality rates

Whether children work in family business

Religious values and views on gender roles and birth control

Cultural Traditions

10/20/2014

9

Gender inequality is common worldwide

Disparities

Political participation

Social status

Economic status

Legal rights

Education

Employment and

earningsIlliteracy rates in 2002

Social & Economic Status of Women

Educational Opportunities and Fertility

Women with more education tend to:

Marry later

Have fewer children

United States

Family Planning

Family planning services offer information to men and women on contraception, STDs, and parenting

Often hindered by religious or cultural values

10/20/2014

10

Achieving Population Stabilization

How can developing country governments help? Increase funding to pubic health and family planning

services

Education on methods of birth control

Increase average level of education

How can developed country governments help? Provide financial support

Support research and development of new birth control methods

Chapter 9

The Urban Environment

Population and Urbanization

Milestone: As of 2008, more than half of the world’s population lives in urban areas

10/20/2014

11

Characteristics of Urban Populations

Basic characteristics of city populations:

Diverse population in terms of race, ethnicity, religion, and socioeconomic status

Younger population than local rural area

More males in cities of developing nations

More females incities of developednations

Substandard Housing

1/3 of urban population in developing countries are squatters

no legal ownership of land or housing

Few or no city services

Water

Sewage treatment

Garbage collection

Police and fire protection

Schools

Libraries

United States Urban Agglomerations

(Population of 50,000 or above)

Urbanization Trends

Urban Agglomeration

Urbanized core region that consists of several adjunct cities or megacities and their surrounding developed suburbs

10/20/2014

12

Environmental Problems in Urban Areas

Growing urban areas affect land use patterns

Fragment wildlife

Encroach wetlands, forests, desert, etc.

Impermeable surfaces and urban runoff discharged into waterways

Motor oil, lawn fertilizers, heavy metals, etc.

Noise pollution

Suburban Sprawl

Suburban Sprawl

Patchwork of developed tracts around the edges of larger cities

Drawbacks

Air pollution

Increased traffic

Water pollution

Runoff

Loss of habitat

Suburban Sprawl

How far can it go? - Los Angeles

10/20/2014

13

Making Cities More Sustainable

Clear urban growth policies and planning

Reduction of pollution and waste

Collect runoff water (slow it, spread it, sink it)

Open space: parks, greenbelts, preserves

People-centered, not car-centered

Food grown in or near city

Rooftop gardens, local farms

Compact development

Living wage for residents

Reduce need for commuting

Sustainable Cities

Portland, OR

San Francisco, CA

Seattle, WA

Minneapolis, MN

Austin, TX

Eugene, OR

New York City, NY

Salt Lake City, UT

Grand Rapids, MI

Philadelphia, PA

Chicago, IL

Los Angeles, CA

http://billmoyers.com/content/12-cities-leading-the-way-in-sustainability/

Portland

Austin