Applying Population Ecology: The Human Population

Chapter 5


Current Population Trends

World population = 6.4 billion (6,400,000,000) in 2004

Doubled since 1963 = 3.2 billion

In 2050 could be 7.2 10.6 billion

Amplifies all environmental problems

Largest increase expected in developing countries

Decreasing in some developed countries

Is human population experiencing exponential growth?


Factors Affecting Human Population Size

Population change equation

Population change = (Births + Immigration) (Deaths + Emigration)


Crude birth rate = births per 1000 people in population per year

Crude death rate = deaths per 1000 people in population per year


Sex Ratio - Age Distribution

Sex Ratio- Relative number of males and females in a population

Age Distribution - Number of individuals of each age in a population


Together they tell how a population will grow


Population Age Structure


Human Population Issue

Several factors determine the impact of a society on natural resources.

Population size

Population density

Degree of technological development

Demography - Study of populations and their characteristics.

Environmental Impact


Total Fertility Rate (TFR) - Number of children a woman has during her lifetime, averaged for population.

same as biotic potential (r)

Replacement Level Fertility - Number of children needed to replace everyone in the population.

Varies between regions

2.1 with low infant mortality

2.5 with high infant mortality

Zero Population Growth - Birth rate equals death rate.


Factors Affecting Birth Rates and Total Fertility Rates

Children in Labor Force

Cost of raising and educating children

Availability of pension systems


Education and employment for women

Infant mortality rate

Average marrying age


Availability of birth control



Major social factor determining family size is the role of women in society.

Early marriages foster high fertility rates.

Lack of education opportunities for women reduces their options.

When level of education increases, fertility rates fall.

The most important factor is the ability of women to control the size of their family.

Access to birth control is key.


United States Population Picture

US population has a post-war baby boom period, significantly affecting pop. trends.

20 yr period following WWII

By 2030, 20% of US pop will be over 65

U.S. Birth Rates: 1910-2004


US Immigration rates

Demographic Transition

Case Study: Slowing Population Growth in India

Generally disappointing results

Poor planning

Bureaucratic inefficiency

Low status of women

Extreme poverty

Lack of support

Case Study: Slowing Population Growth in China

Economic incentives

Free medical care

Preferential treatment

Locally administered

Very intrusive and coercive


Cutting Global Population Growth

Family planning

Improve health care

Elevate the status of women

Increase education

Involve men in parenting

Reduce poverty



Global megacities

Urban Poor in Developing Countries



Squatter settlements




Illegal settlements


Poverty and unemployment


US metropolitan areas

Undesirable impacts of urban sprawl

Urban Land-Use Planning and Control

Land-use planning

Property taxes


Smart growth

Urban growth boundary




Mass transit vs. automobile

What makes one or the other feasible?

Why is most of the US developed around cars? When did it happen?

Where does mass transit work?

What are the pros and cons to each?

Sustainable city solutions