Population Ecology: Human
Population and Its Impact
Mrs. R. Brown
Milton High School
AP Environmental
What is demography and why is
it important?
The study of the vital statistics that affect population size.
- Size
- Age Distribution
- Density
- Dispersion
World Population Clock
http://www.census.gov/main/www/popclock.html
Is the world overpopulated?
The world’s population is projected
to increase from 6.6 billion to 8.9
billion by 2050.
The debate over interactions
among population growth,
economic growth, politics, and
moral beliefs is one of the most
important and controversial issues
in environmental science.
Can our Earth support more people?
Some argue that the planet has
too many people.
Some feel that the world can
support billions of more people
due to technological advances.
There is a constant debate over
the need to reduce population
growth. (Must consider moral,
religious, and personal freedom.)
Human Population Growth
World population growth rate
1.25%
This adds 80 million
people a year.
Population Growth Variables
 Crude Birth Rate (CBR)
 Crude Death Rate (CDR)
 Immigration
 Emigration
 Density Dependant Factors
 Density Independent Factors
 Cultural Practices
 Technology Revolutions
Where are we headed?
U.N. world population
projection based on
women having an
average of 2.5 (high),
2.0 (medium), or 1.5
(low) children.
Factors Affecting Human
Population Size
•Births
•Deaths
•Migration
Crude Birth Rate – the number of births per 1,000
people in a population in a given year
Crude Death Rate: the total number of deaths per 1000 people. Usually it is
measure per country. The crude death rate for the whole world is currently
about 9.6 per 1000 per year (based on 62 million deaths in 2006, for a
population of 6470 million).
Total Fertility Rate (TFR) – the average number of children a
woman typically has during her reproductive years.
Average crude
birth rate
Average crude
death rate
21
World
9
All developed
countries
All developing
countries
Developing
countries
(w/o China)
11
10
23
8
27
9
Poverty affects population growth
 Develop Countries Growth Rate 0.1%
 Undeveloped Countries Rate 1.15%
How long will it take for the world’s
population to double?
Rule of 70 – Doubling Time
• Life expectancy/growth rate
• 70/1.14 = 61 years
Indicators of population growth or decline
 Natural Increase Rate (NIR)
Percentage by which the population grows in a year.
 Total Fertility Rate (TFR)
Average number of children a women will have in her
lifetime.
 Infant Mortality Rate (IMR)
Average number of infant deaths under 1 year of age,
compared with total live births
Population Growth Rate
CIA World Factbook
The average annual percent change in the population, resulting
from a surplus (or deficit) of births over deaths and the balance of
migrants entering and leaving a country. The rate may be positive
or negative. The growth rate is a factor in determining how great a
burden would be imposed on a country by the changing needs of
its people for infrastructure (e.g., schools, hospitals, housing,
roads), resources (e.g., food, water, electricity), and jobs. Rapid
population growth can be seen as threatening by neighboring
countries.
https://www.cia.gov/library/publications/the-world-factbook/fields/2002.html
Changes in U.S. Fertility
Factors affecting fertility and births
 Infant mortality rate
 Average age at marriage
 Ability of Legal Abortions
 Availability of Reliable Birth Control Methods
 Religious beliefs, traditions, and cultural norms
 Importance of children as part of the labor force
 Cost of raising and educating children
 Availability of private and public pension systems
 Urbanization
 Educational and employment opportunities available for women
 Importance of young adults joining the military
How can family planning help?
 Birth Spacing
 Birth Control
 Health Care for Pregnant Women
 Heath Care for Infants
Key Factors to Fewer Children
 Ensuring education
 Having jobs outside the home
 Living in societies where their rights are not suppressed
Two useful indicators of overall health
of people in a country or region
• Life expectancy
• Infant mortality rate
Life Expectancy – the average number of
years a newborn infant can expect to live
Infant Mortality Rate – the number of babies out of
every 1,000 born who die before their first birthday
Why death rates have declined
•
•
•
•
•
Food supplies and distribution
Better nutrition
Medical advances in vaccines and antibiotics
Improved sanitation
Safer water supplies
Infant mortality and female literacy
Age structure diagrams
 Shows the distribution of
various age groups in a
population.
 A great deal of information
about the population broken
down by age and sex can be
read from a population
pyramid, and this can shed
light on the extent of
development and other
aspects of the population.
Populations with a large proportion of its people in
the pre-reproductive ages of 1-14 have a large
potential for rapid population growth
Teenagers and Pyramids
 The number of people under age 15 is
the major factor determining a country’s
future population growth.
 Population pyramids can be used to
find the number of economic dependents
being supported in a particular
population.
 30% (1.9 billion) of people on the
planet were under 15 years of age in
2004.
Economic Projections
 Who will need education
 Who will need jobs
 Who will determine markets
 Who will affect elections
 Who will need Medicare
How do human populations develop
economically?
Demographic Transition Model
A model used to explain
the process of shift from
high birth rates and high
death rates to low birth
rates and low death rates
as part of the economic
development of a
country from a preindustrial to an
industrialized economy.
Pre-industrial stage (Stage 1)
 High birth and death rates
 Low medical care (natural meds)
 Population limited by food
availability (internal)
Transitional Stage (Stage 2)
 Increased food production
 Better medical care (esp. antibiotics)
 Improved sanitation (esp. drinking water)
 Decreased death rate
 Birth rate stays high (cultural norms)
 Period of rapid growth rate
Industrial Stage (Stage 3)
 Need for increased labor force
 Availability of education (esp. female)
 Delay in age of 1st reproduction
 Change in cultural norms
 Birth rates decline toward zero population growth (ZPG)
Post-industrial Stage (Stage 4)
 Industrial system no longer supports population
 High unemployment, poverty
 Food supplies diminish
 Environmental health declines (high disease)
 Social strife (disease, famine, war)
 Increased death rates and decreased birth rates
Problems associated with rapid
population decline
 Can threaten economic growth
 Less government revenues with fewer workers
 Less entrepreneurship and new business formation
Less likelihood for new technology development
Increasing public deficits to fund higher pension and healthcare
Altering nature to
meet our needs