Population Ecology

1
Chapter 8

• Population Ecology

2
Core Case Study Southern Sea Otters Are They
Back from the Brink of Extinction?

• They were over-hunted to the brink of extinction
  by the early 1900s and are now making a
  comeback.

Figure 8-1
3
Core Case Study Southern Sea Otters Are They
Back from the Brink of Extinction?

• Sea otters are an important keystone species for
  sea urchins and other kelp-eating organisms.

Figure 8-1
4
Characteristics of Population

• Population dynamics
• Population size
• Population density
• Carrying Capacity

5
Exponential and Logistic Growth
Year
Year
6
Environmental Resistance
Carrying capacity (K)
Population size (N)
Exponential Growth
Time (t)
Fig. 8-3, p. 163
7
Exceeding Carrying Capacity Move, Switch Habits,
or Decline in Size

• Members of populations which exceed their
  resources will die unless they adapt or move to
  an area with more resources.

Figure 8-6
8
Chapter 9

• Applying Population Ecology
• The Human Population and Its Impact

9
Core Case Study Is the World Overpopulated?

• The worlds population is projected to increase
  from 6.6 billion to 8.9 billion between 2006 and
  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.

10
Core Case Study Is the World Overpopulated?

• 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.

11
Factors Affecting Death Rates

• Death rates have declined because of
• Increased food supplies, better nutrition.
• Advances in medicine.
• Improved sanitation and personal hygiene.
• Safer water supplies.
• U.S. infant mortality is higher than it could be
  (ranked 46th world-wide) due to
• Inadequate pre- and post-natal care for poor.
• Drug addiction.
• High teenage birth rate.

12
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.

Figure 9-2
13
Factors Affecting Human Population Size

• Population change equation

• Zero population growth (ZPG)

• Crude birth rate (BR)- per 1000

• Crude death rate (DR)- per 1000

14
Core Case Study Is the World Overpopulated?

• Much of the worlds population growth occurs in
  developing countries like China and India.

Figure 9-1
15
Case Study Slowing Population Growth in China-
1 child policy
Generally positive results

• Economic incentives

• Free medical care

• Preferential treatment

• Intrusive and coercive

16
Case Study Slowing Population Growth in Thailand
Generally positive results

• 3.2 growth, 6 child family

• Woman literacy, economic role

• Religion support- Buddhist

• openmindness

17
Case Study Slowing Population Growth in India
Generally disappointing results

• Poor planning

• Bureaucratic inefficiency

• Low status of women

• Extreme poverty

• Lack of support

18
POPULATION AGE STRUCTURE-Japan

• Age structure predictions based on a medium
  fertility projection.
• The cost of an aging population will strain the
  global economy.

Figure 9-12
19
How Would You Vote?

• Should the population of the country where you
  live be stabilized as soon as possible?
• a) Yes. Governments should use incentives and
  penalties.
• b) Yes. However, only through indirect means,
  like education, or by relying on demographic
  transition.
• c) No. The population of my country could
  continue to grow without serious consequences.

20
Solutions Influencing Population Size

• Migration

• Reducing births

• Family planning

• Empowerment of women

• Economic rewards and penalties

21
United States Population

• US BRs and TFRs

Fig. 9.6
22
POPULATION AGE STRUCTURE

• Today, baby boomers make up nearly half of all
  adult Americans and dominate the populations
  demand for goods and services.

Figure 9-11
23
1907
1914
New laws restrict Immigration
Number of legal immigrants (thousands)
Great Depression
Year
Fig. 9-8, p. 178
24
How Would You Vote?

• Should legal immigration into the United States
  (or the country where you live) be reduced?
• a) Yes Because of threats of terrorism and the
  burden on the economy, immigration should be
  reduced.
• b) No. Humane efforts should be made to curtail
  illegal immigration, but our economy needs legal
  immigrants.

25
POPULATION AGE STRUCTURE

• About 14 of the worlds population live in
  countries with stabilizing or declining
  populations.
• Rapid population decline can lead to long-lasting
  economic and social problems.
• Death from AIDS can disrupt a countrys social
  and economic structure by removing significant
  numbers of young adults.

26
POPULATION AGE STRUCTURE

• The number of people in young, middle, and older
  age groups determines how fast populations grow
  or decline.
• The number of people younger than age 15 is the
  major factor determining a countrys population
  growth.
• Changes in the distribution of a countrys age
  groups have long-lasting economic and social
  impacts.

27
POPULATION AGE STRUCTURE

• Populations with a large proportion of its people
  in the preproductive ages 1-14 have a large
  potential for rapid population growth.

Figure 9-9
28
SOLUTIONS INFLUENCING POPULATION SIZE

• Demographic Transition As countries become
  economically developed, their birth and death
  rates tend to decline.
• Preindustrial stage little population growth due
  to high infant mortality.
• Transitional stage industrialization begins,
  death rates drops and birth rates remain high.
• Industrial stage birth rate drops and approaches
  death rate.

29
SOLUTIONS INFLUENCING POPULATION SIZE

• Generalized model of demographic transition.
• Some developing countries may have difficulty
  making the demographic transition.

Figure 9-14
30
Lester Brown

• Our numbers expand but Earths natural systems do
  not.
• End chapter 8 and 9