Chapter 11Chapter 11

The Human Population and it’s impact

Human growth/expansion: Past, Present, Future

How Has the Human Population How Has the Human Population Grown HistoricallyGrown Historically

A. Early Hunter Gatherers1. Nomadic, With a Strong Sense of the Earth

B. Rise of Agriculture1. Necessary for Survival

a. Animals became extinct via predation and altered habitatb. Humans began to cultivate own food

C. Agriculture Gives Rise to Cities1. Food Produced in Country, Consumed in City

a. Food wastes are no longer returned to soilb. Soil becomes less productive

2. Waste of Populations Concentrated in Cities3. Population Control in Medieval Societies

a. Infanticideb. Plagues

D. Industrialization1. View of Children During Early Phases of Industrial Growth

a. Valued as cheap source of income and cheap laborb. Exponential growth of populations

2. By 1900s, Birth Rate in Industrialized World Droppeda. Rise in standards of livingb. Safe and inexpensive means of birth control introducedc. Increase in the cost of child rearing

Current World Population

• Population Clock Vital Events (per time unit)Global population was 7,186,917,280

On August 21, 2014 at 7:35 am

• The global population grows by: • Nearly 4 persons per seconds

• Over 225,000 persons per day

• Over 82 million persons per year

How Much is a Billion?How Much is a Billion?

• 1,000 seconds = 16.7 minutes• 1 million-s = 16,677 min = 11.6 days• 1 billion-s = 11,574 days = 31.7 years• How many years would it take to count every person on the

planet if you counted at the rate of one person per second?• 1,000 pennies = ~ 88 ounces = 5.5 pounds• 1 million pennies = 5,500 pounds (~1-Suburban)• 1 billion pennies = 2,750 tons (~2 Space Shuttles)

• 7 billion pennies = ??? Space Shuttles

Uneven distribution of population growth• Developed – 0.1% per year• Developing – 1.5% per year

Projections in 2050• 10.7 billion• World population growth – 1.19% per year

• What does this say about the globe’s status?

0

2000

4000

6000

8000

10000

1750 1950 1995 2025 2100

developed countriesless developed countries

MILLIONS

• See Figure 11-3 p. 246• Compare with 11-6, p.247

Human Population DynamicsHuman Population Dynamics

• There are just three sources of change in population size:

1. fertility (births)2. mortality (deaths)

• "natural decrease" refers to population decline resulting from more deaths than births

3. migration• Net migration is the number of immigrants minus emigrants

Population Change

• Population Change is calculated by subtracting the number of people leaving a population (death/emigration) from the number entering it (birth/immigration), usually during one year.

• Population Change = (B + I) – (D + E)

• When is the population increasing, decreasing, and staying the same (ZPG)?

Rates of Global Pop. ChangeRates of Global Pop. Changeuse: International Data Base http://www.census.gov/ipc/www/idbnew.html, then Online Demographic Aggregation

• CBR (crude birth rate) = # births / 1000 population1990: 24 now: 20.6

• CDR (crude death rate) = # deaths / 1000 population1990: 9 now: 8.8

• Annual rate of natural population change: • = (birth rate-death rate/1000)*100

1963: 39% 1990: 1.5% now: 1.19%• This equation excludes migration—why?• growth rates have come down (some)

Factors for population increase• ability to expand into new habitats and climate

zones• emergence of modern agriculture• improved health care, sanitation, sources of

water

Human Population DynamicsHuman Population Dynamics• Total fertility rate (TFR) Figure 11-5, p. 247)

• The average number of children born to a woman (age15-49)• Average in developed countries = 1.5• Average in developing countries = 3.8• Worldwide 1990: 3.1 now: 2.76

• Replacement fertility rate (RFR)• The number of children a couple must have to replace

themselves• A TFR of 2.1 for developed countries with low infant and

child mortality rates• Africa RFR = 2.5• Reaching RFR does not necessarily mean ZPG will

immediately be reached (many future parents are already alive)

Factors affecting fertility rate• Children part of labor force• Urbanization (better access to family planning, unneeded for

work – farms)• Cost of raising and educating children• Education/employment of women• Infant mortality rates• Age of marriage• Availability of pension system• Availability of abortions/birth control methods• Religious beliefs/cultural norms, etc.

• World TFR has dropped from 5. 7 to 1.6

Factors affecting death rate

• increased life expectancy due to:• Food supplies• Nutrition• Medical/public health technology• Sanitation/hygiene• Safer water

Population PyramidsPopulation Pyramids• Graphic device: bar graph• shows the age and gender composition of a region• pre-reproductive, reproductive, post-reproductive• horizontal axis: gender

• male: left-hand female: right-hand• absolute number of people or %

• vertical axis: age• 5-year or 10-year age groups

• Population Pyramids on the Web

Population Pyramid with Population Pyramid with young cohortsyoung cohorts

-500 -400 -300 -200 -100 0 100 200 300 400 500

0-4

5-9

10-14

15-19

20-24

25-29

30-34

35-39

40-44

45-49

50-54

55-59

60-64

65-69

70-74

75-79

80-84

85 OR

femalemale

High Growth (Rapid)

Moderate Growth

Zero Growth (Stable)

Negative Growth

Practice

• Predict future growth• Rapid, Stable (slow, negative, zero)• Developing, Developed

Tracking the baby-boom generation in the United StatesTracking the baby-boom generation in the United States

Effects of Population DeclineEffects of Population Decline• As percentage of 60+ aged people increases,

population begins decline• 60+population increase --> severe economic and

social problems because 60+ consume• more medical care• Social Security• costly public services

• Labor shortages require automation & immigration