human population : growth, demography and carrying capacity

Human PopulationHuman Population:: Growth, Demography and Carrying Capacity Growth, Demography and Carrying Capacity

Current World PopulationGlobal population was 6,629,514,472

On November 7, 2007 at 08:05 pm

• The global population grows by: – Nearly 2.3 persons per seconds

– Nearly 8,343 persons per hour

– Over 200,234 persons per day

– Over 73 million persons per year

Human Population DynamicsHuman Population Dynamics

There are just three sources of change in population size —

Fertility – number of children born Mortality -"natural decrease" refers to

population decline resulting from more deaths than births

Migration - Net migration is the number of immigrants minus emigrants

Human Population DynamicsHuman Population DynamicsReplacement fertility rate (RFR)

– The number of children a couple must have to replace themselves

Total fertility rate (TFR)– The average number of children born to a

woman during childbearing years (15-49)– Average in developed countries = 1.6 (1950 2.5)– Average in developing countries = 3.1 (1950: 6.5)

Infant Mortality Rate (IMR )

• infant deaths per 1000 live births (infant < 1 yr)– 1990: 62 now: 52 (normal in 1900: 200)– Current US IMR: 6.9% (69/1000)

Maternal Deaths per 100,000 Live BirthsMaternal Deaths per 100,000 Live Births

Source: WHO, UNICEF, UNFPA Maternal Mortality in 1995: Estimates Developed

by WHO, UNICEF AND UNFPA, 2001.

• Overall, the world population is growing at a rate of about 1.7%; if this rate continues, the population will double in 42 years.

Population PyramidsPopulation Pyramids• Graphic device: bar graph• shows the age and gender composition of a

region• 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 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

female

male

Population PyramidsPopulation Pyramids

• High Growth: Afghanistan• Moderate Growth: Mexico

• Zero Growth: U.S.

• Negative Growth: Austria or Italy

Population PyramidsPopulation Pyramids• Population Pyramids on the Web

• High Growth: Afghanistan

• Moderate Growth: Mexico • Zero Growth: U.S.

• Negative Growth: Austria or Italy

Population PyramidsPopulation Pyramids• Population Pyramids on the Web

• High Growth: Afghanistan

• Moderate Growth: Mexico

• Zero Growth: U.S. • Negative Growth: Austria or Italy

Population PyramidsPopulation Pyramids• Population Pyramids on the Web

• High Growth: Afghanistan

• Moderate Growth: Mexico

• Zero Growth: U.S.

• Negative Growth: Italy

• Movement of a nation from high population growth to low population as it develops economically

• Transition as a result of four stages– Stage 1—Birth and death rates are both high– Stage 2—Death rates fall; birth rates remain high;

growth rate rises– Stage 3—Birth rates fall as standard of living

rises; growth rate falls– Stage 4—Growth rate continues to fall to zero or

to a negative rate

Demographic TransitionDemographic Transition

Population Pyramids and Population Pyramids and Demographic StagesDemographic Stages

• characteristics shapes of ‘pyramids’– wide base (true pyramid)– wide middle (bulge), somewhat wider base– urn- or bottle-shaped– reversed pyramid

• different shapes--different dynamics

Population Pyramid and Demographic TransitionPopulation Pyramid and Demographic Transition• Stage 2: wide base• stage 3: wide middle

• stage 4: slender

• stage 5: narrow base

Population Pyramid and Demographic TransitionPopulation Pyramid and Demographic Transition• Stage 2: wide base

• stage 3: wide middle• stage 4: slender

• stage 5: narrow base

Population Pyramid and Demographic TransitionPopulation Pyramid and Demographic Transition• Stage 2: wide base

• stage 3: wide middle

• stage 4: slender• stage 5: narrow base

Population Pyramid and Demographic TransitionPopulation Pyramid and Demographic Transition• Stage 2: wide base

• stage 3: wide middle

• stage 4: slender

• stage 5: narrow base