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Basic concepts and human history Human Population Growth.

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Presentation on theme: "Basic concepts and human history Human Population Growth."— Presentation transcript:

1 Basic concepts and human history Human Population Growth

2 Human population has recently exploded in size Note large increase in late 20 th century

3 Homo sapiens sapiens (modern humans) around 90,000 years old Human ancestor numbers regulated by the environment like any other organism Changes in society cause changes in population Human evolution

4 Hunter-gatherers Small nomadic populations Short life expectancy (30-40 yrs.) LOW ENVIRON. IMPACTS Small numbers Frequent movements

5 Began 10,000 - 12,000 y.a. in the Middle East Fundamentally alters human civilization Agricultural revolution

6 Ample food available Craftsmen and artisans arise Class distinctions Frees individuals from daily food gathering Societal effects Better survival rates

7 Permanent settlements arise... Architecture improves... Agricultural revolution...CITIES ARE BORN

8 POPULATION DENSITY: Populations remain in one location Ample food = population growth ENVIRONMENTAL IMPACTS: Increased human populations stress local environment PEOPLE IN CITIES NEED: Fields for farming & grazing, water, wood, clay, minerals, etc. This changes everything...

9 Menderes Valley in modern Turkey Erosion in river valley Overgrazing Over-farming Deforestation Delta into Aegean grows over time

10 Begins in Europe in early 18th century CHANGES Agriculture Production Transportation Industrial revolution SOCIETY

11 STEAM POWER: Coal-fired Replaces water power Factories need not be near water Powers factories, railroads, sea travel Industrial revolution

12 AGRICULTURE: Crop rotation - reduced fallow time END RESULT: More food from less land with less labor Plowing and seeding techniques improved Root crops popularized Late 1800's inorganic fertilizer produced Mechanized farming and processing Industrial revolution

13 SOCIAL CONSEQUENCES: Urbanization of population Plentiful food Medicine and sanitation reduce mortality END RESULT: Populations rise rapidly Mass production improves quality of life Industrial revolution

14 Numbers of humans Time Tool-making revolution Agricultural revolution Industrial – Scientific revolution Each of these revolutions raised the carrying capacity for humans Revolutions and pop. growth

15 Time Number Population grows slowly... …then rapidly... …eventually leveling off at the carrying capacity CARRYING CAPACITY Maximum no. of a species the environment can support A highly simplified and somewhat unrealistic growth model Population growth curve

16 Note the human population is still in the rapid growth phase Figure 3.12

17 THE BIG QUESTION: Where will the human population level off?

18 How many humans can the earth support? QUESTION: Assumes: All open flat land cultivated Purely vegetarian diet People live underground Assumes: Current food production Typical American diet 50 billion2.5 billion  World grain production leveling off Population continues to increase Per-capita grain production necessarily declines Human carrying capacity Environmental impact starting to cause problems

19 BIRTH RATE: Births per unit time divided by population size b = B/N b = birth rate B = number of births per unit time N = total population size DEATH RATE: Deaths per unit time divided by population size d = death rate D = number of deaths per unit time N = total population size d = D/N GROWTH RATE: Rate of population change g = (B - D)/N Variables as above Calculating growth rate

20 Population of Australia in 1998 (N) = 18,700,000 Births from 1998-1999 (B) = 261,500 Deaths from 1998-1999 (D) = 130,900 BIRTH RATE: b = B/N b = 261,000/18,700,000 b = 0.014 b = 1.4% d = D/N DEATH RATE: d = 130,900/18,700,000 d = 0.7% GROWTH RATE: g = (B - D)/N g = (261,800 - 130,900)/18,700,000 g = 0.7% AN EXAMPLE:

21 Figure 5.5 Time it takes population size to double Varies depending on growth rate Roughly equal to 70  growth rate Even g =1% will double global population in your lifetime DOUBLING TIME

22 Pop size time 2 = Pop size time 1 + (Pop size time 1 * growth rate time1 ) N 2 = N 1 *(1+ g 1 ) Using the previous example: Population of Australia in 1998 (N 1 ) = 18,700,000 Population of Australia in 1999 (N 2 ) = ? Growth rate of Australia in 1998 (g 1 ) = 0.7% or 0.007 N 2 = 18,700,000 *(1.000 + 0.007) N 2 = 18,700,000 + 130,900 N 2 = 18,830,900 POPULATION GROWTH:

23 N 2 = N 1 *(1 + g 1 ) Population increase affected by population size and growth rate Therefore: Large population = rapid increase High growth rate = rapid increase China = 1,220,000,000 people x 1% growth = +12,200,000 per yr Japan = 126,000,000 people x 1% growth = + 1,260,000 per yr Population size Japan =126,000,000 people x 1% growth = + 1,260,000 per yr Japan =126,000,000 people x 10% growth = + 12,600,000 per yr Growth rate FACTORS AFFECTING POPULATION GROWTH

24 The two worlds DEVELOPED COUNTRIES: High Gross National Product High per-capita GNP STATS: 21% of global pop. Holds 85% of global wealth Use 88% of global resources Generate 75% of global pollution

25 DEVELOPING COUNTRIES: Low Gross National Product Very low per-capita GNP STATS: 79% of global pop. Holds 15% of global wealth Little industrialization The two worlds

26 1 in 5 people live in luxury 3 in 5 people "get by" 1 in 5 people live in dire poverty How is the distribution of wealth changing? Trends in global wealth

27 Population x Affluence x Technology = Impact Number of people number of resource “units” used per person Environmental impact per resource unit used THE FORMULA: P x A x T = Environ. Impact A differs in developed and developing countries T  by some technology (e.g., burning coal) T  by some technology (e.g., solar power) Calculating environ. impacts

28 P x A x T = Environ. Impact Number of people number of resource “units” used per person Env. impact per resource unit used Env. impact of population = = x xx x Developed nations Developing nations Magnitude = width of circle

29 Figure 5.3 Where are populations increasing?

30 Figure 5.3c Geography and growth

31 Figure 5.9 Age structure diagrams

32 Growth rate = births - deaths Growth increased by  births or  deaths So which caused the recent increase in population? Rapid increases in population in 20th century Population increases

33 Natural rate of increase Birth rate-death rate Both rates decline in 20 th century Rate of increase stable Developed countries

34 Natural rate of increase Death rates decline sharply Birth rates do not follow Rate of increase skyrockets Developing countries

35 Why the drop in death rates? Improvements in sanitation reduce incidence of disease Industrialized agriculture gives higher yields, better nutrition Antibiotics and better medicine reduce death rates

36 Figure 5.8

37 FACTORS THAT AFFECT FERTILITY RATES: Education and affluence Urbanization Cost of children State pensions Availability to birth control Infant mortality Women's age at marriage Female education and employment Importance of child labor How will each of these factors affect birth rates? What influences birth rates?

38 REPLACEMENT LEVEL FERTILITY: No. of kids per couple to replace themselves in the population Developed = 2.1 and Developing = 2.6 in 1996 TOTAL FERTILITY RATE: Estimate of the no. of children a woman has in her lifetime Developed = 1.6 and Developing = 3.4 in 1996 Global average = 3.0 "Magic number" = 2.1 Measuring fertility rates

39 Figure 5.11

40 Figure 5.6

41 Get global TFR  2.1 for zero population growth (ZPG) THE GOAL: METHODS: Affluence and industrialization Increased access to birth control Increased opportunities for women Economic incentives to reduce family size Slowing population growth

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