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Human Population Growth. Factors Affecting Human Population Size. Births Deaths Migrations Immigration: individuals moving into a pop. Emigration: individuals moving out of a pop. Population Change= (births+immigration)-(deaths+emigration)
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Factors Affecting Human Population Size • Births • Deaths • Migrations • Immigration: individuals moving into a pop. • Emigration: individuals moving out of a pop. • Population Change= (births+immigration)-(deaths+emigration) **When births and immigration is greater than deaths and emigration, the population will increase http://www.youtube.com/watch?v=4BbkQiQyaYc
World Population • Rate of annual pop change is expressed as a percentage: birth rate-death rate 10 • Exponential growth has not disappeared, but its occurring at a slower rate • Between 1963 and 2002, the population rose from 3.2 to 6.2 billion • 79 million people were added in 2002, compared to 69 million in 1963 when the world’s pop growth rate was at its highest
Fertility Rates • Replacement Level Fertility- # of children that a couple needs to have in order to replace themselves (2.1 in developed countries/2.5 in developing countries) • Total Fertility Rate (TFR)-an estimate of the # of children a woman will have during childbearing years (based on the previous year)
United States Historical Trend in Total Fertility Rate • 1910-1930: birth rates dropped due to urbanization • 1930’s: stayed low because of the Great Depression • 1940’s: rising again • 1957: TFR=3.7 children/woman, highest • 1946-1964: Baby Boom • 1965-1977: Baby Bust • 1977-2000: Echo Boom
Factors that Affect Average Birth Rate and TFR • Children are part of the labor force- • Urbanization- • High cost of raising and education children- • High infant mortality rate- • Older average age of marriage-
Factors that Affect Average Birth Rate and TFR • High availability of pension systems- • Availability of legal abortions- • Availability of birth control- • Men included in child-rearing responsibilites- • Religious beliefs, traditions, cultural norms
Factors That Decrease Death Rates • Increased food supply and distribution • Better nutrition • Medical improvements • Increased sanitation** • Better water supply
Two Indicators of Overall Health • Life expectancy: average # of years people live • Global life expectancy: 76 in developed nations/65 in developing nations • US: 77 yrs. • Africa: 55 Yrs. • Infant Mortality Rate: # of babies out of 1000 that die before their first birthday • High infant mortality rate indicates insufficient food, poor nutrition, high incidence of infectious disease (water supply)
Population Age Structure • The proportion of the pop of each sex at each age level; used to make pop and economic projections • Age levels: • Prereproductive (0-14) • Reproductive (15-44) • Post reproductive (45 and up) • Age structure affects population growth • Countries with a wide base (lots of people below 15) will increase in size if death rate stays the same
Population Study-Example • Social security crisis
Populations Affected by Immigration • U.S. • Canada • Australia
Cultural Carrying Capacity • Different from actual # of individuals an area can support b/c of culture; when land is used to grow feed for cattle it expends more energy thus reducing carrying capacity • Eating high on the food chain uses up to 50x more land than eating a vegetarian diet • 43% of U.S. is used for grazing or feed for livestock; meat’s impact on the environment is second only to automobiles
Demographic Transition • Demography: study of human population • As countries become industrialized first death rates, but then birth rates decline • Four Stages • Preindustrial Stage • Tansitional Stage • Industrial Stage • Postindustrial Stage
Preindustrial Stage • Little population growth because of harsh conditions • High birth AND death rates
Transitional Stage • Population grows rapidly when industrialization improves • High birth rates, lowering death rates • Stage that developing nations are in currently
Industrial Stage • Population growth slows as birth rates drop and eventually approach death rates
Postindustrial Stage • Birth rate=death rate • Zero population growth • European countries
India • 1.1 billion people • 16% of world’s people, but only 2.3% of world’s land resources and 2% of world’s forests • 70% of water seriously polluted • Tried family planning, but not very successful • Why?
China • 1.3 billion people • Since 1970, cut its crude birth rate in half and decreased TFR from 5.7 to 1.8 children/woman • How? • Free sterilizations/contraception/abortions • Couples who have only one child receive: extra food, larger pensions, better housing, free medical care, salary bonuses, free school tuition for their child, and preferential treatment in employment when their child enters the work force
China • Projected that China’s pop will begin to decline in 2042, but what about their aging population/social security? • Should other countries impose such severe restrictions/limitations on human freedoms to achieve pop control?
Cutting Global Population Growth • Provide access to family planning services and reproductive health care • Improve health care of infants, children, pregnant women • Implement population policies • Improve job opportunities for women • Increase access to education, especially to women • Increase involvement of men in child-rearing • Eradicate poverty • Reduce/eliminate unsustainable patterns of production and consumption
Cutting Global Population Growth • Goal of Cairo Commitment: stabilize pop growth at 7.8 billion by 2050 instead of projected 9-11 billion • BTW we are already at 6.7 billion….. • World Clock