Population Ecology

Population Ecology - Population 6.6 billion(2006 9.2...

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Population: 6.6 billion (2006) 9.2 billion (2050) Most growth in developing countries (India and China) Too many people degrades Earth’s natural capital Past Population Growth 3 reasons for rapid exponential growth (J-curve) o 1. Humans have adapted and can now live in new diverse habitats an different climate zones o 2. Agriculture allows more people to be fed o 3. We’ve developed sanitation systems and treatments for disease and tapped into concentrated energy sources Today’s Population Growth Growth rate 1.23% per year (15 times faster in developing countries) 81 million more people/year No population can continue to grow indefinitely Birth Rates and Death Rates Human populations grow or decline due to: births (fertility), deaths (mortality), and migration Population Change = (Births + Immigration) – (Deaths + Emigration) Population experts (demographers) use the crude birth rate (the number of live births per 1,000 people in a population in a given year) Crude death rate (number of deaths per 1,000 people in a population in a given year) Fertility (number of children a woman has) Two types of fertility rates: o Replacement-level fertility : a number of children a couple must have to replace themselves (2). Usually more (2.1 in developed and 2.5 in developing) o Total fertility rate (TFR): the average number of children a woman has . (1.6 in developed and 2.9 in developing with a 2.5 global average) U.S. Fertility and Birth Rates 1946-1964 is Baby-boom period (added 79 million people, TFR was 3.9). Baby- boomers make up nearly half of all adult U.S. residents Baby bust : delayed marriages, widespread contraceptive use, and abortion Growth rate greater than any other developed country Factors affecting Birth Rates and Fertility Importance of children as a part of the labor force Cost of raising and educating children Availability of public and private pension systems (pensions reduce the need of couples to have many children to support them when they are old) Urbanization (Urban areas make contraceptives easier to obtain and in rural areas, children are needed for labor) Educational and employment opportunities available for women (if women work and go to school they have less time to have and raise kids)
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Infant mortality rate (if rate is high, they have more kids b/c they expect to lose some) Average age at marriage (women have less kids if married at 25 or older) Availability of legal abortions (190 million women get pregnant each year. 46
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Population Ecology - Population 6.6 billion(2006 9.2...

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