ENSP101Chapter 7 – Human Populations7.1 Population Growth- A net gain of roughly 2.3 more humans per second in the world’s population- Many people worry that overpopulation will cause resource depletion and environmental degradation that threaten the ecological life-support systems on which we all dependo These fears often lead to demands for worldwide birth control programs to reduce fertility- Others believe that human ingenuity, technology, and enterprise can extend the world carrying capacity and allow us to overcome any problems we encountero A larger population means a larger workforce, more geniuses, more ideas about what to doo Alone with every new mouth comes a pair of hands- Another perspective derives from social justice concernso The root causes of environmental degradation in this view, is inequitable distribution of wealth and power rather than population sizeo A narrow focus on population growth only fosters racism and an attitude that blames the poor for their problems while ignoring the deeper social and economic forces at work- Human populations grew slowly until relatively recentlyo Human populations began to increase rapidly after A.D. 1600o It took all of human history to reach 1 billion people in 1804, but little more than 150 years to reach 3 billion in 1960o To go from 5 to 6 billion took only 12 years7.2 Perspectives on Population Growth- Malthus’ view: Excess population growth  Resource depletion/Pollution/Overcrowding/Unemployment (which lead to poverty)  Starvation/Disease/Crime/Misery  War- Marx’s view: Exploitation/Oppression  Poverty  Resource depletion/Pollution/Overcrowding/Unemployment  Excess population growth OR Starvation/Disease/Crime/Misery  War- Some believe that population growth is the ultimate cause of poverty and environmental degradationo Others argue that poverty, environmental degradation, and overpopulation are all merely symptoms of deeper social and political factors- Progress in agricultural productivity, engineering, information technology, commerce, medicine, sanitation, and other achievements of modern life have made it possible to support thousands of times as many people per unit area as was possible 10,000 years agoo Much of our growth and rising standard of living in the past 200 years, however, hasbeen based on easily acquired natural resources, especially cheap, abundant fossil fuelso I = PAT formula – a formula that says our environmental impacts (I) are the product of our population size (P) times affluence (AS) and the technology (T) used to produce the goods and services we consume- Population growth could bring benefitso More people means lager markets, more workers, and efficiencies of scale in mass production of goodso Moreover, adding people boosts human ingenuity and intelligence that will create new resources by finding new materials and discovering new ways of doing things7.3 Many Factors Determine Population Growth- Demography – vital statistics about people; the statistical study of human populations relating to growth rate, age structure, geographic distribution, etc, and their effect on social, economic, and environmental conditions- We really live in 2 very different demographic worlds: one is old, rich, and relatively stable. The other is young, poor, and growing rapidlyo Most people in Asia, Africa, and Latin America inhabit the latter demographic world These countries represent 80% of the world population but more than 90% of all projected growtho The highest population growth rates occur in a few “hot spots,” such as sub-Saharan Africa and the Middle East, where economics, politics, religion, and civil unrest keep birth rates high and contraceptives use lowo The other demographic world is made up of the richer countries of north America, western Europe, Japan, Australia, and New Zealand This world is wealthy, old, and mostly shrinking- Crude birth rate – the number of births in a year divided by the midyear population- Total fertility rate – the number of children born to an average woman in a population during her entire reproductive life- Zero population growth (ZPG) –the number of births at which people are just replacing themselves; also called the replacement level of fertilityo It takes several generations of replacement level fertility (where people just replace themselves) to reach ZPG- Fertility rates have declined dramatically in every region of the world except Africa over thepast 50 yearso China’s one-child-per family policy- Crude death rate – the number of deaths per thousand persons in a given year; also called crude mortality rateo Countries in Africa where health care and sanitation are limited may have mortality rates of 20 or more per 1,000 peopleo Wealthier countries generally have mortality rates around 10 per 1,000- Crude death rate subtracted from crude birth rate gives the natural increase of a population- Total growth rate – the net rate of population growth resulting from births, deaths, immigration, and emigrationo The world growth rate is now 1.14%, which means that the population will double in about 61 years if this rate persists- Life span – the oldest age to which a species is known to survive- Life expectancy – the average age that a newborn infant can expect to attain in any given societyo It’s another way of expressing the average age at death- Declining mortality, not rising fertility, is the primary cause of most population growth in the past 300 years- Women almost always have higher life expectancies than men- Both rapidly growing countries and slowly growing countries can have a problem with theirdependency ratio, or the number of nonworking compared to working individuals in a populationo By 2050, the UN predicts there will be 2 older persons for every child in the world- Emigration and immigration are important demographic factors7.4 Ideal Family Size is Culturally and Economically Dependent- Pro-natalist pressures – influences that encourage people to have children- In more highly developed countries, many pressures tend to reduce fertilityo Higher education and personal freedom for women often result in decisions to limit childbearingo The desire to have children is offset by a desire for other goods and activities that compete with childbearing and childbearing for time and moneyo Thus, education and socioeconomic status are usually inversely related to fertility inricher countries- There are