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Lecture 4

EES 1080 Lecture 4: Chapter 8 Human Population

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University of Iowa
Earth & Environmental Sciences
EES 1080

Chapter 8 Human Population Case Study: China’s One Child Policy • In 1970, China’s 790 million people faced starvation • The government instituted a one-child policy o The growth rate plummeted o The policy is now less strict • The successful program has unintended consequences: o Killing of female infants o Black market trade in teenage girls One World at Seven Billion • Population continues to rise in most countries o Particularly in poverty-stricken developing nations • Although the rate of growth is slowing, we are still increasing the numbers • It would take 30 years counting once each second, to count to a billion! It would take 210 years to count to 7 billion The Human Population is Growing Rapidly • Population grows over 80 million each year • It took until 1800 to reach 1 billion • In 1930 (130 years later) we reached 2 billion • We added the most recent billion in 12 years • Due to exponential growth, even if the rate remains steady, population will continue to grow Rates of Growth Vary from Region to Region • At today’s 1.2% global growth rate, the population will double in 58 years (70/1.2=58) • If China’s rate had contained at 2.8%, it would had 2 billion people in 2004 Is Population Growth a Problem? • Technology, sanitation, medication, and increased food increase population o Death rates drop, but not birth rates • Population growth was seen as good o Support for elderly, a larger labor pool • Thomas Malthu’s An Essay on the Principles of Population (1798) o Humans will outstrip food supplies o War, disease, starvation reduce populations Paul Ehrlich’s Population Bomb (1968) • Neo Malthusians: population growth will increase faster than food production • Population growth causes famine and conflict o Civilization would end by the 20 century • Intensified food production fed more people Population Growth will Affect Quality of Life • PG has caused famine, disease, conflict • Prosperity, education, gender equality reduce birth rates • Cornucopians (economists) say new resources will replace depleted ones o But some resources (species) are irreplaceable • Quality of life will suffer with unchecked growth o Less space, food, wealth per person Some Governments Fear Falling Populations • Policymakers believe population increases economic, political, and military strength • But growth is correlated with poverty, not wealth o Strong, rich nations have low growth rates o Weak, poor nations have high growth rates • Some nations offer incentives for more children o Elderly need social services • 49% of non-European nations feel their birth rates are too high Population Growth Affects the Environment • The IPAT Model: I= P x A x T x S • Total impact (I) on the environment results from: o Population (P)= individuals need space and resources o Affluence (A)= greater per capita resource use o Technology (T)= increased exploitation of resources o Sensitivity (S)= how sensitive an area is to human pressure • Further model refinements include the effects of education, laws, and ethics on the formula Population Growth with Limited Resources • Impacts equates to pollution on resource consumption o Humans use 25% of the Earth’s net primary production • Technology has increased efficiency and reduced our strain on resources o Resulting in further population growth o For xample: increased agricultural production • Modern China’s increasing affluence is causing: o Increased resource competition o Farmland erosion, depleted aquifers, urban pollution • China shows us what the rest of the world can become Demography • Demography the application of population ecology to the study of change in human populations o All population principles apply to humans o Environmental factors limit population growth • Humans raise the environment’s carrying capacity through technology • How many humans can the world sustain? o 1-33 billion: prosperity to abject poverty o Population growth cannot continue forever • Demographers Study: o Population size o Density and distribution o Age structure o Sex ratio o Birth, death, immigration and emigration rates Population Size and Density • The UN predicts 9 billion by 2050 • Increased density impacts the environment o But relieves pressure in less-populated areas • Highest Density= Temperate, subtropical, tropical biomes o Cities • Lowest Density= Away from water Population Distribution • Uneven distribution of humans around the globe • Unpopulated areas tend to be environmentally sensitive (high S value in the IPAT equation) o Vulnerable to humans (e.g. desserts, arid grasslands) Age Structure Affects Population Size • Age structure diagrams (population pyramids) show age structure • Wide base= many young: o High reproduction o Rapid population growth • Even age distribution: o Remain stable o Births= Deaths Age Structure: Canada vs. Madagascar • Canada’s age structure is balanced • Madagascar’s age structure is heavily weighted toward the young Changing Age Structures Pose Challenges • China’s age structure is changing o In 1970, median age was 20 o By 2050, it will be 45 • By 2050, over 300 million will be over 65 o Fewer people will be working to support social programs Many Populations are Aging • Many populations are getting older o They will need care and financial assistance o Taxes will increase for SS and Medicare • But fewer dependent children means lower crime rates • The elderly can remain productive Sex Ratios • Human sex ratios at birth slightly favor males o For every 100 females born, 106 males are born • Chinese families are selectively aborted o 120 boys were reported for 100 girls o Cultural gender preferences o The government’s one-child policy • The undesirable social consequences? o Many single Chinese men o Teenage girls are kidnapped and sold as brides Factors in Population Change • Whether a population grows, shrinks, or remains stable depends on the birth, death and migration rates o Birth and immigration add people o Death and emigration remove people • Technological advances caused decreased rates o The increased gap between birth and death rates resulted in population expansion • Natural Rate of Population Change due to birth and death rates alone Immigration and Emigration • War, civil, strife, and environmental degradation cause people to flee their homes o Each year, 25 million refugees escape poor environmental conditions • This movement causes environmental problems o No incentives to conserve resources Falling Growth Rates do not mean Fewer People • Slower rates of growth do not mean a decreasing population—population size continues to increase Factors Affecting Total Fertility Rate • Total Fertility Rate (TFR) the average # of children born to each female • Replacement Fertility the TFR that keeps the size of the population stable (about 2.1) • Causes of decreasing TFR: o Medical care reduces infant mortality o Urbanization increased childcare costs o Children go to school instead of working o SS supports the elderly o Educated women enter the labor force Life Expectancy is Increasing • In countries with good sanitation, health care, and food, people live longer • Life Expectancy a
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