<p>This lecture will help you understand: • Human population growth • How human population, affluence, and technology affect the environment • Demography • Demographic transition • How wealth, poverty, and status of women affect population growth • Dimensions of HIV/AIDS Central Case: China’s One-Child Policy • Unfettered population growth posed challenges for China’s environment, economy, and political stability. • China tried to control its growth with a system of rewards and punishments to encourage one-child families. • The program decreased population growth, but meant government intrusion in private reproductive choices. “Baby Six Billion” The world’s population now exceeds 6 billion people.</p><p>The UN marked this symbolically by declaring a child born in 1999 in war- torn Sarajevo as the six-billionth baby. World population has risen sharply • Global human population was < 1 billion in 1800. • Population has doubled just since 1964. • We add 2.5 people every second (78 million/year). Population growth rates, 1990–1995 • Growth rates vary from place to place. • Growth peaked at 2.1% in the 1960s; it has now declined to 1.2%. Is population growth really a problem? Some say NO:</p><p>• People can find or manufacture additional resources to keep pace with population growth. • Nations become stronger as their populations grow. Some say YES:</p><p>• Not all resources can be replaced. • Even if they could, quality of life suffers. • Nations do not become stronger as their populations grow. The “IPAT” model Shows how Population, Affluence, and Technology interact to create Impact on our environment.</p><p>I = P  A  T</p><p>Further factors can be added to the original equation of Holdren and Ehrlich to make it more comprehensive. Modeling population and its consequences Some models show population growth leading to resource depletion, which can result in declining food production, industrial output, and population. Increasing our carrying capacity Technology has allowed us to raise Earth’s carrying capacity for our species time and again. Tool-making, agriculture, and industrialization each enabled humans to sustain greater populations. Demography Demography = the study of human populations</p><p>Human populations exhibit the same fundamental characteristics as do populations of all other organisms. Population size: National populations Nations vary from China’s 1.3 billion down to Pacific island nations of 100,000. Shown are the 15 most populous countries, and selected others; 2005 data. Population size: Future projections Demographers project population growth trends to estimate future population sizes. Different fertility rate scenarios predict global population sizes in 2050 of 7.7 billion, 9.1 billion, or 10.6 billion. All these projections assume fertility rates below today’s; at today’s rate, the population would reach 11.7 billion. Population density and distribution Humans are unevenly distributed, living at different densities from region to region. Age structure: Age pyramids Canada (a) shows a balanced age structure, while Madagascar’s population growth (b) is 9 times faster. Age structure: “Graying populations” Demographers project that China’s population will become older over the next two decades. Age structure: “Graying populations” China’s aging population will mean fewer working-age citizens to finance social services for retirees. Age structure: “Baby booms” The United States’ “baby boom” is evident in age bracket 40–50. U.S. age structure will change as baby boomers grow older. Sex ratios A population’s sex ratio can affect its growth rate. The naturally occurring sex ratio in humans is 105 to 106 males for every 100 females. This may be an evolutionary adaptation as males are slightly more prone to death at any given age. The ratio of men to women is therefore approximately equal at reproductive age. Factors affecting population growth rates Population growth depends on rates of birth, death, immigration, and emigration.</p><p>(birth rate + immigration rate) – (death rate + emigration rate) = population growth rate Migration can have environmental effects Immigration and emigration play large roles today. Refugees from the 1994 Rwandan genocide endured great hardship, and deforested large areas near refugee camps. China’s natural rate of change has fallen China’s rate has fallen with fertility rates. It now takes the population 4 times as long to double as it did 25 years ago. Global growth rates have fallen The annual growth rate of the world population has declined since the 1960s.</p><p>(But the population size is still rising!) Fertility rates affect population growth rates Total fertility rate (TFR) = average number of children born per woman during her lifetime</p><p>Replacement fertility = the TFR that keeps population size stable</p><p>For humans, replacement fertility is about 2.1. Total fertility rates by region African nations have the highest TFRs. European nations have the lowest TFRs. Natural rate of population change Change due to birth and death rates alone, excluding migration.</p><p>It is often expressed in % per year. Demographic transition theory Demographic transition = model of economic and cultural change to explain declining death rates, declining birth rates, and rising life expectancies in Western nations as they became industrialized.</p><p>Proposed by Frank Notestein in the 1940s–1950s Demographic transition: Stages The demographic transition consists of several stages: Pre-industrial stage: high death rates and high birth rates. Transitional stage: death rates fall due to rising food production and better medical care. Birth rates remain high, so population surges. Demographic transition: Stages, continued Industrial stage: birth rates fall, as women are employed and as children become less economically useful in an urban setting. Population growth rate declines. Post-industrial stage: birth and death rates remain low and stable. Society enjoys fruits of industrialization without threat of runaway population growth.</p><p>Demographic transition: Stages TFR decline in Bangladesh Bangladesh reduced TFR from 7.1 to 4.6 in 25 years, and is at 3.0 today. Family planning, education, and outreach were responsible. Female education and TFR Female literacy and school enrollment are correlated with total fertility rate.</p><p>More-educated women have fewer children. Poverty is correlated with population growth Poorer countries will experience most future population growth 98% of the next billion people born will live in developing nations. Population and the environment Population growth can lead to environmental degradation.</p><p>Overpopulation in Africa’s Sahel region has led to overgrazing of semi-arid lands. Affluence and the environment Poverty can lead to environmental degradation…</p><p>BUT </p><p> wealth and resource consumption can produce even more severe and far- reaching environmental impacts. The ecological footprint The cumulative amount of Earth’s surface area required to provide the raw materials a person or a population consumes, and then to dispose of or recycle the waste that is produced. Global ecological footprint Scientists have calculated the global ecological footprint now exceeds what the Earth can bear in the long run. The wealth gap Residents of developed nations have larger houses, more possessions, and more money than residents of developing nations.</p><p>The richest 20% of the world’s people consumes 86% of its resources, and has > 80 times the income of the poorest 20%. Demographic fatigue and demographic transition Many governments of developing countries are experiencing “demographic fatigue,” unable to meet the social, economic, and environmental challenges imposed by rapid population growth.</p><p>This raises the question: Will today’s developing countries successfully pass through the demographic transition? Conclusion The human population is larger than at any time in the past. 90% of children born today are likely to live in conditions far less healthy and prosperous than those in the industrialized world. The rate of growth has decreased nearly everywhere, and some countries are seeing population declines. Most developed nations have passed through the demographic transition and are in position to transition to ecologically sustainable economies. Conclusion Many developing nations are making their way through the demographic transition, and equitable treatment is vital to their success. Women’s rights are expanding worldwide, which helps slow population growth.</p>