ENSP101 Chapter 7 Human Populations 7 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 depend o These fears often lead to demands for worldwide birth control programs to reduce fertility what to do Others believe that human ingenuity technology and enterprise can extend the world carrying capacity and allow us to overcome any problems we encounter o A larger population means a larger workforce more geniuses more ideas about o Alone with every new mouth comes a pair of hands Another perspective derives from social justice concerns o The root causes of environmental degradation in this view is inequitable distribution of wealth and power rather than population size o 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 recently o Human populations began to increase rapidly after A D 1600 o It took all of human history to reach 1 billion people in 1804 but little more than 150 years to reach 3 billion in 1960 o To go from 5 to 6 billion took only 12 years 7 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 degradation o 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 ago o Much of our growth and rising standard of living in the past 200 years however has been based on easily acquired natural resources especially cheap abundant fossil fuels o 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 benefits o More people means lager markets more workers and efficiencies of scale in mass production of goods o Moreover adding people boosts human ingenuity and intelligence that will create new resources by finding new materials and discovering new ways of doing things 7 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 rapidly o 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 growth o 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 low o 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 fertility o 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 the past 50 years o 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 rate o Countries in Africa where health care and sanitation are limited may have mortality rates of 20 or more per 1 000 people o 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 emigration o 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 society o 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 their dependency ratio or the number of nonworking compared to working individuals in a population o By 2050 the UN predicts there will be 2 older persons for every child in the world Emigration and immigration are important demographic factors 7 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 fertility o Higher education and personal freedom for women often result in decisions to limit o The desire to have children is offset by a desire for other goods and activities that compete with childbearing and childbearing for time and money o Thus education and socioeconomic status are usually inversely related to fertility in childbearing richer countries There are concerns about falling military strength lack of soldiers economic power lack of workers and declining social systems not enough workers and taxpayers if low birth