Environmental Problems, Their Causes, and Sustainability 1

The problems to be faced are vast and complex, but comedown to this: 6.4 billion people are breeding exponentially.The process of fulfilling their wants and needs is strippingearth of its biotic capacity to produce life; a climactic burst ofconsumption by a single species is overwhelming the skies,earth, waters, and fauna.PAUL HAWKENThis chapter addresses the following questions:■■■■■How is population size affected by birth, death,fertility, and migration rates?How is population size affected by age structure?How can we influence population size?What success have India and China had in slowingpopulation growth?How can global population growth be reduced?10-1 FACTORS AFFECTING HUMANPOPULATION SIZEWhat Is Demography and Why Is itImportant? How Population Change AffectsLife, Death, and EconomiesChanges in the size, composition, and distribution ofhuman populations have important health, social, andeconomic effects.How long are you likely to live and what will probablykill you? How many people are there in the country orarea where you live and how many people are likely tolive there in the future? How many children are youlikely to have? How likely are you to get married or divorced?What kind of job will you probably have andhow many times are you likely to change jobs? Whatare your chances of promotion? When are you likely toretire? About how many times will you move?Demography is devoted to finding answers tothese and other population-related questions. Demographyis the study of the size, composition, and distributionof human populations and the causes andconsequences of changes in these characteristics. Specialistsin this field are called demographers.How Is Population Size Affectedby Birth Rates and Death Rates? Entrancesand ExitsPopulation increases because of births andimmigration, and decreases through deaths andemigration.Human populations grow or decline through the interplayof three factors: births, deaths, and migration. Populationchange is calculated by subtracting the numberof people leaving a population (through death andAverage crude birth rateWorldAll developed11countries 10All developingcountries 8Developingcountries(w/o China)AfricaLatinAmerica 6AsiaOceania9914United14States 8North14America 8Europe101277Average crude death rateFigure 10-3 Average crude birth and death rates for variousgroupings of countries in 2004. (Data from Population ReferenceBureau)emigration) from the number entering it (throughbirth and immigration) during a specified period oftime (usually a year):Population change (Births Immigration) (Deaths Emigration)When births plus immigration exceed deaths plusemigration, population increases; when the reverse istrue, population declines.Instead of using the total numbers of births anddeaths per year, demographers use the birth rate, orcrude birth rate (the number of live births per 1,000people in a population in a given year), and the deathrate, or crude death rate (the number of deaths per1,000 people in a population in a given year). Figure10-3 shows the crude birth and death rates for variousgroupings of countries in 2004.How Fast Is the World’s PopulationGrowing? Good and Bad NewsThe rate at which the world’s population increaseshas slowed, but the population is still growing fairlyrapidly.Birth rates and death rates are coming down worldwide,but death rates have fallen more sharply than18212022242738http://biology.brookscole.com/miller14177