Environmental Problems, Their Causes, and Sustainability 1

irth rates. As a result, more births are occurring thandeaths; every time your heart beats, 2.5 more babies areadded to the world’s population. At this rate, we sharethe earth and its resources with about 219,000 morepeople each day—97% of them in developing countries.The rate of the world’s annual population changeis usually expressed as a percentage:1.1 billion1.4 billionAnnual rate ofBirth rate Death rateBrazil 179 millionnatural population 100change (%)1,000 persons211 millionBirth rate Death ratePakistan 159 million 10 229 millionRussia 144 millionExponential population growth has not disappearedbut is occurring at a slower rate. The rate of theworld’s annual population growth (natural increase)dropped by almost half between 1963 and 2004, from2.2% to 1.25%. This is good news but during the sameperiod the population base doubled, from 3.2 billion to6.4 billion. This drop in the rate of population increaseis somewhat like learning that a truck heading straightBangladeshJapanNigeria137 million141 million205 million128 million121 million137 million206 millionat you has slowed from 100 kilometers per hour (kph)2004 2025to 55 kph while its weight has doubled.Figure 10-4 The world’s 10 most populous countries in 2004,An exponential growth rate of 1.25% may seemwith projections of their population size in 2025. In 2004, moresmall. But in 2004 it added about 80 million people topeople lived in China than in all of Europe, Russia, North America,the world’s population, compared to 69 million addedin 1963, when the world’s population growth reachedJapan, and Australia combined. (Data from World Bank andPopulation Reference Bureau)its peak. An increase of 80 million people per year isroughly equal to adding another New York City everyHow Long Does It Take to Double the Numbermonth, a Germany every year, and a United Statesof People on the Planet? The Rule of 70every 3.7 years.Also, there is a big difference between exponentialDoubling time is how long it takes for a populationpopulation growth rates in developed and developinggrowing at a specified rate to double its size.countries. In 2004, the population of developed countrieswas growing at a rate of 0.1%. That of the developingcountries was 1.5%—almost 15 times faster.As a result of these trends, the population of thedeveloped countries, currently at 1.2 billion, is expectedto change little in the next 50 years. In contrast,the population of the developing countries is projectedto rise steadily from 5.2 billion in 2004 to 8 billion in2050. The six nations expected to experience mostof this growth are, in order: India, China, Pakistan,Nigeria, Bangladesh, and Indonesia.What five countries have the largest numbers ofpeople? Number 1 is China with 1.3 billion people—One measure of population growth is doubling time:the time (usually in years) it takes for a populationgrowing at a specified rate to double its size. A quickway to calculate doubling time is to use the rule of 70:70/percentage growth rate doubling time in years(a formula derived from the basic mathematics of exponentialgrowth). For example, in 2004 the world’spopulation grew by 1.2%. If that rate continues, theearth’s population will double in about 56 years(70/1.25 56 years).The population of the African country of Nigeriais increasing by 2.8% a year. How long will it take forits population to double?about one of every five people in the world. Number 2is India with 1.1 billion people—about one of every sixHow Have Global Fertility Rates Changed?people. Together China and India—with roughly theHaving Fewer Babies per Womansame geographic areas—have 37% of the world’s population.Number 3 is the United States, with 294 millionpeople or 4.6% of the world’s population.has dropped sharply since 1950, but the number is notThe average number of children that a woman bearsCan you guess the next two most populous countries?What three countries are expected to have thenear future.low enough to stabilize the world’s population in themost people in 2025? Look at Figure 10-4 to see if youranswers are correct.Fertility is the number of births that occur to an individualwoman or in a population. Two types of fertilityChinaIndiaUSAIndonesia294 million349 million219 million308 million1.3 billion1.4 billion178 CHAPTER 10 Applying Population Ecology: The Human Population