Chapter 9 Chapter 9 The Human The Human PopulationPopulation

ObjectivesObjectives

DescribeDescribe how the size and growth rate of how the size and growth rate of the human population has changed in the the human population has changed in the last 200 years.last 200 years.

DefineDefine four properties that scientists use four properties that scientists use to predict population sizes.to predict population sizes.

MakeMake predictions about population trends predictions about population trends based on age structure.based on age structure.

ExplainExplain why different countries may be at why different countries may be at different stages of the demographic different stages of the demographic transition.transition.

Studying Human Studying Human PopulationsPopulations DemographyDemography is the study of the is the study of the

characteristics of populations, characteristics of populations, especially human populations.especially human populations.

Studying Human Studying Human PopulationsPopulations

Countries with similar population trends are Countries with similar population trends are often grouped into two general categories: often grouped into two general categories: developed and developing countries.developed and developing countries.

Developed countries Developed countries – higher average incomes, slower population higher average incomes, slower population

growth, diverse industrial economies, & stronger growth, diverse industrial economies, & stronger social support systemssocial support systems

Developing countries Developing countries – lower average incomes, simple & agriculture-lower average incomes, simple & agriculture-

based economics, & rapid population growthbased economics, & rapid population growth

The Human Population Over The Human Population Over TimeTime

Exponential growth in the 1800s Exponential growth in the 1800s (population growth rates increased (population growth rates increased during each decade)during each decade)

Mostly due to decreased death ratesMostly due to decreased death rates– increases in food productionincreases in food production– clean waterclean water– improvements in hygiene improvements in hygiene – safe sewage disposalsafe sewage disposal– discovery of vaccinesdiscovery of vaccines

World Population Over TimeWorld Population Over Time

Age StructureAge Structure CClassification of members of a population into lassification of members of a population into

groups by age or distribution of members of a groups by age or distribution of members of a population in terms of age groupspopulation in terms of age groups

Helps make predictionsHelps make predictions Countries with high rates of growth usually have Countries with high rates of growth usually have

more more young peopleyoung people. Countries that have slow or no . Countries that have slow or no growth usually have an even distribution of ages in growth usually have an even distribution of ages in the population. the population.

Graphed in a population pyramidGraphed in a population pyramid

SurvivorshipSurvivorship %% of newborns in a of newborns in a

population that can be population that can be expected to survive to expected to survive to a given agea given age

Used to predict Used to predict population trendspopulation trends

To predict To predict survivorship, survivorship, demographers study a demographers study a group of people born group of people born at the same time & at the same time & notes when each notes when each member of the group member of the group dies.dies.

SurvivorshipSurvivorship Type I=most people live to be very oldType I=most people live to be very old

– Wealthy developed countries like Japan & Wealthy developed countries like Japan & GermanyGermany

Type II=populations have a similar death Type II=populations have a similar death rate at all agesrate at all ages

Type III=many children dieType III=many children die– Very poor, underdeveloped countriesVery poor, underdeveloped countries

Type I & Type III may result in populations Type I & Type III may result in populations that remain the same size or grow slowly.that remain the same size or grow slowly.

Fertility RateFertility Rate The number of The number of birthsbirths (usually per year) per 1,000 (usually per year) per 1,000

women of childbearing age (usually 15 to 44)women of childbearing age (usually 15 to 44) Replacement levelReplacement level is the average number of is the average number of

children each parent must have in order to children each parent must have in order to ““replacereplace”” themselves. This number is slightly themselves. This number is slightly more than 2 because not all children born will more than 2 because not all children born will survive & reproduce.survive & reproduce.

MigrationMigration AAny movement of individuals or ny movement of individuals or

populations from one location to anotherpopulations from one location to another Movement Movement INTOINTO an area= an area=IImmigrationmmigration Movement Movement OUTOUT of an area= of an area=EEmigrationmigration

((EExit)xit)

Life ExpectancyLife Expectancy Average length of time that an individual is Average length of time that an individual is

expected to liveexpected to live– Most affected by infant mortalityMost affected by infant mortality

Expensive medical care is not needed to prevent Expensive medical care is not needed to prevent infant deaths. Infant health is more affected by infant deaths. Infant health is more affected by the parentsthe parents’’ access to education, food, fuel, and access to education, food, fuel, and clean water.clean water.

The Demographic TransitionThe Demographic Transition

The general pattern of demographic The general pattern of demographic change from high birth & death rates change from high birth & death rates to low birth & death rates, & to low birth & death rates, & observed in the history of more-observed in the history of more-developed countriesdeveloped countries– Industrial development causes economic Industrial development causes economic

& social progress that then affects & social progress that then affects population growth ratespopulation growth rates

Stages of the TransitionStages of the Transition First StageFirst Stage

– A society is in a A society is in a preindustrial preindustrial condition condition

– The The birth & death birth & death ratesrates are both at are both at high levels high levels

– Population size is Population size is stablestable

Second StageSecond Stage – A population A population

explosion occurs explosion occurs – Death ratesDeath rates decline decline

as hygiene, as hygiene, nutrition, & nutrition, & education improve. education improve.

– Birth ratesBirth rates remain remain highhigh

Stages of the TransitionStages of the Transition Third StageThird Stage

– Population growth slows Population growth slows because birth rate because birth rate decreasesdecreases

– Population size Population size stabilizes, but the stabilizes, but the population is much population is much larger than before the larger than before the demographic transitiondemographic transition

Fourth StageFourth Stage– Birth rate drops below Birth rate drops below

replacement levelreplacement level– Population begins to Population begins to

decreasedecrease It has taken from 1-3 It has taken from 1-3

generations for the generations for the demographic transition to demographic transition to occur.occur.

Women and FertilityWomen and Fertility The factors most clearly related to a decline in The factors most clearly related to a decline in

birth rates are increasing education & economic birth rates are increasing education & economic independence for women.independence for women.– In the demographic transition model, the lower death In the demographic transition model, the lower death

rate of the second stage is usually the result of rate of the second stage is usually the result of increased levels of education.increased levels of education.

– Educated women find that they donEducated women find that they don’’t need to bear as t need to bear as many children to ensure that some will survive. They many children to ensure that some will survive. They may also learn family planning techniques.may also learn family planning techniques.

– Women are able to contribute to their familyWomen are able to contribute to their family’’s increasing s increasing prosperity while spending less energy bearing & caring prosperity while spending less energy bearing & caring for children.for children.

– As countries modernize, parents are more likely to work As countries modernize, parents are more likely to work away from home. If parents must pay for child care, away from home. If parents must pay for child care, children may become a financial burden rather than an children may become a financial burden rather than an asset.asset.

ObjectivesObjectives

DescribeDescribe three problems caused by rapid three problems caused by rapid human population growth.human population growth.

CompareCompare population growth problems in population growth problems in more-developed countries and less more-developed countries and less developed countries.developed countries.

AnalyzeAnalyze strategies countries may use to strategies countries may use to reduce their population growth.reduce their population growth.

DescribeDescribe worldwide population worldwide population projections into the next century.projections into the next century.

Changing Population TrendsChanging Population Trends

Throughout history, populations that have Throughout history, populations that have high rates of growth create environmental high rates of growth create environmental problems.problems.

A rapidly growing population uses resources A rapidly growing population uses resources at an increased rate & can overwhelm the at an increased rate & can overwhelm the infrastructure of a community.infrastructure of a community.

InfrastructureInfrastructure is the basic facilities of a is the basic facilities of a country or region, such as roads, bridges, country or region, such as roads, bridges, sewers, power plants, subways, schools, & sewers, power plants, subways, schools, & hospitals.hospitals.

Problems of Rapid GrowthProblems of Rapid Growth Uses resources Uses resources fasterfaster than the than the

environment can renew themenvironment can renew them Standards of living decline when wood is Standards of living decline when wood is

removed from local forests faster that it removed from local forests faster that it can grow back, or when wastes overwhelm can grow back, or when wastes overwhelm local water sources.local water sources.

Symptoms of overwhelming populations Symptoms of overwhelming populations include include suburban sprawl, polluted rivers, suburban sprawl, polluted rivers, barren land, inadequate housing, & barren land, inadequate housing, & overcrowded schoolsovercrowded schools..

Unsafe WaterUnsafe Water In places that lack infrastructure, the local In places that lack infrastructure, the local

water supply may be used not only for water supply may be used not only for drinking & washing but for drinking & washing but for sewage disposalsewage disposal..

The water supply then becomes a breeding The water supply then becomes a breeding ground for organisms that can cause ground for organisms that can cause diseases.diseases.

Many cities have populations that are Many cities have populations that are doubling every 15 years, & water systems doubling every 15 years, & water systems cancan’’t be expanded fast enough to keep up t be expanded fast enough to keep up with this growth.with this growth.

Impacts on LandImpacts on Land Arable landArable land is farmland that can be used to grow is farmland that can be used to grow

crops.crops. Growing populations make trade-offs between Growing populations make trade-offs between

competing uses for land such as agriculture, competing uses for land such as agriculture, housing, or natural habitats.housing, or natural habitats.– For example, Egypt has a population of more than 69 For example, Egypt has a population of more than 69

million that depends on farming within the narrow Nile million that depends on farming within the narrow Nile River valley.River valley.

– Most of the country is desert, and less than 4 percent of Most of the country is desert, and less than 4 percent of EgyptEgypt’’s land is arable.s land is arable.

– The Nile River Valley is also where the jobs are located, and The Nile River Valley is also where the jobs are located, and where most Egyptians live. They build housing on what was where most Egyptians live. They build housing on what was once farmland, which reduces Egyptonce farmland, which reduces Egypt ’’s available arable land.s available arable land.

UrbanizationUrbanization is an increase in the ratio or density is an increase in the ratio or density of people living in urban areas rather than in rural of people living in urban areas rather than in rural areas.areas.– People often find work in the cities but move into suburban People often find work in the cities but move into suburban

areas around the cities.areas around the cities.– This leads to traffic jams, inadequate infrastructure, & This leads to traffic jams, inadequate infrastructure, &

reduction of land for farms, ranches, & wildlife habitat. reduction of land for farms, ranches, & wildlife habitat. Meanwhile, housing within cities becomes more costly, Meanwhile, housing within cities becomes more costly, more dense, & in shorter supply.more dense, & in shorter supply.

A Demographically Diverse A Demographically Diverse WorldWorld Not every country in the world is progressing Not every country in the world is progressing

through each stage of demographic transition. through each stage of demographic transition. In recent years, the international community has In recent years, the international community has

begun to focus on the least developed countries.begun to focus on the least developed countries. Least developed countriesLeast developed countries are countries that are countries that

have been identified by the United Nations as have been identified by the United Nations as showing the fewest signs of development in showing the fewest signs of development in terms of income, human resources, & economic terms of income, human resources, & economic diversity.diversity.– These countries may be given priority for These countries may be given priority for

foreign aid & development programs to foreign aid & development programs to address their population & environmental address their population & environmental problems.problems.

A Demographically Diverse A Demographically Diverse WorldWorld

Populations are still growing rapidly Populations are still growing rapidly in less developed countries, with in less developed countries, with most of the worldmost of the world’’s population now s population now within within AsiaAsia..

ManagingManaging Development & Population Development & Population GrowthGrowth Today, less developed countries face the Today, less developed countries face the

likelihood that continued population growth will likelihood that continued population growth will prevent them from imitating the development of prevent them from imitating the development of the worldthe world’’s economic leaders.s economic leaders.

Countries such as China, Thailand, & India have Countries such as China, Thailand, & India have created campaigns to reduce the fertility rates of created campaigns to reduce the fertility rates of their citizens.their citizens.

These campaigns include These campaigns include public advertising, public advertising, family planning programs, economic incentives, family planning programs, economic incentives, or legal punishment.or legal punishment.

In 1994, the United Nations held the In 1994, the United Nations held the International International Conference on Population & DevelopmentConference on Population & Development (ICPD), (ICPD),

It involved debates about the relationships It involved debates about the relationships between population, development, & the between population, development, & the environment.environment.

Many countries favor stabilizing population Many countries favor stabilizing population growth through investments in development, growth through investments in development, especially through improvements in womenespecially through improvements in women’’s s status.status.

Managing Development and Managing Development and PopulationPopulation

With these goals, worldwide fertility With these goals, worldwide fertility rates are dropping as shown below.rates are dropping as shown below.

Growth Is SlowingGrowth Is Slowing

Fertility rates have declined in both more-Fertility rates have declined in both more-developed & less-developed regions. developed & less-developed regions.

Demographers predict that this trend will Demographers predict that this trend will continue & that worldwide population continue & that worldwide population growth will be slower this century than the growth will be slower this century than the last century.last century.

If current trends continue, most countries If current trends continue, most countries will have replacement level fertility rates will have replacement level fertility rates by 2050. If so, world population growth by 2050. If so, world population growth would eventually stop.would eventually stop.

Projections to 2050Projections to 2050

Looking at the graph below, most Looking at the graph below, most demographers predict the medium demographers predict the medium growth rate, and a world population growth rate, and a world population of 9 billion in 2050.of 9 billion in 2050.