Environmental ScienceEnvironmental Science

Chapter 9 Lecture NotesChapter 9 Lecture Notes

The Human PopulationThe Human Population

Introduction to Human Population Growth (11")

Chapter 9 TargetsChapter 9 Targets1. I can define demography and describe the 2

general categories of population growth they study.2. I can describe how the size and growth rate of the

human population has changed in the last 200 years.

3. I can make predictions about population trends based on age structure.

4. I can describe how survivorship, fertility, migration, death rate and life expectancy affect populations.

5. I can describe the four stages of the demographic transition.

6. I can name the 2 main factors affecting birth rates.

Demography: study of HUMAN populations Countries based on 2 population trends:

Developed and Developing countries. Developed countries have:

average incomes industrial economies social support systems population growth

Developing countries have: average incomes simple and agriculture-based economics population growth

Studying Human PopulationsStudying Human Populations

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Human population underwent Human population underwent exponential growth in the 1800s. WHY?exponential growth in the 1800s. WHY? Better Better food production food production andand hygiene hygiene

came with the industrial and scientific came with the industrial and scientific revolutionsrevolutions

The Human Population Over TimeThe Human Population Over TimeT2

http://www.ibiblio.org/lunarbin/worldpop

Age Structure Age structure/Population PyramidAge structure/Population Pyramid:: classifies a classifies a

population into groups by age agepopulation into groups by age age helps demographers make predictionshelps demographers make predictions Countries with high growth rates usually have Countries with high growth rates usually have more more

young young than old peoplethan old people Countries with slow growth or no growth usually Countries with slow growth or no growth usually

have an have an even distribution even distribution of ages in the of ages in the populationpopulation

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Russia United States

Ethiopa

SurvivorshipSurvivorship SurvivorshipSurvivorship:: % of % of

newborns in newborns in population expected population expected to survive to a given to survive to a given ageage used as another way used as another way

to predict population to predict population trendstrends

(see video)(see video)

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Which survivorship curve would belong to humans? Frogs? Robins?

Fertility Rates Fertility rateFertility rate:: number of births (per year) per 1,000 number of births (per year) per 1,000

women of childbearing age (usually 15 to 44)women of childbearing age (usually 15 to 44) Replacement levelReplacement level: average number of children each : average number of children each

parent must have in order to parent must have in order to ““replacereplace”” themselves themselves This number is slightly more than 2 because not all This number is slightly more than 2 because not all

children born will survive and reproducechildren born will survive and reproduce

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Migration MigrationMigration:: movement of individuals or movement of individuals or

populations from one location to anotherpopulations from one location to another Immigration vs. EmigrationImmigration vs. Emigration Populations of many developed countries might Populations of many developed countries might

be decreasing if not for immigrationbe decreasing if not for immigration

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Declining Death Rates

Dramatic Dramatic in human population in last in human population in last 200 years 200 years

Happened because death rates declined Happened because death rates declined faster than birth ratesfaster than birth rates Death rates declined mainly because more Death rates declined mainly because more

people now have access to enough food, people now have access to enough food, clean water, and safe sewage disposalclean water, and safe sewage disposal

Discovery of vaccines in 20th century also Discovery of vaccines in 20th century also contributed to declining death ratescontributed to declining death rates

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Life ExpectancyLife Expectancy Life expectancyLife expectancy::

average length of average length of time an individual is time an individual is expected to liveexpected to live Life expectancy is Life expectancy is

most affected by most affected by infant mortalityinfant mortality, , the death rate of the death rate of infants less than a infants less than a year oldyear old

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The Demographic TransitionThe Demographic Transition

Demographic transitionDemographic transition:: general general pattern of demographic change from pattern of demographic change from high birth/death rates to low high birth/death rates to low birth/death ratesbirth/death rates Seen during history of more-developed Seen during history of more-developed

countriescountries

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Stages of Demographic Transition Video (1")

Stages of TransitionStages of Transition First stage: society is preindustrialFirst stage: society is preindustrial

Birth/death rates are high and population size is stableBirth/death rates are high and population size is stable Second stage: population explosion occursSecond stage: population explosion occurs

Death rates decline as hygiene, nutrition, and education Death rates decline as hygiene, nutrition, and education improve. Birth rates remain high, so population grows very fast.improve. Birth rates remain high, so population grows very fast.

Third stage: population growth slows because birth rate decreasesThird stage: population growth slows because birth rate decreases Birth rate = death rate, population size stabilizes Birth rate = death rate, population size stabilizes

Fourth stage: birth rate drops below replacement level, population Fourth stage: birth rate drops below replacement level, population begins to decreasebegins to decrease

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

declinedecline in birth rates are in birth rates are increasing educationincreasing education and and economic independence for economic independence for womenwomen

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Chapter 9 TargetsChapter 9 Targets

7. I can describe three problems caused by rapid human population growth.

8. I can compare population growth problems in more-developed countries and less developed countries.

9. I can analyze strategies countries may use to reduce their population growth.

10. I can describe worldwide population projections into the next century.

Problems of Rapid GrowthProblems of Rapid Growth Rapidly growing population uses resources Rapidly growing population uses resources

faster than environment can renew themfaster than environment can renew them Living standards drop when wood is Living standards drop when wood is

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

Symptoms of overwhelming populations Symptoms of overwhelming populations include polluted rivers, barren land, include polluted rivers, barren land, inadequate housing, and overcrowded inadequate housing, and overcrowded schoolsschools

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Least developed countriesLeast developed countries: identified by : identified by U.N. as showing fewest signs of improving U.N. as showing fewest signs of improving income, human resources, and economic income, human resources, and economic diversitydiversity Populations are still growing rapidly in less Populations are still growing rapidly in less

developed countries, with most of the developed countries, with most of the worldworld’’s population now in Asias population now in Asia

A Demographically Diverse WorldA Demographically Diverse WorldT8

Less developed countries face continued Less developed countries face continued population growth that will prevent them population growth that will prevent them from developing into world economic from developing into world economic leadersleaders Countries such as China, Thailand, and India Countries such as China, Thailand, and India

have created campaigns to reduce fertility have created campaigns to reduce fertility rates of their citizensrates of their citizens

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

ManagingManaging Development and Development and Population GrowthPopulation Growth T10

In 1994, United In 1994, United Nations held Nations held International International Conference on Conference on Population and Population and Development (ICPD) Development (ICPD)

Involved debates Involved debates about relationships about relationships between population, between population, development, and the development, and the environmentenvironment

Managing Development and Managing Development and Population GrowthPopulation Growth T10

With these goals, worldwide fertility With these goals, worldwide fertility rates are dropping as shown below (see rates are dropping as shown below (see assignment)assignment)

Managing Development and Managing Development and PopulationPopulation T10

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 of growth rate, and a world population of 9.2 billion 9.2 billion in 2050in 2050

Current population is at 7 billionCurrent population is at 7 billion

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Population Clock