Population ChangePopulation Change

Overview of Chapter 8Overview of Chapter 8

o Principles of Population EcologyPrinciples of Population Ecologyo Reproductive StrategiesReproductive Strategieso The Human PopulationThe Human Populationo Demographics of CountriesDemographics of Countrieso Demographics of United StatesDemographics of United States

Principles of Population EcologyPrinciples of Population Ecology

o Population EcologyPopulation Ecology• Study of populations and why their Study of populations and why their

numbers change over timenumbers change over time• Important forImportant for

• Endangered speciesEndangered species• Invasive speciesInvasive species

o PopulationPopulation• Group of individuals of same species living Group of individuals of same species living

in the same geographic area at the same in the same geographic area at the same timetime

Population DensityPopulation Density

o Population densityPopulation density• The number of individuals of a species per The number of individuals of a species per

unit area or volume at a given timeunit area or volume at a given time• Ex: minnows per Liter of pond waterEx: minnows per Liter of pond water

o Ovals below have same population, and Ovals below have same population, and different densitiesdifferent densities

Change in Population SizeChange in Population Size

Change in Population SizeChange in Population Size

Principles of Population EcologyPrinciples of Population Ecology

o How Do Populations Change in Size?How Do Populations Change in Size?o Global scale:Global scale:

r = b – d

Growth rate

Birth rate

Death rate

*remember that when calculating growth rates you always use per 1000 individuals in the population unless specifically stated otherwise!

Practice Problem: “Global Practice Problem: “Global Population Change”Population Change”

o You have a human population of 10, You have a human population of 10, 000 where there are 200 births per year 000 where there are 200 births per year and 100 deaths per year. Calculate the and 100 deaths per year. Calculate the natural growth rate of this population natural growth rate of this population (Hint: remember that we always calculate per 1000…reduce!)(Hint: remember that we always calculate per 1000…reduce!)

o Use r = b – d Use r = b – d

AnswerAnswer

o 200/10,000 = 20/1000 = 200/10,000 = 20/1000 = 0.020.02

o 100/10,000 = 10/1000 = 100/10,000 = 10/1000 = 0.010.01

o R = b – d = 0.02 – 0.01 = R = b – d = 0.02 – 0.01 = 0.01 or 1% per 0.01 or 1% per yearyear

o More examples can be found at the end of More examples can be found at the end of chapter 8chapter 8

Calculating Population Change: Calculating Population Change: “Local Population”“Local Population”

Birth (b), Death (d), Immigration (i) and Birth (b), Death (d), Immigration (i) and Emigration (e) are calculated per 1000 peopleEmigration (e) are calculated per 1000 people

Growth Growth raterate

Birth Birth raterate

Death Death raterate

Immigration Immigration raterate

Emigration Emigration raterate

r = (b – d) + (i – e) r = (b – d) + (i – e)

Practice Calculating Local Practice Calculating Local Population GrowthPopulation Growth

o Calculate the growth of a population of Calculate the growth of a population of 10, 000, that has 100 births, 50 deaths, 10, 000, that has 100 births, 50 deaths, 10 immigrants, and 100 emigrants10 immigrants, and 100 emigrants

o Use equation: Use equation: r = (b - d) + ( i – e )r = (b - d) + ( i – e )o REDUCE!REDUCE!

AnswerAnswer

o b =100/10,000 = 10/1000 = b =100/10,000 = 10/1000 = .010.010o d =50/10,000 = 5/1000 = d =50/10,000 = 5/1000 = 0.0050.005o i =10/10,000 = 1/1000 = i =10/10,000 = 1/1000 = 0.0010.001o e = 100/10,000 = 10/1000 = e = 100/10,000 = 10/1000 = 0.010.01o So, r = (0.010 – 0.005) + (0.001 – So, r = (0.010 – 0.005) + (0.001 –

0.010)0.010)o r = 0.005 – 0.009 = r = 0.005 – 0.009 = -0.004, or -0.4% per -0.004, or -0.4% per

yearyear

Maximum Population GrowthMaximum Population Growth

o Intrinsic Rate of Growth (Biotic Intrinsic Rate of Growth (Biotic Potential)Potential)• Growth rate under ideal conditionsGrowth rate under ideal conditions• J- Shaped Curve (exponential growth)J- Shaped Curve (exponential growth)

Environmental ResistanceEnvironmental Resistance

o Environmental limits (resistance)Environmental limits (resistance)• Prevent indefinite reproductionPrevent indefinite reproduction• Unfavorable food, water, shelter, predation, Unfavorable food, water, shelter, predation,

etc.etc.

o Carrying Capacity (K)Carrying Capacity (K)• Maximum # of individuals an environment Maximum # of individuals an environment

can supportcan support• Causes leveling off of exponential growthCauses leveling off of exponential growth• S- shaped curve of logistic population growthS- shaped curve of logistic population growth

Population CrashPopulation Crash

o Overshooting carrying capacity can Overshooting carrying capacity can lead to population crashlead to population crash• Abrupt decline in population densityAbrupt decline in population density

Factors That Affect Population SizeFactors That Affect Population Size

o Density Dependent FactorDensity Dependent Factor• Factor whose effect on population changes Factor whose effect on population changes

as population density changesas population density changes• Examples:Examples:

• PredationPredation• DiseaseDisease• CompetitionCompetition

• Sometimes cause Boom-or-Bust Population Sometimes cause Boom-or-Bust Population CyclesCycles

Boom-Or-Bust Population CyclesBoom-Or-Bust Population Cycles

Case Study- Predator Prey Dynamics Case Study- Predator Prey Dynamics on Moose and Wolf Isle Royaleon Moose and Wolf Isle Royale

o As wolf population increases, moose As wolf population increases, moose population decreases (and vice versa)population decreases (and vice versa)

Factors That Affect Population SizeFactors That Affect Population Size

o Density Independent FactorsDensity Independent Factors• Factors that affects population size, but is Factors that affects population size, but is

not influenced by changes in population not influenced by changes in population densitydensity

• Examples:Examples:• Killing frostKilling frost• Severe blizzardSevere blizzard• FireFire

Reproductive StrategiesReproductive Strategies

r-selected speciesr-selected species k-selected speciesk-selected species

-Small body size-Small body size

- Early maturity- Early maturity

- Short life span- Short life span

- Large broods- Large broods

- Little or no parental - Little or no parental carecare- Probability of long Probability of long term survival is lowterm survival is low- Mosquitoes and Mosquitoes and DandelionsDandelions

-Small broodsSmall broods-Long life spanLong life span-Slow developmentSlow development-Large body sizeLarge body size-Late reproductionLate reproduction-Low reproductive rateLow reproductive rate-Redwood trees and Redwood trees and human beingshuman beings

SurvivorshipSurvivorship

Some populations fit two curvesSome populations fit two curves

o Herring GullsHerring Gullso Type III (as Type III (as

chicks) & Type chicks) & Type II (as adults)II (as adults)

Human PopulationHuman Population

o DemographyDemography• Science of Science of

population population structure and structure and growthgrowth

o Human Population Human Population since 1980 is J-since 1980 is J-shaped curve shaped curve (exponential)(exponential)

Population experts believe that this graph will level out during the 21 century and represent an S-shaped curve.When this happens which individuals will be those dying and which will be those surviving???

Human PopulationHuman Population

1 Billion1 Billion 18001800

2 Billion2 Billion 19301930

3 Billion3 Billion 19601960

4 Billion4 Billion 19751975

5 Billion5 Billion 19871987

6 Billion6 Billion 19991999

6.6 Billion6.6 Billion 20062006

Population Increase in MexicoPopulation Increase in Mexico

High D.R. due to Mexican revolution

Analysis: death rate declined much more than the birth rate so there was a high population growth during the 20th century

Doubling TimeDoubling Time

o One Way to express population growth One Way to express population growth of a country is to determine it’s of a country is to determine it’s doubling timedoubling time

o Doubling Time = Doubling Time = The amount of time it The amount of time it takes for a population to double in size takes for a population to double in size (assuming that it’s growth rate (r) doesn’t change)(assuming that it’s growth rate (r) doesn’t change)

o Doubling time can identify a country as highly, moderate, or less Doubling time can identify a country as highly, moderate, or less developed.developed.

o The shorter the doubling time the less developed the country!The shorter the doubling time the less developed the country!o Formula (simplified): TD (time double) or DT (doubling time) = Formula (simplified): TD (time double) or DT (doubling time) =

70/r70/r

Replacement Level Fertility Replacement Level Fertility

o Replacement-level-fertility: The number Replacement-level-fertility: The number of children that a couple must produce of children that a couple must produce in order to “replace” themselvesin order to “replace” themselves

o It usually given as 2.1 childrenIt usually given as 2.1 childreno The number is greater than 2 b/c some The number is greater than 2 b/c some

children die before they hit children die before they hit reproductive agereproductive age

Total Fertility Level (global)Total Fertility Level (global)

o Total-Fertility-Level: The global average Total-Fertility-Level: The global average number of children born to each womannumber of children born to each woman

o Currently we are at 2.8!Currently we are at 2.8!o This is This is wayway above the replacement level above the replacement level

fertility rate!fertility rate!

Projecting Future Projecting Future Global Human Global Human

PopulationsPopulations

o Population is Population is increasingincreasing

o Growth rate (r) has Growth rate (r) has started to declinestarted to decline

o Projections for 2050Projections for 2050• Low = 7.7 billionLow = 7.7 billion• High = 10.6 billionHigh = 10.6 billion• Most likely = 9.1 billionMost likely = 9.1 billion

Demographics of CountriesDemographics of Countries

Demographic StagesDemographic Stageso Pre-industrial StagePre-industrial Stage

• Birth and death rates highBirth and death rates high• Modest population growthModest population growth

o Transitional StageTransitional Stage• Lowered death rateLowered death rate• Rapid population growthRapid population growth

o Industrial StageIndustrial Stage• Birth rate declineBirth rate decline• Population growth slowPopulation growth slow

o Post Industrial StagePost Industrial Stage• Low birth and death ratesLow birth and death rates• Population growth very slowPopulation growth very slow

Demographic StagesDemographic Stages

Age Structure Diagrams (or Age Structure Diagrams (or Pyramids) ExplainedPyramids) Explained

o A countries age structure helps us A countries age structure helps us predict the future growth of a countrypredict the future growth of a country

o The number of males/females at each The number of males/females at each age from birth to death is representedage from birth to death is represented

o It is especially important to look at the It is especially important to look at the pre-reproductive and reproductive pre-reproductive and reproductive years (generally speaking if they are years (generally speaking if they are larger then the population is expandinglarger then the population is expanding

Age Structure DiagramsAge Structure Diagrams

o The number and proportion of people at The number and proportion of people at each age in a populationeach age in a population

Demographics of Specific CountriesDemographics of Specific Countries

World-wide World-wide Population Statistics Population Statistics

o 29% of human 29% of human population is population is under age 15under age 15

o The higher the % The higher the % the higher the the higher the likelihood of likelihood of growthgrowth

o Could cause large Could cause large increase in birth increase in birth ratesrates

Education of Immigrants into USEducation of Immigrants into US

See envirobrief on pg. 179 of your text

Addressing Population IssuesAddressing Population Issues

Women in Egypt learning about family planning. Egypts TFR’s declined to 3.5, which was at 7.0 in the 1960’s

Overview Overview

o Population and Quality of LifePopulation and Quality of Life• Population and Chronic HungerPopulation and Chronic Hunger• Economic Effects of Population GrowthEconomic Effects of Population Growth

o Reducing the Total Fertility RateReducing the Total Fertility Rate• Culture and FertilityCulture and Fertility• Social and Economic Status of WomenSocial and Economic Status of Women• Family Planning ServicesFamily Planning Services

o Government Policies and FertilityGovernment Policies and Fertility• China, India, Mexico, Nigeria, EuropeChina, India, Mexico, Nigeria, Europe

o Achieving Population StabilizationAchieving Population Stabilization

Population and Quality of LifePopulation and Quality of Life

o Difficult to meet basic needs in Difficult to meet basic needs in developing countriesdeveloping countries

o Problems associated with Problems associated with overpopulation:overpopulation:• Environmental degradationEnvironmental degradation• HungerHunger• Persistent povertyPersistent poverty• Economic stagnationEconomic stagnation• Urban deteriorationUrban deterioration• Health issuesHealth issues

Carrying CapacityCarrying Capacity

o Carrying Capacity (K)Carrying Capacity (K)• The maximum number of individuals of a The maximum number of individuals of a

given species that a particular environment given species that a particular environment can support for an indefinite period, can support for an indefinite period, assuming no changes in the environmentassuming no changes in the environment

o Overuse of land can cause a decrease Overuse of land can cause a decrease in carrying capacityin carrying capacity

o Uncertain what the carrying capacity of Uncertain what the carrying capacity of the earth is for humansthe earth is for humans

Population and Chronic HungerPopulation and Chronic Hunger

o Food securityFood security• Condition in which people live with chronic Condition in which people live with chronic

hunger and malnutritionhunger and malnutrition

o Effects of Chronic HungerEffects of Chronic Hunger• Weakened immune Weakened immune

systemsystem• Increased susceptibility to Increased susceptibility to

illness and disease such asillness and disease such as• MalariaMalaria• MeaslesMeasles• DiarrheaDiarrhea• Acute respiratory illnessAcute respiratory illness

Population and Chronic HungerPopulation and Chronic Hunger

o Ways to Help Solve the Food ProblemWays to Help Solve the Food Problem• Control population growthControl population growth• Promote economic development of Promote economic development of

developing countries without adequate developing countries without adequate food suppliesfood supplies

• Provide access to food and land resources Provide access to food and land resources to those who live in areas without themto those who live in areas without them

Areas with Greatest Food Areas with Greatest Food ProblemsProblems

Economic Effects of Population Economic Effects of Population GrowthGrowth

o Two viewpoints from economists:Two viewpoints from economists:• Population growth stimulates economic Population growth stimulates economic

development and technological innovationdevelopment and technological innovation• Rapidly expanding hampers developmental Rapidly expanding hampers developmental

effortsefforts

o Most observations support the second Most observations support the second viewpointviewpoint

o Developmental efforts are also Developmental efforts are also hampered by debt from past hampered by debt from past development attemptsdevelopment attempts

Reducing the Total Fertility RateReducing the Total Fertility Rate

Three major influences on total fertility Three major influences on total fertility raterate

1.1. Cultural traditionsCultural traditions

2.2. Social & economic status of womenSocial & economic status of women

3.3. Family planning (or the lack of)Family planning (or the lack of)

Cultural Cultural TraditionsTraditions

o Culture influences and Culture influences and controls individuals’ controls individuals’ behaviorsbehaviors

o Marriage ageMarriage ageo Couple is expected to Couple is expected to

have large number of have large number of childrenchildren• Due to high infant and Due to high infant and

child mortality rateschild mortality rateso Children often work in Children often work in

family businessfamily business• Provide support for aging Provide support for aging

parentsparentso Religious valuesReligious values

Social & Economic Status of WomenSocial & Economic Status of Women

o Gender inequality is common worldwideGender inequality is common worldwideo DisparitiesDisparities

• Political participationPolitical participation• Social statusSocial status• Economic statusEconomic status• Health statusHealth status• Legal rightsLegal rights• EducationEducation• Employment andEmployment and

earningsearningsSingle most important factor affecting high total fertility Single most important factor affecting high total fertility

rates is low status of womenrates is low status of women

Illiteracy in 2002Illiteracy in 2002

Educational Opportunities and Educational Opportunities and FertilityFertility

o Women with more educationWomen with more education• Marry laterMarry later• Have fewer childrenHave fewer children

Family Planning ServicesFamily Planning Services

o In many countries men make In many countries men make reproductive decisions regarding reproductive decisions regarding contraceptivescontraceptives

o Family planning services offer Family planning services offer information to both men and women on:information to both men and women on:• SexualitySexuality• ContraceptionContraception• STDsSTDs• ParentingParenting

Contraceptive Use Among Married Contraceptive Use Among Married Women of Reproductive AgeWomen of Reproductive Age

Government Policies and Fertility- Government Policies and Fertility- ChinaChina

o Largest population in the world Largest population in the world o Controversial Family Planning PolicyControversial Family Planning Policy

• 1971- Chinese Government pursued birth 1971- Chinese Government pursued birth control seriouslycontrol seriously

• 1979- Incentives to promote later 1979- Incentives to promote later marriages and one-child familiesmarriages and one-child families

• Medical care, schooling for child, preferential Medical care, schooling for child, preferential housing, retirement fundshousing, retirement funds

• Brought about rapid and drastic decrease Brought about rapid and drastic decrease in fertilityin fertility

Government Policies and Fertility- Government Policies and Fertility- ChinaChina

o Law – controversial and unpopularLaw – controversial and unpopular• Compromised freedom of choiceCompromised freedom of choice• Social pressure to abort a second childSocial pressure to abort a second child• Pressure to abort/kill female first childPressure to abort/kill female first child

• More boys than More boys than girls in Chinagirls in China

o Law more Law more relaxed in rural relaxed in rural ChinaChina

Government Policy and Fertility- Government Policy and Fertility- IndiaIndia

o Severe population pressureSevere population pressure• 1950- first country with government-1950- first country with government-

sponsored family planningsponsored family planning• Did not work due to language/cultural barriersDid not work due to language/cultural barriers

• 1976- introduced incentives and 1976- introduced incentives and compulsory sterilizationcompulsory sterilization

• Unpopular and failureUnpopular and failure• Recent years- government focused on Recent years- government focused on

educationeducation• Much more effective, but TFR still above Much more effective, but TFR still above

replacement level (currently at 3.4)replacement level (currently at 3.4)

Government Policy and Fertility- Government Policy and Fertility- MexicoMexico

o Young age structureYoung age structure• Huge potential for population growth: 33% Huge potential for population growth: 33%

of population is under age 15of population is under age 15• Positive growth momentumPositive growth momentum

o 1974- government imparted 1974- government imparted educational reform, family planning, educational reform, family planning, health carehealth care• Very successfulVery successful

Government Policy and Fertility- Government Policy and Fertility- NigeriaNigeria

o Population challengePopulation challenge• Largest population of any African countryLargest population of any African country

o Very high reproductive potential: 43% Very high reproductive potential: 43% of population is less than age 15of population is less than age 15

o Current National Population PolicyCurrent National Population Policy• Improving health careImproving health care• Population educationPopulation education

Government Policy and Fertility- Government Policy and Fertility- EuropeEurope

o Population concernPopulation concern• Proportion elderly Proportion elderly

people in population is people in population is increasingincreasing

• Due to low TFRDue to low TFR

o Decrease in population Decrease in population could cause decrease could cause decrease economic growtheconomic growth

Achieving Population Achieving Population StabilizationStabilization

o How can developing country governments How can developing country governments help?help?• Increase $$ allotted to pubic health and family Increase $$ allotted to pubic health and family

planning servicesplanning services• Education on affordable, safe, effective methods of Education on affordable, safe, effective methods of

birth controlbirth control• Increase average level of educationIncrease average level of education

• Especially for womenEspecially for women

o How can developed country governments How can developed country governments help?help?• Provide financial supportProvide financial support• Supporting research and development of new birth Supporting research and development of new birth

control methodscontrol methods