Population Dynamics, Carrying Capacity, and Human PopulationPopulation Dynamics, Carrying Capacity, and Human Population

Brian Kaestner

Saint Mary’s Hall

Brian Kaestner

Saint Mary’s Hall

Thanks to Miller and ClementsThanks to Miller and Clements

Population Dynamics and Carrying CapacityPopulation Dynamics and Carrying Capacity

Population dynamics Population dynamics

Zero population growth (ZPG) Zero population growth (ZPG)

Biotic potential (intrinsic rat of increase [r]) Biotic potential (intrinsic rat of increase [r])

Environmental resistance Environmental resistance

Carrying capacity Carrying capacity

Minimum viable population (MVP) Minimum viable population (MVP)

Population DispersionPopulation Dispersion

ClumpedClumped(elephants)(elephants)

UniformUniform(creosote bush)(creosote bush)

RandomRandom(dandelions)(dandelions)

Fig. 9.2, p. 199

Factors Affecting Population SizeFactors Affecting Population SizePOPULATION SIZE

Growth factors(biotic potential)

Favorable lightFavorable temperatureFavorable chemical environment(optimal level of critical nutrients)

Abiotic

BioticHigh reproductive rate

Generalized niche

Adequate food supply

Suitable habitat

Ability to compete for resources

Ability to hide from or defendagainst predatorsAbility to resist diseases and parasitesAbility to migrate and live in other habitatsAbility to adapt to environmentalchange

Decrease factors(environmental resistance)

Too much or too little lightTemperature too high or too lowUnfavorable chemical environment(too much or too little of critical nutrients)

Abiotic

BioticLow reproductive rate

Specialized niche

Inadequate food supply

Unsuitable or destroyed habitat

Too many competitorsInsufficient ability to hide from or defendagainst predatorsInability to resist diseases and parasitesInability to migrate and live in other habitatsInability to adapt to environmentalchange

Fig. 9.3, p. 200

Exponential and Logistic GrowthExponential and Logistic Growth

YearYear

Time (t)

Po

pu

lati

on

siz

e (N

)

Exponential GrowthExponential Growth

Time (t)

Po

pu

lati

on

siz

e (N

)K

Logistic GrowthLogistic Growth

YearYear

Nu

mb

er

of

rein

de

er

Nu

mb

er

of

rein

de

er

2.02.0

1.51.5

1.01.0

.5.5

Nu

mb

er

of

sh

ee

p (

mil

lio

ns

)N

um

be

r o

f s

he

ep

(m

illi

on

s)

18001800 18251825 18501850 18751875 19001900 19251925

2,0002,000

1,5001,500

19101910 19201920 19301930 19401940 19501950

1,0001,000

500500

Fig. 9.4, p. 201

Fig. 9.5, p. 201 Fig. 9.6, p. 201

Population Density EffectsPopulation Density Effects

Density-independent controlsDensity-independent controls

Density-dependent controlsDensity-dependent controls

Natural Population CurvesNatural Population CurvesN

um

ber

of

ind

ivid

ual

sN

um

ber

of

ind

ivid

ual

s

TimeTime

Irruptive

Stable

Cyclic

Irregular

Fig. 9.7, p. 202

The Role of Predation in Controlling Population SizeThe Role of Predation in Controlling Population Size

Predator-prey cycles Predator-prey cycles Top-down control Top-down control Bottom-up control Bottom-up control

Po

pu

lati

on

siz

e (

tho

us

an

ds

)P

op

ula

tio

n s

ize

(th

ou

sa

nd

s)

160160

140140

120120

100100

8080

6060

4040

2020

0018451845 18551855 18651865 18751875 18851885 18951895 19051905 19151915 19251925 19351935

YearYear

Hare

Lynx

Fig. 9.8, p. 203

Reproductive Patterns and SurvivalReproductive Patterns and Survival

Asexual reproduction Asexual reproduction Sexual reproduction Sexual reproduction

r-selected species r-selected species K-selected species K-selected species

r-Selected Species

cockroach dandelion

Many small offspringLittle or no parental care and protection ofoffspringEarly reproductive ageMost offspring die before reaching reproductive ageSmall adultsAdapted to unstable climate and environmental conditionsHigh population growth rate (r)Population size fluctuates wildly above and below carrying capacity (K)Generalist nicheLow ability to competeEarly successional species

Fewer, larger offspringHigh parental care and protection of offspringLater reproductive ageMost offspring survive to reproductive ageLarger adultsAdapted to stable climate and environmental conditionsLower population growth rate (r)Population size fairly stable and usually close to carrying capacity (K)Specialist nicheHigh ability to competeLate successional species

elephant saguaro

K-Selected Species

Fig. 9.10b, p. 205

Survivorship CurvesSurvivorship CurvesP

erce

nta

ge

surv

ivin

g (

log

sca

le)

Per

cen

tag

e su

rviv

ing

(lo

g s

cale

)

100100

1010

11

00

AgeAge

Fig. 9.11, p. 206

Human Impacts on EcosystemsHuman Impacts on Ecosystems

Habitat degradation and fragmentation Habitat degradation and fragmentation

Ecosystem simplification Ecosystem simplification

Genetic resistance Genetic resistance

Predator elimination Predator elimination

Introduction of non-native species Introduction of non-native species

Overharvesting renewable resources Overharvesting renewable resources

Interference with ecological systems Interference with ecological systems

Fig. 9.12, p. 208

Physiological changesPsychological changesBehavior changesFewer or no offspringGenetic defectsBirth defectsCancersDeath

Organism Level

Change in population sizeChange in age structure (old, young, and weak may die)Survival of strains genetically resistant to stressLoss of genetic diversity and adaptabilityExtinction

Population Level Population Level

Disruption of energy flow throughfood chains and webs

Disruption of biogeochemical cyclesLower species diversityHabitat loss or degradationLess complex food websLower stabilityEcosystem collapse

Environmental Stress

Key ConceptsKey Concepts

Factors affecting human population size Factors affecting human population size

Managing population growth Managing population growth

Human population problems Human population problems

Fig. 11.2a, p. 239

Average crude birth rate Average crude death rate

World

All developedcountries

All developingcountries

Developingcountries

(w/o China)

22

9

11

10

25

9

29

9

Fig. 11.2b, p. 239

Africa

LatinAmerica

Asia

Oceania

UnitedStates

NorthAmerica

Europe

38

14

24

6

22

8

18

7

15

9

14

9

10

11

Factors Affecting Human Population SizeFactors Affecting Human Population Size

Population change equationPopulation change equation

Zero population growth (ZPG)Zero population growth (ZPG)

Crude birth rate (BR)Crude birth rate (BR)

Crude death rate (DR)Crude death rate (DR)

Refer to Fig. 11-2 p. 239Refer to Fig. 11-2 p. 239

PopulationChange

PopulationChange == (Births + Immigration) – (Deaths + Emigration)(Births + Immigration) – (Deaths + Emigration)

Natural Rate of IncreaseNatural Rate of Increase

<1%

1-1.9%

2-2.9%

3+%Data notavailable

Annual worldpopulation growth

Fig. 11.3, p. 240

Fig. 11.6, p. 241

Asia

Europe

Africa

LatinAmerica

NorthAmerica

Oceania

3.7 billion

4.7 billion

728 million

714 million

800 million

1.3 billion

518 million

703 million

306 million

374 million

31 million

39 million

2000 2025

Fig. 11.5, p. 241

China

India

USA

Indonesia

Brazil

Pakistan

Russia

Bangladesh

Japan

Nigeria

2000 2025

1.26 billion1.4 billion

1 billion1.4 billion

276 million

338 million

212 million273 million

170 million

221 million

151 million

227 million

145 million137 million

128 million

177 million

127 million

121 million

123 million205 million

Births per woman

< 2

2-2.9

3-3.9

4-4.9

5+

NoData

Fertility RatesFertility Rates Replacement-level fertility Replacement-level fertility Total fertility rate (TFR) Total fertility rate (TFR)

Fig. 11.8, p. 242

Fig. 11.7, p. 241

World

Developedcountries

Developingcountries

Africa

LatinAmerica

Asia

Oceania

NorthAmerica

Europe

5 children per women2.9

2.5

1.5

6.53.2

6.65.3

5.92.8

5.92.8

3.82.4

3.52.0

2.61.4

1950 2000

The Demographic TransitionThe Demographic Transition

LowLow

HighHigh

Rel

ativ

e p

op

ula

tio

n s

ize

Rel

ativ

e p

op

ula

tio

n s

ize

Bir

th r

ate

and

dea

th r

ate

(nu

mb

er p

er 1

,000

per

yea

r)B

irth

rat

e an

d d

eath

rat

e(n

um

ber

per

1,0

00 p

er y

ear) 8080

7070

6060

5050

4040

3030

2020

1010

00

Stage 1Preindustrial

Stage 1Preindustrial

Stage 2Transindustrial

Stage 2Transindustrial

Stage 3IndustrialStage 3

IndustrialStage 4

PostindustrialStage 4

Postindustrial

Lowgrowth rate

Lowgrowth rate

Increasing Growthgrowth rate

Increasing Growthgrowth rate

Very highgrowth rateVery high

growth rateDecreasinggrowth rateDecreasinggrowth rate

Lowgrowth rate

Lowgrowth rate

Zerogrowth rate

Zerogrowth rate

Negativegrowth rate

Negativegrowth rate

Birth rate

Total population

Death rate

TimeTimeTimeTimeFig. 11.26, p. 255

Factors Affecting BR and TFRFactors Affecting BR and TFR

See bulleted list in text p. 243 See bulleted list in text p. 243

US BR’s and TFR’s US BR’s and TFR’s3232

3030

2828

2626

2424

2222

2020

1818

1616

1414

00

19101910 19201920 19301930 19401940 19501950 19601960 19701970 19801980 19901990 20002000 20102010

Bir

ths

per

th

ou

san

d p

op

ula

tio

nB

irth

s p

er t

ho

usa

nd

po

pu

lati

on

Demographictransition Depression

Baby boom Baby bust Echo baby boom

World War II

YearYearFig. 11.11, p. 243

see Fig. 11-10 p. 243

Fig. 11.9, p. 242

High

Medium

Low

12

11

10

9

8

7

6

5

4

3

21950 1960 1970 1980 1990 2000 2010 2020 2030 2040 2050

High10.7

Medium8.9

Low7.3

Year

Po

pu

lati

on

(b

illio

n)

Fig. 11.10, p. 243

4.0

3.5

3.0

2.5

2.02.1

1.5

1.0

0.5

01920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Year

Bir

ths

per

wo

man

Infant deathsper 1,000 live births

<10<10-35<36-70<71-100<100+Data notavailable

Factors Affecting DRFactors Affecting DR

Life expectancy Life expectancy Infant mortality rate (IMR) Infant mortality rate (IMR)

Fig. 11.14, p. 246

Factors Affecting Natural Rate of IncreaseFactors Affecting Natural Rate of Increase

Developed Countries5050

4040

3030

2020

1010

0017751775

18001800 1850

185019001900

19501950

20002000 2050

2050

Rat

e p

er 1

,000

peo

ple

Rat

e p

er 1

,000

peo

ple

Year

Rate ofnatural increase

Crudebirth rate

Crudedeath rate

Rate of natural increase = crude birth rate = crude death rate Rate of natural increase = crude birth rate = crude death rate

Developed Countries5050

4040

3030

2020

1010

0017751775

18001800 1850

185019001900

19501950

20002000 2050

2050

Rat

e p

er 1

,000

peo

ple

Rat

e p

er 1

,000

peo

ple Crude

birth rate

Rate ofnaturalincrease Crude

death rate

Year

Fig. 11.13, p. 245

Ages 0-14Ages 0-14 Ages 15-44Ages 15-44 Ages 45-85+Ages 45-85+

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Rapid GrowthGuatemala

NigeriaSaudi Arabia

Slow GrowthUnited States

AustraliaCanada

Slow GrowthUnited States

AustraliaCanada

MaleMale FemaleFemale

Zero GrowthSpainAustriaGreece

Zero GrowthSpainAustriaGreece

Negative GrowthGermanyBulgariaSweden

Negative GrowthGermanyBulgariaSweden

Population Age StructurePopulation Age Structure

Fig. 11.16a, p. 247

Solutions: Influencing Population SizeSolutions: Influencing Population Size

MigrationMigration

Environmental refugeesEnvironmental refugees

Reducing birthsReducing births

Family planningFamily planning

Empowerment of womenEmpowerment of women

Economic rewards and penaltiesEconomic rewards and penalties

Case Study: Slowing Population Growth in IndiaCase Study: Slowing Population Growth in India

Poor planningPoor planningBureaucratic inefficiencyBureaucratic inefficiencyLow status of womenLow status of womenExtreme povertyExtreme povertyLack of supportLack of support

Generally disappointing results:Generally disappointing results:

Case Study: Slowing Population Growth in ChinaCase Study: Slowing Population Growth in China

Economic incentivesEconomic incentivesFree medical careFree medical carePreferential treatmentPreferential treatmentIntrusive and coerciveIntrusive and coerciveLocally administeredLocally administered

Generally positive results:Generally positive results:

Cutting Global Population GrowthCutting Global Population Growth

Family planningFamily planning

Reduce povertyReduce poverty

Elevate the status of womenElevate the status of women