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Chapter 5

ENVS 137 Chapter 5: Chapter5HumanPopulationGrowth


Department
Environmental Science
Course Code
ENVS 137
Professor
zahina-ramos
Chapter
5

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CHAPTER5:HUMANPOPULATIONGROWTH
5.1:TheHistoryofHumanPopulationGrowth
ThreePeriodsofGrowth:
● Demographers:peoplewhostudythesize,density,anddistributionofhuman
populations
● Threeperiodsofhumanpopulationgrowth:
1. Preagriculturalperiod
a. Extendedover100,000years,510millionglobalpopulationatend
b. Advancementofskills(i.e.toolmaking)>abilitytoadapttonewenvironments
>humansspreadintonewregions>populationgrowth
2. Agriculturalperiod
a. Domesticationofplantsandanimals,developmentoffarming,newtechnologies
(i.e.irrigationandplowing)>increasedsupplyoffood>populationgrowth
b. 500millionatend
3. Industrialperiod(currentperiod)
a. Industrialrevolution(1800)
b. Technologiesincreasedfoodproduction,moldedlandtoaccommodatefarming
c. Improvedsanitation,advancesinmedicine
DemographicTransitionModel
● Economicdevelopmentimprovesoverallwellbeing(fewerdeathsandincreasedlife
expectancy)
● Economicdevelopmentcausesbirthratestodecrease
● ^Demographictransitionmodel(descriptive,notpredictive),describeslogisticgrowth
1. Pretransitionperiodpriortoeconomicdevelopment,populationlimitedbylow
availabilityoffoodandhighprevalenceofdisease
a. Highdeathratesanddeathrates(0populationgrowth,birthrate=deathrate)
2. MortalityTransitionimprovedeconomicconditionsrelievefoodshortages,better
livingconditions,healthcare,andexpandaccesstoeducation
a. Deathratedecreaseswhilebirthratestayshigh/increases
b. Rapid,sustainedpopulationgrowth
c. Ex.poorcountrieslikeAfghanistanandNiger
3. FertilityTransitioncontinuedeconomicdevelopment→socialandculturalchange
a. Leadtolowerbirthratesandfertilityrates(peopledelayhavingchildren)
b. TFR(thenumberofchildrenawomanhas)
c. Contraceptives,familyplanning
d. Deathratelow,birthratedecreases→populationgrowthslows(mostofthe
world’scountriesinthisfertilitytransition)
4. StabilityTransitionlowbirthrateandlowdeathrate
a. Birthratealmostequaltodeathrate(low)→0populationgrowth/declinein
population(Japan,Italy,Spain)
● CompareNiger(endofstage2)andtheNetherlands(approachingstage4)pg.129
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5.2:GlobalVariationinHumanPopulationGrowth
● Humanpopulationgrowthratethepercentchangeinthenumberofpeoplelivinginan
areaoveracertaintimeperiod
● Ingeneralthepopulationgrowthrateishighestintheworld’spoorestcountriesand
lowestintheworld’swealthiestcountries
BirthRatethenumberofbabiesborneachyear(expressedasapercentofthepopulation)
● Birthrateisdecreasing,butvariationsamongcountries
● Poorercountriesbirthrategenerallyhigh(Ethiopia1.4%)
● Wealthiercountriesbirthrategenerallylow(US4.3%)
● Womeninpoorercountriestypicallyhavechildrenatayoungeragethanwealthierones
● Agespecificbirthratestellthenumberofchildrenborninayearper1,000women
withdefinedagegroups
● Higherbirthratesamongyoungerwomen→shortergenerations→highergrowthrate
DeathRatethepercentofindividualsinapopulationthatdieeachyear
● Worldwidedeathratedeclining(improvednutrition,sanitation,healthcare),butvaries
betweencountries
● Deathratesinpoorercountriesarehigher(babiesvulnerabletodiseaseandmalnutrition
● Infantmortalityratethepercentofinfantswithinapopulationwhodiebeforeage1
(influencedbysanitation,waterquality,andhealthcareability)
● Survivorshiptheprobabilityofsurvivingtoaparticularage
● Niger→74%womensurvivetoage40,US→98%
● Adolescentwomenhavehighersurvivorshipratethanadolescentmen(menmorelikely
tobeinvolvedinaccidents/exhibitviolentbehavior),BUTpoorcountriesmaynotbetrue
becauseofhighdeathriskofmothersinchildbirth
● Survivorshipofwomenbeyondtheageof40exceedsthatofmen
● Lifeexpectancytheaverageagetowhichababybornatagiventimewilllive
(summarizessurvivorship)
● Lifeexpectancyincreaseddramaticallyoverpast6decades(46.9→70years)→
becauseofimprovementsinfoodproductionanddistribution,cleanerwater,advancesin
medicineandhealthcare
AgeStructure
● Survivorshipandagespecificbirthratesdetermineapopulation’sagestructure(the
distributionofapopulationbasedonageclasses)
● Agestructurepyramids(agesexpyramids/populationpyramids)graphicallyillustrate
howpopulationsareapportionedaccordingtoageandgender(examplespg.135)
● Widthofbars:numberofbothmalesandfemalesinapopulationforeachageclass
(yaxis)
● Colorcoding:showsapproximateagecategories(prereproductive,reproductive,and
postreproductive)
● Birthrateshigh,survivorshiplow→largeproportionofyoungpeople(widebase,thintip)
→rapidpopulationgrowth
● Birthrateslow,survivorshiphigh→moreevenlydistributed(similarwidths)→indicates
stablepopulationsizeorslowgrowth
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