Ch6Ch6

BIOL101BIOL101

• Thescopeofhumanpopula7ongrowth

• Theeffectofpopula7on,affluence,andtechnologyontheenvironment

• Fundamentalsofdemography

• Thedemographictransi7on

• Factorsthataffectpopula7ongrowth

• 1970Chinahad790millionpeople

• Facingstarva7on

• AverageChinesewomanhad5.8children

• Governmentins7tutedaone‐childpolicy

• China’sgrowthrateplummeted

• Firstusededuca7onandoutreach

• Laterins7tutedrewardsandpunishments

• 1984policyexemptedethnicminori7esandfarmers

• Programhasbeenbothsuccessfulandcontroversial

• Lowgrowthratemakesiteasiertodealwithchallenges

• Ithasproducedunintendedconsequences

• Killingoffemaleinfants

• 120boysto100girls–40‐60millionmissingwomen

• Black‐markettradeinteenagegirls

• Popula7onscon7nuetoriseinmostcountries

• Par7cularlyinpoverty‐strickendevelopingna7ons

• Therateofgrowthisslowing

• Butweares7llincreasinginabsolutenumbers.

Itwouldtake30years,coun4ngonceeachsecond,tocounttoabillion!

• Ittooknearlyallofhumanhistorytoreach1billion(~1810)

• In1930,~120yearslater,wereached2billion,andaddedthemostrecentbillionin12years(!)

• Weadd80millionpeopleeachyear(2.5people/second).

Duetoexponen4algrowth,evenifthegrowthratedeclines,popula4onwillcon4nuetogrow.

• Attoday’s1.2%globalgrowthrate

• Popula7onwilldoublein58years(70/1.2=58)

• IfChina’sratecon7nuedat2.8%

• Itwouldhavehad2billionpeoplein2004

• Popula7ongrowthresultsfrom

• Technology

• Medicalcare

• Sanita7on

• Food

• Deathratesdrop,butnotbirthrates

• Somepeoplesaygrowthisnoproblem

• Newresourceswillreplacedepletedones

• Butsomeresources(i.e.,biodiversity)areirreplaceable

• Qualityoflifewillsufferwithuncheckedgrowth

• Lessfood,space,wealthperperson

• Everythingisfinite!

• Popula7ongrowth

• Correlatedwithpoverty,notwealth

• Somepolicymakersbelievegrowthincreaseseconomic,poli7cal,andmilitarystrength

• Theyofferincen7vesformorechildren

• 67%ofEuropeanna7onsthinktheirbirthratesaretoolow

• Innon‐Europeanna7ons,49%feeltheirbirthratesaretoohigh

• TheIPATmodel:I=PxAxT

• Ourtotalimpact(I)ontheenvironmentresultsfromtheinterac7onofpopula7on(P),affluence(A),andtechnology(T)

• Popula7on:individualsneedspaceandresourcesandproducewaste

• 9.7hectaresperpersoninU.S.

• X300million=2.91billionhectares!

• Only11.3billionhectaresonearth

• Affluence:percapitaresourceuse

• GDPpercapitaproxy

• US=~47,000

• Technology:allowsincreasedexploita7onofresources

• Butcanalsoreduceourimpact(e.g.,decreaseemissions)

• Furthermodelrefinementsinclude:sensi7vityoftheenvironmenttoimpacts,educa7on,laws,ethics

• Humanscanraisetheenvironment’scarryingcapacitythroughtechnology.

• Howmanyhumanscantheworldsustain?

• 1–33billion• Buts7llfinite

• Allpopula7onprinciplesapplytohumans• Environmentalfactorslimitpopula7ongrowth• Theenvironmenthasacarryingcapacity(K)forhumans

• Demography

• Humanpopula7onecology

• Popula7onsize• Densityanddistribu7on• Agestructure,sexra7o• Birth,death,immigra7on,andemigra7onrates

• Ul7matepossiblehumanpopula7onsizeunknown

• Rawnumbersnottheonlyimportantaspect

• Popdensity/distribu7on• Highestdensityintemperate,subtropical,andtropicalbiomes

• Increasesnearcoasts,waterways,andci7es

Predic4onsofpopula4onsizedependondifferentassump4onsaboutfer4lityrates.

• Increaseddensityimpactstheenvironmentinthoselocales

• Butrelievespressureinless‐populatedareas

• Unpopulatedareastendtobeenvironmentallysensi7ve(i.e.,deserts,grasslands)

• Provideindica7onofpoten7alfuturegrowthrateataglance• Narrowbase,widermiddle/topindicatesslowinggrowth,

agingpopula7on• Widebase,narrowtopshowsayoung,rapidlygrowing

popula7on• Canada 0.82%(2009),0.79%(2011)• Madagascar2.7%(2009),2.97%(2011)

• Manypopula7onsaregemngolder

• Europeancountries,Japan,China

• Greaterfinancialburden

• Seniorci7zensrequiremorecareandfinancialassistance

• Reducesthenumberofdependentchildrenandcrimerates

• Historicalnaturallyoccurringsexra7osforhumansslightlyfavormales

• 106males/100females

• Malesareslightlymorepronetodeath

• Chinarecently‐120boys/100girls

• Someprovincesashighas138/100

• Genderimbalanceduetomalepreference

• Inresponsetothegovernment’sone‐childpolicy

• Ledtoselec7veabor7onoffemalefetuses

• Problem‐toomanysingleChinesemen

• Teenagegirlssome7meskidnappedandsoldasbrides

• Whetherapopula7ongrows,shrinks,orremainsstabledependson:

• Ratesofbirth,death,andmigra7on

• Birthandimmigra7onaddindividuals

• Deathandemigra7onremoveindividuals

• Technologicaladvancesledtodrama7cdeclineinhumandeathrates

• Medicine,increasedcropyields,watertreatment

• Wideningthegapbetweenbirthratesanddeathratesresul7nginpopula7onexpansion

Fallinggrowthratesdonotmeanadecreasingpopula4on,butonlythatratesofincreaseareslowing.

• Totalfer0lityrate(TFR)

• Averagenumberofchildrenbornperfemale

• Replacementfer0lity

• TFRthatkeepsthesizeofapopula7onstable

• Forhumans,replacementfer7lity=2.1

• Urbaniza7ondecreasesTFR

• Accesstomedicalcare

• Childrenaoendschoolandimposeeconomiccosts

• Withsocialsecurity

• Elderlyparentsneedfewerchildrentosupportthem

• Greatereduca7onallowswomentoenterthelaborforce

• Withlessemphasisonchildrearing.

• EveryEuropeanna7onnowhasaTFR<replacementlevel

• Naturalrateofpopula0onchange

• Popula7onchangeduetobirthanddeathratesalone

• Incountrieswithgoodsanita7on,healthcare,andfood,peoplelivelonger• Higherlifeexpectancy

• Demographictransi0on

• Modelofeconomicandculturalchange

• Explainsthedecliningdeathandbirthratesinindustrializedna7ons

• Stablepre‐industrialstate

• Highbirthanddeathrates

• Changestoastablepost‐industrialstate

• lowbirthanddeathrates

• Industrializa7oncausesthesechanges

• Asmortalitydecreases

• Lessneedforlargefamilies

• Parentsinvestinqualityoflife

• Becauseini7allybirthratesremainhighwhiledeathratesarelow,popula7ongrowthoccurs.