biol 101 ch 6 human population part 1philipdarrenjones.com/web_documents/biol_101_ch_6... ·...
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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.
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