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1、PopulationinAfricaIn1990,35percentoftheworld'spopulationlivedon1percentoftheice-freeland,accordingtodatafromSEDAC,theSocioeconomicDataandApplicationsCenteroperatedbytheCenterforInternationalEarthScienceInformationNetworkatColumbiaUniversity.Concernedabouttheimpactof
2、growingpopulationontheglobalenvironment,researchersandpolicymakershavebegunfocusingresearcheffortsontheviabilityofregionalandnationaleconomiesandhumanproximitytonaturalhazards.Asresearchresultsreturn,globalpopulationdataarehelpingscientists,resourcemanagers,andpolic
3、ymakerstoforecastandpreparefortheimpactoftheworld'sever-growingpopulation. Agrowingglobaleconomyhasresultedinblurringofnationaleconomicboundaries,generallyincreasingwealth,andimprovingaccesstohealthandtechnologyformostoftheworld'sdevelopedcountries.However,therateo
4、feconomicdevelopmentforpoornationsismuchslowerthanthatofdevelopednations.TheWorldBankestimatesthatalmosthalfoftheworld'spopulation,about2.8billion,liveonlessthan$2perdayandthattheaverageincomeoftheworld'srichestnationsis37timeshigherthanthatofthepoorest20nations.Thi
5、samountstoadoublingineconomicdisparityoverthepast40years.ResearchersatHarvard'sCenterforInternationalDevelopment(CID)studiedtherelationshipofclimateto,andtheeffectofdiseaseandagriculturalproductivityontheeconomicsuccessofacityorregion."EachyeartheWorldBankpublishesm
6、apsdetailingnationalgrossdomesticproduct,andeachyearthemapsshowmostofthecountriesinthetropicstobepoor,evenafteryearsofeconomicandinstitutionalreforms,"saidAndrewMellinger,aresearchassociateattheCID."Wewerepuzzledbythefactthatthemethodsadoptedbyaidagenciesdidnotseemt
7、oaffectchangeindevelopingtropicalcountries."Tobetterunderstandthisproblem,MellingerandcolleaguesJeffreySachsandJohnGallupusedgeographicinformationsystemmappingtechniquestoidentifygeographicandeconomicpatternsinpoorregions.Usingdetailedglobalpopulationdensitydatafrom
8、SEDACtocreateamapdelineatingcountriesbasedontheirGrossNationalProduct(GNP—thetotalvalueofallgoodsandservicesproducedbyacountryduringoneyea
