2Climate Effects on Food Security An Overview

13BookID182985_ChapID2_Proof#1-10/10/2009AbstractThereareroughly1billionfoodinsecurepeopleintheworldtoday,eachhavingthisstatusbecausefoodisunavailabletothem,becauseitisunaffordable,orbecausetheyaretoounhealthytomakeuseofit–orsomecombinationofthethree.Assessingthepotentialeffectsofclimatechangeonfoodsecurityrequiresunderstandingtheunderlyingdeterminantsofthesethreeaspectsoffoodsecurity–availability,access,andutilization–andhowclimatechangemightaffecteach.Thischapterexplorestheseaspectsanddeterminantsoffoodsecurity,summarizingthebasicmechanismsbywhichclimatechangemightimpactthelivesoftheglobalfoodinsecure.2.1IntroductionRoughlyabillionpeoplearoundtheworldlivetheirlivesinchronichunger,andhumanity’sinabilitytoofferthemsustainedlivelihoodimprovementshasbeenoneofitsmostobdurateshortcomings.Althoughrapidimprovementsinagriculturalproductivityandeconomicgrowthoverthesecondhalfofthetwentiethcenturybroughtfoodsecuritytobroadswathsofthedevelopingworld,otherregionsdidnotshareinthatsuccessandremainnobetterofftoday–andinsomecasesworseoff–thantheyweredecadesago.Progressinunderstandingwhysomeofthesecountriesemergedfrompovertyandfoodinsecurity,andwhyothersdidnot,hasbeensimilarlylimited.Suchques-tionsarecentraltotheeconomicsdisciplineandhavebeenanactiveareaofresearchforcenturies,buttheyhavegeneratedremarkablylittleconsensusonhowtoeffectthetransitionfrompovertytowealth.Muchofthecontroversyarisesbecausefoodsecurity(andrelatedmeasuresofwell-being)havemultiple,complexdeterminants,withvaryingagreementonwhichcausesaremoreorlessimportant.Butconfrontingthiscomplexityiscentraltoanyunderstandingofthepotentialimpactsofclimatechangeonfoodsecurity.ForChapter2ClimateEffectsonFoodSecurity:AnOverviewMarshallBurkeandDavidLobellD.LobellandM.Burke(eds.),ClimateChangeandFoodSecurity,AdvancesinGlobalChangeResearch37,DOI10.1007/978-90-481-2953-9_2,©SpringerScience+BusinessMedia,B.V.200M.Burke()andD.LobellStanfordUniversity,CA,USA114M.BurkeandD.LobellBookID182985_ChapID2_Proof#1-10/10/2009BookID182985_ChapID2_Proof#1-10/10/2009instance,knowledgeoftheimpactsofclimateoncropyieldsaloneisnotenoughtounderstandfoodsecurityimpacts,becausefoodsecurityisaproductofcomplexnatu-ralandsocialsystemsinwhichyieldsplayonlyone(albeitimportant)part.Instead,understandingclimatechange’sfullimpactwillrequireknowledgeofitspotentialeffectsonboththeproximatecausesoffoodinsecurity(e.g.,lowagriculturalyields,lowruralincomes)aswellasonthemorefundamentalcausesofpooreconomicprogress(e.g.,poorly-functioninginstitutionsandmarkets,loweducationlevels,highdiseaseburden).Ourgoalinthischapterisnottoassignpriorityamongpossiblefactors,buttooutlinehoweachmightbeaffectedbyclimatechangeandwhatinturnthiscouldmeanforprogresstowardsachievingglobalfoodsecurity.2.2FoodSecurity:Definition,Measurement,andRecentProgressAlthoughanearlierstudycountedatleast30definitionsoftheterm“foodsecurity”(MaxwellandSmith1992),thebenchmarkunderstandingofthetermisroughlythatofFAO(FAO2001):Foodsecurityisasituationthatexistswhenallpeopleatalltimeshavephysical,social,andeconomicaccesstosufficient,safeandnutritiousfoodthatmeetstheirdietaryneedsandfoodpreferencesforanactiveandhealthylife.Underthisdefinition,foodsecurityconsistsofhaving,onanindividuallevel,thefoodoneneedsandwants.Thisdefinitionisthenconventionallysubdividedintothreemaincomponents:foodavailability,foodaccess,andfoodutilization.Availabilityreferstothephysicalpresenceoffood;accessreferstohavingthemeanstoacquirefoodthroughproductionorpurchase;andutilizationreferstotheappropriatenutri-tionalcontentofthefoodandtheabilityofthebodytouseiteffectively.Weexploreeachoftheseaspectsoffoodsecurityinthecontextofclimatechangebelow.2.2.1MeasuringFoodSecurityPropermeasurementoffoodsecurityisofclearpolicyandhumanitarianconcern,primarilybecausesuchmeasuresareusedtobothassessprogressinagivenregionandtotargetassistancewhereneeded.However,giventhemultipleinteractingcomponentsoffoodsecuritylistedabove,measurementoffoodsecurityisbothdifficultandcontroversial.Themostcitedcountry-andglobal-levelstatisticsonfoodsecurityarethoseofFAO,whouseameasureof“undernourishment”asaproxyforfoodsecurity.Thismeasurereliesprimarilyonnationalleveldataonfoodsupplytoestimatethepercentageofagivencountry’spopulationthatdoesnothaveaccesstosufficientdietaryenergy.FAO’sestimationprocedure,showngraphicallyinFig.2.1,isroughlyasfollows(Naiken2002):152ClimateEffectsonFoodSecurity:AnOverviewBookID182985_ChapID2_Proof#1-10/10/20091.Foragivencountry,sumupthetotalnumberofcaloriesavailableforhumanconsumptioninagivenyear,whichwillbeacombinationoflocallyproducedfoodandimportedfood,minusexports.2.Dividebythecountry’spopulationtodetermineaveragepercapitaconsumption.3.Determinetheshapeofthedistributionaroundthismean,eitherfromhouseholdincomeorexpendituresurveyswhereavailable,orfromimputationfromothersourceswherenot.4.Usecountry-leveldataonaverageheightandweighttoestimatetheminimumamountofenergyneededtomaintainlightactivity,andapplythedistributionfrom(3)todeterminewhatpercentageofthepopulationfallsbelowthisthreshold.Th