nber -Urban Forests - Environmental Health Values and Risks-此為英文文檔

NBERWORKINGPAPERSERIESURBANFORESTS:ENVIRONMENTALHEALTHVALUESANDRISKSweiXinghirenHuXiaaoXucZouWorkingPaper31554http//papers/w31554NATIONALBUREAUOFECONOMICRESEARCHCambridgeMA8August2023WethankseminarparticipantsattheRenminUniversityofChinaforhelpfulcomments.Allerrorsareourown.TheviewsexpressedhereinarethoseoftheauthorsanddonotnecessarilyreflecttheviewsoftheNationalBureauofEconomicResearch.NBERworkingpapersarecirculatedfordiscussionandcommentpurposes.Theyhavenotbeenpeer-reviewedorbeensubjecttothereviewbytheNBERBoardofDirectorsthataccompaniesofficialNBERpublications.?2023byJianweiXing,ZhirenHu,FanXia,JintaoXu,andEricZou.Allrightsreserved.Shortsectionsoftext,nottoexceedtwoparagraphs,maybequotedwithoutexplicitpermissionprovidedthatfullcredit,including?notice,isgiventothesource.UrbanForests:EnvironmentalHealthValuesandRisksJianweiXingZhirenHu,FanXia,JintaoXu,andEricZouNBERWorkingPaperNo.31554August2023JELNoI,Q23,Q53,Q56,R11STRACTForestsaccompanythecitieswebuild.Thereareanestimated5.5billionurbantreesintheUnitedStates.Globally,about25percentofurbanlandiscoveredbytreecanopy.Thisstudyexaminesurbanforestsasapolicytoolforairpollutionmitigation.WestudyanafforestationprograminthecityofBeijing,whichplantedatotalof2millionmuofgreenery–roughlythesizeofLosAngeles–acrossthecityoveradecade.Weconductaremote-sensingauditoftheprogram,findingthatitcontributestoasubstantialgreeningupofthecity.Thiscausessignificantdownwindairqualityimprovement,reducingaveragePM2.5concentrationatcitypopulationhubsby4.2percent.Rapidvegetationgrowth,however,ledtoa7.4percentincreaseinpollenexposure.Analysisofmedicalclaimsdatashowsaeroallergenstriggeredemergencyroomvisits,mirroringwell-documentedindustrialpollutioneffectsthoughlesssevere.Weofferinsightonmanagingurbanforests’healthrisks,identifyingharmfulpollenspeciesandsusceptiblepopulationsubgroups.JianweiXingNationalSchoolofDevelopmentPekingUniversityNo.5YiheyuanRoadBeijing100871jerryxing@hirenHuCharlesH.DysonSchoolofAppliedEconomicsandManagement,CornellUniversity300DayHall,10EastAvenueIthaca,NY14853zh443@XiaNanjingUniversityNanjing,210023xiafannjueducnaoXuNationalSchoolofDevelopmentingUniversityNo.5YiheyuanRoadBeijing100871xujtpkueducncZouossSchoolOfBusinessUniversityofMichigananAveAnnArborMI48109Rumichedu21.IntroductionUrbanpollutioncontrolisauniversalchallengeforcitiesworldwide.Citieshavetodealwithpollutionfromvarioussources,suchastransportation,construction,waste,energygeneration,andindustrialactivities(GlaeserandKahn,2010;CurrieandWalker,2011;ZhengandKahn,2013;Gendron-Carrieretal.,2022).Traditionalpollutionpoliciesfocusonreducingemissionsfromtheseindividualpollutionsources.Anotherapproachistomitigatepollutionexposureatreceptors–thepeople.Inthispaper,westudyurbanforests,oneofthemostprevalentpolicyinstrumentsinthatvein.ThereareanestimatedbillionurbantreesintheUnitedStates.Worldwide,urbantreecover–theproportionofthetotalurbanlandareacoveredbytreecanopy–isestimatedtobearound25percent(NowakandGreenfield,2018;2020).Urbanforests,andotherformssandherbaceousplantsareabletoabsorbhazardouschemicalpollutantsandfilteroutparticulatepollutionastheytravelthroughtheair(Nowak,1994).Asidefromenvironmentalbenefits,urbanforestsalsoenhancelandscapes,propertyvalues,andemploymentopportunities,makingitoftenapoliticallyviablepolicyinstrument.nomicandenvironmentallifetheireffectsaresparselystudiedintheeconomicsliterature.Westudythreesubjectsinthispaper.First,wedocumentasubstantialgreeningupofamegacityandexaminethecontributionbyagovernment-ledmassusingaquasi-experimentalresearchdesign.Third,weinvestigateacommonlywonderednegativeexternality–pollenemissionsresultingfromurbanafforestation–andusemedicalclaimsdatatoprovidesomeofthefirstdirectestimatesofthehealthburdensassociatedwiththeseaeroallergens.Welimitthisresearchtoenvironmentalandhealtheffectsasourfirst-orderfocus,thoughweexpecttheseeffectstobeassociatedwithabroadersetofeconomic,environment,andhealthoutcomes.OurstudysettingisBeijing,thecapitalcityofChina,whichhasapopulationofover20millionalgovernmentsrecentfocusoncombatingpollutionBeijingimplementedalarge-scaleurbanafforestationeffortcalledtheMillionMuProject(henceforthMMP),whichbeganinillionmuofgreenery–equivalentto515squaremiles,roughlythesizeofLosAngeles–spreadthroughoutthecity,withmanyforestpatchessituatednearthecity’smostdenselypopulatedareas.Webeginwitharemote-sensingauditofBeijing’sgreeningprogress.Usingasatelliteetween2001and2020.Thistrendacceleratednotablyafter2012,withnumerousdenselypopulatedareas3experiencingannualvegetationindexgrowthofover10percent.Bycross-referencinggovernmentmapsofMMPplantingsiteswithhigh-resolutionsatellitedata,wedemonstratethatmuchofthisgreengrowthinhotspotareasisindeeddrivenbytheMMPprogram.Thevegetationgrowthishighlyrelevanttocityresidentsasmanyplantingsitesarelocatedrightontheoutskirtsofdenselypopulatedareas.Weestimatethatover1.3millionpeople(7percentofthecitypopulation)liveinareasdirectlyinfluencedbyMMPplanting,andthevastmajorityofthecity’spopulationresideswithinafewkilometersofthesesites–which,aswewillshowlater,aresignificantlyimpactedbytheenvironmentaleffectsofthenewgreenerythroughspatialspillover.thistimeusingasatellitepollutionmeasurementastheoutcomevariable.WedocumentsharpimprovementsinairqualitywithinMMP’splantingareas,indicatingadistinctgradientthatwasnotobservedinthesamelocationspriortotheimplementationofthepolicy.FocusingsolelyontheMMPplantingareasoverlooksimportantspilloverbenefits.Forestsserveasnaturalabsorbersandfiltersthatmayreducepollutionthatwouldotherwisereachpopulationcenters.Toassessthebroadereffectonthepopulation,weusepollutionmonitoringdatafromin-situreal-timeairqualitymonitorsinstalledbythegovernmentnearpopulationhubs,combinedwithprevailingwindandthesedenselypopulatedlocations.Exploitingplausibleday-to-dayvariationsinwinddirections,wedemonstratethatupwindvegetationreducesparticulateairpollution.Forestshavealargeeffectonparticulatepollutionreduction,andalsoreducestracegaspollutantssuchassulfurdioxides.Placebotestsshowthatnoneofnconditionsatdownwindlocationsasthesourceofshocksinstead.Next,weexaminetheimpactofurbanforestsonambientpollenconcentration.Weusein-situmonitoringdatafrompollenmonitors,alsolocatedatpopulationhubs,thatcapturedailypollencounts.Usingthesamewind-direction-basedestimationmethoddescribedearlier,wedemonstratethatupwindvegetationleadstoasharpincreaseinpollenspikes.Theimpactofvegetationonpollenlevelsissizable,ifnotlargerandmorestatisticallypreciseintermsofelasticity,thanthepollutionreductioneffect.Forexample,givenanupwindvegetationshockofthesamesize,theresponseofthepollenspikeinlogscaleisovertwiceaslargeasthatofthereductioninfineparticulatematter(PM2.5).Ourestimatessuggestthatoverthefirsteight-yearperiodsinceMMPstarted,theprojectreducestheaveragepopulationPM2.5exposureinthecityby4.2percent(about2.9ug/m3from2012baseline).Thiseffectissignificant:thecityofBeijinghasachieveda40percentreductioninsinceChina’sWaronPollutioncampaign(Greenstoneetal.,2021);ourfindingssuggestasizableshareofthatreductionis4contributedbyurbanafforestation.Ontheotherhand,theMMPhasincreasedtheaveragepopulationpollenexposureby7.4percent.Naturally,thesefindingsraisequestionsaboutthehealthimplications.Inparticular,canpollenlattentionandresourcesandifsohowtheseeffectscomparetotheknownimpactsofairpollutionexposure?Thefinalpartofthistestimatesusingadministrativemedicalclaimsdatacoveringallcityresidents.Tobegin,wehighlighttwofactsaboutpollenandpollutionvariation:First,osureacrosspollenseasonsofdifferentyears;Second,thereisasignificantamountofindependentvariationindailytofday-to-daypollenfluctuationsonhealthcareutilization,andtocomparethemwiththesameoutcomesbutlookingatpollutionfluctuations.Wefindthatdailypollenshocksleadtosignificantincreasesinthenumberofemergencyroom(ER)visits,drivenmostlybythoseduetorespiratoryorsensorysystembothusingestimatesfromourowndataandthoseborrowedfromthepriorliterature.Thehealthevidencesuggeststhatthenegativehealthexternalityassociatedwithpollenexposureshouldnotbeoverlooked:itissignificantenoughtotriggerERvisits,withthemagnitudeoftheelasticitysimilartotheeffectsofpollutiononERvisits.However,severalcharacteristicsoftheeffectsindicatethattheoverallhealthcostofpollenexposureislikelysmallcomparedtothebenefitsofpollutionreduction:First,althoughbothpollenexposureandPM2.5contributetoanincreaseinthenumberofERvisitstoaThissuggeststhatERvisitsduetopollenexposuretendtobelessseverecomparedtothosetriggeredbyPM2.5.Second,pollenprimarilyleadstoincreasedERvisitsforpatientswhodonotrequirefurtherinpatientcare.Incontrast,itiswell-documentedthatPM2.5canresultinseverehealthemergenciesandcanleadtodeathevenatylowexposurelevelsDeschenesGreenstoneandShapiroDeryuginaetalHuangpopulation,pollenhasanequalorpotentiallystrongereffectonthenon-elderlypopulation.Wealsofindthatpollen’simpactappearstobeconcentratedamongindividualswithpriorallergyhistories,whichmayfacilitatetargetedpreventionefforts.eannualhealthcarecostsavingsresultingfromthereductionofPMduetotheMMPprojectrangetomillionUSDThiscorrespondstoaboutpercentofBeijingsitsmeasuredintermsofthe5valueofstatisticallife(VSL),amounttoanestimatedvalueof5billionCNY(710millionUSD).ThehealthcarecostsassociatedwiththeincreasedpollenexposurerelatedtotheMMPprojectareaboutone-ninthofthemagnitudeofthepollutionbenefits,totaling25to102millionCNY(3.5to14millionUSD).Weacknowledgethatfurtherresearchisnecessarytofullyaccountfortheimpactsofpollenonabroaderrangeofwell-beingmeasures,suchascognitivehealthandproductivityimpacts.Thispaperjoinsanascenteconomicsliteratureontheenvironmentalimpactsofforestsandtheirdownstreameffectsonhealthandeconomicprosperity,includingtheimpactsoflarge-scaledeforestationorafforestationondownwindprecipitationandagriculturaloutcomes(Araujo,2023;Grosset,Papp,andTaylor,2023),theeffectsofurbantreesonmicroclimateandpropertyvalues(Hanetal.,2021;Li,2023),rthofeconomicstudiescontrastswithavast,multi-disciplinaryefforttounderstandurbanforestsandtheirreduction,stormwatermanagement,wildlifehabitatprovision,amongmanyotherecosystemservicesthatciesmorebroadlyKahnandWalsh2015).Whilethenaturalsciencesoffervaluableinsightsintotheinteractionsbetweenforestsandtheenvironment,numerousquestionsremainopenregardingthereal-worldeffectiveness,efficiency,andequityofurbanafforestationpoliciesfromaneconometricstandpoint.1Inadditiontotheenvironmentalimpacts,auniquefeatureofurbanafforestationworthstudyingasapolicytoolisitstrackrecordofimplementabilityatlargescale.WehavestudiedthecityofBeijing,suchasLosAngeles’MillionTreesInitiative,NewYorkCity’sMillionTreesNYCinitiative,Toronto’sEveryTreeCountsprogram,andSingapore’sCityinaGardenproject.Thislevelofimplementationisnoteworthywhenconsideringurbanafforestationwithinthecontextofenvironmentalprotectionpolicies,whichoftenencounterfeasibilitychallenges,enforcementandcomplianceissues,andpoliticalresistancethatsimilarurbanafforestationprogramsandotherformsofgreeninfrastructurewillplayanincreasinglyimportantroleinfuturesustainableurbandevelopment(Thackeretal.,2019).1Forexample,onthetopicofurbanforestryandairquality,Nowak,Crane,andSevens(2006)usescomputationalmodelingapproachcombinedwithparametercalibrationtopredictimpactofurbantreesonairpollutionremoval.Inatmosphericscience,Abhijithetal.(2017)providesadetailedreviewoftheatmosphericinteractionsbetweenvegetationandsurrounding,andtheimplicationsforpollutionexposure.Inepidemiology,Rojas-Ruedaetal.(2019)conductsameta-analysisofrecentcohortstudieslinkingNDVItomortality.6andtheeconomicscostsintermsofcognitiveoutcomessuchastestperformance,crimes,andaccidents(Marcotte,2015;Bensnes,2016;Chalfin,Danagoulian,andDeza,2019;AkesakaandShigeoka,2022).Onthemethodfront,wejoinagrowingeconometricliteratureontreatmenteffectwithunitinterference(S?vje,Aronow,andHudgens,2021):althoughtheMMPpolicycausesforeststobeplantedalspillovereffectsarelikelydrivenbywindtransport–andbuildawinddirectivitydesigntocapturethephenomenon.WestimatesontwoothermarginaleffectestimatesthatcanbeobtainedmpactofpolicyonlocalvegetationgrowthandtheimpactOuranalysisisfacilitatedbyacomprehensivedatasetwecompiledcombininggovernmentsurveys,high-resolutionremotesensingdata,real-timegroundmonitoring,andadministrativemedicalclaimsdata,whichallowsustodirectlyestimateeachlinkonthecausalchainfrompolicyimplementationtoendpointhealthoutcomes.Therestofthepaperisorganizedasfollows:Section2discussespolicybackgroundanddata.Beijingsgreeningupandtheroleofthestudieshealtheffects.Section7tiestogethervariousestimatesanddiscussesimplications,andconcludesthepaper.2.BackgroundandData2.1BackgroundABriefChronicleofUrbanAfforestationPoliciesinBeijing.The1977WorldConferenceonseriousecologicalalarmstotheChinesegovernment.Inreaction,ChinainauguratedArborDayin1979andtheNationalCapital’sObligatoryTreePlantingDayin1985,encouragingpublicparticipationinthecountry’sgreentransformation;thecountryalsointroducednumerousinitiativesinthetwodecadesbetween1991and2010includingtheThree-NorthShelterForestprogram,theTaihangMountaintionzones7Beijing,thecapitalcity,hasbeenparticularlyproactiveinthismovement.Thisculminatedwhenthecitycommittedtoa“GreenOlympics”asthehostofthe2008BeijingOlympics,propellingmajorregionalafforestationandecologicalinitiativessuchastheBeijing-TianjinSandSourceControlProjectandtheBeijing-HebeiEcologicalWaterSourceProtectionForestConstructionProject.ytheplainareaofBeijingthehubforthecityspopulationandindustriesFigureAareaswith<100maltitude),hasbeenecologicallyunder-resourced,withlowerforestcoveragecomparedtothemountainousregions.Inanefforttoremedythis,in2012,theBeijingMunicipalGovernmentintroducedthe“MillionMuAfforestationProjectinPlainAreas.”WecallthisprojecttheMillionMuProjectMMPinthispaperThisambitiousinitiativeaimedtoaugmenttheforestcoverageintheseplainareasbyanadditionalonemillionmu(approximately165,000acres)overfiveyears,withagoaltoattainover25%forestcoveragerate.ThismarkedasignificantmilestoneinBeijing’songoingjourneyofurbanafforestationandecologicalrestoration.TheMillionMuProject.TheMMPprojectwasdiscussedinaJanuary2012meetingoftheBeijingMunicipalGovernmentaspartoftheBeijingMunicipalAirPollutionControlPlan2012-2020.ThestatedgoaloftheMMPprojectistoimprovetheecologicalenvironmentofthecapitalcity,reducePM2.5pollution,andpromotegreenandecologicaldevelopment.TheMMPprojectinvolvesboththeconversionofexistingconstructionlandandthereclamationofabandonedsandandgravelpitsforsofroadsandrivers,watersourceprotectionareas,andagriculturallynon-viablelandforfocusedforestcreation.Thespatiallayoutoftheseurbanforestswasplannedinalignmentwiththebroaderurbanandgreenspacesystemplanning.Theguidelinesareknownas“TwoRings,ThreeBelts,NineWedges,andMultipleCorridors.”2Specifically,“TwoRings”referstothecreationofcontinuousgreenbeltsalongsidedefenseintheplainarea.Furtherout,beyondtheSixthRingRoad,twoadditionalgreenbeltshavebeenestablished–anouteroneextending1,000metersinwidthandaninneronespanning500meters,jointlytheplainareaThreeBeltsdenotestheestablishmentofpermanentgreenbeltsalongthebanksoftheYongdingRiver,BeiyunRiver,andChaobaiRiver,eachstretchingatleast200meterswide.Thesebeltsfunctionasvitalecologicalpreservationzones.“Ninefinedmoderatelysizedsuburbanparkswithinninewedgeshapedareasoflimiteddevelopment.Togetherwithlarge,contiguousforestedareas,theseparksproviderewiththecitysoutskirtsMultipleCorridorsencompasses2/zwgk/cwgk/jbcwgg/202103/t20210319_2311459.html8thedevelopmentofgreenpassagesalongkeyroads,riversides,andrailways,aswellashealth-orientedgreenwaysthatinterconnectdifferentregionalforestlandscapesandparkgreenspaces.TheMMPshapefilesweuseintheanalysis(Figure2,forexample)representactualplantingsitesthatfallundertheseforestcreationguidelines.SeeSection2.2formorediscussion.ogramFinancingFundingfortheMMPconstructionwassourcedfrombothcityandsubcity(district)levels.Datapublishedbythecitygovernmentindicatethattheinitialinvestmentduringthefirstthreeyearsoftheproject(2012to2015)amountedto34.3billionCNY,ofwhich25.5billionCNYwascontributedbythecitygovernmentandtherestbydistrictgovernments.Investmentandconstructiononareas,andperformingmaintenanceandmanagementdutiespost-planting.Astheprogramexpandedtethetotalrecordedcostoftheprogramtobearound75billionCNY(about10billionUSD).WewillcomparethisfigurewithpotentialhealthbenefitsinSection7.ProgramOutcomes.From2012to2017,atotalof1.17millionmu(780,000hectares)ofafforestationandgreeningwascompletedinthecity.Followingthesuccessoftheseefforts,anewphaseofthemillionmuprojectwaslaunchedbythemunicipalgovernmentinlate2017andconcludedin2022.Thissecondphaseoftheprojecthadamoreextensivecoverage,spanningthecentralurbanarea,newtowns,andlowmountainousregions.Throughtwoconsecutivefive-yearroundsoftheMMPproject,atotalof2.07millionmu(135,000hectares)ofnewafforestationandgreeninghasbeenaddedtothecity.IntheplainareasofBeijing,theforestcoveragerateincreasedfrom15%in2011to31%in2022,whiletheoverallforestcoveragerateinthecityimprovedfrom38%to45%duringthesameperiod.DuetothelackofdataregardingtheexactplantingsitesestablishedinthefirstfiveyearsversusastheMMPpolicyperiod.TheScienceofUrbanForestsandPollution.Vegetationleavesreducepollutionthroughaprocessknownasphytoremediation.Thishappensintwomainways:First,smallopeningsonleaves(stomata)absorbtracegaspollutantssuchasnitrogendioxideandsulfurdioxide(HarrisandManning,2010;Yinetal.,2011);Second,leaves“filterout”particlepollutantsthroughdrydeposition(McDonaldandurbangreeneryarewidelyrecognizedasaneffectivetoolforpollutionreduction(e.g.,Baldauf,2017;Kumaretal.,2019).9Thereisonenotableexception:theimplicationsforground-levelozone,whereforestsandurbangreenerycanhavebothpositiveandnegativeeffects.Ononehand,plantingtreescanincreasetherateofozonedepositionandabsorption,reducingnear-groundozoneconcentrations.Ontheotherhand,certaintreespecies,suchaspoplar,willow,andoak,releasevolatileorganiccompounds(VOCs)torepelpestsandattractpollinatinginsects.TheseVOCsareprecursorstoozoneformation–thatis,theyreactwithnlighttoformozoneOurempiricalresultsbelowindeedshowthattheimpactofurbanforestsonozoneisnotasclearcutastheirimpactsonothercriteriaairpollutants.ClinicalEvidenceonPollenandHealth.InSection6,weeconometricallyquantifiesthelinkbetweenambientpollenconcentrationandemergencyroomvisits.Herewereviewsomeoftheclinicalfoundationofthatlink.Exposuretoallergenicpollenhasbecomeanincreasinglyconcerningenvironmentalhealthissueinurbanareasinrecentdecades(Biedermannetal.,2019;D’Amatoetal.,2015).Theprevalenceratesofseasonalallergiescausedbypollenrangefrom10%to40%indevelopedcountries,withanestimated400millionsufferersworldwide(Greineretal.,2011;Meltzeretal.,2012).Theriseinallergiesisparticularlyconcerninginthecontextofglobalwarming,asitisexpectedtoprolongtheplantgrowingseasonandincreasetheoverallpollenproductionperseason(Ziskaetal.,2019).Inhalationofairbornepollencanleadtoseasonalallergies,oftenreferredtoashayfeverorinosisThisconditionisawidespreadchronicissueandaglobalhealthconcernUnliketheyearroundthreatposedbyairpollution,suchasPM2.5,whichimpactstherespiratoryandcardiovascularhealthofalargeportionofthepopulation,exposuretopollenexhibitsstrongseasonalvariationsanddifferentiallyaffectsindividualswithallergyhistories.Allergicreactionsaretriggeredbytheimmunesystem.Whenapersonwhoisallergictosubstanceslikedust,mold,orpollenencountersthesesubstances,theirimmunesystemmightreactexcessively,producingantibodiesthatattacktheallergenaggressively.Anumberoftypicalallergicreactionsarelinkedwiththeproductionofaspecificantibodyknownasimmunoglobulinumptionorcontactwiththeskin.Symptomsofseasonalallergiescausedbypollenexposureinvolvesthesensorysystem,includingallergicrhinitis(sneezing,runnyandstuffynose)andallergicconjunctivitis(itchyeyesandtears).Inrarecases,asthmaandatopymayalsooccur(Sunetal.,2016).Severeallergicreactionscanleadtobronchitis,bronchialasthma,pulmonaryheartdisease,andevenlife-threateningsituations(Brunekreefetal.,2000).Pollenhasaparticularlynoticeableimpactonindividualswithrespiratoryallergies,whichaffectapproximately10-30%oftheglobalpopulation(Sierra-Herediaetal.,2018).Seasonalallergiesnotonlyworsenphysicalandmentalhealthbutalsodecreaseproductivity,increasemedicalexpenses,andreducedailyactivities,therebyimpactingpeople’squalityoflife.Higherpollencountsleadtoincreasedvisitstoasthmaemergencydepartmentsandmoresalesofover-the-counterallergymedications.Allergymedicationsusedtoalleviatesymptomscanhavesideeffectssuchasdrowsiness,drymouth,lethargy(Jáureguietal.,2009;Meltzeretal.,2012),whichmaynegativelyimpactcognitiveperformanceandproductivity.Differenttypesofpollenvaryinallergenicity,whichdependsonthestrengthofallergenicpollenantigensandthepollenconcentration.InBeijing,herbaceousplantslikeArtemisiaexhibitrelativelyhighaceaehaverelativelyweakallergenicitybuthighpollenlevelsduringthespringseason.Inthe1980s,thetotalamountofairbornepollen,primarilyfromherbaceousplants,washigherduringsummerandautumnthanduringthespringpeakperiod.Since2000,thepollencontentfromofthetotalannualpollencontent.Thisshiftbecameevenmorepronouncedsince2010,withasignificantincreaseinpollenfromspring-floweringdeciduoustreeslikeGinkgo,Platanus,andCupressaceae(ZhaoetalCurrentlythepredominantpollentypesinBeijingarefromcypressandpoplartrees.Chinesejuniperpollenhasalsobecomeanimportantallergenforspringpollenallergies,withthepeakallergyseasonrunningfromMarchtoMay.32.2DataSourcesThisproject’sdatasourcesaretabulatedinTable1.Hereweprovidemoredetailsabouteachsource.PlantingSites.WegetlocationinformationontheuniverseofMMPplantingsitesfromapolicydocumentpublishedin2022bytheBeijingMunicipalCommissionofDevelopmentandReform.Tobeclear,themapshowswheretreesandothergreeneryendedupbeingplanted(ratherthanwhereplantingwasplanned).4Wedigitizeandgeo-referencethesemapstocreatepolygonfilesthatrepresentlocationsofMMPsites.ThetotalareaofMMPsitesaccordingtoourdigitizeddatais2.38millionmu(about1,589illionmukmOuranalysisSectionprovides3See/xwzx/mtjj/202103/t20210326_3023644.html414thFive-YearPeriodLandResourcesProtectionandUtilizationPlaninBeijing(京政發(fā)[2022]26號:北京市“十四五”時期土地資源保護利用規(guī)劃,lastaccessedJanuary5th,2023.)Thisdocumentoutlineslandresourcesprotectionandutilizationplanningforthefive-yearperiodof2021-2025.ThedocumentprovidesMMPmapsasapartofitssummaryofachievementinthepreviousdecade.furthercross-referencechecksusingremote-sensingbasedvegetationindexdata,showingsharpincreaseinvegetationgrowthimmediatelystartingtheMMPboundaries.5LandUse.Weobtainland-useinformationfromChina’sLand-Use/CoverDatasets(CLUD)fromNaturalResourcesResearchattheChineseAcademyofSciencesCLUDaremainlybasedonLandsatimages,andgeneratedusingahuman-computerinteraction(HCI)interpretationprocess.Thedataareavailableat30-meterspatialresolutionandfive-yearintervals,andweobtaindataforthe2000,2010,and2020crosssections.Ouranalysisuseslevel-1classificationswhichcontainsixcategories:cropland,forest,grassland,waterbodies,constructionland,andunutilizedland.CLUD’slevel-1classificationisestimatedtohaveanaccuracyrateofover94percent(YangandHuang,2021).WeusethisdatatocharacterizethetypeofplaceswhereMMPplantingsareasweresited.populationdistributionatfinespatialscale.WeuseWorldPopmainlytodemonstratethelocationofpopulationhubsinthecity.VegetationIndex.NormalizedDifferenceVegetationIndex(NDVI)isawidely-usedremote-sensingmeasureofthedensityo