Emergy evaluation and economic analysis of three wetland fish farming systems in Nansi Lake area, Ch17
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Emergy evaluation and economic analysis of three wetland fish farming systems in Nansi Lake area, Ch17
JournalofEnvironmentalMa；Contentslistsavailableat；JournalofEnvironmentalMa；journalhomepage:www.else；e/jenvman；Emergyevaluationandecono；L.X.Zhanga,S.Ulgiatib,Z.；ab；StateKeyJointLabo
JournalofEnvironmentalManagementxxx(ContentslistsavailableatScienceDirectJournalofEnvironmentalManagementjournalhomepage:/locate/jenvmanEmergyevaluationandeconomicanalysisofthreewetland?shfarmingsystemsinNansiLakearea,ChinaL.X.Zhanga,S.Ulgiatib,Z.F.Yanga,*,B.ChenaabStateKeyJointLaboratoryofEnvironmentalSimulationandPollutionControl,SchoolofEnvironment,BeijingNormalUniversity,Beijing100875,PRChinaDepartmentofSciencesfortheEnvironment,ParthenopeUniversityofNapoli,ItalyarticleinfoArticlehistory:Received28September2009Receivedinrevisedform25August2010Accepted3October2010AvailableonlinexxxKeywords:Wetland?shfarmingEmergyaccountingEconomicanalysisSustainabilityabstractEmergyandeconomicmethodswereusedtoevaluateandcomparethree?shproductionmodels,i.e.,cage?shfarmingsystem,pondintensive?shrearingsystemandsemi-naturalextensivepond?shrearingsystem,inNansiLakeareainChinaintheyear2007.Thegoalofthisstudywastounderstandthebene?tsanddrivingforcesofselected?shproductionmodelsfromecologicalandeconomicpointsofview.Thestudyconsideredinputstructure,productionef?ciency,environmentalimpacts,economicviabilityandsustainability.Resultsshowthatthemaindifferenceamongthethreeproductionsystemswastheemergycostfor?shfeedassociatedwiththeirfeedingsystem,i.e.,feedingonnaturalbiomasssuchasplanktonandgrassoroncommercialfeedstock.AsindicatedbyEYR,ELRandESI,itcanbeclearlyshownthattheintensiveproductionmodelwithcommercialfeedisnotasustainablepattern.However,thepointisthatmoreenvironmentallysoundpatternsdonotseemabletoprovideacompetitivenetpro?tintheshortrun.Theintensivepond?shfarmingsystemhadanetpro?tof2.57Et03$/ha,muchhigherthan1.27Et03$/haforcage?shfarmingsystemandslightlyhigherthan2.37Et03$/haforsemi-natural?shfarmingsystem.Withregardtothedriversoflocalfarmer’sdecisions,theaccessibilityoflandfortherequireduseandinvestmentabilitydeterminethefarmer’schoiceoftheproductionmodelandthescaleofoperation,whileotherfactorsseemtohavelittleeffect.Theoretically,thedevelopmentofenvironmentallysustainableproductionpatterns,namelywaterandlandconservationmeasures,greenerfeedaswellaslowwastesystemsisurgentlyneeded,tokeepproductionactivitieswithinthecarryingcapacityofecosystems.Coupledemergyandeconomicanalysescanprovidebetterinsightintotheenvironmentalandeconomicbene?tsof?shproductionsystemsandhelpsolvetheproblemsencounteredduringpolicymaking.ó2010ElsevierLtd.Allrightsreserved.1.IntroductionAquacultureactivitiesinChina,especiallyfreshwateraquacul-ture,haveaverylonghistory,andthe?rstworknamedGuidebooktoPisciculturebyFanLicanbetracedbacktotheChineseSpringandAutumnPeriod(770e476B.C.).SincethebirthofNewChinain1949,theStatehasalwaysgivenhighprioritytotheproductionofaquaticproductsanddevotedmajoreffortstoexpandruralaquaculture,because?shfarmingplaysacrucialroleinboostingruraldevel-opmentandreducingpovertyandhungerinChina.Therefore,aquacultureisthefastestgrowingsub-sectorofagricultureandithasmadeChinathelargestaquacultureproducerintheworld.In2007,?sheryproductionwas47.48millionmetrictonsinChina,out*Correspondingauthor.Tel.:t;fax:t.E-mailaddresses:zhanglixiao@(L.X.Zhang),zfyang@(Z.F.Yang)./$eseefrontmatteró2010ElsevierLtd.Allrightsreserved.doi:10.1016/j.jenvman.ofwhichfreshwateraquacultureproductionwas21.97millionmetrictons,representingabout46.27%ofthetotalChinese?sheryproduction(CSY,2008).Oneofthedirectconsequencesoftherapidexpansionoffreshwateraquacultureisthatalargeamountofwetlandsinruralareashavebeencultivatedforseveraltypesof?shfarming,i.e.,pens,cages,rafts,andinlandpondsandrice?elds.Inaddition,withthechangesinlanduserightsandthedesireoffarmerstoincreaseproduction,traditionalpolycultureandintegrated?shfarmingsystemshavebeenchallengedbyintensiveproductionmodelscharacterizedbymonoculturesystemswithhighinputofcommercialfeed,fertilizersandpesticides,whichhavecausedsevereecologicaldegradationandenvironmentaldamagetothewetlandecosystem(Luetal.,2007;Paolietal.,2008).Takingfood-relatedwasteasanexample,only25e35%oftheinputfeedcontributestotheincreasedweightof?sh,whiletheremaining65e75%isleftinthewaterenvironmentscausingseverepollutionsmanifestedaseutrophication(LiuandHuang,2008).Thefrequent2L.X.Zhangetal./JournalofEnvironmentalManagementxxx(Fig.1.LocationofNansilakeandstudysitesofthethree?shrearingsystems.outbreakofalgalbloomsinlargeChineselakesinrecentyearsisevidencethattheenvironmentalsustainabilityoftherapidexpansionofintensive?shfarmingandaquacultureinwetlandareasofruralChinaisnowinquestion.Theintensiveproductionmodelanditsrelatedenvironmentalimpactsareregardedasthemaincauseoffrequentalgalbloomsaswellasotherenvironmentaleffects(Zuoetal.,2004;Luetal.,2007).Therefore,effortmustbefocusedonthedevelopmentofecologicallysustainableaquaculturethatisabletoexploitthenaturalenvironmentwithoutseverelyorirreversiblydegradingit(FolkeandKautsky,1992;Gomieroetal.,1997;Vassalloetal.,2007).Aquacultureoperatesattheinterfacebetweennatureandthehumaneconomyandcombinesnaturalresourcesandeconomicinputtoyieldaquaticproducts(Martinetal.,2006).Asaconse-quence,itisnecessarytoaccountforbothaspectsinequivalenttermswhencomparingtheresourceuseofdifferent?sheryproductionmethods(Campbell,1998).Ifenvironmentalinput?owsarenotproperlyaccountedforrelativetoeconomicones,optimumuseofresourcesmaynotbeachieved,andmanagementdecisionswillbebasedonincompleteanalyses(Ulgiatietal.,1994).Anintegratedapproachtoquantifytheimpactofaquaculturefarmingsystemswithinlakeandwetlandareasonenvironmentalresources,economicinvestmentandhumanlaborwithregardtolocaldevelopmentandecologicalconservationisbadlyneeded.EmergyanalysisandsynthesiscanbeusedasanaccountingmethodcapableofconsideringbothnaturalandeconomicaspectsL.X.Zhangetal./JournalofEnvironmentalManagementxxx(Table1Descriptionofthethree?shfarmingsystemsinNansiLakearea.FarmingmodelCage?shfarmingIntensivepond?shfarmingLocationN??????????3804800?? 003FeedingsystemNaturalfeedingwithplanktonArti?cialfeedingbycommercialfoodArti?cialfeedingbygrassgatheredaroundAreaanddepth4.02.50.42.0hamhamFishspeciesSilvercarpSpottedsilvercarpGrasscarpSilvercarpSpottedsilvercarpGrasscarpSilvercarpOwnershipIndividualownershipunderHRSRentSemi-naturalextensivepond?shfarming0.67ha3.0mSelf-builtunderHRSofasystemandofcomparingproductsonacommonbase(Odum,1996;Zhangetal.,2009).Byde?nition,emergyistheavailableenergyofonekindpreviouslyusedupdirectlyandindirectlytomakeaserviceorproduct.Itisusuallyquanti?edinsolarenergyequivalentsandexpressedassolaremJoules(seJ)(Odum,1996;UlgiatiandBrown,2009).Theratiooftheemergyrequiredtomakeaproductorservicetothepresentenergyoftheproductorserviceisde?nedasthesolartransformityoftheproduct.Theemergycontentofaproductorserviceiscalculatedbymultiplyingunitsofenergybyitsappropriatetransformity.TheunitsofthesolartransformityaresolaremJoulesJà1,abbreviatedasseJJà1,otheremergyperunitvaluesarethespeci?cemergy,solaremJouleskgà1(seJkgà1)andtheemergytomoneyratio,solaremJoules$à1(seJ$à1).ThelatterindicatoriscalculatedwhenacountryevaluationisperformedbydividingthetotalemergyannuallyusedinthecountrytotheGDP(GrossDomesticProduct)generated.Itindicatestheemergyinvestmentneededtocreateaunitofmonetarywealthandthereforeallowstheconversionofagivenamountofmoneyintotheemergyrequiredintheeconomyforitsgeneration.Theemergytomoneyratioisusedintheemergycalculationprocedurestoconvertintoemergyunitsthemoneyinputsassociatedtolaborandservices.ThetheoreticalbackgroundanddetailedemergyalgebrahavebeenstatedbyOdumandhiscollaborators(Odum,;BrownandUlgiati,1997;Odumetal.,2000).Afternearly30yearsofdevelopmentandapplica-tion,theemergysynthesisapproachhasbecomeamorecommonandtestedevaluationmethodforecologicaleconomicsystemsandprocesses(BrownandUlgiati,2004a;HauandBakshi,2004),withspecialfocusontheagricultural?eld(LefroyandRydberg,2003;Castellinietal.,2006;Cavalettetal.,2006;Chenetal.,2006;Cohenetal.,2006;CuadraandRydberg,2006;Martinetal.,2006;Zhangetal.,2007;Laetal.,2008;DeBarrosetal.,2009).However,sofartherehavebeenonlyafewemergystudiesthatspeci?callyevaluate?sheryproductionsystems(Odum,2001;Zuoetal.,2004;Vassalloetal.,).AcarefulemergyevaluationoftheaquaculturesectorinChinacanbringupnewinsightsonthemanagementof?sheryproductionsystems,whichwouldprovidecomplementaryinformationonitsenvironmentalsustainabilityandindicatethepotentialforimprovement.Bothemergyandeconomicanalysismethodswereappliedtoevaluatethree?shfarmingsystems,i.e.,cage?shfarmingsystem,intensivepond?shrearingsystemandsemi-naturalextensivepond?shrearingsystem,inNansilakeareainthisstudy,toshedlightonthepotentialbene?tsofmoreeffectiveresourceuseandtosuggestappropriatemanagementpracticeswithregardtomain-tainingtheecosystemhealthofwetlands,basedonaoneyearinvestigationin2007.Thegoalsofthispaperare:(1)tocomparethedifferent?shfarmingsystemsinNansiLakeareawithregardtotheirresourceuse,productivity,environmentalimpactsandoveral(2)tounderstandtheextenttowhichintensivefarmingchoicesaredrivenbytheperspectiveofeconomicperformance,i.e.,localfarmer’spro?tasareturnoninvestment,withouttakingintoaccou(3)tohighlightimprovementsthatmighttranslateintoanincreaseoftheoverallenvironmentalandeconomicsustainabilityof?shfarminginlakewetlandareas.2.LocationandstudysitesNansiLake(SouthFourLakes),locatedinShandongProvinceChina,isthelargestshallowfreshwaterlakeinthenorthoftheChina(34??270à35??200N,116??84e117??210E),seeFig.1.Itconsistsoffoursub-lakes:Weishan,Zhaoyang,NanyangandDushan.Thetotalwatersurfaceis1266km2andtheaveragewaterdepthisonly1.5m.ThewholelakeisintheadministrativeareaofWeishanCounty,morethan70%ofwhichisoccupiedbythislake.Theareareceivesanannualaveragerainfallof870mm,andtheannualsolarradiationisabout5.00Et09J/m2.ItisimportanttonotethatpumpingstationsinNansiLakewillbeusedtocontrolwaterstorageandwatertransferintheEastLineProjectofWaterTransferfromSouthtoNorthinChina.However,waterqualityinNansiLakeispoor,duetointernalpollutionsources(aquaculture)andexternalloadingsources(untreateddomesticwastewater,industrialwastewaters,andagriculturalandurbanrunoff)fromthesurrounding31,000km2watershed.Sincethe1970s,aquaculturehasbeendevelopinginboththedikedandundikedwetlandsofNansiLakeintheformofpond?shfarming,pen?shculture,pencrabcultureand?shbreedinginthelake.In2008,theaquacultureareainWeishancountyreached2.13?104ha,ofwhichcage?shfarmingwas3.2?103ha,pen?shculturewas7.0?103haandpond?shfarmingwas1.05?104ha(WSSB,2009).Beforetheintroductionofthestudysites,itisnecessarytoexplaintherurallandusesystem,i.e.,theHouseholdResponsibilitySystem(HRS)inChina.Thissystemisbasedontwofeatures.First,allfarmlandisstillownedbythepublic.Second,productionandmanagementareentrustedtoindividualfarminghouseholdsthroughlong-termcontracts.Duringthecontractperiod,thefarmerspaytaxestotheStateanddelivercollectivereservestolocalgovernments,andkeeptheremainingproductandincomeforthemselves.Thecirculationoflanduserightisallowedintheformofrenting,becomingashareholderorotheractivities.Thethree?shfarmingsystemsanalyzedwerecage?shfarminginthelake,pond?shfarmingusinganintensivemodel,andpond?shfarminginasemi-naturalextensivestyle.Thestudysiteforthecage?shfarmingwasalakesurfaceof4hawithameandepthofabout2.5m,ownedbya?shfarmerundertheHRS,i.e.,thefarmerhastheuserightsfor50yearsgrantedbyacontractwiththeGovernment(Table1).Fiftycagesof?shwereplacedonstandingbamboopolesandmostoftheworkandmanagementwereperformedusingaboatpoweredbyadieselengine.Thevolumeofeachcageis200cubicmeters,i.e.,20m?5m?2m.Fishrearedinthissystemweresilvercarp(Hypophthalmichthysmolitrix)andspottedsilvercarp(Aristichthysmobilis).Thetotalnumberof?shintroducedwasroughly10004L.X.Zhangetal./JournalofEnvironmentalManagementxxx(mentionedabove,thispondwasalsoequippedwithaeratorpow-eredbyadieselengine,butwithoutaspreadingmachine,sinceitwasmainlyfedbygrassgatheredbythefamilyeveryday.The?shraisedinthispondwasgrasscarpandsilvercarpbutatmuchlowerdensitywithtotalof3000grasscarpsand900silvercarpsinthesystem.Forallthree?shfarmingsystems,?ngerlingswereintroducedintheearlyspringinMarch.ThewholegrowthperiodlastedabouteightmonthsfromMarchtoNovember.Allthe?sheswerecaughtformarketattheendofNovemberbeforethetemperatureofthewaterbecametoolow.Inaddition,bleachingpowderandtrichlorphonwereusedforwaterdisinfectionandpreventionofdiseases.3.MethodsBasedontheEnergySystemsLanguageintroducedbyOdum(1996),aggregatedsystemsdiagramsoftheaquaculturesystemsareshowninFig.2.Diagramsillustratetheirboundaries,theirmaincomponentsandinteractionsaswellasemergydrivingsourcesforthesystems.Thedifferentemergysourceswereaggregatedaslocallyrenewableresourceinput(R1),freerenewableresourceinputfromoutside(R2),locallynon-renewableresources(N),renewable(FR)andnon-renewable(FN)fractionsofgoodsandenergypurchasedfromoutside.Themaincharacteristicsofthesedifferentresourcesandemergy-basedindicesandratiosthatareusedtoevaluatethebehavioroftheinvestigatedproductionsystemsarelistedanddescribedinTable2.Duetorecentdevelopmentsofemergymethodology,thisworkincorporatessomechangesinemergyaccountingprocedures(Agostinhoetal.,2008).Thesechangesarethefollowing:(1)Thebiospherebaseline,i.e.,theglobalemergybudgetofthegeobiosphereforemergycalculationwasupdatedfromthepreviousvalue9.44Et24seJ/yr(Odum,1996)tothevalue15.83Et24seJ/yr(Odumetal.,2000),accordingtoacalculationprocedurethattakesintoaccountthecouplingbetweenthemaindrivingforces(solarradiation,geothermalheatandgravitationalpotentialenergy).Thus,tobeconsistentandtoallowcomparisonwitholdervalues,transformitiescalculatedusingtheoldbaselinehavebeenmultipliedby1.68(theratioof15.83/9.44)toobtaintheupdatedvalue.Nevertheless,theappropriatevalueforthebaselineisstillindispute(Campbell,2000;Campbelletal.,2005).Whatmattersisthepossibilitytocompareresultsobtainedfromdifferentbaselinesthankstotransparentcalculationprocedures.(2)Averagetransformityorspeci?cemergyofmanufacturedproductsarefrequentlyusedinspeci?ccasestudies,whichismostoftencriticizedassimplisticandinaccurate.Infact,theemergyembodiedintoanimportedproductismadeupwithtwoparts,oneisfromgeobiosphereworkandtheotheroneisfromservicesneededforitsproductionduringpreviousmanufacturingsteps.Whilethetechnologicalprocessesfortheproductionofagivengoodarebecomingday-by-daymoresimilarinaglobalizedplanet,importantdifferencesstillderivefromtheeconomicstructureoftheregionsorcountrieswheretheimportscomefrom,whichinturnaffectsthevalueoftheassociatedservices.Themoneypaidforaproductisinfact“buying”theserviceemergy.Therefore,thecalculationoftheemergyofimportsshouldproceedintwophases,usingthetransformitywithoutservicesandthenaddingtheemergyofservicesdeliveredwithinthespeci?ccountry.Servicesareamonetarymeasureoftheindirectlaborembodiedintheproductionanddeliveryofimportedgoodsandaremeasuredbythemoneyinvestedfortheirpurchase:asaconsequence,Fig.2.Summarydiagramoftheemergy?owsinthethree?shfarmingsystem.(a)cage?shfarmingsystem,(b)intensivepond?shfarmingsystem,(c)semi-naturalextensivepond?shfarmingsystem.Allemergy?owsare1014seJhaà1yearà1andthemoney?owsare$haà1yearà1.individualspercageperyear,ofwhich80%wassilvercarpand20%wasspottedsilvercarp.Thepondforintensive?shfarmingconsistedof0.4ha,withameandepthofabout2m.Thefarmerobtainedthelanduserightbypayingrent.Thissystemwascharacterizedbyentirelyrelyingoncommercialfeed,whichwassuppliedusingaspreadingmachine.Thefarmwasalsoequippedwithasystemforaerationinstalledinthewater,whichisusedwhenoxygenconcentrationfallsbelowathresholdlevelconsidereddangerousforthehealthofthereared?sh.Theelectricityforfeedingandaerationwasgeneratedbyanin-farmdieselenginegenerator.Thereared?shareprimarilygrasscarp(Ctenopharyngodonidellus),aswellassilvercarpandspottedsilvercarp.Thisproductionsystemwasmadeupofabout5000grasscarps,1800silvercarpsand300spottedsilvercarps.Thethirdsystemwaslocatedonanislandwithinthelakewithanareaof0.67haandmeandepthof3m.ThispondwasexcavatedbythefarmeronhisowncontractedcultivatedlandundertheHRS,sinceitwaslocatednearthelake.Similartothepond?shfarmL.X.Zhangetal./JournalofEnvironmentalManagementxxx(Table2Categorytotalsandindicescalculatedforthethree?shproductionsystemsunderstudy.IndexLocalrenewableemergyinputRenewableemergyinputfromoutsideLocalnon-renewableemergyRenewablefractionofpurchasedresourcesNon-renewablefractionofpurchasedresourcesTotalemergyusedEmergydensitySymbolorformulaR1R2NFRFNU?R1tR2tNtFRtFNED?U/areaDescriptionRenewable?owsdirectlyavailabletothearea,suchassolarradiation,windandrain.Freerenewable?owsfromoutsidetocage/pondarea,suchasplanktoninputalongwithwater?ow,andgrasscutforfeeding?sh.Includinglocalsoil,groundwater,andotherenvironmentalresourcesthatarenotreplacedwithinanannualcycle.Thefractionoftheemergyofimportedresources,thatisconsideredtobeofrenewableorigin.aThefractionoftheemergyofimportedresources,thatisconsideredtobeofnon-renewableorigin.aTotalemergy?owsneededtosupportaproductionsystem.aIntensityoftheemergyinvestedperunitarea.Itcanalsobedividedbythetime(seconds)andtranslateintoan“empowerdensity”(emergyperunitareaandtime)Theratiooftherenewableemergyinvesteddividedbythetotalemergydrivingthesystem.Thetotalemergyuseddividedbythetotalnetpro?t,i.e.,pro?tsminuscosts.Theratioofthetotalemergydrivingthesystem(andthereforeassociatedtotheoutput)andtheemergyinvestedfromoutside(andthereforetraditionallyconsideredasacost).Theindexmeasurestheemergyreturnontheemergyinvestment,i.e.,theabilityofaprocesstoexploitlocal(renewableandnon-renewablesources)byinvestingeconomicresourcesfromoutside.Ratioofnon-renewable(localandimported)emergyresourcestotherenewableemergy?ows,indicatingtheloadontheenvironmentgeneratedbyhuman-dominatednon-renewable?ows.Ratiooftheemergyembodiedinthemoneyreceivedtotheemergyembodiedintheproductexportedtooutsidemarket.Anindicatoroftheemergybene?tsorlossesfromthesaleofproducts.ItisthecompositeratiooftheemergyyieldratioEYRtotheenvironmentalloadingratioELR,indicatingtheprocesstrade-offbetweentheemergyadvantageprovidedbytheprocessanditsenvironmentalpressure.5RenewableemergyfractionEmergyinvestmentper$ofnetpro?tEmergyyieldratio%R?(R1tR2tFR)/UEIperNP]U/netpro?tEYR?U/(FRtFN)EnvironmentalloadingratioELR?(NtFN)/(R1tR2tFR)EmergyexchangeratioEER?[($income)*(seJ/$)country]/UEmergysustainabilityindexESI?EYR/ELRIncludestheemergyofservices,i.e.,theemergyassociatedwiththeindirectlaborrequiredoutsideofthesystemtomakeanddelivertheimportedresources(seeTable3to5).atheemergyassociatedtosuchanindirectlaboriscalculatedbymultiplyingtheemergytomoneyratioofthecountry(seJ/GDP)bythemoneypaidfor.Indoingso,thetotalemergyvaluecalculatedforaproductiscomposedofafractionthatismoreorlessthesameeverywhereanddependsontechnologyandafractionthatchangesdependingontheeconomicperfor-manceofthecountry(i.e.,theemergyneededtogenerateGDP).Suchvaluesaremoreaccurateandcanbeupdatedeasily(CuadraandRydberg,2006).(3)Therenewabilityfactorsofeachitemhavebeenconsideredaccordingtopreviousworks,forexample,Ulgiatietal.(1994),Ortegaetal.(2004),Ulgiatietal.(2005),Agostinhoetal.(2008)and(Luetal.,).Thisapproachcanberegardedasanimportantevolutionintheemergymethodology,representingaforwardstepinthedirectionofdescribingwithgreateraccuracythesustainabilityofcomplexsystems(Cavalettetal.,2006).Inotherwords,the?owsofmaterialsandservicesthatenterthesystemaremultipliedbytheircorrespondingrenewabilityfactors,inordertodividethemintheirrenewableandnon-renewablefractionsthatareusedforamoreaccuratecalculationoftheperformanceindicatorsthatdependontherenewabilityofsupporting?ows.(4)Thetransformityofthepolyculture?shwascalculatedbydividingthetotalemergyenteringthesystembythesumofenergiesofallproducts(BastianoniandMarchettini,2000),insteadofallocating100%ofthetotalemergyUtoeachspecies,consideredasaco-productoftheothers.Thisseemstobeabetterchoiceincaseswhereproductionisdiversi?ed,butremainsmoreorlesswithinthesametypologyofoutput.Moreover,threepointsregardingtheemergycalculationsper-formedinthispaperneedtobefurtherclari?ed.First,thegroundwaterpumpedforraisingpond?shhasbeenconsideredasanon-renewableresource,sincewaterisscarceinNorthernChinaasecond,thecage?shfarminginthelakesuffersfromdamagescausedby?oodandwaterpollutioneventsthatfrequentlyhappeninthisarea.Theriskcosthasalsobeenconsideredintheemergyaccountingframeworkinthisworkandariskcycleof5yearswasadoptedaccordingandthird,sinceoneyearwastakenasthetimescaleforthepresentanalysisofthethree?shfarmingsystems,allpiecesofequipmentandtoolsconsideredintheseproductionsystemswereconvertedtoannual?owsbasedontheirexpectedusefullifeandoperationperiodaccordingtolocalinvestigation.Followingthestandardmethodsofemergyanalysis,detailedemergyanalysistablesweresetupandcalculatedforeachsystemunderstudy(Table3,4and5)andrepresentedinaggregatedforminFig.2.Themarketvaluesforpurchaseditemscanbefoundintheservicespartofemergyanalysistablesforfurthercomparisonbetweenemergyandeconomicanalysis.Traditionalinputeoutputmethodwasadoptedforeconomicperformanceanalysisofthethree?shproductionsystem.Financialperfor-mancesofthedifferent?shfarmingsystemshavebeenassessedbyasetofeconomicindicatorscalculatedfromtheaverageresultsforeachtype.Theseeconomicindicatorswereeconomicinputeoutputratio,netpro?tandemergyinvestmentper$ofnetpro?t.4.Resultsanddiscussion4.1.EmergyaccountingAggregatedemergy?ows,aselectionofemergyevaluationindicesaswellassomeeconomicindiceswerecalculatedandpresentedinTable6.Fig.3showsthemainresourceinputsforthesethree?shfarmingsystems,re?ectingtheemergystructure(i.e.,the包含各类专业文献、幼儿教育、小学教育、专业论文、各类资格考试、中学教育、应用写作文书、Emergy evaluation and economic analysis of three wetland fish farming systems in Nansi Lake area, Ch17等内容。　}