基于景观角度农业生态系统的可持续发展综述.docx
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基于景观角度农业生态系统的可持续发展综述.docx
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基于景观角度农业生态系统的可持续发展综述
ResearchArticle
Alandscapeperspectiveonsustainabilityofagriculturalsystems
Abstract
Agriculturalsustainabilityconsiderstheeffectsoffarmactivitiesonsocial,economic,andenvironmentalconditionsatlocalandregionalscales.Adoptionofmoresustainableagriculturalpracticesentailsdefiningsustainability,developingeasilymeasuredindicatorsofsustainability,movingtowardintegratedagriculturalsystems,andofferingincentivesorimposingregulationstoaffectfarmerbehavior.Landscapeecologyisaninformativedisciplineinconsideringsustainabilitybecauseitprovidestheoryandmethodsfordealingwithspatialheterogeneity,scaling,integration,andcomplexity.Tomovetowardmoresustainableagriculture,weproposeadoptingasystemsperspective,recognizingspatialheterogeneity,integratinglandscape-designprinciplesandaddressingtheinfluencesofcontext,suchastheparticularproductsandtheirdistribution,policybackground,stakeholdervalues,location,temporalinfluences,spatialscale,andbaselineconditions.Topicsthatneedfurtherattentionatlocalandregionalscalesinclude
(1)protocolsforquantifyingmaterialandenergyflows;
(2)standardspecificationsformanagementpracticesandcorrespondingeffects;(3)incentivesanddisincentivesforenhancingeconomic,environmental,andsocialconditions(includingfinancial,regulatoryandotherbehavioralmotivations);(4)integratedlandscapeplanningandmanagement;(5)monitoringandassessment;(6)effectsofsocietaldemand;and(7)integrativepoliciesforpromotingagriculturalsustainability.
Keywords
ContextFarmIncentivesIndicatorsScaleSpatialheterogeneitySystems
Introduction
Agricultureistheoldestwayinwhichhumansinteractwithnaturalsystems,particularlythroughalterationoflandforcropandlivestockproductionandtheredirectionofenergy,nutrients,water,orbiomassflowstowardshumanconsumption.Aspeoplebegantoalterthelandtoproducefood,fiber,andfuel,theseactivitiesstartedaprocessinwhichsettlementpatterns,land-managementpractices,cropselection,animalproduction,andlandscapeheterogeneityinfluencedeachotherovertimeinacontinuousprocessofadjustmentanddevelopment.
Currentestimatesofcroplandandpasturevarybetween24and38%oftheEarth’sland.Cropproductionoccursonabout1500millionhaoftheEarth’slandsurface[FAO(FoodandAgricultureOrganization)2012a].Thisareaincludesarablelandandlandunderpermanentcropsandisabout30%ofthelandestimatedtobesuitableforrain-fedcropproduction[FAO(FoodandAgricultureOrganization)2003].Worldcropproductionisexpectedtoincreaseprimarilythroughcropintensificationcomplementedbytheongoingreallocationoflandusesandexpansionofarableland.Somestudiessuggestthatincreasingproductiontofeedtheworldin2050couldbeachievedbyclosing“yieldgaps”(e.g.,Lobelletal.2009;Sánchez2010;Foleyetal.2011;Muelleretal.2012).Forexample,yieldof17majorcropscouldbeincreasedby45–75%ifalllandsplantedtothosecropsachievedcurrentattainablelevels(Muelleretal.2012).Tofeedtheworldin2050,theFoodandAgricultureOrganizationprojectedarablelandareacouldincreasebyabout5%astheresultofexpansioninthedevelopingworldof120millionhaandalossof50millionhaindevelopedcountriesforanetexpansionof70millionha[FAO(FoodandAgricultureOrganization)2010].About90%oftheanticipatedgrowthincropproductionisexpectedtoresultfromhigheryieldsandcroppingintensities[FAO(FoodandAgricultureOrganization)2010].Changesinclimate,disturbanceregimes,markets,managementandotherfactorswillaffecttheproductionandlocationofagriculturalsystemsandadduncertaintytofutureprojections.
Agriculturalsystemshaveexpandedandcontractedinresponsetotheneedsofagrowingpopulationandbybecomingspecializedforspecificregionswithfavorablesoilsandweatherconditions,suchasriceinlowlands,sugarcaneinBrazilandmaizeintheUnitedStates.Water-managementpracticesincludeirrigationanddrainage.Largeareasofthelandscapeswithrain-fedagriculture,liketheuppermidwesternUnitedStatesorlow-lyingregionsofnorthernEurope,aredrainedtoremoveexcesswater,whileMediterraneanandaridlandscapesaroundtheworldrequireirrigationforintensiveproduction.Someagriculturalpracticesaresimilartothoseemployedhundredsoreventhousandsofyearsago.Forexample,cultivationofMayangardensbasedonancientfarmpracticescontinuestosustainproductioninsomeregionsofCentralAmericatoday(e.g.,shiftingcultivationandparticipatoryland-useplanning)(Dalleetal.2011).
Increasedhumanpopulationhasplacedgreatpressureonagriculturebyincreasingdemandforfood,feed,fiberandenergyandbydisplacingsomeofthebestagriculturalsoilsforotheruses.Farmlandcontinuestobedivertedtourbanandsuburbandevelopment,industrialexpansion,transportationnetworks,watermanagement,biodiversity,leisure,tourismandotherdemands.Akeyquestionforsustainingagricultureishowtomeetthegrowingdemandforprimaryproductswhileretainingorevenenhancingecosystemservices(MillenniumEcosystemAssessment2005;Muelleretal.2012).Manyoftheseservicesarerelatedtoprocessesoccurringatscalesmuchlargerthanthatofafarm:
preservationofwaterquality,pollinationbynon-domesticatedbeespecies,nutrientretentioninlandscapes,soilretention,carbonsequestration,floodcontrol,sustainedwateryield,andbiodiversityconservation(Smithetal.2012).Enhancementordegradationofenvironmentalconditionscanaffectagriculturalproductivity(DaleandPolasky2007)and,asaconsequence,agriculturalsustainability.
Agriculturalsustainabilityissues
Definingagriculturalsustainability
Agriculturehasmuchtogainfromthescienceofsustainability,whichfocusesexplicitlyontheinteractionbetweennatureandsociety(Wu2006).Sustainabilitycanbeaphilosophyorideology,asetofstrategies,thecapacitytofulfillasetofgoals,ortheabilitytocontinuemakingimprovementsovertimeunderchangingconditions(Hansen1996).Itcommonlyreferstopracticesthatareenvironmentallysound,economicallyprofitable,andsociallyjust.Howthesepracticesaredefinedandbalancedreflectssociety’sprioritiesandtherefore,definitionsmaychangewithtimeandcircumstances.Reachingagreementontradeoffstoachievenoneconomicsustainabilitygoalsremainsachallenge(Kareivaetal.2007).Devisingcost-effectivemeanstomeasure,monitor,andassesstherelativesustainabilityassociatedwithdifferentcomponentsofheterogeneousagriculturalsystems,andtheinteractionsamongthesecomponentsandbroaderlandscapesovertime,makesitdifficulttoreachdefinitiveoruniversalconclusionsabout“bestpractices”formoresustainableagriculture.
Thedefinitionofagriculturalsustainabilitydependscriticallyontheboundaryconditionsestablishedfortheanalysis(Hansen1996).Atafieldscale,changesinenvironmentalconditionsareoftenthefocus.Atthefarmlevel,profitmarginsandtheconsumptionandproductionofresourcesareoftenthefocus.Atthelargersocialorpolicyscale,concernmayexistforeconomicefficiency,equity,orthedistributionofcostsandbenefits.Thecharacterizationofagriculturalsustainabilityfurtherdependsoncontextualconsiderations,suchasthepurposeofanalysis,theproductionanddistributionsystem,policyconditions,stakeholdervalues,location,temporalinfluences,spatialscale,baselines,andreferencescenarios(Efroymsonetal.inpress).Herewetakealandscapeecologicalperspectiveinconsideringsustainabilityofagriculturalsystems.
Considerationofagriculturalsustainabilitymustderivefromtheobjectivesofagriculturetoprovideanadequatefood,fiber,andfuelsupplyfortoday’spopulationwithoutjeopardizingthecapacitytoprovidethesameservicestofuturegenerations.Agriculturemayinvolveadditionalobjectives:
providingahigh-qualitydietforallpeopleatareasonableprice,maintainingfarmers’income,maintainingthenatural-resourcebaseoffarmsystems(e.g.,soilquality),andmaintainingthesupportingandprovisioningfunctionsofecosystems.Farmingobjectivesmustbemetwithinspecificconstraintsderivedfromlocalandvaryingagro-ecological,economic,andsocialconditions.
Resourcemanagementoptionsassessedintermsofspecificaspectsofsustainabilitycangeneratedivergentoutcomes.Forexample,modernbeefproductionpresentschallengesinprovidingproteinsustainablybecausetherearelargeinefficienciesandenergylossesinfeedinggraintolivestocktoproducebeefcomparedwithfeedinggrainstootheranimalssuchaspoultryordirectlytohumans(Horriganetal.2002;Foley2011).Butanimalproductioncanalsocontributetooverallsystemsustainability,forexample,byusingruminantlivestockthatpreferperennials(Janzen2011;Schiereetal.2002),incorporatinganimalsinorganicfarmingsystems(KaffkaandKoepf1989),feedingpost-consumerfoodwastestoanimals,andusinglowqualityresourcesforanimalfeedsuchasresiduesfromthefoodprocessingindustry,grainthatfailstomeetmarketstandardsforhumanconsumption,anddrieddistillersgrains(DDGs)thatareabyproductofcornethanolproduction(Swanepoeletal.2010).Optimalconditionsforachievingdifferentobjectivescanbedefinedforeachlevelofanalysisbutarenotlikelytobeconsistentacrossdifferentscalesofanalysis.
Measuringsustainability
Developingeffectiveandcost-efficientmethodstomeasuresustainabilityrequires
(1)selectionofalimitedsetofindicators;(2
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