現(xiàn)代化農(nóng)業(yè)

1、現(xiàn)代化農(nóng)業(yè)——真正可持續(xù)性農(nóng)業(yè)經(jīng)營(yíng)的生態(tài)影響和機(jī)遇ModernAgriculture:EcologicalImpactsthePossibilitiesfTrulySustainableFarming1.大約四十年前，農(nóng)業(yè)系統(tǒng)中的作物產(chǎn)量依賴的是內(nèi)部資源、有機(jī)物的循環(huán)利用、內(nèi)在的生物防治機(jī)制和將與模式。Untilaboutfourdecadesagocropyieldsinagriculturalsystemsdependedonint

2、ernalresourcesrecyclingofganicmatterbuiltinbiologicalcontrolmechanismsrainfallpatterns.2.農(nóng)業(yè)產(chǎn)量雖然不高，但比較穩(wěn)定。Agriculturalyieldsweremodestbutstable.3.保證產(chǎn)量的方法是在某一地塊的時(shí)空范圍內(nèi)多種幾類作物，以應(yīng)對(duì)突發(fā)的蟲(chóng)害或惡劣的天氣。Productionwassafeguardedbygrowingme

3、thanonecropvarietyinspacetimeinafieldasinsuranceagainstpestoutbreakssevereweather.4.為取得氨肥，采取輪換種植主要農(nóng)作物和豆類的方法。反過(guò)來(lái)，輪換種植可有效地破壞害蟲(chóng)、雜草、病害的生命周期，從而抑制它們。Inputsofnitrogenweregainedbyrotatingmajfieldcropswithlegumes.Inturnrotationss

4、uppressedinsectsweedsdiseasesbyeffectivelybreakingthelifecyclesofthesepests.5.玉米帶地區(qū)的普通農(nóng)場(chǎng)主輪換種植玉米和包括大豆在內(nèi)的幾種作物，而種植小粒谷物也是飼養(yǎng)牲畜的內(nèi)在需求。大部分勞動(dòng)由家庭成員完成，偶爾會(huì)請(qǐng)幾個(gè)幫手，但不會(huì)從農(nóng)場(chǎng)以外購(gòu)買專用設(shè)備或服務(wù)。在此類農(nóng)業(yè)系統(tǒng)中，農(nóng)業(yè)和生態(tài)的關(guān)系十分密切，很少會(huì)出現(xiàn)環(huán)境退化的跡象。Atypicalcnbeltfarm

5、ergrewcnrotatedwithseveralcropsincludingsoybeanssmallgrainoccasionalhiredhelpsospecializedequipmentserviceswerepurchasedfromofffarmsources.Inthesetypesoffarmingsystemsthelinkbetweenagricultureecologywasquitestrongsignsof

6、environmentaldegradationwereseldomevident.6.但隨著農(nóng)業(yè)現(xiàn)代化的發(fā)展，對(duì)生態(tài)法則的無(wú)視和踐踏經(jīng)常會(huì)打破生態(tài)——農(nóng)業(yè)鏈。Butasagriculturalmodernizationprogressedtheecologyfarminglinkagewasoftenbrokenasecologicalprincipleswereignedoverridden.7.事實(shí)上，有些農(nóng)業(yè)科學(xué)家已經(jīng)一致地認(rèn)為

7、現(xiàn)代農(nóng)業(yè)面臨著環(huán)境危機(jī)，也有越來(lái)越多的人關(guān)注現(xiàn)存的食品生產(chǎn)系統(tǒng)是否能長(zhǎng)期持續(xù)發(fā)展。Infactseveralagriculturalscientistshavearrivedatageneralconsensusthatmodernagricultureconfrontsanenvironmentalcrisis.Agrowingnumberofpeoplehavebecomeconcernedaboutthelongtermsusta

8、inabilityofexistingfoodproductionsystems.8.累積成堆的證據(jù)也表明，盡管目前的資本密集型和技術(shù)密集型農(nóng)業(yè)系統(tǒng)的生產(chǎn)力和競(jìng)爭(zhēng)力非常頑強(qiáng)，但也帶來(lái)了一系列經(jīng)濟(jì)、環(huán)境和社會(huì)問(wèn)題。Evidencehasaccumulatedshowingthatwhereasthepresentcapitaltechnologyintensivefarmingsystemshavebeenextremelyproduct

9、ivecompetitivetheyalsobringavarietyofeconomicenvironmentalsocialproblems.9.證據(jù)還表明，農(nóng)業(yè)結(jié)構(gòu)和通行政策傾向于發(fā)展大型農(nóng)場(chǎng)、專業(yè)化生產(chǎn)、農(nóng)作物單一在中和機(jī)械化，這些做法本身導(dǎo)致了這種環(huán)境危機(jī)。Evidencealsoshowsthattheverynatureoftheagriculturalstructureprevailingpolicieshaveledt

10、othisenvironmentalcrisisbyfavinglargefarmsizespecializedproductioncropmonoculturesmechanization.10.如今，越來(lái)越多的農(nóng)場(chǎng)主融入了跨國(guó)經(jīng)濟(jì)體，多種栽種的必要性不復(fù)存在，單一栽種模式則可以從規(guī)模經(jīng)濟(jì)取得回報(bào)。反過(guò)來(lái)，缺少輪作和多種栽種會(huì)導(dǎo)致重要的自我調(diào)節(jié)機(jī)制小時(shí)，從而使單作系統(tǒng)脆弱不堪，變?yōu)橐詠?lái)高濃度化肥的農(nóng)業(yè)生態(tài)結(jié)構(gòu)。Todayasmemef

11、armersareintegratedintointernationaleconomiesimperativestodiversitydisappearmonoculturesarerewardedbyeconomiesofscale.Inturnlackofrotations回農(nóng)田也會(huì)遇到同樣的困難。Inmanyareasagriculturalwastehasbecomealiabilityratherthanaresource.R

12、ecyclingofnutrientsfromurbancentersbankstothefieldsissimilarlydifficult.22.農(nóng)業(yè)生態(tài)系統(tǒng)不穩(wěn)定和易患病蟲(chóng)害的部分原因就是廣泛采用了作物的單一栽種模式。因?yàn)檫@種模式集中了有利于專門的作物害蟲(chóng)生長(zhǎng)的資源，而且擴(kuò)大了病蟲(chóng)害遷徙的空間。這種簡(jiǎn)單化的模式還降低了在自然環(huán)境中產(chǎn)生天敵的可能。Partoftheinstabilitysusceptibilitytopestsof

13、agroecosystemscanbelinkedtotheadoptionofvastcropmonocultureswhichhaveconcentratedresourcesfspecialistcropherbiveshaveincreasedtheareaavailablefimmigrationofpests.Thissimplificationhasalsoreducedenvironmentalopptunitiesfn

14、aturalenemies.23.結(jié)果，當(dāng)大量病蟲(chóng)害遷移、益蟲(chóng)數(shù)量減少、氣候條件適宜、作物處于抵抗力較弱階段這些因素同時(shí)作用的話，往往就會(huì)爆發(fā)病蟲(chóng)害。Consequentlypestoutbreaksoftenoccurwhenlargenumbersofimmigrantpestsinhibitedpopulationsofbeneficialinsectsfavableweathervulnerablecropstageshappe

15、nsimultaneously.24.由于種植某些作物超出了它們的“自然”范圍，或從適宜生長(zhǎng)的地區(qū)擴(kuò)張到病蟲(chóng)害高發(fā)、水源有限或土壤肥力低下的地區(qū)，就需要使用高強(qiáng)度的化學(xué)物以克服這些制約因素。人們以為，人工干預(yù)和促成這些擴(kuò)張的能量輸入水平可以無(wú)限制地維持下去。Asspecificcropsareexpedbeyondtheir“natural”rangesfavableregionstoareasofhighpestpotentialwi

16、thlimitedwaterlowfertilitysoilsintensifiedchemicalcontrolsarerequiredtoovercomesuchlimitingfacts.Theassumptionisthatthehumaninterventionlevelofenergyinputsthatallowtheseexpansionscanbesustainedindefinitely.25.在經(jīng)濟(jì)農(nóng)場(chǎng)主面前，新的

17、作物品種走馬燈似地更迭不盡，這是由于生物壓力和市場(chǎng)變化引起的品種更替達(dá)到了前所未有的速度。Commercialfarmerswitnessaconstantparadeofnewcropvarietiesasvarietalreplacementduetobioticstressesmarketchangeshasacceleratedtounprecedentedlevels.26.一個(gè)病蟲(chóng)害抵抗力加強(qiáng)的品種初次亮相后可以登臺(tái)數(shù)年（通

18、常是5至9年），如果產(chǎn)量滑坡、生產(chǎn)力面臨問(wèn)題、或出現(xiàn)了更好的品種，它就得被另一品種取代。Acultivarwithimproveddiseaseinsectresistancemakesadebutperfmswellfafewyears(typically59years)isthensucceededbyanothervarietywhenyieldsbegintoslipproductivityisthreatenedameprom

19、isingcultivarbecomesavailable.27.一個(gè)品種的運(yùn)動(dòng)軌跡可描述為：被人采用時(shí)處于起飛階段，栽種情況穩(wěn)定后進(jìn)入中間階段，最后是栽種面積的萎縮。Avariety’strajectyisacterizedbyatakeoffphasewhenitisadoptedbyfarmersadlestagewhentheplantedareastabilizesfinallyaretractionofitsacreage.

20、28.因此，要保持現(xiàn)代農(nóng)業(yè)的穩(wěn)步發(fā)展，依賴的是不斷供應(yīng)新的作物品種，而不是拼拼湊湊地在同一個(gè)農(nóng)場(chǎng)種上不同的作物。Thusstabilityinmodernagriculturehingesonacontinuoussupplyofnewcultivarsratherthanapatchwkquiltofmanydifferentvarietiesplantedonthesamefarm.29.如果要維持單一栽種模式，就得增加殺蟲(chóng)劑和化肥

21、的使用量，但使用過(guò)的藥劑效力正在降低，多數(shù)重要作物的產(chǎn)量也漸趨平穩(wěn)。甚至在某些地區(qū)，產(chǎn)量實(shí)際上已經(jīng)下滑。對(duì)于這種現(xiàn)象背后的原因眾說(shuō)紛紜。Theneedtosubsidizemonoculturesrequiresincreasesintheuseofpesticidesfertilizersbuttheefficiencyofuseofappliedinputsisdecreasingcropyieldsinmostkeycropsar