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wild.However,thoserelativesmightbealteredsuchthattheynowhaveacompletelynewecological
role,causingthemto“outcompete”otherspeciesintheecosystem.AnotherwayinwhichGMcrops
mightharmbiodiversityrelatestotheuseofonlyasmallnumberofcropvarieties.Newcharacter-
isticsthatoccurfromgeneticmodiicationcouldbesoadvantageousthatonlyafewcropvarieties
areused.Inturn,therecouldbeagreaternumberofoutbreaksofdiseaseorpests.Inaddition,any
cropthatisengineeredtoberesistanttopestsorherbicidescaninluencebiodiversity,becauseit
maynotonlyaffectthetargetinsectbutcouldalsobeharmfultoinsectsthatarenottargetsbutstill
consumethecrop.
Thusfar,thereissomeevidencetosuggestthatGMcropscanharmbiodiversity.Whenmon-
archbutterliesfeedonleavesthatarecoveredinpollenfromGMcorn,theirgrowthwasslower,
andtheyweremorelikelytodie.AnotherstudythatinvestigatedpinkbollwormthatfedonGM
cottonfoundsimilarresults.However,follow-upexperimentsonmonarchbutterliesfoundthatbio-
diversitywasnotharmed,indicatingthatmoreresearchneedstobeperformed(Searsetal.2001).
AnotherstudyinvolvedaphidsthatconsumedGMpotatoes.Accordingtothestudy,GMnematode
resistancewasmorecompatiblewithaphidbiologicalcontrolthanasystemicnematicidetreatment;
however,thefoodwasfoundtohaveadetrimentaleffectonladybirdsthatfedonaphids.Therefore,
itwassuggestedthattheconsequencesofcommercialcultivationofGMnematode-resistantplants
foraphidnaturalenemiesandfoodwebstructureneedstobedetermined(Cowgilletal.2004).
Itisnoeasytasktoencouragebiotechnologicaldevelopmentandprogresswhilestillrespecting
biodiversityandtheenvironment.Itis,however,anecessarytaskthatmustbedoneifGMfoodsare
tohaveanylong-termsupportworldwide.Oneimportantstepistoobtainabetterunderstandingof
theecologyofaspeciicareapriortoplantingaGMcrop.Itisalsodificulttocreateexperiments
thatexaminetheimpactofGMcropsonbiodiversity,butthisisachallengethatmustbemetif
biodiversityistoberespected.
Uptonow,thereisnoevidencethattheGMplantshavecausedenvironmentalproblems(Raven
2010;PhippsandPark2002);however,eachnewGMvarietyneedstobecloselyexaminedastoits
environmentalimpact.Therefore,issuesofconcerntobetakenintoaccountincludethecapability
of the GMO to escape and potentially introduce the engineered genes into wild populations, the
persistenceofthegeneaftertheGMOhasbeenharvested,thesusceptibilityofnontargetorgan-
isms(e.g.,insectsthatarenotpests)tothegeneproduct,thestabilityofthegene,thegenetransfer
tomicroorganisms,thereductioninthespectrumofotherplants,includingthelossofbiodiversity,
andtheincreaseduseofchemicalsinagriculture.Inaddition,theenvironmentalsafetyaspectsof
GMcropsvaryconsiderablyaccordingtolocalconditions.
Inlinewiththeabove-mentionedconcerns,currentinvestigationsfocusonthepotentiallydet-
rimental effect on beneicial insects or a faster induction of resistant insects (O'Callaghan et al.
2005),thepotentialgenerationofnewplantpathogens(DunieldandGermida2004;Giovannettiet
al.2005),thepotentialdetrimentalconsequencesforplantbiodiversityandwildlifeandadecreased
useoftheimportantpracticeofcroprotationincertainlocalsituations(Löveietal.2010),andthe
movementofherbicide-resistantgenestootherplants(Frisvoldetal.2009;DukeandPowles2009).
Asmentionedabove,environmentalissuesaredificulttohandle,relatedhazardsaredificult
topredict,anddespitetheoverallpositiveexperiencesofar,acase-by-caseapproachshouldbefol-
lowedconcerningthesafetyissues.Furthermore,astheenvironmentalsafetyaspectsofGMcrops
vary considerably according to local conditions, continuous follow-up should be applied on this
basis.
Theexampleofthedevelopmentofherbicide-tolerantweedsprovidesargumentsfortheadop-
tionofthispractice(Frisvoldetal.2009;DukeandPowles2009):weeds,alongwithinsectpests
andplantdiseases,aresourcesofbioticstressincropsystemsthatreduceyields,raiseproduction
costs,andcontributetoincomerisktofarmers.Transgenic,herbicide-resistant(HR)cropvariet-
ies,irstintroducedin1996,offerthepromiseofmoreeffectiveweedcontrol.By2008,morethan
79millionhaworldwidewasplantedHRvarietiesofsoybean,maize,canola,cotton,alfalfa,and
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