EnvironmentalImpactsofCannabisCultivationinCalifornia

MariahPonce

ENVS190

May17,2018

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TableofContents

Abstract………………………………………………………………………………………….…………….…3

Introduction………………………………………………………………………………………………….3-5

CannabisLifeCycle………………………………………………………………………………………..5-6

Water…………………………………………………………………………………………………………...6-9

A) Overuse…………………………………………………………………………………………..7

B) Diversions…………………………………………………………………………………….8-9

Energy…………………………………………………………………………………………………………9-12

Soil…………………………………………………………………………………………………………….13-14

Air…………………………………………………………………………………………………………….14-16

PesticideUse………………………………………………………………………………………………16-18

ImpacttoWildlife………………………………………………………………………………………..18-21

FishSpecies…………………………………………………………………………………………………21-22

SiteLocation……………………………………………………………………………………………….22-25

Conclusion………………………………………………………………………………………………………25

Figures&Tables…………………………………………………………………………………………25-30

WorkCited…………………………………………………………………………………………….……31-36

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Abstract

Marijuana(Cannabisspp.)isawaterintensiveplantthatrequires22.7liters

ofwateradayperplanttogrow.Onaverage,outdoormarijuanasitesrequire

nearly430millionL/km2ofwaterforproduction.Wateruseassociatedwith

marijuanaproductionhascausedproblemsforpopulationsofCaliforniatroutand

salmonpopulations.Estimationsindicatethatindoorcannabisproductionaccounts

for3percentofCalifornia’selectricityuseandcreatesnearly3poundsofcarbon

dioxideforasinglecannabiscigarette.Cannabiscultivationsitesarealsoassociated

withlandclearingsandpesticideuse,allofwhichthreatenwildlifesuchas

CaliforniaPacificFishers.Asthelegalizationofrecreationalmarijuanausebeginsto

expandthemarketforcannabisproductioninCalifornia,theconstraintsonthe

environmentcontinuetoincrease.Thereisneedforbetter,morein-depthresearch

toprovideinformationforpoliciesandregulationsthatwillhelpoffsetthe

environmentalproblemsassociatedwithmarijuanacultivation.

Introduction

IntheUnitedStates,Cannabisspp.isarisingagriculturalcropthatplaysan

importantroleintheboththeeconomyandenvironment(Carahetal.2015).Legal

marijuanamarketsareworthnearly$8billionandareprojectedtogrowupwardto

$21billionby2020(Carahetal.2015).Currently,Californiaproducesandsupplies

approximately80percentofthelegalandillegalmarijuanaandisconsideredthe

largestdomesticproducerwithintheU.S.(Short-Gianottietal.2017).TheNorth

CoastalBasinofCalifornia,whichincludesHumboldt,Trinity,andMendocino

Counties,contributesroughly$2to$4billionworthofmarijuanatothecountry’s

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overalleconomy(Short-Gianottietal.2017).Asthemarketforcannabiscontinues

toexpandinCaliforniaduetothelegalizationofrecreationaluse,thedemandon

naturalresourcesintensifies.

InNovemberof2016,Proposition64,theAdultUseofMarijuanaAct(AUMA)

waspassed,whichlegalizedrecreationalcannabissalesinCaliforniaasofJanuary1,

2018(Nevius2015).Withthelegalizationofrecreationalmarijuana,production

siteshavebegantomovefurthersouthintotheCentralValleyinordertokeepup

withanexpandingmarket.TheCentralValley’ssoiltype,geography,andabundant

suncreateidealgrowingconditionsforcannabisproduction(Carahetal.2015).

However,theareaseverelylackswater(Carahetal.2015).Cannabisisawater

intensivecropandinordertomeetthedemandsofirrigation,waterhasbeen

divertedthroughillegaldamming(Baueretal.2015).Diversionsandintensive

waterdemandshaveresultedinreducedflowsandcompletelydewateredstreams

(Baueretal.2015).Watershedshavealsobeenpollutedbypesticideandherbicide

runofffromcannabisproduction(Gabrieletal.2013).Soilshavebeendegradedby

illegallandclearingandloggingwhichhascausedrunoffandaneedforimporting

sediment(Wangetal.2017).Cannabisproductionandtransportationisalsoenergy

intensiveandhascausedairpollutionincludinghighlevelsofcarbondioxide

emissions,nitrousoxides,andairbornefungalspores(Mills2012).These

environmentalimpactsofcannabiscultivationalsoseverelyhindersurrounding

wildlifeandfishandareprojectedtointensifyasthemarketandproduction

expandsasaresultofitscurrentlegalstatus(Gabrieletal.2015).

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Althoughcurrentresearchpointstoextremeenvironmentaldamage,the

assessmentoftheeffectsofcannabisproductionishinderedbylackofquantityand

quality.Thequasi-legalstatusofmarijuanahasledtoalackoffundingforresearch

andhasthusledtoanecdotalresearchthatisbasedoffofillicitproductionsites

(AshworthandVizuete2017).Lackofresearchforlegalmarijuanaproductionhas

ledtopoliciesbeingbasedoffofpopularmediaspeculationandpoorlyreferenced

andreviewedliterature(Babcock2017).Anassessmentoftheenvironmental

effectsofcannabiscultivationisneededthatisbasedoffofreliableresearch.An

analysisofwheretheresearchislackingandhowitcanbeimprovedisalsoneeded

(Carahetal.2015).

Thispaperincludesaliteraturesearchofpeerreviewedscientificliterature

inordertoevaluatetheenvironmentalimpactsofcannabiscultivation.These

impactsincludeathoroughanalysisofnaturalresourcedemandssuchas,water,

energy,soil,andair,alongwitheffectsonfishandwildlife.Thefollowingdatabases

wereutilized:PubMed,WebofScience,andEBSCO.Booleansearchtermsincluded;

marijuana/cannabisgrowsoperationsandenvironmentalimpactsonsoil,water

demand/use,energy,pollution,andeffectsonfishandwildlife.Over200articles

werereviewedforrelevancyandqualityand33wereselected.Iintendtousethe

selectedarticlestoidentifywheremorein-depthanalysisorresearchisneededso

thatdecision-makingbypolicymakerscanbeimproved.

CannabisLifeCycle

CannabisgrowsannuallyforoneseasonduringthemonthsofOctoberto

April.Therearesixstagesintheherbslifecycle.Thefirststage,germination,can

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taketwelvehourstoninedaystoproducearootandrequiresmoistureandwarmth.

Optimaltemperaturesrangefrom75to86degreesFahrenheit(Laursen2015).The

germinationstageisthenfollowedbyseedling.Thisstageoccursforonetofour

weeksandischaracterizedbyleafemergence(Laursen2015).Vegetationisthe

thirdstagethatoccursduringthesummermonthsandrequiressubstantial

nutrientsandlight.Theplantbeginstoformthickerstemsandbranchesand

increasesinsize(Laursen2015).Vegetationisthenfollowedbythepre-flowering

stage,whichoccursinautumn.Here,theplantrequirestwelvehoursoflight

exposureandtwelvehoursofdarkness.Thisstageoccursfortentofourteendays

andincludesnodegrowth,whichwilleventuallyformeithermaleorfemaleflowers

(Laursen2015).Theplantalsobeginstodoubleinsize.Next,thefloweringstage

occursandcanlastsixtotwentytwoweeks(Laursen2015).Flowersbeginto

produceandthesexoftheplantcanbeidentified.Thelaststage,seedproduction,

occurswhenmalesacksopenanddroppollenandwhenfemaleseedsareformed

andpollinated,thusre-startingthelifecycle(Laursen2015).

Water

California’sdiversegeography,soil,andclimatehavemadeitanideal

locationforcannabiscultivation.ForyearsillegalgrowershaveusedNorthern

California’slandscape,richsoils,andconstantwatersupplytoconductgrowing

operations(Slater2017).Duetounregulatedcannabisproduction,theNorthern

Californiaregionhasexperiencedsevereenvironmentalimpacts. Northern

California’sMediterraneanclimateconsistsofwet,coolwinterswithapproximately

95percentofprecipitationoccurringbetweenthemonthsofOctoberandApril

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(Baueretal.2015).Thesummermonths,MaythroughSeptember,whichcoincide

withMarijuana’sgrowingseason,oftenexperiencedroughtandprovidenegligible

amountsofprecipitation(Baueretal.2015).Asaresult,waterstorage,diversions,

andconveyancehavebeenconstructedtomeethighwaterdemandsalthough

availabilitymaybescarce.Thishascompoundedperiodsoffloodanddrought,

whichhasseverelyimpactedthesurroundingecosystems(Bauss2017).Water

diversionsforagriculturalirrigationaccountsforupto80percentoftotalhuman

wateruseinCalifornia’sMediterraneanregion(Carahetal.2015).Marijuana

productioncontributestotheexcessivewateruseparticularlyfromstreamand

riverdiversion(Baueretal.2015).Theamountofwateruseforcannabiscultivation

hasthusfargonemainlyunregulated.Asaresult,reducedwaterflowshavecaused

ecologicalproblemssuchaschangingthequalityofaquatichabitat,reducing

dissolvedoxygenlevels,andincreasingwatertemperatures.Allofwhichaffect

abundanceanddiversityoffishspeciesandinvertebrate(Bauss2017).Integrated

watermanagementapproachesareneededtoproperlyallocatewaterforboth

humanuseandfortheconservationoffreshwaterecosystems.

Wateroveruse

Onaverage,outdoormarijuanasitescanproduce130,000plantsperkm2

(Carahetal.2015).Cannabisrequires22.7litersofwateradayperplanttogrow

(Baueretal.2015).UsingawaterapplicationrateproducedbyBaueretal.(2015),

anaverageoutdoorsiterequiresnearly430millionL/km2ofwaterformarijuana

production.Incomparison,winegrapes,anotherwaterintensiveplantgrownin

NorthernCalifornia,requirenearly13litersofwaterperdayandaverage271

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millionL/km2ofwaterforproduction(Hale,2017).Inordertofulfillthedemandof

waterformarijuanaproduction,extensiveamountsofirrigationwaterareused

(Baueretal.2015).

Diversions

Duetonegligiblelevelsofprecipitation,cannabiscultivationsitesareoften

locatedonlandnearreliablesourcesofsurfacewater.Often,cultivatorsacquire

waterforirrigationbydivertingspringsandheadwaterstreams(Granthametal.

2010).Astudythatexaminedtheimpactofwateruseon40differentindoorand

outdoorcannabiscultivationsitesin4differentwatershedsacrosstheNorthern

Californiaregionfoundthatmostsiteswerelocatedinareasthatcontainhighly

sensitivewatersheds(Baueretal.2015).Upto32,000plantswereestimatedper

watershed(Baueretal.2015).Usingthewaterapplicationrate,waterdemands

rangedupto32,000litersperdaywitheachparceloflandusingnearly5,000liters

perday(Figure1).Allfouroftheevaluatedwatershedshadminimumstreamflow.

Theirrigationneedsofthreeofthefoursystemsexceededthesummerlow-flow

periodsandrangedinwaterdemandsbetween34to100percentofflow(Figure1).

Thefourthwatersheddifferedbyhavinggreaterannualmeanprecipitationand

lowerlevelsofevapotranspiration(Baueretal.2015).

ThefindingsproducedbyBaueretal.(2015)werebasedoffofsmallpumps

predictedtobeoperatingatstandardpumpingrate.Ifmorethanonepumpwas

operatedatoncethestreamscouldbedewatered.Oncestreamsaredewateredby

diversionsornaturallyrundry,growersusewaterstoredearlierintheyearuntil

supplieshavebeenexhausted.Groundwateristhenusedfromwellsandimported

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tocannabissitesbytrucks(AshworthandVizuete2017).Theamountofwaterused

byimportsandwetseasonstoragehasnotyetbeendeterminedordocumented

(Baueretal.2015).

AttemptshavebeenmadetousedatacollectedbytheStateWaterResources

ControlBoard(SWRCB),inordertopredicttheoverallimpactofsmallsurface

waterdiversionsonwatershedsinNorthernCalifornia.TheSWRCBisthe

responsibleagencyforadministeringwaterrights(Carahetal.2015).Lessthan6

percentoftheactivewaterdiversionsareregisteredandonfilewiththeSWRCB

(Baueretal.2015).Thus,theunregistereddiversionsarenotsubjugatedto

standardsorregulationssetbytheCaliforniaDepartmentofFishandWildlifeand

thereforetheimpactofwaterdiversionsforcannabisuseiswidelyunknown.

Energy

InCalifornia,marijuanaproductionrequiresasubstantialamountofenergy.

Estimationsindicatethatindoorcannabisproductionaccountsfor3percentof

California’selectricityuse,whichistheequivalenttomorethanamillionCalifornia

homesandcostaround3billiondollarsperyears(Mills2012).Marijuana

productionemissionsarenearlyequaltothatofamillioncars(Mills2012).Large

amountsofenergyarerequiredformarijuanaproductionprocesses,equipment

inefficiencies,andtransportation(Figure3).

Duringmarijuanaproductionenergyisprimarilyconsumedtomaintainhigh

intensitylightinglevels(JohnsonandMiller2011).Onaverage,indoorgrowhouses

cancontainanywherefrom50,000to100,000wattsoflighting(JonlinandLewellen

2017).Duringthe“vegetation”phaseofindoorgrowingoperations,lightsarelefton

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formorethan18hoursperdayforthreeweekstoamonth(Mills2012).Following

thevegetationphase“flowering”occursandplantsareexposedto12hoursof

intenselightingdaily,forseveralweeks(Mills2012).Inlargeroperations,the

floweringphasegrowroomisusuallydividedintotwosections.Ononeside,lights

areonwhiletheothersideisleftcompletelydark.Thistechniqueisutilizedto

minimizetheneedforbiggercoolingsystemsandreducesutilitydemand(Mills

2012).

Traditionally,growershaveusedhighintensitydischargelamps,sodiumHPS

orotherlightingincluding,T5fluorescentlights,ceramicormetalhalide,and

inductionlighting(Mills2012).Althoughtheselightfixturesareinexpensiveand

produceenoughheattosupportplantgrowth,theyfrequentlyneedtobereplaced.

AtypicalmarijuanaoperationmayuseseveralhundredHPSlampsperyear,which

resultsinusingafullmegawattofpower(Mills2012).Thistypeofenergyuse

createsadditionalstrainsondistributionnetworksandcancausesubstantial

challengesforlocalcommunities(Carahetal.2015).

Productionofmarijuanaalsorequiresfilteringtheairevery30hoursin

ordertoproduceandremoveheat(Martynyetal.2013).Forexample,heatingand

dehumidificationisrequiredduringperiodsofnon-illuminationfordryingand

avoidingmolddevelopment.Atypicalindooroperationusesrefrigeration-based

dehumidifiers(Martynyetal.2013).Inordertolaterremoveexcessiveheatthe

growhousesarethenventilatedwithair-conditioning.TypicalHPSlampsgenerate

30to60wattsofheatpersquarefeetpergrowroom(Mills2012).Conventional

officebuildingsgeneratelessthan1wattpersquarefoot(Mills2012).Thisamount

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ofheatrequirescontinuouscoolingtoholdroomtemperaturesaround80degrees

Fahrenheit(JonlinandLewellen2017).

Other,lessintensiveusesofenergyincludeheatingofirrigationwaterand

generatingcarbondioxide(Carahetal.2015).Carbondioxidelevelsareraisedin

indoorgrowhousestoaccelerateplantgrowth.Oftenthelevelsareraisedupto4

timesabovenaturallevelsofcarbondioxide(Martynyetal.2013).Althoughthis

practicecontributesupto2percentofthetotalcarbonfootprintofcannabis

production,italsoshortensmarijuana’sgrowthcycleandcanreduceenergy

demand(Mills2012).Energyrequiredfortransportationalsoplaysabigrolein

marijuanaproduction.Nearly20percentoftotalemissionsproducedduring

marijuanacultivationaregeneratedbyvehicles,whichareusedinproduction

processesandforredistribution(Mills2012).

Overall,typicalproductionofindoormarijuanaplantsproduces3poundsof

carbondioxideforonesinglecannabiscigarette.Producingonekilogramof

marijuanaresultsinnearly5,000kilogramsofcarbondioxideemissions(Martyny

etal.2013).Theseresultsarereflectiveofaverageproductionprotocolsanddonot

takeintoaccountmethodsthatrequiremuchmoreenergyconsumption.Energy

intensivemethodsincludeusingoffsitedieselpowergeneration,whichproduces50

percentmorecarbondioxideemissionsorproductionsitesthatusehydroponicsto

growplants(Mills2012).Researchisneededtoidentifyallformsofenergy

consumptiononhighintensityproductionsitesinorderfordatatodepictamore

accurateestimationofenergyuse.

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Althoughoutdooroperationsrequiresubstantiallylessenergyforproduction

theyalsorequirelargeamountsofenergyandproduceemissions.Operational

differencesincluderequiringmoreenergythanindoorproductionforpumping

waterforirrigationandrequiredryingtechniquesintimeswhennaturalsunlightis

lacking(Carahetal2015).Outdoorproductionalsorequiresmorelandclearingsto

occur(Baueretal.2015).Notonlydoesthisprocesspreventfurthercarbon

sequestration,whichcanoftenbeanywherefrom125to1500tonsofcarbon

dioxidestoredperhectareoflandbutcarbonisoftenmobilizedafterclearings

(Wangetal.2017).Foreverykilogramofcannabisproduced,150kilogramsof

carbonareemittedwhichis3percentoftheamountproducedbyindoorplants

(Wangetal.2017).

AsmarijuanaproductioncontinuestoexpandinCaliforniapredictions

indicateagreaterdemandonenergyuse.Followingthelegalizationofmedical

marijuanauseanenergyexplosionoccurredinNorthernCalifornia(Slater2017).

Forexample,HumboldtCountyresidentialelectricityuseincreasedaround50

percentduringthistimeasmorecitizensbegantogrowmarijuana(Slater2017).In

ordertoreduceenergydemand,productionsitesneedtoinvestmoreincost

effectiveandenergyefficientpracticessuchascontrolsforlighting,airconditioning,

andfans.Growersalsoneedtoutilizedaylightinindooroperations.Estimates

indicatethattheapplicationofefficientpracticescouldreducethecostsofatypical

operationby$40,000peryear(Mills2012).Amorein-depthanalysisofcannabis

cultivationandgreatertransparencyisneededinordertoformulatesolutionson

howtoreduceenergydemandsinoperationsthatareatypical.

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Soil

Formostagriculturalfarmers,soilqualityplaysahugeroleinchoosing

wheretogrowtheircrops.However,formarijuana,over90percentofthesite

locationsareonlandwithpoorsoilquality(Butsicetal.2017).Sitelocationfor

illicitmarijuanagrowthisprimarilychosenbasedoffofaccesstowater,sunlight,

andareasthatareconcealedfromlawenforcementandcivilians(Babcock2017).In

ordertocompensateforpoorsoil,growersbringinnutrientefficientsoilforboth

indoorandoutdoorproduction.Although,manyareaswherecannabiscultivation

takesplacehavelocalbusinessesdesignedtosupplylargequantitiesofsoil,the

exactquantityandoccurrenceoftheimportsisundocumented(Winstonetal.

2014).

Cannabiscultivationalsoinvolveslandclearingandroadconstruction,both

ofwhichcauseenvironmentaldamageandcanbeextremelydemandingonsoil.In

areaswherethesoilqualityisalreadypoor,thesituationisworsenedbyremovalof

nativevegetation,whichcancauseerosionandstreamsedimentation(Keenanand

Kimmins1993).Whentreesarecutdowninlargequantities,thesurrounding

ecosystemlosesitsmainsourceofwaterretention,resultinginfloodsandleaching

ofnutrientsfromthesoil(KeenanandKimmins1993).Whenthereisanincreasein

waterrunoff,topsoilisoftenerodedintonearbystreamsandrivers(Winston

2014).Theresultingelevatedlevelsofsedimentationinthewaterincreasesnutrient

contentandexcessfinesedimenthasbeendocumentedtodeteriorateecosystem

conditionsforsalmonandtroutpopulations(Yageretal.2012).

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Clear-cuttingalsoresultsinchangesinmicrobialcomposition(Carahetal.

2017).Soilmicrobesdependontheinteractionbetweensoilandplantspecies.

Whentheplantsareremovedtheamountofmicrobiotaarereducedinresponseto

changesintemperatureandwatercontent(Winston2014).Soilmicrobesplayan

importantpartinvariousecologicalprocessessuchassuppressionofrootdiseases,

nitrogenfixation,andgrowthstimulantproduction(Winston2014).Byhindering

microbialformation,theoverallecosystemisatadisadvantage.

Theeffectsofclearcuttingformarijuanacultivationareoftenintensifieddue

tositelocation.Often,cannabisproductionsitesarefoundincloseproximityto

othercultivationsites.Forexample,whenasitehasupto200plantsthereisa36

percentprobabilityoffindinganeighboringsite.Whentherearenearly5,000plants

onasitetheprobabilityincreasesto67percent(Butsicetal.2017).Clusteringof

sitesleadstoincreasingnumberofroadsconstructedandclearcuttingoccurringin

centralizedareas,whichcancausemoreerosionandsedimentationlevelsto

increaseinstreams(Baueretal.2015).Althoughclusteringofsitesmayreducethe

spreadofmarijuanaproductiontootherpartsofcommunities,itmagnifiesthe

environmentalproblemsincertainareas.Clusteringcanintensifysoildegradation

toareasthatalreadyexperiencepoorsoilquality.

AirPollution

Airpollutionposesapotentialthreatforindoormarijuanaproducerssuchas,

inhalingtoxicchemicalslikecarbondioxide,carbonmonoxide,volatileorganic

compounds(VOCs),nitrousoxides(NOx),andairbornefungi(JohnsonandMiller

2011).Astudythatsampledthirtyindoorgrowingfacilitiesforlevelsofthese

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chemicalsfoundcarbondioxidelevelsrangingfrom500ppmto1500ppm,while

normalindoorcarbondioxidelevelsrangefrom300to1000ppm(Martynyetal.

2013).Carbonmonoxidelevelswerewellbelowthedesignatedrangeestablished

bytheEnvironmentalProtectionAgency(Martynyetal.2013).Morethanhalfofthe

examinedfacilitiesincreasedcarbondioxidelevelsbyun-ventingpropaneand

naturalgasburnerswhiletheremainderofthefacilitiesusedcarbondioxidetanks

(Martynyetal.2013).TheseunventedcombustionappliancesalsoproduceNO2but

therehasbeenlittleresearchofthischemicalcontaminantincannabisproduction

(Ashworth2017).

Airbornefungiposedthelargestpotentialhealthhazard.Marijuanaplants

experiencemoisturewhentheplantiscultivatingandduringthedryingprocess

(JonlinandLewellen2017).Moldisproducedwhenplantsbecomemoistby

irrigationandcannotdryduetopoorventilation(Cuypersetal.2017).Inorderto

concealodorsemittedfrommarijuanaoperationsandtokeepthefacilitieswarm

andhumid,ventilationisofteninhibited.Whiletheplantisdrying,waterthatwas

onceboundtocellsisaccessibletobecomefunguswhiletheplantbeginstodecay.

Plantswithmoisturecontentsgreaterthan12percentareabletogrowfungi

(Martynyetal.2013).Moldandmarijuanaproductionalsorequiretemperatures

around70to80degreesFahrenheitandhumiditylevelsrangingfrom50to70

percent(Martynyetal.2013).Ingrowrooms;airbornefungalsporeswereelevated

morethanfive-foldhigherthanoutdoorlevels(Martynyetal.2013).Duringthe

plantremovalprocessairbornefungalsporeslevelsincreasedupto34foldand

weresimilarinrangetomoldcontaminationobservedindemolitionbuildings

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(Martynyetal.2013).Theseindoorairpollutantsposeathreattorespiratory

health.

Pesticides

InCalifornia,littletonoresearchhasbeenconductedontheuseofpesticides

onmarijuanaplants.Currently,therearenoregisteredpesticidesforcannabisuse

intheUnitedStatesandtheEnvironmentalProtectionAgencywillnotregisterone

aslongasitisclassifiedasaSchedule1drug(Stone2014).InBelgiumhowever,

researchhasbeenconductedontherisksassociatedwithpesticideresidueon

indoormarijuanaplants,infrastructurerequiredforcultivation,andplantremoval

(Cuypersetal.2017).IndoormarijuanacultivatorsinbothBelgiumandtheUnited

Stateshavesimilargrowingtechniques,butthepesticidesusedvaryduetodiffering

pesticidelawsandregulationinthedifferentcountries.InBelgium,72indoorplant

sitesweresampledforpesticides.Cuypersandcolleagues(2017)foundpesticide

usein64percentoftheplantssampledincludingnearly20differentpesticides,

suchasbifenazate,imidacloprid,andcypermethrin.Although,mostofthechemicals

foundhadalowvolatility,theyweredetectedin65percentofthecarbonfilter

clothsusedinthesensorsincultivationrooms(Cuypersetal.2017).Inorderto

defusemarijuana’sintensesmell,growersuseturbinestocirculateairthrough

carbonfilters(JohnsonandMiller2011).Thehighpercentageofpesticidesfoundin

thecarbonfilterssuggeststhatpesticidesprevailintheatmosphereofthe

cultivationroomsduringandpossiblyaftercultivation(Cuypersetal.2017).

Researchisneededtodeterminewhetherthevolatilityofthepesticidesincreases

whendismantlingandremovingtheplants.Researchisalsoneededtodetermine

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therisksthechemicalsposeonmarijuanagrowersandstaffastheycanbeexposed

throughbothdermalandinhalationofthevapors.

Watersamplesfromthe72sitesinBelgiumwerealsotestedforpesticide

compounds.Outof41watersamples,24werecollectedfromtanksattachedtoan

irrigationsystem,4werefromstagnantwater,and13sampleswerefrombottles

thatwerenotlabeled.20percentofthesamplestestedcontainedpesticides

however;nopesticideswerefoundinthetankwaterconnectedtoaplantirrigation

system(Cuypersetal.2017).Therefore,thedatasuggeststhatpesticidesweremost

likelyappliedbysprayingchemicalsontheplantsdirectlyandnotbymixingthem

withirrigationwater.

InCalifornia,pesticidesareusedtopreventthedamageofcannabisplants

fromSpidermites,aphids,andfungi(Thompsonetal.2014).Attemptshavebeen

madetodetectthetypesofpesticidesusedintheUnitedStatesbyscreening50

samplesofconfiscatedillegalmarijuanaplants(Schneideretal.2014).Pesticides

werefoundin12percentofthe50indoorcannabisplants(Schneideretal.2014).

Researcherswereunabletocollectonsitesamplesandhadtorelyonplantstaken

byauthorities.Identificationofpesticidesalongwithdataonlocationweremade

unavailabletherefore,athoroughassessmentofpesticideuseisstillneededinthe

U.S.

Mostofthedataonpesticideuseformarijuanaproductionisprimarily

collectedfromauthoritieswhenraidsareconducted(Stone2014).Forexample,in

2008,Californiaauthoritiesremovedapproximately3.6millionillegallygrown

outdoormarijuanaplants(Stone2014).Theseplantswereremovedfromfederal

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andstatepubliclandsandwerefoundwiththousandsofpoundsofpesticides.

Similarly,in2011authoritiesintheMendocinoNationalForestremovedover

630,000marijuanaplantsalongwithnearly23,500kgoftrashandapproximately

70kgofpesticides(Gabrieletal.2015).Authoritiesalsofoundsignificantamounts

ofanticoagulantrodenticidenearplantsalongirrigationlines(Figure2).Thismay

beduetothecombineduseofpesticidesandfertilizer,whichincreasesthe

possibilityofchemicaluptakeinnearbyvegetation.

Althoughauthoritieshavefoundpesticidespresentonmarijuanasites,

researchisneededfromthescientificcommunityonthefrequencyofuseand

locationofchemicalprevalence.Atoxicologicalriskassessmentisalsoneededto

determineunderwhatconditionsthepesticidescanbeused,atwhatquantity,and

wheretheycanbesprayed.Constraintstoconductingthistypeofresearchincludes

alackofsystematicmonitoringofpesticideuseonmarijuanasitesandmuchofthe

datathathasbeencollectedisanecdotalandseverelylacksinpeerreview.

ThreattoWildlife

Theuseofanticoagulantrodenticide(AR)inmarijuanacultivationsiteshas

emergedasasignificantconcernforsurroundingwildlifepopulations(Thomsponet

al.2014).ARsaredesignedtosuppresspestpopulationsbycreatingclottingand

coagulationinjurieswhenconsumed(Gabrieletal.2012).SecondgenerationARs

aremoreacutelytoxicandcanpersistintheenvironmentandtissueforlonger

comparedtofirstgenerationARs.PekaniapennantiorCaliforniaPacificFishers,

havebeenexposedandthreatenedbysecond-generationanticoagulantrodenticide

(SGARs)asaresultofcannabiscultivatorstryingtocontrolpopulationsofNeotoma

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spp.,morecommonlyreferredtoaswoodrats(Carahetal.2015).Fishersare

currentlyunderreviewascandidatestobelistedunderthefederalEndangered

SpeciesAct(Gabrieletal.2013).AttheUniversityofCaliforniaDavis,58

toxicologicalscreeningswereperformedonfishersfoundoncommunityandpublic

landsusedformarijuanaproductioninNorthernCalifornia(Gabrieletal.2012).

Theresultsshowedapproximately46ofthe58fishersor80percentofthe

populationwereexposedtoanticoagulantpesticides,withnearly100percentofthe

exposuresbeingSGARs(Gabrieletal.2012).InAprilof2009,researchersfromthe

UCBerkleySierraNevadaAdaptiveManagementProjectfoundadeadmalefisher.

AfterperforminganecropsyitwasconfirmedthatthefisherdiedofARpoisoning.

ThreeSGARcompounds,brodifacoum,bromodiolone,andchlorophacinonewere

foundintheanimal’sliveralongwithover250mlofbloodinitsabdominalcavities

(Thompsonetal.2014).

ResearchersmonitoredthepoisonedCaliforniafishersovertheirlifetimes

andfoundthattheindividualstestedoverlappedwithcannabiscultivationsitesthat

usedtheserodenticides.Usingspatialanalysis,clusteringofrodenticideexposure

wasalsodetected,whichsuggestswidespreadcontaminationofARsinfisher’s

range(Thompsonetal.2014).InCalifornia,fisherhistoricalhabitatprimarily

consistsofareasencompassedbypublicforestandparklands.Fishersarerarely

exposedtodevelopmentsinsuburbanneighborhoodsoragriculturalcrops,which

arethemostcommonplacestofindtheuseofARs(Thompsonetal.2014).Itis

commonforwildlifetocomeintocontactwithARsthroughlegalagricultural

sprayingorwhenthecompoundisusedwithin50feetofasuburbandevelopment

20

(Gabrieletal.2013).SinceJune2011,theEnvironmentalProtectionAgencyhas

regulatedtheuseofSGARstoagriculturalstoresmakingthemunavailableto

consumersatretail(Gabrieletal.2013).ThusrenderingtheuseofARsillegalon

Californiapubliclands,yetfishersarebeingexposedtotherodenticides.

ThedocumentedcasesoffishermortalitiesthathadbeenexposedtoSGARs

typicallyoccurredduringthemonthsofApriltoJunewhenitistimeforcannabis

cultivatorstoplantseedlings.Duringtheseedlingprocess,cultivatorsuseheavy

amountsoftoxicpesticidesinordertopreventrodentsfromdamagingthenew

plants(Thompsonetal.2014).Thistimeoftheseasonisalsocrucialforfemale

fisherstoraisetheirkits(Gabrieletal.2013).ResearcheshavediscoveredSGARsin

thetissueofdeadkits,whichhasraisedconcernsovertheeffectsof

bioaccumulationoftherodenticidesthatmaybetransferredfrommothertokit

throughmilkorearlystagesoffetaldevelopmentthroughtheplacenta(Thompson

etal.2014).CasesofbioaccumulationofARhavealsobeendocumentedinseveral

invertebrates,includingAporrectodeacalignosa(earthworms)andCantareus

asperses(snails),bothofwhichareincludedinthewiderangeofresourcesfishers

consume(Gabrieletal.2013).

Duetoalackoffunding,researchersareunabletodeterminewhetherornot

athresholdfortheamountofexposuretoSGARsafishercanexperience.

ResearchersfoundcasesoffishermortalityatlowlevelsofSGARexposureand

instancesofhighlevelsofexposurewhilenoobvioushealthaffectsoccurred.

Withoutproperdocumentationofenvironmentaldamageandlackoffunding,

21

wildlife,includingtheCaliforniafisher,willcontinuetobethreatenedbythetoxic

pesticidesusedintheproductionofmarijuana.

FishSpecies

IntheEelRiverofnorthwesternCalifornia,severalfishspeciesare

threatenedbytheenvironmentalimpactsofmarijuanaproduction.Historically,the

EelRiveristhethirdlargestflowingriverinCalifornia.ItoriginatesinMendocino

CountyandflowstoanestuaryinthePacificOcean.Naturally,theEelRiverreceives

largeamountsofsedimentfromlandslidesanderosion(Poweretal.2015).The

impactsoferosionandlandslideswouldordinarilybebufferedbynaturally

occurringriparianvegetationtrappingthefinesediments.However,duetoland

clearingandroadconstructionassociatedwithcannabiscultivationmuchofthe

nativevegetationhasbeenremovedfromthebanksoftheEelRiver(Poweretal.

2015).Thefailureofseveralwaterridgetopimpoundmentshasalsoledto

landslidesandincreasedtheamountoffinesedimentintheriverresultingintheEel

becomingmorewideandshallow(Poweretal.2015).Thus,increasingthe

vulnerabilityoftherivertobecomewarmerandeasiertodewater.Currently,

concernshaverisenoverthereleasingbloomsofcyanobacteria.Lesswaterflowand

warmertemperaturesresultinalgalproductionthatisnotbeingconsumedby

organisms.TheseconditionsincreasepHandlowerdissolvedinorganiccarbon

concentrationsthuscreatingfavorableconditionsforcyanobacterialgrowth.These

toxicbloomshavecausedthedeathof11dogsintheEelRiversince2002(Poweret

al.2015).

22

Thechangeinrivertemperatures,sedimentload,andflowvelocityhave

threatenedthepopulationsofChinook,Coho,andSteelheadfishthatarecommonly

presentintheEelRiver(Table1).Ideally,salmonandtroutusethespacebetween

cobblesandboulderstoescapepredation(Kondolf,2000).Theareawherewater

flowsdowntothegravelprovidesanimportantfoodsupplyforjuvenilesalmonand

trout.Excessorfinesedimentcanchallengethesalmonortrout’ssourceofcover

andfoodbycongestingthespacesbetweenthegravel(Chapman1988).Water

temperaturealsoplaysanimportantroleinsalmonandtroutpopulations.Each

speciesrequirescool,freshwaterandincreasedtemperaturescandecreaseegg

survivalrates,increasethesusceptibilityofdisease,lowerthefecundityinthe

species,andmore(McGeeretal.,1991).Baueretal.(2016)foundthatwater

demandfortheproductionofmarijuanacropsexceededthestreamflowinthreeof

fourwatershedsintheEelRiverregion.Thistypeofwateroverusecouldleadto

increasedrivertemperaturesandseverelyaffecttheflow,whichcouldbethe

tippingpointinanecosystemthatsupportslargepopulationsofsalmonandtrout

(Table1).

SiteLocation

Sitelocationplaysahugeroleintheenvironmentalimpactsassociatedwith

marijuanaproduction.Fewstudieshavebeenconductedonhowcannabis

cultivatorschoosethesizeandlocationoftheiroperations.Incomparisontoother

formsofagricultureinCalifornia,mostcropsarewellmappedanddocumented

(Kochetal.2016).Fewstudieshaveattemptedtodocumentandpredictwhere

cultivationsitesarelikelytotakeplace(Kochetal.2016,ButsicandBrenner2016,

23

andButsicetal.2017).Over4,400cannabis-cultivatingsitesin60different

watershedshavebeenanalyzedtocreatemodelsthatcanbeusedtopredictwhere

growerswilllocatetheirsites(ButsicandBrenner2016).Predictorvariables

includedrugmarkets,environmentalconditions,andpolicies.

Sitepreparationtypicallyrequireslargeamountsofequipmentincluding

PVCforirrigationandtoolsforremovingnativevegetation.Ideallocationswouldbe

closetoaroad,whichiswhynearly70percentofcultivationsiteswerefoundless

than500metersfromdevelopedroads(Kochetal.2016).15percentofsiteswere

within100metersofroads(ButsicandBrenner2016).Theneedforaccesstoroads

suggestsariskoflandscapefragmentationthatcouldoccurinorderforsitestobe

developed(Figure4).

Veryflatandsteepslopesarenotfavored;thismaybeduetoirrigatedwater

beingmoreeasilytransportedonslightlyslopedland.Lessthan20percentofsites

wereonsteepslopes(Kochetal2016).Thedegreeofslopeincreasestheriskof

sedimentation,landslides,anderosion(ButsicandBrenner2016).Sitesthatface

southarefavored.Thismaybeduetogreatersunlightavailabilitythatwillleadto

greatergrowthfortheplants.Lowerelevationalsoplaysaroleduetohigher

temperaturesandpotentialforgreaterplantproductivity(Butsicetal.2017).

Accesstofreshwatersourcessuchasriversandstreamsarefavorable.

Studiessuggestspatialclusteringwithinwatershedsiscommon(Butsicetal.2017).

Onaverageanywherefrom70to481growsoccurredinonewatershedinNorthern

California(ButsicandBrenner2016).Thereisasignificantpositivecorrelationto

watershedareaanddensityofplants.Alargenumberofplantswouldrequiremore

24

irrigationwaterandthusimpacttheoverallhealthofthewatershed.Forexample,

fivepercentofcultivationsitesarelessthan100metersfromthreatenedfish

habitat(Kochetal.2016).Intheseparticularsitesthenumberofplantswere

estimatedaround300,000,whichwouldrequireapproximately700,000cubic

metersofwater(Baueretal.2015).Thisamountofwatercouldseverelyimpact

streamsandthreatenfishpopulations.

Growersarealsomorelikelytoestablishsitesonnationalforestlandswhen

marijuanapricesarehigher.Forexample,in2010,governmentagenciesremoved

over10millionmarijuanaplantsofwhich94percentweregrownoutdoorsand

nearlyhalfwerediscoveredonfederallandsinCalifornianationalforests(Babcock

2017).TheUnitedStatesDepartmentofJusticeNationalDrugIntelligenceCenter

alsoreportedanationwideincreaseofoutdoormarijuanagrowsofnearly150

percentbetweentheyearsof2005to2010(Kochetal.2016).

Marijuanasitesarealsooftenfoundincloseproximitytooneanother.

Clusteredsitesnotonlyintensifyenvironmentalimpactsincentralizedregionsbut

theyarealsolinkedtoincreasinglevelsoffragmentation(Butsicetal.2017).Wang

etal.(2017)examined62growsitesinHumboldtCountyandcomparedtheimpacts

offragmentationtothatoftimberharvestthatoccurredfrom2000to2013.Results

showedthat1km2ofcannabishadthesameifnotmoreimpactonforest

fragmentationthan1km2oftimberharvest(Wangetal.2017).Cannabiscultivation

siteshadnearlydoublethelossofcoreareaandthreetimestheamountof

fragmentedpatcheswithgreateramountsofexposededge(Wangetal.2017).

25

Thesetypesofforestpatchesexhibitirregularshapeandarelessintactresultingin

increasedriskofimpactingbiodiversityandecosystemfunctions(Wangetal.2017).

Decriminalizationandlegalizationofmarijuanaproductionplayan

importantroleontheeffectofillicitoutdoorcultivationoccurringonpubliclands

(Vanhoveetal.2011).Researchsuggeststhatinstateswithlegalcannabismarkets,

demandforillicitcultivationcontinuestopersist(Vanhoveetal.2011).Thismaybe

duetoillicitgrowersattemptingtoavoidregulationsandtaxesenforcedonlicensed

growers.Or,inplacessuchasColoradoandOregonwhereproductionand

distributionwerelegalized,illicitgrowsonfederallandsincreasedtosupplystates

wheremarijuanaisprohibited(Vanhoveetal.2011).Aslegalizationoccurs,shiftsin

pricesmayalsoaffectthelikelihoodofcultivationinnationalforests.Forexample,

sharingthemarketwithlegalcultivatorscoulddecreasepricesforillegalcannabis,

whichwouldresultinmoregrowsoccurringonpubliclands(Babcock2017).

Althoughtheoutcomesofthelegalizationofrecreationalmarijuanaare

unknown,researchershavefoundthatsitestendtobeclustered,centralizednear

watersheds;occuronmildlysteeplocations,onpubliclands,andfarfromdeveloped

roads.Thesetypesofsitelocationshaveledtodisproportionatenegativeecological

affectsandfurtherresearchisneededtodevelopbetterland-useplanning

techniquesthatcouldbeimplementedintopolicy.

Conclusion

Theenvironmentaleffectsassociatedwithmarijuanaproductionaresevere.

Theimpactsarepredictedtoworsenasthemarketforrecreationalmarijuana

expands.Asdemandformarijuanaincreases,Californiastreamsandriversare

26

threatenedtobecomedewateredwhichwillaffecttroutandsalmonpopulations,

energydemandwillworsen,alongwiththeuseoftoxicchemicalsthatthreatenthe

healthofemployeesandwildlife.Currently,stateofficialshaveestablishedareport

addressingthenegativeenvironmentalproblemsassociatedwithcannabis

cultivation.Thisreportislargelybasedoffofpopularmediasourcesandlacksin

scientificliterature.Californiansneedtoaddressissueswithinthestate’sreportin

ordertoensureenvironmentalprotection,restoration,andmitigation.Strong

provisionsandfundingforresearchandprotectionareneeded.Alongwith

regulationsthatwillrequiremarijuanagrowerstoimplementsustainablepractices

suchas,monitoringandcontrollingwateruse,usingrenewableenergy,establishing

protocolsforpesticideuse,andonlygrowinginpermittedareas.Strong

enforcementoftheseprovisionswillbenecessaryaswellasapartnershipbetween

growers,scientists,andlawmakers.Theenvironmentalimpactsassociatedwith

cannabiscultivationhavegonewidelyoverlookedandapushforsustainable

practicesneedstobetakennow.

27

Figure1.GrowingseasondischargeforthemonthsofJunetoOctoberintheEelRiverwatershedcomparedtomarijuanawaterdemand(Carahetal.2015).

28

Figure2.RodenticidesconfiscatedbylawenforcementfromillicitcannabisoperationsinnorthwesternCalifornia,whichfallwithinfisher(Martespennanti)range(Gabrieletal.2012).

29

Table1.AquaticspecieswithintheEelRiver(Baueretal.2016).

30

Figure3.Energyuseandcarbonfootprintofaverageindoorcannabisproduction(Mills2012).

31

Figure4.LandclearingandroadconstructionassociatedwithcannabiscultivationsitesneartheTrinityRiverwatershed.Figure(a)demonstratesthesitesbeforeconversionin2004andfigure(b)isafterconversionin2012(Carahetal.2015)

32

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