Conserving Bumble Bees Name _________________________

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Part 1: Value of Pollinators

Insectsareresponsibleforthepollinationofapproximately80%ofallfloweringplantsincludingbothwildplantsandagriculturalcrops.Withadequatepollination,plantsproducefruits,nuts,andberrieswhichareconsumedbyhumansandotheranimals.Properpollinationalsoproducesseedallowingforplantreproductioninthewildandcontinuedagriculturalcroppropagation.

AccordingtoaCornellUniversitystudy,honeybeesandotherinsectpollinatorsintheU.S.contributeanestimated$29billiondollarsannuallyinfarmincome(Calderone,2012).U.S.agriculturegainsapproximately$15billionofthistotalvaluefromhoneybeepollinationalone,butoftenoverlookedarethespecializedpollinationservicesprovidedbybumblebees.

Bumblebeesexhibitauniquebehaviorknownas“buzzpollination,”inwhichthebeehangsupsidedownonaflowerandvibratesherwingmusclescausingthereleaseoflargeamountsofpollen.Buzzpollinationisespeciallyvaluedbygrowersoftomatoes,peppers,andcranberriesbecauseitleadstobetterfruitsetthanpollinationbyhoneybees.Inaddition,bumblebeesaresomeoftheonlyspecieswhichfunctioneffectivelyingreenhousesettingswherecropssuchastomatoes,sweetpeppers,andstrawberriesaregrown.

The Problem: Pollinators in Peril

Overthepastdecade,reportsofdeclininghoneybeehealthhavedominatednewsheadlinesandcapturedtheattentionofthepublic.Concernforpollinatorwell-beingshouldalsobeexpandedtoincludethenearly4,500otherbeespeciesinNorthAmerica.Manyofthesevaluablepollinators,includingnativebumblebees,mayalsobeexperiencingpopulationdeclines.

Sohowdoresearchersgoaboutdeterminingifwildbeepopulationsareincreasing,decreasing,orremainingstable?Thefirststepisidentifyingifhistoricalmonitoringdataexistsandaccessingit.Thismayrequireresearcherstoexaminewell-curatedinsectcollectionstodetermineabundanceanddistributionofaspeciesinpreviousyears(Figure2).Ifthisinformationisunavailableorinaccessible,researcherswillfacethechallengeofbeingunableto

Figure1:BumblebeeonredcloverPhotocredit:ErinIngram

Figure2:ResearchersexamininganinsectcollectionforhistoricalinformationPhotocredit:USDAARS

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comparecurrentbeecountswithhistorical,baselinedata.Ratherthanprovidingevidenceofapopulationtrendingupordown,researchersmayonlybeabletopresenta“snapshot”ofthecurrentpopulation.

Inthemid-2000’s,researchersinpointedouttheseverelackofdataonpollinatorabundanceanddistribution.Inaddition,existingbeesurveysoftenreliedonsamplingmethodswhichwerenotstandardizedorrepeatable.Toaddressthisissue,variousresearchgroupsworkedtogethertoconductalarge-scale,systematicbumblebeesurveyintheU.S.(Cameronetal.,2011).Theaimwastogatherdataonabundance,speciesdiversity,anddistributionofeighttargetbumblebeespecies.Alleightspecieswerehistoricallycommon,butanecdotalreportsindicatedthatsomespeciesmightbeindecline.Oftheeightspecies,fourweresuspectedtobeindeclinewhiletheremainingfourwereassumedtoberelativelystable(Figure3).

Usingrecentdataandhistoricalrecords,researcherscoulddeterminepopulationtrendsbyexaminingaspecies’relativeabundancecomparedtootherbumblebeetargetspeciesovertime.Relativeabundancecanbecalculatedbydividingthenumberofindividualsofthetargetspeciesbythetotalnumberofothertargetspeciescollectedinthesameregion.

Relativeabundance= ##$%&'()%*+),-)*-./-0-/1&2*%#%&2##$&22%&'()%*+),-)*#$-.%)')*%-.%3)')(-#.

Forexample,inthissurvey,onlytwoofthetargetbeespecies(B.bifariusandB.occidentalis)arefoundintheglobalwestregion(includingthestatesofAZ,CA,CO,ID,MT,NM,NV,OR,SD,UT,WA,andWY).TodetermineiftheB.occidentalispopulationwasindecline,researcherscalculatedtherelativeabundanceforthehistoricalperiod(1900-1999,blackbars)andcomparedthistotherelativeabundanceoftherecentcollectionperiod(2007-2009,greybars).

1. WhattrendintheB.occidentalispopulationdoyouobserveinthisgraph?

Therelativeabundancedecreased(ordeclinedovertime.

2. ApproximatelyhowmuchdidtherelativeabundanceofB.occidentalischangeovertime?Therelativeabundancedecreasedfromabout30%to<5%.

BumblebeespeciesexaminedPopulationssuspectedto

beindeclinePopulationssuspectedtobe

relativelystable• Bombusaffinis • Bombusbifarius• Bombusoccidentalis • Bombusvosnesenskii• Bombuspensylvanicus • Bombusbimaculatus• Bombusterricola • Bombusimpatiens

Figure3:Targetspeciesexaminedin2007-2009U.S.bumblebeesurveyfromCameronetal.,2011

Figure4fromCameronetal.,2011:Blackbarsare1900-1999,graybarsare2007-2009.

RelativeAbundance

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Figure5fromCameronetal.,2011.Blackbarsindicate1900-1999.Greybarsindicate2007-2009.Keytospeciesnames:B.aff=Bombusaffinis;B.bif=Bombusbifarius;B.bim=Bombusbimaculatus;B.imp=Bombusimpatiens;B.occ=Bombusoccidentalis;B.pen=Bombuspensylvanicus;B.ter=Bombusterricola;B.vos=Bombusvosnesenskii.

Examinefigure5aboveindicatingrelativeabundanceofeightbumblebeespeciesinfourU.S.regions.

3. ComparethepopulationtrendsofB.pensylvanicusintheGlobalEastandNorthern/CoastalEast.Inbothcases,B.pensylvanicusdeclined.However,intheGlobalEasttherelativeabundancedecreasedfrom~45%to~10%andintheNorthern/CoastalEastitdecreasedfrom~20%to~2%.

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4. Ineachoftheregions,whichbumblebeespecies’populationsshowevidenceofdecline?GlobalWest:BombusoccidentalisPacificWest:BombusoccidentalisGlobalEast:B.pensylvanicusNorthern/CoastalEast:B.affinis,B.pensylvanicus,B.terricola

5. WhichbeespeciesareNOTexperiencingdeclineinthePacificWest?Howdoyouknow?BombusbifariusandB.vosnesenskiidonotappeartobedecliningbecausetheirrelativeabundancewentupinthelatestpopulationsurveyin2007-2009.

Part 2: Likely Culprits of Bumble Bee Decline?

Beforewecanbegintohypothesizereasonsforthedecreaseinsomebumblebeepopulations,wefirstneedtoconsiderwhatbumblebeesneedinordertosurvive.

Bumblebeesneed…

• High-qualityhabitatfornesting• Plentifulfoodandwaterresourcesnearbythroughoutthespring,summer,andfall• Anenvironmentrelativelyfreeofpests,parasites,pathogens,andpesticides

1. Whatarethreefactorsyouthinkmighthaveanegativeimpactonbumblebeepopulations?

Studentanswerswillvary.Acceptallreasonableanswers.

2. Which,ifany,ofthesefactorsarerelatedtohumanactions?Discussthesefactorswithapartner.Studentanswerswillvary.Acceptallreasonableanswers.

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TheselectedexcerptbelowisfromaNatureConservancyblogpostentitled“PlightoftheBumbleBee:ConservingImperiledNativePollinators”fromMattMiller.Thepostprovidesuswithaglimpseofthepotentialfactorsplayingaroleinbumblebeedeclines.

3. WhatarethreefactorsthatMattsuggestsarethreateningbumblebeesandotherpollinators?Threeofthefollowing:Pesticideexposure,habitatloss,climatechange,competitionfromnon-nativebees,introduceddiseases.

Where Have All the Pollinators Gone? An incident in an Oregon parking lot last summer dramatically illustrated the plight faced by native pollinators. At a mall parking lot in Wilsonville, people began finding dead bumble bees – unbelievable numbers of dead bumble bees. It turned out to be the largest bumble bee die-off ever recorded, with more than 50,000 dead bees littering the area. A wildlife mystery? Not quite. It turns out that someone had sprayed 55 flowering trees with a pesticide known as a neonicotinoid, legal for use but deadly for insects, including beneficial ones like pollinators. … In addition to pesticides, bumble bees face a long list of other threats – habitat loss, climate change, competition from non-native bees, introduced diseases. According to the Xerces Society, habitat loss in particular is having a profound effect on bumble bees (and other native pollinators). Bumble bees need a mix of native plants to feed on as well as grassy areas to burrow. They once found this habitat in plenty on the edges of farms and yards, and even in roadside ditches. But there has been a tendency to “clean up” – to remove the wilder edges around human development. That’s bad for bees and other pollinators. A neatly trimmed grass lawn may be green but it’s not green – especially if it is sprayed with pesticides and all native plants are removed. We often think of habitat loss as an irreversible problem, or one that can be solved only by intensive restoration activities. If a subdivision goes in and takes out part of a wolverine’s range, it is not like you can plant a few trees and bring back wolverines. But with bumble bees, you can reverse habitat loss. Yards, ditches and abandoned lots can make a big difference. Your personal actions can save native pollinators – protecting not only cool critters but also vital ecosystem services.

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MattMillerstatesinhisblogpost“Yards,ditchesandabandonedlotscanmakeabigdifference.Yourpersonalactionscansavenativepollinators–protectingnotonlycoolcrittersbutalsovitalecosystemservices.”

4. WhatactionsmightMattbereferringtointhispost?Whatarethreepersonalactionsyoucouldtaketohelpconservebumblebeespecies? Studentanswersmayvary.Reasonableanswersmayincludeplantingofgrassesfornestinghabitat,plantingofflowersforfood/foragingresources,notsprayingpesticides,reducedmowingofgrassesorflowersinditchesorlots,plantingofnativeflowers

Part 3: Taking a Closer Look at Habitat Loss

AccordingtoareviewarticlebyGoulson,Lye,andDarvill(2008)ondeclineandconservationofbumblebees,”declinesinbumblebeespeciesinthepast60yearsarewelldocumentedinEurope,wheretheyaredrivenprimarilybyhabitatlossanddeclinesinfloralabundanceanddiversityresultingfromagriculturalintensification.”

Bycomparinghistoricalandcurrentlandusepatterns,wecanseemoreandmoreofourlandscapehasbeentransformedforagriculturaluseandurbandevelopment.Thischangeinlandusehasledtoalossofadequateforagingandnestinghabitatforbumblebeesandotherpollinators.IntheU.S.,forexample,85%ofIowa’slandareawasonceprairiegrassland,providingabundanthabitatforbumblebees.However,Iowa’sprairieshavebeenreducedto0.1%ofalllandareawithmostlandnowlargelycoveredinmonoculturecropsandurbanareas(Goulsonetal.,2008).

Figure6fromGallant,Sadinski,Roth,&Rewa,2011:Iowa’slandcoverinmid-1800's(A)and2001(B)

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Inanattempttoreversethislossofhabitatandprotectbiodiversity,theU.S.andEuropehaveenactedagriculturalpoliciesthatrewardgrowersforenactingvariouslandmanagementtechniqueswhichminimizeenvironmentalimpact.Eachmanagementtechniquehasadifferentobjectiveandtherefore,resultsindifferinglevelsofsuccessfulconservationofthreatenedbumblebeespecies.

Forexample,somelandmanagementtechniquesaimtoincreasenestinghabitatbyplantinggrassesinfieldmargins.Anothertechniquemayencouragegrowerstolimittheiruseofpesticides.Otherapproachesmayencouragetheplantingofpollen-andnectar-producingflowerstoimprovebumblebees’accesstoqualityforagingresourcesacrossallseasons.

Figure7:Cropfieldmarginsprovidepotentialhabitatorforagingresourcesforbees.Photocredits:Left,RichardWebb-CreativeCommons;Right,KeithEdkins-CreativeCommons

Withsomanydifferentlandmanagementtechniquestochoosefrom,researchersintheUnitedKingdom(UK)decidedtoexaminetheeffecteachapproachhadonabundanceanddiversityofbumblebeespecies.

1. Ifyouwerearesearchercomparingtheeffectofseverallandmanagementtechniques,howmightyousetupanexperimenttocomparetheirconservationsuccess?

a. Whatwouldyourindependentanddependentvariablesbe?b. Whatwouldbeyourcontroltreatment?c. Howwouldyoureplicateyourexperiment?d. Whatconfoundingfactorsshouldyouconsider?

Studentanswerswillvary.Acceptallreasonableanswers.

Independentvariables:typeoflandmanagementtechnique

Dependentvariable:Mightbebumblebeeabundance,numberofdifferentspeciesofbumblebees

Acontroltreatmentmayincludeaconventional(notconservation)landmanagement,suchasplantingofthecropinthefieldmargin.

Aconfoundingfactorcouldbeflowersorgrassesavailableinadjacentfields(bumblebeescanforageuptoamilefromtheirnest).

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Examining the Effectiveness of Conservation Strategies

AresearchstudyconductedbyCarvell,Meek,Pywell,Goulson,&Nowakowski(2007)comparedbeeabundanceinfieldmarginsintheUKwithsevendifferentlandmanagementtechniques.Researcherscomparedthefollowingtreatments:

1. Crop(Crop):fieldmarginplantedwithacerealcrop;conventionalorstandardpractice2. Conservationheadland(Conshead):fieldmarginincludescerealcropwithrestricted

applicationofherbicideandinsecticide;encouragesbroad-leafplants3. Naturalregeneration(Natregen):fieldmarginincludesnocrop;noherbicide,pesticide,or

fertilizer;encouragesrareannualplants4. Tussockygrassmixture(Grass):fieldmarginincludesfivegrassspecies;noherbicide,

pesticide,orfertilizer;providesnestinghabitat5. Wildflowermixture(Wildflower):fieldmarginsownwith21nativewildflowerspeciesand

fourfinegrassspecies;noherbicide,pesticideorfertilizer;providesforagingandnestinghabitat

6. Pollenandnectarmixture(Pollen&nectar):fieldmarginsownwithfouragriculturallegume(bean)speciesandfourfinegrassspecies:noherbicide,pesticideorfertilizer;providesforagingandnestinghabitat

Figure8fromCarvelletal.,2007:Therelationshipbetweenflowerabundanceofbeeforagespeciesandtotalbeeabundanceondifferentfieldmarginlandmanagementtechniques.Valuesrepresentthelog-transformedmeannumberofbeesperplotateachsite,averagedover3years.

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Examinefigure8onthepreviouspage.Answerthefollowingquestions.

1. Whatpatternsinnumberofbeeforageflowersdoyouobserveinthedata?Studentanswerswillvary.Acceptallreasonableanswers.Cropland(thecontrol)andtussockygrassmixturehadconsistentlylownumbersofbeeforageflowers.Naturalregenerationandconservationheadlandhadmoderatebutvariablenumbersofflowers.Wildflowermixtureandpollenandnectarmixturesshowedaconsistentlyhighnumberofbeeforageflowers.

2. Whatpatternsinbeeabundancedoyouobserveinthedata?Croplandandconservationheadlandappearedtohavethelowestnumberofbees,followedbyamoderatenumberofbumblebees(andmorevariation)inthetussockygrassmixtureandnaturalregeneration.Lastly,thewildflowermixtureandpollenandgrassmixtureshadconsistentlyhighnumbersofbumblebees.

3. Describetherelationshipbetweenthenumberofbeeforageflowersandthenumberofbumblebees.Therewasapositiverelationshipbetweenthenumberofbeeforageflowersandnumberofbumblebees.(Thisisnotsurprisingconsideringtherelationshipbetweenbeesandflowers.)

4. Whichlandmanagementstrategywouldyourecommendtoagrowerinterestedinconservationofbumblebees?Why?Studentsshouldadvisegrowerstoplantthepollen&nectarmixturetoattractthegreatestnumberofbumblebeesandminimizeoreliminatepesticidesandherbicidespraysinthefieldmarginstoavoidoff-targetexposurewithbumblebees.

Reflection

5. Howmightthisinformationbeusedtoinformconservationstrategiesinagroecosystems?Studentanswersmayvary.Attheleast,studentsshouldcommentonthefollowing:Thisdataprovidesevidencethatgreaternumbersofbeeforageflowersattractsandsupportsagreaternumberofbumblebees.Whenagriculturalpolicyiswritten,itshouldprovidethegreatestsupportforlandmanagementstrategiesthatpromotemorebeeforageflowers(suchasthewildflowermixtureorpollenandnectarmixture).Thisworkcouldsupportfuturestudieswhichexaminethetypeofflowersthatsupportthegreatestnumberofbumblebeespecies,amountofareaneededtoseeaconservationbenefit,whichplantingssupportrarebumblebeespecies,etc.

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References

Calderone,N.W.(2012).InsectPollinatedCrops,InsectPollinatorsandUSAgriculture:TrendAnalysisofAggregateDataforthePeriod1992–2009.PLoSONE,7(5),e37235.http://doi.org/10.1371/journal.pone.0037235

Cameron,S.A.,Lozier,J.D.,Strange,J.P.,Koch,J.B.,Cordes,N.,Solter,L.F.,&Griswold,T.L.(2011).PatternsofwidespreaddeclineinNorthAmericanbumblebees.ProceedingsoftheNationalAcademyofSciences,108(2),662–667.

Carvell,C.,Meek,W.R.,Pywell,R.F.,Goulson,D.,&Nowakowski,M.(2007).Comparingtheefficacyofagri-environmentschemestoenhancebumblebeeabundanceanddiversityonarablefieldmargins.JournalofAppliedEcology,44(1),29–40.

Colla,S.R.,Otterstatter,M.C.,Gegear,R.J.,&Thomson,J.D.(2006).Plightofthebumblebee:pathogenspilloverfromcommercialtowildpopulations.BiologicalConservation,129(4),461–467.

Gallant,A.L.,Sadinski,W.,Roth,M.F.,&Rewa,C.A.(2011).ChangesinhistoricalIowalandcoverascontextforassessingtheenvironmentalbenefitsofcurrentandfutureconservationeffortsonagriculturallands.JournalofSoilandWaterConservation,66(3),67A–77A.http://doi.org/10.2489/jswc.66.3.67A

Goulson,D.,Lye,G.C.,&Darvill,B.(2008).Declineandconservationofbumblebees.Annu.Rev.Entomol.,53,191–208.