buffer options for the bay: exploring the trends, the

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Buffer Options for the Bay: Exploring the Trends, the Science, and Buffer Options for the Bay: Exploring the Trends, the Science, and

the Options of Buffer Management in the Great Bay Watershed the Options of Buffer Management in the Great Bay Watershed

Key Findings from Available Literature Key Findings from Available Literature

Shea E. Flanagan Nature Conservancy, New Hampshire Chapter

David A. Patrick Nature Conservancy, New Hampshire Chapter

Dolores J. Leonard Roca Communications

Paul Stacey Great Bay National Estuarine Research Reserve, New Hampshire Fish & Game Department

Follow this and additional works at: https://scholars.unh.edu/prep

Recommended Citation Recommended Citation Flanagan, Shea E.; Patrick, David A.; Leonard, Dolores J.; and Stacey, Paul, "Buffer Options for the Bay: Exploring the Trends, the Science, and the Options of Buffer Management in the Great Bay Watershed Key Findings from Available Literature" (2017). PREP Reports & Publications. 380. https://scholars.unh.edu/prep/380

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BUFFEROPTIONSFORTHEBAY:EXPLORINGTHETRENDS,THESCIENCE,ANDTHEOPTIONSOF

BUFFERMANAGEMENTINTHEGREATBAYWATERSHED

KEYFINDINGSFROMAVAILABLELITERATURE

SHEAE.FLANAGAN1,DAVIDA.PATRICK1,DOLORESJ.LEONARD2,ANDPAULSTACEY3

1THENATURECONSERVANCY,NEWHAMPSHIRECHAPTER,22BRIDGESTREET,CONCORD,NH,[email protected]@TNC.ORG

2ROCACOMMUNICATIONS+,2OLDFIELDSROAD,SOUTHBERWICK,ME,[email protected]

3GREATBAYNATIONALESTUARINERESEARCHRESERVE,NEWHAMPSHIREFISH&GAMEDEPARTMENT,69DEPOTROAD,GREENLAND,NH,[email protected]





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TABLEOFCONTENTS

I. Acknowledgements…………………………………………………….…………………………………………………………………..4A. ExecutiveSummary…………………………………………………….…………………………………………………………………..5B. Whatisabuffer?.…………………………………………………….………………………………………………………………………7C. WhichenvironmentalissuesdowehopetoaddressthroughtheuseofbuffersintheGreatBay

Estuary(GBE)?.…………………………………………………….………………………………………………………………………..10D. Howmightbuffersaddresstheseissues?.………………………………………….………………………………………….13 I.WaterQuality…………………………………………………….…………………………………………………………………………17

i. Reducinginputsofexcessnutrientsandcontaminants......................................18ii. Mediatingsediment.............................................................................................19iii. Influencingwatertemperature............................................................................20iv. Providingorganicinputsintoaquaticsystems....................................................20

II.HydrologicEffects.............................................................................................................................20i. Providingfloodstoragecapacity..........................................................................21ii. Reducingrun-offandstabilizingthechannelbank..............................................21iii. Infiltratingsurfacewater.....................................................................................21

III.HabitatforBiodiversity...................................................................................................................22i. Aquaticmacroinvertebratesandfish...................................................................23ii. Amphibians……………………………………………………………………………………………………..23iii. Reptiles……………………………………………………………………………………………………………24iv. Birds………………………………………………………………………………………………………………..24v. Mammals…………………………………………………………………………………………………………25Table2…………………………………………………….……………………………………………………………………26Table3…………………………………………………….……………………………………………………………………27Table4…………………………………………………….……………………………………………………………………27

E.Whatpreviousandongoingattemptshavebeenmadetoaddressecologicalstressorsandmaintainecosystemservicesusingbuffers,andwhattechnicalbarriershavebeenencountered?.........................28

I. Whatsuccesseshavearisenfrombufferrestorationandprotectionattempts?...........................28i. NorthHampton,NewHampshire.………………………………………….………………………..28ii. ConnecticutRiverWatershed………………………….…………………………………….………..29iii. ChesapeakeBayWatershed…………………………………………………………………………….29iv. ColumbiaRiverWatershed………………………………………………………………………………30v. FoxCreekCanyon,Oregon……………………………………………………………………..……….30vi. BogBrook,NewHampshire…………………………………………………………………..…………30vii. MousamLake,Maine………………………………………………………………………………………30viii. HighlandLake,Maine………………………………………………………………………………………31ix. GilaRiverWatershed……………………………………………………………………………….………31

II. Whatobstacleshavebeenencounteredinbufferrestorationandprotectionattempts?.............32i. ChesapeakeBayWatershed…………………………………………………………………….………32

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ii. ConnecticutRiverWatershed………………………………………………………………………….32iii. Maidstone,Vermont……………………………………………………………………………………….32

III. Whataretheoverarchinglessonslearnedfrombufferrestorationandprotectionattempts?.....34Appendix1…………………………………………………….………………………………………………………………………………………36Appendix2…………………………………………………….………………………………………………………………………………………38Appendix3…………………………………………………….………………………………………………………………………………………40Appendix4…………………………………………………….………………………………………………………………………………………42LiteratureCited…………………………………………………….……………………………………………………………………………….43

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ACKNOWLEDGEMENTS

WewouldliketorecognizetheinvaluablesupportofferedbytheNewHampshireAssociationofNaturalResourceScientists,particularlyRickVandePollandMaryAnnTiltonattheNewHampshireDepartmentofEnvironmentalServices,inassemblingthisliteraturereview.The data provided by NHANRS played a foundational role in crafting this review. WewouldalsoliketothankthemembersoftheBufferOptionsfortheBayprojectteamandadvisorycommitteefortheirkeyfeedbackinguidingtheframeworkanddevelopmentofthisreview.

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A. EXECUTIVESUMMARYInNewHampshire,theneedfortrusted,relevantscienceisexperiencedateveryscaleofbuffermanagement,fromdecisionsmadebypropertyownersatthewater’sedgetothoseofstateagenciessettingpolicyforwhatispermissibleonthatland.Underpinningeachdecisionareaseriesoftradeoffsthatreflectassumptionsheldabouttheimpactofthatchoiceontheenvironment,theeconomy,andthewell-beingofthecommunity.ThisliteraturereviewseekstosupportthesedecisionsandgroundtruththoseassumptionsbypresentingasynthesisofavailablescienceonthesubjectofbuffermanagementfortheGreatBayEstuary(GBE)anditstributariesinsoutheastNewHampshire.

ThereviewwascommissionedbytheBufferOptionsfortheBay(“BOB”)technicalteam,whichisacomponentofthelargerintegratedassessmentBOBprojectentitled“ExploringtheTrends,theScience,andtheOptionsofBufferManagementintheGreatBayWatershed.”BufferOptionsfortheBayisagrant-sponsoredcollaborationofpublic,academic,andnonprofitorganizationsdedicatedtoenhancingthecapacityofNewHampshirestakeholderstomakeinformeddecisionsthatmakebestuseofbufferstoprotectwaterquality,guardagainststormsurgeandsealevelrise,andsustainfishandwildlifeintheGreatBayregion.Inkeepingwiththisgoal,thisreviewhasbeeninspiredbytypicalquestionsthatariseinthecourseoflocalbuffermanagement.Forexample,whatroledobuffersplayinprotectingwaterquality?Inmitigatingtheimpactsoffloodingandsealevelrise?Providinghabitatforprotectedorcommerciallyimportantwildlife?Enhancingpropertyvalues?Whatdoesthesciencesuggestwedotoensurethatbufferscancontinuetosupporttheseservices?Howmucharepeople“willingtopay”tomaintainoravoidlossofthesefunctions?

Tohelpaddressthesequestions,thisreviewconsideredbothprimaryliteratureandpreviousliteraturereviews.ThelatterincludesrecentworkundertakenbytheNewHampshireAssociationofNaturalResourceScientists,aswellasstudiesbySweeneyandNewbold(2014),WashingtonStateDepartmentofEcology(Sheldonetal.2005),RhodeIslandDivisionofPlanning(MetzandWeigel2013),NewHampshireAudubon(Chaseetal.1995),UniversityofGeorgia(KirwanandMegonigal2013;Wenger1999),EnvironmentalLawInstitute(EnvironmentalLawInstitute2008),andGoodForestryintheGraniteStateSteeringCommittee(Bennett2010).Thereisanincrediblevolumeofscientificliteraturerelevanttothetopicofbuffers,andourintentionwasnottobeexhaustiveinthisreview;insteadwefocusonthemostlocallyrelevantsciencethatcanbeusedtoaddresstheaforementionedquestionsinNewHampshire.

Fromthisreview,wefoundthatwhilethebestavailablescienceprovidesclearguidancetoinformdecision-makingrelatedtobuffermanagementinNewHampshire,researchquestionsremain.Forexample,itisclearthatbufferscanhelpprotectmanyofthebenefitsthattheGBEanditstributariesprovidetosurroundingcommunitiessuchasrecreationalopportunitiesandhealthyfisheries.Thiscapacity,however,dependsonabuffer’sparticularattributes,includingitswidth,acharacteristicofcriticalimportancetoallstakeholdersandatopicthathasreceivedconsiderableattentioninthepeer-reviewedliterature.Whilemanypapersmakerecommendationsforbufferwidth,thesestudiesoftenseektoaddresshowwideabufferwouldneedtobetomaintainthetypesofecologicalfeaturesor

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functionsfoundinentirelynaturallandscapes,suchasanassemblageofforest-associatedbirds.Consequently,theytendtofocusonrelativelywidemarginsoflandthatmaynotbepractical,orevenfeasible,insomesettings.Whileitiscriticallyimportantthatweunderstandtheseminimumwidthsandhencewhataspectsoftheenvironmentwillbedegradedwithnarrowerbuffers,itisalsoimportantthatweunderstandwhatfunctionsmightbeprovidedbythenarrowerbuffersthatmaybetheonlyfeasibleoptionincertainsettings.Relativelyfewstudieshavefocusedonthetopicofnarrowerbuffers,withtheexceptionofresearchonnutrientremoval.Asaresultofthelimiteddataonnarrowerbuffers,thisreviewputsforwardminimumbufferwidthrecommendationsbasedonwhatisnecessarytomaintainbufferfunctions,withthecaveatthatwedonotalwaysfullyunderstandhowwellnarrowerbuffersmayfunction.Theserecommendationsaresupportedbypertinentexamplesofspecificanalysesfromtheliterature.

Inadditiontothelimiteddataavailabletohelpinunderstandingtheroleofnarrowbuffers,achallengealsoexistsinquantifyingadirectrelationshipbetweentherestoration,maintenance,orlossofbuffersinreal-worldscenariosandacorrespondingchangeinthefocalecosystemservice.Mostprimaryresearchonbufferefficacyisconductedundercontrolledconditionswithintheconfinesofaresearchproject.Underthisapproach,unwantedvariabilityintheenvironmentisminimizedinordertotestspecifichypotheses.However,whenbuffersareutilizedinpractice,thereistypicallyconsiderablevariabilityintheenvironment,accompaniedbyalackofreplication–forexample,oftenasinglewatershedisevaluated.Thismakesthetypeofstatisticalanalysesdeployedinexperimentalresearchdifficult.Understandingthischallengeisimportant,asitcanleadtoaconclusionthat,inpractice,buffersarenotaseffectiveasindicatedbymostprimaryresearch.However,therealityisthatthefindingsofprimaryresearchholdtrue,i.e.bufferscanbeaneffectivetool,butthevariabilityofcomplicatingfactorsinthenaturalenvironmentcaneithermaskoroverridetherolethatbuffersplayininfluencingecosystemservices.ThesciencesynthesizedinthisdocumentisintendedtobeusedbytheBOBprojectteam,althoughtheexplicitintentistothencreateanumberofinformationalproductsthattranslatethisscienceintoamoreaccessibleformforendusers.Ultimately,theproductsthatareshapedfromthisreviewwillbeofservicetoallbuffermanagementstakeholdersintheGreatBayregion,includinglandownersandtheconsultantswhoworkwiththem,regulatoryagenciesandmunicipalities,conservationorganizationsandfoundations,andscientistsinterestedinconductingresearchthatwillleadtomoreeffectivebuffermanagement.

Science,however,isonlyonepieceofthebuffermanagementpuzzle.Toaugmentthisreview,theBOBcollaborativehasconductedananalysisofregulatoryandnon-regulatorypolicyoptionsforNewHampshire,aneconomicanalysisofthevaluesplacedonthewaterqualitybenefitsprovidedbybuffers,abuffer-focusedGISanalysisoftheGBEregion,andanassessmentofthebarriersandopportunitiesrelatedtobuffermanagementatthecommunitylevelintheExeter/Squamscottsubwatershed.

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Theresultsoftheseanalyseshavebeencapturedinindividualreports.They’vealsobeenintegratedintoaframeworkintendedtoinformdiscussionsaroundbuffermanagement,restoration,andprotectionintheGBEregion.Weanticipatethatthisframeworkwillopenthedoortonewandneededresearch;strategicandcomplementaryinvestmentsbystateagencies,nonprofits,andfoundations;andacollectivestrategyforoutreachprofessionalstoworkwithtownsonadvancingeffectivebufferpolicyandpracticeatthecommunitylevel.

B. WHATISABUFFER?Beforeembarkingonareviewofscientificinformationrelatingtobuffers,itisimportanttounderstandwhatismeantbythisconcept.Suchunderstandingisconfoundedbytherangeofterminologyusedinrelationtobuffers.Twoormoretermsmaybeusedtorefertowhatisessentiallythesameconcept,orthesametermmaybeusedindifferentcontextswithdifferentunderlyingmeanings.Thiscanleadtoconfusionthathinderseffectivebuffermanagement.

Forthepurposeofthisreview,bufferisdefinedasanuplandareaadjacenttowetlands(Sheldonetal.2005),andwetlandisdefinedasatransitionalzonebetweenterrestrialandaquatichabitatsthatincludeslandscapefeaturesthatcontainorconveywaterandsupportuniqueplantsandwildlife(EnvironmentalLawInstitute2008)1.Usingthesedefinitions,examplesofwetlandscouldincludestreams,rivers,ponds,lakes,bogs,andvernalpools.ThisreviewisfocusedontheGreatBayEstuary(GBE)region,andisthereforeconcernedprimarilywithcoastalbuffers(i.e.theboundaryadjacenttotidalwatersoftheestuary),buffersadjacenttostreamsandriversthatflowintothebay,andbuffersadjacenttowetlandsthatarehydrologicallyconnectedtothewatersofthebay.Thetermslistedbelowareoftenused,sometimesinterchangeably,whenreferringtoareasthatfittheaforementioneddescriptionofbuffers.

● Buffer● Vegetatedfilterstrip● Bufferstrip● Riparianarea● Riparianzone● Ripariancorridor

Whileeachofthesetermsmaybemorecommonlyemployedindifferentarenas(e.g.regulation/policyversusecologicalconditionorlocation),ormoretypicallyassociatedwithacertaindefinition,thereisconsiderablemixingofusage.GiventhattheBOBprojectisnotfocusedonanysinglespecificfunctionofbuffers,weuse‘buffer’throughoutthisdocumentinreferencetotherangeoffunctionsthatmaybeencompassedbyallofthetermslistedabove.

1One’sunderstandingoftheterm‘buffer’isofteninformedbyone’sbackgroundorexperience.Aplannerordevelopermayconsiderbufferstobedefinedregulatoryareasinwhichdevelopmentmaybeconstrained.Ascientistorecologistmayhaveamuchbroaderandlessrigidunderstanding,characterizedmorebytheecologicalsetting,form,andfunctionthanbyasimpleregulatoryboundary.

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Inadditiontothevariationinterminology,aconsiderablerangeofdefinitionsareusedinreferencetobuffers.Perhapsthesimplestis“theuplandsadjacenttowetlands”(EnvironmentalLawInstitute2008),i.e.astrictlyspatialdefinition.However,theconceptofabufferismoretypicallyappliedtodescribearangeoflandmanagementpracticesintheseuplandareas.Thesepracticescanrangefromrestrictingactivitiesfromwithinaspecifieddistancefromawaterbody(alsocommonlytermeda‘setback’)tocomplexrecommendationsforhabitatmanagementdesignedtoprotectspecificgroupsoforganismsorfunctionalroles.Forexample,Reed(2013)definedbuffersas“vegetatedstripsoflandseparatingrunoff-andpollutant-contributingareasfromsurfacewaters.”Similarly,Chaseetal.(1995),definedabufferas“anaturallyvegetateduplandareaadjacenttoawetlandorsurfacewater.”Conversely,SemlitschandJensen(2001)recommendedthefollowingnuanceddescriptionforamphibiansandreptiles:“Weproposetheuseofstratifiedcriteriathatwouldincludeatleastthreeterrestrialzonesadjacenttocoreaquaticandwetlandshabitats:(1)startingfromthewetlandedge,afirstterrestrialzonewouldbufferthecoreaquatichabitatandprotectwaterresources;(2)startingagainfromthewetlandedgeandoverlappingwiththefirstzone,asecondterrestrialzonewouldcomprisethecoreterrestrialhabitatdefinedbysemi-aquaticfocalspeciesorspecies-groupuse;and(3)startingfromtheoutwardedgeofthesecondzone,athirdterrestrialzonewouldbufferthecoreterrestrialhabitatfromedgeeffectsandsurroundingland-usepractices.”

Bearinginmindthisrangeofdefinitions,ingeneral,theterm‘buffer’isusedtodenoteaspecifiedareaofuplandhabitatadjacenttostreams,rivers,ponds,lakes,and/orotherwetlandtypes,typicallyassociatedwithmaintainingorpromotingoneormoreecologicalorsocio-economicfunctions,andwithspecificlanduseregulationsimplementedwithinthisareatomeettheseobjectives.Theselandusepracticescaneitherbeactivitiesthatareprohibited,suchasconstruction,orencouraged,suchasmaintenanceofnaturalvegetation.Intheecologicalliterature,theterm‘buffer’generallyrelatestothenaturallyvegetatedzoneadjacenttowetlandsandprecludesconsiderationofgrayinfrastructure(i.e.stormsewers,culverts,pipes,otherhuman-engineeredsystems)thatmightservesomeofthesamefunctionsasgreenornaturalinfrastructure(i.e.forests,wetlands,othernaturalecosystems).

‘Setback’and‘jurisdictionalzone’aretwotermsthatareoftenusedinsimilarcontextsasbuffers–specifically,regardingtheregulatorycapacityforwaterbodyprotection.However,setbacksandjurisdictionalzonesaredistinctfrombuffers.Thesetermswillnotbecoveredindepthinthisreview,butthefollowingbackgroundinformationisprovidedtohelpdifferentiatesetbacksandjurisdictionalzonesfrombuffers.

Muchlike‘buffer,’theterm‘setback’hasarangeofdefinitions.Asetbackisgenerallyaspecifieddistancefromthewaterbodywithinwhichcertainactivitiesarerestricted,suchasbuildingconstructionorestablishmentofasepticsystem.Wetlandsetbacksarenotnecessarilynaturallyvegetated,assetbacksaretypicallyaimedspecificallyatmaintainingwaterqualityratherthanthebroadergoalsoftentargetedbybuffers.However,theterm‘setback’issometimesusedinterchangeablywith’buffer.’An

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exampleofonedefinitionis“adistancerequirementfromcertainactivities,”fromNewHampshireDepartmentofEnvironmentalServices(NHDES).Asanotherexample,theNationalOceanicandAtmosphericAdministrationdefinesasetbackas“adistancelandwardofsomecoastalfeature(e.g.theordinaryhighwatermarkwithinwhichcertaintypesofstructuresoractivitiesareprohibited”(Lemieuxetal.2004).

Ajurisdictionalzoneisanotherareainwhichrestrictionsmaybesettoprotectawaterbody.Ajurisdictionalzoneisgenerallytheboundaryextendingoutfromawaterbodytowhichagoverningagency(i.e.stateand/ormunicipality)hasregulatorycapacity.Withrespecttobuffers,ajurisdictionalzonetypicallyincludesandextendsbeyondbufferandsetbackwidths.TheNHDESWetlandsBureaudefinesajurisdictionalzoneas“anareathatissubjecttoregulationunderRSA482-A[FillandDredgeinWetlands],asdescribedtherein.”Anillustrationofthetypicalspatialarrangementofbuffers,setbacks,andjurisdictionalzonesisprovidedinFigure1below.

Figure1.Conceptualillustrationofbuffer,setback,andjurisdictionalzoneextentsinrelationtothewaterbody(nottoscale).

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C. WHICHENVIRONMENTALISSUESDOWEHOPETOADDRESSTHROUGHTHEUSEOFBUFFERS

INTHEGREATBAYESTUARY(GBE)?TheprincipalthreatstotheGreatBayEstuary(GBE)arewellsummarizedinthePiscataquaRegionEstuariesPartnership’s(PREP)2013StateofOurEstuariesReport(PREP2013)andtheGreatBayNon-PointSourceStudy(Trowbridgeetal.2014).Thesedocumentsandtheresourcestheydrawupondescribeacomplexrangeofinterrelatedstressorsthathaveledtoecologicaldegradationandassociatedsocio-economiccosts,includingterrestrialpollutantsfromsettlementsandagriculture,changesinsedimentation,changesinwatertemperatureandlevelsofdissolvedoxygen,lossofnaturalhabitatduetolandconversion(Fig.2a,Fig.2b),declinesinoysterreefsandeelgrassbeds,increasesininvasiveaquaticspeciesandnuisancenativemacroalgae,alteredflowregimesandbarrierstothepassageofaquaticorganismsbetweenmarineandfreshwaterenvironments,increasedfloodinganderosion,andsealevelrise.Buffershavethepotentialtohelpinamelioratingalloftheseissueswiththeexceptionofinvasivespecies,aquaticorganismpassageforstrictlyaquaticspecies,sealevelrise,andchangesinestuarinewatertemperatureasaresultofoceanwarming.

Figure2a.ImpervioussurfacecovertrendsintheGreatBayEstuaryregion.ProvidedbyPiscataquaRegionEstuariesPartnership(PREP2013).

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Figure2b.ImpervioussurfacecovertrendsintheGreatBayEstuaryregion.ProvidedbyPiscataquaRegionEstuariesPartnership(PREP2013).

Nitrogen/nutrientloadingandsedimentinputstotheGBEremainsignificantdriversofecologicaldegradation,withhighinputsfacilitatedbytheincreasingamountofimperviouscoverandlossofnaturalcoverwithinthewatershed(Trowbridgeetal.2014).Excessnutrientinputstoaquaticsystemsreducewaterqualityanddecreasespeciesrichness.Sixty-eightpercentofthenitrogenintheGBEsystemcomesfromnonpointsourcesspreadacrossthewatershed,withtheremaindercomingfrommunicipalwastewatertreatmentdischarge.Nonpointsourcesincludeatmosphericdeposition,fertilizers,humanwastefromsepticsystems,andanimalwaste.Humanwastefromsepticsystemscontributes29percent(~240tons/year)ofnitrogeninputstotheGBEandisthelargestnonpointloadafteratmosphericdeposition(42percent).Thirty-fourpercentofnonpointsourceloadsweredeliveredthroughstormwater(surfacewaterofabnormalquantityresultingfromheavyrainsorsnowfall).

Thelossofbuffersisparticularlyimportantinthecontextofnutrientandsedimentinputs.Nitrogeninputsarecloselylinkedtolevelsofdissolvedoxygen(DO):Ingeneral,thetidalmixingintheGBEmeansthatlevelsofDOareaboveminimumwaterqualitystandardsof5mg/L.However,tidalriversflowingintotheGBEregularlyfallbelowthisthreshold,posingarisktoaquaticorganisms(PREP2013).SuspendedsedimentscontinuetoincreaseintheGBE,havingrisenby12percentfrom1976to2011.Thesesuspendedsedimentsresultfrombothwave/tidaldisturbancestoestuarinesilts,andrun-offdeliveryofterrestrialsedimentsintothebay(i.e.acombinationofresuspensionofexistingsedimentsinthebay,andincreasedterrestrialinputs).Thesethreatsfromnutrientandsedimentinputscanbeamelioratedbytheuseofbuffers.

Increasednutrientlevels,coupledwithsedimentationanddiseaseoutbreaks,arelikelytobeimportantcontributorstodeclinesofeelgrassandoysterreefareaswithinthebay(Fig.3).Historically,therewere

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approximately1,000acresofoysterreefsintheGBE,withonly~10percentofthisareanowremaining(PREP2013).Similarly,eelgrassbedsoncedominatednearshorehabitatinthebay,buttheirdistributionhasdeclinedby44percentsince1996,andtheirbiomasshasdecreasedby79percent(Short2016).Thelossofthesehabitatsisparticularlynotablegiventheimportantecologicalfunctionstheyprovide.Theseincludewaterfiltrationbyoysters,importanthabitatforjuvenilefishandaquaticinvertebrates,andestuarinesedimenttrapping.Asthesehabitatshavedeclined,thereisthepotentialforafeedbackmechanismwhereintheincreasedsedimentationanddecreasedwaterqualitypartiallyresultingfromoysterandeelgrassdeclinescreatesconditionsinwhichitishardertorestorethesesamehabitats.Inadditiontothisecologicalfunctionality,oystersandseagrassmeadowsarecommerciallyvaluable.Forexample,astudyofMediterraneanseagrassmeadowsestimatedtheywereannuallyworth$119millionforcommercialfishing(Jacksonetal.2015).

Figure3.EelgrasscovertrendsintheGreatBayEstuaryregion.ProvidedbyPiscataquaRegionEstuariesPartnership(PREP2013).

Widespreadconversionofnaturalhabitatshasbeendeemedtheleadingcauseofbiodiversitylossworldwide.Riparianhabitatisatparticularriskfromconversionastheseareasareoftenhighlysuitable

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foragricultureanddesirablelocationsforhumandevelopment.IntheUnitedStates,~1percentofriparianareaswerelostfrom1972to2003(PuseyandArthington2003).Whilethisfiguremaynotseemhigh,itisimportanttorecognizethatthisrepresentsacontinuedlossofhabitatontopofhistoricallossinmanyplaces.IncoastalNewHampshire,muchofthislandconversioncanbeattributedtoagrowinghumanpopulationasaresultofproximitytotheexpandinggreaterBostonarea.From1990to2010,thepopulationintheregiongrewby19percentwithaconcomitant120percentincreaseinimperviouscover(representing9.6percentofthelandarea).Thelossofbuffersisofparticularconcerngiventhattheysupportawiderangeoforganismsassociatedwithbothterrestrialandaquatichabitats(Naimanetal.1993)andarethoughttoprovideconnectivity,i.e.allowmovementoforganismsacrossthelandscape,particularlyinsituationswhereuplandhabitatadjacenttothebufferhasbeenlost(Machtansetal.2002,BeierandNoss2008).

Inadditiontohabitatloss,conversionofriparianhabitatincreasestheloadofstressorssuchasnutrientsandsedimentwithlittleopportunityforamelioratingthesethreatsbeforetheyenterwetlands.Areasclosetowaterwayscontributeasignificantproportionofinputs(~10percentofnitrogenloadingcomesfromwithin~650ft.ofwaterways)(PREP2013).Asanexampleoftheconsequencesofconversion,researchintheNHSeacoastregionfoundthatwaterqualityandbiologicalconditionsin-streamdeclinedasthepercentageofurbanlandincreasedwithinan~80ft.buffer(Deaconetal.2005).

Sealevelrise(SLR)isalsoasignificantthreattotheGBE.Whilesealevelsarerisinginmanyareasoftheworldasaresultofmeltingpolaricecausedbyglobalclimatechange,thenortheasternUnitedStateshasbeenidentifiedasahotspotofacceleratedSLR,withrates3to4timeshigherthanglobalaverages(Sallengeretal.2012).SLRwillleadtoextensivecoastalflooding(Kirshenetal.2008),andmayleadtothelossofimportantcoastalhabitat,suchasdunesandsaltmarshes,dependingontherateofSLRandabilityofhabitatstoredistributeinresponsetothesechanges(Craftetal.2008).ThehighdensityofhumansettlementandassociatedinfrastructureinlowlandareasadjacenttotheGBEalsoputsmanycommunitiesatsignificantriskofcoastalfloodingasaresultofSLR(Hamiltonetal.2010).

D. HOWMIGHTBUFFERSADDRESSTHESEISSUES?Bufferscanprovidearangeofecologicalbenefitstohelpinamelioratingthethreatslistedabove(summarizedinTable2withamoredetailednarrativedescriptionprovidedinthefollowingsections).However,beforedescribingtheroleofbuffers,itisimportanttorecognizethattheprovisionoftheseservicesishighlydependentonboththewiderlandscapewithinwhichthebufferisfoundandthelocalizedcontextofthebufferitself(Wenger1999,Franzenetal.2006,Bardgettetal.2013,Raneyetal.2014).Landscapecontextisparticularlyimportantasitwillinfluencethenutrientloadingthatthebufferwillintercept.Forexample,ifabufferissituatedincloseproximitytoalargeareaofcommercialdevelopment,thereislikelytobeahigherloadingofcontaminantscomparedtoalargelyforestedwatershed.Similarly,thefunctioningofthebufferwillbeinfluencedbyarangeofcharacteristicsincludingvegetation,widthofthebuffer,slope,andunderlyingsoils.Wehaveattemptedtodiscussthesetopicsthroughoutthisliteraturereview,butanin-depthdiscussionoftopicssuchasthelinkage

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betweenwatershedmanagement,land-usechange,andnonpointsourcepollutionisbeyondthescopeofouranalyses.Researchhasshownthattheeffectivenessofpollutionreductionby‘green’infrastructure,ornaturalareasthatprovideecosystemservices(inthiscase,buffers),isnotonlycomparabletothatachievedby‘gray’infrastructure(constructedstormwaterinterventions),butthatgreeninfrastructuretypicallycostsmarkedlyless(Talberthetal.2012).Aswatershedshavedegradedovertime,costsfortraditionalwatertreatmenthavedoubledforaboutoneinthreelargecitiesglobally(McDonaldetal.2016).Specifically,from1900to2005,90percentofurbansourcewatershedsexperiencedsomewatersheddegradation,withtheaveragepollutantyieldofurbansourcewatershedsincreasingby40percentforsediment,47percentforphosphorus,and119percentfornitrogen(McDonaldetal.2016).Byelectingtousenatural/greeninfrastructuresuchasbuffersandwetlands,stakeholdersavoidwatersheddegradation.Thisavoidanceinturnhelpsmaintainwaterqualityandreducestreatmentcosts,asthenaturalcapitalofnaturallandcoverfunctionsasanalternativetoinvestmentingrayinfrastructure(McDonaldetal.2016).Asanexampleofthecomparisonbetweengreenandgrayinfrastructure,buildingawastewatertreatmentsystemusingconstructedwetlandscostsaround$5pergallonofcapacitycomparedtoapproximately$10pergallonofcapacityforaconventionaladvancedtreatmentfacility(Fosteretal.2011).Additionally,greeninfrastructureisestimatedtobethreetosixtimesmoreeffectiveinmanagingstormwaterper$1,000investedthanconventionalmethods.Forexample,thelargelyintactfloodplainsandwetlandswithinVermont’sOtterCreekwatershedwereestimatedtohavereduceddamageby54to78percentacrosstenfloodeventstothetownofMiddlebury,andby84to95percentforTropicalStormIrene(Watsonetal.2016).Theannualvalueofthesefloodmitigationservicesexceeded$126,000andmaybeashighas$450,000.Greeninfrastructurealsofunctionsbetterthangrayinfrastructureinclimateadaptationandresiliencebyprovidingasuiteofco-benefits,suchasimprovingairquality,reducingurbanheateffects,loweringenergydemand,andevenincreasinglandvaluesbyupto30percent(Fosteretal.2011).Beforeconsideringtheextenttowhichbufferscanhelpsupportspecificecosystemservices,itisimportanttoaddresstheoverarchingtopicofbufferwidth.Thisthemehasreceivedconsiderableresearchattention,withanumberofreviewpapersofferingrecommendationsfordifferentobjectives(e.g.Leeetal.2004;KirwanandMegonigal2013).Itisworthnoting,however,thatstudieshavetendedtofocusonrelativelywidebuffersthatmaynotbefeasibleinsomesettings,suchasareaswherehighdevelopmentpressureimpedestheabilitytoestablishbuffersoftherecommendedwidth.Asaconsequence,thereissomeconcernthattheefficacyofnarrowerbuffersmaynotbewellunderstood(HickeyandDoran2004).Thisreviewprovidesfixedwidthbufferrecommendations,butwerecognizetheutilityofvariablebufferwidthrecommendationsaswell.Variablewidthbuffersarebuffersthatdonotmaintainauniformwidththroughouttheirextent(Fig.4,Table1).Variablewidthbufferscanprovideanimportanttoolformeetinganecosystemservicetarget(forexample,removalofnutrients),butwhereitisinfeasibleto

15

maintainorrestoreafixedwidthbuffer.Examplesoffactorsthatprecludetheuseofafixedwidthbuffercanincludeadjacentlanduse,siteandstreamconditions(i.e.topography,soil,hydrology)andplaceswherebuffershavebeenlostandrestorationisnotfeasible(EnvironmentalLawInstitute2003;Aunanetal.2005).Forexample,inplaceswherehabitatlosshasalreadyledtoafragmentedorasymmetricalbuffer,greaterwidthswillbeneededinremaininghabitattomaintainbufferintegrity(i.e.forthebuffertoprovidethesamelevelofecosystemservices)(Bartonetal.1985).Variablewidthbuffers,specificallylargerwidths,mayalsobeemployedtoprotectpristineorhighly-valuedriparianareas;areasclosetohigh-impactlanduseactivities;orareaswithsteepbanks,sparsevegetation,orhighlyerodiblesoils(EnvironmentalLawInstitute2003).ArecentreviewundertakenbytheNewHampshireAssociationofNaturalResourceScientists(NHANRS)employedacomprehensiveliteraturereviewtofocusspecificallyonthetopicofbufferwidths.GiventheoverlapbetweenourreviewandtheworkofNHANRS(bothfocusingonbuffersinthestateofNewHampshire),wehavesummarizedavailablerecommendedminimumbufferwidthstoachievedifferentobjectivesattheendofeachsectionbelowandinTable3.OnecanreferencetheNHANRSreviewforacompletelistofthestudiesfromwhichtheserecommendationsweredrawn(Appendix1,Appendix2,Appendix3).

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Figure4.Theoreticalillustrationofsamplerecommendedriparianmanagementzone(RMZ)delineationsforstreamsofvariousorders,forthepurposeofforestmanagement.ReproducedfromGoodForestryintheGraniteState(Bennett2010).Table1.SampleriparianmanagementzoneguidelinesinNewHampshireforvariouswaterbodysizes,forthepurposeofforestmanagement.ReproducedfromGoodForestryintheGraniteState(Bennett2010).

LegallyRequired RecommendedRiparian

ManagementZone(ft.)

NoHarvestZone(ft.)

RiparianManagementZone(ft.)

NoHarvestZone(ft.)

IntermittentStreams

None None 75 None

1stand2ndOrderStreams

50 None 100 25

3rdOrderStreams 50 None 300 504thOrderandHigherStreams

150 None 300 25

Pond(<10acres) 50 None 100 NoneLakeorGreatPond(>10acres)

150 None 300 25

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Onecaveatwheninterpretingthefindingsofdifferentstudiesinregardstobufferwidthisthattherewassomevariabilityinhowthewidthofabufferwasdeterminedbasedonwhatconstitutedtheedgeofthebuffer.Giventheabundanceofstudiesfocusingonbufferwidth,oursenseisthatthisadditionalvariabilityisunlikelytohavestronglyinfluencedrecommendations,althoughtherelevanceofthisissueincreaseswhentherearerelativelyfewstudiessupportingspecificguidance.ThehistoryofdevelopmentandreforestationseenthroughoutNewEngland,andparticularlyincoastalNewHampshire,meansitisalsoimportanttonotethatinindividualsites,bufferfunctionmaybeinfluencedbyprioralteration,suchaswheresoilshavebeenheavilymodifiedbypastagriculture.Caveatsaside,theoverarchingmessageregardingtherelationshipbetweenbufferwidthandprovisionofecosystemservicesisasimpleone:ingeneral,widerandmoreforestedbuffersprovidegreaterbenefitstowaterqualityandbiodiversity.Anotherkeythemethatemergedfromresearchfindingsistheinfluenceoflandscapecontextonbufferefficacy,includingfactorssuchastopography,thelocationofstressorsources,andtheunderlyingwatertable.Furthermore,longer,continuousbuffersaremoreeffectivethanfragmentsofgreaterwidthsforhydrologicfunctions,reducinggapsinmaintainingwaterquality,andwildlifehabitat(Fischeretal.2000).Additionally,widerbuffersmaybewarrantednexttoparticularlysensitiveresources(forexample,impairedwaterbodies),andclosertotheGBE,wherethereislessopportunityforexcessnutrientsthatenterstreamsandriverstobeamelioratedbeforeenteringthebay,althoughresearchhasshownthatbuffersalongheadwaterstreamsthatfeedintoatargetwaterbodyhaveagreaterinfluenceonoverallwaterqualitythanthosedirectlysurroundingthatwaterbody(Fischeretal.2000).Thefollowingsectionsprovideamoredetailedsummaryofthestateofcurrentscientificknowledgeregardingbufferwidthandtheprovisionofspecificecosystemservices.InTable4,weofferasinglerecommendedminimumbufferwidthforeachspecificecosystemservicedrawnfromourliteraturereview.Inadditiontotheserecommendations,wehavealsocompiledgapsinthebestavailablescienceinAppendix4that,ifaddressedthroughfurtherresearch,wouldimprovetherecommendationsweareabletoofferpractitionersregardingtheuseofbuffers.Itisimportanttokeepinmindthatbufferwidthisoneofseveralfactorsthatdetermineabuffer’sabilitytoprovideavarietyofservices–consideringbufferwidthalongsidelinearextent,vegetationcomposition,andlevelofpermanentprotectionfacilitatesmoreholisticandeffectivebuffermanagement.Whilebufferwidthisanimportantindicatorofhowwellabuffermayprovideecosystemservices,thecompositionofthebufferisalsoakeyfactorindetermininghowwellabufferfunctions.Buffersthatarenaturallyvegetatedgenerallyprovideecosystemservicestoagreaterextentthanbuffersthataresparselyvegetatedorhavebeenclearedoraltered,suchasaforestedbufferthathasbeenconvertedtograss(Bentrup2008,Castelleetal.1992,FischerandFischenich2000).Tocompare,nitrogenuptakeandretentionweresignificantlyhigherinforestedbuffersitescomparedtoherbaceoussites–aretentiondifferencebetween99percentand84percent,respectively,inonestudy(HaycockandPinay1993,Heftingetal.2005).Buffersconsistingofnativevegetationperformbetterwhenthevegetationiswell-adaptedtositeconditionsanddiverse,sothebuffer’svegetationcapturesawidearrayof

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environmentaltolerancesthatsupportanumberoffunctions(FischerandFischenich2000).Thebufferisthereforebetterabletoberesilientinthefaceoffluctuatingenvironmentalvariables.Whenrestoringbuffers,thisdiversitycanbeachievedthroughutilizinganarrayofspecies,growthforms,andlifehistories.Overall,naturallyvegetated,diversebuffersaremoreeffectiveatreducingpollutionintothewaterbodythansparselyvegetated,homogenousbuffers.Insummary,bufferscanbeemployedtoprovideavarietyofecosystemservicesandmitigateahostofenvironmentalissues,buttheextenttowhichbuffersdeliverthesefunctionsdependsgreatlyonthecharacteristicsofthebufferitselfaswellasthelargerlandscapecharacteristicssurroundingthebuffer.Acentralmetricinassessingtheextenttowhichabufferisprovidingcertainfunctionsisthewidthofthebuffer.Inthefollowingsections,threeoverarchingthemesofecosystemservicesthatbuffersprovide–waterquality,hydrologiceffects,andhabitatforbiodiversity–aredissected.Thisanalysisservesasanassessmentofhowbuffersspecificallydeliverthesefunctionsandofwhatwidthsaregenerallyadequatetoprovidetheseservices.I. WaterQualityBufferscontributetothemaintenanceofwaterqualityinavarietyofoftensynergisticways.Forinstance,sedimentremovalbybuffersmayalsoremovephosphorusboundtosedimentparticles.Anumberofstudieshavemadegeneralrecommendationsforthewidthofbuffersneededtomaintainoverallwaterquality.Thelowestrecommendationis16-foot.(FischerandFischenich2000),althoughthemajorityofstudiesprovideaminimumwidthof100-foot(Appendix1).Mostofthepublishedresearchontheefficacyofbuffersforpromotingwaterqualityhasfocusedonnaturallyvegetatedhabitat,anditisfromthisbodyofworkthatourrecommendationsaredrawn.However,setbacksthatpreventcertainlandusesorstructures,suchastheinstallationofasepticsystemorconstructionofabuilding,withinacertaindistancefromawaterbodycanhelptomaintainwaterqualitybyreducingerosion,pollutantrunoff,andrunoffflowvolumeandvelocity.Thefollowingsectionprovidesadetailedcommentaryregardingtheroleofbuffersinhelpingtoaddressspecificcomponentsofwaterquality.i. ReducinginputsofexcessnutrientsandcontaminantsImplementingbuffershasbeenshowntobeaneffectiveapproachinreducingthetransportofnitrateandphosphatefromagricultureanddevelopment(PeterjohnandCorrell1984,EnvironmentalLawInstitute2008).Nutrientsareabsorbedintothebuffersediment,takenupbyplantbiomass,andimmobilizedbymicroorganismsthroughdenitrification(Hruby2013).Asphosphorusprimarilyentersbuffersattachedtosedimentsorasorganicmaterial(Wenger1999),theroleofthebufferinreducinginputstowetlandsconformstothesamemechanismsasthatofreducingsedimentinputsingeneral.Experimentalresearchhasdemonstratedthatevennarrowgrassbuffershavethecapacitytoreducephosphorusinputs.Forexample,a15-foot(4.6m)grassbufferstripremoved18to71.5percentoftotal

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phosphorus(Wenger1999).Whenincreasedto31-foot(9.6m),grassbuffersremoved46to79percentofphosphorus.Insomecases,removalofphosphorusandnitrogenbybuffersapproached90to100percent(HickeyandDoran2004).Oneimportantcaveattotheseexperimentalfindingsisthattheeffectivenessofthebuffersdecreasedovertime,presumablyduetopreviously-trappedphosphorusbeingre-mobilized(Wenger1999)andsoilsbecomingsaturatedbynitrogen(WoodsHoleGroup,Inc.2007).Itisalsoimportanttonotethatbuffereffectivenessmayvaryinsitu,sincepercentremovalsaredependentuponinputload.Furthermore,thedepthofthewatertableinrelationtorootbiomasswithinthebufferlikelyplaysanimportantroleininfluencingratesofnutrientandcontaminantuptake(Marczaketal.2010).Lastly,whilegrassbuffersmayeffectivelyreducenutrientinputsincertainsettings,forestedbuffersmaybemoreeffectiveinprovidingabroadersuiteofecosystemservices.Bearinginmindthesecaveats,bufferswithmorehydricsoil,flattertopography,andahigherwatertablearetypicallybetterabletoremovepollutants.BasedonmodelsdevelopedfortheGBE,watershedconservationefforts(i.e.protectionofwetlandsandforests)couldreducenitrogeninputstothebayfromthreeto28metrictonsperyear(Bergetal.2016).Buffersarealsocapableofstabilizingotherpollutants,althoughthebufferwidthsnecessaryforeffectiveremovalhavenotbeenaswell-studied.Bufferscanrenderpathogensharmlessastheyarecarriedinsubsurfaceflowthroughthesoil,neutralizeaciddepositedbyacidrainthroughuptakeintotheforestcanopy,andstabilizesomemetalsthroughadsorptiontosoilparticles(Chaseetal.1995).Furthermore,buffersprovidefiltrationsufficienttotrapfuelandlubricantsfromupslopelanduses(Bennett2010).Thefollowingisasummaryoftheminimumrecommendedbufferwidthsnecessarytoprovidereductionofexcessnutrientandcontaminantinputs.Muchofthepollutantremovalmayoccurwithinthefirst15to30feetofabuffer,butbuffersrangingfrom30to100feetormorewillremovepollutantsmoreconsistently(EnvironmentalLawInstitute2008).Basedonavailableliterature,theminimumbufferwidthneededforeffectivereductionofnitrogenis60feet.(CorrellandWeller1989),andthemajorityofsourcesrecommendawidthofatleast98feet(Appendix1).Theminimumbufferwidthforeffectivereductionofphosphorusis30feet.(FischerandFischenich2000),andthemajorityofsourcesrecommendawidthofatleast98feet.(Appendix1).ii. MediatingsedimentBufferscanhelptoreduceissuesassociatedwithsedimentsinthreeways:(1)preventingtheoccurrenceormediatingtheseverityofsediment-producingactivities,suchasconstructionoragricultureclosetothewetlandedge;(2)trappingterrestrialsedimentscarriedinrun-offbeforetheyenterthewetland;and(3)supportingin-streamconditionsthatincreasesedimentdepositionand/orreduceerosion,suchasreducingtheseverityofhighflow/velocityeventsfromstormflows,stabilizing

20

banks,andcontributingwoodydebris,whichtrapssedimentsinthewater(Mayeretal.2007,Liuetal.2008,Zhangetal.2010,KirwanandMegonigal2013).Sincenutrientsareoftenboundtosedimentparticles,thereductionofsedimenttransportmayalsoservetoreducenutrientexportfromriparianzones(HickeyandDoran2004).Forinstance,sedimentationmayaccountforphosphorusretentionratesofupto115lb/acre/year(Hoffmanetal.2009).Sedimentretentionisalsoanimportantfactorinmaintainingviableforagingandspawningsitesforfishandotheraquaticorganisms(Chaseetal.1995,HickeyandDoran2004).Theroleofbuffersinreducingsedimentinputscanbeprofound(Youngetal.1980,Dillahaetal.1988,Dillahaetal.1989,Magetteetal.1989).Forexample,experimentalresearchdemonstratedthata54-footbufferconsistingofswitchgrassandwoodyvegetation(shrubsandtrees)removed97percentofthesedimentfromanadjacentfield(Polyakovetal.2005).Similarly,researchersfoundthat~65percentofsedimentsweretrappedbya33-footstreamsideforestbufferand~85percentfora66-footbuffer(SweeneyandNewbold2014).Itisalsoworthnotingthatlandscapemodelsindicatedahighpercentage(47percent)ofthetotalvariationinsedimentloadingtostreamscouldbeexplainedbyriparianforestcover,highlightingtheimportanceofbuffersinmediatingsedimenttransfer(Jonesetal.2001).Whileonestudyfoundthatnarrowbuffers(16to66-foot)areabletoremovecoarsesediments,widerbuffers(66to328-foot)arebetterabletoremovefinersediments(Hruby2013).Theminimumbufferwidthforeffectivesedimentremovalis30feet(EnvironmentalLawInstitute2008),andthemajorityofsourcesrecommendawidthofatleast98feet(Appendix1).iii. Influencingwatertemperature

Infreshwatersystems,vegetatedbuffershelptoregulatestreamtemperaturesbyprovidingshade(Hruby2013).Thisisparticularlyimportantforcold-waterfish,asincreasesinwatertemperaturealsohavepotentiallyundesirableeffectsonstreamchemistry,aquaticinsects,streamflora,andfishbehavioranddevelopment(HaganandWhitman2000).Forexample,averagestreamtemperaturesincreasedby7.9°Faftertheremovalofriparianforest,andtherewasan18°Fincreaseinmaximumtemperaturebetweenaclear-cutstreamandabufferedstream(Risheletal.1982).Furthermore,streamswithvegetationremovedtendtoexperiencesummertemperatureincreasesof9°to19.8°Fabovestreamswherenaturalvegetationwasmaintained(Bentrup2008).Basedonthesefindings,bufferwidthsrangingfrom25to100feethavebeenproposedforadequatewatertemperaturemodification(Bartonetal.1985,Bentrup2008,OsborneandKovacic1993),witharecommendedminimumof30feetbasedonasynthesisofavailableliterature(Wenger1999).

iv. Providingorganicinputsintoaquaticsystems

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Bufferscontributeleaflitter,detritus,smallwoodydebris,andinsectstoadjacentaquaticecosystems.Theseimportantenergyinputsdriveaquaticecosystemfoodwebs(Naimanetal.2002,FisherandLikens1972,Golladayetal.1992,Wallaceetal.1997).Largercoarsewoodydebrisinputsintostreamsandriversareimportantforcreatingtherangeofdifferentenvironmentsrequiredbyorganismsforshelter,foraging,hibernation,andreproduction,includingpools,riffles,debrisjams,andrelatedstructuralaquatichabitat(Chaseetal.1995,FischerandFischenich2000).Theyalsohelptoretainsedimentsandnutrients,andinfluencechannelmorphology(Naimanetal.2002).ReidandHiltonexaminedhowwidebufferswouldneedtobetomaintaintree-fallratessimilartothoseinundisturbedforestandtoprovidecoarsewoodydebristotheriparianarea.Theyrecommendedabufferwidthof4to5treeheights,withatreeheightbeingdefinedastheaveragemaximumheightofthetallestdominanttrees(200yearsorolder)foragivensiteclass(ReidandHilton1998).Similarly,Bentrup(2008)recommendedabufferwidthfrom100to400feetforadequatewoodydebrisandlitterinput.Basedonasummaryoftheavailableliterature,Wenger(1999)recommendedaminimumbufferwidthof50feettoprovidesufficientwoodydebristostreams.II. HydrologicEffectsBuffersprovidearangeofhydrologicecosystemservicesthatmaybeparticularlyimportantgivenevidenceoftheincreasingfrequencyof“extreme”weatherevents.TotalannualprecipitationinthenortheastUnitedStateshasincreasedoverthepastcentury,withintensestormeventsoccurringwithmorefrequency(Smithetal.2008b).Asof2008,thecostofrepairingdamagesfromfloodingandfluvialerosionwas$6billionperyearintheUnitedStates;thishaslikelyincreasedsincethen(Smithetal.2008b).Vegetatedbuffersreducetheseverityoffloodeventsbyinterceptingoverlandflowfromprecipitationandmeltwaterandbyallowingforgreaterinfiltration.Themajorityofstudiesfocusinggenerallyonthehydrologicecosystemservicesprovidedbybuffershaverecommendedawidthof98feettomaintaintheseservices(Appendix2),withaminimumrecommendationof33feet(Wenger1999,FischerandFischenich2000).Specificdiscussionoftheroleofbuffersinfloodstorage,run-offreduction,andbankstabilizationisprovidedbelow.i. Providingfloodstoragecapacity

Bufferspromotefloodplainwaterstorageandminimizedownstreamfloodingpotentialinavarietyofways.Theyinterceptoverlandflowandincreasewaterretentiontime,whichresultinreducedfloodpeaks(FischerandFischenich2000).Theyalsoregulatestreamflowandfacilitateinfiltrationofsurfacewater,whichleadtolessseverewaterlevelfluctuationsduringstormevents(Bennett2010,Chaseetal.1995).Thisregulationofwaterlevelfluctuationisimportantsincesudden,highmagnitudefluctuationsoftendestroywetlandvegetation,particularlyalongthewetlandedge.Thislossofnativewetlandvegetationcanthenleadtoanincreasedabundanceofinvasiveplantspeciesandalterationofinvertebratecommunities(Castelleetal.1992).Theminimumbufferwidthrecommendedforeffectivefloodstoragewas66feet(FischerandFischenich2000),withrecommendationsofminimumwidthsup

22

to492feet(FischerandFischenich2000)or25feetbeyondtheextentofthe100-yearfloodplain(Bennett2010).ii. Reducingrun-offandstabilizingthechannelbankVegetationwithinbufferareasstabilizesriparianshorelinesthroughcomplexrootsystemsthatareoftenabletowithstandcyclicflooding,icescour,andnaturalerosion(Chaseetal.1995).Theroleofrootsystemsinstabilizingshorelinesdependsontheplanttaxa:herbaceousplantswithfibrousrootsystemsprotectbanksfromsurfaceerosion,andwoodyspecieswithdeeperrootsincreasesoilcohesionandreducemassslopefailure(Bentrup2008).Buffersalsoimpedetheflowofwaterrunoffbyallowingittopercolateintotheground,whichpreservessoilcompositioninperiodsofintenserainfall(Castelleetal.1992).Likewise,foliageandbranchesreducewindenergybyphysicallyinterruptingflowpaths(Bentrup2008).Infact,avegetativewindbreakprotectsadownwindareathatistento15timestheheightofthetrees–aservicethatreducessoilerosionandstabilizesthesoil(Bentrup2008).Theminimumbufferwidthreportedforeffectivebankstabilityandrun-offreductionwas164feet(EnvironmentalLawInstitute2008).iii. InfiltratingsurfacewaterInfiltrationisdefinedastheprocessbywhichsurfacewaterentersthesoil.Whilewewereunabletofindspecificbufferwidthrecommendationsforinfiltrationintheliterature,itisimportanttorecognizethebenefitthatbuffersprovidebyinfiltratingsurfacewater.Infiltrationallowspollutantsandsedimenttobeinterceptedandremovedfromthewatercolumnbeforereachingthewaterbody(SweeneyandNewbold2014).Infiltrationalsoreducestheseverityoffloodevents,asmentionedpreviously.Coarser-texturedsoils,suchassandysoils,typicallyhavehigherinfiltrationthanfiner-texturedsoils(Bentrup2008).III. HabitatforBiodiversityBuffersprovidevitalhabitatforadiversityofaquatic,semi-aquatic,andterrestrialfauna.Specifically,buffersserveasimportantsitesforforaging,hibernation,breeding,nesting,connectivityandescapefromflooding(Groffmanetal.1991,Naimanetal.1993).Buffersalsoprovidevisualseparationbetweenwetlandsanddevelopedenvironments,therebyreducingnoiseandlightpollutiontosensitivewildlife(Castelleetal.1992).Nearly80vertebrates(bird,mammal,reptileandamphibian)speciesinthenortheasternUShaveastrongpreferenceforriparianhabitats(DeGraafandYamasaki2000).Similarly,ofthe~450speciesofreptiles,amphibians,mammals,andbirdsthatoccurinNewHampshire,~90dependonwetlandsduringsomephaseoftheirbreedingcycle,and50moreusewetlandsforbreedingorforaginghabitat(Chaseetal.1995).Thisamountstoaboutone-thirdofNewHampshire’snativewildlifedependingonaquaticandwetlandhabitat.Therearealsoahostofrareplantsandnaturalcommunitiesassociatedwithriparianareas.

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Itisimportanttonotethatwhilemanyspeciespreferbufferscomparedtoterrestrialhabitatfartherfromthewetlandedge,thisdoesnotnecessarilymeanthatmaintainingbuffersaloneissufficienttoensuretheirneedsaremet.Aseminalmeta-analysisundertakenbyMarczaketal.(2010)assessedwhetherforestedriparianbuffersmaintainedriparianfaunaatdensitiesclosetothosefoundinunharvestedforest.Theyfoundthatwhetherforestedbuffersaloneweresufficienttomaintainlargelyunalteredpatternsofabundancedependedonthetaxa:Amphibianswerelessabundantinforestedbufferscomparedwithcontrolsitesinunharvestedforest.Smallmammalsdemonstratedamarginallydecreasedabundanceinbufferscomparedwithcontrolsites.Birdswereslightlymoreabundant,however,thespeciescompositionofavifaunaswitchedtomoreedge-associatedspecies.Arthropodsweretheonlytaxaassessedinwhichanincreaseinabundancewasfoundinbufferscomparedtocontrolsites.Furthermore,thereviewfoundnorelationshipbetweenbufferwidthandthemagnitudeofdifference(effectsize)betweenbuffersandcontrolsites.Thisreviewclearlydemonstratesthatthemaintenanceofbuffersaloneislikelytobeinsufficientifthemanagementgoalistoretainareasofnaturalhabitatwiththesamesuitabilityfoundinunalteredterrestriallandscapes.Whilebuffersdosupportahostofwildlifespecies,theydonotdosototheextentthatunalteredterrestriallandscapesdo.Whilethemeta-analysisundertakenbyMarczaketal.(2010)didnotfindasignificantrelationshipbetweenbufferwidthandthequalityofriparianhabitat,variationintheknownecologyofindividualspeciesandtaxaprovidescompellingevidencethatminimumbufferwidthswillvaryamongdifferentorganisms.Forexample,woodfrogs(Lithobatessylvaticus)rangeconsiderablyfartherfromthewetlandedgecomparedtospottedsalamanders(Ambystomamaculatum),thustheareaofbufferneededtoensuremostofthepopulationisdistributedwithinsuitableforestedhabitatvariesbetweenthetwospecies(Harperetal.2015).Sincethebufferwidthsrequiredforwildlifehabitataregenerallylargerthanthoserequiredforotherbufferfunctions,ensuringwildlifeprotectionwhendeterminingbufferwidthswillinturnprotecttheothervariousbufferfunctions.Generally,thewiderthebufferwidth,thegreaterthehabitatdiversity,whichcansupportagreaternumberofwildlifespecies(Chaseetal.1995).Themajorityofpublishedstudieshaverecommendedaminimumwidthof328feetforwildlifeingeneral,i.e.considerablywiderthanrecommendationsformostotherbufferfunctions(Appendix3).Discussionofspecificrecommendationsforindividualtaxaisprovidedbelow.i. AquaticmacroinvertebratesandfishAquaticmacroinvertebratesandfishareknowntobesensitivetochangesinhabitatstructureandfunction,hencetheircommonusageasindicesofbioticintegrity(LammertandAllan1999,Herlihyetal.2005).Bufferscanplayanimportantroleindeterminingthishabitatstructurebymaintaininginputsoforganicmaterialasabasisforaquaticfoodwebs,providingwoodydebrisandhencehabitatheterogeneityinthestream,maintainingwaterquality,reducinginputsofterrestrialsediments,andsupportinglowerwatertemperaturesandhigherconcentrationsofdissolvedoxygenthroughshading

24

(Jonesetal.2006).Themaintenanceofbuffersisclearlyofgreaterimportanceforthosespeciesandtaxathatareparticularlysensitivetoalterationofnaturalconditionsintheaquaticenvironment.Examplesoftheseincludecold-waterassociatedspeciessuchasbrooktrout(Salvelinusfontinalis)andothersalmonidswheresuitablespawninghabitatcanbedegradedbyincreasedsedimentationleadingtolowerreproductivesuccess(ScrivenerandBrownlee1989).Themajorityofpublishedstudieshaverecommendeda98-footbufferforadequatefishandaquaticmacroinvertebratehabitat(Appendix3),althoughrecommendationsofover300feethavebeensuggestedforthelattertaxa(EnvironmentalLawInstitute2003).ii. AmphibiansTerrestrialhabitatadjacenttowetlandsiswidelyrecognizedascriticalhabitatformanyamphibianspecies(Semlitsch1998).Juvenileandadultamphibianssuchasmolesalamanders(Ambystomasp.),woodfrogs(Lithobatessylvaticus),andAmericantoad(Anaxyrusamericanus)spendmuchoftheirtimeinuplandhabitat.Asthemajorityofanimalstendtoremainclosetosuitablewetlandbreedinghabitat(RittenhouseandSemlitsch2007)andmanyspeciesofamphibiansinthenortheasternUSareconsideredforest-associated(Gibbs1998),maintainingnaturallyvegetatedbuffersisconsideredcriticaltolocalpopulationpersistence(Harperetal.2008).Asamphibiansdifferinvagility,estimatesoftheextentofterrestrialbufferneededtoensurepopulationpersistencevaryamongspecies.Ameta-analysisundertakenbyHarperetal.(2008)estimatedthatbufferswouldneedtobe3,281feetwidetoencompass100percentofthewoodfrogsinapopulationand951feetwideforspottedsalamanders.ThereviewundertakenbyNHANRSreportedameanrecommendedminimumbufferwidthof256feet(Appendix3).Inadditiontoprovidingcriticalhabitatforlocalpopulationsofamphibians,wetlandbuffersmayalsohelptofosterconnectivitywithinmetapopulations(Baldwinetal.2006).Recentworkhashighlightedtheimportanceofthisinter-populationmovementinmaintainingthepersistenceofregionalpopulationsofamphibianspecies(Harperetal.2015).iii. Reptiles

Similarlytoamphibians,manyspeciesofreptilesarereliantonsuitableaquaticandterrestrialhabitatinordertocompletetheirlifehistorycycles(Bennett2010,SemlitschandBodie2003).Speciessuchascommonsnapping(Chelydraserpentina)andpainted(Chrysemyspicta)turtlesspendthemajorityoftheirtimeinwetlandsandrivers,emergingontolandtolayeggsortomoveinsearchofmoresuitablehabitat(Gibbsetal.2007).OtherspeciessuchasBlanding’s(Emydoideablandingii),wood(Glyptemysinsculpta),andspottedturtles(Clemmysguttata)roammorewidelyintheterrestrialenvironment,oftenaccessinganumberofdifferentwetlandsthroughouttheyear(Arvisaisetal.2004,Joyaletal.2001,RefsniderandLinck2012).Maintainingbuffersfortheseorganismsisparticularlyimportantastheirrelianceonwetlandsanduplandsmeansthatindividualsareoftenconcentratedimmediatelyadjacenttothewetlandedge.Ifhabitatalteration(particularlyroaddevelopment)occursalongthiswetlandinterface,significantmortalitycanoccur,leadingtoreducedabundancesandpopulation

25

viability(GibbsandShriver2002,Aresco2005).Forwide-rangingspecies,riparianbuffersmayalsoformimportantmovementcorridors,therebyincreasingtheprobabilityofpersistenceofbothlocalandregionalpopulations(Arvisaisetal.2002,ShoemakerandGibbs2013).Estimatesoftheminimumbufferwidthsneededtomaintainadequatereptilehabitatrangedconsiderablyfrom100feet(Bentrup2008)tomorethan3,000feet(Kiviat1997),withamedianminimumof417feet(Appendix3).iv. Birds

Manyspeciesofbirdsdemonstrateapreferenceforhabitatonthewetland/uplandinterfacefornesting,foraging,andmovementamongadjacentareas(Bennett2010,NaimanandDecamps1997).Infact,aviandensityandspeciesrichnessinriparianareashavebeenestimatedtobenearlydoubletheamountsinuplandareas(Medinaetal.2016).Maintainingbuffersinotherwisealteredlandscapescanconservethepreferredriparianhabitat(Machtansetal.2002),althoughtheextenttowhichtheneedsofbirdsaremetisdependentonboththecharacteristicsofthebuffer(habitattype,width,andlandscapecontext)andtherequirementsofindividualspecies(Saab1999,Shirley2004,Smithetal.2008a).Forexample,buffersareoftenoccupiedbymoreubiquitousedgespeciesratherthanthosetypicallyfoundintheforestinterior(WhitakerandMontevecchi1999,PearsonandManuwal2001,Marczaketal.2010),withbuffersofmorethan147feetneededtoconservethelattertaxa(PearsonandManuwal2001,ShirleyandSmith2005,Shirley2006).Givenvariationintheneedsandsensitivityofdifferentbirdtaxatohabitatalteration,recommendedminimumbufferwidthsalsovary:themeanminimumbufferwidthforadequatewaterfowlhabitatwas108feet(Appendix3),whereastheminimumwidthforadequatepasserinebirdhabitatwas200feet(Boyd2001;Bentrup2008),andthemajorityofsourceshaverecommendedaminimumwidthof328feetforadequatebirdhabitatoverall(Appendix3).v. MammalsMammalsinNewHampshirevaryintheirpreferenceforbufferhabitat.Speciessuchasriverotter(Lutracanadensis),mink(Neovisonvison),beaver(Castorcanadensis),andAmericanwatershrew(Sorexpalustris)arewetlandobligatesthatusebuffersascriticalhabitatforfeeding,cover,denning,andtravelways.Speciessuchasmoose(Alcesalces)arealsocloselyassociatedwithwetlandsandthewetland/uplandinterfaceduringsummermonthswhentheyusetheseareasforbrowsing,escapefrominsectsandpredation,andthermoregulation(Koitzsch2002).Similarly,southernboglemming(Synaptomyscooperi)andsnowshoehare(Lepusamericanus)areoftenfoundathigherabundancesinuplandhabitatadjacenttowetlands,likelyasaresultoftheavailabilityofbrowseandescapecover(D.Patrick,unpub.data).Inadditiontotheneedtoconservebufferhabitatformammalianspeciesreliantuponthisresource,maintainingbuffersinotherwisealteredlandscapescanalsosupportthecontinuedpersistenceofspeciesdistributedmorewidelyacrossuplandhabitat(CockleandRIchardson2003,Marczaketal.2010).Forexample,researchinagriculturallandscapesinsouthernQuebecreported14speciesofsmall

26

mammalsinremnantriparianbufferstrips(MaisonneuveandRioux2001).Thevalueofbuffersinalteredlandscapesformaintainingregionalconnectivityhasbeenatopicofconsiderabledebate,howeverthereiscompellingevidencetoindicatethatretainingorrestoringconnectivityamongotherwiseisolatedpatchesofsuitablehabitatislikelytoincreasethelikelihoodofpopulationpersistence(BeierandNoss2008).Despitethelikelyimportanceofbuffersformammalianspecies,relativelylittleresearchhasfocusedexplicitlyondeterminingminimumbufferwidths(Wenger1999).Similarlytoothertaxa,thisminimumisheavilyinfluencedbytheneedsofthespecies,habitatstructurewithinthebuffer,andthesurroundinglandscapecontext.Bearingthisinmind,aminimumrecommendedbufferwidthforadequatemammalhabitatof100feethasbeenproposed(Bentrup2008)withthemeanminimumbufferwidthrecommendedof245feetinthepublishedliterature(Appendix3).

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Table2.Benefitsconveyedbybuffers.

BufferFunction

Benefit AttributesofBuffer

Reducinginputsofexcessnutrientsandcontaminants

Highlydependentonsoiltype,vegetationtype,topography,hydrology

WaterQuality

Mediatingsediment Assumesvegetatedbuffer

Influencingwatertemperature

Assumesbufferwithtallvegetationadjacent/overwaterbody,typicallyforested

Providingorganicinputsintoaquaticsystems

Assumesvegetatedbuffer

Providingfloodstoragecapacity

Assumesvegetatedbuffer

HydrologicEffects

Reducingrun-offandstabilizingthechannelbank

Typicallyassumesforestedbuffer

Infiltratingsurfacewater --

Aquaticmacroinvertebratesandfish

Bufferhabitatmustmeetspecies’needs

Amphibians

HabitatforBiodiversity Reptiles

Birds

Mammals

28

Table3.Summaryofminimumrecommendedbufferwidthsbyoverallbufferfunctionfromtheliterature.

BufferFunction MinimumWidthRecommendedbyStudyAuthors

MedianWidthRecommendedbyStudyAuthors

MaximumWidthRecommendedbyStudyAuthors

WaterQuality 16feet 100feet 400feet

HydrologicEffects 33feet 98feet 330feet

HabitatforBiodiversity 50feet 328feet 1,969feet

Table4.Summaryofminimumrecommendedbufferwidthsbyecosystemserviceprovidedbyeachbufferfunctionfromtheliterature.

BufferFunction Benefit RecommendedBufferWidth

Reducinginputsofexcessnutrientsandcontaminants 98feet

WaterQuality Mediatingsediment 98feet

Influencingwatertemperature 30feet

Providingorganicinputsintoaquaticsystems 50feet

Providingfloodstoragecapacity 66feet

HydrologicEffects Reducingrun-offandstabilizingthechannelbank 164feet

Infiltratingsurfacewater Nonefound

Aquaticmacroinvertebratesandfish 98feet

Amphibians 256feet

HabitatforBiodiversity Reptiles 417feet

Birds 328feet

Mammals 245feet

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E. WHATPREVIOUSANDONGOINGATTEMPTSHAVEBEENMADETOADDRESSECOLOGICAL

STRESSORSANDMAINTAINECOSYSTEMSERVICESUSINGBUFFERS,ANDWHATTECHNICALBARRIERS

HAVEBEENENCOUNTERED?

Giventhelikelyefficacyofbuffersinreducingecologicalstressorsandmaintainingecosystemservices,itisnotsurprisingthatanumberofwatershedsintheUnitedStateshaveattemptedwidespreadimplementationofbufferconservationandrestoration.Whiletheintensityoftheseeffortsandthecontextwithinwhichtheyhaveoccurredvariesconsiderably,importantlessonscanbelearnedfromreviewingthefollowingcasestudies.Thesehavebeenchosenbasedontheirdescriptionoftheimplementationstrategy(quantificationofapproachesormethodsused),relevanceofwatershedscale(similartothescaleatGreatBay),inclusionofaquantificationofoutcomes(tangibleresultsforlessonslearnedfromtheimplementation),andsimilarecological/social/cultural/regulatorycontexttotheGreatBaywatershed.Primarily,thesestudieswereconductedinNorthAmerica.Presentationofthesecasestudiesisorganizedbyrelevant“frequentlyaskedquestions.”I. Whatsuccesseshavearisenfrombufferrestorationandprotectionattempts?Thefollowingcasestudiesrepresentexamplesofbufferrestorationsthathavebeen“successfully”employed,i.e.,naturalvegetationhasbeenre-established.Whereinformationisavailable,wehavealsodiscussedtheevidencethattheserestorationeffortshaveresultedinquantifiablebenefitstotargetecosystemservices.Alsoincludedarecasestudieshighlightingsuccessfulprotectioneffortsthathavemaintainedfunctionalbuffersinplaceswheretheystilloccur.Comparedtorestoration,fewercasestudieshavequantifiedtheecosystemservicebenefitsofprotectionofexistingbuffers.Morespecifically,wewereunabletofindwatershed-scalecasestudiesthathadcomparedthebenefitsofusingavailableresourcestoconserveexistingbuffersversusrestoringlostbuffers.Weflagthisasaresearchgapgiventhatrestorationisoftencostlyandnotalwayssuccessful.i. NorthHampton,NewHampshire

VariouswaterqualityandhabitatimprovementprojectsthroughouttheNortheasthavespecificallyimplementedbufferrestorationandprotectionastheirkeystosuccessinmeetingtheirobjectives.Asalocalexample,riparianbuffershavebeenrestoredattheSagamore-HamptonGolfCourseinNorthHampton,NewHampshirethroughtheNewHampshireSeaGrant’sCoastalResearchVolunteersprogram(Fig.5).Morethan100treesandshrubswereplantedinearlysummer2016,includingriverbirch(Betulanigra),sweetpepperbush(Clethraalnifolia),andfragrantsumac(Rhusaromatic,Gro-locultivar).AsofAugust2016,survivalwas100percent,despitethedrought(A.Eberhardt,pers.comm.).

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Figure5.Pre-andpost-restorationphotosofariparianbufferareainNorthHampton,NewHampshire.PhotosprovidedbyNewHampshireSeaGrant.ii. ConnecticutRiverWatershed

FloodplainrestorationalongtheConnecticutRiverisanotherexampleofaprojectthathassuccessfullyimplementedbufferrestorationandprotectionintheNortheast.Since2009,TheNatureConservancyandpartnershavespearheadedanefforttoprotectandrestorefloodplainforestwithintheConnecticutRiverwatershed.Thisinitiativebeganwithprioritizationoftractsforprotectionandrestorationbasedoncriteriaincludingtheexistenceoflow,regularlyfloodedterracesandextensiveshoreline,thepotentialofthetracttoserveasalinkagetoprotectedareasacrosstheriver,andlocationofthetractinanactiveriverareaoftheConnecticut.Withinthesepriorityareas,theConservancyanditspartnershaveimplementedanadaptivemanagementapproachtorestorationthatwillhelpdeterminethemostcosteffectiveapproachtobringbacksilvermaple(Acersaccharinum),Americanelm(Ulmusamericana),andothernativefloodplainspeciesonfloodplainterracesthathaveahydrologicregimetosupportthishabitatintothefuture.Theseeffortshaveledtoanincreasedunderstandingofthemostappropriatemanagementtechniquesforsuccessfulrestoration(Marks2013),aswellasforestedriparianbufferrestorationonanumberofproperties,includingthe252-acrePotterFarmtractinNewHampshire.iii. ChesapeakeBayWatershed

Athirdexampleofasuccessful,targetedbufferrestorationprojectiswithintheChesapeakeBaywatershed.Forestedbuffershavebeenplantedwithinthewatershedsince1996,coveringmorethan8,152miles(ChesapeakeBayProgram2013).Theinitiativehasbeenundertakenthroughtheimplementationofriparianforestbufferincentiveprograms,mostnotablytheConservationReserveEnhancementProgram(CREP).Inthemostproductiveyears,thebaystatesaveraged830milesofbuffersalongsideriparianareasrestoredperyear.Properuseoftreetubingandherbicideapplicationwerefoundtogreatlyimproverestorationsuccess(ChesapeakeBayProgram2013).

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iv. ColumbiaRiverWatershedInotherareasoftheUnitedStates,bufferrestorationprojectshavehadsuccessintargetingareasimpactedbyforestryandagriculture.IntheColumbiaRiverwatershedinthewesternUnitedStates,sincethe1960’sbufferareashavebeenaddedtoreducetheimpactsoflogging–inparticular,slopefailureandsoilerosion(NationalResearchCouncil2004).Additionally,WashingtonState’sConservationReserveEnhancementProgram(CREP)hasprovidedfinancialincentivesforfarmerstorestoreriparianbuffersonagriculturallandfornearly20years.Survivalofplantedvegetationrangedfrom75percentto90percentthroughoutthestate,withmostpositiveresultsseenafter5+yearsofthebufferbeingimplemented,especiallyforcanopycover,whichprovidestheserviceofshadingthebufferandadjacentwaterbody(Smith2012).v. FoxCreekCanyon,OregonInOregonin2003,theFoxCreekCanyonunderwentarestorationprojectcoordinatedbyvariouspartneringagenciestomitigatethedegradationcausedbyopen-rangecattlegrazing.Sixteenacreswereseededwithnativegrasses,4,000nativecuttingsandseedlingswereplanted,and7milesoffencewereinstalledtoexcludecattle(Machtinger2007).Resultswerenotquantified,butgrassesandforbshadregeneratedonthebanksofFoxCreekwithintwoyearsoftherestorationefforts.vi. BogBrook,NewHampshireVariousotherprojectsintheNortheastandwesternUnitedStatesthatincludedbufferrestorationasacomponentoftheirwaterqualityandhabitatimprovementtechniquesdemonstratedsuccesses,althoughthedegreetowhichbufferrestorationcontributedtothesuccessesremainsindeterminable.AbufferwasimplementedaspartofastreambankstabilizationprojectatBogBrookintheupperConnecticutRiverbasinofnorthernNewHampshire,anareadominatedbyagriculture.Riparianvegetationwasremoveddecadesago,presumablytoincreasethearablelandareaavailable,whichcausedstreambankerosionandasubsequentdeclineinwaterquality(U.S.EnvironmentalProtectionAgency2006).In2004,thestreambankwasstabilizedthroughnaturalstreamchanneldesign,includingplantingofdeep-rootedshrubstoformavegetatedbuffertosupplementtheshallow-rooted(six-inch)grassesinexistence.Theshrubsconsistedofalderandwillow,amongothers.One-yearpost-construction,thevegetationwaswell-establishedandfirmlyrooted,andthechannelhadbecomemorenarrowanddeeper,bothindicativeofchannelstability.Becauseofthisrestoration,BogBrookwasreclassifiedas“FullySupporting”from“Impaired”bytheNewHampshireDepartmentofEnvironmentalServices.vii. MousamLake,MaineAnotherprojectthatincludedbufferimplementationtoaddresswaterqualityissueswastherestorationofMousamLake’sshorelineinsouthernMaine.Thelake’swaterqualityhadbeenindeclinefordecades

32

duetoexcessivephosphorusinputsviastormwaterrunoff.However,aftertenyearsofnonpointsourcepollutioncontrolprojectsthatstartedin1997,waterclarityincreasedbythreefeet,thelakewasinastableorimprovingtrophicstate,anditattainedwaterqualitystandardssetbytheMaineDepartmentofEnvironmentalProtection,therebyallowingittoberemovedfromthelistofimpairedwaterbodies(U.S.EnvironmentalProtectionAgency2008).Bestmanagementpractices,includingvegetatedbufferplantings,wereinstalledalongthelakeshorelineat45prioritysitestostabilizeerosionandimproveroadsidedrainageandgravelroadsurfaces.Theassociatedreductioninpollutantloadingtothelakewasmorethan150tonsofsedimentand130poundsofphosphorusperyear–thisequatestoatenpercentreductioninphosphorustothelake.Consequently,thishighprofileworkinspiredprotectioneffortsonseveralneighboringlakes.viii. HighlandLake,MaineSimilarly,bufferrestorationwasonemethodusedtocombatwaterqualitydeclinesinHighlandLakeoutsideofPortland,Maine.Inthe1980’sand1990’s,thelakeshowedsignsofdecliningwaterqualitycausedbyexcessivesoilerosionthroughoutthewatershed.Restorationworkbeginningin1997addressedsignificanterosionsitesandreducedpollutedrunoffbyplantingmorethan1,000shrubs,trees,andgroundcovers,andinstallingotherbestmanagementpracticessuchaswaterbars,raingardens,andriprap.Lakewaterclaritystabilizedandmetwaterqualitystandards,therebyallowingittoberemovedfromthestate’slistofimpairedwaterbodiesin2010.Furthermore,theamountofsedimentandphosphorusexportedtothelakedeclinedsignificantly;itwasestimatedthatpollutantloadingwasreducedby278tonsofsedimentand1,070poundsofphosphorusperyear(U.S.EnvironmentalProtectionAgency2010).ix. GilaRiverWatershedAlthoughnottopographicallysimilartotheNortheast,theGilaRiverwatershedprovidesanotherexampleofbufferrestorationandprotectionbeingusedtoreviveanimpairedwatershedsuccessfully.PortionsofthewatershedwithinArizonaandNewMexicohavebeendegradedbypastfiremanagement,logging,anddomesticgrazingpractices,therebyreducingwaterquality,speciesdiversity,andfloodplainfunction(NaturalResourcesConservationService2006).Protectionandrestorationeffortsbeganinthelate1970’sandincludedprescribedfire,improvedlivestockandoff-roadvehiclemanagement,andtheuseofbioengineeringtechniques.Protectionandrestorationoftheriparianareaappearssuccessful,asanewrarespeciesofstoneflywasobservedduringbioticconditionindexmonitoring,breedingnumbersofthesouthwesternwillowflycatcherincreased,andsedimentsandashwereobservedtobetrappedonsiteratherthanlostdownstream.

33

II. Whatobstacleshavebeenencounteredinbufferrestorationandprotectionattempts?Whilenumerousbufferrestorationandprotectionprojectshavebeensuccessful,othershavefacedchallengesintheirimplementationstrategies.Thefollowingcasestudiesserveasexamplesofeffortsthatinvolvedroadblocks,bothon-the-groundandconceptually.Wealsohighlightcertainobstaclesfacedbyalandtrustinitsattempttoprotectbuffersthroughregulatoryframework.i. ChesapeakeBayWatershedTheChesapeakeBaywatershed’sbufferrestorationinitiativehassufferedvarioussetbacksinitswatershed-scaleattempttoimprovethebay’swaterquality.Basedonthenumberofmilesplanted,restorationeffortshavedecreasednotablysince2009,likelyasaresultofdeclininginterest,lackofnoticeableeffectonwaterqualityandhabitatimprovement,scarcityoffunding,andincreasedchallenge(i.e.mostaccessibleoreasiestareashavealreadybeenplanted).Thisisdespitethefactthatforestbuffersareoneofthemostcost-effectivemethodsofimprovingwaterqualityinthebay.Earlyplantingssufferedfromlackofpropersitepreparationandmaintenance(e.g.competingvegetation,lawnmowing,deerbrowse),whichcausedplantingfailureanddiscouragedstakeholdersgoingforward.AnotherobstaclewasthattheCREPprogramhasnotbeenopenforenrollmentforvariousperiodsthroughouttherestorationeffort,andtheseinterruptionsinprogramdeliveryincreasedskepticismaboutprogramviability.Furthermore,asenrollmentsintheCREPprogramexpire,itmaytakeuptothreeyearstosecurere-enrollment;theamountofeffortandfinancialinvestmentputintoinitiallysecuringthesecontractscouldeasilybecanceledoutbylandownersnotre-enrolling(ChesapeakeBayProgram2013).ii. ConnecticutRiverWatershedSimilarly,theConnecticutRiverfloodplainrestorationprojectinNewHampshirehaselucidatedsomepolicy-basedtensionsandon-the-groundhurdles.Whileanumberofbufferprotectionandrestorationprojectsareunderway,thepathtoreachingascaleatwhichtheseeffortstranslateintolarge-scalerestorationoffloodplainforestwithinthewatershedisnotyetclear.Oneparticularchallengecomesfromthefactthatproductiveagriculturallandstendtobeconcentratedinfloodplainlands,particularlyinNewHampshire,whereonlysevenpercentofthestateisconsideredtobewell-suitedforagriculture.Thusthereisatensionbetweenrestoringbuffersandmaintainingactivefarming.Furthermore,competitioncausedbyinvasiveplantspeciessuchasorientalbittersweet(Celastrusorbiculatus)canleadtohighmortalityofplantedseedlings,particularlyinthelowerportionofthewatershed.iii. Maidstone,VermontAsanexampleofaspecificprojectintheConnecticutRiverfloodplainthathasfacedhurdleson-the-ground,bufferrestorationconductedononeofTheNatureConservancy’spreservesinMaidstone,

34

Vermontfacedvariouschallengespost-restoration(Fig.6).TheConservancypartneredwiththelocalNaturalResourcesConservationDistricttoinstalla100-footbufferalongthreesectionsoferodingriverbankindifferentyears,butthebankshavecontinuedtoerodeandhavecutintotherestoredareas.Additionally,plantingshavestruggledtosurviveduetograsscompetition,lackofwateruponinstallation,anddeerherbivory.Whereverpossible,thepartnershavesinceattemptedtoplantfurtherbackfromthebankandtoplantwidthsgreaterthan100feettoallowforsomebankerosioninthisnaturallymeanderingsectionofriver.Oneyearafterplanting,meshtubingwasinstalledtoprotectagainstdeerherbivory.TheNatureConservancyemploysanadaptivemanagementapproachforallbufferrestorationprojectsintheConnecticutRiverwatershed,therebyallowingflexibilityinpost-restorationmanagementapproachesdependingontheoutcomesobservedfollowingtherestorationwork.Throughtheadaptivemanagementstrategy,thelessonslearnedfromrestorationchallengescanbeemployedinsubsequentrestorations,therebyfacilitatingmoreeffectiveapproachesinthefuture.

Figure6.Before(left)andafter(center,right)photosofbufferrestorationfromTheNatureConservancy’sMaidstoneBendsPreservealongtheConnecticutRiverinMaidstone,VT.PhotosprovidedbyTheNatureConservancyinVermont.AreviewofsixnationalcasestudiesfocusedonriparianbufferprojectshighlightedthetopchallengesthattheprojectsfacedthroughouttheUnitedStates.Thegreatestobstacleidentifiedwassecuringfunding(Frey2013).Invasivespeciesandsurvivalofplantedtreesalsorankedhighlyascommonissuesencountered.Anotherstumblingblockwasthedifficultyofworkingwithprivatelandowners,whichencompassedcoordinationofmultiplesites,willingnessofpropertyownerstoconsiderbufferimplementation,andconcernabout“givingup”landtobuffers.Otherissuesthataroseduringimplementationprojectsincludedweathereventsthataffectedthesurvivalofplantings(e.g.severewindstorms,landslides)(Bissonetal.2013)andlackoflong-termmonitoringforplantingstodeterminepersistenceofefficacy(Smith2012).Lastly,therearevariousobstaclestoenactingregulatorybufferprotections,whichthePennsylvaniaLandTrustAssociation(2014)outlined.Forinstance,landownersandothercommunitymembersmaynotappreciatethevalueofbuffersortheareasthattheyprotect.Peoplewhohaveafinancialinterestindevelopmentorthosewhoareideologicallyopposedtodevelopmentrestrictionsmaypushback

35

againstproposedregulatoryprotections.Likewise,somemaywanttoexemptcertainagriculturalorforestrypracticesfromrestriction.Lastly,findingagreementonanadequatebufferwidththatisbothecologicallysoundandpoliticallyacceptablemaybedifficult(PennsylvaniaLandTrustAssociation2014).III. Whataretheoverarchinglessonslearnedfrombufferrestorationandprotection

attempts?

Anumberofoverarchinglessonscanbedrawnfromourcasestudyreview.Whileappropriatemethodsforsuccessfullyrestoringbuffersarenowwell-understood,factorssuchasinvasivespeciesandbrowsingherbivorescanstillleadtochallenges.Additionally,therehasbeensuccessinrestoringbuffersatscaleinsomeplaces,butinotherareas,thepathtolarge-scalerestorationisnotclear,andmaintainingtheenergyrequiredtopropelrestorationeffortsovertimeisdifficult.Furthermore,thereissomeconcernthatrestorationmaytakeprecedenceoverconservationofbuffers.Thismaybetrue,giventhatnaturalbuffershavealreadylargelybeenlostthroughouttheNortheast,butitisimportanttorecognizethevalueofproactivelymaintainingwhatwealreadyhave,ratherthanreactingtorestorewhathasbeenlost.Programsthathaveimplementedrestorationprojectsalsoprovideimportant“lessonslearned”forfutureefforts.Onemajorthemeistheneedtosecureadequatefunding,includingresourcestosupportlandowneroutreachandmaintenanceofestablishedbuffersbyencouragingenrollmentaswellasre-enrollmentinrestorationprograms(ChesapeakeBayProgram2015).ConservationReserveEnhancementProgram(CREP)andEnvironmentalQualityImprovementProgram(EQIP)fundingshouldbeutilizedtotheirfullestextents–thereisnoestablishedfundinglimitforCREP,andmoststatesarewellundertheirCREPacreagecaps(ChesapeakeBayProgram2013).Anotherimportantlessonregardingbufferrestorationistheneedtoemployanadaptivemanagementapproach.Usingthisapproach,eachrestorationisconsideredanexperiment,andmonitoringisconductedpost-restorationtodeterminehowandwherecertainrestorationapproachesareeffective.Thismonitoringisvital,giventhattherewillinherentlybespatialandtemporalvariabilityamongeachrestorationprojectthatmayaffectitsoutcomerelativetootherprojects.Employingadaptivemanagementenablesmanagerstoimplementimprovedandtailoredrestorationmethodsgoingforward.Afurtherlessonlearnedforbufferprotectionandrestorationwastheimportanceofsufficientpreparatoryworkandconservationplanning.Forexample,programscouldconductlocalizedgeographicanalysestostrategicallytargetspecificlocationswherebufferswouldbemostbeneficialinnutrientloadreduction,asthisisacost-effectiveapproachthataccountsforthefactthatwaterqualitycontributionsvaryatalocalscaledependingonadjacentlanduseandotherfactors(e.g.theamountanddirectionofsubsurfaceflows)(ChesapeakeBayProgram2013).Datasetsarebeingdevelopedthatillustrateconcentratedflowpathsoverhigh-resolutionlandusedatatoprioritizeareasfortargetedrestoration

36

wherepollutantandnutrientrunoffhasthegreatesteffectonthewaterbody(AllenbyandPhelan2013),andtoprioritizeareasfortargetedprotectionwheretherearehigh-functioningnaturallandscapes(AllenbyandBurke2012).Asanadditionalplanningtool,itisimportanttorecognizethatplantedbuffersmaystillbesusceptibletoerosion,especiallyonsteepslopes;engineeredstructurespreparedfromlargewoodydebrisorgeotextilematsandrollscaneffectivelysupportplantedvegetation(Medinaetal.2016).Furthermore,post-restorationmonitoringandadaptivemanagementshouldbeimplementedtoassesssuccessandcontrolforinvasives(Medinaetal.2016).Additionally,programscouldconsiderbufferprotectioninadditiontorestoration.Protectionisconsideredbysomeorganizationsaneasier,moresuccessful,andcost-effectivemethod.Tocapitalizeonpreviousrestorationefforts,bufferprotectioncouldbetargetedtoareaswhererestorationhasbeenundertakenthroughpublicfunding.Lastly,atargetedconservationframeworkshouldbeimplementedinstateandlocallawsandordinancestoemphasizetheprotectionofbuffers(ChesapeakeBayProgram2013).Thecasestudieshighlightedinthisreviewdemonstratethattheremaybedifferencesinbufferefficacyandfunctioninenvironmentalsettingsascomparedtotheexperimentalsettingsfromwhichmuchofthereview’swidthrecommendationsaresourced.Ingeneral,thesecasestudiesraiseanimportantcautionarynotethatbuffersdonotrepresentapanaceaintermsofmitigatingenvironmentalstressorsandprovidingcriticalecosystemservices.Itisalsoclearthatquantitativelylinkingthemaintenanceorrestorationofbufferstokeyservicessuchaswaterqualityoutsideofanexperimentalarenacanbedifficult.Thelatterissueisnotsurprisinggiventhatwell-designedstudiesinvariablyinvolvecontrollingfactorsotherthanthoseofinterest,whereasreal-worldapplicationofbuffersoccurswithinahighlystochastic,multi-variate,andoftenun-replicatedenvironment(i.e.“therealworld”).Thechallengeinlinkingtheuseofbufferstoclearenvironmentalbenefitsinreal-worldapplicationsisimportanttorecognize,particularlywhencommunicatingwithrelevantstakeholders.However,itisalsovitalthatwehighlighttheimportantevidencedrawnfromcontrolledstudiesinwhichspecificcause-and-effectmechanismslinkingbufferstotheservicestheyprovidehavebeentestedandvalidated.

37

Appendix1.

Literaturereviewsummarytableofbufferwidthsforwaterquality.ReproducedwithpermissionfromRickVandePoll,Chair,NHANRSWetlandBufferScientificWorkGroup.Colorcodingcorrespondsasfollows:lightgray–wetlands,lightblue–streams,darkgray–vernalpools,yellow–pondslessthan10acres,darkblue–pondsgreaterthan10acres.

CITATIONTYPE AREAOFCONCERNRELATIVETOWETLAND/RIPARIANZONEFUNCTIONINTEGRITYBufferResearchCompendia GENERAL Sediment TDS/TSS Nitrogen Phosphorus Organics

(e.g.bacteria)

Sweeney&Newbold(2014) ≥98ft.

Chase,Deming&Latawiec(1995) ≥100ft.

Sheldonetal.(2005) ≥197ft. 66–328ft. ≥66ft.

Grangeretal.(2005) 40-75ft.

Wenger(1999)1 ≥98ft. ≥98ft. ≥98ft.

Nieber(2011) ≥100ft. ≥100ft. ≥100ft.

StraughanEnvironmentalServices,Inc.(2003)2

82-98ft.

Sweeney&Newbold(2014) ≥98ft.3 ≥131ft4

BMPGuides EnvironmentalLawInstitute(2003) ≥82ft. ≥82ft. ≥82ft. ≥82ft.

EnvironmentalLawInstitute(2008)5 30-100ft. 100-165ft.

30-100ft. 30-100ft.

Fischer&Fischenich(2000) 16-98ft.

deMaynadieretal.(2007) 50-330ft. Calhoun&Klemens(2002) ≥100ft.

deMaynadieretal.(2007) 50-400ft.

Wenger(1999)1 ≥98ft. ≥98ft. ≥98ft. Fischer&Fischenich(2000) 16-98ft.

GoodForestryintheGraniteState(2010)3 ≥100ft.

deMaynadieretal.(2007) 50-250ft. deMaynadieretal.(2007) 75-125ft. GoodForestryintheGraniteState(2010)3 100ft. deMaynadieretal.(2007) 100-330ft. GoodForestryintheGraniteState(2010)3 300ft.

JournalArticles/TechnicalReports Murphy&Golet(1998) ≥100ft.

Schwerr&Clausen(1989)6 ≥98ft. ≥98ft. ≥115ft. ≥115ft.

Murphy&Golet(1998) ≥100ft.

Murphy&Golet(1998) ≥150ft.

Ahola(1990) ≥160ft.

Correll&Weller(1989) ≥60ft.

38

Peterjohn&Correll(1984) ≥60ft.

RhodeIslandRiversCouncil(2005) ≥300ft.

AdditionalInformation

1Wengeralsosuggestsadding2ft.forevery1%ofslope2Basedon21papersrelatedtowaterqualityconcerns;alsorecommended3-zonesystem:Zone1:15ft.(natural);Zone2:60ft.(managed);Zone3:20ft.(grazed)3EachrecommendedRMZsuggestsaminimum'no-cut'zone:ponds:0ft.;greatponds:25ft.;4thorder+:25ft.;3rdorder:50ft.;1st&2ndorder:25ft.4Medianremovalratewas65%for33ft.bufferand85%for98ft.bufferfor28studiesofbothgrassandforestbuffersites5McElfish,Kihlsinger,&Nicholsaretheprincipalauthors6Forremovalof>90%ofthepollutant

39

Appendix2.

Literaturereviewsummarytableofbufferwidthsforhydrologiceffects.ReproducedwithpermissionfromRickVandePoll,Chair,NHANRSWetlandBufferScientificWorkGroup.Colorcodingcorrespondsasfollows:lightgray–wetlands,lightblue–streams,darkgray–vernalpools,yellow–pondslessthan10acres,darkblue–pondsgreaterthan10acres.

CITATIONTYPE AREAOFCONCERNRELATIVETOWETLAND/RIPARIANZONEFUNCTIONINTEGRITY

BufferResearchCompendiaGENERAL

Run-Off/BankStability FloodStorage

Grangeretal.(2005) 50-110ft. Wenger(1999)1 33-98ft. StraughanEnvironmentalServices,Inc.(2003)2 82-98ft. Sweeney&Newbold(2014) ≥82ft3 Murphy(N.D.) 100ft. VermontAgencyofNaturalResources(2005) 37-225ft. Bolton&Shellberg(2001)4 100-yrfloodplain

BMPGuides EnvironmentalLawInstitute(2003) ≥98ft. ≥164ft. deMaynadieretal.(2007) 50-330ft. Calhoun&Klemens(2002) ≥100ft. Wenger(1999)1 33-98ft. Fischer&Fischenich(2000) 33-66ft. 66-492ft.GoodForestryintheGraniteState(2010)5 100ft.

100-yrflood-plain+25ft.

deMaynadieretal.(2007) 50-250ft. deMaynadieretal.(2007) 75-125ft. GoodForestryintheGraniteState(2010)5 100ft. deMaynadieretal.(2007) 100-330ft. GoodForestryintheGraniteState(2010)5 300ft. JournalArticles/TechnicalReports

Murphy&Golet(1998) ≥100ft. Murphy&Golet(1998) ≥150ft. RhodeIslandRiversCouncil(2005) ≥300ft.

AdditionalInformation1Wengeralsosuggestsadding2ft.forevery1%ofslope2Basedon21papersrelatedtowaterqualityconcerns;alsorecommended3-zonesystem:Zone1:15ft.(natural);Zone2:60ft.(managed);Zone3:20ft.(grazed)

40

3Basedon38studiesinavarietyoflocalesandwithvariablecovertypes;medianremovalrateforthisdistancewas89%

4Applicablefor55%ofspecies;5spp.<100ft.;3spp.100-200ft.;9spp.>200ft.5EachrecommendedRMZsuggestsaminimum'no-cut'zone:ponds:0ft.;greatponds:25ft.;4thorder+:25ft.;3rdorder:50ft.;1st&2ndorder:25ft.

41

Appendix3.

Literaturereviewsummarytableofbufferwidthsforhabitatforbiodiversity.ReproducedwithpermissionfromRickVandePoll,Chair,NHANRSWetlandBufferScientificWorkGroup.Colorcodingcorrespondsasfollows:lightgray–wetlands,lightblue–streams,darkgray–vernalpools.

CITATIONTYPE AREAOFCONCERNRELATIVETOWETLAND/RIPARIANZONEFUNCTIONINTEGRITY

BufferResearchCompendia

GENERAL

AquaticMacro-

Invertebrate Amphibian Reptile Fish WaterfowlPasserine

Bird MammalChase,Deming&Latawiec(1995)

100-300ft.

Boyd(2001)1 ≥200ft2 ≥200ft3 ≥200ft4 <200ft4 ≥200ft5Desbonnetetal.(1994) 246-1,969

ft. Sheldonetal.(2005)

384-673

ft. ≥328ft. ≥328ft.Grangeretal.(2005)

≥100ft.390-1900

ft.440–

3,700ft. ≥100ft. 390–

2,000ft.250-650ft.

Wenger(1999)6 ≥328ft. Nieber(2011) 500-950

ft. Sweeney&Newbold(2014) ≥98ft.7 ≥98ft. Murphy(N.D.) 100ft. 100ft. VermontAgencyofNaturalResources(2005) 10-840ft. Lichtin(2008) 50-200ft. Bolton&Shellberg(2001)4

150-250ft.

BMPGuides Bentrup(2008)

100-200ft.100-600

ft.100-600ft.

100-330ft.

200ft.-5,280ft.

100-330ft.

EnvironmentalLawInstitute(2003) ≥328ft. ≥328ft. EnvironmentalLawInstitute(2008)8

100-950ft.

Calhoun&Klemens(2002)

100-750ft.

Bentrup(2008) 100-200ft.

100-600ft.

100-600ft.

U.S.ArmyCorpsofEngineers(2015)

100-750ft.

Wenger(1999)6 ≥328ft. Fischer&Fischenich(2000)

98-1,640ft.

GoodForestryintheGraniteState(2010)9 ≥300ft. ≥150ft.

42

JournalArticles/TechnicalReports

Groffmanetal.(1991) ≥328ft. ≥328ft. Kiviat(1997)

3,281ft10

Semlitsch&Bodie(2003)

522-951ft.

417-948ft.

Harperetal.(2008)

328-541ft.

328-541ft.

Rabeni(1991) 25-200ft.

25-200ft.

25-200ft.

Brownetal.(1990)

300-600ft.

AdditionalInformation

1Basedon9reptiles,19amphibians,14mammals,and23birdsthatwereidentifiedas"wetlanddependent"2Applicablefor58%ofspecies;1species100-200ft.;sevenspecies<100ft.3Applicablefor67%ofspecies;1species<100ft.;2species<35ft.4Applicablefor55%ofspecies;5spp.<100ft.;3spp.100-200ft.;9spp.>200ft.5Applicablefor80%ofspecies;2speciesfoundtobewithin100ft.6Wengeralsosuggestsadding2ft.forevery1%ofslope7Forthemaintenanceofstreambankandstreamchannelwidthintegrity8McElfish,Kihlsinger,&Nicholsaretheprincipalauthors9EachrecommendedRMZsuggestsaminimum'no-cut'zone:ponds:0ft.;greatponds:25ft.;4thorder+:25ft.;3rdorder:50ft.;1st&2ndorder:25ft.10ApplicableonlytoBlanding'sturtles

43

Summaryofknowledgegapsandresearchneedsidentifiedthroughthecompilationofthisliteraturereview.

• Aliteraturereviewexaminingtheextenttowhichhumanactivityhasdegradedwaterresourcespost-colonization,andwhatquantityoftheseresourcesareneededtoretainfunctioningecosystemservicesinasustainablemannerforbothhumansandbiodiversity.

• Researchthatillustratestheeffectsofhavingnobufferonawaterbody,andtheassociatedpercentofnutrientandcontaminantinputsthatenterthewaterbody.

• Calculablefunctionalrelationshipsbetweenbufferwidthandamountofpollutantreduction.1

• Controlledstudiestodeterminehowvariousbuffercharacteristics(e.g.vegetativecomposition,stemdensity,canopycover)affectbufferfunction.

• Robustmodelsestimatingfloodstoragecapacitybasedonbufferwidthandotherimportantattributes,includingbasingeomorphologyandsoiltype.

• Robustmodelsestimatingrun-offreductionandeffectivebankstabilitybasedonbufferwidthandotherimportantattributes,suchasslopeandsoiltype.

• Robustmodelsestimatinghowbufferwidthaffectstheamountofsurfacewaterinfiltrated.

Appendix4.

1Thisabilitytolinkbufferrestorationorprotectiontoaspecificamountofnutrientreductionisavitalstepinhelpingtopromotetheuseofgreeninfrastructureinmeetingwaterqualityimprovements.Despitetheresearchneed,theUniversityofNewHampshire’sStormwaterCenterismakingprogressonthisfrontthroughitsNHDESPollutantTrackingandAccountingPilotProject,whichwillidentifypotentialtoolstoenablemunicipalitiestoquantitativelyassessnonpointsourcepollutantloadreductionsintheGBE.

44

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