Biological Conservation 191 (2015) 29ndash37

Contents lists available at ScienceDirect

Biological Conservation

j ourna l homepage wwwe lsev ie r com locate b ioc

A riparian conservation network for ecological resilience

Alexander K Fremier a Michael Kiparsky b Stephan Gmur c Jocelyn Aycrigg d Robin Kundis Craig eLeona K Svancara f Dale D Goble g Barbara Cosens g Frank W Davis h J Michael Scott d

a Washington State University Pullman WA United Statesb Wheeler Institute for Water Law amp Policy University of California Berkeley CA United Statesc School of Environmental and Forest Sciences University of Washington Seattle WA United Statesd Department of Fish and Wildlife Sciences University of Idaho Moscow ID United Statese University of Utah SJ Quinney College of Law Salt Lake City UT United Statesf Idaho Department of Fish and Game Moscow ID United Statesg College of Law and Waters of the West University of Idaho Moscow ID United Statesh Bren School of Environmental Science and Management University of California Santa Barbara CA United States

Corresponding author Tel +1 509 335 8689E-mail address alexfremierwsuedu (AK Fremier)

httpdxdoiorg101016jbiocon2015060290006-3207copy 2015 Elsevier Ltd All rights reserved

a b s t r a c t

a r t i c l e i n f o

Article historyReceived 3 November 2014Received in revised form 27 May 2015Accepted 16 June 2015Available online xxxx

KeywordsClimate changeConnectivityCorridorsEcosystemsHabitat fragmentationMatrixProtected areasRiparian areasPolicy

A crucial gap exists between the static nature of the United States existing protected areas and the dynamicimpacts of 21st century stressors such as habitat loss and fragmentation and climate change Connectivity is avaluable element for bridging that gap andbuilding the ecological resilience of existing protected areas Howevercreating terrestrial connectivity by designing individual migration corridors across fragmented landscapes isarguably untenable at a national scaleWe explore the potential for use of riverine corridors in a Riparian Connec-tivity Network (RCN) as a potential contributor to a more resilient network of protected areas There is amplescientific support for the conservation value of riparian areas including their habitat their potential to connectenvironments and their ecosystem services Our spatial analysis suggests that they could connect protectedareas and have a higher rate of conservation management than terrestrial lands Our results illustrate that thespatial backbone for an RCN is already in place and existing policies favor riparian area protection Furthermoreexisting legal and regulatory goals may be better served if governance requirements and incentives are alignedwith conservation efforts focused on riparian connectivity as part of a larger landscape connectivity strategyWhile much research on the effectiveness of riparian corridors remains to be done the RCN concept provides away to improve connectivity among currently protected areas With focused attention increased institutionalcollaboration and improved incentives these pieces could coalesce into a network of areas for biologicalconservation

copy 2015 Elsevier Ltd All rights reserved

1 Introduction

The key challenge for biodiversity conservation in the Anthropoceneis counteracting the accelerating rate of species extinctions resultingfrom habitat loss and fragmentation climate change and invasivespecies (Baron et al 2009 Griffith et al 2009) In response to this chal-lenge reconstructing connectivity between protected areas is an impor-tant element of conservation infrastructure defined as landscapeattributes resulting from actions or policies designed to foster biologicalconservation such as protected areas conservation easements and soforth (Hannah et al 2002)

In the United States national parks wilderness areas and wildliferefuges were set aside primarily to preserve scenic geological wondersmigratory birds and game species and now form the core of the defacto public land system Conserving biodiversity was not the primary

consideration in selection and siting of this system (Aycrigg et al2013) The administrative boundaries of these areas were often locatedto avoid existing development rather than for ecological reasons(eg Wilderness Act 16 CUS sectsect 1131ndash1136) In addition the majorityof these areas were protected before ecological science recognized theimportance of large-scale ecological processes such as migrationsmetapopulation dynamics and gene flow (Mills 2012 Minor andLookingbill 2010) It is only recently that attention has been focusedon securing or restoring areas that provide structural and functionalconnectivity between protected lands

Concepts of socialndashecological resilience indicate that governance andconservation actions need to increase a systems ability to respond tonatural and human-induced perturbations (sensu Biggs et al 2012)One approach is to increase connectivity (Bengtsson et al 2003Elmqvist et al 2003) Developing spatially networked connectivitybetween existing protected areas enables species to move more readilyin response to changing environmental conditions (Johnston et al2013) This spatial aspect allows species and communities to survive

30 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

perturbations by avoiding them or resisting them and respondingafterwards by recolonizing The recolonized communities might besimilar to pre-disturbance ones or entirely transformed (Bengtssonet al 2003) For example connectivity fosters resilience to directionalclimate change (press disturbance) by increasing the potential forspecies redistribution into climatically suitable areas (Crimmins et al2011) Habitat connectivity can also contribute to escape from or re-colonization of occupied areas following events such as wildfires orfloods (pulse disturbance) (Elmqvist et al 2003)

If the goal therefore is to increase resilience through connectivityriparian networks should be an important component because theyconnect headwaters to lowlands in a structured complex and dendriticpattern (Beier 2012) Connecting riparian networks could complementthe existing protected landscape in which higher elevation areas aretypically emphasized and lowlands under-represented (Noss et al1996) Although data on the degree to which riparian areas serve ascorridors for species movement is limited there is evidence that evenan anthropogenically disturbed riparian corridor has the potential toreplicate many of the functions of an undisturbed one (Hilty andMerenlender 2004) For example Hilty and Merenlender (2004)found that although native mammalian predators (eg coyote Canislatrans raccoon Procyon lotor) preferred wider riparian corridors theynonetheless used narrower human-disturbed corridors in agriculturallandscapes In addition wildlife movement through road underpassesassociated with rivers and streams is well documented (Clevengerand Waltho 2000 Santos et al 2011) Although disturbed ripariancorridors are not the equivalent of undisturbed ones (Battin 2004)this body of literature suggests that species will use disturbed ripariancorridors when undisturbed ones do not exist

Riparian areas can play an important role in providing habitatconnectivity for many species in fragmented or heterogeneous land-scapes (Hilty and Merenlender 2004) These areas typically supportassemblages of hydrophilic organisms and are characterized by the in-fluence of periodic water inundation and the exchange of materialsand energy with the surrounding ecosystems namely the stream andupland areas (Naiman and Decamps 1997) Although riparian areastypically are not large they do offer extensive linear networks thatallow many species to move through otherwise inhospitable areas(Rouquette et al 2013 Tremblay and St Clair 2011) The role thatriparian areas play as corridors between and among protected areas ispoorly documented particularly with respect to what characteristicspromote connectivity for which species The use of riparian areas formovement is species-specific (Gilbert-Norton et al 2010 Lees andPeres 2008) Nonetheless multiple terrestrial species rely on riparianareas at some point in their life history (Naiman and Decamps 1997)most commonly for migration through human-modified landscapes(Santos et al 2011) Additionally a variety of species use riparian corri-dors for access to water escape from predators cover food nestinghabitat and dispersal or movement between habitat patches (Brostand Beier 2012)

Rebuilding habitat connectivity with riparian networks is no pana-cea particularly in fragmented and altered landscapes (Goetz et al2009) The condition of riparian areas is highly variable andmany ripar-ian areas will likely require restoration before they serve as functionalcorridors (Theobald et al 2010) However even small sections ofdegraded riparian areas can act as chokepoints by limiting larger-scaleconnectivity and some animals might not use intact riparian areassurrounded by human structures and activity It is yet unclear whatbuffer width provides connectivity for the widest breadth of speciesConversely increased connectivity can have negative ecological influ-ences (Simberloff et al 1992) Regardless although connectivitymight facilitate the spread of invasive species and disease or increaseddisturbance improved habitat connectivity is a net positive conserva-tion outcome (Hannah et al 2002 Shafer 2014) Moreover Haddadet al (2014) found no broad evidence to support the possible undesir-able side-effects of increased habitat connectivity and further suggested

that wider corridors and softer corridor edges could ameliorate poten-tial negative impacts

Restoration of river and riparian areas benefits not only species con-servation but also water quality and esthetics (Bernhardt et al 2005)Restoration actions including reactivating floodplains build uponexisting efforts that protect valuable ecosystem services such as waterfiltration recreation and flood control (Brauman et al 2007 Fremieret al 2013) Although they are often degraded (Theobald et al 2010)riparian forests account for much of the remnant forests on numerouslandscapes (Lees and Peres 2008) Increased conservation efforts inthese areas may also increase the ability of species to move throughintensively managed landscapes Restoring and protecting riparianareas thus can serve human needs while also providing a connectedriparian connectivity network

Furthermore a riparian connectivity network could take advantageof existing policy mechanisms That is a project to establish such a net-work could leverage an existing suite of administrative state and feder-al policies that already protect riparian areas and thereby avoid thepolitical battles that would be involved in enacting new laws (Citron2010 Lacey 1996 Thompson 2004) A key challenge therefore willbe to coordinate restoration actions conservation easements andother conservation-related actions associated with existing policies tofoster large-scale habitat connectivity at a continental scale

We analyzed the current pattern of the protected area system inrelation to riparian management on public and private lands for thecontiguous United States (lower 48 states) to examine the practical po-tential of implementing a national Riparian Connectivity Network(RCN) that could coordinate protection restoration and managementof riparian areas to build habitat connectivity among existing protectedareas We applied a coarse-scale spatial analysis to quantify the poten-tial riparian linkages between existing protected lands Recognizingthat even an ideal physical solution is promising only to the degreethat it can be implemented we developed the concept of an RCN bycombining initial evidence for its geospatial and ecological feasibilitywith a conceptual analysis of its practical and legal potential forimplementation

2 Materials and methods

To assess the biophysical potential of an RCNwe quantified the typeamount and location of streamriparian protection for continental USoutside of Alaska using available spatial dataWe employed a geograph-ic information system (GIS) to analyze spatial and jurisdictionalpatterns in riparian management (ArcGIS version 10 ESRI 2011) Weaddressed four questions regarding distribution area and context ofexisting protected areas and their relationship to river corridors1) How many of the existing protected areas are connected to one ormore protected areas via a river corridor 2) What percentage of ripar-ian corridors is buffered by protected areas 3) What is the spatialpattern of riparian area protection across the lower 48 states Finally4) are conservation easements spatially associated with riparian areas

21 Geospatial data

We analyzed three publicly available spatial databases 1) ProtectedAreas Database of the US (PAD-US) 2) National Conservation EasementDatabase (NCED) and 3) National Hydrography Database (NHDplus)PAD-US represents public land ownership and conservation landsincluding privately owned protected areas (PADUS version 12 USGS-GAP accessed 2011) Thenative resolution of PAD-US is variable becausedata are provided by multiple agencies with a defined standard of1100000 spatial accuracy (USGS-GAP 2013) Lands are assignedconservation status codes (ie GAP Status codes) that both denote thelevel of biodiversity preservation and indicate other natural recreation-al and cultural uses (See Table 1 for code descriptions)

Table 1GAP status codes within PAD-US denote the intended level of biodiversity protection andindicate other natural recreational and cultural uses These status codes emphasize themanaging entity rather than the landowner because the focus is on long-term manage-ment intent Therefore an area gets a status code of permanently protected because thatis the long-term management intent (Aycrigg et al 2013) Note the descriptions do notdetail specific riparian area protection because protection depends upon the managingagency

Status Description

1 Areas having permanent protection from conversion of natural land coverand a mandated management plan in operation to maintain a natural statewhere disturbance events (of natural type frequency intensity andlegacy) are allowed to proceed without interference or are mimickedthrough management

2 Areas having permanent protection from conversion of natural land coverand a mandated management plan in operation to maintain a primarilynatural state but which may receive uses or management practices thatdegrade the quality of existing natural communities includingsuppression of natural disturbance

3 Areas having permanent protection from conversion of natural land coverfor the majority of the area but subject to extractive uses of either a broadlow intensity type (eg logging) or localized intense type (eg mining)This status also confers protection to federally listed endangered andthreatened species throughout the area may be conferred

4 Areas with no known public or private institutional mandates or legallyrecognized easements or deed restrictions held by the managing entity toprevent conversion of natural habitats to anthropogenic habitat typesConversion to unnatural land cover throughout is generally allowed andmanagement intent is unknown

31AK Fremier et al Biological Conservation 191 (2015) 29ndash37

We use the term lsquoprotectedrsquo throughout this paper in two differentways First in the data analysis we define lsquoprotectedrsquo as GAP Status 1and 2 lands plus GAP Status 3 lands but only for riparian areas Theselands have permanent protection from conversion of natural landcover (Table 1) We excluded GAP status 3 lands that are not riparianand GAP status 4 lands because either no formal protection exists orits status is unknown We note that protection be it formal or adminis-trative does not mean full protection in all cases nor does it mean thelands are not already degraded This usage implies protection but notnecessarily functional habitat Second outside of the data analysis andconsistent with the vision presented in the article we use the termlsquoprotectedrsquo in a more general sense to imply land cover protectionfrom non-conservation related activities

Briefly GAP Status 1 lands includewilderness areaswith permanenthabitat protection that allows natural disturbance events to occur GAPStatus 2 lands have permanent habitat protection but may receive usesor management practices that degrade the quality of existing naturalcommunities including the suppression of natural disturbances GAPStatus 3 lands have permanent protection for federally listed endan-gered and threatened species although extractive uses are permittedon typically upland areas (eg logging mining and grazing) Many ofthese lands also have administrative policies to protect riparian landshowever the strength and status of this protection is highly variable(NRC 2002) GAP Status 3 lands represent a large portion of the publiclymanaged lands which are predominately managed by the US ForestService and US Bureau of Land Management (approximately 300million ha) (Aycrigg et al 2013) GAP Status 4 lands have nomandated conservation protection although conservation practicesmight occur (eg Department of Defense State Land Board Bureau ofIndian Affairs) For the purpose of this analysis all lands with noassigned GAP Status code were designated GAP Status 4 lands Conser-vation easements were also designated as Status 4 because they havean unknown conservation-management mandate

The NCED database is a continuously updated spatial databaseof conservation easement lands in the US compiled from land trustand public agency records (NCED accessed June 2012) NCED includesapproximately 162 million ha of privately owned conservationeasement lands Prior to conducting our analysis we eliminatedduplicate data between NCED and PAD-US

The NHDplus database includes streamlines for the US digitizedfrom aerial photos and USGS quadrangles at a scale of 1100000(NHDplus version 2) For a national analysis NHDplus provides thebest data available for representing the US stream network but it alsoincludes large irrigation ditches and other human-made waterways Itis important to highlight that our unit of analysis is the streamline andnot the riparian corridor Currently there is no national inventory ofriparian areas Additionally we recognize that riparian areas withinthe US vary significantly in habitat quality While finer-grained analysismight be possible this level of detail is beyond the scope of our nationalscale analysis

We summarized protection by Strahler Stream Order Stream orderis a measure of the stream size and is a hydrographic metric for indicat-ing the position of a specific stream segment within a watershedStrahler stream order defines the smallest tributaries as order 1 and in-creases as streams join to a value of 10 at the seaward ends of the largestrivers As an example the last segment of the Mississippi River is a 10thorder stream Headwater (mainly first and second order) streamscomprise up to 80 of the stream network by linear measurement Inaddition NHDplus delineates watersheds of varying sizes from topo-graphic data to define Hydrologic Unit Codes (HUCs) Regions (ie 8-digit HUCs) are the largest delineations and are defined topographicallyfor the largest terminal watersheds Small terminal watersheds (10- or12-digit HUCs) are clustered within regions but by definition are nothydrologically connected

22 Data analysis

221 Protected areas connected through a stream networkFor our analysis we defined protected areas both state and federal

as those landswith aGAP Status of 1 and 2 additionallywe includeGAPStatus 3 riparian lands because riparian areas have administrativeprotection in most cases (Table 1) We calculated the number ofprotected areas connected to at least one other protected area via thestream network We counted protected areas as connected when amapped river intersected the boundary of the protected areas Wefound that every protected area had at least one mapped river flowingthrough its bounding polygon while most areas had multiple connec-tions Any contiguous protected polygons with shared protected status1 and 2 or 3 were merged into a single unit we performed this opera-tion to better reflect how species would use an adjacent protectedparcel as a continuous habitat A protected area was considered lsquocon-nectedrsquo through the stream network if it was connected to at least oneother protected area within an 8-digit HUC Protected areas that arelocated in separate 8-digit HUCs (the largest watersheds) cannot beconnected through a riparian corridor as they exist in separatewatersheds

222 Percent protection of stream network by conservation status streamorder and HUC

Wedefine ldquopercent protectedrdquo as the percentage of linear rivermileslyingwithin either a protected area or aworking landscapewith admin-istrative riparian protection (eg GAP Status land 1ndash3) ldquoPercentprotectedrdquo is thus a proxy for the amount of an RCN that is alreadyimplemented We calculated the percentage of the current mappedstream network by GAP Status Code 1 2 or 3 by Strahler streamorder and by governing agency It is important to note that our estimateof riparian protection is in linear units (stream length) not areal unitsand that this will impact the estimate and any comparison withterrestrial measures of protection (Aycrigg et al 2013) In additionour decision to include GAP status 3 riparian lands as ldquoprotectedrdquo signif-icantly affects the percent protected lands In our analysis non-riparianGAP status 3 lands are not protected

For this analysis streamlines with no stream order demarcationwere not used in the analysis as they typically include streamlinesthrough lakes reservoirs or irrigation canals To calculate the percent

32 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

protected we assumed that if the stream centerline lies within aprotected area both sides of the streams riparian areas are protectedexcept when the stream defines the border of the protected area Weprocessed a 30-meter buffer inside the perimeter of each protectedarea to limit this edge effect We used these reduced polygons in ouranalysis to quantify the percentage of the total stream length protectedWe believe our estimate is accurate in terms of administrative protec-tion but also conservative in its extent In addition for publicly ownedland we calculated the percentage of the stream network managed byeach governmental agency

223 Proximity of conservation easements to riparian areasWehypothesized that conservation easements fromNCEDwould be

biased toward riparian areas To estimate this bias we used a distance-based analysis to capture those easements that might fall within ariparian area Specifically we calculated the Euclidean distance betweeneach conservation easement edge and the closest stream centerlineWeperformed this analysis initially with the entire NHDplus dataset thenonly for stream orders greater than 1 and again for stream orders great-er than 2 Excluding the lowest order streams which typically supportlittle or no adjacent riparian habitat should provide a more reasonableestimate of the association of easements with floodplain and ripariancorridors

3 Results

31 Protected areas are connected through a stream network

Ninety-five percent of all federally protected areas are connected bya stream network to at least one other protected area In many regionsmultiple connections exist between protected areas The few protectedareas without riparian connections are found in small basins directlydraining to the ocean or basins with terminal drains into deserts(eg eastern Sierra Nevada rivers flowing into Nevada)

32 Stream network protection varies by conservation status stream orderand HUC

The percentage of land along protected stream segments generallydecreases as stream order increases (Fig 1) The average protection ofthe stream network is 248 Streams classified as orders 1ndash3 make up80 of the overall network in general Although the general pattern of

Fig 1 Percent protection of stream network by groups of stream order Based on PAD-US and Nthe average protection is 248 The average is highly skewed because headwater streams (str

protection of streams decreases from smaller to larger streams(ie there is a bias in protection toward riparian areas in headwaterstreams as expected) the percent of protection for riparian areas inlarge streams does not drop below 15 with a range of 255ndash159 oflands with GAP Status codes 1ndash3 The average protection (248) iscloser to the highest protection (255) because the stream network iscomposed of 80 headwater streams As such riparian areas aroundheadwater streams generally have higher protection status than ripari-an areas associated with large rivers The explanation for this higherprotection is in part because of the amount of GAP Status 3 landsWe in-cluded these lands in the lsquoprotectedrsquo category because they typicallyhave administrative protection of riparian lands but not upland areas(Table 1) however it is important to note that upland land use canimpact riparian structure and function and there is high variability inthe strength of that protection and the ecological condition (NRC2000) Stream orders 1ndash3 have the highest percent of stream lengthprotected on GAP Status 3 lands particularly in the western US (Fig 2)

33 Conservation easements are often near to streams

Conservation on private lands through conservation easements mayhave a spatial bias toward riparian areas most notably around largerrivers (Fig 3) Of the 162 million ha of land in conservation easements57 are within 100 m of a stream channel and 93 are within 1 km ofthe stream centerline The proportion decreases when first and secondorder streams are removed (19 and 68 respectively) For examplethe pattern of easements and their distance to the Mississippi and RedRivers in the southern portion of the US indicates numerous easementswithin the floodplain (Fig 3) Conservation easements are clusteredgenerally around main river corridors

4 Discussion

Any conservation effort is only as good as its potential for implemen-tation through action at relevant ecological scales nomatter how clean-ly the proposed solutionmightmap in networked spaceWe argue that1) current policies broadly reflect societal concern for the protection ofriparian areas Our analysis suggests that an RCN is an emerging proper-ty of the streamnetwork and therefore a nascent backbone for the RCNmay already exist 2) scientific evidence supports the conservationvalue of an RCN to help mitigate the impacts of climate change and up-land habitat fragmentation and 3) although an RCNmay bemore easily

HDplus databases See Table 1 for descriptions of GAP status codes Over all stream orderseam orders 1ndash3) make up 80 of the total stream network by linear unit

Fig 2 Percent of stream length protectedwithin NHDplus 8-digit HUCwatersheds across the contiguous US Protection of stream and riparian areas in thewestern US is far greater than inthe Midwestern states and to a lesser degree the Eastern states Protection is defined as lands with GAP status codes 1ndash2 and conservation easements

33AK Fremier et al Biological Conservation 191 (2015) 29ndash37

implemented than other connectivity approaches from policy andmanagement standpoints conservation is better served if riparianconnectivity is part of a larger landscape connectivity strategy Ourvision is that the RCN would coordinate protection restoration andmanagement of riparian areas to build habitat connectivity amongexisting protected areas The primary value of this research is its con-ceptual and integrative approach Questions remain about the benefitsintegrity and management activities in riparian areas Howeverthe RCN provides context for future research and management onthese issues A research program to flesh out the RCN concept wouldnecessarily follow this conceptualization

The spatial distribution of conservation easements is additionalevidence of an emerging RCN Our analysis indicates that conservationeasements on private lands have a bias toward proximity to rivers(57 within 100 m and 93 within 1 km) Although the motivationfor establishing conservation easements varies the spatial pattern ofeasements suggests that protection of land close to rivers is important(Kline et al 2000 Ryan et al 2003) Although there are concernsthat conservation easements do not fully protect lands from non-conservation-related activities (Rissman et al 2007) conservationeasements nevertheless provide a mechanism for protection of ripariancorridors and could be tailored to meet that need The increasing inter-est in conservation easements by private landowners suggests themotivation to protect riparian lands exists (Mann et al 2013)

We acknowledge the potential limitations of re-building habitatparticularly in the face of complex topography rapid change inelevation or micro-climatic variation along the length of a corridornot to mention current condition of most riparian areas Many riparianareas will require restoration before they serve as functional corridors(Theobald et al 2010) and the buffer width to facilitate connectivityremains unclear particularly through human dominated areasAdditionally concerns about the potential undesirable side effects ofincreased connectivity exist (Simberloff et al 1992) but the existingnascent RCN could also serve as a research focus for assessing thevalidity of these concerns

41 A riparian conservation network is emerging

The geospatial patterns suggest that the backbone for an RCNis emerging through a combination of existing policy on publiclands and incentives for conservation easements on private lands(Figs 1ndash3) Although riparian lands are notmanaged as a formal systemstreams already have greater protection than upland areas Riparianareas are managed through various mechanisms including protectedlands management (eg wilderness parks and forests) measurestaken in response to the requirements of regulatory programs(eg the Clean Water Act (CWA) the Endangered Species Act (ESA)and the state-level implementation programs) and through incentive-based programs such as the USDAs Conservation Reserve Program(CRP) (NRC 2002)

We interpret this legal and administrative protection as strongevidence of the perceived importance of riparian area managementMoreover this level of protection (248) is more than double thelevel of protection of terrestrial areas (10 Aycrigg et al 2013) mainlybecause riparian areas have protection on public lands This elevatedprotection stems from the ecosystem services provided by riparianareas For example placement of lands in GAP Status 3 (national forestand BLM public lands) provides protection of riparian areas that mayassist in meeting water quality requirements (eg temperature pollut-ants) Administrative protection of course does not always mean func-tional protection and a great need remains for restoration of degradedriparian areas including in some areas a widening of protected riparianbuffers (Kondolf et al 1996) Nonetheless it is a beginning Further-more active tracking of the actual protection of riparian areasmay assistlandmanagers inmeeting area goals but certainlymore research is nec-essary to understand if administrative protection of riparian areas leadsto functional connectivity Our classification of GAP Status 3 lands asfunctional habitat denotes formal protection but is probably optimisticgiven degraded land and proximity to human activities

A viable RCN could build on the existing governance that supportssocietal interests in clean water and naturally functioning rivers

Fig 3 Riparian connectivity emerging from current policy The map shows the concentration of easements near or within the floodplain along the Mississippi and Red Rivers which col-lectively start to form a de facto corridor

34 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

governance that is nevertheless not currently coordinated for purposesof connectivity (Arthington et al 2010) Such mechanisms have beenput in place for a variety of services including water quality (CWA)single species protection (ESA) or soil conservation (CRP) The CWAhas already helped to restore and prevent degradation of many riparianareas to improve water quality through its direct controls on pollutersand restrictions on aquatic habitat destruction (Adler et al 2013)Nevertheless many waters across the United States remain impairedin part because of failure to integrate land use regulation with imple-mentation of federal laws such as the CWA and ESA (Cosens and Stow

2014) Mechanisms already have emerged to address the failure ofregulatory programs like the CWA and ESA such as incentive basedprograms like the USDA-CRP (NRC 2002)

The value of riparian protection for achieving habitat connectivityand the need to meet water quality standards may increase incentivesfor riparian protection from land conversion with minimal change inexisting law The CWA provides some incentives to develop an RCN asshown by the role it plays in driving riparian corridor protection(eg the US EPAs promotion of watershed-scale management andother state level efforts Section 404s restrictions on destruction and

35AK Fremier et al Biological Conservation 191 (2015) 29ndash37

adversemodification ofwetlands and other aquatic areas) For exampleto achieve temperature requirements of discharge permits under theCWA entities governing watersheds such as the Willamette River andthe Virginia regions of the Chesapeake Bay watershed have set uptrading programs in which a municipality pays for restoration ofshade in upstream riparian areas rather than the expensive alternativeof mechanical cooling

Implementation of the ESA has also encouraged riparian area protec-tion A high percentage of species listed for protection under the ESA areaquatic (Craig 2014) Compliance with both the CWA and ESA arefactors in developing habitat conservation plans (Native Fish HabitatConservation Plan) Similarly forestry programs at federal (NorthwestForest Plan) and state (Idaho Forestry Program Nez Perce Term SheetNez PercendashIdaho Water Rights Settlement) levels require buffer zonesalong riparian corridors in timber harvest areas The implementationof the ESA in the Pacific Northwest has placed the Federal EmergencyManagement Agency under pressure to change the National FloodInsurance Program (NFIP) by removing incentives to separate riversfrom their floodplains to allow insured development in the formerflood zone (see National Wildlife Federation v Federal EmergencyManagement Agency No C11ndash2044ndashRSM 2014 WL 5449859 WDWash Oct 24 2014)

In short CWA water quality standards ESA habitat requirementsand flood risk management goals may all be advanced by protectingsmall amounts of land in riparian corridors In addition to these regula-tory incentives planning approachesmdashincluding ESA Section 7 jeopardyassessments and the National Environmental Policy Act (NEPA)and its state counterparts the California Environmental Quality Act(CEQA)mdashcan allow for or even mandate coordination of ripariancorridor protection Other extant legal and policy protections includefinancial incentives to protect riparian lands such as incentive programsfor agriculture in the US Farm Bill (although these incentives werereduced in 2014) Another alternative is the purchase of private riparianlands by public entities or non-governmental organizations such as TheNature Conservancys water programs (Greenway program conserva-tion easements and other water programs Rollins Palmer 2008)

Other legal mechanisms associated with land management arealready playing a role in the emergence of riparian conservationparticularly across the federal public lands Notably 78 of publiclands are managed by four agenciesndashndashUSDA Forest Service US Bureauof LandManagement US National Park Service and US Fish andWildlifeServicemdashincreasing the potential for inter-agency coordination (Aycrigget al 2013) Additionally an RCN could enable a scalable policy withnested efforts to integrate currently independent and loosely coordinat-ed federal state tribal local and private actions

In addition riparian areas are pre-defined by the stream networkwhich simplifies the process of selecting corridor routes compared tospecies-specific terrestrial corridors (Hilty et al 2006) By simplifyingthe corridor selection procedure the RCN thus offers a simpler imple-mentation strategy Nonetheless although this simplicity is attractiveat conceptual and policy levels the effectiveness in improving connec-tivity and species survival through an RCN must be evaluated at thefield level For example the RCN cannot serve as a replacement corridorselection procedure in situations where species will not use riparianareas or the areasmight not have suitable riparian corridors In additionmore detailed local-scale analysis is needed to determine how andwhere local riparian corridors should be concentrated RCN researchalong these lines could dovetail with research already being completedsuch as the Riparian Climate-Corridors which incorporates mappedriparian areas and climate projections (Beier 2012 Krosby et al 2014)

42 A policy path to a riparian connectivity network

Although conceptually simple building connected corridors requirescoordination among governance agencies and private landownersThere currently is no federal policy mechanism for connecting

landscapes at any scale Although planning is underway for large-scalecorridors (ecoregions biomes) efforts lack sufficient generality fornational-scale application (Hilty et al 2006) Nevertheless there aremultiple examples of regional-scale cooperative restoration effortsthat may offer governance models for building connectivity TheChesapeake Bay region inMaryland andVirginia the Florida Evergladesand the Greater Yellowstone Ecosystem in Wyoming Montana andIdaho are regional examples of multiagency collaborative managementto maintain conservation integrity (Noss et al 2002) as are theWestern Governors Associations discussions of a migratory corridoror Washington States climate-change-related efforts to addressconnectivity In addition the Partners in FlightMigratory Bird Conserva-tion program specifically targets migratory species and has hadconservation-related successes throughout North America working atlarger scales (Carter et al 2000) This program functions at the regionalscale but is planned and coordinated through lsquojoint venturersquo partner-ships and management at international scale

Coordination at coarser scales can lead to protection at finer scalesFor example wetland and riparian areas play a key role in buildingconnectivity for migrating waterfowl in the North AmericanWaterfowlManagement Plan (Williams et al 1999) Many of these efforts toimprove habitat connectivity attempt to optimize the construction ofhabitat corridors between individual preserves focusing on specificspecies or small assemblages of species within the constraints of localgeographies and prioritizing riparian lands for restoration with theirspatial configuration in mind (Theobald et al 2012) However achallenge for implementing an RCN particularly in western states isthe complicated planning and implementation of the allocation ofwater through private water rights (Adler et al 2013)

Federal resource agencies have a checkered history of workingtogether toward a common purpose in part because each is governedby different legal requirements Yet the Landscape Conservation Coop-eratives (LCCs) in the US that began as the result of a Secretarial Orderfrom the Department of the Interior in 2009 (Order No 3289 Sept 142009) exemplify emergent coordination to solve issues that persist atlarger scales (Millard et al 2012) LCCs aim to provide scientificexpertise and coordination among public and private institutions at alandscape scale In addition implementation of the ESA has led to coor-dination across multiple agencies in examples such as the NorthwestForest Plan A more proactive coordinated approach to building land-scape habitat connectivity could be incorporated into the missions ofrelevant agencies (eg National Park Service US Fish and WildlifeService Bureau of LandManagement USDA Forest Service) Presidentialguidance through an Executive Order could be used to advance thedevelopment of a more comprehensive RCN In addition at least somestates seem to be willing to pursue similar efforts for state publiclands (Citron 2010) Conversations on such lsquotop-downrsquo options arealready underway in national policy circles (USFWS 2013) In additionfactors other than species conservation are already driving riparianprotection such as ecosystem services One clear example of agencycoordination to manage riparian areas for multiple benefits is the YoloBasin near Sacramento California (Opperman et al 2009) other suchsolution have been recently proposed (Greco and Larsen 2014) Thisarea supports multiple typically competing interests by managing ricefarming and wildlife conservation while allowing flood water storageduring critical times with the added benefit of migratory bird habitatThe multiple benefits of riparian protection illustrated in the YoloBasin example can broaden actual and potential sources of supportfor an RCN including efforts to improve aquatic ecosystem servicessuch as filtration riparian vegetation and floodplain connectivity thatimprove water quality bank stabilization and flood control as well asesthetics (Bernhardt et al 2005 Fremier et al 2013) Explicitly incor-porating ecosystem services into conservation corridor protectionmechanisms would open riparian protection efforts to a broader arrayof institutions and funding sources including agencies charged withprotecting water quality and reducing flood risks and private interest

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

Adler RW Craig RK Hall ND 2013 Modern Water Law Private Property PublicRights and Environmental Protections 1st ed Foundation Press

Arthington AH Naiman RJ McCLAIN ME Nilsson C 2010 Preserving the biodiversityand ecological services of rivers new challenges and research opportunities FreshwBiol 55 1ndash16 httpdxdoiorg101111j1365-2427200902340x

Aycrigg JL Davidson A Svancara LK Gergely KJ McKerrow A Scott JM 2013Representation of ecological systems within the protected areas network of theContinental United States PLoS One 8 e54689 httpdxdoiorg101371journalpone0054689

Baron JS Gunderson L Allen CD Fleishman E McKenzie D Meyerson LA OropezaJ Stephenson N 2009 Options for national parks and reserves for adapting toclimate change Environ Manag 44 1033ndash1042 httpdxdoiorg101007s00267-009-9296-6

Battin J 2004 When good animals love bad habitats ecological traps and the conserva-tion of animal populations Conserv Biol 18 1482ndash1491 httpdxdoiorg101111j1523-1739200400417x

Beier P 2012 Conceptualizing and designing corridors for climate change Ecol Restor312ndash319

Bengtsson J Angelstam P Elmqvist T Emanuelsson U Folke C Ihse M Moberg FNystrom M 2003 Reserves resilience and dynamic landscapes AMBIO A J HumEnviron 32 389ndash396 httpdxdoiorg1015790044-7447-326389

Bernhardt ES Palmer MA Allan JD Alexander G Barnas K Brooks S Carr JClayton S Dahm C Follstad-Shah J Galat D Gloss S Goodwin P Hart DHassett B Jenkinson R Katz S Kondolf GM Lake PS Lave R Meyer JLODonnell TK Pagano L Powell B Sudduth E 2005 Synthesizing US river resto-ration efforts Science 308 636ndash637 (80-)

Biggs R Schluumlter M Biggs D Bohensky EL BurnSilver S Cundill G Dakos V DawTM Evans LS Kotschy K Leitch AM Meek C Quinlan A Raudsepp-HearneC Robards MD Schoon ML Schultz L West P 2012 Toward principles for

enhancing the resilience of ecosystem services Annu Rev Environ Resour 37421ndash448 httpdxdoiorg101146annurev-environ-051211-123836

Brauman KA Daily GC Duarte TK Mooney HA 2007 The nature and value ofecosystem services an overview highlighting hydrologic services Annu RevEnviron Resour 32 67ndash98 (doihttpdxdoiorg101146annurevenergy32031306102758 U httparjournalsannualreviewsorgdoiabs101146annurevenergy32031306102758)

Brost BM Beier P 2012 Comparing linkage designs based on land facets to linkagedesigns based on focal species PLoS One 7 e48965 httpdxdoiorg101371journalpone0048965

Carter M Hunter W Pashley D Rosenberg K 2000 Setting conservation prioritiesfor landbirds in the United States the Partners in Flight approach Auk 117 541ndash548

Citron A 2010 Working rivers and working landscapes using short-term water useagreements to conserve Arizonas riparian and agricultural heritage ArizonaJ Environ Law Policy 1

Clevenger AP Waltho N 2000 Factors influencing the effectiveness of wildlifeunderpasses in Banff National Park Alberta Canada Conserv Biol 14 47ndash56httpdxdoiorg101046j1523-1739200000099-085x

Cosens B Stow C 2014 Resilience and water governance addressing fragmentationand uncertainty in water allocation and water quality law In Garmestani A AllenCR (Eds) Social-Ecological Resilience and Law Columbia University Press p 416

Craig RK 2014 Does the Endangered Species Act Preempt State Water LawCrimmins SM Dobrowski SZ Greenberg J a Abatzoglou JT Mynsberge AR

2011 Changes in climatic water balance drive downhill shifts in plant speciesoptimum elevations Science 331 324ndash327 httpdxdoiorg101126science1199040 (80-)

ElmoreW Beschta RL 1987 Riparian areas perceptions inmanagement Rangelands 9Elmqvist T Folke C Nystrom M Peterson G Bengtsson J Walker B Norberg J 2003

Response diversity ecosystem change and resilience Front Ecol Environ 1488ndash494 httpdxdoiorg1018901540-9295(2003)001[0488RDECAR]20CO2

Fremier AK Declerck FAJ Bosque-Peacuterez NA Carmona NE Hill R Joyal T Keesecker LKlos PZ Martiacutenez-Salinas A Niemeyer R Sanfiorenzo A Welsh K Wulfhorst JD2013 Understanding spatiotemporal lags in ecosystem services to improve incentivesBioscience 63 472ndash482 httpdxdoiorg101525bio20136369

Gilbert-Norton L Wilson R Stevens JR Beard KH 2010 A meta-analytic review ofcorridor effectiveness Conserv Biol 24 660ndash668 httpdxdoiorg101111j1523-1739201001450x

Goetz SJ Jantz P Jantz CA 2009 Connectivity of core habitat in the NortheasternUnited States parks and protected areas in a landscape context Remote SensEnviron 113 1421ndash1429 httpdxdoiorg101016jrse200807019

Goldman RL Tallis H 2009 A critical analysis of ecosystem services as a tool inconservation projects the possible perils the promises and the partnerships AnnN Y Acad Sci 1162 63ndash78 httpdxdoiorg101111j1749-6632200904151x

Greco SE Larsen EW 2014 Ecological design of multifunctional open channels forflood control and conservation planning Landsc Urban Plan 131 14ndash26 httpdxdoiorg101016jlandurbplan201407002

Griffith B Scott JM Adamcik R Ashe D Czech B Fischman R Gonzalez P Lawler JMcGuire AD Pidgorna A 2009 Climate change adaptation for the US NationalWildlife Refuge System Environ Manag 44 1043ndash1052 httpdxdoiorg101007s00267-009-9323-7

Haddad NM Brudvig La Damschen EI Evans DM Johnson BL Levey DJ OrrockJL Resasco J Sullivan LL Tewksbury JJ Wagner Sa Weldon AJ 2014 Potentialnegative ecological effects of corridors Conserv Biol 28 1178ndash1187 httpdxdoiorg101111cobi12323

Hannah L Midgley GF Lovejoy T BondWJ Bush M Lovett JC Scott DWoodwardFI 2002 Conservation of biodiversity in a changing climate Conserv Biol 16264ndash268 httpdxdoiorg101046j1523-1739200200465x

Hilty JA Merenlender AM 2004 Use of riparian corridors and vineyards by mammali-an predators in Northern California Conserv Biol 10 126ndash135

Hilty JA Lidicker WZ Merenlender AM 2006 Corridor Ecology The Science andPractice of Linking Landscapes for Biodiversity Conservation 1st ed Island PressWashington DC

Johnston A Ausden M Dodd AM Bradbury RB Chamberlain DE Jiguet F ThomasCD Cook ASCP Newson SE Ockendon N Rehfisch MM Roos S Thaxter CBBrown A Crick HQP Douse A McCall RA Pontier H Stroud DA Cadiou BCrowe O Deceuninck B Hornman M Pearce-Higgins JW 2013 Observed andpredicted effects of climate change on species abundance in protected areas NatClim Chang 3 1055ndash1061 httpdxdoiorg101038nclimate2035

Kline JD Alig RJ Johnson RL 2000 Forest owner incentives to protect riparian habitatEcol Econ 33 29ndash43 httpdxdoiorg101016S0921-8009(99)00116-0

Kondolf GM Kattelman R Embury M Erman D 1996 Status of riparian habitat SierraNevada Ecosystem Project Final Report to Congress Vol II Assessments andScientific Basis for Management Options University of California Centers for Waterand Wildland Resources Davis CA pp 1009ndash1030

Krosby M Norheim R Theobald D McRae BH 2014 Riparian Climate-CorridorsIdentifying Priority Areas for Conservation in a changing Climate

Lacey HB 1996 Dancing in place the Clinton Administration and aquatic ecosystemprotection in the Pacific Northwest Nat Resour J 36

Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

Millard MJ Czarnecki CA Morton JM Brandt LA Briggs JS Shipley FS Sayre RSponholtz PJ Perkins D Simpkins DG Taylor J 2012 A national geographic

Table 1GAP status codes within PAD-US denote the intended level of biodiversity protection andindicate other natural recreational and cultural uses These status codes emphasize themanaging entity rather than the landowner because the focus is on long-term manage-ment intent Therefore an area gets a status code of permanently protected because thatis the long-term management intent (Aycrigg et al 2013) Note the descriptions do notdetail specific riparian area protection because protection depends upon the managingagency

Status Description

1 Areas having permanent protection from conversion of natural land coverand a mandated management plan in operation to maintain a natural statewhere disturbance events (of natural type frequency intensity andlegacy) are allowed to proceed without interference or are mimickedthrough management

2 Areas having permanent protection from conversion of natural land coverand a mandated management plan in operation to maintain a primarilynatural state but which may receive uses or management practices thatdegrade the quality of existing natural communities includingsuppression of natural disturbance

3 Areas having permanent protection from conversion of natural land coverfor the majority of the area but subject to extractive uses of either a broadlow intensity type (eg logging) or localized intense type (eg mining)This status also confers protection to federally listed endangered andthreatened species throughout the area may be conferred

4 Areas with no known public or private institutional mandates or legallyrecognized easements or deed restrictions held by the managing entity toprevent conversion of natural habitats to anthropogenic habitat typesConversion to unnatural land cover throughout is generally allowed andmanagement intent is unknown

31AK Fremier et al Biological Conservation 191 (2015) 29ndash37

We use the term lsquoprotectedrsquo throughout this paper in two differentways First in the data analysis we define lsquoprotectedrsquo as GAP Status 1and 2 lands plus GAP Status 3 lands but only for riparian areas Theselands have permanent protection from conversion of natural landcover (Table 1) We excluded GAP status 3 lands that are not riparianand GAP status 4 lands because either no formal protection exists orits status is unknown We note that protection be it formal or adminis-trative does not mean full protection in all cases nor does it mean thelands are not already degraded This usage implies protection but notnecessarily functional habitat Second outside of the data analysis andconsistent with the vision presented in the article we use the termlsquoprotectedrsquo in a more general sense to imply land cover protectionfrom non-conservation related activities

Briefly GAP Status 1 lands includewilderness areaswith permanenthabitat protection that allows natural disturbance events to occur GAPStatus 2 lands have permanent habitat protection but may receive usesor management practices that degrade the quality of existing naturalcommunities including the suppression of natural disturbances GAPStatus 3 lands have permanent protection for federally listed endan-gered and threatened species although extractive uses are permittedon typically upland areas (eg logging mining and grazing) Many ofthese lands also have administrative policies to protect riparian landshowever the strength and status of this protection is highly variable(NRC 2002) GAP Status 3 lands represent a large portion of the publiclymanaged lands which are predominately managed by the US ForestService and US Bureau of Land Management (approximately 300million ha) (Aycrigg et al 2013) GAP Status 4 lands have nomandated conservation protection although conservation practicesmight occur (eg Department of Defense State Land Board Bureau ofIndian Affairs) For the purpose of this analysis all lands with noassigned GAP Status code were designated GAP Status 4 lands Conser-vation easements were also designated as Status 4 because they havean unknown conservation-management mandate

The NCED database is a continuously updated spatial databaseof conservation easement lands in the US compiled from land trustand public agency records (NCED accessed June 2012) NCED includesapproximately 162 million ha of privately owned conservationeasement lands Prior to conducting our analysis we eliminatedduplicate data between NCED and PAD-US

The NHDplus database includes streamlines for the US digitizedfrom aerial photos and USGS quadrangles at a scale of 1100000(NHDplus version 2) For a national analysis NHDplus provides thebest data available for representing the US stream network but it alsoincludes large irrigation ditches and other human-made waterways Itis important to highlight that our unit of analysis is the streamline andnot the riparian corridor Currently there is no national inventory ofriparian areas Additionally we recognize that riparian areas withinthe US vary significantly in habitat quality While finer-grained analysismight be possible this level of detail is beyond the scope of our nationalscale analysis

We summarized protection by Strahler Stream Order Stream orderis a measure of the stream size and is a hydrographic metric for indicat-ing the position of a specific stream segment within a watershedStrahler stream order defines the smallest tributaries as order 1 and in-creases as streams join to a value of 10 at the seaward ends of the largestrivers As an example the last segment of the Mississippi River is a 10thorder stream Headwater (mainly first and second order) streamscomprise up to 80 of the stream network by linear measurement Inaddition NHDplus delineates watersheds of varying sizes from topo-graphic data to define Hydrologic Unit Codes (HUCs) Regions (ie 8-digit HUCs) are the largest delineations and are defined topographicallyfor the largest terminal watersheds Small terminal watersheds (10- or12-digit HUCs) are clustered within regions but by definition are nothydrologically connected

22 Data analysis

221 Protected areas connected through a stream networkFor our analysis we defined protected areas both state and federal

as those landswith aGAP Status of 1 and 2 additionallywe includeGAPStatus 3 riparian lands because riparian areas have administrativeprotection in most cases (Table 1) We calculated the number ofprotected areas connected to at least one other protected area via thestream network We counted protected areas as connected when amapped river intersected the boundary of the protected areas Wefound that every protected area had at least one mapped river flowingthrough its bounding polygon while most areas had multiple connec-tions Any contiguous protected polygons with shared protected status1 and 2 or 3 were merged into a single unit we performed this opera-tion to better reflect how species would use an adjacent protectedparcel as a continuous habitat A protected area was considered lsquocon-nectedrsquo through the stream network if it was connected to at least oneother protected area within an 8-digit HUC Protected areas that arelocated in separate 8-digit HUCs (the largest watersheds) cannot beconnected through a riparian corridor as they exist in separatewatersheds

222 Percent protection of stream network by conservation status streamorder and HUC

Wedefine ldquopercent protectedrdquo as the percentage of linear rivermileslyingwithin either a protected area or aworking landscapewith admin-istrative riparian protection (eg GAP Status land 1ndash3) ldquoPercentprotectedrdquo is thus a proxy for the amount of an RCN that is alreadyimplemented We calculated the percentage of the current mappedstream network by GAP Status Code 1 2 or 3 by Strahler streamorder and by governing agency It is important to note that our estimateof riparian protection is in linear units (stream length) not areal unitsand that this will impact the estimate and any comparison withterrestrial measures of protection (Aycrigg et al 2013) In additionour decision to include GAP status 3 riparian lands as ldquoprotectedrdquo signif-icantly affects the percent protected lands In our analysis non-riparianGAP status 3 lands are not protected

For this analysis streamlines with no stream order demarcationwere not used in the analysis as they typically include streamlinesthrough lakes reservoirs or irrigation canals To calculate the percent

32 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

protected we assumed that if the stream centerline lies within aprotected area both sides of the streams riparian areas are protectedexcept when the stream defines the border of the protected area Weprocessed a 30-meter buffer inside the perimeter of each protectedarea to limit this edge effect We used these reduced polygons in ouranalysis to quantify the percentage of the total stream length protectedWe believe our estimate is accurate in terms of administrative protec-tion but also conservative in its extent In addition for publicly ownedland we calculated the percentage of the stream network managed byeach governmental agency

223 Proximity of conservation easements to riparian areasWehypothesized that conservation easements fromNCEDwould be

biased toward riparian areas To estimate this bias we used a distance-based analysis to capture those easements that might fall within ariparian area Specifically we calculated the Euclidean distance betweeneach conservation easement edge and the closest stream centerlineWeperformed this analysis initially with the entire NHDplus dataset thenonly for stream orders greater than 1 and again for stream orders great-er than 2 Excluding the lowest order streams which typically supportlittle or no adjacent riparian habitat should provide a more reasonableestimate of the association of easements with floodplain and ripariancorridors

3 Results

31 Protected areas are connected through a stream network

Ninety-five percent of all federally protected areas are connected bya stream network to at least one other protected area In many regionsmultiple connections exist between protected areas The few protectedareas without riparian connections are found in small basins directlydraining to the ocean or basins with terminal drains into deserts(eg eastern Sierra Nevada rivers flowing into Nevada)

32 Stream network protection varies by conservation status stream orderand HUC

The percentage of land along protected stream segments generallydecreases as stream order increases (Fig 1) The average protection ofthe stream network is 248 Streams classified as orders 1ndash3 make up80 of the overall network in general Although the general pattern of

Fig 1 Percent protection of stream network by groups of stream order Based on PAD-US and Nthe average protection is 248 The average is highly skewed because headwater streams (str

protection of streams decreases from smaller to larger streams(ie there is a bias in protection toward riparian areas in headwaterstreams as expected) the percent of protection for riparian areas inlarge streams does not drop below 15 with a range of 255ndash159 oflands with GAP Status codes 1ndash3 The average protection (248) iscloser to the highest protection (255) because the stream network iscomposed of 80 headwater streams As such riparian areas aroundheadwater streams generally have higher protection status than ripari-an areas associated with large rivers The explanation for this higherprotection is in part because of the amount of GAP Status 3 landsWe in-cluded these lands in the lsquoprotectedrsquo category because they typicallyhave administrative protection of riparian lands but not upland areas(Table 1) however it is important to note that upland land use canimpact riparian structure and function and there is high variability inthe strength of that protection and the ecological condition (NRC2000) Stream orders 1ndash3 have the highest percent of stream lengthprotected on GAP Status 3 lands particularly in the western US (Fig 2)

33 Conservation easements are often near to streams

Conservation on private lands through conservation easements mayhave a spatial bias toward riparian areas most notably around largerrivers (Fig 3) Of the 162 million ha of land in conservation easements57 are within 100 m of a stream channel and 93 are within 1 km ofthe stream centerline The proportion decreases when first and secondorder streams are removed (19 and 68 respectively) For examplethe pattern of easements and their distance to the Mississippi and RedRivers in the southern portion of the US indicates numerous easementswithin the floodplain (Fig 3) Conservation easements are clusteredgenerally around main river corridors

4 Discussion

Any conservation effort is only as good as its potential for implemen-tation through action at relevant ecological scales nomatter how clean-ly the proposed solutionmightmap in networked spaceWe argue that1) current policies broadly reflect societal concern for the protection ofriparian areas Our analysis suggests that an RCN is an emerging proper-ty of the streamnetwork and therefore a nascent backbone for the RCNmay already exist 2) scientific evidence supports the conservationvalue of an RCN to help mitigate the impacts of climate change and up-land habitat fragmentation and 3) although an RCNmay bemore easily

HDplus databases See Table 1 for descriptions of GAP status codes Over all stream orderseam orders 1ndash3) make up 80 of the total stream network by linear unit

Fig 2 Percent of stream length protectedwithin NHDplus 8-digit HUCwatersheds across the contiguous US Protection of stream and riparian areas in thewestern US is far greater than inthe Midwestern states and to a lesser degree the Eastern states Protection is defined as lands with GAP status codes 1ndash2 and conservation easements

33AK Fremier et al Biological Conservation 191 (2015) 29ndash37

implemented than other connectivity approaches from policy andmanagement standpoints conservation is better served if riparianconnectivity is part of a larger landscape connectivity strategy Ourvision is that the RCN would coordinate protection restoration andmanagement of riparian areas to build habitat connectivity amongexisting protected areas The primary value of this research is its con-ceptual and integrative approach Questions remain about the benefitsintegrity and management activities in riparian areas Howeverthe RCN provides context for future research and management onthese issues A research program to flesh out the RCN concept wouldnecessarily follow this conceptualization

The spatial distribution of conservation easements is additionalevidence of an emerging RCN Our analysis indicates that conservationeasements on private lands have a bias toward proximity to rivers(57 within 100 m and 93 within 1 km) Although the motivationfor establishing conservation easements varies the spatial pattern ofeasements suggests that protection of land close to rivers is important(Kline et al 2000 Ryan et al 2003) Although there are concernsthat conservation easements do not fully protect lands from non-conservation-related activities (Rissman et al 2007) conservationeasements nevertheless provide a mechanism for protection of ripariancorridors and could be tailored to meet that need The increasing inter-est in conservation easements by private landowners suggests themotivation to protect riparian lands exists (Mann et al 2013)

We acknowledge the potential limitations of re-building habitatparticularly in the face of complex topography rapid change inelevation or micro-climatic variation along the length of a corridornot to mention current condition of most riparian areas Many riparianareas will require restoration before they serve as functional corridors(Theobald et al 2010) and the buffer width to facilitate connectivityremains unclear particularly through human dominated areasAdditionally concerns about the potential undesirable side effects ofincreased connectivity exist (Simberloff et al 1992) but the existingnascent RCN could also serve as a research focus for assessing thevalidity of these concerns

41 A riparian conservation network is emerging

The geospatial patterns suggest that the backbone for an RCNis emerging through a combination of existing policy on publiclands and incentives for conservation easements on private lands(Figs 1ndash3) Although riparian lands are notmanaged as a formal systemstreams already have greater protection than upland areas Riparianareas are managed through various mechanisms including protectedlands management (eg wilderness parks and forests) measurestaken in response to the requirements of regulatory programs(eg the Clean Water Act (CWA) the Endangered Species Act (ESA)and the state-level implementation programs) and through incentive-based programs such as the USDAs Conservation Reserve Program(CRP) (NRC 2002)

We interpret this legal and administrative protection as strongevidence of the perceived importance of riparian area managementMoreover this level of protection (248) is more than double thelevel of protection of terrestrial areas (10 Aycrigg et al 2013) mainlybecause riparian areas have protection on public lands This elevatedprotection stems from the ecosystem services provided by riparianareas For example placement of lands in GAP Status 3 (national forestand BLM public lands) provides protection of riparian areas that mayassist in meeting water quality requirements (eg temperature pollut-ants) Administrative protection of course does not always mean func-tional protection and a great need remains for restoration of degradedriparian areas including in some areas a widening of protected riparianbuffers (Kondolf et al 1996) Nonetheless it is a beginning Further-more active tracking of the actual protection of riparian areasmay assistlandmanagers inmeeting area goals but certainlymore research is nec-essary to understand if administrative protection of riparian areas leadsto functional connectivity Our classification of GAP Status 3 lands asfunctional habitat denotes formal protection but is probably optimisticgiven degraded land and proximity to human activities

A viable RCN could build on the existing governance that supportssocietal interests in clean water and naturally functioning rivers

Fig 3 Riparian connectivity emerging from current policy The map shows the concentration of easements near or within the floodplain along the Mississippi and Red Rivers which col-lectively start to form a de facto corridor

34 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

governance that is nevertheless not currently coordinated for purposesof connectivity (Arthington et al 2010) Such mechanisms have beenput in place for a variety of services including water quality (CWA)single species protection (ESA) or soil conservation (CRP) The CWAhas already helped to restore and prevent degradation of many riparianareas to improve water quality through its direct controls on pollutersand restrictions on aquatic habitat destruction (Adler et al 2013)Nevertheless many waters across the United States remain impairedin part because of failure to integrate land use regulation with imple-mentation of federal laws such as the CWA and ESA (Cosens and Stow

2014) Mechanisms already have emerged to address the failure ofregulatory programs like the CWA and ESA such as incentive basedprograms like the USDA-CRP (NRC 2002)

The value of riparian protection for achieving habitat connectivityand the need to meet water quality standards may increase incentivesfor riparian protection from land conversion with minimal change inexisting law The CWA provides some incentives to develop an RCN asshown by the role it plays in driving riparian corridor protection(eg the US EPAs promotion of watershed-scale management andother state level efforts Section 404s restrictions on destruction and

35AK Fremier et al Biological Conservation 191 (2015) 29ndash37

adversemodification ofwetlands and other aquatic areas) For exampleto achieve temperature requirements of discharge permits under theCWA entities governing watersheds such as the Willamette River andthe Virginia regions of the Chesapeake Bay watershed have set uptrading programs in which a municipality pays for restoration ofshade in upstream riparian areas rather than the expensive alternativeof mechanical cooling

Implementation of the ESA has also encouraged riparian area protec-tion A high percentage of species listed for protection under the ESA areaquatic (Craig 2014) Compliance with both the CWA and ESA arefactors in developing habitat conservation plans (Native Fish HabitatConservation Plan) Similarly forestry programs at federal (NorthwestForest Plan) and state (Idaho Forestry Program Nez Perce Term SheetNez PercendashIdaho Water Rights Settlement) levels require buffer zonesalong riparian corridors in timber harvest areas The implementationof the ESA in the Pacific Northwest has placed the Federal EmergencyManagement Agency under pressure to change the National FloodInsurance Program (NFIP) by removing incentives to separate riversfrom their floodplains to allow insured development in the formerflood zone (see National Wildlife Federation v Federal EmergencyManagement Agency No C11ndash2044ndashRSM 2014 WL 5449859 WDWash Oct 24 2014)

In short CWA water quality standards ESA habitat requirementsand flood risk management goals may all be advanced by protectingsmall amounts of land in riparian corridors In addition to these regula-tory incentives planning approachesmdashincluding ESA Section 7 jeopardyassessments and the National Environmental Policy Act (NEPA)and its state counterparts the California Environmental Quality Act(CEQA)mdashcan allow for or even mandate coordination of ripariancorridor protection Other extant legal and policy protections includefinancial incentives to protect riparian lands such as incentive programsfor agriculture in the US Farm Bill (although these incentives werereduced in 2014) Another alternative is the purchase of private riparianlands by public entities or non-governmental organizations such as TheNature Conservancys water programs (Greenway program conserva-tion easements and other water programs Rollins Palmer 2008)

Other legal mechanisms associated with land management arealready playing a role in the emergence of riparian conservationparticularly across the federal public lands Notably 78 of publiclands are managed by four agenciesndashndashUSDA Forest Service US Bureauof LandManagement US National Park Service and US Fish andWildlifeServicemdashincreasing the potential for inter-agency coordination (Aycrigget al 2013) Additionally an RCN could enable a scalable policy withnested efforts to integrate currently independent and loosely coordinat-ed federal state tribal local and private actions

In addition riparian areas are pre-defined by the stream networkwhich simplifies the process of selecting corridor routes compared tospecies-specific terrestrial corridors (Hilty et al 2006) By simplifyingthe corridor selection procedure the RCN thus offers a simpler imple-mentation strategy Nonetheless although this simplicity is attractiveat conceptual and policy levels the effectiveness in improving connec-tivity and species survival through an RCN must be evaluated at thefield level For example the RCN cannot serve as a replacement corridorselection procedure in situations where species will not use riparianareas or the areasmight not have suitable riparian corridors In additionmore detailed local-scale analysis is needed to determine how andwhere local riparian corridors should be concentrated RCN researchalong these lines could dovetail with research already being completedsuch as the Riparian Climate-Corridors which incorporates mappedriparian areas and climate projections (Beier 2012 Krosby et al 2014)

42 A policy path to a riparian connectivity network

Although conceptually simple building connected corridors requirescoordination among governance agencies and private landownersThere currently is no federal policy mechanism for connecting

landscapes at any scale Although planning is underway for large-scalecorridors (ecoregions biomes) efforts lack sufficient generality fornational-scale application (Hilty et al 2006) Nevertheless there aremultiple examples of regional-scale cooperative restoration effortsthat may offer governance models for building connectivity TheChesapeake Bay region inMaryland andVirginia the Florida Evergladesand the Greater Yellowstone Ecosystem in Wyoming Montana andIdaho are regional examples of multiagency collaborative managementto maintain conservation integrity (Noss et al 2002) as are theWestern Governors Associations discussions of a migratory corridoror Washington States climate-change-related efforts to addressconnectivity In addition the Partners in FlightMigratory Bird Conserva-tion program specifically targets migratory species and has hadconservation-related successes throughout North America working atlarger scales (Carter et al 2000) This program functions at the regionalscale but is planned and coordinated through lsquojoint venturersquo partner-ships and management at international scale

Coordination at coarser scales can lead to protection at finer scalesFor example wetland and riparian areas play a key role in buildingconnectivity for migrating waterfowl in the North AmericanWaterfowlManagement Plan (Williams et al 1999) Many of these efforts toimprove habitat connectivity attempt to optimize the construction ofhabitat corridors between individual preserves focusing on specificspecies or small assemblages of species within the constraints of localgeographies and prioritizing riparian lands for restoration with theirspatial configuration in mind (Theobald et al 2012) However achallenge for implementing an RCN particularly in western states isthe complicated planning and implementation of the allocation ofwater through private water rights (Adler et al 2013)

Federal resource agencies have a checkered history of workingtogether toward a common purpose in part because each is governedby different legal requirements Yet the Landscape Conservation Coop-eratives (LCCs) in the US that began as the result of a Secretarial Orderfrom the Department of the Interior in 2009 (Order No 3289 Sept 142009) exemplify emergent coordination to solve issues that persist atlarger scales (Millard et al 2012) LCCs aim to provide scientificexpertise and coordination among public and private institutions at alandscape scale In addition implementation of the ESA has led to coor-dination across multiple agencies in examples such as the NorthwestForest Plan A more proactive coordinated approach to building land-scape habitat connectivity could be incorporated into the missions ofrelevant agencies (eg National Park Service US Fish and WildlifeService Bureau of LandManagement USDA Forest Service) Presidentialguidance through an Executive Order could be used to advance thedevelopment of a more comprehensive RCN In addition at least somestates seem to be willing to pursue similar efforts for state publiclands (Citron 2010) Conversations on such lsquotop-downrsquo options arealready underway in national policy circles (USFWS 2013) In additionfactors other than species conservation are already driving riparianprotection such as ecosystem services One clear example of agencycoordination to manage riparian areas for multiple benefits is the YoloBasin near Sacramento California (Opperman et al 2009) other suchsolution have been recently proposed (Greco and Larsen 2014) Thisarea supports multiple typically competing interests by managing ricefarming and wildlife conservation while allowing flood water storageduring critical times with the added benefit of migratory bird habitatThe multiple benefits of riparian protection illustrated in the YoloBasin example can broaden actual and potential sources of supportfor an RCN including efforts to improve aquatic ecosystem servicessuch as filtration riparian vegetation and floodplain connectivity thatimprove water quality bank stabilization and flood control as well asesthetics (Bernhardt et al 2005 Fremier et al 2013) Explicitly incor-porating ecosystem services into conservation corridor protectionmechanisms would open riparian protection efforts to a broader arrayof institutions and funding sources including agencies charged withprotecting water quality and reducing flood risks and private interest

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

Adler RW Craig RK Hall ND 2013 Modern Water Law Private Property PublicRights and Environmental Protections 1st ed Foundation Press

Arthington AH Naiman RJ McCLAIN ME Nilsson C 2010 Preserving the biodiversityand ecological services of rivers new challenges and research opportunities FreshwBiol 55 1ndash16 httpdxdoiorg101111j1365-2427200902340x

Aycrigg JL Davidson A Svancara LK Gergely KJ McKerrow A Scott JM 2013Representation of ecological systems within the protected areas network of theContinental United States PLoS One 8 e54689 httpdxdoiorg101371journalpone0054689

Baron JS Gunderson L Allen CD Fleishman E McKenzie D Meyerson LA OropezaJ Stephenson N 2009 Options for national parks and reserves for adapting toclimate change Environ Manag 44 1033ndash1042 httpdxdoiorg101007s00267-009-9296-6

Battin J 2004 When good animals love bad habitats ecological traps and the conserva-tion of animal populations Conserv Biol 18 1482ndash1491 httpdxdoiorg101111j1523-1739200400417x

Beier P 2012 Conceptualizing and designing corridors for climate change Ecol Restor312ndash319

Bengtsson J Angelstam P Elmqvist T Emanuelsson U Folke C Ihse M Moberg FNystrom M 2003 Reserves resilience and dynamic landscapes AMBIO A J HumEnviron 32 389ndash396 httpdxdoiorg1015790044-7447-326389

Bernhardt ES Palmer MA Allan JD Alexander G Barnas K Brooks S Carr JClayton S Dahm C Follstad-Shah J Galat D Gloss S Goodwin P Hart DHassett B Jenkinson R Katz S Kondolf GM Lake PS Lave R Meyer JLODonnell TK Pagano L Powell B Sudduth E 2005 Synthesizing US river resto-ration efforts Science 308 636ndash637 (80-)

Biggs R Schluumlter M Biggs D Bohensky EL BurnSilver S Cundill G Dakos V DawTM Evans LS Kotschy K Leitch AM Meek C Quinlan A Raudsepp-HearneC Robards MD Schoon ML Schultz L West P 2012 Toward principles for

enhancing the resilience of ecosystem services Annu Rev Environ Resour 37421ndash448 httpdxdoiorg101146annurev-environ-051211-123836

Brauman KA Daily GC Duarte TK Mooney HA 2007 The nature and value ofecosystem services an overview highlighting hydrologic services Annu RevEnviron Resour 32 67ndash98 (doihttpdxdoiorg101146annurevenergy32031306102758 U httparjournalsannualreviewsorgdoiabs101146annurevenergy32031306102758)

Brost BM Beier P 2012 Comparing linkage designs based on land facets to linkagedesigns based on focal species PLoS One 7 e48965 httpdxdoiorg101371journalpone0048965

Carter M Hunter W Pashley D Rosenberg K 2000 Setting conservation prioritiesfor landbirds in the United States the Partners in Flight approach Auk 117 541ndash548

Citron A 2010 Working rivers and working landscapes using short-term water useagreements to conserve Arizonas riparian and agricultural heritage ArizonaJ Environ Law Policy 1

Clevenger AP Waltho N 2000 Factors influencing the effectiveness of wildlifeunderpasses in Banff National Park Alberta Canada Conserv Biol 14 47ndash56httpdxdoiorg101046j1523-1739200000099-085x

Cosens B Stow C 2014 Resilience and water governance addressing fragmentationand uncertainty in water allocation and water quality law In Garmestani A AllenCR (Eds) Social-Ecological Resilience and Law Columbia University Press p 416

Craig RK 2014 Does the Endangered Species Act Preempt State Water LawCrimmins SM Dobrowski SZ Greenberg J a Abatzoglou JT Mynsberge AR

2011 Changes in climatic water balance drive downhill shifts in plant speciesoptimum elevations Science 331 324ndash327 httpdxdoiorg101126science1199040 (80-)

ElmoreW Beschta RL 1987 Riparian areas perceptions inmanagement Rangelands 9Elmqvist T Folke C Nystrom M Peterson G Bengtsson J Walker B Norberg J 2003

Response diversity ecosystem change and resilience Front Ecol Environ 1488ndash494 httpdxdoiorg1018901540-9295(2003)001[0488RDECAR]20CO2

Fremier AK Declerck FAJ Bosque-Peacuterez NA Carmona NE Hill R Joyal T Keesecker LKlos PZ Martiacutenez-Salinas A Niemeyer R Sanfiorenzo A Welsh K Wulfhorst JD2013 Understanding spatiotemporal lags in ecosystem services to improve incentivesBioscience 63 472ndash482 httpdxdoiorg101525bio20136369

Gilbert-Norton L Wilson R Stevens JR Beard KH 2010 A meta-analytic review ofcorridor effectiveness Conserv Biol 24 660ndash668 httpdxdoiorg101111j1523-1739201001450x

Goetz SJ Jantz P Jantz CA 2009 Connectivity of core habitat in the NortheasternUnited States parks and protected areas in a landscape context Remote SensEnviron 113 1421ndash1429 httpdxdoiorg101016jrse200807019

Goldman RL Tallis H 2009 A critical analysis of ecosystem services as a tool inconservation projects the possible perils the promises and the partnerships AnnN Y Acad Sci 1162 63ndash78 httpdxdoiorg101111j1749-6632200904151x

Greco SE Larsen EW 2014 Ecological design of multifunctional open channels forflood control and conservation planning Landsc Urban Plan 131 14ndash26 httpdxdoiorg101016jlandurbplan201407002

Griffith B Scott JM Adamcik R Ashe D Czech B Fischman R Gonzalez P Lawler JMcGuire AD Pidgorna A 2009 Climate change adaptation for the US NationalWildlife Refuge System Environ Manag 44 1043ndash1052 httpdxdoiorg101007s00267-009-9323-7

Haddad NM Brudvig La Damschen EI Evans DM Johnson BL Levey DJ OrrockJL Resasco J Sullivan LL Tewksbury JJ Wagner Sa Weldon AJ 2014 Potentialnegative ecological effects of corridors Conserv Biol 28 1178ndash1187 httpdxdoiorg101111cobi12323

Hannah L Midgley GF Lovejoy T BondWJ Bush M Lovett JC Scott DWoodwardFI 2002 Conservation of biodiversity in a changing climate Conserv Biol 16264ndash268 httpdxdoiorg101046j1523-1739200200465x

Hilty JA Merenlender AM 2004 Use of riparian corridors and vineyards by mammali-an predators in Northern California Conserv Biol 10 126ndash135

Hilty JA Lidicker WZ Merenlender AM 2006 Corridor Ecology The Science andPractice of Linking Landscapes for Biodiversity Conservation 1st ed Island PressWashington DC

Johnston A Ausden M Dodd AM Bradbury RB Chamberlain DE Jiguet F ThomasCD Cook ASCP Newson SE Ockendon N Rehfisch MM Roos S Thaxter CBBrown A Crick HQP Douse A McCall RA Pontier H Stroud DA Cadiou BCrowe O Deceuninck B Hornman M Pearce-Higgins JW 2013 Observed andpredicted effects of climate change on species abundance in protected areas NatClim Chang 3 1055ndash1061 httpdxdoiorg101038nclimate2035

Kline JD Alig RJ Johnson RL 2000 Forest owner incentives to protect riparian habitatEcol Econ 33 29ndash43 httpdxdoiorg101016S0921-8009(99)00116-0

Kondolf GM Kattelman R Embury M Erman D 1996 Status of riparian habitat SierraNevada Ecosystem Project Final Report to Congress Vol II Assessments andScientific Basis for Management Options University of California Centers for Waterand Wildland Resources Davis CA pp 1009ndash1030

Krosby M Norheim R Theobald D McRae BH 2014 Riparian Climate-CorridorsIdentifying Priority Areas for Conservation in a changing Climate

Lacey HB 1996 Dancing in place the Clinton Administration and aquatic ecosystemprotection in the Pacific Northwest Nat Resour J 36

Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

Millard MJ Czarnecki CA Morton JM Brandt LA Briggs JS Shipley FS Sayre RSponholtz PJ Perkins D Simpkins DG Taylor J 2012 A national geographic

32 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

protected we assumed that if the stream centerline lies within aprotected area both sides of the streams riparian areas are protectedexcept when the stream defines the border of the protected area Weprocessed a 30-meter buffer inside the perimeter of each protectedarea to limit this edge effect We used these reduced polygons in ouranalysis to quantify the percentage of the total stream length protectedWe believe our estimate is accurate in terms of administrative protec-tion but also conservative in its extent In addition for publicly ownedland we calculated the percentage of the stream network managed byeach governmental agency

223 Proximity of conservation easements to riparian areasWehypothesized that conservation easements fromNCEDwould be

biased toward riparian areas To estimate this bias we used a distance-based analysis to capture those easements that might fall within ariparian area Specifically we calculated the Euclidean distance betweeneach conservation easement edge and the closest stream centerlineWeperformed this analysis initially with the entire NHDplus dataset thenonly for stream orders greater than 1 and again for stream orders great-er than 2 Excluding the lowest order streams which typically supportlittle or no adjacent riparian habitat should provide a more reasonableestimate of the association of easements with floodplain and ripariancorridors

3 Results

31 Protected areas are connected through a stream network

Ninety-five percent of all federally protected areas are connected bya stream network to at least one other protected area In many regionsmultiple connections exist between protected areas The few protectedareas without riparian connections are found in small basins directlydraining to the ocean or basins with terminal drains into deserts(eg eastern Sierra Nevada rivers flowing into Nevada)

32 Stream network protection varies by conservation status stream orderand HUC

The percentage of land along protected stream segments generallydecreases as stream order increases (Fig 1) The average protection ofthe stream network is 248 Streams classified as orders 1ndash3 make up80 of the overall network in general Although the general pattern of

Fig 1 Percent protection of stream network by groups of stream order Based on PAD-US and Nthe average protection is 248 The average is highly skewed because headwater streams (str

protection of streams decreases from smaller to larger streams(ie there is a bias in protection toward riparian areas in headwaterstreams as expected) the percent of protection for riparian areas inlarge streams does not drop below 15 with a range of 255ndash159 oflands with GAP Status codes 1ndash3 The average protection (248) iscloser to the highest protection (255) because the stream network iscomposed of 80 headwater streams As such riparian areas aroundheadwater streams generally have higher protection status than ripari-an areas associated with large rivers The explanation for this higherprotection is in part because of the amount of GAP Status 3 landsWe in-cluded these lands in the lsquoprotectedrsquo category because they typicallyhave administrative protection of riparian lands but not upland areas(Table 1) however it is important to note that upland land use canimpact riparian structure and function and there is high variability inthe strength of that protection and the ecological condition (NRC2000) Stream orders 1ndash3 have the highest percent of stream lengthprotected on GAP Status 3 lands particularly in the western US (Fig 2)

33 Conservation easements are often near to streams

Conservation on private lands through conservation easements mayhave a spatial bias toward riparian areas most notably around largerrivers (Fig 3) Of the 162 million ha of land in conservation easements57 are within 100 m of a stream channel and 93 are within 1 km ofthe stream centerline The proportion decreases when first and secondorder streams are removed (19 and 68 respectively) For examplethe pattern of easements and their distance to the Mississippi and RedRivers in the southern portion of the US indicates numerous easementswithin the floodplain (Fig 3) Conservation easements are clusteredgenerally around main river corridors

4 Discussion

Any conservation effort is only as good as its potential for implemen-tation through action at relevant ecological scales nomatter how clean-ly the proposed solutionmightmap in networked spaceWe argue that1) current policies broadly reflect societal concern for the protection ofriparian areas Our analysis suggests that an RCN is an emerging proper-ty of the streamnetwork and therefore a nascent backbone for the RCNmay already exist 2) scientific evidence supports the conservationvalue of an RCN to help mitigate the impacts of climate change and up-land habitat fragmentation and 3) although an RCNmay bemore easily

HDplus databases See Table 1 for descriptions of GAP status codes Over all stream orderseam orders 1ndash3) make up 80 of the total stream network by linear unit

Fig 2 Percent of stream length protectedwithin NHDplus 8-digit HUCwatersheds across the contiguous US Protection of stream and riparian areas in thewestern US is far greater than inthe Midwestern states and to a lesser degree the Eastern states Protection is defined as lands with GAP status codes 1ndash2 and conservation easements

33AK Fremier et al Biological Conservation 191 (2015) 29ndash37

implemented than other connectivity approaches from policy andmanagement standpoints conservation is better served if riparianconnectivity is part of a larger landscape connectivity strategy Ourvision is that the RCN would coordinate protection restoration andmanagement of riparian areas to build habitat connectivity amongexisting protected areas The primary value of this research is its con-ceptual and integrative approach Questions remain about the benefitsintegrity and management activities in riparian areas Howeverthe RCN provides context for future research and management onthese issues A research program to flesh out the RCN concept wouldnecessarily follow this conceptualization

The spatial distribution of conservation easements is additionalevidence of an emerging RCN Our analysis indicates that conservationeasements on private lands have a bias toward proximity to rivers(57 within 100 m and 93 within 1 km) Although the motivationfor establishing conservation easements varies the spatial pattern ofeasements suggests that protection of land close to rivers is important(Kline et al 2000 Ryan et al 2003) Although there are concernsthat conservation easements do not fully protect lands from non-conservation-related activities (Rissman et al 2007) conservationeasements nevertheless provide a mechanism for protection of ripariancorridors and could be tailored to meet that need The increasing inter-est in conservation easements by private landowners suggests themotivation to protect riparian lands exists (Mann et al 2013)

We acknowledge the potential limitations of re-building habitatparticularly in the face of complex topography rapid change inelevation or micro-climatic variation along the length of a corridornot to mention current condition of most riparian areas Many riparianareas will require restoration before they serve as functional corridors(Theobald et al 2010) and the buffer width to facilitate connectivityremains unclear particularly through human dominated areasAdditionally concerns about the potential undesirable side effects ofincreased connectivity exist (Simberloff et al 1992) but the existingnascent RCN could also serve as a research focus for assessing thevalidity of these concerns

41 A riparian conservation network is emerging

The geospatial patterns suggest that the backbone for an RCNis emerging through a combination of existing policy on publiclands and incentives for conservation easements on private lands(Figs 1ndash3) Although riparian lands are notmanaged as a formal systemstreams already have greater protection than upland areas Riparianareas are managed through various mechanisms including protectedlands management (eg wilderness parks and forests) measurestaken in response to the requirements of regulatory programs(eg the Clean Water Act (CWA) the Endangered Species Act (ESA)and the state-level implementation programs) and through incentive-based programs such as the USDAs Conservation Reserve Program(CRP) (NRC 2002)

We interpret this legal and administrative protection as strongevidence of the perceived importance of riparian area managementMoreover this level of protection (248) is more than double thelevel of protection of terrestrial areas (10 Aycrigg et al 2013) mainlybecause riparian areas have protection on public lands This elevatedprotection stems from the ecosystem services provided by riparianareas For example placement of lands in GAP Status 3 (national forestand BLM public lands) provides protection of riparian areas that mayassist in meeting water quality requirements (eg temperature pollut-ants) Administrative protection of course does not always mean func-tional protection and a great need remains for restoration of degradedriparian areas including in some areas a widening of protected riparianbuffers (Kondolf et al 1996) Nonetheless it is a beginning Further-more active tracking of the actual protection of riparian areasmay assistlandmanagers inmeeting area goals but certainlymore research is nec-essary to understand if administrative protection of riparian areas leadsto functional connectivity Our classification of GAP Status 3 lands asfunctional habitat denotes formal protection but is probably optimisticgiven degraded land and proximity to human activities

A viable RCN could build on the existing governance that supportssocietal interests in clean water and naturally functioning rivers

Fig 3 Riparian connectivity emerging from current policy The map shows the concentration of easements near or within the floodplain along the Mississippi and Red Rivers which col-lectively start to form a de facto corridor

34 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

governance that is nevertheless not currently coordinated for purposesof connectivity (Arthington et al 2010) Such mechanisms have beenput in place for a variety of services including water quality (CWA)single species protection (ESA) or soil conservation (CRP) The CWAhas already helped to restore and prevent degradation of many riparianareas to improve water quality through its direct controls on pollutersand restrictions on aquatic habitat destruction (Adler et al 2013)Nevertheless many waters across the United States remain impairedin part because of failure to integrate land use regulation with imple-mentation of federal laws such as the CWA and ESA (Cosens and Stow

2014) Mechanisms already have emerged to address the failure ofregulatory programs like the CWA and ESA such as incentive basedprograms like the USDA-CRP (NRC 2002)

The value of riparian protection for achieving habitat connectivityand the need to meet water quality standards may increase incentivesfor riparian protection from land conversion with minimal change inexisting law The CWA provides some incentives to develop an RCN asshown by the role it plays in driving riparian corridor protection(eg the US EPAs promotion of watershed-scale management andother state level efforts Section 404s restrictions on destruction and

35AK Fremier et al Biological Conservation 191 (2015) 29ndash37

adversemodification ofwetlands and other aquatic areas) For exampleto achieve temperature requirements of discharge permits under theCWA entities governing watersheds such as the Willamette River andthe Virginia regions of the Chesapeake Bay watershed have set uptrading programs in which a municipality pays for restoration ofshade in upstream riparian areas rather than the expensive alternativeof mechanical cooling

Implementation of the ESA has also encouraged riparian area protec-tion A high percentage of species listed for protection under the ESA areaquatic (Craig 2014) Compliance with both the CWA and ESA arefactors in developing habitat conservation plans (Native Fish HabitatConservation Plan) Similarly forestry programs at federal (NorthwestForest Plan) and state (Idaho Forestry Program Nez Perce Term SheetNez PercendashIdaho Water Rights Settlement) levels require buffer zonesalong riparian corridors in timber harvest areas The implementationof the ESA in the Pacific Northwest has placed the Federal EmergencyManagement Agency under pressure to change the National FloodInsurance Program (NFIP) by removing incentives to separate riversfrom their floodplains to allow insured development in the formerflood zone (see National Wildlife Federation v Federal EmergencyManagement Agency No C11ndash2044ndashRSM 2014 WL 5449859 WDWash Oct 24 2014)

In short CWA water quality standards ESA habitat requirementsand flood risk management goals may all be advanced by protectingsmall amounts of land in riparian corridors In addition to these regula-tory incentives planning approachesmdashincluding ESA Section 7 jeopardyassessments and the National Environmental Policy Act (NEPA)and its state counterparts the California Environmental Quality Act(CEQA)mdashcan allow for or even mandate coordination of ripariancorridor protection Other extant legal and policy protections includefinancial incentives to protect riparian lands such as incentive programsfor agriculture in the US Farm Bill (although these incentives werereduced in 2014) Another alternative is the purchase of private riparianlands by public entities or non-governmental organizations such as TheNature Conservancys water programs (Greenway program conserva-tion easements and other water programs Rollins Palmer 2008)

Other legal mechanisms associated with land management arealready playing a role in the emergence of riparian conservationparticularly across the federal public lands Notably 78 of publiclands are managed by four agenciesndashndashUSDA Forest Service US Bureauof LandManagement US National Park Service and US Fish andWildlifeServicemdashincreasing the potential for inter-agency coordination (Aycrigget al 2013) Additionally an RCN could enable a scalable policy withnested efforts to integrate currently independent and loosely coordinat-ed federal state tribal local and private actions

In addition riparian areas are pre-defined by the stream networkwhich simplifies the process of selecting corridor routes compared tospecies-specific terrestrial corridors (Hilty et al 2006) By simplifyingthe corridor selection procedure the RCN thus offers a simpler imple-mentation strategy Nonetheless although this simplicity is attractiveat conceptual and policy levels the effectiveness in improving connec-tivity and species survival through an RCN must be evaluated at thefield level For example the RCN cannot serve as a replacement corridorselection procedure in situations where species will not use riparianareas or the areasmight not have suitable riparian corridors In additionmore detailed local-scale analysis is needed to determine how andwhere local riparian corridors should be concentrated RCN researchalong these lines could dovetail with research already being completedsuch as the Riparian Climate-Corridors which incorporates mappedriparian areas and climate projections (Beier 2012 Krosby et al 2014)

42 A policy path to a riparian connectivity network

Although conceptually simple building connected corridors requirescoordination among governance agencies and private landownersThere currently is no federal policy mechanism for connecting

landscapes at any scale Although planning is underway for large-scalecorridors (ecoregions biomes) efforts lack sufficient generality fornational-scale application (Hilty et al 2006) Nevertheless there aremultiple examples of regional-scale cooperative restoration effortsthat may offer governance models for building connectivity TheChesapeake Bay region inMaryland andVirginia the Florida Evergladesand the Greater Yellowstone Ecosystem in Wyoming Montana andIdaho are regional examples of multiagency collaborative managementto maintain conservation integrity (Noss et al 2002) as are theWestern Governors Associations discussions of a migratory corridoror Washington States climate-change-related efforts to addressconnectivity In addition the Partners in FlightMigratory Bird Conserva-tion program specifically targets migratory species and has hadconservation-related successes throughout North America working atlarger scales (Carter et al 2000) This program functions at the regionalscale but is planned and coordinated through lsquojoint venturersquo partner-ships and management at international scale

Coordination at coarser scales can lead to protection at finer scalesFor example wetland and riparian areas play a key role in buildingconnectivity for migrating waterfowl in the North AmericanWaterfowlManagement Plan (Williams et al 1999) Many of these efforts toimprove habitat connectivity attempt to optimize the construction ofhabitat corridors between individual preserves focusing on specificspecies or small assemblages of species within the constraints of localgeographies and prioritizing riparian lands for restoration with theirspatial configuration in mind (Theobald et al 2012) However achallenge for implementing an RCN particularly in western states isthe complicated planning and implementation of the allocation ofwater through private water rights (Adler et al 2013)

Federal resource agencies have a checkered history of workingtogether toward a common purpose in part because each is governedby different legal requirements Yet the Landscape Conservation Coop-eratives (LCCs) in the US that began as the result of a Secretarial Orderfrom the Department of the Interior in 2009 (Order No 3289 Sept 142009) exemplify emergent coordination to solve issues that persist atlarger scales (Millard et al 2012) LCCs aim to provide scientificexpertise and coordination among public and private institutions at alandscape scale In addition implementation of the ESA has led to coor-dination across multiple agencies in examples such as the NorthwestForest Plan A more proactive coordinated approach to building land-scape habitat connectivity could be incorporated into the missions ofrelevant agencies (eg National Park Service US Fish and WildlifeService Bureau of LandManagement USDA Forest Service) Presidentialguidance through an Executive Order could be used to advance thedevelopment of a more comprehensive RCN In addition at least somestates seem to be willing to pursue similar efforts for state publiclands (Citron 2010) Conversations on such lsquotop-downrsquo options arealready underway in national policy circles (USFWS 2013) In additionfactors other than species conservation are already driving riparianprotection such as ecosystem services One clear example of agencycoordination to manage riparian areas for multiple benefits is the YoloBasin near Sacramento California (Opperman et al 2009) other suchsolution have been recently proposed (Greco and Larsen 2014) Thisarea supports multiple typically competing interests by managing ricefarming and wildlife conservation while allowing flood water storageduring critical times with the added benefit of migratory bird habitatThe multiple benefits of riparian protection illustrated in the YoloBasin example can broaden actual and potential sources of supportfor an RCN including efforts to improve aquatic ecosystem servicessuch as filtration riparian vegetation and floodplain connectivity thatimprove water quality bank stabilization and flood control as well asesthetics (Bernhardt et al 2005 Fremier et al 2013) Explicitly incor-porating ecosystem services into conservation corridor protectionmechanisms would open riparian protection efforts to a broader arrayof institutions and funding sources including agencies charged withprotecting water quality and reducing flood risks and private interest

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

Adler RW Craig RK Hall ND 2013 Modern Water Law Private Property PublicRights and Environmental Protections 1st ed Foundation Press

Arthington AH Naiman RJ McCLAIN ME Nilsson C 2010 Preserving the biodiversityand ecological services of rivers new challenges and research opportunities FreshwBiol 55 1ndash16 httpdxdoiorg101111j1365-2427200902340x

Aycrigg JL Davidson A Svancara LK Gergely KJ McKerrow A Scott JM 2013Representation of ecological systems within the protected areas network of theContinental United States PLoS One 8 e54689 httpdxdoiorg101371journalpone0054689

Baron JS Gunderson L Allen CD Fleishman E McKenzie D Meyerson LA OropezaJ Stephenson N 2009 Options for national parks and reserves for adapting toclimate change Environ Manag 44 1033ndash1042 httpdxdoiorg101007s00267-009-9296-6

Battin J 2004 When good animals love bad habitats ecological traps and the conserva-tion of animal populations Conserv Biol 18 1482ndash1491 httpdxdoiorg101111j1523-1739200400417x

Beier P 2012 Conceptualizing and designing corridors for climate change Ecol Restor312ndash319

Bengtsson J Angelstam P Elmqvist T Emanuelsson U Folke C Ihse M Moberg FNystrom M 2003 Reserves resilience and dynamic landscapes AMBIO A J HumEnviron 32 389ndash396 httpdxdoiorg1015790044-7447-326389

Bernhardt ES Palmer MA Allan JD Alexander G Barnas K Brooks S Carr JClayton S Dahm C Follstad-Shah J Galat D Gloss S Goodwin P Hart DHassett B Jenkinson R Katz S Kondolf GM Lake PS Lave R Meyer JLODonnell TK Pagano L Powell B Sudduth E 2005 Synthesizing US river resto-ration efforts Science 308 636ndash637 (80-)

Biggs R Schluumlter M Biggs D Bohensky EL BurnSilver S Cundill G Dakos V DawTM Evans LS Kotschy K Leitch AM Meek C Quinlan A Raudsepp-HearneC Robards MD Schoon ML Schultz L West P 2012 Toward principles for

enhancing the resilience of ecosystem services Annu Rev Environ Resour 37421ndash448 httpdxdoiorg101146annurev-environ-051211-123836

Brauman KA Daily GC Duarte TK Mooney HA 2007 The nature and value ofecosystem services an overview highlighting hydrologic services Annu RevEnviron Resour 32 67ndash98 (doihttpdxdoiorg101146annurevenergy32031306102758 U httparjournalsannualreviewsorgdoiabs101146annurevenergy32031306102758)

Brost BM Beier P 2012 Comparing linkage designs based on land facets to linkagedesigns based on focal species PLoS One 7 e48965 httpdxdoiorg101371journalpone0048965

Carter M Hunter W Pashley D Rosenberg K 2000 Setting conservation prioritiesfor landbirds in the United States the Partners in Flight approach Auk 117 541ndash548

Citron A 2010 Working rivers and working landscapes using short-term water useagreements to conserve Arizonas riparian and agricultural heritage ArizonaJ Environ Law Policy 1

Clevenger AP Waltho N 2000 Factors influencing the effectiveness of wildlifeunderpasses in Banff National Park Alberta Canada Conserv Biol 14 47ndash56httpdxdoiorg101046j1523-1739200000099-085x

Cosens B Stow C 2014 Resilience and water governance addressing fragmentationand uncertainty in water allocation and water quality law In Garmestani A AllenCR (Eds) Social-Ecological Resilience and Law Columbia University Press p 416

Craig RK 2014 Does the Endangered Species Act Preempt State Water LawCrimmins SM Dobrowski SZ Greenberg J a Abatzoglou JT Mynsberge AR

2011 Changes in climatic water balance drive downhill shifts in plant speciesoptimum elevations Science 331 324ndash327 httpdxdoiorg101126science1199040 (80-)

ElmoreW Beschta RL 1987 Riparian areas perceptions inmanagement Rangelands 9Elmqvist T Folke C Nystrom M Peterson G Bengtsson J Walker B Norberg J 2003

Response diversity ecosystem change and resilience Front Ecol Environ 1488ndash494 httpdxdoiorg1018901540-9295(2003)001[0488RDECAR]20CO2

Fremier AK Declerck FAJ Bosque-Peacuterez NA Carmona NE Hill R Joyal T Keesecker LKlos PZ Martiacutenez-Salinas A Niemeyer R Sanfiorenzo A Welsh K Wulfhorst JD2013 Understanding spatiotemporal lags in ecosystem services to improve incentivesBioscience 63 472ndash482 httpdxdoiorg101525bio20136369

Gilbert-Norton L Wilson R Stevens JR Beard KH 2010 A meta-analytic review ofcorridor effectiveness Conserv Biol 24 660ndash668 httpdxdoiorg101111j1523-1739201001450x

Goetz SJ Jantz P Jantz CA 2009 Connectivity of core habitat in the NortheasternUnited States parks and protected areas in a landscape context Remote SensEnviron 113 1421ndash1429 httpdxdoiorg101016jrse200807019

Goldman RL Tallis H 2009 A critical analysis of ecosystem services as a tool inconservation projects the possible perils the promises and the partnerships AnnN Y Acad Sci 1162 63ndash78 httpdxdoiorg101111j1749-6632200904151x

Greco SE Larsen EW 2014 Ecological design of multifunctional open channels forflood control and conservation planning Landsc Urban Plan 131 14ndash26 httpdxdoiorg101016jlandurbplan201407002

Griffith B Scott JM Adamcik R Ashe D Czech B Fischman R Gonzalez P Lawler JMcGuire AD Pidgorna A 2009 Climate change adaptation for the US NationalWildlife Refuge System Environ Manag 44 1043ndash1052 httpdxdoiorg101007s00267-009-9323-7

Haddad NM Brudvig La Damschen EI Evans DM Johnson BL Levey DJ OrrockJL Resasco J Sullivan LL Tewksbury JJ Wagner Sa Weldon AJ 2014 Potentialnegative ecological effects of corridors Conserv Biol 28 1178ndash1187 httpdxdoiorg101111cobi12323

Hannah L Midgley GF Lovejoy T BondWJ Bush M Lovett JC Scott DWoodwardFI 2002 Conservation of biodiversity in a changing climate Conserv Biol 16264ndash268 httpdxdoiorg101046j1523-1739200200465x

Hilty JA Merenlender AM 2004 Use of riparian corridors and vineyards by mammali-an predators in Northern California Conserv Biol 10 126ndash135

Hilty JA Lidicker WZ Merenlender AM 2006 Corridor Ecology The Science andPractice of Linking Landscapes for Biodiversity Conservation 1st ed Island PressWashington DC

Johnston A Ausden M Dodd AM Bradbury RB Chamberlain DE Jiguet F ThomasCD Cook ASCP Newson SE Ockendon N Rehfisch MM Roos S Thaxter CBBrown A Crick HQP Douse A McCall RA Pontier H Stroud DA Cadiou BCrowe O Deceuninck B Hornman M Pearce-Higgins JW 2013 Observed andpredicted effects of climate change on species abundance in protected areas NatClim Chang 3 1055ndash1061 httpdxdoiorg101038nclimate2035

Kline JD Alig RJ Johnson RL 2000 Forest owner incentives to protect riparian habitatEcol Econ 33 29ndash43 httpdxdoiorg101016S0921-8009(99)00116-0

Kondolf GM Kattelman R Embury M Erman D 1996 Status of riparian habitat SierraNevada Ecosystem Project Final Report to Congress Vol II Assessments andScientific Basis for Management Options University of California Centers for Waterand Wildland Resources Davis CA pp 1009ndash1030

Krosby M Norheim R Theobald D McRae BH 2014 Riparian Climate-CorridorsIdentifying Priority Areas for Conservation in a changing Climate

Lacey HB 1996 Dancing in place the Clinton Administration and aquatic ecosystemprotection in the Pacific Northwest Nat Resour J 36

Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

Millard MJ Czarnecki CA Morton JM Brandt LA Briggs JS Shipley FS Sayre RSponholtz PJ Perkins D Simpkins DG Taylor J 2012 A national geographic

Fig 2 Percent of stream length protectedwithin NHDplus 8-digit HUCwatersheds across the contiguous US Protection of stream and riparian areas in thewestern US is far greater than inthe Midwestern states and to a lesser degree the Eastern states Protection is defined as lands with GAP status codes 1ndash2 and conservation easements

33AK Fremier et al Biological Conservation 191 (2015) 29ndash37

implemented than other connectivity approaches from policy andmanagement standpoints conservation is better served if riparianconnectivity is part of a larger landscape connectivity strategy Ourvision is that the RCN would coordinate protection restoration andmanagement of riparian areas to build habitat connectivity amongexisting protected areas The primary value of this research is its con-ceptual and integrative approach Questions remain about the benefitsintegrity and management activities in riparian areas Howeverthe RCN provides context for future research and management onthese issues A research program to flesh out the RCN concept wouldnecessarily follow this conceptualization

The spatial distribution of conservation easements is additionalevidence of an emerging RCN Our analysis indicates that conservationeasements on private lands have a bias toward proximity to rivers(57 within 100 m and 93 within 1 km) Although the motivationfor establishing conservation easements varies the spatial pattern ofeasements suggests that protection of land close to rivers is important(Kline et al 2000 Ryan et al 2003) Although there are concernsthat conservation easements do not fully protect lands from non-conservation-related activities (Rissman et al 2007) conservationeasements nevertheless provide a mechanism for protection of ripariancorridors and could be tailored to meet that need The increasing inter-est in conservation easements by private landowners suggests themotivation to protect riparian lands exists (Mann et al 2013)

We acknowledge the potential limitations of re-building habitatparticularly in the face of complex topography rapid change inelevation or micro-climatic variation along the length of a corridornot to mention current condition of most riparian areas Many riparianareas will require restoration before they serve as functional corridors(Theobald et al 2010) and the buffer width to facilitate connectivityremains unclear particularly through human dominated areasAdditionally concerns about the potential undesirable side effects ofincreased connectivity exist (Simberloff et al 1992) but the existingnascent RCN could also serve as a research focus for assessing thevalidity of these concerns

41 A riparian conservation network is emerging

The geospatial patterns suggest that the backbone for an RCNis emerging through a combination of existing policy on publiclands and incentives for conservation easements on private lands(Figs 1ndash3) Although riparian lands are notmanaged as a formal systemstreams already have greater protection than upland areas Riparianareas are managed through various mechanisms including protectedlands management (eg wilderness parks and forests) measurestaken in response to the requirements of regulatory programs(eg the Clean Water Act (CWA) the Endangered Species Act (ESA)and the state-level implementation programs) and through incentive-based programs such as the USDAs Conservation Reserve Program(CRP) (NRC 2002)

We interpret this legal and administrative protection as strongevidence of the perceived importance of riparian area managementMoreover this level of protection (248) is more than double thelevel of protection of terrestrial areas (10 Aycrigg et al 2013) mainlybecause riparian areas have protection on public lands This elevatedprotection stems from the ecosystem services provided by riparianareas For example placement of lands in GAP Status 3 (national forestand BLM public lands) provides protection of riparian areas that mayassist in meeting water quality requirements (eg temperature pollut-ants) Administrative protection of course does not always mean func-tional protection and a great need remains for restoration of degradedriparian areas including in some areas a widening of protected riparianbuffers (Kondolf et al 1996) Nonetheless it is a beginning Further-more active tracking of the actual protection of riparian areasmay assistlandmanagers inmeeting area goals but certainlymore research is nec-essary to understand if administrative protection of riparian areas leadsto functional connectivity Our classification of GAP Status 3 lands asfunctional habitat denotes formal protection but is probably optimisticgiven degraded land and proximity to human activities

A viable RCN could build on the existing governance that supportssocietal interests in clean water and naturally functioning rivers

Fig 3 Riparian connectivity emerging from current policy The map shows the concentration of easements near or within the floodplain along the Mississippi and Red Rivers which col-lectively start to form a de facto corridor

34 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

governance that is nevertheless not currently coordinated for purposesof connectivity (Arthington et al 2010) Such mechanisms have beenput in place for a variety of services including water quality (CWA)single species protection (ESA) or soil conservation (CRP) The CWAhas already helped to restore and prevent degradation of many riparianareas to improve water quality through its direct controls on pollutersand restrictions on aquatic habitat destruction (Adler et al 2013)Nevertheless many waters across the United States remain impairedin part because of failure to integrate land use regulation with imple-mentation of federal laws such as the CWA and ESA (Cosens and Stow

2014) Mechanisms already have emerged to address the failure ofregulatory programs like the CWA and ESA such as incentive basedprograms like the USDA-CRP (NRC 2002)

The value of riparian protection for achieving habitat connectivityand the need to meet water quality standards may increase incentivesfor riparian protection from land conversion with minimal change inexisting law The CWA provides some incentives to develop an RCN asshown by the role it plays in driving riparian corridor protection(eg the US EPAs promotion of watershed-scale management andother state level efforts Section 404s restrictions on destruction and

35AK Fremier et al Biological Conservation 191 (2015) 29ndash37

adversemodification ofwetlands and other aquatic areas) For exampleto achieve temperature requirements of discharge permits under theCWA entities governing watersheds such as the Willamette River andthe Virginia regions of the Chesapeake Bay watershed have set uptrading programs in which a municipality pays for restoration ofshade in upstream riparian areas rather than the expensive alternativeof mechanical cooling

Implementation of the ESA has also encouraged riparian area protec-tion A high percentage of species listed for protection under the ESA areaquatic (Craig 2014) Compliance with both the CWA and ESA arefactors in developing habitat conservation plans (Native Fish HabitatConservation Plan) Similarly forestry programs at federal (NorthwestForest Plan) and state (Idaho Forestry Program Nez Perce Term SheetNez PercendashIdaho Water Rights Settlement) levels require buffer zonesalong riparian corridors in timber harvest areas The implementationof the ESA in the Pacific Northwest has placed the Federal EmergencyManagement Agency under pressure to change the National FloodInsurance Program (NFIP) by removing incentives to separate riversfrom their floodplains to allow insured development in the formerflood zone (see National Wildlife Federation v Federal EmergencyManagement Agency No C11ndash2044ndashRSM 2014 WL 5449859 WDWash Oct 24 2014)

In short CWA water quality standards ESA habitat requirementsand flood risk management goals may all be advanced by protectingsmall amounts of land in riparian corridors In addition to these regula-tory incentives planning approachesmdashincluding ESA Section 7 jeopardyassessments and the National Environmental Policy Act (NEPA)and its state counterparts the California Environmental Quality Act(CEQA)mdashcan allow for or even mandate coordination of ripariancorridor protection Other extant legal and policy protections includefinancial incentives to protect riparian lands such as incentive programsfor agriculture in the US Farm Bill (although these incentives werereduced in 2014) Another alternative is the purchase of private riparianlands by public entities or non-governmental organizations such as TheNature Conservancys water programs (Greenway program conserva-tion easements and other water programs Rollins Palmer 2008)

Other legal mechanisms associated with land management arealready playing a role in the emergence of riparian conservationparticularly across the federal public lands Notably 78 of publiclands are managed by four agenciesndashndashUSDA Forest Service US Bureauof LandManagement US National Park Service and US Fish andWildlifeServicemdashincreasing the potential for inter-agency coordination (Aycrigget al 2013) Additionally an RCN could enable a scalable policy withnested efforts to integrate currently independent and loosely coordinat-ed federal state tribal local and private actions

In addition riparian areas are pre-defined by the stream networkwhich simplifies the process of selecting corridor routes compared tospecies-specific terrestrial corridors (Hilty et al 2006) By simplifyingthe corridor selection procedure the RCN thus offers a simpler imple-mentation strategy Nonetheless although this simplicity is attractiveat conceptual and policy levels the effectiveness in improving connec-tivity and species survival through an RCN must be evaluated at thefield level For example the RCN cannot serve as a replacement corridorselection procedure in situations where species will not use riparianareas or the areasmight not have suitable riparian corridors In additionmore detailed local-scale analysis is needed to determine how andwhere local riparian corridors should be concentrated RCN researchalong these lines could dovetail with research already being completedsuch as the Riparian Climate-Corridors which incorporates mappedriparian areas and climate projections (Beier 2012 Krosby et al 2014)

42 A policy path to a riparian connectivity network

Although conceptually simple building connected corridors requirescoordination among governance agencies and private landownersThere currently is no federal policy mechanism for connecting

landscapes at any scale Although planning is underway for large-scalecorridors (ecoregions biomes) efforts lack sufficient generality fornational-scale application (Hilty et al 2006) Nevertheless there aremultiple examples of regional-scale cooperative restoration effortsthat may offer governance models for building connectivity TheChesapeake Bay region inMaryland andVirginia the Florida Evergladesand the Greater Yellowstone Ecosystem in Wyoming Montana andIdaho are regional examples of multiagency collaborative managementto maintain conservation integrity (Noss et al 2002) as are theWestern Governors Associations discussions of a migratory corridoror Washington States climate-change-related efforts to addressconnectivity In addition the Partners in FlightMigratory Bird Conserva-tion program specifically targets migratory species and has hadconservation-related successes throughout North America working atlarger scales (Carter et al 2000) This program functions at the regionalscale but is planned and coordinated through lsquojoint venturersquo partner-ships and management at international scale

Coordination at coarser scales can lead to protection at finer scalesFor example wetland and riparian areas play a key role in buildingconnectivity for migrating waterfowl in the North AmericanWaterfowlManagement Plan (Williams et al 1999) Many of these efforts toimprove habitat connectivity attempt to optimize the construction ofhabitat corridors between individual preserves focusing on specificspecies or small assemblages of species within the constraints of localgeographies and prioritizing riparian lands for restoration with theirspatial configuration in mind (Theobald et al 2012) However achallenge for implementing an RCN particularly in western states isthe complicated planning and implementation of the allocation ofwater through private water rights (Adler et al 2013)

Federal resource agencies have a checkered history of workingtogether toward a common purpose in part because each is governedby different legal requirements Yet the Landscape Conservation Coop-eratives (LCCs) in the US that began as the result of a Secretarial Orderfrom the Department of the Interior in 2009 (Order No 3289 Sept 142009) exemplify emergent coordination to solve issues that persist atlarger scales (Millard et al 2012) LCCs aim to provide scientificexpertise and coordination among public and private institutions at alandscape scale In addition implementation of the ESA has led to coor-dination across multiple agencies in examples such as the NorthwestForest Plan A more proactive coordinated approach to building land-scape habitat connectivity could be incorporated into the missions ofrelevant agencies (eg National Park Service US Fish and WildlifeService Bureau of LandManagement USDA Forest Service) Presidentialguidance through an Executive Order could be used to advance thedevelopment of a more comprehensive RCN In addition at least somestates seem to be willing to pursue similar efforts for state publiclands (Citron 2010) Conversations on such lsquotop-downrsquo options arealready underway in national policy circles (USFWS 2013) In additionfactors other than species conservation are already driving riparianprotection such as ecosystem services One clear example of agencycoordination to manage riparian areas for multiple benefits is the YoloBasin near Sacramento California (Opperman et al 2009) other suchsolution have been recently proposed (Greco and Larsen 2014) Thisarea supports multiple typically competing interests by managing ricefarming and wildlife conservation while allowing flood water storageduring critical times with the added benefit of migratory bird habitatThe multiple benefits of riparian protection illustrated in the YoloBasin example can broaden actual and potential sources of supportfor an RCN including efforts to improve aquatic ecosystem servicessuch as filtration riparian vegetation and floodplain connectivity thatimprove water quality bank stabilization and flood control as well asesthetics (Bernhardt et al 2005 Fremier et al 2013) Explicitly incor-porating ecosystem services into conservation corridor protectionmechanisms would open riparian protection efforts to a broader arrayof institutions and funding sources including agencies charged withprotecting water quality and reducing flood risks and private interest

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

Adler RW Craig RK Hall ND 2013 Modern Water Law Private Property PublicRights and Environmental Protections 1st ed Foundation Press

Arthington AH Naiman RJ McCLAIN ME Nilsson C 2010 Preserving the biodiversityand ecological services of rivers new challenges and research opportunities FreshwBiol 55 1ndash16 httpdxdoiorg101111j1365-2427200902340x

Aycrigg JL Davidson A Svancara LK Gergely KJ McKerrow A Scott JM 2013Representation of ecological systems within the protected areas network of theContinental United States PLoS One 8 e54689 httpdxdoiorg101371journalpone0054689

Baron JS Gunderson L Allen CD Fleishman E McKenzie D Meyerson LA OropezaJ Stephenson N 2009 Options for national parks and reserves for adapting toclimate change Environ Manag 44 1033ndash1042 httpdxdoiorg101007s00267-009-9296-6

Battin J 2004 When good animals love bad habitats ecological traps and the conserva-tion of animal populations Conserv Biol 18 1482ndash1491 httpdxdoiorg101111j1523-1739200400417x

Beier P 2012 Conceptualizing and designing corridors for climate change Ecol Restor312ndash319

Bengtsson J Angelstam P Elmqvist T Emanuelsson U Folke C Ihse M Moberg FNystrom M 2003 Reserves resilience and dynamic landscapes AMBIO A J HumEnviron 32 389ndash396 httpdxdoiorg1015790044-7447-326389

Bernhardt ES Palmer MA Allan JD Alexander G Barnas K Brooks S Carr JClayton S Dahm C Follstad-Shah J Galat D Gloss S Goodwin P Hart DHassett B Jenkinson R Katz S Kondolf GM Lake PS Lave R Meyer JLODonnell TK Pagano L Powell B Sudduth E 2005 Synthesizing US river resto-ration efforts Science 308 636ndash637 (80-)

Biggs R Schluumlter M Biggs D Bohensky EL BurnSilver S Cundill G Dakos V DawTM Evans LS Kotschy K Leitch AM Meek C Quinlan A Raudsepp-HearneC Robards MD Schoon ML Schultz L West P 2012 Toward principles for

enhancing the resilience of ecosystem services Annu Rev Environ Resour 37421ndash448 httpdxdoiorg101146annurev-environ-051211-123836

Brauman KA Daily GC Duarte TK Mooney HA 2007 The nature and value ofecosystem services an overview highlighting hydrologic services Annu RevEnviron Resour 32 67ndash98 (doihttpdxdoiorg101146annurevenergy32031306102758 U httparjournalsannualreviewsorgdoiabs101146annurevenergy32031306102758)

Brost BM Beier P 2012 Comparing linkage designs based on land facets to linkagedesigns based on focal species PLoS One 7 e48965 httpdxdoiorg101371journalpone0048965

Carter M Hunter W Pashley D Rosenberg K 2000 Setting conservation prioritiesfor landbirds in the United States the Partners in Flight approach Auk 117 541ndash548

Citron A 2010 Working rivers and working landscapes using short-term water useagreements to conserve Arizonas riparian and agricultural heritage ArizonaJ Environ Law Policy 1

Clevenger AP Waltho N 2000 Factors influencing the effectiveness of wildlifeunderpasses in Banff National Park Alberta Canada Conserv Biol 14 47ndash56httpdxdoiorg101046j1523-1739200000099-085x

Cosens B Stow C 2014 Resilience and water governance addressing fragmentationand uncertainty in water allocation and water quality law In Garmestani A AllenCR (Eds) Social-Ecological Resilience and Law Columbia University Press p 416

Craig RK 2014 Does the Endangered Species Act Preempt State Water LawCrimmins SM Dobrowski SZ Greenberg J a Abatzoglou JT Mynsberge AR

2011 Changes in climatic water balance drive downhill shifts in plant speciesoptimum elevations Science 331 324ndash327 httpdxdoiorg101126science1199040 (80-)

ElmoreW Beschta RL 1987 Riparian areas perceptions inmanagement Rangelands 9Elmqvist T Folke C Nystrom M Peterson G Bengtsson J Walker B Norberg J 2003

Response diversity ecosystem change and resilience Front Ecol Environ 1488ndash494 httpdxdoiorg1018901540-9295(2003)001[0488RDECAR]20CO2

Fremier AK Declerck FAJ Bosque-Peacuterez NA Carmona NE Hill R Joyal T Keesecker LKlos PZ Martiacutenez-Salinas A Niemeyer R Sanfiorenzo A Welsh K Wulfhorst JD2013 Understanding spatiotemporal lags in ecosystem services to improve incentivesBioscience 63 472ndash482 httpdxdoiorg101525bio20136369

Gilbert-Norton L Wilson R Stevens JR Beard KH 2010 A meta-analytic review ofcorridor effectiveness Conserv Biol 24 660ndash668 httpdxdoiorg101111j1523-1739201001450x

Goetz SJ Jantz P Jantz CA 2009 Connectivity of core habitat in the NortheasternUnited States parks and protected areas in a landscape context Remote SensEnviron 113 1421ndash1429 httpdxdoiorg101016jrse200807019

Goldman RL Tallis H 2009 A critical analysis of ecosystem services as a tool inconservation projects the possible perils the promises and the partnerships AnnN Y Acad Sci 1162 63ndash78 httpdxdoiorg101111j1749-6632200904151x

Greco SE Larsen EW 2014 Ecological design of multifunctional open channels forflood control and conservation planning Landsc Urban Plan 131 14ndash26 httpdxdoiorg101016jlandurbplan201407002

Griffith B Scott JM Adamcik R Ashe D Czech B Fischman R Gonzalez P Lawler JMcGuire AD Pidgorna A 2009 Climate change adaptation for the US NationalWildlife Refuge System Environ Manag 44 1043ndash1052 httpdxdoiorg101007s00267-009-9323-7

Haddad NM Brudvig La Damschen EI Evans DM Johnson BL Levey DJ OrrockJL Resasco J Sullivan LL Tewksbury JJ Wagner Sa Weldon AJ 2014 Potentialnegative ecological effects of corridors Conserv Biol 28 1178ndash1187 httpdxdoiorg101111cobi12323

Hannah L Midgley GF Lovejoy T BondWJ Bush M Lovett JC Scott DWoodwardFI 2002 Conservation of biodiversity in a changing climate Conserv Biol 16264ndash268 httpdxdoiorg101046j1523-1739200200465x

Hilty JA Merenlender AM 2004 Use of riparian corridors and vineyards by mammali-an predators in Northern California Conserv Biol 10 126ndash135

Hilty JA Lidicker WZ Merenlender AM 2006 Corridor Ecology The Science andPractice of Linking Landscapes for Biodiversity Conservation 1st ed Island PressWashington DC

Johnston A Ausden M Dodd AM Bradbury RB Chamberlain DE Jiguet F ThomasCD Cook ASCP Newson SE Ockendon N Rehfisch MM Roos S Thaxter CBBrown A Crick HQP Douse A McCall RA Pontier H Stroud DA Cadiou BCrowe O Deceuninck B Hornman M Pearce-Higgins JW 2013 Observed andpredicted effects of climate change on species abundance in protected areas NatClim Chang 3 1055ndash1061 httpdxdoiorg101038nclimate2035

Kline JD Alig RJ Johnson RL 2000 Forest owner incentives to protect riparian habitatEcol Econ 33 29ndash43 httpdxdoiorg101016S0921-8009(99)00116-0

Kondolf GM Kattelman R Embury M Erman D 1996 Status of riparian habitat SierraNevada Ecosystem Project Final Report to Congress Vol II Assessments andScientific Basis for Management Options University of California Centers for Waterand Wildland Resources Davis CA pp 1009ndash1030

Krosby M Norheim R Theobald D McRae BH 2014 Riparian Climate-CorridorsIdentifying Priority Areas for Conservation in a changing Climate

Lacey HB 1996 Dancing in place the Clinton Administration and aquatic ecosystemprotection in the Pacific Northwest Nat Resour J 36

Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

Millard MJ Czarnecki CA Morton JM Brandt LA Briggs JS Shipley FS Sayre RSponholtz PJ Perkins D Simpkins DG Taylor J 2012 A national geographic

Fig 3 Riparian connectivity emerging from current policy The map shows the concentration of easements near or within the floodplain along the Mississippi and Red Rivers which col-lectively start to form a de facto corridor

34 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

governance that is nevertheless not currently coordinated for purposesof connectivity (Arthington et al 2010) Such mechanisms have beenput in place for a variety of services including water quality (CWA)single species protection (ESA) or soil conservation (CRP) The CWAhas already helped to restore and prevent degradation of many riparianareas to improve water quality through its direct controls on pollutersand restrictions on aquatic habitat destruction (Adler et al 2013)Nevertheless many waters across the United States remain impairedin part because of failure to integrate land use regulation with imple-mentation of federal laws such as the CWA and ESA (Cosens and Stow

2014) Mechanisms already have emerged to address the failure ofregulatory programs like the CWA and ESA such as incentive basedprograms like the USDA-CRP (NRC 2002)

The value of riparian protection for achieving habitat connectivityand the need to meet water quality standards may increase incentivesfor riparian protection from land conversion with minimal change inexisting law The CWA provides some incentives to develop an RCN asshown by the role it plays in driving riparian corridor protection(eg the US EPAs promotion of watershed-scale management andother state level efforts Section 404s restrictions on destruction and

35AK Fremier et al Biological Conservation 191 (2015) 29ndash37

adversemodification ofwetlands and other aquatic areas) For exampleto achieve temperature requirements of discharge permits under theCWA entities governing watersheds such as the Willamette River andthe Virginia regions of the Chesapeake Bay watershed have set uptrading programs in which a municipality pays for restoration ofshade in upstream riparian areas rather than the expensive alternativeof mechanical cooling

Implementation of the ESA has also encouraged riparian area protec-tion A high percentage of species listed for protection under the ESA areaquatic (Craig 2014) Compliance with both the CWA and ESA arefactors in developing habitat conservation plans (Native Fish HabitatConservation Plan) Similarly forestry programs at federal (NorthwestForest Plan) and state (Idaho Forestry Program Nez Perce Term SheetNez PercendashIdaho Water Rights Settlement) levels require buffer zonesalong riparian corridors in timber harvest areas The implementationof the ESA in the Pacific Northwest has placed the Federal EmergencyManagement Agency under pressure to change the National FloodInsurance Program (NFIP) by removing incentives to separate riversfrom their floodplains to allow insured development in the formerflood zone (see National Wildlife Federation v Federal EmergencyManagement Agency No C11ndash2044ndashRSM 2014 WL 5449859 WDWash Oct 24 2014)

In short CWA water quality standards ESA habitat requirementsand flood risk management goals may all be advanced by protectingsmall amounts of land in riparian corridors In addition to these regula-tory incentives planning approachesmdashincluding ESA Section 7 jeopardyassessments and the National Environmental Policy Act (NEPA)and its state counterparts the California Environmental Quality Act(CEQA)mdashcan allow for or even mandate coordination of ripariancorridor protection Other extant legal and policy protections includefinancial incentives to protect riparian lands such as incentive programsfor agriculture in the US Farm Bill (although these incentives werereduced in 2014) Another alternative is the purchase of private riparianlands by public entities or non-governmental organizations such as TheNature Conservancys water programs (Greenway program conserva-tion easements and other water programs Rollins Palmer 2008)

Other legal mechanisms associated with land management arealready playing a role in the emergence of riparian conservationparticularly across the federal public lands Notably 78 of publiclands are managed by four agenciesndashndashUSDA Forest Service US Bureauof LandManagement US National Park Service and US Fish andWildlifeServicemdashincreasing the potential for inter-agency coordination (Aycrigget al 2013) Additionally an RCN could enable a scalable policy withnested efforts to integrate currently independent and loosely coordinat-ed federal state tribal local and private actions

In addition riparian areas are pre-defined by the stream networkwhich simplifies the process of selecting corridor routes compared tospecies-specific terrestrial corridors (Hilty et al 2006) By simplifyingthe corridor selection procedure the RCN thus offers a simpler imple-mentation strategy Nonetheless although this simplicity is attractiveat conceptual and policy levels the effectiveness in improving connec-tivity and species survival through an RCN must be evaluated at thefield level For example the RCN cannot serve as a replacement corridorselection procedure in situations where species will not use riparianareas or the areasmight not have suitable riparian corridors In additionmore detailed local-scale analysis is needed to determine how andwhere local riparian corridors should be concentrated RCN researchalong these lines could dovetail with research already being completedsuch as the Riparian Climate-Corridors which incorporates mappedriparian areas and climate projections (Beier 2012 Krosby et al 2014)

42 A policy path to a riparian connectivity network

Although conceptually simple building connected corridors requirescoordination among governance agencies and private landownersThere currently is no federal policy mechanism for connecting

landscapes at any scale Although planning is underway for large-scalecorridors (ecoregions biomes) efforts lack sufficient generality fornational-scale application (Hilty et al 2006) Nevertheless there aremultiple examples of regional-scale cooperative restoration effortsthat may offer governance models for building connectivity TheChesapeake Bay region inMaryland andVirginia the Florida Evergladesand the Greater Yellowstone Ecosystem in Wyoming Montana andIdaho are regional examples of multiagency collaborative managementto maintain conservation integrity (Noss et al 2002) as are theWestern Governors Associations discussions of a migratory corridoror Washington States climate-change-related efforts to addressconnectivity In addition the Partners in FlightMigratory Bird Conserva-tion program specifically targets migratory species and has hadconservation-related successes throughout North America working atlarger scales (Carter et al 2000) This program functions at the regionalscale but is planned and coordinated through lsquojoint venturersquo partner-ships and management at international scale

Coordination at coarser scales can lead to protection at finer scalesFor example wetland and riparian areas play a key role in buildingconnectivity for migrating waterfowl in the North AmericanWaterfowlManagement Plan (Williams et al 1999) Many of these efforts toimprove habitat connectivity attempt to optimize the construction ofhabitat corridors between individual preserves focusing on specificspecies or small assemblages of species within the constraints of localgeographies and prioritizing riparian lands for restoration with theirspatial configuration in mind (Theobald et al 2012) However achallenge for implementing an RCN particularly in western states isthe complicated planning and implementation of the allocation ofwater through private water rights (Adler et al 2013)

Federal resource agencies have a checkered history of workingtogether toward a common purpose in part because each is governedby different legal requirements Yet the Landscape Conservation Coop-eratives (LCCs) in the US that began as the result of a Secretarial Orderfrom the Department of the Interior in 2009 (Order No 3289 Sept 142009) exemplify emergent coordination to solve issues that persist atlarger scales (Millard et al 2012) LCCs aim to provide scientificexpertise and coordination among public and private institutions at alandscape scale In addition implementation of the ESA has led to coor-dination across multiple agencies in examples such as the NorthwestForest Plan A more proactive coordinated approach to building land-scape habitat connectivity could be incorporated into the missions ofrelevant agencies (eg National Park Service US Fish and WildlifeService Bureau of LandManagement USDA Forest Service) Presidentialguidance through an Executive Order could be used to advance thedevelopment of a more comprehensive RCN In addition at least somestates seem to be willing to pursue similar efforts for state publiclands (Citron 2010) Conversations on such lsquotop-downrsquo options arealready underway in national policy circles (USFWS 2013) In additionfactors other than species conservation are already driving riparianprotection such as ecosystem services One clear example of agencycoordination to manage riparian areas for multiple benefits is the YoloBasin near Sacramento California (Opperman et al 2009) other suchsolution have been recently proposed (Greco and Larsen 2014) Thisarea supports multiple typically competing interests by managing ricefarming and wildlife conservation while allowing flood water storageduring critical times with the added benefit of migratory bird habitatThe multiple benefits of riparian protection illustrated in the YoloBasin example can broaden actual and potential sources of supportfor an RCN including efforts to improve aquatic ecosystem servicessuch as filtration riparian vegetation and floodplain connectivity thatimprove water quality bank stabilization and flood control as well asesthetics (Bernhardt et al 2005 Fremier et al 2013) Explicitly incor-porating ecosystem services into conservation corridor protectionmechanisms would open riparian protection efforts to a broader arrayof institutions and funding sources including agencies charged withprotecting water quality and reducing flood risks and private interest

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

Adler RW Craig RK Hall ND 2013 Modern Water Law Private Property PublicRights and Environmental Protections 1st ed Foundation Press

Arthington AH Naiman RJ McCLAIN ME Nilsson C 2010 Preserving the biodiversityand ecological services of rivers new challenges and research opportunities FreshwBiol 55 1ndash16 httpdxdoiorg101111j1365-2427200902340x

Aycrigg JL Davidson A Svancara LK Gergely KJ McKerrow A Scott JM 2013Representation of ecological systems within the protected areas network of theContinental United States PLoS One 8 e54689 httpdxdoiorg101371journalpone0054689

Baron JS Gunderson L Allen CD Fleishman E McKenzie D Meyerson LA OropezaJ Stephenson N 2009 Options for national parks and reserves for adapting toclimate change Environ Manag 44 1033ndash1042 httpdxdoiorg101007s00267-009-9296-6

Battin J 2004 When good animals love bad habitats ecological traps and the conserva-tion of animal populations Conserv Biol 18 1482ndash1491 httpdxdoiorg101111j1523-1739200400417x

Beier P 2012 Conceptualizing and designing corridors for climate change Ecol Restor312ndash319

Bengtsson J Angelstam P Elmqvist T Emanuelsson U Folke C Ihse M Moberg FNystrom M 2003 Reserves resilience and dynamic landscapes AMBIO A J HumEnviron 32 389ndash396 httpdxdoiorg1015790044-7447-326389

Bernhardt ES Palmer MA Allan JD Alexander G Barnas K Brooks S Carr JClayton S Dahm C Follstad-Shah J Galat D Gloss S Goodwin P Hart DHassett B Jenkinson R Katz S Kondolf GM Lake PS Lave R Meyer JLODonnell TK Pagano L Powell B Sudduth E 2005 Synthesizing US river resto-ration efforts Science 308 636ndash637 (80-)

Biggs R Schluumlter M Biggs D Bohensky EL BurnSilver S Cundill G Dakos V DawTM Evans LS Kotschy K Leitch AM Meek C Quinlan A Raudsepp-HearneC Robards MD Schoon ML Schultz L West P 2012 Toward principles for

enhancing the resilience of ecosystem services Annu Rev Environ Resour 37421ndash448 httpdxdoiorg101146annurev-environ-051211-123836

Brauman KA Daily GC Duarte TK Mooney HA 2007 The nature and value ofecosystem services an overview highlighting hydrologic services Annu RevEnviron Resour 32 67ndash98 (doihttpdxdoiorg101146annurevenergy32031306102758 U httparjournalsannualreviewsorgdoiabs101146annurevenergy32031306102758)

Brost BM Beier P 2012 Comparing linkage designs based on land facets to linkagedesigns based on focal species PLoS One 7 e48965 httpdxdoiorg101371journalpone0048965

Carter M Hunter W Pashley D Rosenberg K 2000 Setting conservation prioritiesfor landbirds in the United States the Partners in Flight approach Auk 117 541ndash548

Citron A 2010 Working rivers and working landscapes using short-term water useagreements to conserve Arizonas riparian and agricultural heritage ArizonaJ Environ Law Policy 1

Clevenger AP Waltho N 2000 Factors influencing the effectiveness of wildlifeunderpasses in Banff National Park Alberta Canada Conserv Biol 14 47ndash56httpdxdoiorg101046j1523-1739200000099-085x

Cosens B Stow C 2014 Resilience and water governance addressing fragmentationand uncertainty in water allocation and water quality law In Garmestani A AllenCR (Eds) Social-Ecological Resilience and Law Columbia University Press p 416

Craig RK 2014 Does the Endangered Species Act Preempt State Water LawCrimmins SM Dobrowski SZ Greenberg J a Abatzoglou JT Mynsberge AR

2011 Changes in climatic water balance drive downhill shifts in plant speciesoptimum elevations Science 331 324ndash327 httpdxdoiorg101126science1199040 (80-)

ElmoreW Beschta RL 1987 Riparian areas perceptions inmanagement Rangelands 9Elmqvist T Folke C Nystrom M Peterson G Bengtsson J Walker B Norberg J 2003

Response diversity ecosystem change and resilience Front Ecol Environ 1488ndash494 httpdxdoiorg1018901540-9295(2003)001[0488RDECAR]20CO2

Fremier AK Declerck FAJ Bosque-Peacuterez NA Carmona NE Hill R Joyal T Keesecker LKlos PZ Martiacutenez-Salinas A Niemeyer R Sanfiorenzo A Welsh K Wulfhorst JD2013 Understanding spatiotemporal lags in ecosystem services to improve incentivesBioscience 63 472ndash482 httpdxdoiorg101525bio20136369

Gilbert-Norton L Wilson R Stevens JR Beard KH 2010 A meta-analytic review ofcorridor effectiveness Conserv Biol 24 660ndash668 httpdxdoiorg101111j1523-1739201001450x

Goetz SJ Jantz P Jantz CA 2009 Connectivity of core habitat in the NortheasternUnited States parks and protected areas in a landscape context Remote SensEnviron 113 1421ndash1429 httpdxdoiorg101016jrse200807019

Goldman RL Tallis H 2009 A critical analysis of ecosystem services as a tool inconservation projects the possible perils the promises and the partnerships AnnN Y Acad Sci 1162 63ndash78 httpdxdoiorg101111j1749-6632200904151x

Greco SE Larsen EW 2014 Ecological design of multifunctional open channels forflood control and conservation planning Landsc Urban Plan 131 14ndash26 httpdxdoiorg101016jlandurbplan201407002

Griffith B Scott JM Adamcik R Ashe D Czech B Fischman R Gonzalez P Lawler JMcGuire AD Pidgorna A 2009 Climate change adaptation for the US NationalWildlife Refuge System Environ Manag 44 1043ndash1052 httpdxdoiorg101007s00267-009-9323-7

Haddad NM Brudvig La Damschen EI Evans DM Johnson BL Levey DJ OrrockJL Resasco J Sullivan LL Tewksbury JJ Wagner Sa Weldon AJ 2014 Potentialnegative ecological effects of corridors Conserv Biol 28 1178ndash1187 httpdxdoiorg101111cobi12323

Hannah L Midgley GF Lovejoy T BondWJ Bush M Lovett JC Scott DWoodwardFI 2002 Conservation of biodiversity in a changing climate Conserv Biol 16264ndash268 httpdxdoiorg101046j1523-1739200200465x

Hilty JA Merenlender AM 2004 Use of riparian corridors and vineyards by mammali-an predators in Northern California Conserv Biol 10 126ndash135

Hilty JA Lidicker WZ Merenlender AM 2006 Corridor Ecology The Science andPractice of Linking Landscapes for Biodiversity Conservation 1st ed Island PressWashington DC

Johnston A Ausden M Dodd AM Bradbury RB Chamberlain DE Jiguet F ThomasCD Cook ASCP Newson SE Ockendon N Rehfisch MM Roos S Thaxter CBBrown A Crick HQP Douse A McCall RA Pontier H Stroud DA Cadiou BCrowe O Deceuninck B Hornman M Pearce-Higgins JW 2013 Observed andpredicted effects of climate change on species abundance in protected areas NatClim Chang 3 1055ndash1061 httpdxdoiorg101038nclimate2035

Kline JD Alig RJ Johnson RL 2000 Forest owner incentives to protect riparian habitatEcol Econ 33 29ndash43 httpdxdoiorg101016S0921-8009(99)00116-0

Kondolf GM Kattelman R Embury M Erman D 1996 Status of riparian habitat SierraNevada Ecosystem Project Final Report to Congress Vol II Assessments andScientific Basis for Management Options University of California Centers for Waterand Wildland Resources Davis CA pp 1009ndash1030

Krosby M Norheim R Theobald D McRae BH 2014 Riparian Climate-CorridorsIdentifying Priority Areas for Conservation in a changing Climate

Lacey HB 1996 Dancing in place the Clinton Administration and aquatic ecosystemprotection in the Pacific Northwest Nat Resour J 36

Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

Millard MJ Czarnecki CA Morton JM Brandt LA Briggs JS Shipley FS Sayre RSponholtz PJ Perkins D Simpkins DG Taylor J 2012 A national geographic

35AK Fremier et al Biological Conservation 191 (2015) 29ndash37

adversemodification ofwetlands and other aquatic areas) For exampleto achieve temperature requirements of discharge permits under theCWA entities governing watersheds such as the Willamette River andthe Virginia regions of the Chesapeake Bay watershed have set uptrading programs in which a municipality pays for restoration ofshade in upstream riparian areas rather than the expensive alternativeof mechanical cooling

Implementation of the ESA has also encouraged riparian area protec-tion A high percentage of species listed for protection under the ESA areaquatic (Craig 2014) Compliance with both the CWA and ESA arefactors in developing habitat conservation plans (Native Fish HabitatConservation Plan) Similarly forestry programs at federal (NorthwestForest Plan) and state (Idaho Forestry Program Nez Perce Term SheetNez PercendashIdaho Water Rights Settlement) levels require buffer zonesalong riparian corridors in timber harvest areas The implementationof the ESA in the Pacific Northwest has placed the Federal EmergencyManagement Agency under pressure to change the National FloodInsurance Program (NFIP) by removing incentives to separate riversfrom their floodplains to allow insured development in the formerflood zone (see National Wildlife Federation v Federal EmergencyManagement Agency No C11ndash2044ndashRSM 2014 WL 5449859 WDWash Oct 24 2014)

In short CWA water quality standards ESA habitat requirementsand flood risk management goals may all be advanced by protectingsmall amounts of land in riparian corridors In addition to these regula-tory incentives planning approachesmdashincluding ESA Section 7 jeopardyassessments and the National Environmental Policy Act (NEPA)and its state counterparts the California Environmental Quality Act(CEQA)mdashcan allow for or even mandate coordination of ripariancorridor protection Other extant legal and policy protections includefinancial incentives to protect riparian lands such as incentive programsfor agriculture in the US Farm Bill (although these incentives werereduced in 2014) Another alternative is the purchase of private riparianlands by public entities or non-governmental organizations such as TheNature Conservancys water programs (Greenway program conserva-tion easements and other water programs Rollins Palmer 2008)

Other legal mechanisms associated with land management arealready playing a role in the emergence of riparian conservationparticularly across the federal public lands Notably 78 of publiclands are managed by four agenciesndashndashUSDA Forest Service US Bureauof LandManagement US National Park Service and US Fish andWildlifeServicemdashincreasing the potential for inter-agency coordination (Aycrigget al 2013) Additionally an RCN could enable a scalable policy withnested efforts to integrate currently independent and loosely coordinat-ed federal state tribal local and private actions

In addition riparian areas are pre-defined by the stream networkwhich simplifies the process of selecting corridor routes compared tospecies-specific terrestrial corridors (Hilty et al 2006) By simplifyingthe corridor selection procedure the RCN thus offers a simpler imple-mentation strategy Nonetheless although this simplicity is attractiveat conceptual and policy levels the effectiveness in improving connec-tivity and species survival through an RCN must be evaluated at thefield level For example the RCN cannot serve as a replacement corridorselection procedure in situations where species will not use riparianareas or the areasmight not have suitable riparian corridors In additionmore detailed local-scale analysis is needed to determine how andwhere local riparian corridors should be concentrated RCN researchalong these lines could dovetail with research already being completedsuch as the Riparian Climate-Corridors which incorporates mappedriparian areas and climate projections (Beier 2012 Krosby et al 2014)

42 A policy path to a riparian connectivity network

Although conceptually simple building connected corridors requirescoordination among governance agencies and private landownersThere currently is no federal policy mechanism for connecting

landscapes at any scale Although planning is underway for large-scalecorridors (ecoregions biomes) efforts lack sufficient generality fornational-scale application (Hilty et al 2006) Nevertheless there aremultiple examples of regional-scale cooperative restoration effortsthat may offer governance models for building connectivity TheChesapeake Bay region inMaryland andVirginia the Florida Evergladesand the Greater Yellowstone Ecosystem in Wyoming Montana andIdaho are regional examples of multiagency collaborative managementto maintain conservation integrity (Noss et al 2002) as are theWestern Governors Associations discussions of a migratory corridoror Washington States climate-change-related efforts to addressconnectivity In addition the Partners in FlightMigratory Bird Conserva-tion program specifically targets migratory species and has hadconservation-related successes throughout North America working atlarger scales (Carter et al 2000) This program functions at the regionalscale but is planned and coordinated through lsquojoint venturersquo partner-ships and management at international scale

Coordination at coarser scales can lead to protection at finer scalesFor example wetland and riparian areas play a key role in buildingconnectivity for migrating waterfowl in the North AmericanWaterfowlManagement Plan (Williams et al 1999) Many of these efforts toimprove habitat connectivity attempt to optimize the construction ofhabitat corridors between individual preserves focusing on specificspecies or small assemblages of species within the constraints of localgeographies and prioritizing riparian lands for restoration with theirspatial configuration in mind (Theobald et al 2012) However achallenge for implementing an RCN particularly in western states isthe complicated planning and implementation of the allocation ofwater through private water rights (Adler et al 2013)

Federal resource agencies have a checkered history of workingtogether toward a common purpose in part because each is governedby different legal requirements Yet the Landscape Conservation Coop-eratives (LCCs) in the US that began as the result of a Secretarial Orderfrom the Department of the Interior in 2009 (Order No 3289 Sept 142009) exemplify emergent coordination to solve issues that persist atlarger scales (Millard et al 2012) LCCs aim to provide scientificexpertise and coordination among public and private institutions at alandscape scale In addition implementation of the ESA has led to coor-dination across multiple agencies in examples such as the NorthwestForest Plan A more proactive coordinated approach to building land-scape habitat connectivity could be incorporated into the missions ofrelevant agencies (eg National Park Service US Fish and WildlifeService Bureau of LandManagement USDA Forest Service) Presidentialguidance through an Executive Order could be used to advance thedevelopment of a more comprehensive RCN In addition at least somestates seem to be willing to pursue similar efforts for state publiclands (Citron 2010) Conversations on such lsquotop-downrsquo options arealready underway in national policy circles (USFWS 2013) In additionfactors other than species conservation are already driving riparianprotection such as ecosystem services One clear example of agencycoordination to manage riparian areas for multiple benefits is the YoloBasin near Sacramento California (Opperman et al 2009) other suchsolution have been recently proposed (Greco and Larsen 2014) Thisarea supports multiple typically competing interests by managing ricefarming and wildlife conservation while allowing flood water storageduring critical times with the added benefit of migratory bird habitatThe multiple benefits of riparian protection illustrated in the YoloBasin example can broaden actual and potential sources of supportfor an RCN including efforts to improve aquatic ecosystem servicessuch as filtration riparian vegetation and floodplain connectivity thatimprove water quality bank stabilization and flood control as well asesthetics (Bernhardt et al 2005 Fremier et al 2013) Explicitly incor-porating ecosystem services into conservation corridor protectionmechanisms would open riparian protection efforts to a broader arrayof institutions and funding sources including agencies charged withprotecting water quality and reducing flood risks and private interest

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

Adler RW Craig RK Hall ND 2013 Modern Water Law Private Property PublicRights and Environmental Protections 1st ed Foundation Press

Arthington AH Naiman RJ McCLAIN ME Nilsson C 2010 Preserving the biodiversityand ecological services of rivers new challenges and research opportunities FreshwBiol 55 1ndash16 httpdxdoiorg101111j1365-2427200902340x

Aycrigg JL Davidson A Svancara LK Gergely KJ McKerrow A Scott JM 2013Representation of ecological systems within the protected areas network of theContinental United States PLoS One 8 e54689 httpdxdoiorg101371journalpone0054689

Baron JS Gunderson L Allen CD Fleishman E McKenzie D Meyerson LA OropezaJ Stephenson N 2009 Options for national parks and reserves for adapting toclimate change Environ Manag 44 1033ndash1042 httpdxdoiorg101007s00267-009-9296-6

Battin J 2004 When good animals love bad habitats ecological traps and the conserva-tion of animal populations Conserv Biol 18 1482ndash1491 httpdxdoiorg101111j1523-1739200400417x

Beier P 2012 Conceptualizing and designing corridors for climate change Ecol Restor312ndash319

Bengtsson J Angelstam P Elmqvist T Emanuelsson U Folke C Ihse M Moberg FNystrom M 2003 Reserves resilience and dynamic landscapes AMBIO A J HumEnviron 32 389ndash396 httpdxdoiorg1015790044-7447-326389

Bernhardt ES Palmer MA Allan JD Alexander G Barnas K Brooks S Carr JClayton S Dahm C Follstad-Shah J Galat D Gloss S Goodwin P Hart DHassett B Jenkinson R Katz S Kondolf GM Lake PS Lave R Meyer JLODonnell TK Pagano L Powell B Sudduth E 2005 Synthesizing US river resto-ration efforts Science 308 636ndash637 (80-)

Biggs R Schluumlter M Biggs D Bohensky EL BurnSilver S Cundill G Dakos V DawTM Evans LS Kotschy K Leitch AM Meek C Quinlan A Raudsepp-HearneC Robards MD Schoon ML Schultz L West P 2012 Toward principles for

enhancing the resilience of ecosystem services Annu Rev Environ Resour 37421ndash448 httpdxdoiorg101146annurev-environ-051211-123836

Brauman KA Daily GC Duarte TK Mooney HA 2007 The nature and value ofecosystem services an overview highlighting hydrologic services Annu RevEnviron Resour 32 67ndash98 (doihttpdxdoiorg101146annurevenergy32031306102758 U httparjournalsannualreviewsorgdoiabs101146annurevenergy32031306102758)

Brost BM Beier P 2012 Comparing linkage designs based on land facets to linkagedesigns based on focal species PLoS One 7 e48965 httpdxdoiorg101371journalpone0048965

Carter M Hunter W Pashley D Rosenberg K 2000 Setting conservation prioritiesfor landbirds in the United States the Partners in Flight approach Auk 117 541ndash548

Citron A 2010 Working rivers and working landscapes using short-term water useagreements to conserve Arizonas riparian and agricultural heritage ArizonaJ Environ Law Policy 1

Clevenger AP Waltho N 2000 Factors influencing the effectiveness of wildlifeunderpasses in Banff National Park Alberta Canada Conserv Biol 14 47ndash56httpdxdoiorg101046j1523-1739200000099-085x

Cosens B Stow C 2014 Resilience and water governance addressing fragmentationand uncertainty in water allocation and water quality law In Garmestani A AllenCR (Eds) Social-Ecological Resilience and Law Columbia University Press p 416

Craig RK 2014 Does the Endangered Species Act Preempt State Water LawCrimmins SM Dobrowski SZ Greenberg J a Abatzoglou JT Mynsberge AR

2011 Changes in climatic water balance drive downhill shifts in plant speciesoptimum elevations Science 331 324ndash327 httpdxdoiorg101126science1199040 (80-)

ElmoreW Beschta RL 1987 Riparian areas perceptions inmanagement Rangelands 9Elmqvist T Folke C Nystrom M Peterson G Bengtsson J Walker B Norberg J 2003

Response diversity ecosystem change and resilience Front Ecol Environ 1488ndash494 httpdxdoiorg1018901540-9295(2003)001[0488RDECAR]20CO2

Fremier AK Declerck FAJ Bosque-Peacuterez NA Carmona NE Hill R Joyal T Keesecker LKlos PZ Martiacutenez-Salinas A Niemeyer R Sanfiorenzo A Welsh K Wulfhorst JD2013 Understanding spatiotemporal lags in ecosystem services to improve incentivesBioscience 63 472ndash482 httpdxdoiorg101525bio20136369

Gilbert-Norton L Wilson R Stevens JR Beard KH 2010 A meta-analytic review ofcorridor effectiveness Conserv Biol 24 660ndash668 httpdxdoiorg101111j1523-1739201001450x

Goetz SJ Jantz P Jantz CA 2009 Connectivity of core habitat in the NortheasternUnited States parks and protected areas in a landscape context Remote SensEnviron 113 1421ndash1429 httpdxdoiorg101016jrse200807019

Goldman RL Tallis H 2009 A critical analysis of ecosystem services as a tool inconservation projects the possible perils the promises and the partnerships AnnN Y Acad Sci 1162 63ndash78 httpdxdoiorg101111j1749-6632200904151x

Greco SE Larsen EW 2014 Ecological design of multifunctional open channels forflood control and conservation planning Landsc Urban Plan 131 14ndash26 httpdxdoiorg101016jlandurbplan201407002

Griffith B Scott JM Adamcik R Ashe D Czech B Fischman R Gonzalez P Lawler JMcGuire AD Pidgorna A 2009 Climate change adaptation for the US NationalWildlife Refuge System Environ Manag 44 1043ndash1052 httpdxdoiorg101007s00267-009-9323-7

Haddad NM Brudvig La Damschen EI Evans DM Johnson BL Levey DJ OrrockJL Resasco J Sullivan LL Tewksbury JJ Wagner Sa Weldon AJ 2014 Potentialnegative ecological effects of corridors Conserv Biol 28 1178ndash1187 httpdxdoiorg101111cobi12323

Hannah L Midgley GF Lovejoy T BondWJ Bush M Lovett JC Scott DWoodwardFI 2002 Conservation of biodiversity in a changing climate Conserv Biol 16264ndash268 httpdxdoiorg101046j1523-1739200200465x

Hilty JA Merenlender AM 2004 Use of riparian corridors and vineyards by mammali-an predators in Northern California Conserv Biol 10 126ndash135

Hilty JA Lidicker WZ Merenlender AM 2006 Corridor Ecology The Science andPractice of Linking Landscapes for Biodiversity Conservation 1st ed Island PressWashington DC

Johnston A Ausden M Dodd AM Bradbury RB Chamberlain DE Jiguet F ThomasCD Cook ASCP Newson SE Ockendon N Rehfisch MM Roos S Thaxter CBBrown A Crick HQP Douse A McCall RA Pontier H Stroud DA Cadiou BCrowe O Deceuninck B Hornman M Pearce-Higgins JW 2013 Observed andpredicted effects of climate change on species abundance in protected areas NatClim Chang 3 1055ndash1061 httpdxdoiorg101038nclimate2035

Kline JD Alig RJ Johnson RL 2000 Forest owner incentives to protect riparian habitatEcol Econ 33 29ndash43 httpdxdoiorg101016S0921-8009(99)00116-0

Kondolf GM Kattelman R Embury M Erman D 1996 Status of riparian habitat SierraNevada Ecosystem Project Final Report to Congress Vol II Assessments andScientific Basis for Management Options University of California Centers for Waterand Wildland Resources Davis CA pp 1009ndash1030

Krosby M Norheim R Theobald D McRae BH 2014 Riparian Climate-CorridorsIdentifying Priority Areas for Conservation in a changing Climate

Lacey HB 1996 Dancing in place the Clinton Administration and aquatic ecosystemprotection in the Pacific Northwest Nat Resour J 36

Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

Millard MJ Czarnecki CA Morton JM Brandt LA Briggs JS Shipley FS Sayre RSponholtz PJ Perkins D Simpkins DG Taylor J 2012 A national geographic

36 AK Fremier et al Biological Conservation 191 (2015) 29ndash37

groups seeking improvements in hunting and fishing opportunities(Goldman and Tallis 2009) Moreover riparian landowners tend to be-come invested in the health of waters bordering their properties(Elmore and Beschta 1987)

The basis for operationalizing an RCN lies in a coordinated policythat could be realized through the integration of independent andloosely coordinated federal state tribal local and private actions intoa coherent larger set of outcomes Because 78 of all public lands aremanaged by only four federal agencies promoting collaborationbetween these agencies provides a conceptual pathway toward integra-tion for larger conservation resiliency Further coordinating withexisting private conservation easements that already are spatiallybiased toward riparian areas could amplify progress toward a coherentconservation network Finally governing entities supporting the furtherdevelopment of an RCN could reach beyond biological conservation tosupport conservation goals to leverage other existing mechanisms forprotection such as flood management policies water quality require-ments and recreation policies We have argued that the seeds foran RCN are already in place geospatially as well as institutionallyMobilizing public private and multiparty efforts at local regional andnational scales (Ostrom et al 1999) will be necessary to achieve afully-connected RCN With the right motivation and action includingbut the already emerging RCN clearly could continue to grow in waysthat increasingly promote socio-ecological resilience through collabora-tion among multiple levels of governance using existing legal policyand social mechanisms the nascent RCN could grow and promotesocio-ecological resilience

Acknowledgments

The authors acknowledge the support of our respective institutionsfor supporting this work JAs time was funded under the US GeologicalSurvey Gap Analysis Programunder researchwork order G12AC20244to the University of Idaho Funding provided staff time and did notinfluence study design data collection data analysis data interpreta-tion writing of the report or decisions on publication We receivedsome funding from the University of Idaho We thank Brady GreenDaniel Thornton Amanda Stahl and Steve Katz for input on earlierdrafts Three anonymous reviewers provided valuable comments onour manuscript

References

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Lees AC Peres CA 2008 Conservation value of remnant riparian forest corridors ofvarying quality for Amazonian birds and mammals Conserv Biol 22 439ndash449httpdxdoiorg101111j1523-1739200700870x

Mann KB Berry KA Bassett S Chandra S 2013 Voting on floodplain conservationthe role of public values and interactions along the Carson River Nevada Soc NatResour 26 568ndash585 httpdxdoiorg101080089419202012713449

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