sustaining the grassland sea: regional perspectives on … · 2013-07-26 · usda forest service...

USDA Forest Service Proceedings RMRS-P-67. 2013 399

In: Gottfried, Gerald J.; Ffolliott, Peter F.; Gebow, Brooke S.; Eskew, Lane G.; Collins, Loa C., comps. 2013. Merging science and management in a rapidly changing world: Biodiversity and management of the Madrean Archipelago III; 2012 May 1-5; Tucson, AZ. Proceedings. RMRS-P-67. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station.

Sustaining the Grassland Sea: Regional Perspectives on Identifying, Protecting and Restoring the Sky Island Region’s Most Intact Grassland Valley Landscapes

Gitanjali S. Bodner and Peter Warren The Nature Conservancy in Arizona

David Gori, Karla Sartor, and Steven Bassett The Nature Conservancy in New Mexico

Abstract—Grasslands of the Sky Islands region once covered over 13 million acres in southeastern Arizona and adjacent portions of New Mexico, Sonora, and Chihuahua. Attempts to evaluate current ecological conditions suggest that approximately two thirds of these remain as intact or restorable grassland habitat. These grasslands provide watershed services such as flood control and aquifer recharge across the region, and continue to support dozens of species of concern. Prioritizing conservation interventions for these remaining grassland blocks has been challenging. Reliable data on condition and conservation value of grasslands in the region have not been systematically summarized. State and national boundaries further complicate efforts to identify where the best remaining habitats and populations of grassland obligate species still exist. We present results of an effort to merge grassland condition assessments, compile information on target species locations, and identify “priority grassland valley landscapes” across the region. We evaluate these priority landscapes in terms of the number of target species, critical threats, and enabling conditions for long-term conservation success such as activity by local cooperative groups dedicated to sustaining their landscapes. Lastly, we discuss the opportunities and challenges of designing and implementing effective restoration activities in these large multi-jurisdictional landscapes.

Introduction The grasslands of central and southernArizona, southernNewMexico,andnorthernMexico,referredtohereasSkyIslandgrass-lands,formthe“grasslandseas”thatsurroundsmallforestedmountainranges,transitioningintodesertscrublandsaselevationsdrop,orintofoothillwoodlandsorchaparralaselevationsrise.Atthecontinentalscale,SkyIslandgrasslandsformauniquesettingwherethelargeblocks ofGreat Plains andChihuahuanDesert grasslands east oftheRockiesandSierraMadreMountains spillovera lowspot intheContinentalDivide.Thisecotonegeographyandtheecologicalgradientsassociatedwith“SkyIslandmountainsandgrasslandseas”addtremendousfloralandfaunaldiversitytotheregionasawhole(McClaranandVanDevender1997).Grasslandvalley landscapeshereareoftenrecognizedasdistinctandimportantplacesbytheirrespectivehumancommunities,whoself-organizetovaryingdegreesin order to benefit fromandprotect the ecological and economicvaluesoftheseplaces.

SkyIslandgrasslandshaveundergonedramaticvegetationchangesoverthelast130yearsincludingencroachmentbyshrubsandtrees,lossofperennialgrasscoverandspreadofnon-nativespecies(Hum-phrey1987;Bahre1991).Thecausesforthesevegetationchangeshavebeenthesubjectofdebateandrangefromchangesinregionalclimatetohumanimpactsincludingpoorlymanagedlivestockgrazingandsuppressionofwildfires(Humphrey1958;BuffingtonandHerbel1965;HastingsandTurner1965;Cable1967;Wright1980;Bahre1985,1995;Swetnam1990;Brownandothers1997;McPhersonandWeltzin2000). Changes in grassland composition and structure have not oc-curreduniformlyacrosstheborderlandregion,noraretheysolelytheconsequenceofpastclimaticeventsorhumanimpactsbutareongoingtoday(Archer1989;Bahre1991;Brownandothers1997;Ceballosandothers2010).Thesechanges,combinedwithincreasedfragmentationduetoexurbandevelopmentandagriculturalconver-sion,havecausedsignificantdeclinesingrasslandspecies,especiallywide-rangingones. Althoughtheabovestudies,aswellasothers,havedocumentedchangetograsslandslocally,therehavebeenonlyafewattemptstocharacterizetheextentofchangeorassesscurrentgrasslandcondi-tionofborderlandgrasslandsatbroaderscales(CoxandRuyle1986;EnquistandGori2008;Yanoffandothers2008). In 2009, The National Fish andWildlife Foundation (NFWF)launcheditsSkyIslandGrasslandInitiative,a10-yearplantoprotectandrestoregrasslandsandembeddedwetlandandriparianhabitatsintheSkyIslandregion(fig.1).TheInitiativeemphasizesgrasslandrestoration, protecting threatened land and water, and restoring

400 USDA Forest Service Proceedings RMRS-P-67. 2013

Bodner and others Sustaining the Grassland Sea: Regional Perspectives on Identifying, Protecting . . .

populationsoftargetwildlifespecies(NFWF2009).TheFoundationanticipatesinvestingmillionsofdollarstoachievethesegoalsandexpectstoleverageadditionalmillionsinfederal,stateandprivatefunds.Thequestionis:wherewillthisinvestmentyieldthegreatestreturnsintermsofrestoringgrasslandhealthandrecoveringwildlifespeciesacrosstheregion? This reportattempts toanswer thisquestionata regional scalebyintegratingtworecentspatialassessmentsofthehistoricalextentandcurrentconditionofSkyIslandgrasslandsandsavannasaswellascompilinginformationontheoccurrenceofgrassland-dependentwildlife and species of concern. Using this information and anexpert-basedapproach,weidentify12prioritylandscapeswherethepotentialforrestoringgrasslandsandrecoveringtargetspecieshavethegreatestprobabilityofsuccess.Weidentifyandevaluatethesepriority landscapes basedon their size, condition, landscape con-text,numberoftargetspeciesandnaturalcommunities,andhuman

enablingconditionsforlong-termconservationsuccess.Thelatterfactorincludestheexistenceofpartnerships,suchaslocalcoopera-tivegroupsdedicatedtosustainingtheirlandscape;landprotectionefforts;andongoingecologicalrestorationandmanagement.

Methods

Mapping Grassland Condition

TworecentassessmentsofhistoricalgrasslandextentandcurrentconditionformthebasisofthisSkyIslandGrasslandAssessmentandcovermostofthehistoricalandremaininggrasslandsandsavannasintheSkyIslandregion:theApacheHighlandGrasslandAssessment(AHGA;GoriandEnquist2003)andtheNewMexicoRangelandEcologicalAssessment(REA;Yanoffandothers2008).TheAHGAdefinedaseriesofgrasslandconditionclassesusingexpertopinion

Figure 1—Current condition of Grasslands in the Sky Island focal area.


Sustaining the Grassland Sea: Regional Perspectives on Identifying, Protecting . . . Bodner and others

andthepeer-reviewedliteraturetodefinethresholdvaluesforshrubcover.Mapping of these condition classeswas done by 24 rangemanagementspecialistsfromfederalandstateagencies,academicinstitutionsandnon-governmentalorganizationsfortheU.S.andacombinationofexpertsandLANDSATsatelliteimageryanalysisforMexico.Mappingwasatapproximately1:100,000to1:250,000scale.AHGAconditionclassesweredefinedbypercentwoodyplantcover,comparedtohistoricalcondition,andwhetherthegrassspecieswerenative,non-native,uplandorriparian(table1).TheAHGAconsideredfiretobeamajornaturaldisturbancethatcontrolledwoodyplantsandmaintainedgrassdominancehistorically.TheAHGAincludedacomprehensiveaccuracyassessmentusing234fieldsamplingpointsintheU.S.portionoftheApacheHighlandsecoregion.Theoverallaccuracyrateofthefinalmapwasgreaterthan77%. TheNewMexicoRangelandEcologicalAssessment(REA)waslimitedtosouthernNewMexicoandincludesthenortheasternpor-tionoftheSkyIslandsprojectarea.Mappingwascompletedby70expertsatapproximately1:23,000-1:100,000scale.ConditionclassesintheREAarevegetationstatesinthestate-and-transitionmodelsthataccompanyNaturalResourcesConservationService’secologicalsitedescriptions(NRCS2009b).REAconditionclassesaresimilartothoseoftheAHGAinthatmostalteredclassesreflectincreasesinwoodyplantcoveroverhistoricalcondition.However,REAclassesarefiner-scale,beingassociatedwithecologicalsites,andstressrela-tiveratherthanquantitativewoodycover,thedistributionofgrassesbetweenorunderwoodyplants, grass compositiondominatedbylong-livedperennialgrassesversussparseruderalperennialorannualspecies,andnon-vegetativeindicatorssuchassoilerosion(table1).TheREAdidnotmapnon-nativegrasses,asthespreadofLehmannandBoerlovegrassintosouthwestNewMexicowaslimitedbefore

2007(GoriandEnquist2003;Schussmanandothers2006).TheREAdidnotincludeanaccuracyassessment. For thisanalysis, the twoassessmentswerecombined intoonespatialdatasetbygroupingthefiner-scaleREAconditionclassesuptoAHGAclasses(table1).ThecombinedspatialdatasetdoesnotidentifygrasslandsinMexicooutsideoftheApacheHighlandsecore-gion.Torepresentthesegrasslands,weusedtheInstitutoNacionaldeEstadísticayGeografía(INEGI)landcovermapthatcontainsnoinformationonthecurrentconditionofgrasslandsoronthespatialextentofformergrasslands.Usingthecombineddataset,wesum-marizedthehistoricalextentandcurrentconditionofgrasslandsandsavannasacrosstheprojectarea(fig.1).

Mapping Sensitive Species and Natural Communities

ToassistintheidentificationandevaluationofSkyIslandgrasslands,wesummarizedexistinginformationfromavarietyofsourcesonthedistributionofsensitivegrasslandspeciesandriparian-aquaticspeciesthatoccurinwetlandhabitatsembeddedwithingrasslands(table2).ThesespecieswereidentifiedastargetsinNFWF’sSkyIslandBusinessPlan(NFWF2009).Inaddition,wesummarizedoccurrenceinforma-tionforseveralnaturalcommunitiesthathavedeclinedsignificantly(>90%fromhistoricalextent)overthelast100+yearsdueprimarilyto human impacts: ciénegawetlands, sacaton riparian grasslands,andChihuahuanblackgramagrasslands(HendricksonandMinckley1984;Humphrey1960;Yanoffandothers2008).OccurrencerecordsobtainedfromtheNaturalHeritageProgramsinArizona,NewMexico,andSonorawerescreenedtoidentifygrasslandandriparian-aquaticspecies.NaturalHeritagedatawerenotavailableforChihuahua.

Table 1—Sky Island Grassland Assessment condition classes and the original AHGA and REA classes.

Original assessment class Source Sky Island assessment class

Native grassland and savanna with low woody cover a AHGA No or low woody increase, native grassland and savannaNative grassland with or without ruderal grasses REA “Native savanna with or without ruderal grasses REA “Bottomland sacaton (Sporobolus wrightii, S. airoides) AHGA grassland REA “Woody-invaded native grassland and savanna with AHGA Medium woody increase, native medium woody cover b grassland and savannaWoody-invaded native grassland with or REA “ without ruderal grassesWoody-encroached native savanna with or REA “ without ruderal grasses Non-native grassland and savanna with low woody AGHA No or low woody increase, non-native cover, where non-native perennial grasses, grassland and savanna Lehmann and Boer lovegrass, are common or dominant a

Non-native grassland and savanna with medium woody cover, AHGA Medium woody increase, non-native grassland where non-native perennial grasses, and savanna Lehmann and Boer lovegrass, are common or dominant b

Former grassland and savanna with high woody cover c AHGA High woody increase, former grassland and savannaWoody-dominated former grassland REA “Woody-dominated former savanna REA “Highly eroded former grassland REA “Highly eroded former savanna REA “aWoody cover < 10%bWoody cover 10-35%, with cover of mesquite or juniper, Prosopis and Juniperus, <15%cWoody cover >15% cover mesquite and juniper combined and/or >35% total woody cover; perennial grass cover always <3%; type conversion

from grassland or savanna to shrubland.



Tapping Expert Knowledge to Delineate and Evaluate Highlight Priority Landscapes

Intheprocessofcompilingtheinformationabove,werecognizedthatthesesourcesdidnotfullycapturethecollectiveknowledgethatweknewtoexistfortheregion.InSeptember2010,weassembledseveral experts to both expand our understanding of grasslandsacrosstheregionandtoexplicitlydelineatefocalareas.Participantsincluded:AngelMontoya,PeregrineFundandPartnersforFishandWildlife;DanRobinett,NRCS retired;MilesTraphagen,Turn of The Century Monitoring Inc.;andfromTheNatureConservancy:GitaBodner,DaveGori,PeterWarren,andStevenYanoff,assistedbyAnneBradleyandLaraMiller. Participantswereaskedtomapareastheyviewedasparticularlypromisingforsustainingtheregion’sgrasslandsoverthelongterm,drawingontheirownknowledgeandavarietyofsupportinginfor-mationprovided at theworkshop.We seeded thediscussionwithsuggestedcriteriaforidentifying,delimiting,andevaluating“prioritygrasslandlandscapes”andwithpolygonsusedintheNFWFBusinessPlan(NFWF2009),butparticipantswerefreetomapanddescribeattributesofthesedelineatedareasastheysawfit.Suggestedcriteriaincludedsizeofgrasslandblocks,ecologicalconditionofthoseblocks,presenceofembeddedstreamsandwetlandsandtargetwildlifespe-cies,fragmentationversusconnectivityofgrasslandhabitatandofnativevegetationmorebroadly,presenceofintractablethreats,andexistenceofconservationeffortssuchaslocalcommunitypartner-ships.Spatialdatasetsprovidedtoparticipantsincludedinformationonvegetationclassifications,AHGAandREAgrasslandconditionassessments, soil classifications, species occurrence locations andhabitatmodels,landprotectionstatus,andresultsofvariousgroups’effortstoidentifypriorityconservationareasforotherpurposes.Oncepolygonsweredrawnandmetwithgroupagreement,participantswereaskedtofilloutamatrixofconservationvalueandfeasibilityforeach.Criteriaevaluatedincludedmanyof thesameonesusedto inform thedrawingof thepolygons, but this exercise requiredparticipantstoratecriteriaforeachsiteaslow,medium,orhighand,

wherenecessary,explainthoseratings.Thiswasdoneasagroupef-fort,withdiscussionofrankingsalongtheway.Fillingoutthematrixtogetheralsospawneddiscussionsaboutthecharacteristicsofeachgrassland landscape, and about additional sources of informationaboutdistributionsoftargetspeciesandcommunities.

Results and Discussion Hereafter,wewillreferto“grasslandsandsavannas”collectivelyas“grasslands”tostreamlinethepresentationanddiscussionofresults.

Historic Distribution and Current Condition of Sky Island Grasslands

ExpertsintheUnitedStatesandMexicoidentified13,902,000acresascurrentorformergrassland,whichcorrespondstoalmosthalfoftheareaweanalyzed(table3;fig.1).Weassumethatthisrepresentsaconservativefigureforthehistoricdistributionandextentofgrass-lands in thisarea.Furthermore,grasslandswerehighlyconnectedhistorically,allowingwide-rangingspecies, likebison,pronghorn,andgrasslandbirds,aswellasspecieswithmorelimiteddispersalcapabilities,likeblack-tailedprairiedogs,tomovefreelywithinandbetweenthesehabitats. Only2.6millionacresor18.9%ofthesegrasslandsarecurrentlydominatedbynativegrassesandrelativelyopenandshrubfree.Bycomparison,shrubencroachmenthasoccurredonover8,159,000acresor58.7%ofcurrentandformergrasslands.Approximately4.9millionacresor35.1%ofcurrentandformergrasslandshaveexperiencedmoreshrubencroachmentbutstillfallintoclasseswherethischangeisconsideredreversible,forexample,withprescribedfireorotherbrush controlmethods.However, shrub cover and associated soilerosionhasexceededathresholdonover3.2millionacres,producingatypeconversionfromgrasslandtoshrublandonalmostonequarterofthehistoricgrasslandsandsavannasinthisregion.Suchareasareconsidereddifficultifnotimpossibletoreturntoopengrasslandstates

Table 2--Spatial data collected and data sources for analysis of NFWF target and high-priority grassland and riparian-aquatic species occurrences in priority grassland landscapes.

Biological feature Data source

Ciénega Ciénega database and spatial layer developed by TNC-AZ based on literature, agency reports, expert knowledge and field reconnaissance Sacaton riparian grasslands Mapped by experts, AHGA (Gori & Enquist 2003; Enquist and Gori 2008) and REA (Yanoff and others 2008)Black grama grasslands Mapped by experts: historical extent and current condition on Sandy and Shallow Sandy ecological sites; REA (Yanoff and others 2008)Black-tailed prairie dog Database and spatial layer developed by TNC-AZ based on (Cynomys ludovicianus) colonies literature, agency reports & expert knowledge.Pronghorn (Antilocapra americana) Spatial layer developed by TNC-AZ & NM based on Brown and Ockenfels (2007), AZGFD (2010) and expert knowledgeJaguar (Panthera onca) Spatial layer developed by TNC-NM and AZ based on agency reports and expert knowledgeBison (Bison bison) Spatial layer developed by TNC-NM and AZ based on agency reports and expert knowledge Mexican gartersnake (Thamnophis eques megalops) Location information cited in Rosen and others (2001)Sensitive grassland and riparian/aquatic species Spatial information on species occurrences from Natural Heritage Programs in AZ and NM and Centro de Datos para la Conservación de Sonora; sensitive grassland and riparian-aquatic species and subspecies have global ranks of G1-G3 and T1-T3



onanysubstantialscale,thoughsmallpatchesmightconceivablyberecoveredwithheavyinvestmentofresources. Thespreadofnon-nativeperennialgrasseswithingrasslandshasalsobeensubstantial(table3).Boerlovegrassand,toagreaterextent,Lehmannlovegrassarecommonordominantonatleast1.5millionacressuchthatnon-nativegrasslandswithlittletomoderatewoodyincreasecomprise11%ofthisarea’scurrentandformergrasslands.WhentheAHGAwascompletedin2003,non-nativegrasslandswerelargelyrestrictedtoArizona.However,LehmannlovegrassappearstobespreadingintosouthwesternNewMexicoasitisnowpresentinlong-termmonitoringplotswhereithadnotpreviouslybeenrecorded(P.Sundt2009).Implicationsofthisspreadaremixed,withsomewildlifespeciesmoreimpactedthanothers(Bockandothers1986;Albrechtandothers2008).Nativegrassesremainpresentinmanyinvadedareas,albeitatlowerdensity.Fireregimesandhydrologycanbeaffectedbutarenotasradicallytransformedasinthecasewithmanyplantinvasions(EmmerichandCox1992).

Identification, Delineation, and Evaluation of Priority Landscapes

Participantslargelyagreedonlocationsof“best”remaininggrass-landlandscapes(fig.2),Polygonboundarieswereadjustedbasedonadditionalknowledgeaboutlocationsofvaluedfeatures(e.g.extendingtheJanospolygonnorthintothePlayasValleytoreflectmovementsofawildbisonherd)orongoingconservationefforts(e.g.expansionofMuleshoe-AravaipapolygontoincludeanareaknownastheBonitagrasslandwherelandownersarecombatingshrubinvasion).Expertssuggestedadditionofpolygons(e.g.Buenaventura)toincorporateareasthatmetmanyofthesuggestedcriteriabutwhosevalueshavenotbeenwidelyknownamongpractitionersinthisregion.Thegroupalsorecommendeddroppingtwopolygons(SantaCruzandSanPedro-U.S.)thathadbeenpreviouslydelineatedbutratedlowingrassland-specificvalues(table4).Bothareascontinuetoharborotherhabitatsofhighconservationvalue,particularlyripariansystems,whichmayin turnbenefit fromgrassland restoration activities.Nevertheless,forthepurposesofgrasslandconservationperse,theseareaswereseenasbeinglesslikelythanotherlandscapestohostlargeblocksofgrasslandhabitat intothefuture.PartsoftheinitialSantaCruzpolygonthatstillhavesubstantialgrasslandpatcheswereaddedtotheAltarValleypolygon,withwhichexpertsidentifiedrelativelyhighlandscapeconnectivity(animpressionsubstantiatedbythemulti-yearmovementsofawanderingjaguarknownasMachoB).Intwocases,

participantschosetofurtherrefinepolygonboundariesbyexaminingadditionalinformationaftertheworkshop.OverlayingdraftpolygonsonGoogleEarthprovedespeciallyusefulformodifyingboundariestoexcludehighlymodifiedareassuchascenter-pivotagricultureinChihuahua. The12finalpolygonsincorporatedalmostallthesubstantialblocksofhighest-qualitygrasslandthattheconditionassessmentshadidenti-fiedwithintheregion(83%ofoverallacreageinnativeno-to-lowwoodyincreaseclasses)aswellassubstantialacreageofsurround-ing patches deemed restorable grassland (fig. 2).These polygonsalso succeedat encompassingmanyof theother targetbiologicalfeaturesassociatedwithgrasslands(fig.3,table5).Forexample,allbut two riparian sacatongrasslandpatches identified in grasslandassessmentswereincludedinfinalpolygons.Thetwothatwerenotidentifiedarerelativelyisolatedfromothergrasslandblocks,onebe-ingonthesouthwesternedgeoftheregionwhereterrainchangestohighlydissectedSonoranscrub,andtheotherbeingonthenorthernendwhereterrainrisestowardstheMogollonPlateau.ThelatterisneartheBurroCienega-Hachitapolygonbutisseparatedfromitbyalargeopenpitmine. Delineations of these major grassland landscapes largely con-formedtounitsdefinedbyindividualvalleys.Thisevaluationboreoutpreviousobservationsthatthelargestremainingblocksofopengrasslandtendtobeinmid-elevationvalleybottoms(e.g.SanRafael,Empire-Cienega-Sonoita).Grassyhillscontributesubstantialblocksin some areas (e.g.Tumacacori andSierrita portions of theAltarpolygon). Inothers(NorthPeloncillos,SouthernSulphurSprings,Aravaipa-Muleshoe-Willcox), grassland habitat primarily occursonbajadaorfoothillsterrainabovelowlandsthathaveundergonevegetationand/orlanduseconversions.Weappliedthevalleynamesmostcommonlyusedbylocalcommunitiestorefertothesegrasslandlandscapes.Participantsdiscussedcombiningnearbypolygonsbutdecided that the smaller unitsmore accurately reflect differencesamongnearbypolygonsinenablingconditions,e.g.incommunitycultureordevelopmentthreatsamongnearbypolygons. Infillingouttheevaluationmatrixforthesepolygons,participantslargelyagreedonratings(table4).Wheretherewasinitialdisagree-ment,furtherdiscussionwasusuallyenoughtobringthegrouptoconsensusonafinalrating.Oneexceptioncameintryingtorateanaspectofconservationfeasibilitythatreflectstheinfluencethatactivecommunityandpartnergroupshavebypromotingand/orimplementingconservationmeasuresinagivenlandscape.Participantsagreedontheimportanceofthisfactor,discussedactivitiesofvariouspartner

Table 3—General statistics for grasslands (U.S. and Mexico) in the Sky Island region.

Grassland type # Patches Total acres % All grasslands

No or low woody increase, native grassland 102 2,144,488 15.4No or low woody increase, native savanna 48 478,953 3.5Medium woody increase, native grassland and savanna 138 3,212,191 23.1No or low woody increase, non-native grassland and savanna 11 162,417 1.2Medium woody increase, non-native grassland and savanna 19 1,342,952 9.7High woody increase, former grassland and savanna 185 3,275,463 23.6Mix of low and medium woody increase, native grassland and savanna 26 328,574 2.4Undetermined grassland and savanna 5,764 2,956,650 21.3

Total U.S.-MX Grassland/Savanna 13,901,688



Figure 2—Priority grassland landscapes, showing ecological condition.

groupsandmodifiedsomepolygonboundariestoreflectpartnerwork,butultimatelydecidedthatthisfactorcouldnotbereadilydistilledintoacomparativerating.Inallareas,participantsrecognizedthat(1)additionalinformationorincreasedconservationeffortscouldchangetheseratings,(2)thatall12polygonsholdsubstantialpromiseforconservationofgrasslandsandassociatedspecies,and(3)thatbothopportunitiesandneedsvaryamongtheset. Discussionamongparticipantsalsodrewoutobservationsaboutanumberofecologicalgradientspresentacrosstheregion,addedtoinformationontargetspecies,describedboththreatsandconservation

valuesofparticularlandscapesingreaterdetail,andaddedinformationaboutpartnersandtheirconservationactivities(elaboratedinGoriandothers2012).

Applications for Protection and Restoration

In each of these landscapes, successful grassland conservationwillneedtoincludethreekeycomponents:(1)strongpartnershipswithinthelocalcommunity,whichinturnsupport,(2)landprotec-



Figure 3—Priority grassland landscapes, showing select species and biological features of interest.

tiontopreventfurtherfragmentationofthesurvivinggrasslands,and(3)activeecologicalmanagementtorestoreandmaintaingrasslandhealththroughtime.TheseareaddressedfurtherinGoriandothers(2012),highlightedbelowtoshowthebroadutilityofinformationpresentedhere. Overlayingpolygonsonlandmanagementhighlightstheroleofparticularinstitutionsinsustaininggrasslandsacrosstheregionandwithineachindividuallandscape.Forinstance,thesemapssuggestthatiftheU.S.ForestServicewantstoinvestinmaintainingopengrasslands,thisagencymightfocusonareaswithintheSanRafaelpolygon; if the agency’s goal is to restore recoverable grassland,workingintheAltar-Tumacacorimightprovidethebestopportuni-ties.Offederalagencies,BLMhasaparticularlylargeroletoplayacrosstheU.S.portionofthisregion.Whileeachoftheselandscapesincludesamixofpublicandprivate lands, success in landscapesliketheEmpire-Cienega-Sonoitadependsheavilyonmanagement

effectsonBLMlands.Bycontrast,outcomesinlandscapessuchastheAnimas-SanLuisValleydependalmostentirelyontheactionsofprivatelandowners. Comparingpolygonstomapsoflandmanagementandprotectionstatus(Gorietal2012)highlightsplaceswheregrasslandblocksarevulnerabletofragmentationbyhumaninfrastructureanddisturbance,aswellaskeyopportunitiestoprotectlongtermconnectivityofnaturalvegetationforthemanywildlifespeciesthatareaffectedbymoredramaticlandscapechangessuchasproliferationofroads,houses,mines,or intensiveagriculture.Several jurisdictions, for instance,combinetoprovideprotectionacrossnearlytheentireSanRafaelValleyintheUnitedStates;addingeasementsorotherconservationstatustothelastremaininglargeblockofunprotectedprivatelandat the top of the valleywould secure the ongoing value of thesepreviousinvestments.Successfullycompletinglong-standingeffortstobringpubliclyidentifiedparcelsofArizonaStateTrustlandinto



conservationstatuswouldgreatlybenefitfiveofthe12prioritygrass-landlandscapesidentifiedhere.ConservingtheseStateTrustlandswould,forexample,safeguardthegrasslandblockinthecenteroftheEmpire-Cienega-Sonoita,andsecurewildlifeconnectivityacrosstheI-10corridor,Catalina-RinconMountains,andtheSanPedroRivertotheAravaipa-Muleshoe-Willcoxlandscape. Overlayingpolygonsonmapsofgrasslandhabitatconditionhigh-lightskeyopportunitiestoprotectorrestoreconnectionsforspeciessuchaspronghornwhosemovementsareaffectedbyhabitatchangessuchasshrubencroachment(BrownandOckenfels2007).However,forplanningandimplementingrestorationormanagementinterven-tions,moreinformationisneeded.CloserexaminationofEcologicalSitemaps(Bestelmeyerandothers2009)canprovidemanyinsightsintoconservationvalueandmanagementoptionswithinlandscapes.Finer-scalemappingofecologicalcondition(e.g.byecologicalstate)cantheninformselectionofprojectlocations,treatmentmethods,andmonitoring(Tillerandothers2012). Futureeffortstogatherinformationfromadditionalexpertswouldnodoubtimprovetheresolution,accuracy,andrichnessoftheregionalpicturepresentedhere.Werecognize,forexample,thatchallengesofcollectingdataacrossstateandinternationalboundariescreatein-consistentcoverageforsomecommunitiesandspecies,andwelcomerefinements.ThelargeproportionofgrasslandsinMexicocurrentlydepictedas“unknowncondition,”forexample,highlightstheneedtocompileconsistentinformationabouttheseareas.Weencouragereaderstotreatthisassessment,andotherslikeit,aslivingdocumentstobemodifiedandaddedtoastimegoeson,asecologicalandsocialconditionschange,asspeciesrangesshift,andaswelearnmoreaboutallthesefactors. InreviewingthestatusandtrendsofSkyIslandgrasslands,itisclearthatmaintainingthemasfunctioningsystemsrepresentsoneofthegreatestneeds,andgreatestchallenges,ofanyconservationissueintheborderlands.Thesegrasslandsareanessentiallinkthatsustainsthewildlifeinthemountainsandtheperennialwatersinthevalleybottoms.Yetsuccessfulgrasslandconservation iscomplex,requiring simultaneous progress on several fronts: protecting thelandfromfragmentation,managingthelandtocontrolshrubsandmaintaingrasscover,andsupportingcommunityorganizationsandotherpartnershipsthatgettheworkdone.Wehopethatthisanalysis,combinedwitheffortstomakeprogressonthesefrontsandevalua-tionsofwhatisworkingbest,helpsusallrisetothischallenge.

Acknowledgments Wewouldliketothanktheindividualslistedaboveforexpertinputduringthisanalysis;StevenYanoffforintegratingthetwograsslandassessmentlayers;AnneGondorforhelpaccessingspatialdataforMexico;andthemany,manyexpertswhoprovidedinputintotheAHGAandREA.FundingforthisworkwasprovidedbytheNationalFishandWildlifeFoundation,TheNatureConservancy,PimaCounty,andFreeportMcMoran.

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