Proceedings of the Third International Conference on Invasive ...

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<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive SpartinaChapter 3: Ecosystem Effects <strong>of</strong> Invasive SpartinaBay marshes are also larger than marshes in <strong>the</strong> sou<strong>the</strong>rnreach, higher in elevation, have a lower rate <strong>of</strong> subsidencerelative to mean tidal level, and have more emergent marshvegetation (Atwater et al. 1979; Josselyn 1983; GoalsProject 1999; Baye et al. 2000).ONGOING THREATS TO THE CLAPPER RAIL POPULATIONExtensive conversion <strong>of</strong> tidal lands resulting fromhistoric and ongoing pressures <strong>of</strong> agricultural production,urbanization, and salt production has drastically reducedCalifornia clapper rail habitat in <strong>the</strong> San Francisco Estuary(Goals Project 1999; Albertson and Evens 2000). Theremnant tidal marshlands <strong>of</strong> <strong>the</strong> estuary, <strong>the</strong> largest and lastrefuge <strong>of</strong> R.l. obsoletus, occupy only about 12-15% <strong>of</strong> <strong>the</strong>irhistoric extent, yet even in such diminished capacitycomprise more than 90% <strong>of</strong> all remaining California tidalmarshlands (Dedrick 1989; Goals Project 1999). In additionto, and exacerbated by, habitat loss and fragmentation, <strong>the</strong>rail population is vulnerable to a redundancy <strong>of</strong> threats—predation by introduced red fox (Vulpes vulpes); depredation<strong>of</strong> nests and eggs by non-native rodents (Rattus spp.) andinflated populations <strong>of</strong> native mammals (e.g. striped skunk,raccoon); contamination (Lonzarich et al. 1992;Schwarzbach et al. 2006); diminution <strong>of</strong> peripheral refugialvegetation; and sea-level rise. The ecological alteration <strong>of</strong><strong>the</strong> estuary’s tidal marshes by non-native vegetation,especially Spartina alterniflora and its hybrids, and possiblyLepidium (Spautz and Nur 2004), poses yet ano<strong>the</strong>r potentialthreat to an already beleaguered species.Ecologists have found that non-native hybrid cordgrassexceeds <strong>the</strong> narrower niche <strong>of</strong> <strong>the</strong> native tidal marsh plantand predicted that as <strong>the</strong> invasion progresses, hybridSpartina will likely spread to higher and lower elevations(Cohen 2001; Callaway and Josselyn 1992; Daehler andStrong 1996; Collins 2002; Baye 2004). As cordgrass bedsexpand, <strong>the</strong>y are expected to “constrain <strong>the</strong> tidal network”(Collins 2002) and, as <strong>the</strong> culms reach mature densities, <strong>the</strong>stands are apt to become effective sediment traps, promotinginfilling (Baye 2004). Additionally, <strong>the</strong> lower elevationlimits <strong>of</strong> non-native cordgrass “correspond to <strong>the</strong> slumpblocks and lower banks <strong>of</strong> large channels” (Collins 2002),prime clapper rail foraging areas.One <strong>of</strong> <strong>the</strong> forecasts <strong>of</strong> a study on <strong>the</strong> geomorphiceffects <strong>of</strong> non-native cordgrass invasion was that it will tend“to isolate <strong>the</strong> headward reaches <strong>of</strong> first order channelsfrom <strong>the</strong>ir networks,” [in effect] “shortening and simplifyingintertidal channel networks and <strong>the</strong> shoreline <strong>of</strong> <strong>the</strong> Estuaryas a whole” (Collins 2002). This narrow elevational nicheoverlaps almost precisely with habitat that is critical for <strong>the</strong>California clapper rail (Collins et al. 1994; Albertson andEvens 2000). Given <strong>the</strong> importance <strong>of</strong> channel complexity toclapper rails, a reduction in channel density and complexitypredicted for marshes invaded by non-native Spartina(Collins 2002; Ayres et al. 2003; Baye 2004) is likely toreduce <strong>the</strong> availability <strong>of</strong> habitat for clapper rails.RAIL DENSITY AND HABITAT QUALITYThe population estimates reported above suggest thatclapper rails may occur in dramatically higher densities insome invaded marshes than in non-invaded marshes. Thisapparent selection <strong>of</strong> non-native over native habitats by railspredicates a question: Do increased densities <strong>of</strong> rails meanincreased viability <strong>of</strong> rail populations?Some have interpreted <strong>the</strong> density <strong>of</strong> rails detectedwithin non-native Spartina patches as a positive trend forthis highly endangered taxon. However, <strong>the</strong> literaturecautions that density is a misleading indicator <strong>of</strong> habitatquality or reproductive success (VanHorne 1983; Vickery etal. 1992; Pulliam 1996). Given <strong>the</strong> biogeography <strong>of</strong> tidalmarshlands within <strong>the</strong> estuary, and <strong>the</strong> disparity in habitattypes that exists between marshes in its nor<strong>the</strong>rn andsou<strong>the</strong>rn reaches (Josselyn 1983; Goals Project 1999; Bayeet al. 2000) land managers and biologists should consider<strong>the</strong> possibility that non-native Spartina pastures might beecological traps, or perhaps “attractive sinks,” phenomenathat occur most commonly in anthropogenically modifiedhabitats (Delibes et al. 2001; Schlaepfer et al. 2002; Battin2004; Robertson and Hutto 2006). Indeed, San FranciscoEstuary and <strong>the</strong> California clapper rail fulfill most if not all<strong>of</strong> <strong>the</strong> criteria that increase vulnerability <strong>of</strong> animalpopulations to ecological traps summarized by Battin(2004). It is also worth considering <strong>the</strong> possibility that <strong>the</strong>increasing trends in abundance associated with invadedmarshes (east bayshore) and coincident negative trends inless invaded sites (west bayshore) reported in Broom (2008),suggest <strong>the</strong> possibility that rails are being lured away fromhigher quality habitat (larger patch size, age heterogeneity,native Spartina beds ) to occupy falsely attractive habitat.However, <strong>the</strong> supposition that ecological traps account for<strong>the</strong>se apparent trends is open to o<strong>the</strong>r interpretations (Battin2004; Robertson and Hutto 2006; Gilroy and Su<strong>the</strong>rland2007).To determine <strong>the</strong> impact <strong>of</strong> non-native Spartina beds toclapper rail long-term population viability, studiesdetermining reproductive success, survivorship, andpredation rates in both habitat types will be needed. Futurestudies aimed at determining reproductive success ininvaded and non-invaded habitat may help address thisimportant question <strong>of</strong> conservation biology.SUMMARY AND CONCLUSIONSNon-native cordgrass has invaded intertidal marshlandsin <strong>the</strong> San Francisco Estuary, crucial habitat for <strong>the</strong> endemicand endangered California clapper rail. The ecologicaltransformation <strong>of</strong> <strong>the</strong> intertidal marsh zone is apparentlyunderway and future changes are anticipated. Densities <strong>of</strong>rails in invaded habitat appear to be somewhat higher than at- 187 -
Chapter 3: Ecosystem Effects <strong>of</strong> Invasive Spartina<strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> <strong>Third</strong> <strong>International</strong> <strong>Conference</strong> on Invasive Spartinanon-invaded habitat, but <strong>the</strong> ultimate effects on <strong>the</strong>reproductive success and recovery <strong>of</strong> <strong>the</strong> California clapperrail poplation are unknown.The South and Central Bay subpopulations <strong>of</strong> railsoccupy tidal marshes that are undergoing an aggressiveinvasion by non-native cordgrass. The North Bay clapperrail populations occupy marshes that are mostly free <strong>of</strong> nonnativecordgrass. The North Bay is also an area whereextensive marsh restoration efforts are underway or in <strong>the</strong>planning phases (Siegel 2002). These differing situations<strong>of</strong>fer opportunities for:• Non-native cordgrass control in <strong>the</strong> South and Centralbays employing “best management practices” to reduceor minimize impacts to rails, currently in progress by <strong>the</strong> SanFrnacisco Bay Invasive Spartina Project.• Monitoring <strong>of</strong> North Bay marshes for <strong>the</strong> presence <strong>of</strong>non-native cordgrass, particularly in marsh restoration sites.• Control <strong>of</strong> non-native cordgrass in <strong>the</strong> North Bayprior to alteration <strong>of</strong> <strong>the</strong> structure and function <strong>of</strong> <strong>the</strong> habitat.• Research focused on population dynamics <strong>of</strong> rails atdifferent sites (invaded and “pristine”) to determine reproductivesuccess and survivorship.REFERENCESAlbertson, J. and J. Evens. 2000. California Clapper Rail. In:Ol<strong>of</strong>son, P.R., ed. Baylands Ecosystem Species and CommunityPr<strong>of</strong>iles: life histories and environmental requirements <strong>of</strong> keyplants, animals, and wildlife, pp. 332-341. San Francisco BayRegional Water Quality Control Board, Oakland, California.Atwater, B.F., S.G. Conard, J.N. Dowden, C.W. Hedel, R.L.MacDonald, and W. Savage. 1979. History, landforms, and vegetation<strong>of</strong> <strong>the</strong> estuary’s tidal marshes. In: Conomos, T.J., ed. SanFrancisco Bay: <strong>the</strong> urbanized estuary, pp. 348-385. Pacific Division,American Association for <strong>the</strong> Advancement <strong>of</strong> Science. SanFrancisco, California.Avocet Research Associates. 1992. Evaluation <strong>of</strong> impacts <strong>of</strong> NavalRiverine Forces Training Operations on nesting habitat <strong>of</strong> <strong>the</strong>California Clapper Rail at Napa River, California. Report toU.S. Department <strong>of</strong> <strong>the</strong> Navy, Western Division, San Bruno,California.Avocet Research Associates. 2004. California Clapper Rail (Ralluslongirostris obsoletus): breeding season surveys, San Pablo Bayand tributaries—2004. Final report to Marin Audubon Societyfrom Avocet Research associates.Ayres, D.R., D.R. Strong, and P. Baye. 2003. Spartina foliosa(Poaceae)—A common species on <strong>the</strong> road to rarity? Madrono50:209-213.Battin, J. 2004. When good animals love bad habitats: Ecologicaltraps and <strong>the</strong> conservation <strong>of</strong> animal populations. ConservationBiology 18: 1482-1491.Baye, P., P.M. Faber, and B. Grewell. 2000. Tidal marsh plants <strong>of</strong><strong>the</strong> San Francisco Estuary. In: Ol<strong>of</strong>son, P.R., ed. Baylands EcosystemSpecies and Community Pr<strong>of</strong>iles: life histories and environmentalrequirements <strong>of</strong> key plants, animals, and wildlife, pp.9-67. San Francisco Bay Regional Water Quality Control Board,Oakland, California.Baye, P. 2004. A Review and Assessment <strong>of</strong> Potential Long-termEcological Consequences <strong>of</strong> <strong>the</strong> Introduced Cordgrass Spartinaalternifora in <strong>the</strong> San Francisco Estuary. Draft ms.Broom, J. 2008. Regional Trends in California Clapper RailAbundance at Non-native Spartina-invaded Sites in <strong>the</strong> SanFrancisco Estuary from 2005 to 2007. Report prepared by Ol<strong>of</strong>sonEnvironmental, Inc. for <strong>the</strong> State Coastal Conservancy.http://www.spartina.org/project_documents/clapper_rails/CLRA_Trends_2005-07(web).pdf.Callaway, J.C., and M.N. Josselyn. 1992. The introduction andspread <strong>of</strong> smooth cordgrass (Spartina alterniflora) in South SanFrancisco Bay. Estuaries 15(2):218-226.Cohen, A.N. 2001. Conservation management <strong>of</strong> exotic cordgrassin <strong>the</strong> Pacific coast salt marshes: preserving clapper rails vs.preserving <strong>the</strong> clapper rail. Abstract for Second Symposium onMarine Conservation Biology. San Francisco state University,June 21-26, 2001.Collins, J. 2002. Invasion <strong>of</strong> San Francisco Bay by SmoothCordgrass, Spartina alterniflora: a forecast <strong>of</strong> geomorphic effectson <strong>the</strong> intertidal zone. Report prepared for U.S. EPA Region9.Collins, J.N., J.G. Evens, and B. Grewell. 1994. A synoptic survey<strong>of</strong> <strong>the</strong> distribution and abundance <strong>of</strong> <strong>the</strong> California Clapper Rail,Rallus longirostris obsoletus, in <strong>the</strong> nor<strong>the</strong>rn reaches <strong>of</strong> <strong>the</strong> SanFrancisco Estuary during <strong>the</strong> 1992 and 1993 breeding seasons.Draft Technical Report to California Department <strong>of</strong> Fish andGame (8/1/94).Conomos, T.J., ed. 1979. San Francisco Bay: The UrbanizedEstuary. http://www.estuaryarchive.org/archive/conomos_1979.Daehler, C.C. and D.R. Strong. 1996. Status, prediction, andprevention <strong>of</strong> introduced cordgrass Spartina spp. invasions inPacific estuaries, USA. Biological Conservation 78:51-58.Dedrick, K. 1989. San Francisco bay tidal marshland acreages:recent and historic values. <strong>Proceedings</strong> <strong>of</strong> <strong>the</strong> 6 th Symposium inCoastal and Ocean Management (Coastal Zone 1989). Am. Soc.Of Engineers, pp. 383-398.Delibes, M., P. Gaona, and P. Ferreras. 2001. Effects <strong>of</strong> an attractivesink leading into maladaptive habitat selection. AmericanNaturalist 158: 277-285.Estrella, S. California Clapper Rail and California Black Rail:Suisun Marsh Survey 2007. California Department <strong>of</strong> Fish andGame Bay-Delta Region. Report to California Department <strong>of</strong>Water Resources. Contract #4600004374.Evens, J.G. and G.W. Page. 1987. Clapper rail populations atCorte Madera Creek, Muzzi Marsh, San Clemente Creek, andTriangle Marsh, Marin County, California. Report to MarinAudubon Society from Point Reyes Bird Observatory.Evens, J.G. and J.N. Collins. 1992. Distribution, abundance, andhabitat affinities <strong>of</strong> <strong>the</strong> California Clapper Rail, Rallus longirostrisobsoletus, in <strong>the</strong> nor<strong>the</strong>rn reaches <strong>of</strong> <strong>the</strong> San FranciscoEstuary during <strong>the</strong> 1992 breeding season. Report by AvocetResearch Associates to California Department <strong>of</strong> Fish and Game.Gill, R. 1979. Status and distribution <strong>of</strong> <strong>the</strong> California Clapper Rail(Rallus longirostris obsoletus). California Fish and Game 65:36-49.Gilroy, J.J. and W.J. Su<strong>the</strong>rland. 2007. Beyond ecological traps:perceptual errors and undervalued resources. Trends in Ecologyand Evolution 22(7):351-6.Goals Project. 1999. Baylands ecosystem habitat goals. A report <strong>of</strong>habitat recommendations prepared by <strong>the</strong> San Francisco BayArea Wetlands Ecosystem Goals Project. USEPA, San Francisco/SFBRWQCB,Oakland, CA.Grinnell, J. and A. Miller. 1944. Distribution <strong>of</strong> <strong>the</strong> Birds <strong>of</strong>California. Pacific Coast Avifauna No. 27.Herzog, M., L. Liu, J. Evens, N. Nur, and N. Warnock. 2005.Temporal and spatial patterns in population trends in California- 188 -
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FORWARD & ACKNOWLEDGEMENTSThe <stro
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CHAPTER ONESpartina Biology
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Chapter 1: Spartina Biology
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