Appendix G POINT BLUE CONSERVATION SCIENCE FINAL REPORT Natural resource vulnerabilities, potential adaptation strategies, and monitoring framework for Marin County’s outer coast sea level rise vulnerability assessment January 2017, Final Report Prepared for the Marin County Community Development Agency Natural resource vulnerabilities, potential adaptation strategies, and monitoring framework for Marin County’s outer coast sea level rise vulnerability assessment January 2017, Final Report Point Blue Conservation Science M. Hayden, S. Veloz, L. Salas, D. Jongsomjit, N. Nur Prepared for the Marin County Community Development Agency Suggested Citation Point Blue Conservation Science. 2016. Natural resource vulnerabilities, potential adaptation strategies, and monitoring framework for Marin County’s outer coast sea level rise vulnerability assessment. Prepared for the Marin County Community Development Agency. 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Cover photo credit: Cory Gregory 1 TABLE OF CONTENTS PURPOSE AND SCOPE ................................................................................................................................... 3 STUDY AREA .................................................................................................................................................. 3 SUMMARY OF VULNERABILITIES .................................................................................................................. 5 NATURAL RESOURCE VULNERABILITY ASSESSMENT .................................................................................... 6 Natural land cover..................................................................................................................................... 6 Critical habitat for federally listed species ................................................................................................ 6 Other listed species ................................................................................................................................. 11 Projected marsh bird response to estuary evolution ............................................................................. 11 Eelgrass ................................................................................................................................................... 15 Pinniped haul outs .................................................................................................................................. 19 Seabird colonies ...................................................................................................................................... 20 ADAPTATION STRATEGIES ........................................................................................................................... 21 MONITORING FRAMEWORK ....................................................................................................................... 26 Hypotheses of future change .................................................................................................................. 26 Monitoring ecosystem change ................................................................................................................ 26 Target species population trends ........................................................................................................... 27 Design monitoring program .................................................................................................................... 29 Evaluate monitoring costs relative to goals ............................................................................................ 29 REFERENCES CITED ...................................................................................................................................... 30 APPENDIX A - ADDITIONAL INFORMATION ON LISTED SPECIES ................................................................. 32 APPENDIX B - SEABIRD COLONY VULNERABILITY ....................................................................................... 34 APPENDIX C - DEVELOPING A CLIMATE ADAPTATION MONITORING PROGRAM ...................................... 35 2 PURPOSE AND SCOPE This assessment was intended to assist Marin County in identifying site-specific vulnerability of natural resource assets to sea level rise and coastal erosion, to provide nature-based adaptation strategy suggestions to address identified natural resource vulnerabilities, and to provide a framework for monitoring of potential strategies. The goal was to further inform Marin County’s sea level rise vulnerability assessment for the outer coast (C-SMART). Our analysis was limited to available geospatial data of mapped natural resource assets and existing modeling of projected hazards including (1) flood extent and depth from the Our Coast, Our Future project, (2) marsh elevation capital projections (projected evolution of estuary habitat) completed by ESA (2015), and (3) beach/cliff erosion projections for select areas also completed by ESA (2015). Natural resource assets analyzed include: Habitat - based on land cover from NOAA’s Coastal Change Analysis Program Terrestrial state- and federally-listed species Tidal marsh bird indicator species (response to projected estuary evolution) Eelgrass beds Mammal haul-outs Seabird colonies If a natural resource asset was not included, this is likely a reflection of lack of appropriate geospatial data and should not be assumed to mean it bears no risk. This is particularly true for aquatic species. For example, no spatial data were available for wild oyster or mussel beds. Certain aquatic species such as fish (i.e., coho salmon, longfin smelt, and tidewater goby) were not assessed given lack of modeling that appropriately reflects projected future habitat shifts. STUDY AREA The study area encompasses non-federal lands within Marin County’s Coastal Zone boundary and areas immediately offshore (Figure 1), including Tomales Bay and Bolinas Lagoon. Federal lands were not included because Marin County has no jurisdictional authority. In some cases (e.g., listed species), federal lands were included for context and this is noted accordingly. 3 Figure 1. Study region extent. 4 SUMMARY OF VULNERABILITIES There are three key regions within the study area that have natural resource assets at risk: Dillon Beach, Tomales Bay, and Bolinas Lagoon/Sea Drift. Table 1 presents a summary of the natural resource assets that are particularly at risk, based on our limited analysis. For most assets, the vulnerability will be mediated depending on the availability of upslope accommodation space and the ability of the asset to migrate in pace with sea level rise. For example, Bolinas Lagoon is an important estuary but is topographically confined. The lack of upland accommodation space makes vegetated marsh habitat particularly at risk from sea level rise. Table 1. Summary of key natural resource vulnerabilities. Region Dillon Beach Tomales Bay Bolinas Lagoon/Beach Natural Resource Beach/dune habitat Eelgrass beds Vegetated marsh Assets Particularly Critical habitat for the Two large estuary habitat at Risk endangered Western complexes with Pinniped haul-out sites Snowy Plover associated plants and Western Snowy Plover Last remaining natural wildlife habitat population of Showy Pinniped haul-out Rancheria Clover sites Primary Hazards Coastal erosion and/or Permanent Permanent inundation and Vulnerabilities inundation from sea level inundation from sea from sea level rise or rise level rise or changes changes in wave in wave exposure, exposure. with potentially Lagoon is limited upslope topographically accommodation confined so upland space accommodation space severely limited Beach erosion 5 NATURAL RESOURCE VULNERABILITY ASSESSMENT Natural land cover Natural lands within the study area are predominately grassland and other upland vegetation types (Table 2). These upland types are projected to be minimally affected (≤ 1%) by inundation from sea level rise (Table 2), reflecting the steep topography of much of Marin’s outer coast. Habitats at the land-water interface (e.g., beaches and coastal wetlands) are most exposed to potential inundation resulting from sea level rise. While the total spatial extent of these habitats is small relative to upland types, they tend to support a disproportionate number of endemic species (e.g., tidewater goby, black rail) and high species diversity (Hutto et al. 2015). The Unconsolidated Shore cover class includes sandy beach-dune habitat at Dillon and Stinson/Seadrift beaches, as well as rocky shoreline between Rocky Point and Slide Ranch. Tidal, higher salinity wetland types (Estuarine cover classes) are concentrated around Bolinas Lagoon and the deltas of Lagunitas and Walker creeks in Tomales Bay. Freshwater (Palustrine) wetland types are concentrated around creeks draining into Bolinas Lagoon and the eastern side of Tomales Bay. Approximately 1/3 of habitats at the land-water interface are projected to be inundated with 200cm of sea level rise (Table 2). The potential site-specific effects of this on key species is discussed in more detail below. Table 2. Total area of natural land classes within the study area, and