San Francisco Bay National Wildlife Refuge Complex Climate Assessment

San Francisco Bay National Wildlife Refuge Complex Climate Assessment California Landscape Conservation Cooperative | USFWS Region 8 Inventory and Monitoring Program | Foundations of Success San Francisco Bay National Wildlife Refuge Complex Climate Assessment Prepared by: California Landscape Conservation Cooperative | USFWS Region 8 Inventory and Monitoring Program | Foundations of Success In support of: USFWS San Francisco Bay National Wildlife Refuge Complex July 2018 The information provided in this document was current as of February, 2017. We recommend reviewing the most recent literature when making conservation decisions. 1 2 TABLE OF CONTENTS INTRODUCTION 5 METHODS 5 Selecting Climate Change Projections 5 Conservation Target Climate Summaries 6 PART I: SUMMARY OF CLIMATE PROJECTIONS 7 Warming temperatures 7 Precipitation changes 7 Increased overall aridity and drought 8 Increased frequency and intensity of extreme heat events 8 Changes in storm patterns 9 Sea level rise 10 Increased coastal flooding events 13 Increasing salinity 13 Sea surface temperatures 13 Changes in upwelling, winds, and ocean productivity 13 Ocean Acidification 16 Potential for changes in fog patterns 17 Species distribution and phenology shifts 20 Climate Change and Non-climate Stressors 20 Refuge-scale Climate Projection Graphs and Data 21 PART II: CONSERVATION TARGET CLIMATE SUMMARIES 22 Breeding Seabirds 22 California Least Tern 24 Coastal Sand Dunes 25 Marine Island Ecosystems 26 3 Riverine Sand Dunes 28 Salamanders Error! Bookmark not defined. Tidal Flats and Open Water 29 Tidal Marshes 31 Vernal Pool Grasslands 32 Waterbirds 33 Work Cited 35 APPENDIX I: PROJECTIONS FOR THE NORTH COMPLEX 44 APPENDIX II: PROJECTIONS FOR THE CENTRAL COMPLEX 63 APPENDIX III: PROJECTIONS FOR THE SOUTH COMPLEX 78 4 Introduction The San Francisco Bay National Wildlife Refuge Complex (hereafter the SFBNWRC) is located on California’s Pacific Coast. SFBNWRC is comprised of seven National Wildlife Refuges (hereafter “Refuges”) in and around San Francisco Bay and Monterey Bay. SFBNWRC administers the following refuges: Antioch Dunes National Wildlife Refuge, Don Edwards San Francisco Bay National Wildlife Refuge, Ellicott Slough National Wildlife Refuge, Farallon National Wildlife Refuge, Marin Islands National Wildlife Refuge, Salinas River National Wildlife Refuge, and San Pablo Bay National Wildlife Refuge. These refuges contain a diverse array of habitat types including dunes, tidal salt marsh, rocky offshore islands, vernal pools, and beaches. SFBNWRC also provides habitat for dozens of threatened and endangered species. In 2017, SFBNWRC staff began the development of a Natural Resource Management Plan (NRMP) that included a detailed analysis of current and potential stresses, threats, and management opportunities. We used these analyses to develop SMART1 conservation objectives for refuges’ conservation targets, and a complex-wide work plan to attain the agreed upon objectives. The information presented in this report was compiled to support the integration of the best available climate change science into the NRMP process. There are two main sections of this report. The first (Part I: Summary of Climate Projections) provides an overview of the anticipated rate, extent, and level of certainty of future physical changes for the planning region. The second section (Part II: Conservation Target Summaries) provides a description of the potential effects of climate stressors on SFBNWRC’s conservation targets. Methods Selecting Climate Change Projections Climate scientists recommend reviewing a range of plausible futures when assessing options and priorities for conservation action. The climate projections presented in Part I are drawn from existing reports, data, and available tools to provide a range of projections of future climate, hydrology, and sea level rise conditions. Global Climate Model (GCM) and greenhouse gas scenario combinations (hereafter “models”) reflect the resources available at the time of this writing. The models sometimes differ across these resources, but the information can still be compared. Some of the sources reference projections from the older CMIP3 (2007) models, such as Cayan et al. (2009 and 2012) and CalAdapt. The more fine-scale data, such as the graphs in the refuge-specific projections, present the CMIP5 (2014) models and greenhouse gas scenarios (RCPs), selecting two GCMs: CNRM ("Warm-Wet") and MIROC-ESM ("Hot-Dry"), combined with the highest greenhouse gas scenario RCP8.5, to characterize a range of potential future conditions under high emissions. These two models are also used in the 2016 CDFW Vegetation Vulnerability Assessment and the 4th California Climate Change Assessment, now in progress. 1 specific, measurable, attainable, realistic, and time-bound 5 Figure 1 below compares the older GFDL A2 model to the two newer models by their end-of-century projections of temperature and precipitation. GFDL A2 is similar in this respect to CNRM RCP8.5 for temperature ("warmer") and to MIROC-ESM RCP8.5 for precipitation ("drier"). Figure 1. A comparison of the end-of-century precipiation and air temperature outputs of the CMIP3 and the CMI5P nodels referenced here. CNRM RCP8.5 projects the highest average precipitation for that 30- year time period, MIROC-ESM RCP 8.5 projects the lowest average precipitation and even higher average temperature, and GFDL A2 falls between the two, projecting a warmer and drier future. The choice of these three models provides a broad range of projections for conservation planning. Source: Weiss, et al., 2013. For more about models, please see this Climate Commons article (still in draft). Conservation Target Climate Summaries There are many pathways through which climate change can effect habitat and wildlife. Climate change drivers (e.g., sea-level rise, drought, extreme storms) can alter the physical structure of habitats (e.g., species composition, hydrology), create conditions that exceed the physiological tolerances of species, or alter the amount of food energy a particular habitat can provide (Walther et al. 2002, McKenney et al. 2007, Notaro et al. 2012, Pearson et al. 2014). In our conservation target climate summaries (Part II: Conservation Target Climate Summaries), we attempt to describe how key climate change drivers may affect SFBNWRC’s eleven conservation targets (hereafter “target”). 6 To develop these summaries, Conservation Measure Partners (www.conservationmeasures.org) and USFWS Region 8 Inventory & Monitoring staff conducted a thorough literature search for physiological tolerances and climate change research for each target. California Landscape Conservation Cooperative staff then reviewed the literature and summarized it to the best of their understanding. When possible, experts were asked to review the climate summaries to ensure accuracy. The conservation target climate summaries are a good starting point and provide key references for further reading. However, we recommend reviewing the most recent literature when making conservation decisions. Part I: Summary of Climate Projections Warming Temperatures • By 2050, California is projected to warm by approximately 2.7°F average annual temperature above 2000 averages, a threefold increase in the rate of warming over the last century. By 2100, average temperatures are projected to increase by 4.1–8.6°F, depending on emissions levels. Springtime warming — a critical influence on snowmelt — will be particularly pronounced (CA Climate Change Center 2012). • By the last 30 years of this century, North Bay scenarios project average minimum temperatures to increase by 0.5 °C to 5.8 °C and average maximum temperatures to increase by 0.9°C to 5.5 °C relative to conditions over the last 30 years (Veloz et al. 2016). Precipitation Changes • Models vary widely in their projections of potential future precipitation patterns, and therefore there is low certainty about future precipitation (Cayan 2009, 2014 California Basin Characterization Model). • Analysis by Cayan et al. (2009) for the second and third California Climate Change Assessments indicates an overall drying trend in California during the 21st century. Some areas in Northern California may experience higher annual rainfall amounts, and potentially larger storm events, but California as a whole, particularly Southern California, are expected to be 15 to 35% drier by 2100. 7 Figure 2. Annual precipitation projected by three models for the San Pablo Bay Watershed with a 30-year running average to show broad trends. Data source: 2014 California Basin Characterization Model. Increased Overall Aridity and Drought • Models with both more and less overall precipitation for the North Bay and Central Coast regions indicate an increase in overall summer dryness even in years of higher-than-average precipitation (Micheli et al. 2012). • Warming temperatures will increase the frequency, intensity, and impacts of drought regardless of the direction of precipitation change (Diffenbaugh et al. 2015, Mann and Glieck 2015). Increased Frequency and Intensity of Extreme Heat Events • Models project a significant rise in the number, intensity, and length of heat waves. In the graph below from CalAdapt, every year in the last quarter of the century is projected to have one or more 5-day periods with temperatures exceeding today's threshold considered extreme for the region. 8 Figure 3. Projected number of extreme heat days for the San Pablo Bay region. You can use the CalAdapt extreme heat tool

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