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

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.

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

Riverine Sand Dunes 28

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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

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”).

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.

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.

Figure 3. Projected number of extreme heat days for the San Pablo Bay region. You can use the CalAdapt extreme heat tool to explore the data further. Changes in Storm Patterns

• In addition to the increase in average coastal winds during spring, summer, and fall, data from the San Francisco tide gauge (from 1858 to 2000) show an increase in intense winter storms since 1950, consistent with an observed increase in the largest waves (see section 3.3.2 Waves). Coastal flooding events that were previously 1-in-100 year events are now projected to occur with a probability of 1-in-10 years (Largier et al. 2010).

• Most models under an A2 greenhouse-gas scenario indicate that years with many atmospheric river (AR) episodes increase, ARs with higher-than-historical water-vapor transport rates increase, and AR storm-temperatures increase. These changes raise the potential for more intense runoff and flooding (Dettinger 2011).

• Reduced Sierra snowpack will result in stronger winter runoff events and reduced spring runoff through San Francisco Bay (Largier et al. 2010).

• The combination of climate change trends with El Niño and Pacific Decadal Oscillation (PDO) variability may create new extreme conditions or temporarily mask the effects of climate change, yielding periods in which climate change appears to have stalled only to be followed by years of apparently rapid climate change (Largier et al. 2010).

Sea Level Rise

• Local rates of observed sea level rise (SLR) in San Francisco Bay estuary have been 2.2 centimeters per decade for a total of 19.3 cm between 1900 and 2000 (Griggs et al. 2017).

• Sea level along the California coast, south of Cape Mendocino, is projected to rise 4-30 cm (2-12 in) by 2030, relative to 2000 levels; 12-61 cm (5-24 in) by 2050; and 42-167 cm (17-66 in) by 2100 (NRC 2012).

• Inundation and other impacts associated with rising sea level at a given location is influenced by storm surge, El Niño events’ effects on temperature, and wave run-up. Future increases in the extremes of these factors is expected (Largier et al. 2010).

• Future SLR projections for San Francisco Bay varies; the tables below are the most current projections at the time of this writing, provided by the state of California (Griggs et al. 2017).

Figure 4. Projected sea-level rise (measured in feet) for a tide gauge location in San Francisco, CA (Griggs

10 et al. 2017).

Figure 5. Probability that sea-level rise at San Francisco, Golden Gate, will meet or exceed a particular height (feet) in a given year under: (a) RCP 8.5, and (b) RCP 2.6. (Griggs et al. 2017).

Figure 6. Historic sea levels at the San Francisco tide gauge compared with the future projections presented in the report Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future. The extremes recorded in 1983 and 1997 correspond to El Niño events, which also brought multiple strong storms with high wind, heavy rain, flooding, and extensive coastal damage. You can go to the dynamic tool to the San Francisco BayKeeper website to explore the data further.

Figure 7. Comparison of six different projections of sea level rise for (top) the time frame for reaching a 25 cm increase, and (bottom) the range of increase in sea level reached at the year 2030. You can go to this tool on the Our Coast, Our Future website to explore the data further.

Increased Coastal Flooding Events

• Extreme flooding events that are currently considered 100-year events are projected to occur as frequently as every year, starting as early as the year 2050 (Cayan et al. 2012, Knowles 2009).

• An increasing tendency for heightened sea level events to persist for longer hours is expected, which implies a greater threat of coastal erosion and other damage (Cayan et al. 2012).

• The rise in average global sea surface temperature has been accompanied by an increased frequency of El Niño-Southern Oscillation events (events of warm Pacific ocean surface temperature coupled with high air surface pressure that affect global weather patterns) (Bettencourt et al. 2006).

Increasing Salinity

• An increase in water salinity levels is expected in the San Francisco Bay as a result of sea-level rise, decreasing precipitation, runoff, and snowmelt contribution to runoff that feed tributaries entering the Bay (Cloern et al. 2011).

• Salinity levels are projected to increase by 0.33 to 0.46 practical salinity units (psu) per decade in Northern San Francisco Bay. These salinity increases will in turn affect soil salinity in the transition zone (Veloz et al. 2016).

• Sea level rise may also increase salinity in the San Francisco delta by as much as 9 psu, particularly during drought and if the period of seasonal low freshwater flow expands as models suggest (Knowles and Cayan 2002).

• Lower ecosystem productivity from salinity increases will affect both primary and detrital-based food webs. Such changes will cascade via the food webs into invertebrate, bird, and pelagic systems. Biodiversity of the tidal wetland system in the San Francisco Bay-Delta region is expected to decline, with subsequent effects on ecosystem functioning and services. Altered plant production, physiological tolerances, and shifts in rates of mortality will modify wetland plant communities in ways not yet predictable (Parker et al. 2011).

Sea Surface Temperatures

• Surface ocean temperatures have increased in the North Pacific, offshore of the north- central California continental shelf. This increase in temperature has significant effects on water column structure (i.e., stratification), sea level rise, and ocean circulation patterns (Largier et al. 2010).

• While sea temperature also appears to have increased in shallow bays, estuaries, and sheltered nearshore locations, waters over the north-central California continental shelf have cooled over the last 30 years (by as much as 1°C in some locations) due to stronger and/or more persistent upwelling winds during spring, summer, and fall (Largier et al. 2010).

Changes in Upwelling, Winds, and Ocean Productivity

• Global sea surface temperatures have been rising and are projected to continue rising as much as 2°C by the end of the century (IPCC). However, it is not known how sea surface temperatures will respond in our region, as wind behavior and freshwater runoff are factors (Largier et al. 2010).

• Wind intensity has been increasing in the region (Largier et al. 2010).

• Increases in spring and summer upwelling intensity, and associated increases in the rate of offshore advection, are expected. While this could counter effects of habitat warming, it could also lead to more frequent hypoxic events and lower densities of suitable-sized food particles for fish larvae (Bakun et al. 2015).

• The seasonal timing of upwelling is expected to vary due to climate change. This will have numerous ecological impacts due to mismatches between the timing of upwelling-induced primary production and the less-variable seasonal phenology of higher trophic levels. Changes in these phenomena and their resulting effects on marine populations are expected, but projections are uncertain (Largier et al. 2010).

• Based on potential changes in sea surface temperatures, wind, and productivity patterns, there are expected to be shifts in the distribution of diving foraging seabirds: a decrease in the Channel Islands region, and an increase from San Francisco to Oregon (Point Blue Conservation Science, unpublished).

• Marine mammals and seabirds that are tied to sparsely distributed nesting or resting grounds could experience difficulties in obtaining prey resources, or could respond adaptively by moving to more favorable biogeographic provinces (Bakun et al. 2015).

Figure 8. Illustration of anticipated climate change impacts on the eastern boundary upwelling system (EBUS). A) Global chlorophyll-a annual average concentrations and the locations of major coastal upwelling zones. B) Present state of coastal upwelling zones with the California Current as an example. C) Potential future state of coastal upwelling zones with the California Current as an example (from Bakun et al. 2015).

Figure 9. Projected future foraging seabird hotspots (Dick et al. In Prep, from Point Blue). Ocean Acidification

• Rising atmospheric CO2 concentrations cause a corresponding increase in ocean carbonic acid (H2CO3), resulting in increased hydrogen ion concentrations ([H+]), which leads to a decrease in pH and decreased carbonate ion concentrations. Carbonate ion is essential to the formation of calcium carbonate minerals that make up the shells and skeletons of many marine taxa; decreases in carbonate ion concentrations could have severe consequences for these organisms (Largier et al. 2010).

• Studies suggest that there are a variety of other potential impacts of ocean acidification and its combination with warming temperatures on other organisms (Petkewich 2009, Munday et al. 2009, Rosa and Seibel 2008).

• Ocean acidification will likely impact plankton organisms, which will cause effects at higher trophic levels, although the implications to food webs are poorly understood (Largier et al. 2010).

Potential for Changes in Fog Patterns

• Fog has a profound influence over summertime microclimate where it has been historically prevalent. Reductions in number of hours per day with fog and low cloud cover will exacerbate the warming and drying trends expected under climate change (Personal comm., Alicia Torregrosa 2017).

• Summertime coastal fog frequency is patchy in the SF NWR complex due to the strong influence of topography on the prevailing winds. Areas in the wind shadow of high elevation features have significantly less fog than areas facing the NW wind direction (Personal comm., Alicia Torregrosa 2017). Wind intensity has been increasing in the region (Largier et al. 2010).

• Fog frequency in summertime (June, July, August) has decreased over the last century by as much as 33% (Johnstone and Dawson 2010). The ocean-atmosphere oscillations, such as the Pacific Decadal Oscillation, may be a strong factor in this decline (Personal comm., Alicia Torregrosa 2017).

• Future projections suggest a continued decrease in fog for the late 21st century in Northern California. Incomplete understanding of the strength of fog forming interactions between atmospheric, oceanic, and terrestrial process leads to high uncertainty in these projections (O'Brien 2011).

Figure 10. Summertime frequency of fog cover from two sources, Johnstone and Dawson (2010), identified as JD 2010, and O'Brien 2011, for 1900 - 2070, adapted from figure 6.3 O'Brien 2011. The solid black trend line shows the regression based on Arcata and Monterey airport records (1950 - 2008) extrapolated. The dotted trend line is the result of the statistical model that uses a principal component analysis of the 17

contrast between inland and coastal temperatures and correlation with observed airport records. The dashed trendline is the physics-based O'Brien model (RegCM-UW driven by 20CV2 reanalysis - see O'Brien 2011 for details). The curved lines are the model outputs on an annual average summertime interval for the O'Brien model (blue) and the Johnstone and Dawson model (red). Graph prepared by Alicia Torregrosa.

Figure 11. Average hours per day of summertime fog and low cloud cover, 1999-2009. Map provided by Alicia Torregrosa.

Species Distribution and Phenology Shifts

• Changes in phenology – the timing of seasonal biological events (e.g., leaf-out, pollen and nectar release, migration, and reproduction) – is closely tied to local weather patterns and constitute one of the most proximate responses to climate change (USA National Phenology Network).

• Ecological changes in the phenology and distribution of plants and animals are occurring in all well-studied marine, freshwater, and terrestrial groups, and these shifts have been highly correlated with anthropogenic climate change (Walther et al. 2002, Parmesan 2006).

• Climate change is advancing spring onset, one indicator of ecological change, across the US National Park System (Monahan et al. 2016, National Parks Service). Spring onset varies spatially — while it was 2-3 weeks earlier than a long-term average in the South, Great Basin, Great Plains, Midwest, and mid-Atlantic, many regions in west coast states were 1-3 weeks late (USA National Phenology Network). See map below.

• Phenology shifts could cause a decoupling of food source availability and the species life-cycle events that rely on them, and other important mutualisms such as plant-pollinator interactions (Hegland et al. 2009).

• The USA National Phenology Network provides a web map that allows managers to track how the current year's spring indices, such as first leaf and bloom, compare to 30-year averages. See these helpful tutorials if you would like to explore this topic further.

Figure 12. Spring leaf index anomaly for 2017, a way of measuring seasonal change, from the US National Phenology Network. See more about this map here: https://www.usanpn.org/data/spring.

Climate Change and Non-climate Stressors

Multiple stressors may interact to produce unexpectedly severe impacts on biodiversity and ecosystem health. Additional stressors within the study region include pollution, invasive species, fishing, disease, habitat modification, wildlife disturbance, and development of infrastructure along the coast and at sea.

Refuge-scale Climate Projection Graphs and Data To provide more geographically-focused graphs and maps for the Refuges, data was extracted and summarized for the three sub-regions of the Complex, indicated by the map below. These write ups are provided as Appendices I-III.

Figure 13. Three sub-regions of the Complex.

Part II: Conservation Target Climate Summaries

Breeding Seabirds Summary Projected changes in the marine environment associated with climate change are expected to have substantial impacts on seabird populations. These changes include rising sea surface temperatures, ocean acidification, and changes in timing and strength of upwelling and ocean circulation patterns. Disruptions in the food web and changes in the timing of physical processes in the marine environment resulting from these climate changes appear to already be leading to changes in seabird reproductive success and survival. Seabird population metrics, as well as distributions, appear to be shifting in response to changes in the locations of high-productivity areas and other conditions. There have been radical swings in ocean conditions and seabird populations observed in recent years, with some seabird species (such as Brandt's cormorant) crashing dramatically and important prey (such as juvenile rockfish) increasing to record numbers. Marine ecosystems are complex; it is difficult to assign causality and, therefore, to make projections for the future due to the effects of long-term cycles overlain on shorter-term patterns. However, recent studies indicate that climate change is playing a significant role in the changes observed.

Sea Surface Temperatures, El Niño, Ocean Acidification Food supply for seabirds is likely to become less reliably available due to rising sea surface temperatures, increased frequency of El Niño events, and ocean acidification.

Zooplankton species are important prey for some seabirds and for the forage fish that make up a large portion of the diet of many seabird species. Zooplankton declines have been associated with rising sea surface temperatures (Hill 1995, Roemmich and McGowan 1995), and it is believed these declines can be linked to poor reproductive success and poor survival in some seabirds (Abraham and Sydeman 2004, Lee et al. 2007, Jahncke et al. 2008). The effect is especially dramatic during El Niño events that are likely to become more frequent in the future (Largier et al. 2010). Strong El Niño events have been linked to reduced breeding and success, while strong La Niña years enhance survival and reproduction in Cassin’s auklet, a krill-feeding species (Lee et al. 2007). Low adult survival and low seabird productivity that occurs frequently or over many years will ultimately lead to declines in breeding populations (Lee et al. 2007).

Ocean acidification is likely to affect many aspects marine organism health, including biochemistry, development, behavior, and reproduction. It may also cause effects at all trophic levels, although the implications to food webs are poorly understood and difficult to project. Studies suggest that there are a variety of potential impacts of ocean acidification and its combination with warming temperatures on a wide variety of organisms (Rosa and Seibel 2008, Munday et al. 2009, Petkewich 2009).

Changes in Upwelling Distributions of "trophic hotspots" (temporary locations of high productivity of marine forage species, such as krill and schooling fish) in the southern California Current Ecosystem result from interactions

between a strong upwelling center and a productive retention zone with enhanced nutrients, which concentrate prey and predators across multiple trophic levels (Santora et al. 2017). Changes in strength and timing of upwelling contribute to changes in the locations and timing of these hotspots, and these changes impact the ability of seabirds to find food, affecting adult survival and breeding success.

Increases in spring and summer upwelling intensity and associated increases in the rate of offshore advection are expected (Largier et al. 2010). Both strong and weak upwelling events have been observed in recent years; upwelling was weak and delayed in 2005-06 and 2010, and strong upwelling conditions occurred in the early months of 2007-09 and 2012-13 (Elliott and Jahncke 2015). Strong upwelling is generally associated with high seabird reproductive success because of its positive effect on ocean productivity (Ainley et al. 1995, Abraham and Sydeman 2004, Jahncke et al. 2008). However, the effect of a long-term increase in frequency and intensity of upwelling events could have unpredictable effects, such as more frequent hypoxic events and reduction of food supply for larval fish (Cury and Roy 1989, Bakun et al. 2015). Abraham and Sydeman (2004) found that breeding can also be delayed when upwelling is unusually strong at the time of spring transition. Late breeding is generally associated with poor seabird reproductive success (Ainley et al. 1995, Sydeman et al. 2001, Sydeman et al. 2006, Jahncke et al. 2008) and could ultimately lead to declining breeding populations in the region.

There has been an increase in the frequency of years with early onset of spring transition, which marks the beginning of the upwelling season, over the past decade (Elliott and Jahncke 2015), with the exceptions of 2005 and 2010 showing late spring transition. Earlier spring transition dates are linked to greater productivity in our regional marine ecosystem, while late spring transition is associated with poor ocean productivity, low krill abundance, and late seabird breeding (Abraham and Sydeman 2004, Jahncke et al. 2008). Spring transition, strong upwelling events, and reproductive events could occur out of sync, putting seabird species at risk by decoupling food production with the need for food for reproduction (Largier et al. 2010).

More rapid and extreme changes in general, which are projected as a result of climate change, could increase the probability that food resources will not occur where and when seabirds expect them to be, putting pressures on social and behavioral traits. One study suggests that seabirds are vulnerable to abrupt environmental changes and can fall victim to "ecological traps" that cannot sustain a population (Grémillet and Boulinier 2009).

Changing Seabird Population Distributions Seabird population ranges, densities, and diversity are likely to shift in response to a changing climate and appear already to be responding to climate change. For example, there have been observations of declines of cold-water seabird densities in the southern California Current ecosystem (off the coast of Southern California) and increases in seabird densities and species richness in the northern part of the region (offshore of Washington state), implying a northward range expansion for some seabird species (Sydeman et al. 2009). These changes in seabird distributions are being correlated with the influences of climate change. Sydeman et al. (2009) report significant increases in variance (variability) of Cassin's auklet productivity, which, based on data quantifying krill populations in the region, appear to reflect fluctuations in the primary food source for auklets. Farallon Island’s auklet population has declined severely (by ~80%) over the past 30 years (Lee et al. 2008). By contrast, Brandt's cormorants have shown contrasting population trends—increasing productivity and decreased variance—possibly due to their fish-based diets and a more stable prey base over that time period.

Long-term studies of seabird distribution and abundance have highlighted the importance of mesoscale oceanographic features (fronts, eddies) that influence the locations of enhanced primary and secondary productivity as well as attract and/or concentrate the larger prey that seabirds feed on (Ainley et al. 2005, Yen et al. 2006). Changes in ocean circulation and seabird properties will change the habitat and make different phytoplankton, zooplankton, and fish available, possibly at different geographic locations and depths. The new prey or depths may not be suitable to existing wildlife and may result in population distribution changes (Manugian et al. 2015). Seabird species that are tied to sparsely distributed nesting or resting grounds may experience difficulties in obtaining food, or they might adapt by moving to more favorable locations (Bakun et al. 2015). One model projects a shift in the distribution of diving foraging seabird "hotspots" based on potential changes in sea surface temperatures, wind, and productivity patterns, in particular suggesting a decrease in the Channel Islands region and an increase between the waters offshore of San Francisco to the Oregon coast (Point Blue Conservation Science, unpublished).

Vulnerability to Climate Change Gardali et al. (2012) determined vulnerability and climate priority rankings for 358 bird taxa in California. Species ranked as Climate Priority 3 (low priority) are those with vulnerability scores ≥30 and <40, ≥40 and <45 are ranked as Climate Priority 2 (moderate priority), and ≥45 are ranked as Climate Priority 1 (high priority). Below are seabirds that fell into these priority rankings based on the assessment of their vulnerability to climate change. Please see "A Climate Change Vulnerability Assessment of California's At-Risk Birds" (Gardali et al. 2012) for more information.

Climate Priority 1: California Least Tern Climate Priority 2: Brandt’s Cormorant, Pelagic Cormorant, Pigeon Guillemot, Common Murre, Cassin’s Auklet, Rhinoceros Auklet, Tufted Puffin Climate Priority 3: Double-crested Cormorant

California Least Tern Summary Climate variation influences bird populations both in their breeding and non-breeding areas by affecting important demographic processes, such as breeding success and survival. Increased frequency and intensity of storms, heat exposure, and ocean acidification could negatively impact California least tern feeding and breeding in the San Francisco Bay area.

In the vulnerability and climate priority rankings determined by Gardali et al. (2012), California least tern was the only seabird listed as a Climate Priority 1 (high priority), meaning it had a vulnerability score ≥45.

Increased Temperatures, Extreme Heat Large scale direct mortality of California least tern (Sternula antillarum, CALT) chicks has been documented (Overstreet and Rehak 1982). In 1980, nearly all of several hundred chicks of the least tern chicks within a narrow beach nesting area about 900 m long in eastern Gulfpor .t, Mississippi, died during a heatwave (25 June to 1 July) (Overstreet and Rehak 1982). Necropsies and lab tests confirmed that deaths were caused by heat stroke (Overstreet and Rehak 1982). Recorded means of daily maximum, average, and minimum air temperatures for those 7 days were 35.5, 30.3, and

25.1°C, and daily highs recorded humidity levels ranging from 72–98% and averaging 85.6% (Overstreet and Rehak 1982).

Changing Ocean Conditions and Prey Availability CALT typically forage over short distances in calm, narrow estuaries or large bays, and occasionally in the open ocean. Changing ocean conditions, including changes in sea surface temperatures, El Niño, ocean acidification, and upwelling, both directly and indirectly affectd prey quality and availability. The CALT’s diet consists exclusively of fish, and multiple studies have linked CALT breeding productivity to diet (Elliot, Hurt, and Sudeman 2007; Robinette et al. 2015). Northern anchovies and juvenile rockfish are thought to be indicators of a high quality diet (Elliot, Hurt, and Sudeman 2007; Robinette et al. 2015). Diets high in larval fish and Pacific saury may indicate poor quality diet (Coomber 2013).

How changing ocean conditions will affect fish species, and in turn CALT, is an area of active research. For example, Robinette et al. (2013) found the occurrence of anchovies in CALT diet to be correlated with the Pacific Decadal Oscillation, while the occurrence of rockfish was found to be correlated with local sea surface temperature. We recommend that decision makers consult the most current literature when making decisions because this area of research is evolving so rapidly.

Please also refer to the Sea Surface Temperatures, El Niño, Ocean Acidification, and Changes in Upwelling sections of the Breeding Seabirds Climate Summary for information about potential impacts from those climate factors.

Coastal Sand Dunes Nested targets: Central dune scrub, Smith's blue butterfly (Euphilotes enoptes smithi), western snowy plover (Charadrius alexandrines nivosus), Antioch Dunes evening primrose (Oenothera deltoides subsp. howellii), Contra Costa wallflower (Erysimum capitatum var. capitatum).

Summary While loss of habitat is the most pressing concern for dune plant and insect species (Xerces Society), climate change related impacts are also primary concerns. Sea level rise, combined with more extreme storms, coastal flooding, and increased El Niño events, is likely to cause accelerated shoreline erosion and destruction of habitat in coastal sand dune ecosystems. These threats are exacerbated by existing non-climate causes of coastal sand dune habitat loss, including development on landward side of beach, off-road vehicles, grooming, intense forms of beach use, pollution, structures that impact sand storage and transport (e.g., breakwaters), and urbanization of coastlines. Sand dune plant and insect communities may be further impacted by changes in phenology and loss of food species.

Sea Level Rise and Coastal Erosion Sandy beach and dune habitats are increasingly squeezed between the impacts of human land development and the manifestations of climate change (Schlacher et al. 2007, Nordstrom 2000). Hutto et al. (2015) determined that the most vulnerable habitats in their North-central California Coast and Ocean study region were beaches and coastal dunes, estuaries, and rocky intertidal because they exist at the land-sea interface.

Sea level rise and other projected effects of climate change, including increased storm intensity/frequency and increased wave action, are expected to exacerbate the trend of shoreline erosion and retreat, and further degrade habitat (Nordstrom 2000, Slott et al. 2006, PWA 2009). Marin County will be especially impacted by dune erosion (PWA 2009) as sea level rise is expected to flood existing habitat and force the landward retreat of these communities. Where coastal dunes are backed by development, upland habitat for the colonization and persistence of dune vegetation may become increasingly limited, further fragmenting this ecosystem (Feagin et al. 2005). Sea level rise can also disrupt the successional dynamics and coastal processes that lead to the formation of mature coastal dune vegetation communities and biodiversity (Feagin et al. 2005). Changing climatic variables such as precipitation and salt spray may also affect the composition of these communities by modifying soil salinity, with subsequent effects on plant physiology (Williams et al. 1999, Greaver and Sternberg 2007). An increase in severe storms and coastal flooding could be detrimental to reproductive success of insect and beach-nesting birds such as the snowy plover.

Warming Temperatures and Shifting Seasons Warmer air and soil temperatures (especially in winter), changes in precipitation, and an earlier spring transition of weather and ocean patterns have been shown to result in changes in phenological processes in plants and insects, potentially causing the decoupling of conditions important for the survival of species, such as reproductive events mistimed with peak food availability. Forister and Shapiro (2003) show that the average first spring flight of 23 butterfly species in the Central Valley of California has advanced to an earlier date over the past 31 years.

In addition to phenological changes, other potential impacts from a changing climate include increased aridity or changes in precipitation patterns that may favor different plant species, annual or biennial versus perennial reproductive cycles, increased hybridization, changes in arthropod herbivory, and vernalization (the process of cold winter soil temperatures signaling some species' seeds to germinate). Butterfly species in California and elsewhere have been shown to already be shifting in geographic distribution in response to changing climate (Forister et al. 2010).

Marine Island Ecosystems Nested Targets: Farallon camel cricket (Farallonophilus cavernicolus), CA arboreal salamander (Aneides lugubris farallonensis), maritime goldfields, marine mammals, and breeding seabirds

Summary

Anticipated changes in ocean, climate, and coastal weather patterns are expected to significantly impact the physical habitat on offshore islands by reducing the amount of habitat available to seabird and marine mammals for breeding and resting. Other important potential impacts include disruptions of the marine-based food web, erosion, and changes in vegetation communities on the islands.

Sea Level Rise Future sea level rise off northern and central California has the potential to significantly alter island habitats and cause redistribution of wildlife populations. Models demonstrate that a rise of 0.5 m would result in permanent flooding of 23,000 m2 of habitat at the South Farallon Islands (Largier et al. 2010). This area represents approximately 5% of the island’s surface area and would include intertidal areas

where pinnipeds haul out, as well as pocket beaches and gulches around the island. As a result, these areas would become inaccessible, forcing the animals to move higher up onto the marine terrace or to abandon the colony. This redistribution of pinnipeds would, in turn, impact seabird habitat by reducing the available nesting areas and causing the destruction of nest sites, particularly for burrow nesting species such as the Cassin’s auklet (Ptychoramphus aleuticus). Furthermore, during extreme high tides and storm events, waves would be expected to extend higher still, leading to increased erosion, flooding, and loss of habitat.

Examples of these changes can be seen during El Niño events when alongshore winds decrease and warm water floods into the area from the tropical Pacific, leading to higher sea level off the coast of California. During the El Niño events of 1983 and 1992, higher water and increased storm activity resulted in significant erosion of elephant seal (Mirounga angustirostris) breeding areas and the destruction of important beach access routes at the Farallon Islands (Sydeman and Allen 1999). This made it more difficult for the elephant seals to access their primary breeding areas and ultimately led to local population declines and reduced breeding success (Sydeman and Allen 1999). The distribution of pinnipeds was also significantly altered during El Niño events, resulting in greater numbers of animals hauled out high on the marine terrace, habitat normally occupied by breeding seabirds (Largier et al. 2010). Similar consequences would be expected with rising oceans, particularly if coupled with more extreme weather events, which are also projected to occur as a result of climate change.

Changes in Precipitation Patterns Intensified winter precipitation and more significant rainfall later in the season may alter physical habitat in many ways. Increased erosion of the hillsides can alter vegetation structure, increase the frequency of rockslides, and degrade nesting habitat — particularly for species that rely on rock crevices, such as auklets and storm petrels. Flooding of low lying areas on the marine terrace will also decrease suitable habitat for burrow-nesting species and carry away the thin layer of soil in which they dig their burrows (Largier et al. 2010).

Rising Air Temperatures Average annual air temperature at the Farallon Islands has exhibited an increasing trend over a 36-year period, from 1971- 2007 (Largier et al. 2010). Scientists expect this trend to continue, leading to overall changes in the climate of the islands. While warmer temperatures would not necessarily alter the physical structure of the islands, it may affect habitat by altering the vegetation structure on the island and facilitating the proliferation of more heat tolerant non-native species, such as grasses. Increasing air temperatures will also have important implications for island wildlife. Many of these species are adapted to cold and windy conditions and quickly become stressed when conditions change. During unusually warm weather, seabirds may abandon their nests, neglect dependent offspring, and die of heat stress (Warzybok and Bradley 2011). Marine mammals are expected to spend less time hauled out and may abandon young in the rookeries if temperatures become too warm.

Ocean Condition Changes Projected changes in the marine environment associated with climate change are expected to have substantial impacts on breeding seabird populations. These changes include rising sea surface temperatures, ocean acidification, and changes in timing and strength of upwelling and ocean circulation patterns. Please see “Climate Changed-Induced Stress on Breeding Seabirds” for more information.

Riverine Sand Dunes

Nested targets: Lange's metalmark butterfly (Apodemia mormo langei), Contra Costa wallflower (Erysimum capitatum var. capitatum), Antioch Dunes evening primrose (Oenothera deltoids var. howellii).

Summary While loss and degradation of remaining habitat is the most pressing concern for dune plant and insect species (Xerces Society website), climate change related impacts are also important for conservation planning. Key climate change-related stressors for riverine sand dunes and the associated species of the Antioch Dunes National Wildlife Area are likely to include changes in average conditions (warming temperatures and rainfall), severe weather extremes, and phenology shifts. Non climate-related threats that may be exacerbated by climate change include increased rate of spread of invasive species and potential for fire.

Increased Temperatures, Changing Precipitation Long-term changes in average temperature and rainfall conditions may affect habitat suitability for plants and insects at Antioch Dunes NWR. Increased aridity or changes in precipitation patterns may favor different plant species, annual or biennial versus perennial reproductive cycles, increased hybridization, changes in arthropod herbivory, and vernalization (the process of cold winter soil temperatures signaling some species' seeds to germinate). Butterfly species in California have been shown to already be shifting in geographic distribution in response to changing climate (Forister et al. 2010).

Heat and Other Weather Extremes Small populations of endemic species restricted to a very small geographic area, such as the three endangered species found at Antioch Dunes, are especially vulnerable to weather extremes. More frequent and prolonged drought and periods of extreme heat could cause direct mortality, or prevent or delay, the germination of plants. They could also impact insect life cycles. Anticipated increases in coastal storm frequency and severity is expected to threaten the persistence of coastal bluff habitat and associated coastal plant species by increasing inundation, flooding, and erosion (Largier et al. 2010).

Warming Temperatures and Shifting Seasons Warmer air and soil temperatures (especially in winter), changes in precipitation, and an earlier spring transition of weather and ocean patterns have been shown to result in changes in phenological processes in plants and insects, potentially causing the temporal decoupling of conditions important for survival of species, such as reproductive events mis-timed with peak food availability. For example, Forister and Shapiro (2003) show that the average first spring flight of 23 butterfly species in the Central Valley of California has advanced to an earlier date over the past 31 years.

Non-climate Stressors Changing average climate conditions and weather extremes may lead to increases in invasive plants, insects, and animals that could out-compete or predate on the native species or the plants they depend upon for their life cycles. Extreme heat and drought could lead to an increased potential for fire, shifting the balance in favor of some species and against others depending on adaptation and timing.

Pajaro River Waterhsed Nested targets: California tiger salamander (Ambystoma californiense), Santa Cruz long-toed salamander (ambystoma macrodactylum croceum), ponds, seasonal wetlands, oak woodlands, grasslands

Summary The key climate-related threat to salamanders is the degradation and loss of vernal pool or pond habitat (“pond” and “vernal pool” are terms used interchangeably), which will likely result due to the combined effects of increased drought, reduction in precipitation, and increased air temperature. Increased exposure to ultraviolet radiation may present an additional threat.

More Arid Conditions, Reduced Hydroperiod Precipitation projections are highly variable, but drought frequency and intensity is expected to increase as a result of increased air temperatures, regardless of precipitation amount. California is already experiencing increased drought conditions; drought years in California have occurred twice as often in the last 20 years compared to the preceding century (Diffenbaugh et al. 2015).

To maintain salamander populations, it is critical that seasonal ponds are available for reproduction and throughout development from egg to adult. Even the temporary drying of ponds could cause direct mortality. California tiger salamanders (CTS) breed in 1-7 foot deep ponds and require a least two months to develop from egg to adult (USFWS 2009). CTS’ developmental period is prolonged in colder weather, and under such conditions, can take in excess of four months (USFWS 2009). Studies suggest the majority of adult CTS immigration to breed ponds occurs when ponds fill; in California, this generally occurs from December to February (Trenham et al. 2000).

Drought and increased air temperature can completely prevent ponding and/or reduce the ponding hydroperiod (Bauder 2005). Loss of pools or reduction of the hydroperiod at critical times can reduce salamander breeding opportunities (Barry and Shaffer 1994). Early pond drying caused by drought conditions can also lead to death of larval stage salamanders (U.S. Fish and Wildlife Service 2016). However, relatively long adult lifespans help salamander populations weather short-term drought (Barry and Shaffer 1994), but longer drought durations would likely negatively affect CTS and other salamander species by limiting breeding opportunities and reducing survival (U.S. Fish and Wildlife Service 2016). Paired with naturally low recruitment (Trenham et al. 2000), drought could threaten CTS persistence (U.S. Fish and Wildlife Service 2016).

Increased Exposure to UV Radiation In addition to reduction in hydroperiod, drought and decreased rainfall can cause a reduction in pond depth, which increases egg and larva exposure to ultraviolet (UV) radiation. Increased UV exposure has been shown in many salamander species to lead to egg mortality or embryo deformities (Blaustein et al. 2011). UV exposure has also been shown in multiple salamander species to increase time spent under refugia and in deeper waters (Garcia, Stacy, Sih, and Garcia 2014).

Tidal Flats and Open Water

Nested targets: Delta smelt (Hypomesus transpacificus), green sturgeon (Acipenser medirostris), longfin smelt (Spirinchus thaleichthys), salmonids (Salmonidae), tidewater goby, shorebirds, waterfowl, other waterbirds, invertebrates.

Summary Key climate change related stressors for tidal flats and open water include declining estuarine food web productivity, algae blooms, increased salinity, disease, and loss of tidal flat habitat from sea-level rise. These changes would likely result in impacts to native fish populations and waterbird species’ distributions. Non-climate related stressors include invasive species introductions and water diversions.

Sea-level Rise Primary impacts of sea level rise on coastal habitats and communities are the increased likelihood and depth of coastal flooding. Tidal flat habitat may be converted to open water as a result of increased inundation depth and time periods, depending upon the rate of sediment supply and the ability of the gradient of tidal wetland habitat types to migrate inland with the rising sea-level (see the Tidal Wetland climate summary for more on this topic).

Increasing Salinity Lower ecosystem productivity from salinity increases will affect both primary and detrital-based food webs. Such changes will cascade via the food webs into invertebrate, bird, and pelagic systems. Biodiversity of the tidal wetland system in the San Francisco Bay-Delta region is expected to decline, with subsequent effects on ecosystem functioning and services. Altered plant production, physiological tolerances, and shifts in rates of mortality will modify wetland plant communities in ways not yet predictable (Parker et al. 2011).

Bay Water Quality Food supply for fish and other species is likely to become less reliable due to rising water temperatures, increased frequency of El Niño events, and the effects of ocean acidification. Declines in zooplankton, an important prey item for many fish, have been associated with rising sea surface temperatures (Hill 1995, Roemmich and McGowan 1995), and it is believed these declines affect the nearshore and open water ecosystem food webs (Abraham and Sydeman 2004, Lee et al. 2007, Jahncke et al. 2008, Lehman 2004). Climate is thought to have contributed to the downward shift in estuarine production (biomass) in northern San Francisco Bay estuary from 1975 to 1993 via direct and indirect mechanisms. It was also thought to have contributed to physical changes in water transparency, water temperature, wind velocity, and rainfall accompanied by a decrease in diatom, total zooplankton, and carbon at the base of the food web throughout the estuary (Lehman 2004).

Ocean acidification is likely to affect many aspects of biochemistry, development, behavior, and reproduction for marine and nearshore organisms, and cause effects at all trophic levels, although the implications to food webs are poorly understood and difficult to project. Studies suggest that there are a variety of potential impacts of ocean acidification and its combination with warming temperatures on a wide variety of organisms (Rosa and Seibel 2008, Munday et al. 2009, Petkewich 2009).

Bay conditions are likely to change as a result of more extremes in precipitation and drought. These impacts are already suspected to be happening due to climate change, affecting aquatic and marsh habitats and the species that rely on them. For example, there have been observations of impacts to

water quality within the San Francisco Bay associated with the freshwater runoff from the extremely wet winter of 2016-17, which followed a prolonged drought. Low salinity and increased pollution resulting from this runoff is suspected of causing an outbreak of a protozoan pathogen thought to be the cause of a mass die-off of sharks and rays (Simons 2017). However, high ambient temperatures and increased water surface temperature of bay water are thought to support algal blooms in San Francisco Bay (Cloern et al. 2005). These effects could compound other stressors in ways not yet well understood.

Impacts on Fish Adverse effects from climate change on the native fishes of the San Francisco Bay Area are thought to be secondary to the impacts of estuarine alteration, agriculture, and upstream dam operations. However, the relative effect of climate change on these species will likely grow in an increasingly warmer and drier California, conditions that will generally favor alien fishes over native species (Moyle et al. 2013, Quiñones and Moyle 2014). Particularly vulnerable are fishes that rely on cold water, including the region’s salmonids (Moyle et al. 2012). Delta smelt is sensitive to changes in estuarine conditions, where it is closely associated with the freshwater-saltwater mixing zone, except when it spawns in fresh water in the spring (Moyle et al. 1992). Water diversions during periods of drought have contributed to delta smelt declines in the past (Moyle et al. 1992, Bennett 2005), and these conditions are expected to become more acute under climate change. Delta smelt were assessed by Moyle et al. (2012) to be the most vulnerable (“critically vulnerable”) to climate change impacts of the region’s native fishes; followed by hardhead, longfin smelt, and coho and chinook salmon.

Please also see the climate impact summary for breeding seabirds for more information about climate- related changes to outer-bay ocean habitats, and the waterbirds summary for that nested target.

Tidal Marshes Nested targets: transition zone, low marsh, high marsh, tidal marsh plants, fish/steelhead, Ridgway's rail (Rallus obsoletus), salt marsh harvest mouse (Reithrodontomys raviventris), common yellowthroat (Geothylpis trichas), song sparrow (Melospiza melodia)

Summary Marshes represent the interface between aquatic and terrestrial systems. Persistence of a marsh is a balancing act between processes that increase (accretion, organic matter inputs, tectonic uplift) and decrease (erosion, decomposition, compaction, and subsidence) marsh elevation relative to sea level. If processes that increase marsh elevation outpace those that decrease it, marshes transition into higher elevation marsh or uplands. If processes that decrease marsh elevation outpace marsh inputs, vegetation is no longer able to survive and marshes transition to mudflat or open water. The climate change vulnerability of tidal marshes results from how climate drivers directly or indirectly affect these processes.

Sea Level Rise If sea level rise outpaces sediment accretion and tectonic uplift, marshes will be inundated for longer periods of time. Increased inundation ultimately decreases plant production, and increases compaction and decomposition, or can lead to anoxic soils. Eventually, high rates of sea level rise will lead to conversion of marsh to mudflats and the possible expansion of marsh into upland areas. This process will likely result in changes in vegetation and habitat availability for marsh dependent species such as

Ridgway's rail, salt marsh harvest mouse, common yellowthroat, and song sparrow (Takekawa et al. 2013). The response of tidal marshes to sea level rise will vary based on local conditions; for example, research suggests that suspended sediment concentration in the North Bay is lower than South Bay (Takekawa et al. 2013).

Extreme Events: Storms Storms accompanied by large amounts of precipitation and increased wave action could affect tidal marshes in the following ways:

• Changes in inundation regimes can alter the biological zonation of plant communities due to inundation and salinity tolerance limitations (Foin et al. 1997, Mendelssohn and McKee 1988, Day et al. 2008, Zedler 2010). • Vegetation may be buried or covered with sediment or debris, which can reduce primary productivity or cause dieback (Callaway and Zedler 2004). • Storm flushing and sediment influx can increase delivery of nutrients and reduce soil salinity, which are necessary to promote vegetative growth (Zedler et al. 1986, Zedler 2010). • Unusually low pickleweed cover has been observed after periods of extended inundation from storms (Zedler et al. 1986). • Storms could lead to episodic flooding that would temporarily decrease the amount of available habitat and displace wildlife, exposing them to competition and predation (Zedler et al. 1986). • Storms during the breeding season have been observed to overtop nests and cause egg failure, reducing fecundity of marsh birds, particularly rails (John Y Takekawa et al. 2006; Massey, Zembal, and Jorgensen 1984). • Storms may provide local suspended sediment to build marsh elevation relative to sea-level rise (Thorne et al. 2013).

Vernal Pool Grasslands Nested targets: Contra Costa goldfields (Lasthenia conjugens), vernal pool plants, vernal pool tadpole shrimp, California tiger salamander (CTS; Ambystoma California).

Summary Fall and winter rains drive the “wet” period of the vernal pool hydrologic cycle. Initial rains stimulate plant germination and invertebrate hatching (Zedler 1987), and continued rains result in ponding. As precipitation declines in spring, vernal pools experience slow drying of surface water and substrate, with significant desiccation common by late summer (Zedler 2003). The result of this process is a gradient from the center of the pool to the surrounding upland edge, with flooding frequency, depth, duration, and timing varying considerably. This gradient drives differences in vegetation assemblages, vulnerability to invasion, and crustacean predator presence.

Precipitation Vernal pools are sensitive to annual changes in amount and timing of precipitation events. Vernal pool species are typically adapted to seasonal drought (Zedler 2003), but severe drought periods can completely prevent vernal pool ponding, and many pools experience minimal ponding duration in years with below-average precipitation (Bauder 2005). Reduced precipitation results in a shorter hydroperiod and drier conditions. These changes would likely alter habitat suitability for a variety of vernal pool

32 obligate species and make vernal pools more vulnerable to exotic invasion (Marty 2005). Common invasive grasses are likely to benefit from drying, because they are intolerant of extended inundation and their abundance declines with increasing vernal pool water depth (Gerhardt and Collinge 2003). However, some invasive species also experience increased growth during high precipitation years (e.g., El Niño; Bauder 2005).

Even small hydroperiod reductions can affect community diversity and habitat suitability for plant and animal species, particularly those with longer aquatic life stages (e.g., CTS, western spadefoot toads; Marty 2005). Vernal pool obligates with life histories that are tightly coupled to hydrological conditions, such as branchiopods, will be most vulnerable to reduced hydroperiod.

In conjunction with total annual rainfall, shifts in seasonal precipitation patterns will influence ponding frequency and duration. For example, in several southern California study sites, high rainfall delivered in discrete periods yielded longer ponding time than the same rainfall volume distributed equally throughout the season in years with average precipitation. However, at the same study sites during years with low annual precipitation, consistent rain favored longer ponding times than discrete, intense rainfall events (Bauder 2005). Larger, deeper pools may show less of a response to precipitation shifts than shallow pools that currently provide marginal habitat (Pyke 2005).

Extreme Events: Flooding Some projections suggest an increase in flooding as a result of more rapid runoff from snowmelt and spring rains in the Sierra Nevada during the time period that vernal pools experience their seasonal winter flooding (December-March). Greater inundation depth and duration typically reduces invasive species establishment success, and inundation has been found to reduce the survival, growth, and reproduction of many invasive species (Gerhardt and Collinge 2007).

Vernal pools are adapted to seasonal flooding. Prolonged flooding (usually a result of human modifications) can cause seed rot and trigger novel germination patterns, potentially facilitating vegetation shifts, including shifts to more permanent wetland-affiliated vegetation. Prolonged inundation can also increase habitat suitability for key crustacean predators, including fish and bullfrogs (U.S. Fish and Wildlife Service 2005).

Water Temperature Water temperature affects vernal pool crustacean hatching (Eriksen and Belk 1999) and development rates and influences immature and adult crustacean mortality (Helm 1998).

Waterbirds Nested targets: Eared grebe (Podiceps nigricollis), managed pond island nesting birds, shorebirds, waterfowl

Summary Key climate change related stressors for waterbirds are loss of habitat, nesting sites, and food sources due to sea level rise and changing ocean conditions. Bay water quality may also be affected by changing climate and hydrologic conditions, causing other potential as-yet unknown impacts.

Sea Level Rise and Coastal Erosion Sea level rise is projected to cause inundation and significant loss of tidal marsh and mudflats; key habitat used by shorebirds and waterfowl. The physical structure of estuarine and beach habitat is likely to undergo significant changes from sea level rise and other climate change-related effects. Despite the certainty of rising sea levels, much uncertainty surrounds the long-term effects of sea level rise on these physical habitats. Other factors, including organic and inorganic sediment deposition, storms, erosion, and changes in freshwater runoff will also influence the rates at which tidal elevation is altered and the extent to which these coastal habitats are lost (Hutto et al. 2015, Largier et al. 2010).

Sea level rise combined with increased storm intensity and wave action are expected to exacerbate the trend of shoreline erosion and degrade sandy beach habitat (Nordstrom 2000, Slott et al. 2006, PWA 2009). Shorebird use of beaches can be high and is positively correlated with the availability of invertebrate prey, the amount and type of macroalgae wrack, beach slope, and beach width (Dugan 1999, Dugan et al. 2003, Dugan et al. 2004, Neuman et al. 2008, Revell et al. 2011). It is difficult to predict the precise reduction in shorebird numbers likely to result from any estimated loss of habitat, largely because the degree to which any site is saturated for any species is not known, making prediction ns speculative. However, there is little doubt that major effects will likely occur to at least some shorebird species at some sites, especially in South SF Bay. (Galbraith et al. 2002). Birds of all types, including shorebirds, seabirds, and gulls, have been shown to respond negatively to beach width and zone losses associated with coastal armoring (Dugan et al. 2008). Threatened birds, such as the western snowy plover (Charadrius nivosus nivosus) and California least tern (Sternula antillarum browni), nest in open beach and dune habitats on GFNMS shorelines (Lehman 1994, Page et al. 1995), making use of the dry sand zone; a habitat where erosive impacts from climate change will be strongly expressed.

Changing Ocean and Bay Conditions Ocean acidification is likely to cause changes in mudflat biotic community structure and productivity, impacting food sources for birds (Largier et al. 2010). For example, increased acidity has been found to cause decreased fertilization and embryo development rates in Pismo clam (Tivela stultorum) (Alvarado- Alvarez et al. 1996). The North American wintering Aechmophorus grebe and western grebe populations have undergone changes in abundance and distribution between 1980 and 2010, possibly linked to changes in prey densities (Wilson et al. 2013). Changes associated with increased ocean temperatures, wind, mixing, and upwelling are expected to have profound effects on all levels of the food web in ways not yet well understood (Largier 2015).

Bay conditions may change as a result of more extremes in precipitation and drought already suspected to be happening due to climate change, affecting aquatic and marsh habitats and the species that rely on them. There have recently been observations of impacts to water quality within the Bay associated with the freshwater runoff from the extremely wet winter of 2016-17. Low salinity and increased pollution resulting from this runoff is suspected of causing an outbreak of a protozoan pathogen thought to be the cause of a mass die-off of sharks and rays (Simons 2017). These effects could compound other stressors in ways not yet well understood.

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Appendix I: Projections for the North Complex

Temperature

Figure 14. Summer monthly average temperatures are projected to change approximately 7.6°F from a 1980 baseline; winter average temperatures change approximately 5.6°F using the GFDL A2. The "Hot- Dry" MIROC-ESM RCP 8.5 projects a more extreme rate of increase—see graph below.

Figure 15. Maximum monthly temperature annual averages from the three models for the San Pablo Bay Watershed. Note that the lowest average monthly maximum temperatures consistently exceed even the highest from the historic data after about the middle of the century.

Precipitation

Figure 16. "Warm-Wet" CNRM RCP 8.5 shows an increasing trend for annual average precipitation, with the potential for high-end extremes above historic levels. GFDL A2 and the "Hot-Dry" MIROC ESM RCP 8.5 indicate a decreasing trend for annual average precipitation, with the potential for low-end extremes below historic levels.

Figure 17. 30-year averages for projected compared to historical precipitation patterns over the water- year. All models still show the Mediterranean pattern of precipitation with the potential for shifts in seasonality (possible earlier cessation of rainy season.

Aridity

Figure 18. All models indicate a steady increase in annual average climatic water deficit, with annual high- end extremes as much as 30% higher than historic levels in the second half of the century.

Seasonal water balance changes Figure 18 shows a shift in hydrologic conditions: a decrease in actual evapotranspiration, an indicator of plant growth (green), and an increase of length and intensity of the dry season with respect to both soil moisture (yellow) and climatic water deficit (red).

Figure 19. Comparison of 30-year averages for the historical period of 1951-1980 and projected future period of 2070-2099 using the GFDL A2 model.

Sea level rise and coastal flooding Most models project a 25 cm increase in average sea level by 2050 and for the rate of increase to accelerate over the coming century (OCOF, NRC, 2012). SF Bay Complex Refuges in low-lying areas will be affected by rising sea level combined with increased occurrences of storms bringing wave surge and freshwater run-off. El Niño years will further heighten risks of inundation due to temporary extremes in sea levels (see the graphs and information presented in the California and Region-wide Projections summary).

Below are maps made using Our Coast Our Future, comparing present-day flood risk on the north San Pablo Bay coastline with no storm effect (top) to a 25 cm increase in sea level and no storm effect (middle), and to a 25 cm increase in sea level with a 100-year storm (bottom). Please use the OCOF tool for access to data and reports for specific (>2,000 acre) areas.

Figure 20. Present-day sea level and no storm effect.

Figure 21. A 25 cm increase in sea level and no storm effect.

Figure 22. 5 cm increase in sea level with a 100-year storm.

Tidal marsh habitat changes Persistence of a marsh is a balancing act between processes which increase marsh elevation (sedimentation, organic matter inputs, tectonic uplift) and processes that decrease marsh elevation (erosion, compaction, and subsidence) relative to sea level. The magnitude of these effects are typically measured in millimeters a year. If processes that increase marsh elevation outpace those that decrease it, marshes transition into uplands. If processes that decrease marsh elevation outpace marsh inputs, then marshes transition into mudflat or become subtidal. Measuring any of these processes precisely is difficult, and anticipating how they will respond to climate and non-climate stressors in the future is impossible. However, to develop models and projections of future tidal marsh, researchers must make assumptions. There are multiple tidal marsh projections for SF Bay and they all make slightly different assumptions about the magnitude of future marsh inputs and exports, or they use different input data. Map results from two tidal marsh modeling projects are featured below (figures 22-26).

PRBO Future Tidal Marsh Mapping tool: These maps can be easily generated for a variety of different scenarios using this web mapping app (link). The sedimentation and sea level scenario seem to have a much larger impact on results than the organic materials scenario:

Figure 23. Year: 2010

Figure 24. Year: 2050; Sedimentation (accretion): high (1.65 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high

Figure 25. Year: 2050; Sedimentation (accretion): low (0.5 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high

Figure 26. Year: 2110; Sedimentation: high (1.65 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high

Figure 27. Year: 2110; Sedimentation: low (0.5 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high WARMER Modeling Results: These results are different than the ones above because they were developed using a different SLR projection (1.23 meters by 2100; Cayan 2009), elevation data collected in the field via RTK, and sediment and organic matter rates with estimates based on soil cores from the North Bay. To access this report in its entirety, click here.

Figure 28. WARMER results for west San Pablo. WARMER accounts for changes in relative sea-level, subsidence inorganic sediment accumulation, above and belowground organic matter productivity, compaction, and decay. Non-linear sea-level rise projections for California were used (Cayan and others, 2009). [MSL, mean sea level; m, meters]

Figure 29. West San Pablo WARMER results in terms of plant communities relative to mean sea level (MSL), in meters (m): mudflat, low, mid, or high marsh, or upland transition.

Figure 30. WARMER results for east San Pablo. WARMER accounts for changes in relative sea-level, subsidence, inorganic sediment accumulation, above and below ground organic matter productivity, compaction, and decay. Non-linear sea-level rise projections for California were used (Cayan and others, 2009). [MSL, mean sea level; m, meters]

Figure 31. East San Pablo WARMER results in terms of plant communities relative to mean sea level (MSL), in meters (m): mudflat, low, mid, or high marsh, or upland transition.

Refuge-specific Projection Data Projected changes in climate and hydrology parameters, using two models with high greenhouse gas concentrations for Planning Watersheds in or near the Refuges in the North Complex:

San Pablo Bay NWR

Figure 32. Map of San Pablo Bay NWR.

Table 1. Watershed data for San Pablo Bay NWR.

San Pablo Bay Data below is for this watershed: Gallinas Creek (HUC 2206200003) See also data for the larger watershed: San Pablo Bay MIROC-ESM RCP 8.5 (Hot/Dry) CNRM RCP 8.5 (Warm/Wet) Average Average Annual Average Annual Average Annual Average Annual Annual Data Data for 2025 - Data for 2090 - Data for 2025 - Data for 2090 - for WY 1999 - 2034 2099 2034 2099 2008 Climate or Hydrology Projected Delta Projected Delta Projected Delta Metric (Historic) Projected Delta Daily Max Temperature,°C Annual Average 20.6 22.1 1.5 26.6 6 21.8 1.2 24.6 4 Daily Min Temperature,°C Annual Average 8.9 10.1 1.2 14 5.1 9.6 0.7 12.6 3.7 Precipitation, mm Annual Total 739 711 -28 564 -175 892 153 1083 344 Runoff, mm Annual Total 114 84 -30 50 -64 203 89 331 217

Recharge, mm Annual Total 196 170 -26 112 -84 248 52 300 104 Potential EvapoTranspiration, mm Annual Total 1191 1227 36 1286 95 1224 33 1282 91 Actual EvapoTranspiration, mm Annual Total 428 456 28 403 -25 445 17 463 35 Climatic Water Deficit, mm Annual Total 761 770 9 916 155 772 11 820 59

Marin Islands NWR

Figure 33. Map of Marin Island NWR

Table 2. Watershed data for Marin Island NWR

Marin Islands Data below is for the nearest mainland watershed: San Rafael Creek (HUC 2203200102) See also data for the larger watershed: San Pablo Bay MIROC-ESM RCP 8.5 (Hot/Dry) CNRM RCP 8.5 (Warm/Wet)

Average Average Annual Average Annual Average Annual Average Annual Annual Data Data for 2025 - Data for 2090 - Data for 2025 - Data for 2090 - for WY 1999 - 2034 2099 2034 2099 2008 Climate or Hydrology Projected Delta Projected Delta Projected Delta Metric (Historic) Projected Delta Daily Max Temperature,°C Annual Average 20.4 22.1 1.7 26.6 6.2 21.7 1.3 24.5 4.1 Daily Min Temperature,°C Annual Average 9.2 10.5 1.3 14.4 5.2 10 0.8 13 3.8 Precipitation, mm Annual Total 866 845 -21 670 -196 1061 195 1286 420 Potential EvapoTranspiration, mm Annual Total 1190 1233 43 1289 99 1225 35 1285 95 Actual EvapoTranspiration, mm Annual Total 400 433 33 392 -8 424 24 443 43 Climatic Water Deficit, mm Annual Total 790 799 9 933 143 797 7 843 53

Antioch Dunes NWR

Figure 34. Map of Antioch Dunes NWR.

Table 3. Watershed data for Antioch Dunes NWR.

Antioch Dunes Data below is for this watershed: Unnamed basin within Dowest Slough (HUC 2207340200) See also data for the larger watershed: Suisun Bay Watershed MIROC-ESM RCP 8.5 (Hot/Dry) CNRM RCP 8.5 (Warm/Wet) Average Average Annual Average Annual Average Annual Average Annual Annual Data Data for 2025 - Data for 2090 - Data for 2025 - Data for 2090 - Climate or Hydrology for WY 1999 - 2034 2099 2034 2099 Metric 2008 (Historic) Projected Delta Projected Delta Projected Delta Projected Delta Daily Max Temperature,°C Annual Average 22.9 24.2 1.3 29.1 6.2 23.9 1 26.9 4 Daily Min Temperature,°C Annual Average 9.4 10.5 1.1 14.5 5.1 10 0.6 13.2 3.8 Precipitation, mm Annual Total 397 382 -15 294 -103 480 83 574 177 Runoff, mm Annual Total 0 0 0 0 0 0 0 1 1 Recharge, mm Annual Total 3 1 -2 0 -3 42 39 83 80 Potential EvapoTranspiration, mm Annual Total 1263 1289 26 1353 90 1285 22 1349 86 Actual EvapoTranspiration, mm Annual Total 390 378 -12 297 -93 443 53 499 109 Climatic Water Deficit, mm Annual Total 869 911 42 1091 222 837 -32 851 -18

Farallon Islands NWR A detailed climate impact assessment has been completed for the Farallon Islands NWR: Please see the Climate Change Impacts: Gulf of the Farallones and Cordell Bank National Marine Sanctuaries.

More Data and Information Online See these links to explore more for the North Complex: • USGS Explore Your Watershed: San Pablo Bay Watershed • Watershed Analyst dynamic graphs: Gallinas Creek Watershed (and others) • BCM graphs: San Francisco Bay Watershed (and others)

Figure 35. San Pablo Bay watershed map

Appendix II: Projections for the Central Complex

Temperature Degrees of change for summer and winter months: summer monthly average temperatures are projected to change almost 8°F from a 1980 baseline; winter average temperatures change approximately 6°F using the GFDL A2.

Figure 36. The "Hot-Dry" MIROC-ESM RCP 8.5 projects a more extreme rate of increase.

Figure 37. Maximum monthly temperature annual averages from the three models. Note that the lowest average monthly maximum temperatures consistently exceed even the highest from the historic data after about the middle of the century.

Precipitation

Figure 38. "Warm-Wet" CNRM RCP 8.5 shows an increasing trend for annual average precipitation, with the potential for high-end extremes above historic levels. GFDL A2 and the "Hot-Dry" MIROC ESM RCP 8.5 indicate a decreasing trend for annual average precipitation, with the potential for low-end extremes below historic levels. 64

Figure 39. 30-year averages for projected compared to historical precipitation patterns over the water- year. All models still show the Mediterranean pattern of precipitation, with the potential for shifts in seasonality (possible earlier cessation of rainy season in the spring).

Aridity

Figure 40. All models indicate a steady drying trend indicated by an increase in annual average climatic water deficit, with annual high-end extremes as much as 20% higher than historic levels in the second half of the century.

Seasonal water balance changes Figure 40 shows a shift in hydrologic conditions: a decrease in actual evapotranspiration, an indicator of plant growth (green), and an increase of length and intensity of the dry season with respect to both soil moisture (yellow) and climatic water deficit (red).

Figure 41. Comparison of 30-year averages for the historical period of 1951-1980 and projected future period of 2070-2099 using the GFDL A2 model.

Sea level rise and coastal flooding A 25 cm increase in average sea level is projected by most models to occur by 2050, and the rate of increase is expected to accelerate over the coming century (OCOF, NRC, 2012). SF Bay Complex Refuges in low-lying areas will be affected by rising sea level combined with increased occurrences of storms bringing wave surge and freshwater run-off. El Niño years will further heighten risks of inundation due to temporary extremes in sea levels (see the graphs and information presented in the California and Region-wide Projections summary).

Below are maps made using Our Coast Our Future, comparing present-day flood risk on the south San Francisco Bay coastline with no storm effect (top) to a 25 cm increase in sea level and no storm effect (middle), and to a 25 cm increase in sea level with a 100-year storm (bottom). Please use the OCOF tool for access to data and reports for specific (>2,000 acre) areas.

Figure 42. Present-day sea level and no storm effect.

Figure 43. 25 cm increase in sea level and no storm effect.

Figure 44. 25 cm increase in sea level and 100-year storm effect.

Tidal marsh habitat changes Persistence of a marsh is a balancing act between processes which increase marsh elevation (sedimentation, organic matter inputs, tectonic uplift) and processes that decrease marsh elevation (erosion, compaction, and subsidence) relative to sea level. The magnitude of these effects are typically measured in millimeters a year. If processes that increase marsh elevation outpace those that decrease it, marshes transition into uplands. If processes that decrease marsh elevation outpace marsh inputs, then marshes transition into mudflat or become subtidal. Measuring any of these processes precisely is difficult, and anticipating how they will respond to climate and non-climate stressors in the future is impossible. However, to develop models and projections of future tidal marsh, researchers must make assumptions. There are multiple tidal marsh projections for SF Bay and they all make slightly different assumptions about the magnitude of future marsh inputs and exports, or they use different input data. Map results from the two tidal marsh modeling projects are featured below.

PRBO Future Tidal Marsh Mapping tool:

These maps can be easily generated for a variety of different scenarios using this web mapping app (link). The sedimentation and sea level scenario seem to have a much larger impact on results then the organic materials scenario:

Figure 45. Central Complex Map, year: 2010

Figure 46. Year: 2050; Sedimentation (accretion): high (1.65 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high

Figure 47. Year: 2050; Sedimentation (accretion): low (0.5 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high 71

Figure 48. Year: 2110; Sedimentation: high (1.65 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high

Figure 49. Year: 2110; Sedimentation: low (0.5 m/century); Sea Level Rise Projection: 165cm by 2100; Organic Materials: high 72

WARMER Modeling Results: These results are different than the ones above because they are developed using a different SLR projection (1.23 meters by 2100; Cayan 2009), elevation data collected in the field via RTK, and sediment and organic matter rates with estimates based on soil cores from the North Bay. To access this report in its entirety, click here. WARMER modeling efforts have not been as extensive because it is more labor intensive, but below are modeling results for Laumeister marsh to provide a comparison how of results vary across models.

Figure 50. WARMER results for Laumeister. WARMER accounts for changes in relative sea-level, subsidence, inorganic sediment accumulation, above and belowground organic matter productivity, compaction, and decay. Non-linear sea-level rise projections for California were used (Cayan and others, 2009). [MSL, mean sea level; m, meters]

Figure 51. Laumeister WARMER resullts in terms of plant communities relative to mean sea level (MSL), in meters (m), mudflat, low, mid, or high marsh, or upland transition.

Alameda Point NWR

Figure 52. “Undefined basin within Oakland (HUC 2204200400),” used to retrieve data for Alameda Point.

Table 4. Watershed data for Alameda Point, unnamed basin within Oakland.

Alameda Point Data below is for this watershed: Unnamed basin within Oakland (HUC 2204200400) MIROC-ESM RCP 8.5 (Hot/Dry) CNRM RCP 8.5 (Warm/Wet) Average Average Annual Average Annual Average Annual Average Annual Annual Data Data for 2025 - Data for 2090 - Data for 2025 - Data for 2090 - Climate or Hydrology for WY 1999 - 2034 2099 2034 2099 Metric 2008 (Historic) Projected Delta Projected Delta Projected Delta Projected Delta Daily Max Temperature,°C Annual Average 19.6 21.2 1.6 25.9 6.3 20.7 1.1 23.6 4 Daily Min Temperature,°C Annual Average 10.3 11.6 1.3 15.6 5.3 11.1 0.8 14.1 3.8

Precipitation, mm Annual Total 485 482 -3 369 -116 598 113 726 241 Runoff, mm Annual Total 8 4 -4 2 -6 27 19 49 41 Recharge, mm Annual Total 50 43 -7 22 -28 116 66 181 131 Potential EvapoTranspiration, mm Annual Total 1190 1233 43 1292 102 1225 35 1286 96 Actual EvapoTranspiration, mm Annual Total 425 438 13 348 -77 461 36 505 80 Climatic Water Deficit, mm Annual Total 767 795 28 979 212 758 -9 779 12

Don Edwards NWR

Figure 53. “Newark Slough (HUC 2205200003),” used to retrieve data for Don Edwards. Go to the live data: LINK Table 5. Watershed data for Don Edwards San Francisco NWR.

Don Edwards Data below is for this watershed: Newark Slough (HUC 2205200003) See also data for the larger watershed: Coyote Watershed MIROC-ESM RCP 8.5 (Hot/Dry) CNRM RCP 8.5 (Warm/Wet)

Daily Max Temperature,°C Annual Average 20.7 22.1 1.4 26.9 6.2 21.7 1 24.5 3.8 Daily Min Temperature,°C Annual Average 10.1 11.3 1.2 15.3 5.2 10.8 0.7 13.8 3.7 Precipitation, mm Annual Total 377 386 9 290 -87 476 99 580 203 Runoff, mm Annual Total 0 0 0 0 0 3 3 6 6 Recharge, mm Annual Total 5 5 0 1 -4 43 38 81 76 Potential EvapoTranspiration, mm Annual Total 1215 1254 39 1317 102 1242 27 1306 91 Actual EvapoTranspiration, mm Annual Total 369 380 11 293 -76 436 67 502 133 Climatic Water Deficit, mm Annual Total 845 871 26 1059 214 805 -40 804 -41

More Data and Information Online See these links to explore more for the Central Complex: • USGS Explore Your Watershed: San Francisco Bay Watershed Analyst • BCM Graphing Tool

Appendix III: Projections for the South Complex

Temperature Degrees of change for summer and winter months: Summer monthly average temperatures are projected to change 7.6°F from a 1980 baseline; winter average temperatures change approximately 5.7°F using the GFDL A2.

Figure 54. The "Hot-Dry" MIROC-ESM RCP 8.5 projects a more extreme rate of increase.

Figure 55. Maximum monthly temperatures annual averages from the three models. Note that the lowest average monthly maximum temperatures consistently exceed even the highest from the historic data after about the middle of the century.

Precipitation

Figure 56. "Warm-Wet" CNRM RCP 8.5 shows an increasing trend for annual average precipitation, with 79 the potential for high-end extremes above historic levels. GFDL A2 and the "Hot-Dry" MIROC ESM RCP 8.5 indicate a decreasing trend for annual average precipitation.

Figure 57. 30-year averages for projected compared to historical precipitation patterns over the water- year. All models still show the Mediterranean pattern of precipitation, with the potential for shifts in seasonality (possible earlier cessation of rainy

Aridity

Figure 58. All models indicate a steady drying trend indicated by an increase in annual average climatic

water deficit, with annual high-end extremes as much as 20% higher than historic levels in the second half of the century.

Seasonal water balance changes

Figure 59. This comparison of 30-year averages for the historical period of 1951-1980 and projected future period of 2070-2099 using the GFDL A2 model (with more moderate projected changes) shows a shift in hydrologic conditions ideal for plant growth (green- actual evapotranspiration) and an increase of length and intensity of the dry season with respect to both soil moisture (yellow) and climatic water deficit (red).

Below is a map created by the Pacific Institute portraying present-day coastal 100-year flood zones (light blue) and areas projected to flood in a 1.4 meter sea level rise scenario (dark blue) for the Watsonville West quadrangle. You may click on the image below to see the entire map, and go to the source to explore the data further.

Ellicott Slough and Salinas River NWRs

Figure 60. “Mouth of Pajaro River (HUC 3305100301),” used to retrieve data for Ellicott Slough and

Salinas River. Go to the live data: LINK

Table 6. Watershed data for Ellicott Slough and Salinas River NWRs.

Ellicott Slough and Salinas River Data below is for this watershed: Mouth of Pajaro River (HUC 3305100301) See also data for these Alisal-Elkhorn Sloughs larger watersheds: Pajaro Watershed and Watershed MIROC-ESM RCP 8.5 (Hot/Dry) CNRM RCP 8.5 (Warm/Wet) Average Average Annual Average Annual Average Annual Average Annual Annual Data Data for 2025 - Data for 2090 - Data for 2025 - Data for 2090 - Climate or Hydrology for WY 1999 - 2034 2099 2034 2099 Metric 2008 (Historic) Projected Delta Projected Delta Projected Delta Projected Delta

Daily Max Temperature,°C Annual Average 19.2 21.3 2.1 26.1 6.9 20.6 1.4 23.3 4.1 Daily Min Temperature,°C Annual Average 8.5 9.6 1.1 13.6 5.1 9 0.5 12 3.5 Precipitation, mm Annual Total 544 556 12 411 -133 686 142 858 314 Runoff, mm Annual Total 0 0 0 0 0 11 11 24 24 Recharge, mm Annual Total 67 48 -19 23 -44 177 110 297 230 Potential EvapoTranspiration, mm Annual Total 1211 1254 43 1322 111 1242 31 1304 93 Actual EvapoTranspiration, mm Annual Total 474 508 34 393 -81 504 30 546 72 Climatic Water Deficit, mm Annual Total 735 743 8 967 232 731 -4 761 26

More Data and Information Online See these links to explore more for the South Complex: • USGS Explore Your Watershed: Pajaro • Watershed Analyst • BCM Graphing Tool