Climate Change and San Francisco Bay-Delta Tidal Wetlands V.T. Parker San Francisco State University and L.M. Schile, J.C. Callaway & M.C. Vasey San Francisco State University and University of San Francisco

Context: Focal Area for Research

SF Bay-Delta Tidal Marshes Salinity Gradient Brackish Marshes Salt Marshes Freshwater Marshes in the Delta

Historic marshes along gradient China Camp Coon Island Browns Island

Pond 2A Carls Bull Island Restored marshes along the gradient Pond 3

San Francisco Bay Tidal Marshes Brackish Marshes Salt Marshes Freshwater Marshes in the Delta Species Diversity 2-22 species Species Diversity species Species Diversity 117+ species Species Diversity

San Francisco Bay Tidal Marshes Brackish Marshes Salt Marshes Freshwater Marshes in the Delta Annual Primary Production ANPP g m -2 yr -1 ANPP g m -2 yr g m -2 yr -1

SF Bay-Delta: Freshwater> Salt Marshes Freshwater tidal marshes have 5-50 times more species than salt marshes Freshwater tidal marshes have 3-12 times more primary production Historic marshes have more species than restored marshes

What happens to these systems under projected climate change?

Processes predicted to change… Increases in CO2 Rising temperatures More rain/less snow->reduced snowpack-> reduced water flow in Bay-Delta in late summer Reduced water flow->increased salinity Rising sea level

Increase in atmospheric CO 2 concentration Generally good for C 3 plants at beginning –Most wetland plants use C 3 photosynthesis Generally no improvement for C 4 plants (meaning net relative loss of productivity) –Spartina foliosa and Distichlis spicata are two common C 4 plants in SF Bay-Delta marshes

6 global climate models for each of 4 different historic and future scenarios. Northern California will increase in temperature. The models are ambivalent about precipitation, but greater unpredictability Dettinger 2005 Temperature regime increases

Temperature effects on wetlands Direct Indirect

Direct effects-temperature Influence on photosynthesis/respiration balance of dominant plants rate temperature respiration photosynthesis

Direct effects-temperature Influence on photosynthesis/respiration balance of dominant plants rate temperature Mortality Increase in ANPP Decrease in ANPP

Indirect Effects-temperature Sierran snow pack melts earlier Rivers flow earlier Salinity increases upstream Salinity (ppt)

Salinity (ppt) Current Summer Salinities Projected Summer Salinities in 2060 Figure from Noah Knowles Projected Salinity Changes Critical

Salinity Effects on Tidal Wetlands Shifts composition Reduces diversity Reduces productivity Inhibits organic peat production Changes soil structure Critical thresholds at low salinity levels

(from IPCC) Indirect effects, cont. Increase in the rate of sea level rise

Inundation and flooding current conditions

Marsh Surface Elevations : Percent Time Wet Restored sites are inundated longer than natural sites Number of Observations Bull Island Pond 2a Carl’s Marsh Restored Sites Coon Island Browns Island Reference Sites

Bull Island Pond 2a Carl’s Marsh Restored Sites Coon Island Browns Island Reference Sites Diversity peaks at MHHW at reference sites; lower at restored sites Number of Species Marsh Surface Elevations : Plant Diversity Mean high water - MHW Mean higher high water - MHHW MHW MHHW

Coon Island MTLMHWMHHW c a b b c b c a b b c b Within a site, elevation predicts distribution of species

Larry Allian Formerly known as Scirpus acutus Schoenoplectus acutus tule a b c a a a Among sites, % inundation time predicts distribution

Bolboschoenus maritimus Alkali bulrush Formerly known as Scirpus maritimus ab c d a b c c

Schoenoplectus americanus Common three-square Formerly known as Scirpus americanus a b c a b a

Formerly known as Salicornia virginica Sarcocornia pacifica Pickleweed a b c a a b c c

Site-level Elevation and Inundation Patterns Restored sites differ in length of inundation, and elevation at which species diversity peaks Elevation important in determining plant distributions within sites Among sites, inundation patterns for any species are relatively similar, but elevations may differ Salinity another influence needing consideration

Likely influences of climate change on tidal wetlands Negative impacts –Increase in inundation –Increase in salinity –Increase in temperature? Positive impacts –Increase in CO 2 –Increase in temperature? Restored marshes lagging behind reference sites

Given environmental change –If temperature increases… –If salinity increases… –If marsh substrate accretion fails to keep up with sea level rise and inundation increases… What might be a predictable scenario for SF Bay-Delta?

Sarcocornia pacifica: Sarcocornia occurs in a diversity of salinity and inundation conditions formerly Salicornia virginica

Sarcocornia pacifica: Used spatially variability as a natural experiment to ask the question: What happens to Sarcocornia productivity under higher salinities and more inundation? Multiple harvests to assess annual production under a variety of salinity and inundation conditions

While annual productivity increases with height… The pattern with salinity seems scattered and complex…

Until well-drained locations are separated from poorly-drained sites... Well-drained plots Poorly-drained plots

Results: Natural Experiment Increases in salinity and inundation (predicted environmental changes)… Result in significant reductions in wetland productivity in the species most likely to expand low productivity?

Conclusions Reducing the rate of change in wetlands: depends on maintaining or enhancing freshwater flows into the Delta in the summer/fall periods (levee protection, less diversion) Restoring new marshes sooner might increase their likelihood of long-term success and persistence

What haven’t I mentioned? Temperature, salinity, inundation all strongly influence other major ecosystem processes within wetlands that have strong links to terrestrial and pelagic systems: –Decomposition –Soil organic matter accumulation –Every aspect of nitrogen dynamics –Plant composition shifts, seedling establishment, seed bank persistence

To keep from getting stuck in the details…

Ppt Shifts from Snow to rain Smaller Snowpack Earlier melt Spring floods Increasing Temperatures Lower Summer flows Global Warming Impact on SF Bay-Delta Increased Estuarine salinity Sea level Rise Increased inundation Reduced Peat formation CO 2 increases mixed

these environmental changes impact the performance of wetland vegetation: …and potentially lead to:

Loss of species, reduction in annual productivity, with cascading effects on linked terrestrial and pelagic systems… Acknowledgements: …CA Parks, CA Fish & Game, EB Regional Park District, a large and excellent field crew, and colleagues in the IRWM project …meaning marshes may fade to blue