1 Variable marsh resilience to stress offers clues to climate changeadaptive management 2014 2015 The same plot, one year apart Roger Fuller Western Washington University Katrina Poppe, WWU John Rybczyk, WWU Eric Grossman, USGS Chad Stellern, WWU

2 The Take-Home MessagesClimate change interacts with existing sources of stress, and changes the rules and the timeline of response. 2. Resilience to stress differs spatially across the estuary. (and each estuary is different) 3. Understanding why resilience varies, allows you to identify strategies to enhance resilience now.

3 The Stillaguamish Estuary2012 Restoration Marsh retreat Tidal marsh: dominated by 4 bulrushes in the middle to low marsh, and graminoids in high marsh. No tidal shrub or swamp left. Marsh expansion

4 Habitat Drivers (resilience factors)Circulation Patterns Sediment Salinity Water levels Estuary ecosystem species diversity ecosystem services habitat complexity etc.

5 Climate change stress Salinity2050’s Projection for 2-year low flow: 30-40% decline

6 Summer 2015: same as 2050’s average conditionPore Water Salinity Bulrush salinity tolerance threshold CC effects on salinity vs temp allowing growing season to shift earlier

7 Sea level rise and AccretionClimate Change Stress Sea level rise and Accretion Elevation Change (cm/yr) plenty …of sediment for the marshes Rybczyk and Poppe

8 Sediment delivery in future?2080s, Skagit River River Flow Hamlet et al. (2016) Sediment Load (MT/month) 4 3 2 1 2010 Suspended sediment Historic Avg.

9 Other sources of stress that interact with climate changeBiotic changes: herbivores, bioturbators and insects Waves Legacy stresses…levee configuration effects on delivery of freshwater and sediment

10 Goose herbivory – overgrazing results in erosion and marsh lossDisturbance - herbivory Goose herbivory – overgrazing results in erosion and marsh loss Keith Lazelle

11 Herbivory interacts with Wave Exposure High Wave Exposure Low Wave

12 Insect-mediated Marsh Dieback2015: Stress + Insect = 50 acre dieback Bore holes Preliminary ID: Bactra sp. (Tortricidae)

13 Interacting stresses kill marsh2014 2015 Highest elevation marsh Interacting stresses kill marsh Lowest elevation marsh

14 Summer: Range of Conditions Sediment and Wave SeasonBiophysical Interactions: Vegetation structure Summer: Range of Conditions Winter Sediment and Wave Season Scam Boma-Scam Vegetation – structure affects hydro and sediment dynamics Different species have different structure Scta-Boma-Scam Bofl-Boma-Scam

15 Biophysical Interactions and Disturbance Resilience

16 Effects of high salinity on vegetationearly senescence decreased biomass reproductive failure 2015 % Reduction in vegetation height

17 Marsh retreat…multiple interacting stressorsLow Marsh Boundary 1964 2004 21 m/yr 5 m/yr 1964 Low Marsh Boundary

18 Summary Varied sources of stress, expect more in the futureClimate changes effects interact with existing stresses Salinity is likely an earlier and bigger threat than SLR Understanding the biophysical interactions driving resilience allows spatially targeted strategies

19 Adaptation Action ExamplesSalinity – earliest big threat from climate change 1. Restoration focus: freshwater and sediment delivery higher in estuary, close to river mouth, distributaries 2. Maximize hydroconnectivity between restoration site and system 3. Fill and grade subsided restoration sites, target elevations and particle size to support resilient plant species e.g. Bolboschoenus fluviatilis, river bulrush 4. Dredged sediment beneficial reuse 5. Engineered LWD jams: channel stabilizing, sediment capture, wave attenuation 6. Snow goose management, behavior modification

20 Monitoring Metrics to Understand Biophysical InteractionsPore water salinity (especially the next dry summer) Vegetation height and density (summer, winter) Common plant species Accretion (feldspar and grid horizons) Elevation change (Sediment Elevation Tables) Soil particle size distribution Disturbance index

21 Thanks! Roger Fuller Western Washington UniversityJen Moslemi Thanks! Roger Fuller Western Washington University Acknowledgements Colleagues: Katrina Poppe, John Rybczyk, Eric Grossman Grad Students: Brittany Jones, Chad Stellern Field crew members: James McArdle, Sarah Thomas, Abe Lloyd, Adam Schnellbaecher, Christian Aguilar, Devin Debono, Andy Cortese, Alec Barber, Katy Hancock, Kaylee Guetle. Funding: The Nature Conservancy, ESRP, NOAA