Effects of Accelerated Sea Level Rise on

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Effects of Accelerated Sea Level Rise on
Biogeochemical Cycles of Tidal Marshes of the
Southeast U.S. Coast A Landscape Simulation
Christopher Craft (Indiana University) Jonathan
Clough (Warren Pinnacle Consulting Richard Park
(Eco Modeling) Jeff Ehman (Image Matters LLC)
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Tidal salt marsh - Spartina alterniflora
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Tidal brackish marsh Juncus roemerianus
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Tidal freshwater marsh Zizaniopsis milacea
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Ecosystem Services

• Shoreline protection
• Retention of carbon, nitrogen, phosphorus

• Gas exchange (CO2, CH4, N2O)
• Support of higher trophic levels

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Land
Sea
Tidal fresh-water marsh
Salt marsh
Regulation Functions Shoreline Protection CO2
CH4 Flux Carbon sequestration NP
retention Sediment Deposition Denitrification
Habitat Functions Macrophyte
Diversity Marsh Nekton Productivity
Functions Macrophyte Productivity Marsh Nekton

Predictions largely based on William E. Odum 1988
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How will accelerated sea level rise (SLR)
affect the distribution of tidal marshes AND
their delivery of ecosystem services?
Wetland Habitat Ecosystem Services ?
Reduced salt and brackish ? Reduced
regulation functions marsh habitat
(shoreline protection, CH4 CO2
flux, carbon sequestration, NP ? Complete loss
of tidal retention, denitrification,
freshwater marsh sediment deposition)
? Increased submerged land ?
Reduced habitat functions (plant
diversity) ? Reduced production
functions (plant productivity, marsh
nekton,
commercial shrimp yield)
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Methods

• Quantify ecosystem services of salt,
• brackish and tidal fresh marshes (Georgia).
• Overlay ecosystem services on GIS
• representation of National Wetlands
• Inventory (NWI) maps.
• Simulate different scenarios of accelerated
• SLR to predict change in wetland area, type
• and delivery of ecosystem services.
• Scale to southeast (SC-GA) coast.

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Three estuaries
Measurement of Ecosystem Services

• Altamaha
• Ogeechee
• Satilla

Three marsh types

• Tidal fresh
• Tidal brackish
• Tidal salt

3 estuaries / 3 marsh types / 2 sites, n18 sites
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Altamaha River brackish marsh
Measurement of Ecosystem Services Carbon
Sequestration in Soil as an Example
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Carbon Sequestration in Soil
110 18 A
118 6 A
42 1 B
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Nitrogen Accumulation in Soil
7.8 1.0 A
7.8 0.6 A
2.6 0.1 B
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Phosphorus Accumulation in Soil
1.08 0.17 A
0.66 0.04 A
0.28 0.05 B
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Mineral Soil Accumulation
1120 45 A
807 86 B
488 77 B
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Denitrification
Potential Denitrification
(g/m2/yr) --------------------------------
-- Tidal fresh marsh 22 Brackish
marsh 4.0 Salt marsh 6.0

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SLAMM Version 5 (beta) (Sea Level
Affects Marshes Model)
SLAMM uses elevation, NWI, tide range, historic
sea level rise and site-specific accretion rate
data to parameterize the model. A salinity
algorithm is used to simulate saltwater
intrusion into river-dominated estuaries as sea
level rises. The simulation is run using A1B
SRES (mean) scenario.
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The Altamaha River Estuary (Georgia) as an Example
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Altamaha River (1986)
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1986
2025
2050
2100
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SLAMM simulation of the effects of accelerated
SLR on the southeast (GA-SC) coast
2100
South Carolina
Ogeechee R.
Altamaha R.
Georgia
Satilla R.
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SLAMM simulation of the effects of accelerated
SLR on the southeast (GA-SC) coast
Initial Conditions Year 2100 Loss
(km2) (km2) () --------
---------------- -------------- ------- Dry
land 14450 12720 12 Non-tidal
swamp 6070 2180 64 Tidal fresh swamp 810
310 62 Inland fresh marsh 280
265 5 Tidal fresh marsh 370
220 41 Brackish marsh 630 530 16 Salt
marsh 2350 2280 3 Tidal flat 50 13
74 Estuarine open water 1850 2830 65
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C, N, P Sequestration in Soil
Wetland C N P
Change (km2) MT/yr MT/yr MT/yr ------
------ ---------- ---------- -------- Tidal
fresh -150 -17,700 -1,170 -100 Brackish
-100 -12,000 - 780 -110 Salt marsh
- 70 - 3,000 - 130 -
20 Cumulative -320 -32,700 -2,080 -230
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Sediment Deposition Denitrification
Wetland Change Sediment N
(km2) ------- MT/yr
-------- ------------------------ ------------
-- ------- Tidal fresh -150 -120,000 -3330 Bra
ckish marsh -100 -110,000 - 400 Salt
marsh - 70 -30,000 -
400 Cumulative -320 -260,000 -4100
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Summary

• Different types of tidal marshes provide
  different levels of ecosystem services.
• Sea level rise will reduce the area of different
  types of tidal marshes.
• By combining estimates of both area and services,
  we hope to forecast how net marsh ecosystem
  services will change with rising sea level and
  changing climate (e.g. variable freshwater
  discharge).

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Caveats

• Projected changes in marsh type may not be
  perfect.
• Marsh accretion rates may increase as sea level
  rises.
• Nevertheless, this work is novel because it will
  combine projections of wetland area change with
  wetland-specific measurements of ecosystem
  services.
• Further simulations can explore areas of
  uncertainty.

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Questions?