1. Research and monitoring at Elkhorn Slough:
improved conservation through understanding

2. CONSERVATION RESEARCH
At Elkhorn Slough Reserve

3. PLACE-BASED SCIENCE

4. LONG-TERM MONITORING

5. CITIZEN SCIENTISTS

7. INFORMING MANAGEMENT

8. RESTORATION EXPERIMENTS

9. SALT MARSH ECOLOGY

10. SALT MARSH ECOLOGY Marsh values Marsh habitat requirements
Threats and what we can do about them
Marshes and sea level rise

11. SALT MARSH VALUES Rare habitat type Unique plants Support for animals
Improved water quality
Shoreline protection
Carbon sequestration

12. Salt marshes are rare on this coast

13. Few estuaries in California
At scale of whole coast, very few estuaries with more than a few hundred acres of habitat.
Much less habitat than this picture suggests – dots are much too large for all except SF Bay
Like archipelago of islands – not continuous habitat

14. UNIQUE PLANTS
found in salt marshes

15. PICKLEWEED - Salicornia
Dominant in low marsh

16. High marsh plants Dodder – Cuscuta on pickleweed
Salt grass – Distichlis
About 40 % of cover in ecotone is pickleweed, about 30% is upland plants

17. High marsh plants Atriplex – Spear scale Frankenia – alkali heath
About 40 % of cover in ecotone is pickleweed, about 30% is upland plants
Jaumea
Grindelia – gum plant

18. BIRDS USE MARSH HABITAT

23. MARSH PROVIDES REFUGE FOR MARINE MAMMALS

25. WILDLIFE USE OF
MARSH-UPLAND ECOTONE

26. MARSH DETRITUS SUPPORTS ESTUARINE FOOD WEBS

27. MARSHES CAN TRAP POLLUTED RUN-OFF

30. SHORELINE PROECTION
From wind waves & storms

31. “BLUE CARBON”
Carbon sequestration

32. Measuring carbon sequestration

33. Measuring gas emissions

34. SALT MARSH VALUES Rare habitat type Unique plants Support for animals
Improved water quality
Shoreline protection
Carbon sequestration

35. SALT MARSH ECOLOGY Marsh values Marsh habitat requirements
Threats and what we can do about them
Marshes and sea level rise

36. WHAT SALT MARSHES NEED
Light
Nutrients
Moisture
Soil

37. Light: generally not limiting

38. Nutrients: supplied by ocean and freshwater

39. Moisture: some freshwater, but mostly salt water

40. Moisture: CRITICAL!!! Too little tidal inundation:
desiccation and competition from upland plants
Too much tidal inundation:
roots don’t get enough oxygen and plants drown

41. IT’S ALL ABOUT ELEVATION

42. Lower areas:
drowned marsh
Higher areas:
healthy marsh

43. Lower areas:
drowned marsh
Higher areas:
healthy marsh

44. Soil: CRITICAL!!! Horizontal processes:
Banks retreat if sediment supply is to low

45. Marsh plain needs to build upward to track rising seas
Soil: CRITICAL!!!
Vertical processes:
Marsh plain needs to build upward to track rising seas

46. From D. Cahoon

47. HORIZONTAL:
EXPANSION OR RETREAT OF EDGE
VERTICAL:
UPWARD GROWTH OF MARSH PLAIN TO TRACK SEA LEVEL

48. MARSH DROWNING
Due to insufficient external sediment supply or insufficient organic matter internally to build soil

50. WHAT SALT MARSHES NEED Light: usually not an issue
Nutrients: not too much or little
Moisture: not too much or little (elevation!)
Soil: need to keep building up to track SLR

51. SALT MARSH ECOLOGY Marsh values Marsh habitat requirements
Threats and what we can do about them
Marshes and sea level rise

52. THREATS TO SALT MARSHES and what we can do about them
Diking
Erosion
Decreased freshwater inputs
Eutrophication
Trampling
Invasions

53. DIKING/DRAINING MARSHES

54. LEGACY OF DIKING: SUBSIDENCE

56. LEGACY OF DIKING: SUBSIDENCE

57. 1870 2000 Sediment addition project From Van Dyke & Wasson 2005
Minhoto restoration site is circled
Sediment addition project
From Van Dyke & Wasson 2005

58. SEDIMENT ADDITION
To restore elevation and marsh

59. ARTIFICIAL HARBOR MOUTH

60. MARSH BANK EROSION

61. DECREASE TIDAL CURRENTS
Parsons Sill project

62. FRESHWATER INPUTS DECREASED
Problem because marshes need sediments that come with rivers, and marsh diversity requires some freshwater inputs.
Estuary is where river meets the sea – but freshwater inputs have been greatly decreased to Elkhorn.
Groundwater overdraft has led to the vanishing of artesian wells and freshwater all along margins. See loss of brackish plants, hear about from beth today
Also rivers and creeks don’t flow freely into the estuary anymore.

63. EUTROPHICATION

65. ALGAL WRACK AND MARSH

66. DECREASED PLANT HEALTH

67. VEGETATION RETREAT AND BANK EROSION marsh retreat rate (cm/yr)
R2 = 0.62, P =
marsh retreat rate (cm/yr)
Wrack index

68. CATTLE TRAMPLING
Cattle grazing tool used by land managers for adjacent grasslands, increases native forbs
At similar densities, not beneficial for marsh and ecotone
(we had about 1 cow/hectare for this study)

69. CATTLE TRAMPLING
Fencing prevents harm

70. HUMAN TRAILS

71. BOARDWALKS PROTECT MARSH

72. NON-NATIVE PLANT INVASIONS
poison
hemlock
ice
plant
MARSH
MARSH

73. ICE PLANT REMOVAL

74. THREATS TO SALT MARSHES and what we can do about them
Diking>>>restore tides, add sediment
Erosion>>>reduce currents
Decreased freshwater inputs>>>restore some
Eutrophication>>>decrease nutrients
Trampling>>>limit access
Invasions>>>prevent and restore

75. SALT MARSH ECOLOGY Marsh values Marsh habitat requirements
Threats and what we can do about them
Marshes and sea level rise

77. GREENHOUSE GAS INCREASES
Sharp climb in past 100 yrs

78. SEA LEVEL RISE
High uncertainty, but major increases projected

79. WARMING CAUSES SEA LEVEL RISE

80. SEA LEVEL RISE PROJECTIONS

81. KING TIDES OFFER PREVIEW

82. MONTEREY TIDE STATION
Sea level rise still moderate

83. MONTEREY TIDE STATION
Short term high water levels

84. Dieback of lower edge of marsh: High water levels during El Nino

85. RESILIENCE TO SEA LEVEL RISE
Existing marshes tracking SLR; marsh survives in current area
Migration of marshes upward; marshes occupy new areas

86. Coastal Marsh
MHW
intertidal
MLW

87. Rapid sea level rise = marsh drowning
MHW
intertidal
MLW
SEA LEVEL RISE
If a tidal marsh has an adequate sediment supply, it responds to sea level rise by accumulating sediments.
Examples: 1. South San Francisco Bay and groundwater overdraft
2. sediment accumulation data from the past decades in the Mid-Atlantic (sediment accumulation appears to track tide cycles)

88. Adequate sediment or slow SLR = survival
MHW
intertidal
MLW
organic
sediment
If a tidal marsh has an adequate sediment supply, it responds to sea level rise by accumulating sediments.
Examples: 1. South San Francisco Bay and groundwater overdraft
2. sediment accumulation data from the past decades in the Mid-Atlantic (sediment accumulation appears to track tide cycles)

89. RESILIENCE TO SEA LEVEL RISE Factors that help existing marshes
Marsh elevation>>>high marshes safer
Tidal range>>>larger range provides buffer
Elevation change>>>rising marshes safer
Sediment supply>>>more helps track SLR
Eutrophication>>>can cause subsidence
Groundwater overdraft>>>ditto

90. Surveying elevation of marshes

92. Measuring marsh elevation change

93. Measuring sea level

94. Elkhorn Slough resilience:
Sea level rise: +1.4 mm/yr
(and increasing)
Marsh accretion: mm/yr
Marsh subsidence: mm/yr
Net elevation gain: +0.9 mm/yr
Not enough….

95. How resilient are US marshes in the face of sea level rise?
Analysis across the National Estuarine Reserves
LDD
Legend
Number of metrics (of 10) that show high risk 1 2 3 4
>5

96. RESILIENCE TO SEA LEVEL RISE
Existing marshes tracking SLR; marsh survives in current area
Migration of marshes upward; marshes occupy new areas

97. BATHTUB RING
Narrow band of marsh may result from upward migration on steep slopes

99. SEA LEVE RISE PROJECTIONS
NOAA’S SEA LEVEL RISE VIEWER

101. HOW CAN WE SUPPORT MARSH RESILIENCE?

102. SUPPLY SEDIMENT

103. DECREASE OTHER STRESSORS

104. FACILITATE MIGRATION

105. UNDERSTAND, APPRECIATE, CONSERVE AND RESTORE OUR SALT MARSHES!