nyc tidal marsh assessment: condition, vulnerability and...
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NYC Tidal Marsh Assessment: Condition, Vulnerability and Restoration OpportunitiesChristopher Haight1, Marit Larson1, Rebecca Swadek1, Ellen K. Hartig1, Nicole Maher2, Stephen Lloyd2, Lauren Alleman2, and Helen M. Forgione3
NYC Parks - Natural Resources Group 1
The Nature Conservancy2
Natural Areas Conservancy 3
NCERApril 20, 2016
Why Urban Coastal Wetlands
• Coastal wetlands are a critical part of a livable NYCo resilient Park assetso aesthetic, recreational and educational valueo ecosystem services (fisheries, bird communities, water quality)
• Coastal wetlands are at risk
• Planning, management and restoration can help protect our wetland assets for the future
Historic NYC Wetland Extent
Current NYC Tidal Wetlands
Project Goals
• Assess current marsh condition
• Evaluate vulnerability (SLR)
• Identify opportunities for protection, conservation & restoration
Prioritize restoration & protection opportunities
Ecological Assessment at 25 salt marshes
Long Island Sound
Staten Island
Jamaica Bay
Desktop AnalysisoHistoric Loss
AnalysisoSLAMM
Rapid Ecological AssessmentsoMidTRAMoMarsh-wide
assessments
7
Marsh area
% Development in buffer
Species richness
Total cover
Low marsh soil strength
Breeding bird count
Bare soil cover
Pool expansion
Ditch density
Identify key ecological attributes of marsh condition for which there are measurable indicator variables:
Percent high marsh
Marsh area
Edge density
Waterward loss
Potential gain from migration
Potential loss by SLR
Identify key measurable indicators of vulnerability available from SLAMM outputs, field and desktop assessments
Idlewild Park, Queens, NYSalt marsh
Recently lost salt marsh
Sea Level Affecting Marshes Model (SLAMM)
10
Likelihood of Coastal Marsh 2080sIdlewild Park
Example – Saw Mill Creek Marsh, Staten Island
-2 -1 0 1 2 3
Marsh Area
Native Species Richness
Low Marsh Soil Strength
Bare Peat Coverage
Ditch Density
Z-Score
Condition
-5 -4 -3 -2 -1 0 1 2
Marsh Area
Potential Marsh Loss to SLR
Potential Gain from Migration
Trend in Waterward Marsh Loss
Edge Density
Percent High Marsh
Total Score
Z-Score
Vulnerability
Alley Creek Inner
Alley Creek Outer
Hutchinson Inner
Hutchinson Outer
Pelham Bay Cove
Pugsley Creek Marsh
Turtle Cove
Udall's Cove Marsh
Westchester Creek
Four Sparrow
Fresh Creek MarshIdlewild Marsh Inner
Idlewild Marsh Outer
Spring CreekArlington Marsh
Fresh Kills Marsh
Lemon Creek Inner
Lemon Creek Outer
Neck Creek Inner
Neck Creek Outer
Richmond Creek
Saw Mill Creek InnerSaw Mill Creek Outer
W. T. Davis Inner
W. T. Davis Outer
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-1.5 -1 -0.5 0 0.5 1 1.5 2
Bronx/Queens
Jamaica Bay
Staten Island
Higher condition/Lower Vulnerability Higher condition/Higher Vulnerability
Lower condition/Higher VulnerabilityLower condition/Lower Vulnerability
Marsh Condition vs. Vulnerability
Long Island Sound
Marsh Area and Shape Explain Trends in Condition and Vulnerability Variables
R2 = 0.70
R2 = -0.89
Short/Mid-Term: Increase viability of existing marsh sites Remove fill and re-establish hydrology Remove debris and revegetate• Increase elevation of drowning marsh surface• Restore shore edge of marsh where eroded
Long Term: Assure sustainability of marsh ecosystems• Secure adjacent parcels where marsh can
migrate• Remove hard surfaces that impede marsh
migration
Identify and prioritize strategies for restoration
Actions Threats Targets
Long Term Viability & Function of NYC
Saltmarshes in
Study Area
Obstacles to Marsh Migration
Acquisition/Transfer
Restore Flooded Developed lands
Reduced Capacity for Vertical GrowthElevation
Enhancement
Erosion and Decreased Size
Rebuild Marsh Edge
Opportunities for Restoration / Conservation
Current Marsh Future Marsh with SLR
Ownership across 25 NYC Marsh complexes
Acquisition/ Transfer
36 ac
838 ac
63 ac
Future new marsh acres in Study Area
0
10
20
30
40
50
60
Acre
s
Private
City/State/Federal
NYC Parks
Acquisition of advancement zones
Restore Flooded Developed lands
Action prioritized by area of opportunity
Elevation Enhancement
Action prioritized by % low marsh and future marsh loss in SLAMM
Rebuild Marsh Edge
Action prioritized by acres, width and % of recent marsh lost and future marsh loss in SLAMM
Are these a better long-term investment?
Is there anything we can do to save marshes that are highly vulnerable to begin with?
Watershed / Water-body Considerations
-1-0.8-0.6-0.4-0.2
00.20.40.60.8
1
BQ JB SI
JB LIS SI
Focus on watershed – specific needs• SI = Acquire and transfer
parcels
• JB = Restore elevation
• LIS = Address Edge Extension uncertainty
Appropriate strategy depends on goals, landscape context, time horizon, and socioeconomic factors
• Preserve existing marsh ecosystems and marsh migration zones for future – explore acquisition and easement strategies
• Prioritize high condition / low vulnerability marshes through best management practices and these 4 conservation strategies as neededo Address uncertainty - study shoreline retreat, sediment
supply, and wave energyo Consider size and shape - conserve and restore to reduce
fragmentation for long term health and viability
• Consider socio-economic or ecosystem services when pursuing opportunities for low condition / high vulnerability marshes
• Consider a watershed approach to conserving wetlands in addition to site by site restoration projects.
Next Steps
NYC Parks - Natural Resources GroupChristopher HaightMarit LarsonRebecca SwadekEllen K. Hartig
Natural Areas Conservancy Helen M. Forgione
The Nature ConservancyNicole MaherStephen LloydLauren Alleman
Funding from U.S. EPA Region 2, Wetlands Protection Program Development Grant
Kathleen Drake