U.S. Geological Survey.
U.S. Fish and Wildlife Service.
Structured decision making is a systematic, transparent process for improving the quality of complex decisions by identifying measurable management objectives and feasible management actions; predicting the potential consequences of management actions relative to the stated objectives; and selecting a course of action that maximizes the total benefit achieved and balances tradeoffs among objectives. The U.S. Geological Survey, in cooperation with the U.S. Fish and Wildlife Service, applied an existing, regional framework for structured decision making to develop a prototype tool for optimizing tidal marsh management decisions at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia. Refuge biologists, refuge managers, and research scientists identified multiple potential management actions to improve the ecological integrity of six marsh management units within the refuges, totaling about 575 hectares, and estimated the outcomes of each action in terms of performance metrics associated with each management objective. Value functions previously developed at the regional level were used to transform metric scores to a common utility scale, and utilities were summed to produce a single score representing the total management benefit that could be accrued from each potential management action. Constrained optimization was used to identify the set of management actions, one per marsh management unit, that could maximize total management benefits at different cost constraints at the refuge scale. Results indicated that, for the objectives and actions considered here, total management benefits may increase consistently up to approximately $143,000, but that further expenditures may yield diminishing return on investment. Potential management actions in optimal portfolios at total costs less than $143,000 included digging runnels by hand to improve drainage from the marsh surface, breaching a road to restore natural hydrology, trapping predators to enhance nest success of tidal marsh birds, and reducing the abundance of
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Photograph of ESV Marsh in the Eastern Shore of Virginia National Wildlife Refuge, Cape Charles, Virginia; photograph by the U.S. Fish and Wildlife Service.
The U.S. Fish and Wildlife Service (FWS) provided exceptional hospitality at the Eastern Shore of Virginia National Wildlife Refuge, Cape Charles, Virginia, for the 2018 structured decision-making workshop, which included participants from two additional national wildlife refuge administrative units. Nathan Bush of the FWS generated the mapping data used in this report, and Jackie Olson of the U.S. Geological Survey expertly prepared the maps. Technical reviews by Rachel Katz of the FWS and Bill Thompson of the National Park Service greatly improved the quality of this report.
Multiply | By | To obtain |
meter (m) | 3.281 | foot (ft) |
kilometer (km) | 0.6214 | mile (mi) |
square meter (m2) | 0.0002471 | acre |
hectare (ha) | 2.471 | acre |
Vertical coordinate information is referenced to the North American Vertical Datum of 1988 (NAVD 88).
Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).
Elevation, as used in this report, refers to distance above the vertical datum.
U.S. Fish and Wildlife Service
national wildlife refuge
U.S. Geological Survey
The National Wildlife Refuge System protects extensive salt marsh acreage in the northeastern United States. Much of this habitat has been degraded by a succession of human activities since the time of European settlement (
Structured decision making is a systematic approach to improving the quality of complex decisions that integrates assessment metrics into the decision process (
Map showing national wildlife refuges and national wildlife refuge complexes of the U.S. Fish and Wildlife Service where salt marsh integrity was assessed from 2012 to 2016 using the regional monitoring protocol.
Figure 1. Map showing national wildlife refuges and national wildlife refuge complexes of the U.S. Fish and Wildlife Service where salt marsh integrity was assessed from 2012 to 2016 using the regional monitoring protocol
The Eastern Shore of Virginia National Wildlife Refuge protects 180 hectares (ha) of salt marsh at the southern end of the Delmarva Peninsula, in Northampton County, Virginia, between the Atlantic Ocean and Chesapeake Bay (
Map showing salt marsh management units at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia. U.S. Fish and Wildlife Service managed areas shown for reference.
Figure 2. Map showing salt marsh management units at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia
This report describes the application of the regional structured decision-making framework (
The Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges are located at the southern tip of the Delmarva Peninsula (
A regional framework for assessing and managing salt marsh integrity at northeastern NWRs was developed through collaborative efforts of FWS regional and refuge managers and biologists, salt marsh research scientists, and structured decision-making experts. This process followed the discrete steps outlined by
Clarify the temporal and spatial scope of the management decision.
Define objectives and performance measures to evaluate whether objectives are achieved.
Develop alternative management actions for achieving objectives.
Estimate the consequences or likely outcomes of management actions in terms of the performance measures.
Evaluate the tradeoffs inherent in potential alternatives and select the optimum alternatives to maximize management benefits.
This sequence of steps was applied through successive workshops to refine the decision structure and incorporate newly available information. Initial development of the structured decision-making framework occurred during a week-long workshop in 2008 to define the decision problem, specify management objectives, and explore potential strategies available to restore and enhance salt marsh integrity. During 2008 and 2009, workshop results were used to guide field tests of salt marsh monitoring variables (
From the outset, FWS goals included development of an approach for consistent assessment of salt marsh integrity across all northeastern NWRs (
Table 1. Objectives hierarchy for salt marsh management decision problems
[Two fundamental objectives (overall goals of the decision problem) draw directly from U.S. Fish and Wildlife Service (FWS) National Wildlife Refuge System policy to maintain, restore, and enhance biological integrity, diversity, and environmental health within the refuges. These are broken down into lower level objectives focused on specific aspects of marsh structure and function. Values in parentheses are weights assigned to objectives, reflecting their relative importance. Weights on any branch of the hierarchy (that is, objectives that are at the same level of the hierarchy under a fundamental objective) sum to one. The weight for each metric is the product of the weights from each level of the hierarchy leading to that metric. See also
FWS objectives | Performance metrics | Unit of measurement |
Maximize biological integrity and diversity1 (0.5) | ||
---|---|---|
Maximize cover of native vegetation (0.24) | Cover of native vegetation | Percent |
Maximize abundance and diversity of native nekton (0.18): | NA | NA |
Maximize nekton abundance (0.50) | Native nekton density | Number per square meter |
Maximize nekton diversity (0.50) | Native nekton species richness | Number of native species |
Maintain sustainable populations of obligate salt marsh breeding birds (0.20) | Abundance of four species of tidal marsh obligate birds ( |
Number per marsh management unit from call-broadcast surveys, summed across all sampling points in unit |
Maximize use by nonbreeding wetland birds (0.20) | Abundance of American black duck as indicator species | Relative abundance for refuge during wintering waterfowl season (low, medium, high)2 |
Maintain trophic structure (0.18) | Density of spiders as indicator taxon | Number per square meter |
Maximize environmental health1 (0.5) | ||
Maintain natural hydrology (0.44): | NA | NA |
Maintain natural flooding regime (0.50) | Percent of time marsh surface is flooded relative to ideal reference system | Absolute deviation from reference in percentage points |
Maintain natural salinity (0.50) | Surface-water salinity relative to ideal reference system | Absolute deviation from reference in parts per thousand |
Maintain the extent of the marsh platform (0.44) | Change in marsh surface elevation relative to sea-level rise | 0=change in elevation is less than amount of sea-level rise; 1=change in elevation greater than or equal to amount of sea-level rise |
Minimize use of herbicides (0.12) | Rate of application | Pints |
Fundamental objectives of salt marsh management decisions.
Relative abundance based on local knowledge.
The hierarchy of objectives for salt marsh management (
In February 2018, FWS regional biologists, biologists and managers from four northeastern NWR administrative units, and USGS research scientists (
Table 2. Participants in workshop convened at the Eastern Shore of Virginia National Wildlife Refuge to apply a regional framework for optimizing salt marsh management decisions to three national wildlife refuge administrative units in February 2018
[FWS, U.S. Fish and Wildlife Service; NWR, National Wildlife Refuge; USGS, U.S. Geological Survey]
Affiliation | Participant |
FWS NWR specialists | |
---|---|
Eastern Shore of Virginia and Fisherman Island NWRs | Pam Denmon |
Eastern Shore of Virginia and Fisherman Island NWRs | Robert Leffel |
Long Island NWR Complex | Monica Williams |
Plum Tree Island NWR | William Crouch |
Plum Tree Island NWR | Lauren Cruz |
FWS regional expert | |
Rachel Carson NWR | Susan Adamowicz |
Research scientists | |
USGS Eastern Ecological Science Center | James Lyons |
USGS Eastern Ecological Science Center | Hilary Neckles |
Participants identified a range of possible management actions for achieving objectives within each marsh management unit at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges and estimated the total cost of implementation over a 5-year period; the specific years of implementation were not identified in this prototype. Potential actions to enhance salt marsh integrity ranged from targeted efforts that restore hydrologic connections, increase surface-water drainage, or control predators, deer, or spread of
Table 3. Possible management actions for achieving objectives within marsh management units at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia, estimated costs over 5 years, and predicted outcomes expressed relative to performance metrics
[Potential management actions, costs, and predicted outcomes developed by workshop participants using expert judgement. Predicted consequences of management actions aided by influence diagrams (
Management action | Estimated cost over 5 years (dollars) | Performance metrics | |||||||||
Native vegetation (% cover) | Nekton | Tidal marsh obligate birds (summed number per point) | American black ducks use1 | Spider density (number per square meter) | Hydrology | Marsh surface elevation change relative to sea-level rise3 | Herbicide application (pints/year) | ||||
Density (number of animals per square meter) | Species richness (number) | Duration of surface flooding2 (%) | Surface-water salinity2 (ppt) | ||||||||
Bull Marsh | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
A. No action | 0 | 98 | 76 | 7 | 3.5 | Medium | 30 | 10.6 | 6 | 1 | 0 |
B. Remove road and control any resulting invasive species | 250,000 | 100 | 91 | 10 | 5.5 | Medium | 30 | 0 | 6 | 1 | 6 |
C. Breach road in four places and control any resulting invasive species | 20,000 | 100 | 84 | 9 | 4.5 | Medium | 30 | 5 | 6 | 1 | 3 |
D. Lower road elevation | 50,000 | 100 | 80 | 8 | 4.5 | Medium | 30 | 7 | 6 | 1 | 0 |
E. Remove |
25,000 | 100 | 76 | 7 | 3.6 | Medium | 30 | 10.6 | 6 | 1 | 60 |
F. Facilitate marsh migration by leveling berms and ditches west of unit and controlling invasive plants | 15,000 | 100 | 76 | 7 | 3.5 | Medium | 30 | 9 | 6 | 1 | 12 |
G. Create more pools and runnels | 60,000 | 100 | 100 | 8 | 3.5 | Medium | 15 | 10.6 | 6 | 1 | 0 |
H. Trap mammalian predators, including |
50,000 | 100 | 76 | 7 | 4 | Medium | 30 | 10.6 | 6 | 1 | 0 |
I. Reduce disturbance through refuge permits | 7,800 | 100 | 76 | 7 | 3.7 | Medium | 30 | 10.6 | 6 | 1 | 0 |
J. Acquire land and control |
17,400 | 98 | 108 | 9 | 3.6 | Medium | 30 | 9 | 6 | 1 | 30 |
K. Install three culverts in road and control invasive plants | 20,000 | 100 | 82 | 9 | 4.5 | Medium | 30 | 4 | 6 | 1 | 3 |
L. B+G | 310,000 | 100 | 130 | 11 | 5.7 | Medium | 15 | 10.6 | 6 | 1 | 0 |
Skidmore S | |||||||||||
A. No action | 0 | 99 | 12 | 6 | 0.69 | Medium | 15 | 22.8 | 2 | 1 | 0 |
B. Create islands for marsh bird nesting using dredge spoils | 30,000 | 98 | 12 | 6 | 1 | Medium | 15 | 18 | 2 | 1 | 0 |
C. Apply broad-scale sediment to marsh platform to lower flood duration | 90,000 | 99 | 11 | 6 | 1 | Medium | 30 | 0 | 2 | 1 | 0 |
D. Remove |
7,500 | 100 | 12 | 6 | 0.7 | Medium | 15 | 22.8 | 2 | 1 | 18 |
E. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 50,000 | 100 | 12 | 6 | 1.2 | Medium | 15 | 22.8 | 2 | 1 | 0 |
F. B+E | 80,000 | 99 | 12 | 6 | 2 | Medium | 15 | 18 | 2 | 1 | 0 |
G. B+C+E | 170,000 | 99 | 11 | 6 | 3 | Medium | 30 | 0 | 2 | 1 | 0 |
ESV Marsh | |||||||||||
A. No action | 0 | 97 | 87 | 8 | 5.7 | Medium | 15 | 10 | 3 | 1 | 0 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 50,000 | 98 | 87 | 8 | 6.1 | Medium | 15 | 10 | 3 | 1 | 0 |
C. Reduce deer population | 10,000 | 98 | 87 | 8 | 6.1 | Medium | 15 | 10 | 3 | 1 | 0 |
D. Remove Wise Point Road and control invasive plants | 100,000 | 98 | 87 | 8 | 5.9 | Medium | 15 | 10 | 3 | 1 | 24 |
E. Remove water control structure on Wise Point Road and control invasive plants | 10,000 | 98 | 87 | 8 | 5.9 | Medium | 15 | 10 | 3 | 1 | 6 |
F. Remove |
50,000 | 100 | 87 | 8 | 6 | Medium | 30 | 10 | 3 | 1 | 18 |
G. Reduce disturbance through refuge permits | 7,800 | 98 | 87 | 8 | 6 | Medium | 15 | 10 | 3 | 1 | 0 |
H. B+C | 60,000 | 98 | 87 | 8 | 6.6 | Medium | 15 | 10 | 3 | 1 | 0 |
I. Dig runnels by hand | 9,000 | 100 | 157 | 15 | 8.6 | Medium | 30 | 7 | 3 | 1 | 0 |
J. Dig runnels using machine | 26,000 | 100 | 124 | 13 | 8.9 | Medium | 30 | 0 | 3 | 1 | 0 |
Raccoon | |||||||||||
A. No action | 0 | 99 | 88 | 11 | 2 | Medium | 15 | 16.1 | 1 | 0 | 0 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 5,000 | 100 | 88 | 11 | 2.8 | Medium | 15 | 16.1 | 1 | 0 | 0 |
C. Remove |
10,000 | 100 | 88 | 11 | 2.8 | Medium | 15 | 16.1 | 1 | 0 | 24 |
D. Install living shoreline | 2,500,000 | 100 | 120 | 11 | 2.8 | Medium | 30 | 16.1 | 1 | 1 | 0 |
Fisherman Island East Marsh | |||||||||||
A. No action | 0 | 98 | 51 | 9 | 3.2 | Medium | 30 | 2.6 | 1 | 1 | 0 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 50,000 | 99 | 51 | 9 | 4 | Medium | 30 | 2.6 | 1 | 1 | 0 |
C. Reduce deer population | 10,000 | 99 | 51 | 9 | 4.1 | Medium | 30 | 2.6 | 1 | 1 | 0 |
D. Remove |
150,000 | 100 | 51 | 9 | 3.6 | Medium | 30 | 2.6 | 1 | 1 | 360 |
E. Reduce disturbance through refuge permits | 7,800 | 100 | 51 | 9 | 3.6 | Medium | 30 | 2.6 | 1 | 1 | 0 |
Fisherman Island West Marsh | |||||||||||
A. No action | 0 | 99 | 172 | 16 | 7.5 | Medium | 15 | 20 | 3 | 1 | 0 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 50,000 | 100 | 172 | 15 | 8.5 | Medium | 15 | 20 | 3 | 1 | 0 |
C. Reduce deer population | 10,000 | 100 | 172 | 15 | 8.9 | Medium | 15 | 20 | 3 | 1 | 0 |
D. Install six road culverts or bridges and control invasive plants | 6,000,000 | 100 | 110 | 11 | 10 | Medium | 30 | 6 | 3 | 1 | 60 |
E. Remove |
25,000 | 100 | 172 | 15 | 8.5 | Medium | 15 | 20 | 3 | 1 | 0 |
F. Install living shoreline to protect dunes and prevent breaches into marsh | 5,000,000 | 100 | 172 | 15 | 8.4 | Medium | 15 | 20 | 3 | 1 | 0 |
G. Remove invasive plants in upland adjacent to marsh | 10,000 | 100 | 172 | 15 | 8.4 | Medium | 15 | 20 | 3 | 1 | 0 |
H. Reduce disturbance through refuge permits | 7,800 | 100 | 172 | 15 | 8.5 | Medium | 15 | 20 | 3 | 1 | 0 |
I. Dig runnels by hand | 9,000 | 100 | 157 | 15 | 8.6 | Medium | 30 | 10 | 3 | 1 | 0 |
J. Dig runnels using machine | 26,000 | 100 | 124 | 13 | 8.9 | Medium | 30 | 8 | 3 | 1 | 0 |
K. D+J | 6,026,000 | 100 | 87 | 9 | 9.3 | Medium | 30 | 0 | 3 | 1 | 60 |
Relative abundance for refuges during wintering waterfowl season.
Measures absolute deviation from reference point representing ideal condition.
Measures change relative to sea-level rise: 0, lower than sea-level rise; 1, above sea-level rise.
Following the workshop, the potential management benefit of each salt marsh integrity performance metric was calculated by converting salt marsh integrity metric scores (
Table 4. Normalized predicted outcomes and estimated total management benefits of possible management actions within six marsh management units at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia
[Numeric table entries are weighted utilities, which were calculated as raw utilities multiplied by objective weights. Unitless raw utilities were derived from metric scores (
Management action | Performance metrics | Total management benefit | |||||||||
Native vegetation | Nekton | Tidal marsh obligate birds | American black ducks | Spider density | Hydrology | Marsh surface elevation change | Herbicide application | ||||
Density | Species richness | Duration of surface flooding | Surface-water salinity | ||||||||
Bull Marsh | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|
A. No action | 0.119 | 0.028 | 0.020 | 0.035 | 0.075 | 0.090 | 0.108 | 0.110 | 0.220 | 0.060 | 0.865 |
B. Remove road and control any resulting invasive species | 0.120 | 0.032 | 0.028 | 0.055 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.059 | 0.899 |
C. Breach road in four places and control any resulting invasive species | 0.120 | 0.030 | 0.025 | 0.045 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.885 |
D. Lower road elevation | 0.120 | 0.029 | 0.023 | 0.045 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.882 |
E. Remove |
0.120 | 0.028 | 0.020 | 0.036 | 0.075 | 0.090 | 0.108 | 0.110 | 0.220 | 0.050 | 0.857 |
F. Facilitate marsh migration by leveling berms and ditches west of unit and controlling invasive plants | 0.120 | 0.028 | 0.020 | 0.035 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.058 | 0.866 |
G. Create more pools and runnels | 0.120 | 0.034 | 0.023 | 0.035 | 0.075 | 0.045 | 0.108 | 0.110 | 0.220 | 0.060 | 0.829 |
H. Trap mammalian predators, including |
0.120 | 0.028 | 0.020 | 0.040 | 0.075 | 0.090 | 0.108 | 0.110 | 0.220 | 0.060 | 0.871 |
I. Reduce disturbance through refuge permits | 0.120 | 0.028 | 0.020 | 0.037 | 0.075 | 0.090 | 0.108 | 0.110 | 0.220 | 0.060 | 0.868 |
J. Acquire land and control |
0.119 | 0.035 | 0.025 | 0.036 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.055 | 0.876 |
K. Install three culverts in road and control invasive plants | 0.120 | 0.030 | 0.025 | 0.045 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.884 |
L. B+G | 0.120 | 0.039 | 0.031 | 0.057 | 0.075 | 0.045 | 0.108 | 0.110 | 0.220 | 0.060 | 0.865 |
Skidmore S | |||||||||||
A. No action | 0.120 | 0.006 | 0.017 | 0.007 | 0.075 | 0.045 | 0.063 | 0.110 | 0.220 | 0.060 | 0.722 |
B. Create islands for marsh bird nesting using dredge spoils | 0.119 | 0.006 | 0.017 | 0.010 | 0.075 | 0.045 | 0.081 | 0.110 | 0.220 | 0.060 | 0.743 |
C. Apply broad-scale sediment to marsh platform to lower flood duration | 0.120 | 0.005 | 0.017 | 0.010 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.817 |
D. Remove |
0.120 | 0.006 | 0.017 | 0.007 | 0.075 | 0.045 | 0.063 | 0.110 | 0.220 | 0.057 | 0.720 |
E. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 0.120 | 0.006 | 0.017 | 0.012 | 0.075 | 0.045 | 0.063 | 0.110 | 0.220 | 0.060 | 0.728 |
F. B+E | 0.120 | 0.006 | 0.017 | 0.020 | 0.075 | 0.045 | 0.081 | 0.110 | 0.220 | 0.060 | 0.753 |
G. B+C+E | 0.120 | 0.005 | 0.017 | 0.030 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.837 |
ESV Marsh | |||||||||||
A. No action | 0.119 | 0.031 | 0.023 | 0.057 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.060 | 0.849 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 0.119 | 0.031 | 0.023 | 0.061 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.060 | 0.854 |
C. Reduce deer population | 0.119 | 0.031 | 0.023 | 0.061 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.060 | 0.854 |
D. Remove Wise Point Road and control invasive plants | 0.119 | 0.031 | 0.023 | 0.059 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.056 | 0.848 |
E. Remove water control structure on Wise Point Road and control invasive plants | 0.119 | 0.031 | 0.023 | 0.059 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.059 | 0.851 |
F. Remove |
0.120 | 0.031 | 0.023 | 0.060 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.057 | 0.895 |
G. Reduce disturbance through refuge permits | 0.119 | 0.031 | 0.023 | 0.060 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.060 | 0.853 |
H. B+C | 0.119 | 0.031 | 0.023 | 0.066 | 0.075 | 0.045 | 0.110 | 0.110 | 0.220 | 0.060 | 0.859 |
I. Dig runnels by hand | 0.120 | 0.043 | 0.042 | 0.086 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.956 |
J. Dig runnels using machine | 0.120 | 0.038 | 0.037 | 0.089 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.949 |
Raccoon | |||||||||||
A. No action | 0.120 | 0.031 | 0.031 | 0.020 | 0.075 | 0.045 | 0.088 | 0.110 | 0.000 | 0.060 | 0.579 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 0.120 | 0.031 | 0.031 | 0.028 | 0.075 | 0.045 | 0.088 | 0.110 | 0.000 | 0.060 | 0.588 |
C. Remove |
0.120 | 0.031 | 0.031 | 0.028 | 0.075 | 0.045 | 0.088 | 0.110 | 0.000 | 0.056 | 0.584 |
D. Install living shoreline | 0.120 | 0.038 | 0.031 | 0.028 | 0.075 | 0.090 | 0.088 | 0.110 | 0.220 | 0.060 | 0.859 |
Fisherman Island East Marsh | |||||||||||
A. No action | 0.119 | 0.021 | 0.025 | 0.032 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.862 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 0.120 | 0.021 | 0.025 | 0.040 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.871 |
C. Reduce deer population | 0.120 | 0.021 | 0.025 | 0.041 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.872 |
D. Remove |
0.120 | 0.021 | 0.025 | 0.036 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.000 | 0.807 |
E. Reduce disturbance through refuge permits | 0.120 | 0.021 | 0.025 | 0.036 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.867 |
Fisherman Island West Marsh | |||||||||||
A. No action | 0.120 | 0.045 | 0.045 | 0.075 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.868 |
B. Trap mammalian predators, including raccoons, to increase nesting success of tidal marsh birds | 0.120 | 0.045 | 0.042 | 0.085 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.876 |
C. Reduce deer population | 0.120 | 0.045 | 0.042 | 0.089 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.880 |
D. Install six road culverts or bridges and control invasive plants | 0.120 | 0.036 | 0.031 | 0.100 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.050 | 0.942 |
E. Remove |
0.120 | 0.045 | 0.042 | 0.085 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.876 |
F. Install living shoreline to protect dunes and prevent breaches into marsh | 0.120 | 0.045 | 0.042 | 0.084 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.875 |
G. Remove invasive plants in upland adjacent to marsh | 0.120 | 0.045 | 0.042 | 0.084 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.875 |
H. Reduce disturbance through refuge permits | 0.120 | 0.045 | 0.042 | 0.085 | 0.075 | 0.045 | 0.073 | 0.110 | 0.220 | 0.060 | 0.876 |
I. Dig runnels by hand | 0.120 | 0.043 | 0.042 | 0.086 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.956 |
J. Dig runnels using machine | 0.120 | 0.038 | 0.037 | 0.089 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.060 | 0.949 |
K. D+J | 0.120 | 0.031 | 0.025 | 0.093 | 0.075 | 0.090 | 0.110 | 0.110 | 0.220 | 0.050 | 0.924 |
Potential management actions identified to improve marsh integrity at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges included trapping mammalian predators to increase the nesting success of tidal marsh birds; controlling
Constrained optimization was applied to identify the optimal management portfolios over 5 years for a range of total costs to the refuges’ administration. As total cost increased from $0 (no action in any unit) to approximately $3 million, the total management benefit at the refuge scale increased from 4.746 to 5.379 (a 13-percent increase;
Table 5. Actions included in various management portfolios to maximize the total management benefits subject to increasing cost constraints at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia
[Letter designations for actions refer to specific actions and are listed in
Portfolio | Marsh management unit | Total cost (dollars) | Total management benefit | |||||
Bull Marsh | Skidmore S | ESV Marsh | Raccoon | Fisherman Island East Marsh | Fisherman Island West Marsh | |||
1 | A | A | A | A | A | A | 0 | 4.746 |
2 | A | A | I | B | A | I | 23,000 | 4.950 |
3 | C | A | I | A | C | I | 48,000 | 4.971 |
4 | C | B | I | B | C | I | 83,000 | 4.999 |
5 | C | C | I | B | C | I | 143,000 | 5.074 |
6 | C | G | I | B | C | I | 223,000 | 5.094 |
7 | B | G | I | B | C | I | 453,000 | 5.108 |
8 | B | G | I | D | C | I | 2,948,000 | 5.379 |
The potential management actions selected within the set of portfolios that yielded the greatest total management benefit per unit cost (
Graph showing predicted total management benefit of various portfolios, expressed as weighted utilities, relative to total cost at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia. Each portfolio (dot with number) represents a combination of six management actions, one per marsh management unit, as identified in
Figure 3. Graph showing predicted total management benefit of various portfolios, expressed as weighted utilities, relative to total cost at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia
Examination of the refuge-scale metric responses to actions included in portfolio 5, which is the turning point in the cost-benefit plot (
Bar chart showing predicted management benefit at the refuge scale for individual performance metrics, expressed as weighted utilities, resulting from implementation of the management actions included in portfolio 5, in comparison to the management benefit from the baseline “no-action” portfolio, at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia. The actions included in each portfolio are listed in
Figure 4. Bar chart of predicted management benefit of portfolio 5 in comparison to the management benefit from the baseline “no-action” portfolio at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges in Virginia
A regional structured decision-making framework for salt marshes on NWRs in the northeastern United States was applied by the USGS, in cooperation with the FWS, to develop a tool for optimizing management decisions at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges. Use of the existing regional framework and a rapid-prototyping approach permitted NWR biologists and managers, FWS regional authorities, and research scientists to construct a decision model for the refuges within the confines of a 1.5-day workshop. This preliminary prototype provides a local framework for decision making while revealing information needs for future iterations. Insights from this process may also be useful to inform future habitat management planning at the refuges.
The suite of potential management actions and predicted outcomes included in this prototype (
Results of constrained optimizations (
Second, the habitat management plan for the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges identifies seaside sparrows as a priority resource of concern in salt marsh habitat (
Third, although loss of marsh area through shoreline erosion is a concern in the Raccoon and Fisherman Island West Marsh management units, reducing wave action through construction of living shorelines (plants or other natural elements for shoreline stabilization) was excluded from all but the costliest optimal portfolio. Living shorelines may be cost prohibitive at these refuges. Additionally, deconstructing the objective of maintaining the extent of the marsh platform into subordinate objectives and performance metrics related to both horizontal and vertical gains and losses of marsh substrate may help focus decision making on erosion of marsh edges as a driver of marsh area.
Finally, the constrained optimizations analyzed in this report were based on estimations of management costs. As salt marsh management is undertaken around the northeast region, a detailed list of actual expenses can be compiled, including staff time for project planning as well as materials, equipment, contracts, and staff time for implementation. For example,
The prototype model for the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges provides a useful tool for decision making that can be updated in the future with new data and information. The spatial and temporal variability inherent in parameter estimates were not quantified during rapid prototyping. Previously, preliminary sensitivity analysis revealed little effect of incorporating ecological variation in abundance of marsh-obligate breeding birds on the optimal solutions for Prime Hook National Wildlife Refuge (
The influence diagrams (following the style of prototype diagrams in
Influence diagram used to estimate percent cover of native vegetation in response to implementing certain management actions.
Influence diagram used to estimate nekton density and species richness in response to implementing certain management actions.
Influence diagram used to estimate abundance of tidal marsh obligate breeding birds in response to implementing certain management actions.
Influence diagram used to estimate abundance of American black ducks in winter, as indicator species for nonbreeding wetland birds, in response to implementing certain management actions.
Influence diagram used to estimate density of spiders, as indicator of trophic health, in response to implementing certain management actions.
Influence diagram used to estimate percent of time marsh surface is flooded and salinity of marsh surface water in response to implementing certain management actions.
Influence diagram used to estimate change in elevation of the marsh surface relative to sea-level rise in response to implementing certain management actions.
Influence diagram used to estimate volume of herbicide that could be applied if a decision was made to use chemical control for removing unwanted vegetation.
Utilities [
Native vegetation at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Native nekton density at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Native nekton species richness at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Tidal marsh obligate birds at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
American black ducks at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Marsh spiders at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Duration of surface flooding at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Salinity of surface water at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Change in marsh surface elevation relative to sea-level rise at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Application of herbicides at the Eastern Shore of Virginia and Fisherman Island National Wildlife Refuges, Virginia.
Director, Eastern Ecological Science Center
U.S. Geological Survey
11649 Leetown Road
Kearneysville, WV 25430
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