Puget Sound Ecosystem Portfolio Model

The Puget Sound Ecosystem Portfolio Model:
     A Regional Analysis to Support Land Use and Restoration Planning

Puget Sound project area
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For more information contact:
Bill Labiosa

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Photo: Hugh Shipman
image of barrier beach

Barrier beaches are broad, flat beaches where sediment deposits.

image of Bluff-backed beach

Bluff-backed beaches form at the base of steep, eroding bluffs.

image of seawall

Seawall (armoring) on Whidbey Island

The Puget Sound nearshore encompasses 4000 kilometers of shoreline that include bluffs, beaches, mudflats, kelp and eelgrass beds, salt marshes, gravel spits, and estuaries. This highly productive zone supports a wide variety of valuable ecosystem services (the services provided to humans by nature), like shellfishing, fin fishing, and shoreline recreation, as well as the many cultural activities that rely on a healthy ecosystem, like subsistence fishing by tribes. The nearshore provides ecosystem function by supplying the substrate for eelgrass and kelp and spawning habitat for forage fish, and supporting shellfish production and rearing and migration for juvenile salmon.

Thousands of streams and rivers drain a land area of about 35,500 square kilometers into Puget Sound, designated by the U.S. EPA as an Estuary of National Significance. This region is experiencing significant population growth and development pressures. In 2005 the Puget Sound Basin had approximately 4.4 million people, a 25% increase from 1991, and the population is expected to grow to 4.7 to 6.1 million residents by 2025.

The USGS Puget Sound Ecosystem Portfolio Model (PSEPM) is a decision support tool that uses scenarios to evaluate where, when and to what extent future population growth, urban growth and shoreline development may threaten the nearshore environment by 2060 (Byrd et al., 2011). The tool focuses on threats to barrier and bluff-backed beaches, which represent 50 percent of Puget Sound shorelines by length. A suite of sub-models identify multiple connections between land use and the nearshore’s capacity to support valued ecosystem components (VECs) and ecosystem services (Figure 1, Table 1). The PSEPM builds on approaches used in the South Florida EPM (http://lcat.usgs.gov/sflorida/sflorida.html) (Labiosa et al., 2009 -- http://pubs.usgs.gov/sir/2009/5181/). .

Figure 1. The Land-Water-Human Connection: The PSEPM models potential future changes to metrics of nearshore condition through the use of ENVISION growth model output data.

Figure 1

VECs are key elements of the Puget Sound Nearshore Ecosystem Restoration Project (PSNERP) (http://www.pugetsoundnearshore.org/) conceptual framework for nearshore restoration, and were selected to communicate the value of Puget Sound nearshore restoration to managers and the public. Ecosystem services are the benefits people obtain from ecosystems including provisioning services such as food and water, regulating services such as flood and disease control, cultural services such as spiritual, recreational, and cultural benefits, and supporting services such as nutrient cycling.

PSEPM model outputs include maps that highlight shoreline sections where nearshore resources may be at greater risk from upland changes. Using these results, planners may focus threat reduction strategies to targeted areas in order to meet Puget Sound-wide conservation and restoration goals.

Scenario Analysis

The PSEPM evaluates three alternative futures of the nearshore by analyzing three growth scenarios developed by PSNERP as part of their Future Risk Assessment Project (FRAP). These decadal scenarios are modeled out to 2060 by the GIS-based ENVISION model( http://envision.bioe.orst.edu/StudyAreas/PugetSound/) developed at Oregon State University by Professor John Bolte. The three scenarios include

  1. Status Quo – continuation of current trends
  2. Managed Growth – adoption of an aggressive set of land use management policies and concentrating growth within urban growth areas
  3. Unconstrained Growth – relaxation of land use restrictions and more growth occurring outside urban growth areas.

A scenario is not a prediction. Instead it represents a plausible account of the future given logical assumptions about how conditions change over space and time. Instead of trying to predict a single outcome, planners use scenarios to consider a variety of possible futures that include many important uncertainties. Scenario planning is most useful in cases such as long term planning for the Puget Sound region, where uncertainty is high and the ability to control the system is low.

Model Results

Shellfish Pollution Model - estimates fecal coliform bacteria concentrations in commercial shellfish growing areas based on scenarios of land cover change in drainages. Click here to compare model results across scenarios and here to see differences between scenarios.

Beach Armoring Index – scores beaches based on the potential for geomorphological and ecological changes due to scenarios of cumulative on-site and updrift armoring. Click here to compare model results across scenarios and here to see differences between scenarios.

Recreation Visits Model – models changes in State Park beach visitation based on scenarios of population distributions in Puget Sound. Click here to compare model results across scenarios and here to see differences between scenarios.

As illustrated in Figure 1, these model results influence potential changes to Nearshore Resources, including ecosystem services and valued ecosystem components. By intersecting models with existing data, PSEPM assesses potential future changes to forage fish spawning habitat, recreational shellfish harvesting, and recreational beach quality. Click here to see potential changes to these resources across scenarios and time.


  1. Interpretation of model results is limited by model uncertainty and data availability, but they allow for relative comparisons of nearshore ecosystem change among sites and regions across decades.

  2. Evaluation of multiple environmental criteria targets a short list of sites for further study and higher level conservation and restoration planning.

  3. Model results highlight resource-rich areas that may be potentially impacted by multiple stressors. For example, increased shoreline armoring combined with increased impervious surfaces and population growth in the South-Central subbasin may create conditions where a shoreline exhibits reduced water quality and sediment supply, yet recreational visits are higher. These changes could reduce the shoreline’s capacity to support shellfish harvesting, beach going, or possibly forage fish spawning habitat.

  4. Iterative adjustment of scenarios and models is needed to better discern differences among alternative futures.

  5. The Washington Climate Change Impacts Assessment (2009) (http://cses.washington.edu/cig/res/ia/waccia.shtml) identifies potential climate change impacts to Puget Sound beaches and bluffs and shellfish aquaculture. The PSEPM lays the foundation for future work on integrated climate change and land use change scenario development to better evaluate potential threats to these resources.

Table 1. PSEPM models and their connection to Puget Sound Valued Ecosystem Components (VECs) and Ecosystem Services. These models measure changes to nearshore metrics selected based on multiple workshops and meetings with stakeholders, managers and experts in the Puget Sound region.

EPM Model

Model Description

Ecosystem Service
(Millennium Ecosystem Assessment 2005)

Puget Sound VEC: Native Shellfish

Shellfish pollution model

Statistical model based on land cover and Washington Dept. of Health water quality data in commercial shellfish growing areas

Provisioning services: food

Cultural services: ethical values

Regulating services: water purification

Recreational shellfish harvesting

Shellfish pollution model results intersected with Washington Dept. of Fish and Wildlife annual harvest data at recreational shellfish beaches

Provisioning services: food

Cultural services: recreation and ecotourism

Puget Sound VEC: Beaches and bluffs

Beach armoring index

Index based on PSNERP change analysis geodatabase and fetch data

Cultural services: existence values, recreation and ecotourism

Regulating services: erosion regulation

Recreation visits model

Statistical model based on State Park visitation data

Cultural services: recreation and ecotourism

Recreational beach quality

Beach armoring index intersected with Recreation visits model results and beach access type

Cultural services: existence values, recreation and ecotourism

Regulating services: erosion regulation

Puget Sound VEC: Forage fish

Forage fish spawning potential

Washington Dept. of Fish and Wildlife (WDFW) 2009 data and WDFW and USGS modeling collaboration, intersected with Beach armoring index

Provisioning services: food

Cultural services: existence values

Puget Sound VEC: Eelgrass

Eelgrass habitat suitability*

Based on Controlling Factors Model (Borde et al. 2009, Diefenderfer et al. 2009)

Provisioning services: food

Regulating services: climate regulation, erosion regulation

Cultural services: existence values

Supporting services: primary production

Nearshore nutrient loading*



Regulating services: water purification

Cultural services: recreation and tourism

Supporting services: nutrient cycling

*Planned for phase 2 of PSEPM.




Borde, A, C Judd, N Sather and R Thom. 2009. East Kitsap County Nearshore Habitat Assessment and Restoration Prioritization Framework. PNWD-4052, Battelle Pacific Northwest Division, Sequim, WA.

Byrd, K.B, Kreitler, J.R, and Labiosa, W.B, 2011, Tools and methods for evaluating and refining alternative futures for coastal ecosystem management—the Puget Sound Ecosystem Portfolio Model: U.S. Geological Survey Open-File Report 2011–1279, 47 p., available at http://pubs.usgs.gov/of/2011/1279/.

Carpenter, S.R. et al. (eds). 2005. Ecosystems and Human Well-being: Scenarios, Volume 2. Appendix D, Glossary. Findings of the Scenarios Working Group, Millennium Ecosystem Assessment. Island Press, Washington. http://www.maweb.org/en/Scenarios.aspx#download

Diefenderfer H, K Sobocinski, R Thom, C May, A Borde, S Southard, J Vavrinec, III, and N Sather. 2009. Multiscale Analysis of Restoration Priorities for Marine Shoreline Planning. Environmental Management 44(4):712-731. doi:10.1007/s00267-009-9298-4.

Labiosa, William B., Bernknopf, Richard, Hearn, Paul, Hogan, Dianna, Strong, David, Pearlstine, Leonard, Mathie, Amy M., Wein, Anne M., Gillen, Kevin, and Wachter, Susan, 2009. The South Florida Ecosystem Portfolio Model; a map-based multicriteria ecological, economic, and community land-use planning tool: U.S. Geological Survey Scientific Investigations Report 2009-5181, 41 p.

Peterson, G.D., G.S. Cumming, and S.R. Carpenter. 2003. Scenario planning: a tool for conservation in an uncertain world. Conservation Biology 17(2):358-366.

Schlenger, P., A. MacLennan, E. Iverson, K. Fresh, C. Tanner, B. Lyons, S. Todd, R. Carman, D. Myers, S. Campbell, and A. Wick. In Review. Strategic Needs Assessment Report. Prepared for the Puget Sound Nearshore Ecosystem Restoration Project.

Washington State Office of Financial Management. 2005. Washington State Data Book. OFM Forecasting Division, Olympia, WA. http://www.ofm.wa.gov/pop/default.asp

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