&EPA
United States
Environmental Protection
Agency
EPA/601/S-14/001 September 2014 www.epa.gov/ord
Structure and Vulnerability of
Pacific Northwest Tidal Wetlands
A Summary of Wetland Climate Change
Research by the Western Ecology
Division, U.S. EPA1
Office of
Research and Development
National Health and
Environmental Effects
Research Laboratory
Western Ecology Division
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S-14/001
September, 2014
Structure and Vulnerability of Pacific Northwest Tidal Wetlands -
A Summary of Wetland Climate Change Research
by the Western Ecology Division, U.S. EPA
Christina L. Folger1, Henry Lee II1, Christopher N. Janousek1'2 and Deborah A. Reusser3
1. Western Ecology Division, Office of Research and Development, U.S. Environmental
Protection Agency. 2111 SE Marine Science Dr., Newport, Oregon 97365
2. Present Affiliation: Department of Fisheries and Wildlife, Oregon State University, Corvallis,
Oregon
3. Western Fisheries Research Center, U.S. Geological Survey, Newport,
Oregon, 97365
National Health and Environmental Effects Research Laboratory
Office of Research and Development
U.S. Environmental Protection Agency
Newport, OR 97365
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Disclaimer:
The information in this document was partially funded by the U.S. Environmental Protection
Agency. This report was subjected to review by the National Health and Environmental Effects
Research Laboratory's Western Ecology Division of the U.S. EPA, and the Western Fisheries
Research Center of U.S. Geological Survey, and is approved for publication. However, approval
does not signify that the contents reflect the views of the U.S. EPA. The use of trade, firm, or
corporation names in this publication is for the information and convenience of the reader; such
use does not constitute official endorsement or approval by the U.S. Department of Interior, the
U.S. Geological Survey, or the U.S. EPA of any product or service to the exclusion of others that
may be suitable.
Acknowledgements;
We would like to thank Drs. Christine Weilhoefer and J.B. Moon for their willingness to review
the document in a very timely manner and for their insightful comments. Christopher Janousek
was funded as an NHEERL post-doctoral fellow with the U.S. EPA. Deborah Reusser was
partially funded through IAG#DW-14-92252201-0 with the U.S. EPA.
Recommend Citation:
Folger, C.L., Lee II, H., Janousek, C.N., and Reusser, D.A. 2014. Structure and Vulnerability of
Pacific Northwest Tidal Wetlands - A Summary of Wetland Climate Change Research by the
Western Ecology Division, U.S. EPA. U.S. EPA, Office of Research and Development,
National Health and Environmental Effects Research Laboratory, Western Ecology
Division. EPA 601/S-14/001.
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Table of Contents
Introduction 4
Section 1: Field Surveys and Manipulative Experiments 10
Section 2: Modeling Potential Effects of Climate Change on Estuaries, Seagrass and Tidal Marshes.. 14
Summary: 18
References: 19
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Introduction:
Tidal wetlands, including both submerged aquatic vegetation (SAV) and emergent marsh, are
key habitats in the Pacific Northwest (PNW) playing valuable roles biologically through
fostering local and regional biodiversity and as nursery habitat for commercial fish and crab
species and through providing critical ecosystem services including protecting coastlines from
storms, sequestering carbon and trapping anthropogenic nitrogen (N) from watershed inputs
(e.g., Philips, 1984; Deegan et al., 2000; Williamson, 2006; Ferraro and Cole, 2007; Spalding et
al., 2014). However, tidal wetlands are considered particularly vulnerable ecosystems due to
their unique location - transitional ecotones positioned between land, ocean and rivers (Wasson
et al., 2013) where they are susceptible to changes in the conditions of the habitats surrounding
them. According to the Oregon Climate Change Report (2010), PNW wetlands are expected to
experience greater rates of long term coastal wetland loss than any other areas of the U.S.,
making research on these ecosystems of particular significance. Furthermore, traditional
paradigms of tidal wetland vegetation structure and environmental determinants developed in
east coast US tidal wetlands do not necessarily hold true for PNW wetlands due to differences in
the frequency of tidal inundation and the unique chemical and physical factors of PNW wetlands
(Weilhoefer et al., 2013). As we report in the literature within, it is also these unique conditions
that make PNW tidal wetlands the most biologically diverse in the U.S.
In an effort to forecast potential effects of changing environmental conditions on PNW tidal
wetlands, the Western Ecology Division (WED) of the U.S. EPA, in collaboration with the U.S.
Geological Survey (USGS) and other partners has undertaken a series of research projects aimed
at broadening our understanding of the biological and physical processes that determine PNW
tidal wetland structure and function. Increasing our understanding of the mechanisms at work
within tidal wetlands, adjacent intertidal areas and associated watersheds will increase our ability
to predict how these habitats will respond to anthropogenic stressors, such as climate change. In
this document, we first briefly summarize some of the major climate change threats to tidal
wetlands and then summarize the recent climate change research conducted by WED, USGS,
and other partners (see Table 1).
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A major consequence of global climate change is sea level rise (SLR). Increased global
temperatures are causing land-ice to melt and ocean water to expand, thereby increasing the
volume of the world's oceans. An increase in relative sea level will change the location of the
land-water interface and therefore may impact the aerial extent and community structure of
marshes, macroalgal beds, and seagrass meadows. Although projections of future SLR vary due
to uncertainty and differences in local factors (Ruggiero et al., 2010, NRC, 2012; Mielbrecht et
al., 2014), sea level rise in the region from northern California to Puget Sound is predicted to
range between -3.5 inches to +22.7 inches (-8.9 to 57.7 cm) by 2030; and -2.1 inches to +48.1
inches (-5.3 to 122.2 cm) by 2050 compared to 2008 (Mielbrecht et al., 2014). Interactions
between spatial and temporal physical processes such as isostatic subsidence or uplift, natural
variability in atmospheric and ocean circulation and local topography all contribute to the rate
and potential impact of SLR along the Oregon coast (Ruggiero et al., 2010).
Historically, wetlands have been able to maintain themselves by "biological and physical
feedbacks that couple the rate of sea level rise to the rate of vertical accretion" (Kirwan &
Megonigal 2013). Models suggest that under a medium SLR scenario tidal marshes
with adequate sediment supply are capable of maintaining their current elevation as they have
in the past through dynamic 'cause and effect' biological loops. For instance higher
temperatures and CC>2 levels are predicted to increase above-ground vegetation growth which, in
turn, will slow tidal velocities and allow more sediment to precipitate from the water column.
Below-ground biomass may also increase in response to environmental changes producing more
in-situ organic plant material and increase elevation through sub-surface soil expansion (Thorn,
1992; Morris et al., 2002; Kirwan et al., 2010; Stralberg et al., 2011; Nelson & Zavaleta,
2012; Thorne et al., 2012; Kirwan & Megonigal, 2013). In areas where little sediment is
available for accretion, erosion of the seaward marsh edge is expected resulting in deterioration
of soil structure and vegetation 'drowning'. Whether tidal wetlands and seagrass beds can
sustain their current geographic extent and condition in the face of today's unprecedented
environmental pressures will depend mostly on the degree of human activity surrounding
individual wetlands (e.g. water diversion, natural gas extraction and eutrophication) and the rate
of SLR acceleration.
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Research has documented profound shifts in wetland communities as vegetation follows salinity
optimums as they shift inland concurrent with longer periods of tidal inundation. Evidence of
plant distributional shifts exist in New England where a low-marsh species, cordgrass has rapidly
moved landward at the expense of higher-marsh species (Donnelly & Bertness, 2001), in Florida
where mangroves are retreating landward in response to increased saltwater intrusion (Raabe et
al., 2012); and in the lower elevation marshes of San Francisco Bay, CA as more salt-tolerant
species are increasing in cover and replacing less salt-tolerant species (Watson and Byrne, 2012).
Such changes in wetland community structure will likely have consequences to the ecosystem
overall through changes in productivity, detrital respiration, or change in habitat or food
availability for invertebrates, resident birds and waterfowl. Physiological stress of salinity
appears to be a dominant mechanism determining lateral migration of vegetation shifts (Watson
& Byrne, 2012).
The availability and condition of upland habitat adjacent to the threatened wetland ultimately
determines the degree to which the habitat can migrate. Anthropogenic barriers such as levees,
seawalls and the presence of housing, aquaculture facilities and agriculture limit the natural
response patterns of wetland plants (Galbraith et al., 2002; Feagin et al., 2010). Due to relatively
low human populations in coastal PNW watersheds, wetlands do not have the degree of armoring
and urbanization found in other parts of the U.S., however, land-ward migration of wetland and
intertidal habitats is often constrained by another physical barrier - the natural morphology of
their watersheds. Coastal wetlands in Oregon and Washington are usually relatively small,
starting along the fringes of estuaries and extending to the base of steep watershed hillsides
making them particularly vulnerable to 'coastal squeeze' (Torio and Chmura, 2013), a
phenomenon whereby steep gradients in adjacent upland prevent wetland vegetation from
migrating in response to stressors induced by SLR. Palustrine marshes, located at the upper end
of tidal inundation zones, often terminate in valleys with steep hillsides, and have been shown to
consistently sequester more organic carbon, nitrogen and phosphorous due to lower rates of soil
decomposition relative to saltwater marshes located closer to the mouth of estuaries (Craft, 2007;
Craft, 2009a; Loomis and Craft, 2010). Coastal squeeze may result in loss of habitat area for
low-salinity tidal wetlands resulting in reduced ecosystem function.
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Less predictable factors such as more frequent and intense storms and increased winter
precipitation along the Oregon coast may overwhelm a wetlands natural ability to sustain itself
through vertical or horizontal adaptability and limits our ability to predict the future of coastal
wetlands. Powerful storm water surges flowing through wetland arteries are known to cause
slumping of tidal creek banks and extreme erosion along marsh edges. Conversely increased
precipitation may facilitate the rate of vertical accretion due to a greater supply of organic matter
passing over the marsh surface from highly turbid rivers. In the case of seagrass, intense
scouring from high wave energy can eliminate a large patch of seagrass in one storm event. Data
on the environmental tolerances of wetland species, including elevation and other environmental
determinants presented in this research will allow us to better predict future distributions of PNW
intertidal and marsh vegetation in response to SLR and to assess the variability within these
systems. The magnitude and degree of these complex and interactive environmental changes are
becoming apparent on both large and small scales along coastlines all over the world.
As climate change accelerates, managers and conservation biologists are in need of practical
tools to help them understand the relative impacts of climate change on tidal wetlands. One
frequently used tool is the moderate resolution model, "Sea Level Affecting Marshes Model"
(SLAMM). SLAMM has been used to evaluate 11 sites in Puget Sound, in coastal Washington
and northwestern Oregon (Glick et al., 2007). Model runs have suggested that "52 percent of
brackish marsh will convert to tidal flats, transitional marsh and saltmarsh" assuming a net 0.69
meters (27.3 inches) sea level increase by 2100. SLAMM was used more recently in a
vulnerability assessment of the Coquille Estuary in Oregon which also predicted similar changes
in wetland distributions under various SLR scenarios (Mielbrecht et al., 2014).
The recent climate change wetland research by WED and its partners addresses several of the
issues related to climate impacts on tidal wetlands, and recent products are listed in Table 1.
Products summarized in this document are categorized into two sections: Section 1 summarizes
observational and experimental studies from the field and laboratory that evaluate and improve
the reliability of the classification system of the National Wetlands Inventory (NWI) in the
Pacific Northwest. NWI provides critical data used for SLR modeling. Section 2 focuses on
models and GIS tools developed to explore various climate change scenarios. The products
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summarized here are aimed at providing researchers and managers with the knowledge and tools
available to assess the relative vulnerability of different marsh plants, macroalgae, and seagrass
to climate change as well as providing reference data to be used in mitigation and planning
scenarios. We note that the summaries in this document are reproduced, or adapted from the
published paper's abstract or summary.
Table 1. Recent climate change tidal wetland research publications and tools developed by the
U.S. EPA Western Ecology Division, USGS, and other partners.
Section 1: Field Surveys and Manipulative Experiments
Title
I. Variation in tidal wetland plant diversity and
composition within and among coastal estuaries:
assessing the relative importance of
environmental gradients
II. Patterns of distribution and environmental
correlates of macroalgal assemblages and
sediment chlorophyll a in Oregon tidal wetlands
III. Plant responses to increased inundation and
salt exposure: Potential sea-level rise effects on
tidal marsh productivity
IV. Concordance between marsh habitat classes
and vegetation composition in Oregon estuaries:
Implications for assessing coastal wetland
structure and function
V. Inter-specific variation in salinity effects on
germination in Pacific Northwest tidal wetland
plants
Authors
Janousek, C.
and Folger, C
Janousek, C.
and Folger, C
Janousek, C.
and Mayo, C
Janousek, C.
and Folger, C
Janousek, C.
and Folger, C
Reference / URL
Journal of Vegetation Science 2014 Vol.
25:534-545
Journal of Phycology 2012 Vol. 48:1448-
1457.
Plant Ecology 2013 Vol. 214:917-928
Chapter in 'Report on uncertainty, scaling
and transferability of ecological
production functions'. 2013. Internal
EPA Report for Sustainable and Health
Communities Research Program.
Aquatic Botany 20 13 Vol. 111:104-111
Research
Focus
Marsh
community
structure
Macroalgal
distribution &
environmental
factors
SLR effects on
marsh species
Evaluation of
NWI
classification
Salinity effects
on germination
of marsh plants
Section 2: Models and Predictive Tools
Title Authors
VI. Sea Level Affecting Marshes Model Leg n H Reusser
(SLAMM) - New Functionality for D A praz'ier M R'
Predicting Changes in Distribution of McCoy L M 'Clinton,
Submerged Aquatic Vegetation in Response „ T , _, , T _
to Sea Level Rise. Version 1.0 PJ" wA Clough' IS'
,„ _ ^ ^. , „,. ^ T , , n ff Steele, M.O., Chang,
VII. Potential Climate-Induced Runoff TT ' ' . 6
„. , . • , JTT ^ • ^ • T- H., Reusser, D.A.,
Changes and Associated Uncertainty in Four _ „ . ' '
_ . ° , T ^ ^ „ ^ J Brown, C.A., and Jung,
Pacific Northwest Estuaries T '
t-W.
TI f /TTTIT Research
Reference / URL „
Focus
EPA Report (20 14) : Office of Research and Predict SLR
Development, National Health and impacts on
Environmental Effects Research Laboratory, Zoster a
Western Ecology Division. EPA/600/R- 14/007 marina
Changes in
USGS Open-File Report 2012-1274 fl°W m
http://pubs.usgs.gov/of/20 12/1274/ response to
v v 6 6 changes m
precipitation
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VIII. Tidal Wetlands of the Yaquina and
Alsea River Estuaries, Oregon: Geographic
Information Systems Layer Development
and Recommendations for National
Wetlands Inventory Revisions
IX. WestuRe: U.S. Pacific Coast
Estuary /Watershed Data and R tools
Brophy, L.S. with
contributions from
Reusser, D.A. and
Janousek, C.N.
Frazier, M.R., Reusser,
D.A., Lee II, H.,
McCoy, L.M., Brown,
C. and Nelson, W.
USGS Open-File Report 2012-1038
http://pubs.er.usgs.gov/publication/ofr20 12 1038
EPA Report (2013): EPA/600/R/1 3/067
http://www.epa.gov/wed/pages/models/
WestuRe/WestuRe . htm
Update NWI
layers in two
Oregon
estuaries
Tool to
synthesize
PNW estuary,
watershed,
and climate
information
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Section 1: Field Surveys and Manipulative Experiments:
I. Variation in tidal wetland plant diversity and composition within and among coastal
estuaries: assessing the relative importance of environmental gradients (Janousek and Folger,
2014)
Evaluating coastal wetland responses to climate change requires an understanding of how plant
diversity and composition vary within and among estuaries and habitats and how changes in soil
conditions, inundation times and salinity affect vegetation structure in coastal wetlands. To help
address these questions we surveyed species presence, cover and richness; and environmental
factors (soil salinity, grain size, soil nitrogen and elevation) in tidal wetlands in four Oregon
estuaries (Figure 1).
Our findings suggested that the relative importance of measured environmental gradients on
plant occurrence differed by species. Soil salinity or elevation explained the most variation in the
distribution of the majority of common marsh species. Estuarine hydrology, soil nitrogen and
soil clay content were usually of secondary or minor importance. Overall plant assemblage
composition and species richness varied most strongly with tidal elevation. Local soil salinity
also affected composition, but differences in estuarine hydrology had comparatively less effect
on plant composition and richness. Higher-elevation wetlands supported larger species pools and
higher plot-level richness. Additionally, fresher marshes had larger species pools than more
saline marshes even though plot-level richness was relatively invariant to differences in soil
salinity.
Based on our findings we concluded that elevation and salinity tended to exert more influence on
the vegetation structure of emergent marshes than estuarine hydrology or other edaphic
variables. With relative sea-level rise expected to increase, both flooding intensity and salinity
exposure in future wetlands, global climate change might lead to changes in species
distributions, altered floristic composition and reduced plant species richness in PNW tidal
wetlands.
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II. Patterns of distribution and environmental correlates of macroalgal assemblages and
sediment chlorophyll a in Oregon tidal wetlands (Janousek and Folger, 2012)
Algae have important functional roles in estuarine wetlands along the Pacific coast of the United
States. We quantified differences in macroalgal abundance, composition and diversity, and
sediment chlorophyll a and pheophytin a among three National Wetlands Inventory emergent
marsh classes in four Oregon estuaries spanning a range of riverine to marine dominance (Figure
1). We also assessed the strength of macroalgal-vascular plant associations and the degree to
which environmental variables correlated with algal community metrics across all marsh and
woody wetlands sampled.
The frequency of occurrence of most macroalgal genera, total benthic macroalgal cover,
macroalgal diversity, and sediment chlorophyll a content were several times higher in low
emergent marsh than in high marsh or palustrine tidal marsh. Conversely, pheophytin a:
chlorophyll a ratios were highest in high and palustrine marsh. Attached macroalgae (Fucus and
Vaucherid) were strongly associated with plants common at lower tidal elevations such as
Sarcocorniaperennis and Jaumea carnosa; Ulva (an unattached alga) was not strongly
associated with any common low marsh plants.
Figure 1: Four Oregon estuaries evaluated for
macroalgal abundance, wetland species composition
and diversity.
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In step-wise multiple regression models, intertidal elevation and soil salinity were the most
influential predictors of macroalgal cover and richness and chlorophyll a. Though common taxa
such as Ulva spp. occurred across abroad range of salinities, marshes with oligohaline soils
(salinity < 5 ppt) had the lowest macroalgal diversity and lower sediment chlorophyll a. These
types of baseline data on algal distributions are critical for evaluating the structural and
functional impacts of future changes to coastal estuaries including sea-level rise, altered salinity
dynamics, and habitat modification.
///. Plant responses to increased inundation and salt exposure: interactive effects on tidal
marsh productivity (Janousek and Mayo, 2013)
Sea-level rise may increase submergence and salinity exposure for tidal marsh plants. We tested
the effects of these two potential stressors on seedling growth in a transplant experiment in a
macrotidal estuary in the Pacific Northwest. Seven common marsh species were grown at mean
higher high water (MHHW, a typical mid-marsh elevation), and at 25 and 50 cm below MHHW
in oligohaline, mesohaline, and polyhaline marshes in the Yaquina Estuary on the central Oregon
coast. Increased flooding times reduced shoot and root growth in all species, including those
typically found at middle or lower tidal elevations. It also generally disproportionately reduced
root biomass. For more sensitive species, biomass declined by more than 50 % at only 25 cm
below MHHW at the oligohaline site. Plant growth was also strongly reduced under polyhaline
conditions relative to the less saline sites.
By combining inundation and salinity time-series measurements we estimated a salt exposure
index for each site by elevation treatment. Higher values of the index were associated with
lower root and shoot biomass for all species and a relatively greater loss of below-ground than
above-ground production in most species. Our results suggest that inundation and salinity stress
plants individually and (often) interactively reduce productivity across a suite of common marsh
species. As relative SLR increases the intensity of stress on coastal marsh plants, negative
effects on biomass may occur across a range of species and especially on below-ground
production.
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IV. Concordance between marsh habitat classes and vegetation composition in Oregon
estuaries: Implications for assessing coastal wetland structure and function (Janousek and
Folger, 2013)
Another aspect of our work was evaluating the reliability of a commonly used wetland
classification system, the National Wetlands Inventory (NWI) (Cowardin et al. 1979), for
summarizing structural attributes of coastal habitats. We evaluated NWI habitat classes in
Oregon tidal wetlands with data from field surveys in four regional estuaries (Figure 1).
Assessing the accuracy of the NWI habitat classification system is relevant to coastal modeling
as it is the primary GIS layer for a commonly used sea-level rise model (SLAMM) for projecting
changes to coastal landscapes. Using the established NWI habitat classification system, we
compared environmental conditions and plant assemblages among and within three major
estuarine emergent marsh types (low, high and palustrine) that comprise most of the tidal
wetland area in the Pacific Northwest. We found that physical characteristics (canopy height,
light transmission), sediment properties (total organic carbon, particle size organic matter, and
salinity), elevation and plant composition differed more markedly among NWI marsh habitat
types than between individual estuaries.
In general, we found that the NWI habitat classes were useful for predicting edaphic conditions
and overall plant composition, but because only a few habitat classes are used to map large areas
of tidal marsh in the Pacific Northwest, substantial variation in species richness and vegetation
complexity (driven in part by small-scale topography) can be found within a single marsh class.
A further key finding of the study was the substantial cumulative plant diversity found in Oregon
tidal marshes, including at least 103 species and 12 common assemblages. Identifying the
strengths and weaknesses of the NWI classification schema increases our understanding of the
uncertainties associated with predictions based on NWI and how best to use data from this
readily available mapping effort.
V. Inter-specific variation in salinity effects on germination in the Pacific Northwest tidal
wetlands plants (Janousek and Folger, 2013)
Local climate change effects such as sea-level rise and reduced precipitation in coastal
watersheds are likely to increase salinity in estuarine habitats such as high intertidal marshes and
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swamps (Baldwin et al. 1996). Since salt is often a stressor for vascular plants, we examined
germination success under different salinity conditions to provide insight into species-level
variation in salinity tolerance and inform predictions of species distribution under future climate
scenarios.
In a laboratory study, we evaluated germination sensitivity to salinity in 13 tidal wetland species
found in the Pacific Northwest and then compared germination responses with the distributions
of established plants found along a soil salinity gradient in the field. All species examined,
except Sarcocorniaperennis and Symphyotrichum subspicatum, showed maximum germination
and seedling lengths under fresh to oligohaline (0-5 ppt) conditions. Most species, including
those commonly distributed in more saline wetland soils as adults, had reduced germination at
salinities >10 ppt. Sensitivity to elevated salinity in Triglochin maritima and Hordeum
brachyantherum did not differ markedly between sampled populations. Our results
demonstrated a mismatch between germination sensitivity and adult tolerance for about half of
the species we examined. Therefore, the occurrence of low salinity conditions in time or space
may be necessary for optimal germination rates in these species. Future increases in estuarine
salinity, either in response to sea level rise or reduced coastal precipitation, may alter
germination patterns in tidal wetland plants and thereby shift plant composition.
Section 2: Modeling Potential Effects of Climate Change on
Estuaries, Seagrass and Tidal Marshes:
VI. Sea Level Affecting Marshes Model (SLAMM) - New Functionality for Predicting
Changes in Distribution of Submerged Aquatic Vegetation in Response to Sea Level Rise.
Version 1.0 (Lee et al, 2014)
SLAMM is a two-dimensional model used to predict the effects of sea level rise on marsh habitat
distribution (Craft et al. 2009a)and has been used extensively on both the west coast (e.g., Glick
et al., 2007) and east coast (e.g., Geselbracht et al., 2011) of the U.S. One limitation of
SLAMM, (Version 6.2) is that it lacks the ability to model distribution changes in submerged
aquatic vegetation (SAV) habitat due to sea level rise. This is a major gap since SAV is a critical
estuarine habitat type along the U.S. coast. In PNW estuaries, SAV in the lower intertidal and
shallow subtidal is dominated by the native seagrass, Zostera marina, which provides important
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habitat for juvenile salmon, dungeness crabs, migratory shore birds, and benthic assemblages
(e.g., Philips, 1984; Williamson, 2006; Ferraro and Cole, 2007; Shaughnessy et al., 2012).
Because of its narrow depth range, Z. marina is potentially vulnerable to sea level rise.
Due to its ecological importance, U.S. EPA, USGS, and U.S. Department of Agriculture (USD A)
partnered with Warren Pinnacle Consulting to enhance the SLAMM modeling software. Based
on known distributions of Z. marina in Yaquina Bay Estuary, Oregon, we developed a logistic
regression model to predict SAV distributions from readily available GIS parameters. This
model was added as a new functionality in Version 6.3 of SLAMM. An R script was provided
that describes how the original SAV model for Yaquina Bay was developed. The script also
provides a detailed methodology to develop site-specific model coefficients for other estuaries
when existing SAV GIS data layers are available. Once the site-specific model coefficients are
generated, they can be input into SLAMM to evaluate impacts of sea level rise on SAV
distributions under different sea level rise scenarios. To demonstrate the applicability of the R
tools, we utilized them to develop model coefficients to predict Z. marina distributions in
Willapa Bay, Washington. This new functionality in SLAMM provides a practical first-order
approximation of how the distribution of Z. marina will change in PNW estuaries in response to
sea level rise.
VII. Potential Climate-Induced Runoff Changes and Associated Uncertainty in Four Pacific
Northwest Estuaries (Steele et al., 2012)
To evaluate effects of changing precipitation patterns in the PNW, we estimated changes in
freshwater inputs into four estuaries: Coquille River Estuary, South Slough of Coos Bay, and
Yaquina Bay in Oregon, and Willapa Bay in Washington. All modeled watersheds are located in
rainfall-dominated coastal areas with relatively insignificant base flow inputs, and their areas
vary from 74.3 to 2,747.6 square kilometers. The watersheds also vary in mean elevation,
ranging from 147 meters in the Willapa to 1,179 meters in the Coquille. The U.S. Geological
Survey's Precipitation Runoff Modeling System (PRMS) was used to model watershed
hydrological processes under current and future climatic conditions in these four estuaries.
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We calibrated model parameters using historical climate grid data downscaled to one-sixteenth
of a degree by the Climate Impacts Group, and historical runoff from sub-watersheds or
neighboring watersheds. After calibration, we forced the PRMS models with four North
American Regional Climate Change Assessment Program climate models, using the A2 carbon
emission scenario developed by the Intergovernmental Panel on Climate Change. With these
climate-forcing outputs, we derived the mean change in flow from the period encompassing the
1980s (1971-1995) to the period encompassing the 2050s (2041-2065). Specifically, we
calculated percent change in mean monthly flow rate, coefficient of variation, top 5 percent of
flow, and 7-day low flow. The trends with the most agreement among climate models and
among watersheds were increases in autumn mean monthly flows, especially in October and
November, decreases in summer monthly mean flow, and increases in the top 5 percent of flow.
We also estimated variance in PRMS outputs owing to parameter uncertainty and the selection of
climate model, which showed that PRMS low-flow simulations are more uncertain than medium
or high flow simulations, and that variation among climate models was a larger source of
uncertainty than the hydrological model parameters. These results improve our understanding of
how climate change may affect the saltwater-freshwater balance in PNW estuaries, with
implications for their sensitive ecosystems.
VIII. Tidal Wetlands of the Yaquina andAlsea River Estuaries, Oregon: Geographic
Information Systems Layer Development and Recommendations for National Wetlands
Inventory Revisions (Brophy with Reusser and Janousek, 2013)
To improve SLR modeling results and enhance the accuracy and utility of the NWI for resource
managers, enhanced GIS products were developed for the Yaquina and Alsea drainage basins
(Oregon). These data were generated for two purposes: First, to enhance the NWI by
recommending revised Cowardin classifications for certain NWI wetlands within the study area;
and second, to generate GIS data for the 1999 Yaquina and Alsea River Basins Estuarine
Wetland Site Prioritization study. Two sets of GIS products were generated as a result of this
study: (1) enhanced NWI shapefiles; and (2) shapefiles of prioritization sites. This report also
includes photographs of wetland types and plant species that are common in these estuaries.
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The enhanced NWI shapefiles contain recommended changes to the Cowardin classification
(system, subsystem, class, and/or modifiers) for 286 NWI polygons in the Yaquina Bay Estuary
(1,133 acres) and 83 NWI polygons in the Alsea Bay Estuary (322 acres). These enhanced NWI
shapefiles also identify likely former tidal wetlands that are classified as upland in the current
NWI (64 NWI polygons totaling 441 acres in the Yaquina Estuary; 16 NWI polygons totaling 51
acres in the Alsea Estuary). The former tidal wetlands were identified to assist strategic planning
for tidal wetland restoration. The prioritization site shapefiles contain 49 prioritization sites
totaling 2,177 acres in the Yaquina Estuary, and 39 prioritization sites totaling 1,045 acres in the
Alsea Estuary. The prioritization sites include current and former (for example, diked) tidal
wetlands, and provide landscape units appropriate for basin-scale wetland restoration and
conservation action planning. Several new prioritization sites (not included in the 1999
prioritization) were identified in each estuary, consisting of NWI polygons formerly classified as
nontidal wetland or upland. The GIS products of this project improve the accuracy and utility of
the NWI data, and provide useful tools for estuarine resource management.
IX. WestuRe: U.S. Pacific Coast estuary/watershed data andR tools (Frazier et al, 2013)
There are about 350 estuaries along the U.S. Pacific Coast. Basic descriptive data for these
estuaries, such as their size and watershed area, are important for coastal-scale research,
conservation planning, and predicting effects of climate change. However, this information is
spread among many sources, making it difficult to find and standardize. The goal of the
WestuRe Project is to provide a framework to: 1) make general descriptive data for estuaries and
for their watersheds and climates more accessible; and 2) provide tools to make analyzing and
visualizing these data easier. The WestuRe download includes data describing U.S. Pacific
Coast estuaries and their corresponding watersheds from northern Washington to southern
California (Tijuana Estuary), excluding Puget Sound proper.
WestuRe tools help users extract and view relevant data using the statistical program R and
Google Earth, and WestuRe provides shapefiles of estuary and watershed polygons as well as
.csv files summarizing geomorphological and climate data. Specifically, WestuRe allows the
user to access: 1) NWI habitat polygons classified as marine, estuarine, and tidal riverine for
each estuary, which can be overlaid on an image of an estuary from Goggle Earth; 2)
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Delineations of watershed boundaries from Lee and Brown (2009) for both "estuarine drainage
areas" (EDA) and "coastal drainage areas" (CDAs; coastal watershed that does not drain into an
estuary). In total, 506 polygons are provided; 3) NOAA salinity zones describing the average
annual and depth averaged salinity concentrations for 36 U.S. Pacific Coast estuaries (plus some
bays); and 4) Monthly climate data for sea surface temperature outside the mouth of each
estuary, air temperature at the mouth of the estuary, and air temperature and precipitation
averaged over the watershed. These data allow researchers and managers easy access to key
landscape and climate information for individual estuaries as well as the ability to compare
estuaries, watersheds, and climates along the U.S. Pacific Coast.
Summary:
Climate change poses a serious threat to the tidal wetlands of the Pacific Northwest. In response
to this threat, the U.S. EPA at the Western Ecology Division and the Western Fisheries Research
Center of the USGS, along with other partners, initiated a series of studies on marsh species and
communities, enhancing the SLAMM model to predict submerged aquatic vegetation (Zostera
marina) distributions, evaluating changes in flow into coastal estuaries, and synthesizing Pacific
Coast estuary, watershed, and climate data in a downloadable tool. Because the products
resulting from these efforts were published in a variety of locations, we summarized them in this
document. We anticipate that future research efforts by the U.S. EPA will continue to build
upon these products, in particular with a focus on climate change impacts on a regional scale.
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