NATIONAL WETLAND CONDITION
ASSESSMENT 2011
A Collaborative Survey of the Nation's Wetlands
Draft for Public Review and Comment
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NATIONAL WETLAND CONDITION ASSESSMENT 2011;
A Collaborative Survey of the Nation's Wetlands
Draft for Public Review and Comment
U.S. Environmental Protection Agency
Office of Wetlands, Oceans and Watersheds
Office of Research and Development
Washington, DC 20460
EPA-843-R-15-005
October 2015
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Acknowledgements
The U.S. Environmental Protection Agency (EPA) Office of Water (OW) and Office of Research and
Development (ORD) would like to thank the many people who contributed to this project. Without the
collaborative efforts and support by state and tribal environmental agencies, federal agencies,
universities, and other organizations, this groundbreaking assessment of wetlands would not have been
possible. In addition, the survey could not have been done without the innumerable field biologists, soil
scientists, taxonomists, statisticians, and data analysts, as well as program administrators, EPA regional
coordinators, project managers, quality control officers, and reviewers. To the many hundreds of
participants, EPA expresses its profound thanks and gratitude.
State and Tribal Agency Partners
Alaska Department of Environmental Conservation
Alabama Department of Environmental
Management
Arizona Department of Environmental Quality
California State Water Resources Control Board
Colorado Natural Heritage Program
Delaware Department of Natural Resources and
Environmental Control
Fort Peck Tribe
Georgia Department of Natural Resources
Georgia Environmental Protection Division
Florida Department of Environmental Protection
Idaho Department of Environmental Quality
Illinois Natural History Survey
Iowa Department of Natural Resources
Kansas Alliance for Wetlands and Streams
Kansas Department of Health and the Environment
Kansas Water Office
Kentucky Division of Water
Leech Lake Band of Ojibwe, Division of Resource
Management
Maine Department of Environmental Protection
Maryland Department of the Environment
Massachusetts Bays National Estuary Program
Massachusetts Department of Environmental
Protection
Michigan Department of Environmental Quality
Minnesota Pollution Control Agency
Missouri Department of Natural Resources
Federal Partners
U.S. Army Corps of Engineers
U.S. Department of Agriculture, Forest Service
U.S. Department of Agriculture, Natural Resource
Conservation Service
U.S. Department of Interior, Fish and Wildlife Service
Montana Natural Heritage Program
Navajo Environmental Protection Agency
Nebraska Game and Parks Commission
New Hampshire Department of Environmental
Services
New Jersey Natural Heritage Program
New Mexico Environment Department
New Mexico Natural Heritage Program
New York Natural Heritage Program
North Carolina Department of Environment and
Natural Resources
North Dakota Department of Health
Ohio Environmental Protection Agency
Oklahoma Conservation Commission
Oregon Department of Environmental Quality
Oregon Division of State Lands
South Carolina Department of Health and
Environment Control
Utah Division of Water Quality
Utah Geological Survey
Vermont Department of Environmental
Conservation
Virginia Department of Environmental Quality
Washington State Department of Ecology
West Virginia Department of Environment
Protection
Wind River Environmental Quality Commission
Wisconsin Department of Natural Resource
U.S. Department of Interior, National Park Service
U.S. EPA Office of Research and Development
U.S. EPA Off ice of Water
U.S. EPA Regions 1-10
U.S. Geological Survey
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Other Partners and Collaborators
Battelle Memorial Institute
BioLogics
California State University System - Moss Landing
Marine Laboratories
Center for Plains Conservation and Biodiversity
Dynamac
East Carolina University
EcoAnalysts, Inc
Great Lakes Environmental Center
Kenyon College
Michigan State University
Midwestern Biodiversity Institute
Nature Serve
New England Interstate Water Pollution Control
Commission
North Carolina State University
North Dakota State University
Oregon State University
Partnership for the Delaware Estuary
Pennsylvania State University
San Francisco Estuarine Institute
Southern California Coastal Water Research Project
Tetra Tech, Inc.
University of Central Missouri
University of Florida
University of Houston-Clear Lake
University of Nebraska-Lincoln
Virginia Institute of Marine Sciences
Virginia Tech University
Wells National Estuarine Reserve
Tom Dahl, Bill Wilen, Mitch Bergeson, and Rusty Griffin from the U.S. Fish and Wildlife Service's National
Wetland Inventory Program provided invaluable technical assistance on national wetland mapping and
extent data and generated wetland maps of the NWCA sites.
Lenore Vasilas, Phil King, Steve Monteith, Chris Smith, Larry West, Leander Brown, Rich Ferguson, and
Edward Griffin from the USDA Natural Resource Conservation Service Soil Science Division provided
invaluable technical support and advice developing field protocols, training field crews, reviewing field
data and processing soil samples for NWCA.
The following people played a pivotal role and lent their expertise to the data analysis in this project:
Mary Kentula, Teresa Magee, Karen Blocksom, Tony Olsen, Steve Paulsen, Tom Kinkaid, Marc Weber,
Dave Peck, Anett Trebitz, Brian Hill, and Janet Nestlerode from EPA Office of Research and
Development; Amanda Nahlikand Siobhan Fennessyfrom Kenyon College; Alan Herlihyfrom Oregon
State University; Josh Collins from San Francisco Estuary Institute; Gregg Lomnickyfrom Dynamac
Corporation; Marlys Cappaert from SRA International, Inc; and Keith Loftin from U.S. Geological Survey.
The report was written by a team of contributors that included Mary Kentula, Teresa Magee, and Steve
Paulsen from EPA Office of Research and Development, Amanda Nahlik from Kenyon College; Alan
Herlihyfrom Oregon State University; Gregg Lomnickyfrom Dynamac; Gregg Serenbetz, Laura Nollen,
Sue Bartow, Sarah Lehmann, Regina Poeske, Chris Faulkner, Mike McDavit, and Susan Holdsworth from
EPA Office of Water; and Annie Rossi, an ORISE Research Participant on the National Wetland Condition
Assessment (NWCA).
We would also like to acknowledge the contributions of several EPA interns and managers who are no
longer on the NWCA project team but whose support and leadership were instrumental in the planning
and field implementation of NWCA. Mike Scozzafava and Lynda Hall from EPA Office of Water led NWCA
efforts through these stages and Elizabeth (Riley) Donovan, Leah Medley, Natalie Allen, and Rachel
Sullivan provided outstanding technical and project research as ORISE participants during their time on
NWCA.
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Table of Contents
Acknowledgements i
Table of Contents iii
Tables and Figures v
State and Partner Highlights vii
Executive Summary viii
Key Findings viii
Biological Condition viii
Indicators of Stress ix
Implications ix
Chapter 1: Introduction 1
What are wetlands? 1
Why are wetlands important? 2
Why do we need a national assessment of wetland condition? 6
How was the national assessment developed? 7
Chapter 2: Design of the National Wetland Condition Assessment 11
Which wetlands are included in the NWCA? 11
How are the NWCA results presented? 13
How were the sampling sites chosen and what do they represent? 14
How were wetlands sampled? 17
What data were collected and why? 21
How were the NWCA core data used to report on ecological condition and stress? 23
Evaluating Wetland Biological Condition 27
Evaluating Indicators of Stress 31
Estimating the extent of wetland area for condition classes or stress-level classes 37
Other data collected as part of NWCA 2011 but not reported in national and regional results 37
Water Chemistry 37
Algae Species Data 38
Chapter 3: National Results 42
Biological Condition Based on Vegetation MMI 43
Indicators of Stress 45
Physical 45
Chemical 47
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Biological 49
Ranking of Stressors 50
Relative Extent and Relative Risk 50
Attributable Risk 51
Microcystin Presence and Risk 52
Chapter 4: Ecoregion and Wetland Type Results 57
Coastal Plains Ecoregion 59
Landscape setting of the ecoregion 59
Summary of findings 60
Eastern Mountains and Upper Midwest 65
Landscape setting of the ecoregion 65
Summary of findings 66
Interior Plains 75
Landscape setting of the ecoregion 75
Summary of findings 76
West Ecoregion 79
Landscape setting of the ecoregion 79
Summary of findings 80
Estuarine Wetlands 83
Landscape setting for estuarine wetlands 83
Summary of findings 83
Chapter 5: Summary and Next Steps 86
Summary of Major Findings and Implications 86
Advancing Wetland Science 87
Next Steps: Preparing for the 2016 Assessment 88
Glossary of Terms 94
Sources and References 99
List of Abbreviations and Acronyms 103
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Tables and Figures
Table 2-1. FWS S&T Wetland Categories that comprise the NWCA Target Wetland Types 12
Table 2-2. Number of probability sites sampled nationally and within each of the NWCA Aggregated
Ecoregions and acres of wetland area these sites represent 16
Table 2-3. Heavy metals included in the Heavy Metal Index as a chemical indicator of stress 33
Table 2-4. Soil phosphorus concentration thresholds as chemical indicators of stress 34
Table 2-5. World Health Organization thresholds of risk associated with exposure to microcystin 34
Table 2-6. Summary of NWCA 2011 indicators of condition and stress and information on how
thresholds were set 36
Figure 1-1. Examples of wetlands commonly found across the U.S 3
Figure 2-1. Nine Aggregated Ecoregions used in other NARS (map on left) further combined into the four
NWCA Aggregated Ecoregions (map on right) 13
Figure 2-2. NWCA Sample Sites 15
Figure 2-3. Standard NWCA assessment area and buffer sampling layout 18
Figure 2-4. Core data types and relationships to how they are used to develop indicators of condition
and stress 24
Figure 2-5. Criteria for setting VMMI thresholds for good, fair, and poor condition classes based on
VMMI values observed for Least Disturbed (Reference) sites 28
Figure 3-1. Estimated extent of wetland biological condition by condition classes (good, fair, poor) based
on the VMMI 44
Figure 3-2. Estimated extent of vegetation alteration in wetlands by stressor levels as indicated by
vegetation removal and vegetation replacement 46
Figure 3-3. Estimated extent of hydrologic alteration in wetlands by stressor levels as indicated by
damming, ditching, hardening, and filling/erosion 47
Figure 3-4. Estimated extent of chemical indicators of stress in wetlands by stressor levels as indicated
by a Heavy Metal Index and soil phosphorus concentrations 48
Figure 3-5. Estimated extent of biological stress in wetlands by stressor levels as indicated by the
Nonnative Plant Stressor Indicator 49
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Figure 3-6. National level estimates for relative extent of stressor indicators when stressor level is high,
relative risk associated with each stressor indicator, and attributable risk for each stressor
indicator relative to wetland biological condition 51
Figure 3-7. Estimated occurrence of microcystin in wetlands 53
Figure 3-8. Estimated extent of recreational health risk from exposure to microcystin by risk category
(low, moderate, and high) based on WHO guidelines 54
Figure 4-1. The NWCA Aggregated Ecoregions 58
Figure 4-2. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the Coastal
Plains 61
Figure 4-3. NWCA survey results for the inland herbaceous wetland type across the Coastal Plains 61
Figure 4-4. NWCA 2011 survey results for the inland woody wetland type across the Coastal Plains 62
Figure 4-5. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the Eastern
Mountains and Upper Midwest 67
Figure 4-6. NWCA 2011 survey results for the inland herbaceous wetland type across the Eastern
Mountains and Upper Midwest 68
Figure 4-7. NWCA 2011 survey results for the inland woody wetland type across the Eastern Mountains
and Upper Midwest 68
Figure 4-8. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the Interior
Plains 77
Figure 4-9. NWCA 2011 survey results for the inland herbaceous wetland type across the Interior Plains.
78
Figure 4-10. NWCA 2011 survey results for the inland woody wetland type across the Interior Plains.... 78
Figure 4-11. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the West.
81
Figure 4-12. NWCA 2011 survey results for the inland herbaceous wetland type across the West 82
Figure 4-13. NWCA 2011 survey results for the inland woody wetland type across the West 82
Figure 4-14. NWCA 2011 survey results for estuarine herbaceous wetland types across all coastal areas
of the conterminous U.S 84
Figure 4-15. NWCA 2011 survey results for estuarine woody wetland types across all coastal areas of the
conterminous U.S 85
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State and Partner Highlights
Gulf of Mexico Coastal Wetlands Pilot Project: Setting the Stage for the NWCA 9
California's Intensification Project: Learning More about California's Wetlands and Refining Monitoring
Techniques 19
Wisconsin's Intensification Study: A Floristic Characterization of Wetlands in Eastern Wisconsin 29
Nebraska's Intensification Project: Impacts of Land Use and Management on Wetland Condition 39
Alaska's Arctic Wetlands Assessment 55
Southeast Wetlands Monitoring and Assessment Intensification Study: North Carolina, South Carolina,
Alabama, and Georgia 63
Establishing a Baseline for Ohio's Valuable Wetland Resources: A National Wetland Condition
Assessment Intensification 69
Minnesota's Intensification Project: NWCA Intensification Survey Helps Reveal Important Regional
Variation in Minnesota 72
The U.S. Fish and Wildlife Service's Wetlands Status and Trends Program 90
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Executive Summary
The National Wetland Condition Assessment (NWCA) 2011: A Collaborative Survey of the Nation's
Wetlands presents the results of the first national evaluation of the ecological condition of the nation's
wetlands. The NWCA is part of a broader effort by EPA and state, tribal, and federal partners to conduct
national scale assessments characterizing the ecological condition of the nation's waters. Under the
National Aquatic Resource Survey (NARS) program, studies have been completed for wadeable streams
(2004), lakes (2007), rivers and streams (2008-2009), and coastal waters (2010). The issuance of the
NWCA 2011 report marks the completion of the first full-cycle of assessments by EPA and its partners
under the NARS program.
Wetlands are a vital component of our nation's waters, providing a wide array of benefits that
contribute to the overall health and integrity of aquatic ecosystems and people's well-being. Wetlands
help improve water quality by filtering pollutants, protecting downstream or coastal areas from floods
and erosion, serving as homes or sources of food for a diverse and abundant range of species including
humans, and offering places for recreation and scientific and cultural exploration. Though we are aware
of the important benefits wetlands provide, we know very little about the overall ecological condition of
these systems nationally. The NWCA begins to address some of the gaps in our understanding of
wetland health by providing information about the ecological condition of the nation's wetlands and
stressors most commonly associated with poor condition.
During the spring and summer of 2011, more than 50 field crews sampled 1,179 wetland sites across the
country. Each crew used standardized field protocols to sample vegetation, soils, hydrology, algae, water
chemistry, and potential stressors at each site. Most sites were selected using a random sampling
technique that ensures that the results of the survey reflect the range of wetlands in the target
population across the U.S. Data collected at these randomly selected sites are used to produce national
and regional estimates of wetland condition.
Key Findings
Biological Condition
Vegetation is a major component of the biodiversity and structure found in wetlands, provides
important habitat and food sources for birds, fish, and other wildlife, and both responds to and
influences other physical features (e.g., soils, hydrology) and chemical processes (e.g., nutrient cycling)
in wetland systems. Thus, vegetation can reflect and integrate different components of wetland
ecosystem integrity and serve as an effective indicator of wetland condition. NWCA 2011 uses
vegetation to assess the condition of wetlands across the conterminous U.S. and in four major
ecoregions. Vegetation data collected at each sampling site was used to develop a national Vegetation
Multi-Metric Index (VMMI), which indicates "good," "fair," or "poor" condition based on properties of
vegetation that vary in relation to human-mediated disturbance. For NWCA 2011, "good" condition
generally reflects diversity and abundance levels for species and plant traits (e.g., native species,
tolerance for disturbance) appropriate to ecoregion and wetland type.
NWCA 2011 found that nationally, 48% of the wetland area is in good condition, 20% is in fair condition
and the remaining 32% of the area is in poor condition. Of the four major ecoregion-based units
reported on by NWCA, the West has the lowest percentage of wetland area, 21%, in good condition. The
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Executive Summary
Coastal Plains, Eastern Mountains and Upper Midwest, and Interior Plains have a range of 44% to 52%
wetland area in good condition.
Indicators of Stress
Wetland condition can be influenced by physical, chemical, and biological factors that impact (i.e., cause
stress to) a wetland's physical structure or ecological processes. NWCA 2011 developed and measured a
number of physical, chemical, and biological indicators of stress that reflect potential negative impact to
wetland condition. At each site, all of these indicators were evaluated in a core assessment area and
within a surrounding 100 meter radius buffer. Indicators of stress at each wetland site are assigned to
"low," "moderate," or "high" stressor levels depending on criteria established for each indicator.
Physical
Six physical indicators of stress are assessed for NWCA using field-based observational data collected at
each site. These indicators represent physical alterations to vegetation (removal and replacement) or
hydrologic alterations (damming, ditching, surface hardening, and filling/erosion) observed at the
sampling site. Vegetation removal, surface hardening (e.g., pavement, soil compaction), and ditching are
found to be the most widespread stressors nationally. Vegetation removal and hardening stressors are
high for 27% of wetland area, while the ditching stressor is high for 23% of wetland area.
Chemical
Two chemical indicators of stress are assessed for NWCA using soil data collected at each site: a Heavy
Metal Index and soil phosphorus concentration. Stressor levels for both of these indicators are low for
the majority of wetland area nationally. However, stressor levels for the Heavy Metal Index are
moderate for 47% of wetland area in the West and 31% of wetland area in the Eastern Mountains and
Upper Midwest. Stressor levels for soil phosphorus are high for 13% of wetland area in the Eastern
Mountains and Upper Midwest.
NWCA conducted the first national study of algal toxins in wetlands. Microcystin, a chemical toxin that
can harm people, pets, and wildlife, was detected in 12% of wetland area nationally. However, based on
recreational exposure risk levels established by the World Health Organization, very little wetland area
(<1%) poses either moderate or high risk levels.
Biological
A Nonnative Plant Stressor Indicator developed for NWCA is used to assess the level of biological stress
in wetlands. Nationally, 61% of wetland area has low stressor levels for nonnative plants. These results
are not uniform across the country, however. The Eastern Mountains and Upper Midwest and the
Coastal Plains have similar percentages of low stressor levels, 74% and 66% of wetland area,
respectively, for the nonnative plant stressor indicator. In contrast, the West and Interior Plains have
only 14% and 27% of wetland area, respectively, with low stressor levels.
Implications
For resource managers and other decision-makers, the NWCA provides important information about the
condition of wetlands and several wide-spread stressors influencing their biological condition.
Additionally, the results point to potential improvement in condition that might be seen nationally by
reducing these stressors. The NWCA found that wetlands with high levels of vegetation removal and
surface hardening stress are about twice as likely to have poor biological condition as those with low or
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Executive Summary \
moderate levels of these stressors. Further analysis that looks at how condition might improve if these
two stressors are reduced, called attributable risk, suggests a possible 20% reduction in wetland area
with poor biological condition if the stressor level changed from high to moderate or low.
The NWCA developed a robust VMMI that was successfully used to evaluate the condition of wetlands
across major ecoregions and wetland types. In addition, NWCA developed several indicators of stress
based on readily collected field data and used these to evaluate the relationship between common
stressors and biological condition. NWCA scientists also conducted research into other potential
indicators of wetland condition, and while not highlighted in this public report, findings from this
research will help inform future scientific studies.
The NWCA marks a beginning in our endeavors to assess wetland condition nationally. Work conducted
under the NWCA has advanced the state of science into indicators of wetland condition and improved
our ability to evaluate wetland condition at national and regional scales. Subsequent studies and
research by EPA, states, and other partners will continue to build upon the knowledge gained through
the NWCA and allow us to further explore and evaluate the condition of wetlands at multiple scales. We
will be better able to answer important policy and management questions about the overall health of
this critical resource, and design effective strategies to fulfill the objectives of the Clean Water Act—to
restore and maintain the chemical, physical, and biological integrity of the nation's waters.
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Chapter 1: Introduction
The National Wetland Condition Assessment (NWCA) 2011 is the first national evaluation of the
ecological condition of the nation's wetlands. The survey encompassed both tidal and nontidal wetlands
ranging from the expansive marshes of our coasts to the forested swamps, meadows, and waterfowl-
rich prairie potholes of the interior plains.
The NWCA is part of a broader effort by EPA, state, tribal, and federal partners to conduct national-scale
assessments characterizing the ecological condition of the nation's waters. Under the National Aquatic
Resource Survey (NARS) program, studies have been completed for wadeable streams (2004), lakes
(2007), rivers and streams (2008-2009), and coastal waters (2010). NWCA 2011 marks the completion of
the first full cycle of NARS assessments. EPA and its partners plan to continue to conduct the surveys on
a five-year basis, rotating through each of the aquatic resources beginning with lakes and ending each
cycle with wetlands.
Similar to the other NARS studies, the NWCA identified the following key goals for the project:
• Produce a national report describing the ecological condition of the nation's wetlands and
stressors commonly associated with poor condition;
• Collaborate with states and tribes in developing complementary monitoring tools, analytical
approaches, and data management technology to aid wetland protection and restoration
programs; and
• Advance the science of wetland monitoring and assessment to support wetland
management needs.
The NWCA builds not only upon the groundbreaking work of its sister NARS studies, but also that of the
U.S. Fish and Wildlife Service's (FWS) Wetland Status and Trends (S&T) program, which has been
documenting changes to the extent of wetland area in the U.S. for more than 30 years. Taken together,
these two efforts provide government agencies, wetland scientists, and the public with comparable,
scientifically-defensible information documenting the current status and, ultimately, trends in both
wetland quantity (i.e., area) and quality (i.e., ecological condition). These studies help us to better
understand the overall condition and health of all of our nation's waters and provide information to
more effectively manage and protect this valuable resource.
This report presents the major findings of NWCA 2011. It begins with an introduction on wetlands and
the importance of these aquatic systems. Subsequent chapters provide information on the design and
implementation of the study, national and regional results, and the study's implications and next steps.
Key concepts and study components are emphasized in special text boxes throughout the report. In
addition, there are a number of highlights provided by states and other partners detailing studies and
work associated with NWCA.
What are wetlands?
"Wetlands" is the collective term given to areas of the landscape that are transitional between land and
water. Some wetlands occur alongside streams, rivers, lakes, and coastal waters, while others occur in
depressions and other low-lying areas apart from surface waters, and still others are associated with
springs high in the mountains. Wetlands can be saturated with water at varying intervals throughout the
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Chapter 1 \ Introduction
day and year, and have plant and animal communities adapted to live in conditions ranging from
permanently wet to fluctuating wet and dry. Wetlands are defined by three important attributes:
• plants that have adapted to survive and thrive in wet conditions (known as hydrophytes);
• soils that exhibit features of prolonged saturation and changing wet and dry cycles; and
• the presence of water at or near the surface of the ground for a time sufficient to produce soils
and plant communities characteristic of wetlands.
Scientific and regulatory definitions for wetlands can differ in the criteria used to incorporate these
three attributes. The NWCA uses a scientific definition for wetlands described by Cowardin et al. (1979)
that is broader than the regulatory definition of wetlands used in the federal Clean Water Act (CWA).
Thus, NWCA includes wetlands that may not be considered jurisdictional for purposes of the CWA.
COWARDIN DEFINITION OF WETLANDS
Wetlands are lands transitional between terrestrial and
aquatic systems where the water table is usually at or
near the surface or the land is covered by shallow water.
For purposes of this classification wetlands must have
one or more of the following three attributes:
(1) at least periodically, the land supports
predominantly hydrophytes;
(2) the substrate is predominantly undrained hydric
soil; and
(3) the substrate is nonsoil and is saturated with
water or covered by shallow water at some time
during the growing season of each year.
Wetlands take on a variety of different forms
and are known by many different names
depending on their principal characteristics
and location in particular regions of the
country. Some examples include marsh, wet
meadow, swamp, bog, and prairie potholes.
See Figure 1-1 for pictures and descriptions of
several common wetland types.
A number of classification systems have been
developed based on distinctive wetland
characteristics to organize the many kinds of
wetlands into groups that share similar
attributes. The two most common systems
used nationally are the Cowardin and the
Hydrogeomorphic (HGM) classification
systems. The Cowardin system considers water regime, the underlying substrate and vegetation
communities to catalog wetland and deep water habitats (Cowardin et al. 1979). The HGM system
considers the wetland's location in the landscape (i.e., proximity to a lake, stream, or topographic
setting), along with its morphology, primary water sources, and hydrodynamics (Brinson 1993).
Why are wetlands important?
Wetlands are found on every continent and make up an estimated 5 to 8% of the Earth's land surface
(Mitsch and Gosselink 2007; Zhu et al. 2014). In the U.S., wetlands are found in every state, from the
tundra of Alaska to the playas of the Great Plains and the swamps of the Florida Everglades. Wetlands
even occur in the driest areas of the American West. Wetlands often occur on the edges of lakes, rivers,
streams, coastal seas, and other surface water bodies, but also occur independent of these waters
where precipitation or groundwater is abundant enough to sustain plants, soils, and animals that are
characteristic of wetlands.
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Chapter 1 | Introduction
Freshwater Swamps
Occurring in low-lying areas, such as f loodplains, throughout the United
States, these tidal and nontidal freshwater wetlands are dominated by
shrubs or trees that thrive under saturated conditions. Other common
names include bottomland hardwood, tupelo, or bald cypress swamps.
Freshwater Marshes and Meadows
Occurring alongside lakes, streams, rivers, or in poorly drained depressional
areas throughout the United States, these freshwater wetlands are
dominated by grasses and other non-woody plants. Certain types like wet
meadows and prairies are often dry during some parts of the year.
Peatlands, Bogs, and Fens
These freshwater wetlands are characterized by spongy peat deposits,
growths of evergreen trees and shrubs, and ground cover of sphagnum
moss. They are usually found in glaciated areas of the northern United
States but a special type called a pocosin, occurs throughout the
southeast coastal plain.
Shallow Ponds
These wetlands are covered by surface water that can be up to two meters
deep. Common vegetation includes lily pads and other floating and
submerged water plants that survive in deeper water. Prairie potholes in
the north central United States and playa lakes in the southern great
plains are other common types.
Salt Marshes
Occurring along the coastlines of the United States, these saltwater
wetlands are influenced by ocean tides and dominated by grasses and
other non-woody plants such as smooth cordgrass, saltgrass. and
saltmeadow rush.
Mangrove Swamps
Occurring in brackish and saline tidal waters along the coast of the
southeastern United States, these wetlands are dominated by species of
mangroves and serve as valuable nurseries for a variety of recreational ly-
and commercially-valuable marine fish.
Figure l-l. Examples of wetlands commonly found across the U.S.
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Believed to be an obstacle to development for much of our country's history, wetlands were often
drained and filled to make way for other uses. The FWS estimates that more than 220 million acres of
wetlands existed in the conterminous U.S. prior to European settlement. Since then, extensive losses
have occurred and over half of those wetlands have been drained and converted to other uses (Dahl
1990). Beginning in the 1970s, the rate of wetland losses slowed substantially as a result of changes in
national and state wetland policies and heightened awareness of the important benefits aquatic
systems, including wetlands, bring to society.
We now know that wetlands are a vital component of the nation's waters and provide many crucial
benefits including water quality improvement, flood abatement and carbon storage, biodiversity
support, plus aesthetic, recreational, educational, and scientific opportunities. Today these benefits are
part of the decision process when permits are issued for activities that result in the loss or degradation
of wetlands.
Wetlands play a critical role in sustaining healthy surface and ground waters. The physical structure of
wetlands can allow them to intercept the flow of surface water, resulting in the retention and filtration
of nutrients, sediment, and pollutants. Microbes living in wetlands can break down or transform
potentially toxic compounds. Plants and microbes also consume and transform excess nutrients,
improving water quality and slowing eutrophication of downstream waters. Together these wetland
processes often reduce the amount of undesirable substances entering other surface water bodies (e.g.,
rivers, streams, lakes, coastal waters) where they can degrade water quality and pose environmental
and human health risks.
Wetlands can act as natural sponges, capturing and slowly releasing surface water resulting from heavy
rains, snow melt, and other floodwaters. Trees, grasses, and other wetland plants help slow the speed of
floodwaters and disperse the excess water across floodplains. These processes lower flood heights,
reduce erosion, and decrease the otherwise destructive effects of swiftly moving floodwaters. In
addition, wetlands at the edges of lakes, rivers, bays, and the ocean buffer shorelines from the
damaging effects of storm surges caused by hurricanes, tropical storms, and other powerful weather
events.
The position of wetlands at the interface of land and water make them some of the most biologically
diverse and productive ecosystems in the world. Many unique plant communities provide diverse plant
species, physical structure, and distinct aesthetics to wetlands. A great variety of life from the tiniest
microbes to plants, birds, fish, and mammals inhabit and depend upon wetlands for part or all of their
life-cycles. Chemical and biological processes occurring within wetlands provide abundant supplies of
food for a diverse range of species. Microbes and small aquatic insects break down dead plant material,
forming small particles of organic material that feed larger aquatic insects and shellfish. These, in turn,
feed fish and wildlife. Wetland dependent fish species make up 71% of the commercial and recreational
fisheries in the U.S. (Fisheries and Water Resources Policy Committee 2004). Ducks and other waterfowl
depend on wetlands for food and shelter. For example, prairie potholes and marshes dotting the
Midwest are rich in plant and aquatic life vital for breeding waterfowl. Bogs and fens are important
habitat for rare plants and animals. About 50% of threatened or endangered animal species in the U.S.
depend on wetlands for their survival and 28% of threatened or endangered plant species are associated
with wetland ecosystems (Mitsch and Gosselink 2007).
Wetlands provide plentiful opportunities for recreation and enjoyment by people. Bird and other
wildlife watchers are drawn to wetlands to view or photograph the diverse species that call wetlands
home. Hunters wade or boat through wetlands to hunt waterfowl. The abundance of fish in some types
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Chapter 1 | Introduction
of wetlands attracts fishermen to these habitats. Marsh ecosystems line our coasts and provide food
supply, shelter, and nursery areas for both marine and freshwater species, fueling a commercial and
recreational fishery economy worth billions of dollars (Fisheries and Water Resources Policy Committee
2004). The 2011 National Survey of Fishing, Hunting, and Wildlife-Associated Recreation revealed that
over 90 million U.S. residents participated in wildlife-related recreation such as fishing, hunting, or
wildlife watching. This recreation is entirely dependent on having clean and healthy waters, including
wetlands, to support the fish and wildlife at the center of these activities.
Wetlands are important settings for scientific research. Tens of thousands of research papers have been
published about wetlands by scientists since the 1950s, and today, wetlands continue to be the subject
of much scientific research, including studies on nutrient cycling, global climate change, bird migration,
unique plant communities, and countless others. Despite all of the historic and current wetlands
research, the NWCA is the first assessment to characterize the ecological condition of wetlands on a
national scale. The NWCA also has inspired dozens of researchers to conduct novel scientific research
that will add to our knowledge of wetlands and their importance in our national, global, and human
environments.
WATER CLEANSING PROCESSES OF NATURAL WETLANDS AND THEIR USE IN ENGINEERED WATER
TREATMENT SYSTEMS
Wetlands are vital to the health of waterways and downstream communities. Wetlands can naturally remove
excess nutrients, sediment and other pollutants, keeping them from reaching lakes, streams and the ocean.
The result is cleaner water resources and a healthier aquatic ecosystem.
After being slowed by the vegetation in a wetland, incoming water moves around plants, allowing suspended
sediment to drop out and settle to the wetland bottom. Nutrients dissolved in water—which reach wetlands
from various sources including anthropogenic ones such as fertilizer application, manure, leaking septic tanks,
and municipal sewage—are often absorbed by plant roots and microbes in the soil while other pollutants
adhere to soil particles. In many cases, this filtration process removes much of the water's nutrient and
pollutant load by the time it leaves a wetland.
Engineers have designed water treatment facilities to use similar processes to remove pollutants through
coagulation, settling (in sedimentation tanks), filtration, and disinfection. Just as with the natural processes in
wetlands, stormwater and sewage go through physical, chemical and biological processes at treatment
facilities which clean the wastewater. Constructed wetlands are treatment systems that use natural processes
involving wetland vegetation, soils, and their associated microbial assemblages to improve water quality.
Around the world, thousands of constructed wetlands have been created to replicate the water cleaning
abilities of natural wetlands.
s,
Gravel Substrate
Impermeable Liner
Picture from USEPA 2004
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Chapter 1 \ Introduction
Why do we need a national assessment of wetland condition?
Efforts by the FWS S&T program have provided national scale information on the location and extent of
wetlands (i.e., the areal coverage on the landscape) since the 1950s. Their most recent report, published
in 2011, found a slight decrease in wetland area between 2004 and 2009. While the report noted gains
for some wetland types, such as freshwater ponds, it found continued declines in area of forested
wetlands and salt marshes. Companion reports focused specifically on wetlands in coastal watersheds
(2013) and the prairie pothole region (2014) also found that wetland area is decreasing in these areas.
See "The U.S. Fish and Wildlife Service's Wetland Status and Trends Program" highlight at the end of
Chapter 5 for more information on this program.
While the S&T reports provide invaluable information on wetland extent and change among wetland
types, they do not provide data on wetland condition. Compared to other aquatic systems, such as
lakes, streams, rivers, and coastal waters, wetlands have not been comprehensively assessed to
determine their condition or ability to meet water quality goals under the CWA. In a 2002 Water Quality
Report to Congress, information provided by states addressed only 1% of the estimated area of
wetlands, compared to approximately 20% of streams and rivers, 40% of lakes, and 35% of coastal
waters (USEPA 2007). The lack of data makes it difficult to answer basic questions about the condition of
our wetlands nationwide and to support key management decisions for most effectively protecting and
restoring this valuable resource.
The NWCA is designed to address the gaps that exist in our understanding of wetland condition. EPA and
its state, tribal, academic, and federal agency partners, are collaborating to provide improved
environmental information about wetlands at national and regional scales. The NWCA, like all NARS
assessments, is a statistical survey that provides a cost-effective and scientifically-valid way for
informing the public and decision-makers about wetland quality because it:
• Is nationally consistent,
• Produces data representative of the resource being sampled,
• Uses standardized field and laboratory protocols, and
• Follows rigorous quality assurance protocols.
The findings of the NARS are not water quality reports prepared by the states under Section 305(b) of
the CWA, nor are they impaired water determinations under Section 303(d) of the CWA. Such
determinations are made by states on specific water body segments using applicable state water quality
standards. State CWA monitoring and assessment approaches may vary significantly from those used in
NARS and may yield different results (see text box "How Does NARS Reporting Differ from State Water
Quality Reports Required by the CWA?").
Rather, the NARS are designed to answer such questions as:
• What percent of waters support healthy biological and recreational condition?
• How widespread are major stressors that impact water quality?
• How is condition changing over time?
• Are our national investments in the protection and restoration of aquatic systems working?
The focus of the surveys is on water bodies as groups or populations, rather than as individual waters.
Accordingly, this report does not provide wetland managers with information on the condition of a
specific wetland. Instead, the NWCA allows us to assess the percent of wetland area within particular
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Chapter 1 | Introduction
condition classes (e.g., good, fair, poor) at the national scale and in four major ecoregions across the U.S.
As additional surveys are implemented, we will be able to track changes in condition over time as well.
HOW DOES NARS REPORTING DIFFER FROM STATE WATER-QUALITY REPORTS REQUIRED BY THE CWA?
Under Section 305(b) of the CWA, states are expected to monitor, and are required to assess and report on the
condition of their waters, including the extent of waters that support the goals of the Act. Under Section 303(d), states
are to identify waters that are impaired, do not meet state water quality standards, and require additional pollution
controls. States use a variety of monitoring and assessment approaches to meet these requirements of the CWA and to
address state-specific information needs for managing state waters.
States usually collect information for many parameters at locations of importance to the state, such as swimming
beaches, near dischargers, or at drinking water sources using methods developed for the state's specific purposes.
However, state methods of collecting and assessing data can change over time and vary widely between states; so too
tdo the state water quality standards used to determine impairment. This makes it difficult to aggregate this information
for the nation as a whole, or over time. State monitoring programs are not designed to answer national-level questions
such as whether or not U.S. water quality is improving.
One of the long-term goals of the NARS is to determine trends for the nation as a whole. To do this, the surveys use a set
of standardized methods to monitor for a discrete set of stressors. Field crews collect the same data at each of the
randomly selected, representative sites across the country; results are compared to conditions at least-disturbed sites in
the ecoregions (and not to state water quality standards). Survey results are then aggregated into an overall assessment
of water quality. It is the intent of EPA that these surveys complement state-specific CWA information and provide
national and regional context to decision-makers.
*
o learn more about state CWA reporting, visit www.epa.gov/waters/ir/.
How was the national assessment developed?
EPA began planning for the NWCA in 2006. Throughout the planning process, EPA engaged with a broad
group of stakeholders from state environmental and natural resource agencies, tribes, federal agencies,
academia, and other organizations to help inform different aspects of the assessment. Planning the first-
ever national survey of wetland condition entailed a number of steps, each with its own set of
challenges to overcome, including, but not limited to, creating a survey design, selecting efficient,
scientifically valid indicators, developing new field protocols, and piloting protocols. The development
and selection of the NWCA field methods were also influenced by logistic considerations, such as the
need to complete sampling for each site in one day.
In addition to reporting on the condition of wetlands nationally, another objective of the NWCA is to
provide support to states and tribes that are interested in pursuing research to develop assessment
methodologies and undertake statistically valid surveys of wetlands at finer geographic scales (i.e., within
state or tribal boundaries). To accomplish this, EPA encouraged and provided support for states to do
more intensive sampling in conjunction with the NWCA at state or regional scales. These intensifications
involved sampling additional sites, parameters, or both within a state or region. States worked closely
with EPA to develop intensification survey designs. This resulted in projects throughout the country, with
state-driven focuses such as:
• Designing state-scale assessments that inform state-level management and policy needs;
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Chapter 1 \ Introduction
• Capturing wetlands of interest that may have been missed in the national survey due to being
rare (e.g., vernal pools); and
• Testing additional indicators or assessment procedures.
These intensifications serve to augment the national and ecoregion results of the NWCA 2011. Some of
these projects, as well as their findings, are highlighted throughout this report.
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Gulf of Mexico Coastal Wetlands Pilot Project: Setting the Stage for the NWCA
Janet Nestlerode, U.S. EPA Office of Research and Development, Gulf Ecology Division
Objectives: The EPA, in
collaboration with the
United States Geological
Service (USGS),
implemented a pilot project
along the northern coast of
the Gulf of Mexico (GOM) in
order to evaluate the
effectiveness of a three-tier
survey framework for
regional wetland
assessment. The results of
the pilot study provided
insight into the usefulness
of the chosen indicators in
determining condition and
provided several "lessons
learned" that were
beneficial to the
development of the NWCA
2011.
Site Habitat Type
A Eshattnt Mirth (E2EM)
• EMvannv Shrub (E25S)
rak.unntVa.-i)> iPEMI
* Shfub/Foi«W(PCS/PFO)
HUC Category
I | GOM Conul fttjfon
"" Hand
«0
^- mum
H
+
Figure 1. GOM coastal wetland survey sites shown with in the boundary of GOM
coastal watersheds as defined by all USGS 8-digit hydrologic unit code (HUC)
system segments that abut the coast and modified by NOAA's Estuarine Drainage
Areas where needed.
Overview: One hundred
wetland points along the GOM Coastal Region, which includes five states and 2,500 km of coastal
lands, were selected for the pilot study and included five wetland classes (Figure 1). Five hundred
oversample sites were also generated to replace original points that had to be dropped due to
inaccessibility, or for other reasons. A 3-tier assessment framework was implemented during the
2007 and 2008 field seasons. Landscape-level (tier 1) assessments were conducted off-site and (tier
2 and 3) sampling was undertaken by crew members for each site, typically within one field day.
Crews utilized a tier 2 rapid assessment, called the Gulf Rapid Assessment Method (GRAM), based
on the California Rapid Assessment Method (CRAM). Tier 3 (intensive site assessments) included the
collection of physical, chemical, and biological data at each site. This included soil and water
chemistry, vegetation and macrophyte samples, as well as other measures. Between the first and
second field seasons for the pilot, minor modifications were made to the field protocols.
Planning, logistics, and field conditions presented several challenges for the team before and during
the field season. These ranged from identifying landowners, obtaining permission to sample a site,
and determining how best to reach remote sites. Identifying landowners and gaining access to sites
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Chapter 1 \ Introduction
often proved difficult, as the team had to take into consideration both land ownership at the sample
site and ownership of lands that had to be crossed to access the site. Landowner records and access
to those records differed by localities, and it was a learning curve to find contact information and
coordinate access permissions.
During GOM pilot implementation, crews sampled sites that were often remote and/or difficult to
access. In South Florida, for example, getting to some sites required hiking for miles through waist-
deep waters and mucky soils, transportation by boat, 4-wheel drive sport utility vehicles, or swamp
buggies with balloon tires, or some combination of these modes of transportation. The team
coordinated with local experts to determine the best ways to access remote sites, but in some cases
sites were inaccessible and had to be dropped altogether.
Through data collection and analysis,
the pilot project identified gear and
equipment needed by survey crews, as
well as an appropriate division of
responsibilities among crew members.
Implementation of the pilot study also
provided an opportunity to determine
the time needed for various data
collection protocols, and helped gauge
what could realistically be
accomplished by crews within a single
field sampling day, once factoring in
travel times. This information was used
in the planning and protocol
development for the NWCA.
Swamp buggy used to access a remote wetland site in Big
Cypress National Preserve.
Overall, the GOM coastal wetlands
pilot project highlighted the great
cooperation and effort necessary to conduct a regional condition assessment, and it provided critical
information and lessons learned that informed planning efforts and development of the NWCA
2011.
To learn more, contact Janet Nestlerode (Nestlerode.Janet@epa.gov; 850-934-2492), EPA Office of
Research and Development, Gulf Ecology Division.
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Chapter 2: Design of the National Wetland Condition Assessment
The NWCA is designed to answer basic questions about the condition of our nation's wetlands and the
prevalence of key stressors at national and regional scales. As noted, it is intended to complement and
build upon the achievements of the FWS S&T Program, which characterizes changes in wetland acreage
across the conterminous U.S.
Which wetlands are included in the NWCA?
This report covers the conterminous U.S., which currently contain an estimated 110 million acres of
wetlands (Dahl 2011). Neither Alaska nor Hawaii are included in the national results presented in this
report. Wetlands in Hawaii were not sampled, but the State of Alaska conducted sampling on the North
Slope of the Alaskan coastal plain, using protocols similar to those used in the NWCA. A summary of the
results of the North Slope assessment are presented as a special highlight later in the report (see
"Alaska's Arctic Wetlands Assessment").
The specific wetlands targeted for sampling in the NWCA include tidal and nontidal wetlands within the
conterminous U.S. with rooted vegetation and, when present, shallow open water less than one meter
deep, that are not currently being used in the production of crops1. EPA used the same digital map of
wetland locations that FWS uses in their Wetlands S&T Program to select sites for sampling. The S&T
Program defines and classifies habitats into wetland, deep water, and upland categories and groups
wetlands into S&T categories based on hydrology, geomorphology, vegetation, and water chemistry
(Dahl 2011, Dahl and Bergeson 2009, Cowardin et al. 1979). EPA uses a subset of the S&T wetland
categories for the NWCA. Table 2-1 provides detailed descriptions of the seven S&T wetland categories
that are included in the target wetland population for NWCA.
Two major S&T wetland categories, Marine Intertidal (near shore coastal waters) and Estuarine
Intertidal Unconsolidated Shore (beaches, bars, and mudflats), are not included in the NWCA because
they are outside of the NWCA target population. They typically occur in deeper water (> 1 meter), or are
unlikely to contain rooted wetland vegetation. Unique wetland types with more limited extents across
the conterminous U.S. may also not be included, or may be underrepresented, in the NWCA 2011 if they
are not included in the S&T Program or due to inherent constraints associated with the number and
locations of the sites randomly selected for sampling.
1 Wetlands that have been mechanically or physically altered for the production of crops, but where wetland
plants would become reestablished if farming is discontinued, are identified in the FWS S&T Program as "farmed
wetlands." NWCA included these wetlands in its target population only if they were not currently being used for
the production of crops.
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Table 2-1. FWS S&T Wetland Categories that comprise the NWCA Target Wetland Types. Descriptions adapted from Dahl
(2006) and Dahl and Bergeson (2009). See NWCA 2011 Technical Report (USEPA 2015), Chapter 1 for more details.
S&T Categories included in
NWCA (NWCA Aggregated
Wetland Type)
Estuarine Intertidal Emergent
(Estuarine Herbaceous)
Common Name
Salt marsh
Technical Description
Emergent wetlands in estuarine system characterized by erect,
rooted, herbaceous hydrophytes, excluding mosses and lichens.
This vegetation is present for most of the growing season in
most years. These wetlands are usually dominated by perennial
plants.
Estuarine Intertidal Scrub
Shrub/Forested
(Estuarine Woody)
Mangroves
Other estuarine
shrub or forest
wetlands
Shrub or forested wetlands in estuarine system dominated by
woody vegetation less than 20 feet (6 meters) tall. The species
include true shrubs, young trees, and trees or shrubs that are
small or stunted because of environmental conditions. Forested
wetlands are characterized by woody vegetation that is 6
meters or taller.
Palustrine Emergent
(Inland Herbaceous)
Inland marshes
Wet meadows
Emergent wetlands in the palustrine* system and characterized
by erect, rooted, herbaceous hydrophytes, excluding mosses
and lichens. This vegetation is present for most of the growing
season in most years. These wetlands are usually dominated by
perennial plants.
Palustrine Scrub Shrub
(Inland Woody)
Palustrine Forested
(Inland Woody)
Shrub wetlands
Shrub wetlands in the palustrine* system and dominated by
woody vegetation less than 20 feet (6 meters) tall. The species
include true shrubs, young trees, and trees or shrubs that are
small or stunted because of environmental conditions.
Forested swamps
Forested wetlands in the palustrine* system and characterized
by woody vegetation that is 6 meters tall or taller.
Palustrine Farmed
(Inland Herbaceous)
Palustrine Unconsolidated
Bottom/Aquatic Bed
(Inland Herbaceous)
Farmed wetland
Farmed wetlands in the palustrine* system and having the soil
surface mechanically or physically altered for production of
crops, but where hydrophytes will become reestablished if
farming is discontinued.
Ponds
Bog lakes
Vernal pools
Kettle ponds
Beaver ponds
Alligator holes
Farm ponds
Recreation ponds
Golf course ponds
Residential lakes
Water retention
ponds
Aquatic beds
Pondweeds
Aquatic beds in the palustrine* system dominated by plants that
grow principally on or below the surface of the water for most
of the growing season in most years. Examples include
pondweeds (Potamogeton spp.), wild celery (Vallisneria
americana), waterweed (Elodeaspp.), and duckweed (Lemna
spp.).
Unconsolidated bottom wetlands in the palustrine* system and
with at least 25% cover of particles smaller than stones, and a
vegetative cover less than 30%. Examples of Unconsolidated
substrates are: sand, mud, organic material, and cobble gravel.
Aquatic bed and Unconsolidated bottom wetlands must also
have the following four characteristics: (1) area less than 20
acres (8 ha); (2) an active wave formed or bedrock shoreline
features are lacking; (3) water depth in the deepest part of a
basin less than 6.6 feet (2 meters) at low water; and (4) salinity
due to ocean derived salts less than 0.5 parts per thousand.
* Due to differences in classifying and mapping wetlands under the Cowardin system, these S&T categories may
include wetlands in shallow riverine and lacustrine systems.
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Chapter 2 | Design of the NWCA
How are the NWCA results presented?
The NWCA reports on wetlands at two scales. The broadest scale is nationwide. Results are also
reported for ecoregions that correspond to major climate and landform patterns, because the patterns
of response to stress, and the stressors themselves, are often better understood in this context.
Ecoregions developed and described by Omernik (1987, USEPA 2011a) are used in this report, as well as
in other NARS studies. Omernik Level III ecoregions across the conterminous US were combined into
nine Aggregated Ecoregions to analyze data and report results in previous NARS studies of wadeable
streams (2004), lakes (2007), and rivers and streams (2008-2009) (see left map in Figure 2-1). Ideally,
NWCA would have used this same set of nine ecoregions to analyze and report results. However,
attempting to evaluate each of the seven NWCA Target Wetland Types within each of the nine
Aggregated Ecoregions would have required sampling nearly three times as many sites to achieve
statistically valid results, which was beyond the logistical capacity of the NWCA. To allow assessment of
condition for distinct wetland types across ecoregions with an acceptable degree of statistical certainty
(i.e., a sufficient number of sampled sites by wetland type), NWCA further combined the nine
Aggregated Ecoregions into four NWCA Aggregated Ecoregions (see right map in Figure 2-1):
• Coastal Plains
• Eastern Mountains and Upper Midwest
• Interior Plains
• West
\
CPL Coastal Plains TPL ; emperate Plains
^^| Northern Appalachians UMW Upper Midwest
NPL Northern Plains WM^ Western Mountains
SAP Southern Appalachians XER Xeric
SPL Southern Plains
CPL Coastal Plains
EMU Eastern Mtn and Upper Midwest
IPL Interior Plains
West
Figure 2-1. Nine Aggregated Ecoregions used in other NARS (map on left) further combined into the four
NWCA Aggregated Ecoregions (map on right).
The seven S&T wetland categories included in the NWCA Target Wetland Types (see Table 2-1) sampled
also had to be combined to allow a sufficient number of sites in each reporting group. This was done by
maintaining the distinction between estuarine and inland wetland types, and within these two groups
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Chapter 2 \ Design of the NWCA
distinguishing wetlands by herbaceous-dominated or woody-dominated vegetation, resulting in four
NWCA Aggregated Wetland Types:
• Estuarine Herbaceous - emergent wetlands
• Estuarine Woody - scrub-shrub and forested wetlands
• Inland Herbaceous - emergent, unconsolidated bottom/aquatic bed, and farmed wetlands not
in crop production
• Inland Woody - forested and scrub-shrub wetlands
Chapter 3 presents the results at the national level and in comparison to the four NWCA Aggregated
Ecoregions. Chapter 4 presents the condition and stressor results for each NWCA Aggregated Ecoregion
and, within each ecoregion, for inland herbaceous and inland woody wetland types. Results for
estuarine herbaceous and woody wetlands are presented nationally. While aggregating wetland types
allows for the reporting of statistically valid national and ecoregional results, differences among unique
wetland types across the conterminous U.S. may be obscured by combining the various wetland types
into the four wetland types used for this NWCA 2011 report.
How were the sampling sites chosen and what do they represent?
NWCA sampling locations were randomly selected using a survey design commonly applied in a
variety of research fields (e.g., ecological assessments, health surveys, election polls, monthly labor
estimates) to determine the status of populations using a representative sample of relatively few
members of the group. This approach is especially cost-effective if the population is so numerous
that all members cannot be sampled, or if it is not necessary to sample the entire population to
reach a desired level of statistical precision.
To identify a group of wetland sites to be sampled in the NWCA, also known as the target
population (i.e., potential sample points), it was necessary to know the location of the NWCA Target
Wetland Types. The NWCA design team used the same digital map of wetland locations as the FWS
S&T Program in their 2005 survey to select wetland sample points and to facilitate comparisons of
the findings from both programs. The S&T Program updates wetland mapping for a fixed set of
statistically selected locations across the conterminous U.S. every five to ten years. While not a
comprehensive map of all wetlands throughout the U.S., these mapped locations are used to
statistically represent the extent of wetlands nationally and, at the time of the survey, was the most
consistent and up-to-date source of digitally mapped wetlands available on a national scale for the
NWCA 2011. Sample points for the NWCA were distributed based on the prevalence of wetlands
across the U.S. and the seven NWCA Target Wetland Types (see Table 2-1). For example, more
sample points were located in regions with greater wetland area.
The 967 sites sampled based on the NWCA design were identified using a technique called
Generalized Random Tessellation Stratified (CRTS) survey design (see NWCA 2011 Technical Report,
Chapter 1 (USEPA 2015)). In such a design, every element in the population has a known probability
of being selected for sampling. This important feature ensures that the results of the survey reflect
the full range of wetlands in the target population across the U.S. Site selection rules were
implemented to provide balance in the number of wetlands from each class. Site selection was also
controlled for spatial distribution to ensure each state received a minimum number of sites, which
also improved the national spatial balance of the sites (see Figure 2-2).
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Chapter 2 | Design of the NWCA
NWCA 2011 Sampled Sites
Alaska Coastal Plain Sites
*T^
**
NWCA Aggregated Ecoregions
CPL Coastal Plains
EMU Eastern Mtn and Upper Midwest
I PL Interior Plains
W West
Figure 2-2. NWCA Sample Sites. The inset shows the sample sites for the study in the North Slope of Alaska described in
a highlight later in this report.
Research teams from EPA and the states screened the points identified for sampling by the survey
design using aerial photo interpretations and Geographic Information System (GIS) analyses to eliminate
locations not suitable for NWCA sampling (e.g., wetlands converted to dry land or upland due to
development). Next, field reconnaissance was conducted to determine if the sites met established
criteria for inclusion in the survey. If a site was eliminated by the screening process or determined in the
field to be a non-target wetland type or inaccessible (e.g., the landowner denied access to the site, the
site was unsafe to access, the site was too remote to access under the logistical constraints of the
survey), it was removed from the sampling effort and systematically replaced with another site from a
pool of replacement sites within the random design.
The treatment of sites eliminated from sampling, as either non-target or inaccessible, affects how
the final population results for the NWCA are estimated and reported. Taking into account the sites
identified, during screening and field reconnaissance, as non-target (e.g., wetlands in active crop
production, deeper water ponds, mudflats, uplands), the NWCA estimated there are 95 million
acres of wetlands in the NWCA target population. The area represented by sites that are part of the
target population, but not sampled because of accessibility issues, is not included for reporting on
assessment of condition and stress. As a result, the final acreage represented by the probability
sites sampled and reported on in the NWCA is 62 million acres. In addition, not all wetland types
included in the FWS S&T studies (estimated wetland area 110 million acres) are included as wetland
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Chapter 2 \ Design of the NWCA
types in the NWCA target population. Table 2-2 provides the distribution of sampled probability
sites and the acres and percent of wetland area they represent within the NWCA ecoregions and
aggregated wetland types.
Table 2-2. Number of probability sites sampled nationally and within each of the NWCA Aggregated Ecoregions and acres of
wetland area these sites represent. Number of sites sampled and the acres represented is also shown for the aggregated
wetland types used in NWCA.
Region
National
Represented Represented
Sampled by Sampled Sampled by Sampled
Sites in Sites, (% of Sites in Sites, (% of
Population Population) NWCA Wet land Type Population Population)
967
62,156,199
(100%)
Estuarine Herbaceous
Estuarine Woody
Inland Herbaceous
Inland Woody
258
69
302
338
4,987,824
497,821
13,599,611
(22%)
43,070,943
(69%)
Coastal Plain
513
30,893,305
(50%)
Estuarine Wetlands
Inland Herbaceous
Inland Woody
288
62
163
5,283,489
(9%)
3,750,551
(6%)
21,859,265
(35%)
Eastern Mtn & Upper Midwest
152
19,956,668
(32%)
Estuarine Wetlands
Inland Herbaceous
\
Inland Woody
14
55
83
29,173
(0.04%)
3,762,089
16,165,406
(26%)
Interior Plains
156
7,659,166
(12%)
Estuarine Wetlands
Inland Herbaceous
Inland Woody
115
41
0
4,598,831
3,060,335
(5%)
West
146
3,647,060
(6%)
Estuarine Wetlands
Inland Herbaceous
Inland Woody
25
70
51
172,985
(0.3%)
1,488,139
1,985,936
(3%)
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Chapter 2 | Design of the NWCA
How were wetlands sampled?
NWCA field work was conducted during the spring and summer of 2011 by more than 50 crews
composed of four or more trained personnel from state and tribal environmental agencies, EPA,
universities, and contract staff. Wetland sites were sampled using standardized field protocols (see
NWCA Field Operations Manual, USEPA 2011a; NWCA Laboratory Operations Manual, USEPA 2011b;
and the NWCA Quality Assurance Project Plan, USEPA 2011c) to collect data relevant to describing the
ecological condition of wetlands and quantifying indicators of stress to condition. Protocols were
designed to allow sampling at each site to typically be completed in one day.
During each site visit, field crews collected ecological data in a standard 0.5-hectare assessment area,
representing the sample point from the survey design, and in the immediately adjacent 100 meters
extending from the assessment area edge, designated as the buffer (Figure 2-3). The crews collected
data on vegetation, soils, hydrology, algae, and water chemistry from the assessment area. In the buffer
crews collected data on habitat and the presence of stressors that could impact the assessment area.
Some sites were not conducive to use of the standard layout shown in Figure 2-3 because of the size and
shape of the wetland (e.g., long and narrow) or because parts of the assessment area contained deep
water, non-target wetland types, or upland. In such cases, the NWCA protocols provided specifications
for alternate assessment area layouts.
The use of standardized field and laboratory protocols is a key feature of the NWCA and all NARS
studies, and allows the data to be combined to produce a nationally consistent assessment. As part of
the quality assurance procedures, each field crew was trained and evaluated on applying the NWCA
protocols by wetland experts. Field checks were conducted at the beginning of the sampling season to
ensure that the protocols were being correctly implemented by the crews, thereby minimizing human
error in data collection. In addition, roughly 10% of the sites were resampled two to four weeks after the
initial visit to a site to evaluate sampling variability.
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:ND
• Sampling Point
Assessment Area
Buffer Area
Vegetation Plot
Soil Pit
Buffer Plot
Figure 2-3. Standard NWCA assessment area and buffer sampling layout
Sampleable Surface
Water (> 15cm deep)
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Highlight
California's Intensification Project: Learning More about California's Wetlands and
Refining Monitoring Techniques
Cara Clark, Moss Landing Marine Laboratories
California has a great diversity of wetlands. Different wetland
types provide different services and support diverse wildlife,
such as water birds, birds of prey, otters, bears, deer, and a
wealth of fish species. California has lost more than 90% of its
historical wetlands and today, many remaining wetlands are
threatened. Wetlands continue to be drained for agriculture,
filled for development, or disturbed by modifications to the
watershed such as dams or water diversions. Climate change
poses a significant threat, as many wetlands today are
dependent on artificial water delivery systems or high
groundwater levels, and may be impacted by changing climatic
conditions. Further, wetlands along the coast face flooding from
potential sea level rise.
Estuarine Wetland Site sampled in China
Camp State Park, San Rafael, CA.
Project Objectives: California's intensification project augmented the 2011 NWCA survey to support two
primary goals. First, California increased the number of sites sampled to produce a statistically valid state-level
assessment of California wetland quality. Second, the data collected for NWCA were used to further validate
the California Rapid Assessment Method (CRAM) - an important tool in California's toolbox for assessing
wetland health - and examine additional associations between CRAM and potential stressors to wetland
quality.
Sampling and Protocols: The 2011
NWCA included 23 sites in California
and California added 22 additional
sites bringing the total to 45. The
additional California intensification
project sites were selected from the
same framework as the NWCA, so that
the two sets of sites could be
combined for analysis and reporting.
NWCA data and protocols were used
at all 45 sites and the state also
conducted the CRAM (Figure 1).
The CRAM is a standardized tool for
wetland monitoring in California,
developed with support from EPA. It is
based on the concept that the
structure of a wetland is indicative of
its capacity to provide important
functions. Four general attributes,
Figure 1. Sampled NWCA sites in California.
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100%
„ 80%
v
5 60%
Depressional
Estuarine
Buffer and Landscape Context, Hydrology, Physical Structure, and Biotic Structure, are assessed visually in the
field. The scores for each attribute are compiled into an overall score, with higher scores relating to better
condition. This project served as a valuable opportunity to further validate CRAM by comparing CRAM scores
to the more intensive parameters in the NWCA including water nutrient concentrations.
What They Have Learned: Although assessment of the information from the California intensification is still
ongoing, staff have begun looking at the site-specific information from the CRAM, including a comparison of
estuarine and depressional wetlands. California's estuarine wetlands are often large, connected salt marsh
systems, in contrast to depressional wetlands which are usually smaller or more fragmented. As a result,
estuarine wetlands have fewer direct landscape stressors putting pressure on them, and so tend to be in
better condition. This is borne out by CRAM results from 2011.
The sites sampled in 2011 indicate that estuarine wetlands tended to have higher CRAM scores (indicating
better condition) than depressional wetlands. The median (50th percentile) CRAM score of depressional
wetlands was 62, whereas the median score for estuarine wetlands was 79 (Figure 2). Additionally,
depressional wetlands tended to have lower scores than estuarine wetlands for all of the attributes included
in CRAM, indicating they are subject to more
stressors.
Other stressors: Excess nutrients in wetlands
often have anthropogenic sources, as
nutrients drain to wetlands from high intensity
land uses, such as agriculture or urban
development. Excess nutrients entering the
wetland can have direct impacts, causing
eutrophication and excess growth of algae,
which leads to hypoxia. When algae die and
decompose, oxygen is depleted from the
water, and the lack of oxygen can kill fish and
other organisms. Researchers found weak, but
statistically significant, correlations between
water nutrient concentrations and CRAM
scores in California's wetlands. Wetlands with
higher nitrate and nitrite concentrations in
surface water samples tended to have lower CRAM scores. The correlation observed between CRAM scores
and nitrate/nitrite concentrations validates that the CRAM score reflects environment factors that can cause
wetland degradation. Higher total phosphorous in surface water was also associated with wetlands having
lower Buffer and Landscape Context scores (one of the CRAM components). Like nitrogen, excess
phosphorous in wetlands is often due to intensive anthropogenic activities in the surrounding area, which is
suggested by the lower Buffer and Landscape Context scores.
What's Next: The California intensification project provided valuable information for state-level wetland
condition, as well as validation for the CRAM tool that is utilized throughout the state. In addition to continued
analysis of this dataset, implementation of the NWCA encouraged the state to develop its own wetland status
and trends program with the goal of augmenting the FWS Status and Trends wetland area mapping
information with consistent and complete state-level wetland maps. While the sites selected for the NWCA
survey were spread across the state, there were clusters of sites in the San Francisco Bay area and the Central
Valley. At the time of NWCA 2011 site selection, California did not have comprehensive or consistently-scaled
wetland maps or a state level wetland mapping program. While this program is still under development, it is
hoped that wetland monitoring and assessment goals will be better met with improved wetland maps for the
state providing a more robust characterization of the entire population of wetlands in California.
To learn more, contact Cara Clark (cclark@mlml.calstate.edu; 831-771-4428), Central Coast Wetlands Group at
Moss Landing Marine Laboratories.
20
40 60
CRAM Index Score
80
100
Figure 2. Cumulative Frequency of CRAM scores for depressional and
estuarine wetlands, based upon unweighted data.
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Chapter 2 | Design of the NWCA
What data were collected and why?
The NWCA collected data to characterize biological, chemical, and physical features of each site.
Vegetation, soil, hydrology, water chemistry, algae, and buffer characteristics were chosen for
evaluation based on their utility in reflecting ecological condition of wetlands or key indicators of stress
that may influence condition across broad national and regional scales (see NWCA 2011 Technical
Report (USEPA 2015)). Data for each of these indicator groups were obtained from field observations
and laboratory analyses of samples collected in the field. Vegetation characteristics were used in the
development of a biological indicator of condition. Data collected on vegetation, soils, hydrology, buffer
characteristics, and algae were used to develop core indicators of stress for the NWCA.
Brief descriptions of key NWCA data that were collected and why each data type is important to the
determination of wetland condition or stress class are provided in the remaining paragraphs of this
section. Additional data, not discussed here, were collected in the NWCA 2011 primarily for research
purposes. For information on these other data, see the NWCA 2011 Field Operations Manual (USEPA
2011a) and the NWCA 2011 Technical Report (USEPA 2015).
Vegetation: The status of natural vegetation has been increasingly and effectively used to evaluate
ecological integrity in wetlands. In wetland ecosystems, vegetation provides biodiversity, primary
productivity, habitat for other organisms, and responds to and influences hydrology, water chemistry,
and physical and chemical properties of soils. Because plants respond directly to physical, chemical, and
biological factors at multiple temporal and spatial scales, they can be excellent indicators of ecological
condition or stress. For example, wetland plant species represent diverse adaptations, ecological
tolerances, and life history strategies, and integrate environmental conditions, species interactions, and
human-caused disturbance. As a result, many human-mediated disturbances are reflected in shifts in
the presence or abundance of particular plant species or in the types of plants occurring at a particular
location. Data describing plant species identity, presence, and abundance were collected in the field for
the NWCA 2011. Information on plant species traits was compiled from a variety of sources including
the PLANTS database (USDA-NRCS 2013), National Wetland Plant List (USAGE 2014), regional and state
floristic databases and floras, state and regional lists of coefficients of conservatism (describing species
sensitivity to disturbance) and other published literature (see NWCA 2011 Technical Report (USEPA
2015) for details). Field and trait data describing vegetation characteristics are powerful and robust, and
can be summarized into myriad candidate metrics or indices of ecological condition. Some plant species
or plant groups also can be indicators of stress to wetlands. Nonnative plant species, in particular, are
recognized as indicators of stress or declining ecological condition, or as direct stressors to condition.
Soils: Wetland soils cycle nutrients, store pollutants, mediate groundwater, are a growth medium for
plants, and provide habitat for microbes and macroinvertebrates (e.g., insects, worms, crayfish, crabs).
Wetland soils develop distinct characteristics as a result of the hydrology and biota (e.g., microbes,
vegetation) associated with wetlands, as well as other factors that affect soil development across all
environments (e.g., climate, geology). These characteristics can be altered by chemical, physical, and
biological stressors, which impacts the ability of the soil to perform functions necessary to healthy
wetlands. Field crews described soil morphology (characteristics such as color, texture, and evidence of
saturation) and collected soil samples to be analyzed for chemical and physical properties to identify
disturbance and indicators of stress. The Natural Resources Conservation Service (NRCS), the federal
agency that provides technical assistance in the management and protection of natural resources
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Chapter 2 \ Design of the NWCA
including soils, worked in partnership with the EPA to provide laboratory analysis for soil samples
collected.
Hydrology: Wetland hydrology is a primary driver of wetland formation and persistence. Hydrology
describes the movement, distribution, and physical and chemical characteristics of surface and
subsurface water. How water moves in or out of a wetland, how long water remains in a wetland, and
how much water is in a wetland impacts many wetland characteristics, including the plant community
composition and productivity, nutrient cycling, and the loss and retention of sediment. Water levels and
patterns of water movement within a wetland can be very dynamic, changing over a period of hours,
days, months, and/or years, making it difficult to assess hydrology with a single site visit (such as in the
NWCA). Field crews collected information about the hydrology of each site by observing the presence or
absence of specific water sources and evidence of alterations to water flow and retention (e.g., drainage
ditches, damming features, evidence of sedimentation or erosion, impervious surfaces).
Water Chemistry: Characterizing water chemistry is an integral part of the assessment of aquatic
resources, because the physical and chemical properties of water directly reflect the surrounding
environment, including anthropogenic influences. However, wetlands differ from lakes, streams, and
coastal waters in that standing water is not necessarily present (Mitsch and Gosselink 2007). At sites
with standing water greater than 15 centimeters deep, water samples were collected and analyzed for a
number of water quality parameters. Field crews also made qualitative assessments of water clarity.
Data were analyzed to investigate relationships between water measurements and natural conditions
and anthropogenic stressors.
Algae: Algae respond quickly to ecological change in wetlands and have been widely used as indicators
of recent changes in wetland condition because of their rapid reproduction rates, short life cycles, broad
distribution, and sensitivity to changes in nutrient levels (McCormick and Cairns Jr. 1994). In addition,
diatom species can provide insights into past hydrology such as recent flooding, standing water, or
droughts (McCormick and Cairns Jr. 1994, USEPA 2002, Lane and Brown 2007). Algae samples from the
water column, sediment, and vegetation were collected from sites with standing water and those
without standing water that had evidence of recent inundation. Samples were analyzed to characterize
the algal communities present at sites and to investigate relationships between certain communities
and ecological condition of wetlands.
Blue-Green Algae: Toxins produced by some blue-green algae species can pose potential human health
risks or limit human recreational use of aquatic resources when they occur above specific
concentrations. Microcystin is the algal toxin believed to be most common in lakes, and it was evaluated
in the NWCA to determine how frequently and at what concentrations, it might occur in wetlands. At
sites with standing water present, a composite sample from the water column, sediment, and
vegetation was collected and analyzed to detect the presence and concentration of microcystin.
Buffer: The presence and condition of the habitat in the area surrounding a site can influence the
ecological condition of the site. For example, natural vegetation cover in the buffer can protect the
wetland by trapping and absorbing incoming sediments, nutrients, and pollutants before they reach the
wetland. The buffer can also reduce wetland disturbance from activities in adjacent areas and mitigate
stressors that may affect wetland condition. In contrast, human-mediated disturbances to the buffer can
be indicators of stress to wetland condition, or may directly cause stress. An example of this would be
surface hardening (e.g., pavement, soil compaction) in the buffer which could alter the hydrology of a
wetland by limiting the natural ability of soils in the buffer (and potentially the wetland) to soak up
stormwater, thus increasing the potential for flooding or erosion to the wetland. Field crews collected
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Chapter 2 | Design of the NWCA
observational data on the presence or absence of a variety of disturbance types within the assessment
area and the wetland or upland area extending 100 meters around the assessment area (termed the
buffer area).
Each of these categories of data collected by NWCA were evaluated to determine their utility in
describing the ecological condition of wetlands or defining indicators of stress to condition at broad
national and regional scales. The specific properties measured and how they were used to evaluate
wetland stress and condition are discussed in the next section.
How were the NWCA core data used to report on ecological condition and
stress?
The raw data from the field and laboratories were combined into a number of metrics and indices to
evaluate NWCA 2011 data for this report. A metric is an individual measure of a particular property for
an individual site, while an index is a combination of metrics used to generate a single score for a
particular site. Indicators of condition or stress can be based on single metrics or on indices. An index of
biological condition based on vegetation was created using plant species data collected at each site and
information on plant traits. Indicators of stress were also developed using biological, chemical, or
physical data collected for the NWCA.
Figure 2-4 illustrates the relationships of the core NWCA data types to the 1) development of indicators
of condition and stress for wetlands, 2) calculation of extent estimates for wetland condition and for
indicators of stress, and 3) calculation of relative and attributable risk associated with each of the
indicators of stress. Core data types are indicated by gray boxes in the figure. The gray arrows represent
analyses leading from these core data types to the development of final indicators of stress or condition
used in NWCA 2011, and also show the sources of data for the NWCA indicators of condition and stress.
Further documentation describing the technical aspects of the analysis process used in NWCA is
available in the NWCA 2011 Technical Report (USEPA 2015).
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Chapter 2 \ Design of the NWCA
Data
Indicator of
Condition
Vegetation Removal
Vegetation Replacement
Damming
Ditching
Hardening
Filling/ Erosion
Soil Heavy Metals
Soil Phosphorus
Algal Toxin Microcystin
Nonnative Plants
Wetland
Condition
Extent
Estimates
Relative &
Attributable
Risk
Figure 2-4. Core data types and relationships to how they are used to develop indicators of condition and
stress. Core data types (gray boxes) and relationships to how they are used to develop indicators of condition (open green
box) and stress (open yellow boxes), and how the indicators are used to determine wetland condition (green box) and stressor
extent (purple box) estimates and relative and attributable risk (teal box).
After appropriate indicators of condition and stress were determined from the data and calculated, each
probability site was assigned to a condition or stressor class, based on the value of the indicator for that
site. For the indicator of biological condition, each site was assigned to a good, fair, or poor condition
class. For the metrics or indices describing the indicators of stress, each site was assigned to a low,
moderate, or high stressor level. The thresholds values used to assign sites to the different condition
classes and stressor levels were defined using either a fixed or distribution based approach.
Fixed thresholds are based on accepted values from peer-reviewed, scientific literature and are well-
established and/or widely and consistently used by government agencies. An example of the latter is the
World Health Organization (WHO) risk levels for recreational exposure to the algal toxin, microcystin.
Fixed thresholds are also sometimes based on the best professional judgment of scientific analysts by
incorporating field and research experience with other knowledge from the collective scientific
community.
Distribution based thresholds are determined using the distribution of values of a particular index or
metric found at a designated set of reference sites. NWCA defines reference as "least-disturbed
condition" and used field data collected from probability sites and additional handpicked sites believed
to be in reference condition to identify a set of reference sites with the least amount of human
disturbance. Data from this set of reference sites is then used to determine the distribution of values for
each indicator of condition or stress. The threshold values for good, fair, and poor condition, or low,
moderate, and high stressor level are set based on defined percentiles from the distribution of values
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Chapter 2 | Design of the NWCA
observed in the least disturbed sites (see text box below on "Use of Reference Site Approach" and
NWCA 2011 Technical Report (USEPA 2015)).
The good, fair, and poor condition classes and the low, moderate, and high stressor levels reported by
NWCA have no regulatory implications and are not replacements for the evaluation of the quality of
wetlands with respect to water quality standards set by states and tribes.
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Chapter 2 \ Design of the NWCA
USE OF REFERENCE SITE APPROACH
To interpret the data collected by the NWCA field crews and to assess current ecological condition, scientists
need to compare the collected data to benchmarks — an estimate of what scientists would expect to find in
wetlands with the best natural condition. Because it is difficult to estimate historical conditions for many
indicators, the NWCA's benchmark, or reference, is characterized as the "least-disturbed condition": the best
available physical, chemical, and biological conditions given today's state of the landscape. Least disturbed
condition is defined based on data from sites selected according to a set of explicit screening criteria. These
criteria vary from region to region and among wetland types to account for differences in natural variability
and anthropogenic disturbance across the American landscape*. For the NWCA, separate screening criteria
I were defined based on combinations of the NWCA Aggregated Ecoregions and Aggregated Wetland Types. The
screening criteria were developed with the goal of identifying reference sites with the least amount of human
disturbance for each reporting group (e.g., estuarine herbaceous wetlands, Interior Plains inland woody
wetlands). Reference criteria, in essence, allow identification of the set of sites with the least-disturbed
condition across the target population of wetlands.
The NWCA compares specific physical, chemical, and biological stressor data collected at each site to the
reference site screening criteria to determine whether any given site meets the definition of least disturbed
condition for its combined Aggregate Ecoregion/Wetland Type. The group of sites passing all the screening
criteria are considered to be in reference condition. Good ecological condition and low stressor levels are
characteristic of reference sites. These reference sites are then used to set thresholds against which the
broader population of wetlands can be compared and assigned to condition or stressor classes. The range of
conditions found in the group of reference sites for an ecoregion describes a distribution of values expected
for least-disturbed condition or stress. The thresholds used to define distinct condition classes (e.g., good, fair,
poor) or stressor levels (e.g., low, moderate, high) are drawn from this reference condition distribution. The 5th
percentile of the reference distribution was used to separate the sites in poor biological condition from those
in fair. Similarly, the 25th percentile of the reference distribution was used to distinguish between sites in fair
biological condition from those assessed in good condition. For stressor classes, the 95th percentile of the
reference distribution was used to separate the sites considered to have high stress from soil phosphorus
concentrations from those with moderate, and the 75th percentile was used to separate the moderate and low
stressor classes.
This approach for establishing reference condition is well documented and consistent with current science,
EPA guidelines, state practice, and established protocols for ecological assessment (Bailey et al. 2004; Barbour
et al. 1999; Carter and Resh, 2013; Hughes, 1995; Reynoldson et al. 1997; Stoddard et al. 2006; and USEPA,
2011d).
*Within the reference site distribution, there are two sources of variability:
Natural variability includes a wide range of habitat types naturally found within each ecoregion. This range is
captured in the reference sites representing those different habitats. For this reason, reference condition
thresholds were set based on the distribution of least disturbed sites, rather than from a single site. Capturing
natural variability in reference sites helps establish reference conditions that represent the range of natural
environments in the ecoregions.
Human activities have altered habitats in the U.S., with natural landscapes transformed by cities, suburban
and rural development, agricultural development, and resource extraction. The extent of those disturbances
varies across regions. Some reference sites are in watersheds with little to no evidence of human impact, such
as mountain streams or rivers in areas with very low population densities. Others have been highly influenced
by human activities. The least-disturbed reference sites in regions with more human activity will usually have
lower screening criteria than those in areas with little human disturbance.
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Chapter 2 | Design of the NWCA
Evaluating Wetland Biological Condition
Vegetation is a fundamental component of wetlands. The composition and abundance of plant species
at a site reflect and influence other ecological processes related to hydrology, water chemistry, and soil
properties. Vegetation integrates different wetland processes and plants respond to physical, chemical,
and biological disturbances. These properties make vegetation a particularly good indicator of wetland
condition. Using field data describing species composition and abundance in combination with species
trait information, numerous candidate metrics were developed and evaluated as potential components
of a Vegetation Multimetric Index (VMMI). A national-scale VMMI was then developed as the indicator
of biological condition for the NWCA.
The VMMI is called a multimetric index because it combines more than one metric. After careful
screening of many candidate metrics, four were chosen for inclusion in the VMMI:
• A Floristic Quality Assessment Index (FQAI),
• Relative Importance of Native Plant Species,
• Number of Plant Species Tolerant to Disturbance, and
• Relative Cover of Native Monocot Species.
Each metric in the VMMI is based on combinations of data types describing species composition
(identity and/or abundance) and species traits. These metrics were chosen because they 1) best reflect
ecological condition of wetlands across the conterminous U.S. for the different NWCA Aggregated
Ecoregions and NWCA Aggregated Wetland Types, 2) detect differences between the least and most-
disturbed sites, and 3) were not strongly related to one another (see NWCA 2011 Technical Report
(USEPA 2015)). Each metric is scored from 0 to 10 for consistency in scaling the metric value ranges.
VMMI values are scaled from 0 to 100.
The FQAI is often considered as a standalone index for describing floristic quality, but is used here as
one metric contributing to the VMMI. It captures information about plant community composition
based upon all unique plant species occurring at a given site and a value given to each plant species
based on its sensitivity to human-mediated disturbance. This value is known as the Coefficient of
Conservatism or C-value. C-values range from 0 to 10 where a value of 0 is assigned to plant species that
occur in highly disturbed habitats and a score of 10 is assigned to species found only in minimally
disturbed habitats. C-values may vary by state or region to account for natural differences in habitat and
plant community composition. C-values were compiled from existing state and regional lists of values,
or, for states and regions where lists did not exist, by assigning values based on those of ecologically
similar neighboring states or regions.
The second metric in the VMMI is the Relative Importance of Native Plant Species. Relative importance
combines information on how much of the sampling location is covered by native wetland plants in
relation to all plants present (e.g., relative cover) and how many occurrences of native plant species
there are across a site compared to the number of all plant species occurrences (i.e., relative frequency).
Native status of a given species-site occurrence was based on whether the species was indigenous to the
state in which the sample site was located. As disturbance at a site increases, the native plant
community is often altered—a change that is often related to declining condition.
The Number of Plant Species Tolerant to Disturbance is the third metric in the VMMI. The number of
tolerant species increases with increasing disturbance, indicating a potential shift in plant community
dynamics. Such a shift could reflect competitive pressure or other stress to disturbance-intolerant
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Chapter 2 \ Design of the NWCA
species that are often indicative of good ecological condition. C-values are used to describe sensitivity or
tolerance of plant species to disturbance. Tolerance can be indicated by the presence or abundance of
plant species with low C-values. Species tolerant to disturbance are defined in NWCA as those with a C-
value of 4 or less.
Finally, the fourth metric in the VMMI is the Relative Cover of Native Monocot Species. Monocots are
one of two groups into which flowering plants are divided. They are common to many wetland types,
and are represented by plants like grasses, sedges, rushes, lilies, irises, orchids, etc. Native monocots
represent dominant natural components of many emergent (non-woody) wetland types. In other
wetland types, they may reflect species that are indicative of relatively undisturbed conditions.
The final VMMI score is calculated based on the combination of values for all four metrics for each site,
with the overall value indicating the level of biological condition. Good, fair, or poor condition
thresholds were set using a distribution-based approach based on the VMMI values for reference sites
(see "Use of Reference Sites" text box) in each combination of NWCA Aggregated Ecoregion by NWCA
Aggregated Wetland Type. The 5th percentile of the reference distribution for each NWCA Aggregated
Ecoregion and NWCA Aggregated Wetland Type combination was used to separate the sites in poor
condition from those in fair condition. Similarly, the 25th percentile of the reference distribution was
used to distinguish between sites in fair condition and those assessed as being in good condition (Figure
2-5). Specific threshold values for each NWCA Aggregated Ecoregion and NWCA Aggregated Wetland
Type combination are provided in the NWCA 2011 Technical Report (USEPA 2015).
100
Least Disturbed (Reference)
Site Distribution
Figure 2-5. Criteria for setting VMMI thresholds for good, fair, and poor condition classes based on VMMI
values observed for Least Disturbed (Reference) sites.
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Wisconsin's Intensification Study: A Floristic Characterization of Wetlands in Eastern
Wisconsin
Thomas Bernthal, Wisconsin Department of Natural Resources
Overview: Plant community composition can provide a detailed picture of wetland health, and the
differences between a pristine and a degraded habitat may be partially characterized by looking at the
presence and abundance of plant species. The main objective of the Wisconsin intensification study was
to compare the Floristic Quality Index (FQI)
currently used with an adjusted index to
determine if it may be a better predictor of
wetland ecosystem health.
Main Story: The Wisconsin Department of
Natural Resources (DNR) chose to do a more
intensive study of wetlands in the Lake
Michigan basin of Eastern Wisconsin. As part
of the 2011 NWCA, 34 unique sites were
sampled in Wisconsin, 12 of which were in
the Lake Michigan basin. An additional 38
sites were sampled in 2012 for the
intensification project, for a total of 50 sites in
the project area (Figure 1).
Using vegetation data collected at each site,
the Wisconsin DNR employed a Floristic
Quality Assessment (FQA) framework to
examine wetland health. The FQA uses
species richness or the number of different
species present (N) and the Coefficient of
Conservatism (C) to calculate the Floristic
Quality Index (FQI). The C is an assigned
number between 0 and 10 for each plant
species, which reflects the response to
disturbance. A species that is considered
tolerant of disturbance is assigned a lower C value. Conversely, a species that disappears from a
community following a disturbance is given a higher C value. Invasive species are assigned a C value of 0.
A plant community with a high species count scores well on a FQI. In some habitats this high FQI score
may not be indicative of healthy natural conditions, as excess nutrients like phosphorous and nitrogen
can stimulate excessive plant growth and increase the number of plant species leading to an impaired
community. Though these nutrients are basic building blocks of plants and are needed in a wetland plant
community, in high concentrations these nutrients can degrade wetlands.
A
Survey Sites
c Intensification Sites
• Original NWCA Sites
| ] Project Area
0 5 10 20 30 40
Figure 1. Intensification study project area in eastern
Wisconsin.
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To counter the inflating effects of species richness on the FQI, the Wisconsin DNR employed a weighted
mean Coefficient of Conservatism metric (wC}. This weighted metric accounts for species abundance,
which may allow for a better picture of the composition of a plant community.
What They Found: The main objective of the study was to compare C and wC to determine which
method would give a more accurate assessment of wetland ecological condition when incorporated into
the FQI. Figure 2 shows comparison boxplots of the calculated C and wC for the wetland community
types sampled in the intensification study, including Palustrine Emergent (PEM), Palustrine Forested
(PFO) and Palustrine Shrub/Scrub (PSS). The PEM showed the greatest difference between C and wC.
Among the other community types (PFO and PSS), where sampled wetlands were not dominated by
invasive graminoid (i.e., grass or grass-like plant) species as often, the differences between C and wC
were less pronounced.
Wisconsin found that lower wC values were correlated with an increase in the relative cover of invasive
graminoids, (R2=0.754), including reed canary grass (Phalaris arundinacea), hybrid cattail (Typha x
glauca), narrow-leaf cattail (Typha angustifolia), and common reed (Phragmites australis). They found
that the wC metric was especially useful for capturing differences between sites with sparse invasive
plant populations and sites overrun by invasive species. More PEM sites were dominated by invasive
reed canary grass or hybrid cattail stands than in the other community types, which could explain the
difference between C and wC for the PEM wetlands, as noted in Figure 2.
Although wC is a useful way to describe some wetland plant communities in Wisconsin, it may not be the
best metric for all communities. The conventional methods of calculating the FQI using C may be better
suited for communities that are characteristically more species-rich, such as cedar swamps. Communities
that tend to be naturally species-poor, such as bogs or muskegs, may be better characterized by using
the wC. The conventional FQI used by Wisconsin currently and the adjusted index using wC were found
to be valuable metrics to describe the vegetation condition in wetlands. Scientists and wetland managers
may use the plant community attribute information gained in this intensification study in order to better
evaluate Wisconsin's wetlands based on vegetation condition.
To learn more, contact Thomas Bernthal (Thomas.Bernthal@wisconsin.gov), Wisconsin Department of
Natural Resources.
Mean C vs Weignled Mean C by Status and Trends Community Type
I
"
i
C
'~-
PSSlH»nC
PEM ,'. *ij>- :*= M*I - C
n C
n C
vluMrtnt Enwpvtt (FEIuq
PBluMrtnt SNuMovb Q
Figure 2. Comparison of Cand wC by Status and Trends cornm unity type.
National Wetland Condition Assessment 2011
October 2015
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Chapter 2 | Design of the NWCA
Evaluating Indicators of Stress
Indicators of stress are physical, chemical, or biological factors that have the potential to reflect
anthropogenic impacts on wetland ecological condition. Indicators of stress do not necessarily directly
cause ecological decline, but are often associated with changes in wetland condition. NWCA evaluated
the extensive set of data collected in the field to identify and develop appropriate indicators of stress
and quantify their national and regional extents. While these are expected to be associated with effects
on wetland condition, the exact relationship cannot be explicitly determined from the data collected in
NWCA. For simplicity of language, in this report "indicators of stress" are also referred to as "stressors."
It was not possible to evaluate all potential stressors affecting wetland condition. NWCA 2011 indicators
of stress are derived from field data collected at the site-level within the assessment area and the 100
meter buffer immediately surrounding it. Due to this, potential effects on condition from stressors
occurring outside of the vicinity of the assessment area and buffer may not be fully considered in the
NWCA reported results and could have significant influences on wetland condition.
Six physical, three chemical, and one biological indicator of stress were developed for the NWCA report.
The following sub-sections summarize the development of the indicators pertaining to each of these
three categories.
Physical Indicators of Stress
Wetlands can be impacted by human-mediated activities that cause physical changes to wetland
systems. These may be stressors that are occurring in the wetland itself or many miles away. Due to the
limitations of the survey, NWCA 2011 focused on physical stressors occurring in the assessment area
and in the area immediately surrounding the assessment area (i.e., buffer). Physical indicators of stress
include vegetation alterations that occur through removal or replacement, or hydrologic alterations that
occur through damming, ditching, surface hardening, filling or erosion. These alterations can disrupt
wetland structure and function. Data reflecting indicators of physical stress were evaluated as part of
the hydrology and buffer protocols both within the wetland assessment area and the 100 meter buffer
immediately surrounding it. The indicators evaluated were placed into different stress indicator groups
based on whether they resulted primarily in vegetative or hydrologic alteration to a wetland.
Vegetation alteration included two indicators of stress:
• Vegetation Removal - any field observation related to loss, removal, or damage of vegetation
(e.g., mowing/shrub cutting, herbicide use, highly grazed grasses, recently burned forest); and
• Vegetation Replacement - any field observation of a change in the plant species present due to
anthropogenic activities (e.g., tree plantation, nursery, golf course, lawn/park, row crops,
pasture/hay, rangeland).
Changes in vegetation at the sampling site and the surrounding area can indicate effects of activities
that could impact the ecological condition of the wetland. Removal of vegetation may increase
sediment, nutrient, and pollutant loads entering or residing in a wetland. Replacement reflects
conversion from one vegetation type to another in the buffer and assessment area and can decrease
biodiversity, simplify the vertical structure, and reduce habitat quality on the site. Not all instances of
vegetation removal or replacement (e.g., moderate grazing by native wildlife, natural wildfire regimes in
ecosystems adapted to fire) result in stress to a wetland or poor ecological condition. The relationship
between vegetation alteration stressors and biological condition as indicated by the VMMI are
evaluated through the concepts of relative and attributable risk later in the report.
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Hydrologic alteration included four indicators of stress:
• Damming - any field observation related to impounding or impeding water flow from or within
the site (e.g., dikes, dams, berms, railroad beds);
• Ditching - any field observation related to draining water within the site (e.g., ditches,
corrugated pipe, excavation-dredging);
• Hardening - any field observation related to soil compaction, including activities and
infrastructure that primarily result in soil hardening (e.g., parking lots, suburban residential
development, roads, pavement); and
• Filling/Erosion - any field observation related to soil erosion or deposition (e.g., soil loss/root
exposure, fill/spoil banks, freshly deposited sediment).
Changes in how water moves in or out of a wetland, or water levels within the wetland resulting from
hydrologic alterations can affect plant productivity, nutrient cycling in the soil and water, and the
physical habitat, thereby impacting the overall ecological condition of the wetland. For example, a
nearby parking lot or impervious surface could increase the volume of water entering the wetland.
Higher water tables may limit the plant species that can grow in the wetland.
Stress-level thresholds were established for each stressor group (vegetation alteration and hydrologic
alteration) and applied to each individual indicator of stress (see NWCA 2011 Technical Report (USEPA
2015)). Thresholds reflecting low stress were set to indicate the complete absence of the given physical
indicator of stress at the site. Thresholds reflecting high stress were set using best professional
judgment. Indicator values between the established low and high threshold levels were placed into the
moderate stress class. These thresholds were used across all NWCA sites (See Table 2-6 for a complete
list of indicators and summary information on how thresholds were set).
Chemical Indicators of Stress
Chemical stressors that can impact the ecological condition of wetlands include excess nutrients, metals,
organic toxins, and other chemical compounds that can disrupt nutrient cycles, affect plant and animal
growth, and be detrimental to human health. Two chemical indicators of stress were developed for
NWCA using data from soil samples collected at each site: a Heavy Metal Index and soil phosphorus
concentration. Another potential indicator of stress, microcystin (an algal toxin), was evaluated based on
concentrations from a composite sample of surface water and algal scrapings from vegetation stems and
leaves.
The Heavy Metal Index, developed for the NWCA as a chemical indicator of stress, was comprised of 12
different heavy metals closely associated with anthropogenic activities: antimony (Sb), cadmium (Cd),
chromium (Cr), cobalt (Co), copper (Cu), lead (Pb), nickel (Ni), silver (Ag), tin (Sn), tungsten (W),
vanadium (V), and zinc (Zn). Stress-level thresholds were set for each metal using published estimates of
natural background concentrations and best professional judgment (Table 2-3). It should be noted that
the thresholds established for heavy metals do not reflect toxicity; rather, they are indicators of human
disturbance. Sites where all 12 metal concentrations were equal to or below the stress-level threshold
established for each metal were placed into the low stress-level class. Sites where three or more metal
concentrations were above the stress-level thresholds were placed into the high stress class. Sites not
placed into either the low or high stress-level classes were put into the moderate stress class. The same
thresholds were used across all NWCA sites.
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Chapter 2 | Design of the NWCA
Table 2-3. Heavy metals included in the Heavy Metal Index as a chemical indicator of stress. Natural background
concentrations are based on Alloway (2013). Thresholds were set based on natural background concentration and best
professional judgment.
Silver (Ag)
Cadmium (Cd)
Cobalt (Co)
Chromium (Cr)
Copper (Cu)
Nickel (Ni)
Lead (Pb)
Antimony (Sb)
Tin (Sn)
Vanadium (V)
Tungsten (W)
Zinc(Zn)
bDirebb- Level
nary Anthropogenic Natural Background Threshold
Association Concentration (mg/kg) (mg/kg)
Industry
Agriculture
Industry
Industry
Agriculture / Industry / Roads
Industry /Agriculture
Roads/ Industry
Industry
Industry / Agriculture
Industry/ Roads
Industry /Agriculture
Industry /Agriculture
0.05 - 1.00
0.1-1.0
<50
0.5-250
2-50
0.2-450
Mean of 18
0.1-1.9
1.7-50
36 - 150
<2
10 - 150
1.0
1.0
25
125
50
225
35
1.0
17
150
2.0
150
Soil phosphorus concentrations were measured from samples collected at each site. Naturally-occurring
soil phosphorus concentrations vary widely across wetlands due to differences in soil types, wetland
types, climate, and other factors. Soil phosphorus concentration can also be influenced by and reflect
human activity on the landscape. No nationally-accepted soil phosphorus criteria exist to assign stress
classes. Therefore, NWCA used a distribution-based, or reference site approach, paralleling that of the
VMMI, to set soil phosphorus concentration stress classes for each combination of NWCA Aggregated
Ecoregion by NWCA Aggregated Wetland Type (see "Use of Reference Site Approach" text box). Soil
phosphorus concentrations above the 95th percentile of reference sites were considered to have high
stress, while those below the 75th percentile of reference sites were considered to have low stress
(Table 2-4, see NWCA 2011 Technical Report (USEPA 2015) for further details).
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Table 2-4. Soil phosphorus concentration thresholds as chemical indicators of stress. Stress-level thresholds were set for
estuarine wetland types nationally and for inland wetland types by NWCA Aggregated Ecoregion based on the 75th percentile
(low stress) and 95th percentile (high stress) of reference sites for the group.
.
NWCA Reporting Group
(NWCA Aggregated Ecoregion, Wetland Type)
Estuarine (Herbaceous and Woody)
Coastal Plains (Inland Herbaceous and Woody)
Eastern Mountain and Upper Midwest (Inland
Herbaceous and Woody)
Interior Plains (Inland Herbaceous and Woody)
West (Inland Herbaceous and Woody)
LOW inresnoia
(mg P/kg soil)
<519
<582
<914
< 1,110
< 1,140
High i n res no id
>969
> 1,180
> 1,280
> 1,810
> 2,090
Microcystin is a toxic substance produced by cyanobacteria, a group of microbes also called blue-green
algae. Cyanobacteria are a natural part of aquatic ecosystems, but under certain environmental
conditions, can proliferate into algal blooms that can be unsightly, smelly, and in some instances cause
severe health issues for wildlife, people, and domestic animals.
EPA collected samples and tested them for the presence and concentration of microcystin. The results
are categorized using a fixed threshold approach based on recreational exposure guidelines established
by the World Health Organization (Table 2-5). Concentrations of microcystin have not been previously
documented over a spatial area or for as many wetland types as sampled in the NWCA, consequently,
more research is likely to be needed to appropriately interpret how these results relate to wetland
condition.
Table 2-5. World Health Organization thresholds of risk associated with exposure to microcystin.
Indicator (units)
Microcystin (ug/L)
Low Risk of Exposure
<10
Moderate Risk of
Exposure
10 - < 20
High Risk of
Exposure
>20
Biological Indicators of Stress
EPA used the presence and abundance of nonnative plants to develop a biological indicator of stress.
Nonnative plants are often related to human-mediated disturbance, and can also be direct or indirect
stressors to wetland ecosystems by competing with or displacing native plant species or communities, or
by altering wetland structure and processes.
The Nonnative Plant Stressor Indicator (NPSI) was developed for the NWCA using collected plant data
and information describing the native status of each species (see NWCA 2011 Technical Report (USEPA
2015) for definition of nonnative plant concepts). The NPSI included three complementary nonnative
species metrics that describe different avenues of potential impact to ecological condition:
• Relative Cover of Nonnative Species
• Richness of Nonnative Species (number of unique nonnative species)
• Relative Frequency of Occurrence of Nonnative Species
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Chapter 2 | Design of the NWCA
Relative Nonnative Cover reflects preemption of space and resources, changes in species composition,
and alteration of ecosystem processes. Higher values are often associated with decreases in ecological
condition. Total Richness of Nonnative Species can be an indicator of potential risk for ecological
impact; greater numbers of individual nonnative plant species increases risk that one or more may be or
become invasive or cause ecosystem alterations. Greater Relative Frequency of Occurrence of
Nonnative Species reflects increasing numbers of locations for further nonnative incursions and a
decreasing proportion of the species composition that is native.
These three metrics are used together to assign low, moderate, high, and very high stress levels for the
NPSI. Stress-level thresholds were set for each metric in the NPSI using best professional judgment. The
addition of a "very high" stressor class was made because of the greater range in values for this stressor
indicator compared to other stressor indicators. The same threshold values were used across all NWCA
sites (see NWCA 2011 Technical Report (USEPA 2015) for details on NPSI development and application).
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Chapter 2 \ Design of the NWCA
Table 2-6. Summary of NWCA 2011 indicators of condition and stress and information on how thresholds were set.
Indicator Reference Approach General Assessment Notes
Biological Condition
Vegetation MMI
Indicators of Stress
Regionally specific
(NWCA ecoregion /
wetland type)
distribution-based
threshold
Data on specific plants and abundance collected from five plots
systematically distributed in assessment area. Index developed based
on species composition (presence and abundance) and species traits.
Physical -Vegetation Alteration:
Vegetation Removal
Vegetation
Replacement
Nationally consistent
fixed threshold
Field observations related to loss, removal, or damage of vegetation
(e.g., mowing /shrub cutting, herbicide use, highly grazed grasses,
recently burned forest) collected from plots systematically distributed
in assessment area and 100 meter buffer area.
Field observations of a change in the plant species present due to
anthropogenic activities (e.g., tree plantation, golf course, lawn/park,
row crops, pasture/hay, rangeland) collected from plots systematically
distributed in assessment area and 100 meter buffer area.
Physical - Hydrologic Alteration:
Damming
Ditching
Hardening
Filling/Erosion
Chemical:
Heavy Metal Index
Soil Phosphorus
Microcystin
Biological:
Nonnative Plant
Stressor Index
Nationally consistent
fixed threshold
Nationally consistent
fixed threshold
Regionally specific
(NWCA ecoregion)
distribution-based
threshold
Nationally consistent
fixed threshold
Nationally consistent
fixed threshold
Field observations related to impounding or impeding water flow (e.g.,
dikes, dams, berms, railroad beds) collected in the assessment area and
from plots systematically distributed in the 100 meter buffer area.
Field observations related to draining water within the site (e.g.,
ditches, corrugated pipe, excavation-dredging) collected in the
assessment area and from plots systematically distributed in the 100
meter buffer area.
Field observations related to soil compaction, including activities and
infrastructure that primarily result in soil hardening (e.g., roads,
suburban residential development, pavement) collected in the
assessment area and from plots systematically distributed in the 100
meter buffer area.
Field observations related to soil erosion or deposition (e.g., soil
loss/root exposure, fill/spoil banks, freshly deposited sediment)
collected in the assessment area and from plots systematically
distributed in the 100 meter buffer area.
Samples collected from upper 10 centimeter of soil in the assessment
area. Measured concentrations compared to thresholds based on
background concentrations of heavy metals.
Samples collected from upper 10 centimeter of soil in the assessment
area. Measured concentrations compared to thresholds based on
reference sites.
Samples collected from surface water, sediment, and vegetation
surfaces. Measured concentrations compared to World Health
Organization (WHO) algal toxin threshold for recreation.
Data on specific plants and abundance collected from five plots
systematically distributed in assessment area. Index developed based
on species composition (presence and abundance) and species traits.
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Chapter 2 | Design of the NWCA
Estimating the extent of wetland area for condition classes or stress-level
classes
The NWCA 2011 results presented in the subsequent chapters of the report are calculated by estimating
the extent of wetland area in each of the different condition classes or stressor levels established for
each indicator. The process used to accomplish this is briefly described below for the NWCA indicators
of condition and stress. More detailed information is provided in the NWCA 2011 Technical Report
(USEPA2015).
Condition: There are three different classes to describe wetland condition: good, fair, and poor. The
VMMI thresholds for each condition class are used with site weights to calculate extent estimates of
wetland area in good, fair, and poor condition using a two-step process:
1) Each NWCA probability site is assigned good, fair, or poor biological condition based on its
VMMI value and the thresholds appropriate to the site.
2) Next, the site weights from the probability design, which reflect the number of acres each site
represents across the total population of NWCA Target Wetland Types, are summed within
condition class to estimate the wetland area in good, fair, and poor condition.
In Figure 2-4, this process is illustrated by the arrows between the Vegetation Data, VMMI, and Wetland
Condition Extent Estimate boxes. The survey design also allows evaluation of the statistical certainty of
these condition estimates.
Stress: For each stress indicator, its designated threshold values are used to assign a low, moderate, or
high stress level to each site. An additional stress-level of very high was designated for the Nonnative
Plant Stressor Index. The process for estimating the extent of wetland area with low, moderate, high, or
very high stress for each of the NWCA indicators of stress, parallels the approach used for making
condition estimates. In Figure 2-4, this process is illustrated by the arrow between each group of
indicators of stress and the Stressor Extent Estimate box.
Other data collected as part of NWCA 2011 but not reported in national and
regional results
Water Chemistry
The NWCA 2011 survey is the first national-scale survey of wetland surface water chemistry. Water
chemistry data were collected for chlorophyll-a, conductivity, ammonia, nitrate-nitrite, total nitrogen,
total phosphorus, and pH. Water temperature and dissolved oxygen levels also were measured at some
sites at the option of the states involved. The objectives of the NWCA water chemistry data analyses
were to examine the extent to which water chemistry could be sampled and evaluated across different
wetland types, to explore any patterns found in water chemistry for wetlands across the nation and
relate them to possible classification variables and natural and anthropogenic drivers, and to generate
recommendations concerning further research and protocols for future NWCA assessments.
Water chemistry samples could only be collected from approximately 55% of the sites sampled in NWCA
2011 due to a lack of sufficiently deep standing water at the sampling site. This confounded efforts to
assess and report results for the water chemistry data using the analytic approaches adopted by NWCA
2011 for its core data indicators. For this reason, water chemistry results are not presented in the NWCA
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Chapter 2 \ Design of the NWCA
2011 report. Analysis and interpretation of the data collected is discussed in the NWCA 2011 Technical
Report (USEPA 2015) and, as opportunities arise, will be further disseminated through scientific journals.
Algae Species Data
NWCA 2011 collected composite algae samples from the water column, sediment, and vegetation
surfaces at sites with standing water greater than 15 centimeters deep and sites that had evidence of
recent inundation. Samples were analyzed to characterize the algal communities present at sites and to
investigate relationships between certain communities and ecological condition of wetlands. Though
algae taxonomic data were obtained from approximately 80% of the sites sampled in NWCA 2011, issues
with data consistency arising from sample collection in the field and taxonomic identification in the lab
raised questions about the efficacy of evaluating wetland condition using this algae species data for the
NWCA 2011 report.
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Nebraska's Intensification Project: Impacts of Land Use and Management on Wetland Condition
Ted LaGrange, Nebraska Game and Parks Commission
Overview and Goals: Through the intensification project, participating state, federal, and regional agencies
wanted to learn more about 11 priority landscape regions in the state of Nebraska. Most of these regions have
been identified in the state's Wildlife Action Plan as Biologically Unique Landscapes, and the information
gained from the project will help direct conservation and management efforts in these key landscapes found
in Nebraska and throughout the Great Plains.
Since settlement, Nebraska has lost an estimated 35% of its total wetland area due to land-use conversion,
and 97% of the remaining wetlands occur on private lands. In the Rainwater Basins (an important region
within the Central Flyway as a major bird migration route in North America), wetland losses may be as high as
90%. In order to obtain more data on these important and diverse wetland habitats, an intensified sampling
effort was conducted in 11 wetland complexes in Nebraska. This included isolated playa wetlands in
landscapes dominated by row-crop agriculture in the Rainwater Basin, Central Table Playas, and Southwest
Playas; wet meadows and freshwater and alkaline marshes in the Nebraska Sandhills (includes the Elkhorn
River Headwaters, Cherry County Sandhills Wetland, and Sandhills Alkaline Lake regions); wet meadows and
alkaline wet meadows located along the North Platte (Western Alkaline), Platte (Central Platte), and Niobrara
Rivers; Eastern Saline wetlands located near Lincoln, NE; and forested wetlands along the lower Missouri River
(Figure 1).
Information Collected: 109 sampling locations were visited across the 11 regions during the growing seasons
of 2011-2013. At each site, Level 1, 2, and 3 assessment data were collected using the 2011 NWCA protocols.
Figure 1. Priority landscape regions identified for the intensification project.
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As part of the study, the team developed the Nebraska Wetland Rapid Assessment Method (NeW_RAM),
which was tested at 40 of the sites in 2013 and compared to Level 3 assessments. Additionally, amphibian
community surveys were conducted at 125 sites in the Rainwater Basin complex with the goal of developing a
sampling protocol for long-term amphibian community monitoring and to assess how wetland management
practices might affect the presence and health of frog and toad species. Wetlands surveyed for amphibians
were grouped according to land use: Wildlife Management Areas (WMA), Waterfowl Production Areas (WPA),
Wetlands Reserve Program (WRP), privately owned wetlands, and agricultural reuse pits.
What They Have Learned: Sample processing and data analysis is still underway, but preliminary results have
already provided useful information about wetland condition across landscape regions in Nebraska. The draft
NeW_RAM, developed in early 2013, was used at 40 sites sampled in 2013. Overall, the NeW_RAM worked
well in the field and showed good agreement with level 3 measurements, including the FQAI. It is hoped the
NeW_RAM will be a useful tool for agencies and organizations to quickly assess wetland condition, improving
Nebraska wetland protection and restoration efforts.
Differences in wetland vegetation condition, measured by the FQAI, varied among landscape regions and with
respect to reference condition within each region (Figure 2). Given the high diversity of Nebraska's wetlands,
reference wetland FQAI scores may be very different in each of the regions, and direct comparisons of FQAI
scores between regions may not be
appropriate.
Within each region, high and low FQAI
scores with respect to reference condition
may be linked to land use. In regions
where sites scored well below reference,
high quality sites may no longer exist on
the landscape due to historical and
contemporary land use change or
disturbance. Two of the lowest scoring
regions, the Southwest Playas (SWP) and
Central Table Playas (CTP), included
shallow playa wetlands in areas
dominated by intensive agriculture and
recently affected by a period of extreme
drought. Low scores were also observed
in wetlands along the lower Missouri
River (MR), which had been highly altered
during historic flooding in 2011. Slightly
higher FQAI scores (although still below
reference condition) were documented in
the Western Alkaline (NPR) and Eastern Saline (SAL) regions, both areas that have been altered, but where
some restoration efforts have occurred. The Central Platte (CP), Sandhills Alkaline Lakes (SALK), Rainwater
Basin (RWB), Niobrara River (NR), Cherry County Sandhills Wetlands
(CCWM), and Elkhorn River Headwaters (EHW) regions have large areas
of unmodified land or have been the focus of intensive management
and conservation efforts. FQAI scores in these regions tended to be
closer to the reference standard, evidence that current management
practices are effective in maintaining and restoring wetland condition.
This project is providing baseline data of wetland condition within these
regions of Nebraska, and offers insight towards the direction of future
conservation efforts within the state.
SWP CTP MR NPR SAL CP SALK RWB NR CCWM EHW
Figure 2. Floristic Quality Assessment Index (FQAI) scores for each of the
wetland complexes studied. The top and bottom of the boxes show the
75th and 25th percentile of scores and the line inside the box represents
the median score for each region. Reference standard condition FQAI
scores for each landscape region are shown as red dots.
Seven species of frogs and toads were observed at wetlands sampled in
the Rainwater Basin, including the Chorus Frog, Pseudachs maculata.
Chorus Frog (Pseudacris maculata).
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While data analysis is continuing, a few general trends have started to emerge. Differences in amphibian
species diversity among wetlands within WMAs, WPAs, WRP land, and privately owned land seem to be
minimal, but somewhat lower species diversity has been observed in the agricultural reuse pits. This may
suggest that many of the amphibian species are generalists, adaptable to any habitat with water, but prefer
actual wetlands over the agricultural reuse pits. Once data analysis is complete, researchers hope to have a
better idea of how land use impacts amphibian communities. The team hopes to continue monitoring
amphibian communities in wetlands within the Rainwater Basin to document community trends and develop a
long-term data set.
To learn more, contact Ted LaGrange (ted.lagrange@nebraska.gov; 402-471-5436), Nebraska Game and Parks
Commission.
Nebraska's Intensification Project was a joint effort among the Nebraska Game and Parks Commission, the University
of Nebraska-Lincoln, U.S. EPA, U.S. Fish & Wildlife Service, U.S. Army Corps of Engineers, Natural Resources
Conservation Service, U.S. Geological Survey, Nebraska Department of Environmental Quality, the Rainwater Basin
Joint Venture, the Playa Lakes Joint Venture, the Saline Wetland Conservation Partnership, and The Nature
Conservancy.
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Chapter 3: National Results
The goal of the CWA is to restore and maintain the "chemical, physical, and biological integrity" of the
nation's waters. NWCA examines these three aspects of the ecological quality of aquatic systems
through a set of commonly used and widely accepted indicators. It does not include all aspects of
ecological integrity or all possible chemical, physical, or biological stressors known to affect wetland
systems.
This chapter presents the results from the NWCA 2011 using: 1) an indicator of biological condition, 2)
physical, chemical, and biological indicators of stress, and 3) a ranking of the relative importance of the
stressors in affecting biological condition. Results for each indicator are shown for wetlands nationally
and for the four NWCA Aggregated Ecoregions established for reporting. Regional results are presented
in Chapter 4.
Results for wetland condition are estimates of the extent of wetland area (presented as percent area
and numbers of acres) in three condition classes (good, fair, and poor). Results for the indicators of
stress are presented as estimates of the percent wetland area in a particular stressor-level class
(generally, low, moderate, and high). See Chapter 2 of this report, and the NWCA 2011 Technical Report
(USEPA 2015) for details on how these estimates are made. The estimated wetland area results are
often referred to as population estimates, and each estimate is accompanied by a confidence interval
that conveys the level of certainty or confidence in the estimate (see text boxes "How to Read and
Interpret NWCA Results Figures" and "Confidence Interval" below).
HOW TO READ AND INTERPRET NWCA RESULTS FIGURES
Vegetation MMI
Percent Area
This example figure displays national and
ecoregion estimates of biological condition
as measured by the VMMI
National estimates of
condition or stress level
are shown by the first
group of bars, followed
by estimates for each of
the NWCA Aggregated
Ecoregions
Vegetation MMI
Area
Confidence Interval - displays level of
certainty or confidence in the estimate
Eastern Mtn &
Upper Midw
Number shows the value of the
estimate represented by the bar
(e.g., 61% of wetland area in the
West is in Poor condition)
Wetland area, in acres, nationally or
within an ecoregion in each of the
condition or stress level categories
Proportion of wetland area nationally
or within an ecoregion in each of the
condition or stress level categories
Condition classes (this example) or stressor levels are indicated by colors:
Condition Class:
Green = Good
Yellow = Fair
Red = Poor
Stressor Level:
Green = Low
Yellow = Moderate
Red = High
Dark Red = Very High
Gray = Unassessed (area that could not be sampled)
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Chapter 3 | National Results
Confic
CONFIDENCE INTERVALS
Confidence intervals convey the level of certainty or confidence in the estimates presented in this report. For
example, for the VMMI, NWCA found that 48% of the nation's assessed wetland acres are in good condition,
with a confidence interval of +/- 5%. This means that there is a 95% certainty that the real value is between
43% and 53%. The confidence interval is influenced by the number of sites sampled. As more wetland sites are
sampled, the confidence interval becomes narrower, meaning there is more confidence in the findings. Figure
3-1 shows an example of this pattern, in which the confidence interval for the national results (the largest
sample size) is narrowest, whereas the confidence intervals for the NWCA Aggregated Ecoregions (smaller
sample sizes), are generally broader. Ultimately the number of sites sampled is a tradeoff between the need
for increased certainty to support management and policy decisions, and the cost in money and resources to
perform more extensive monitoring activities. Note, confidence intervals are shown in the results figures for all
NWCA population estimates presented in this report.
Biological Condition Based on Vegetation MMI
Vegetation is a major component of the biodiversity found in wetlands and also provides habitat for a
broad range of microbes, insects, amphibians, reptiles, birds, and mammals. The composition and
abundance of plant species reflects, as well as influences, the hydrology, water chemistry, and soil
properties of wetlands. Vegetation is a particularly good indicator of wetland condition because of its
ability to integrate different wetland processes and because plants respond to physical, chemical, and
biological disturbances at multiple temporal and spatial scales. Using field collected data and plant trait
information, a national Vegetation Multimetric Index (VMMI) was developed. (See Chapter 2 in this
document, and the NWCA 2011 Technical Report (USEPA 2015) for more details). The VMMI serves as
the indicator of biological condition for the NWCA.
The condition of wetlands at national and ecoregional scales is shown in Figure 3-1. This figure presents
both the percentage of wetland area and the number of wetland acres in different condition classes
(good, fair, and poor). The NWCA found nationally, 48% of the wetland area (29,998,957 acres) is in
good condition, while 20% (12,179,915 acres) is in fair condition. The remaining 32% (19,977,327 acres)
of the wetland area is in poor condition.
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National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
Vegetation MMI
Percent Area
Vegetation MMI
Area
0 20 40 60 80 100 0 20.000,000
Percent Area Area
i i Good I I Fair I^H Poor
40,000,000
Figure 3-1. Estimated extent of wetland biological condition by condition classes (good, fair, poor) based on the
VMMI. Results are reported for the nation and by NWCA Aggregated Ecoregion.
The regional results apply to specific NWCA Aggregated Ecoregions, and care must be taken when
comparing results across the four ecoregions. It is important to note that the level of human-mediated
disturbance for reference (least disturbed) sites varied by region and wetland type. For example, in the
Interior Plains and West, reference sites have the highest level of disturbance. Reference sites for
estuarine wetlands, which are predominantly found in the Coastal Plain, have the lowest level of
disturbance. See NWCA 2011 Technical Report (USEPA 2015) for details.
Wetland area varies significantly among the NWCA Aggregated Ecoregions. For example, in the NWCA
survey, the West represents only 6% of the total assessed wetland area of the target wetland types
sampled across the country. In the West, 61% of the wetland area (2,214,806 acres) is in poor condition,
representing a major proportion of the wetland area for that ecoregion, but a small proportion of the
total wetland area nationally. The West has 21% and 18% of wetland area (782,525 and 649,729 acres)
in good and fair condition, respectively.
The Coastal Plains, Eastern Mountains and Upper Midwest, and Interior Plains have a range of 44% to
52% wetland area in good condition. The Eastern Mountains and Upper Midwest has 11% of wetland
area (2,117,215 acres) in fair condition and 37% (7,462,851 acres) in poor condition. In the Coastal
Plains, 21% of wetland area (6,620,942 acres) is in fair condition and 29% (8,808,894 acres) is in poor
condition. In the Interior Plains, 36% of wetland area (2,792,028 acres) is in fair condition while 19%
(1,490,777 acres) is in poor condition.
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As future NWCA surveys are implemented, we will be able to use the 2011 results as a point of
comparison to track whether wetland areas are getting better (i.e., moving to good condition) or worse
(i.e., moving to poor condition) within each aggregated ecoregion.
Indicators of Stress
The NWCA also includes measurements of indicators of stress, which are physical, chemical, and
biological factors that have the potential to reflect human-mediated impacts on wetland condition. The
indicators of stress do not necessarily directly cause ecological decline, but are often associated with
changes in wetland condition. While these stress indicators are expected to be associated with effects
on wetland condition, both in their presence and magnitude, the exact relationship between them and
condition cannot be explicitly determined from the data collected in the NWCA. A goal of the NWCA was
to characterize indicators of stress that are common in wetlands to help inform priorities for
management actions. See Chapter 2 in this document, and the NWCA 2011 Technical Report (USEPA
2015) for more detail on the development of each indicator of stress.
For simplicity of language, in the remainder of this chapter, "indicators of stress" are sometimes
referred to as "stressors." The results report the extent of the NWCA 2011 stress indicators by stressor
levels (low, moderate, or high). Stressor extent is an estimate of how spatially common an indicator of
stress is nationally or within each NWCA Aggregated Ecoregion.
Physical
Wetlands can be influenced by physical changes to the ecosystem and its immediate surroundings. For
the NWCA, physical data collected by crews were categorized and assigned to one of six indicators
representing alteration of wetland vegetation or hydrology: vegetation removal, vegetation
replacement, damming, ditching, surface hardening, and filling/erosion (see Figure 2-4).
Vegetation Alteration
Vegetation alteration was identified by either the removal or replacement of vegetation. The vegetation
removal indicator evaluated the loss, removal, or damage of vegetation either within the assessment
area or the assessed buffer area immediately surrounding it. Nationally, the vegetation removal stressor
is low for 56% of the wetland area and high for 27% (Figure 3-2). However, this varied greatly by NWCA
Aggregated Ecoregion. In the Coastal Plains and Eastern Mountain and Upper Midwest, the degree of
vegetation removal for most of the wetland area fell into the low stressor level. In contrast, a large
proportion of the wetland area in the Interior Plains and West have high stressor levels from vegetation
removal, encompassing 44% and 61% of the wetland area in the Interior Plains and West, respectively.
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Vegetation Removal
Percent Area
Chapter 3 \ National Results
Vegetation Replacement
Percent Area
National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
18%
72%
66%
22%
81%
16%
3%
\—
h
B
— I 17%
| — | 24%
1 59%
97°
I-
}\ 2%
1%
0 20 40 60 80 100 0 20 40 60 80 100
Percent Area Percent Area
I^B Lowi i Moderate ^M High
Figure 3-2. Estimated extent of vegetation alteration in wetlands by stressor levels as indicated by vegetation
removal and vegetation replacement. Results are presented nationally and by NWCA Aggregated Ecoregion.
The vegetation replacement indicator documented major changes to the natural vegetation structure
and composition due to anthropogenic activities (e.g., conversion of natural plant communities to golf
course, lawn, park, row crops, nursery, etc.). Nationally, and within each of the NWCA Aggregated
Ecoregions, wetland area is predominantly found at low stressor levels related to vegetation
replacement (Figure 3-2). Moderate and high stressor levels associated with vegetation replacement are
found in 18% and 10% of national wetland area, respectively.
Hydro/logic Alteration
Information collected by crews pertaining to alterations of wetland hydrology were used to develop four
stressor indicators: damming, ditching, hardening, and filling/erosion. For each of these four indicators,
the majority of wetland area nationally have low stressor levels (Figure 3-3). Of these four, ditching and
surface hardening are found to have the largest extent of wetland area at high stressor levels nationally,
23% and 27%, respectively. Among the ecoregions, the West has the largest proportion of wetland area
at high stressor levels for damming, ditching, and surface hardening. In the other ecoregions, the
majority of wetland area have low stressor levels for the evaluated hydrologic stressors.
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Damming
Ditching
Hardening
Filling/Erosion
National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
Percent Area Percent Area Percent Area Percent Area
I 1 Low I I Moderate^B High
Figure 3-3. Estimated extent of hydrologic alteration in wetlands by stressor levels as indicated by damming,
ditching, hardening, and filling/erosion. Results are presented nationally and by NWCA Aggregated Ecoregion.
Chemical
Chemical stressors that can impact the condition of wetlands include excess nutrients, metals, organic
toxins, and other chemical compounds that can disrupt nutrient cycles, affect plant and animal growth,
and be detrimental to human health. Two chemical indicators of stress were developed for NWCA using
data from soil samples collected at each site: a Heavy Metal Index and concentration of soil phosphorus.
At some sites it was not possible to collect a soil sample because of ponded water or other site
conditions on the sampling day. Additionally, at some sites in the Interior Plains ecoregion soil samples
were not analyzed using NWCA laboratory protocols. As a result, these sites could not be evaluated for
the chemical stressors. Another potential indicator of stress, microcystin (an algal toxin) concentration,
is discussed separately at the end of this chapter.
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Heavy Metals
Chapter 3 \ National Results
Total Phosphorus
National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
0 20 40 60 80 100 0 20 40 60 80 100
Percent Area Percent Area
i i Lowi I Moderatei^B Highi I Unassessed
Figure 3-4. Estimated extent of chemical indicators of stress in wetlands by stressor levels as indicated by a
Heavy Metal Index and soil phosphorus concentrations. Results are presented nationally and by NWCA Aggregated
Ecoregion.
Concentrations of twelve heavy metals found in soils and closely associated with human activities
comprised the Heavy Metal Index. Heavy metals have measured concentrations below background
levels across most sites. Consequently, the majority of assessed wetland area nationally, 73%, is at low
levels for this stressor (Figure 3-4). Moderate levels are found in 18% of wetland area nationally, and
high levels in only 2%. Soil samples could not be collected or were not analyzed for heavy metal
concentrations for 7% of wetland area nationally. Of the four NWCA Aggregated Ecoregions, Eastern
Mountains and Upper Midwest and West have the greatest estimated percentage of wetland area at
high stressor levels (4% and 5%, respectively).
Soil phosphorus is a necessary plant nutrient, but at high levels can indicate human-mediated impacts.
Soil phosphorus concentration thresholds were determined using a distribution-based approach (see
Chapter 2). Nationally, the majority of wetland area, 69%, is at low stressor levels (Figure 3-4), while 19%
of wetland area is at moderate stressor levels. Soil phosphorus concentrations are not assessed for 7%
of the wetland area due to difficulties in collecting soil samples or because some soil samples were not
analyzed using NWCA lab protocols. Among the NWCA Aggregated Ecoregions, wetland area with soil
phosphorous concentrations at low stressor levels ranges from 63 to 88%. The greatest estimated extent
of wetland area at high stressor levels is found in the Eastern Mountain and Upper Midwest (13%) and
in the Coastal Plains (3%).
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Chapter 3 | National Results
Biological
In addition to looking at the chemical and physical stressor indicators that can impact wetland systems,
the NWCA developed a Nonnative Plant Stressor Indicator (NPSI) to assess the level of biological stress
in wetlands. Nonnative plants can have numerous direct and indirect effects on native vegetation and
ecosystem components. This indicator used three metrics: the relative cover of nonnative species,
richness of nonnative species (the number of unique nonnative species), and relative frequency of
occurrence of nonnative species. Wetlands were assessed as having low, moderate, high, or very high
stressor levels based on the potential impact of nonnative plants on the native vegetation of the site.
Nationally, 61% (37,709,004 acres) of the wetland area are estimated to have low stressor levels from
nonnative plants, but results are not uniform across the country (Figure 3-5). In the Eastern Mountains
and Upper Midwest and the Coastal Plains stressor levels based on the NPSI are low for 74% (14,761,495
acres) and 66% (20,358,855 acres) of the wetland area, respectively. In the Interior Plains and West, the
extent of wetland area at low stressor levels is much smaller, 27% and 14%, respectively. In the Interior
Plains, the extent of wetland area is distributed more uniformly across the four NPSI stressor levels, with
relatively similar proportions of area having low, moderate, high, and very high stressor levels. In the
West, the majority of wetland area, 71% (2,602,079 acres) is estimated to have high or very high
stressor levels as indicated by the NPSI.
Nonnative Plants
Percent Area
Nonnative Plants
Area
National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
20 40 60 80 100 0
Percent Area
i i Low i i Moderate ^H
High I
20,000.000
Area
Very High
40,000.000
Figure 3-5. Estimated extent of biological stress in wetlands by stressor levels as indicated by the Nonnative
Plant Stressor Indicator. Results are presented nationally and by NWCA Aggregated Ecoregion.
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Chapter 3 \ National Results
Ranking of Stressors
An important function of the NWCA is to provide information for sound policy and decision-making to
support the maintenance and improvement of wetland ecological quality. It is important for resource
managers to understand not only which stressors are present nationally and in various regions, but to
have information on the potential impact of stressors on ecological condition and to be able to rank
those stressors in terms of the estimated improvements we might expect by reducing or eliminating
them. To meet these objectives, the NWCA uses relative extent, relative risk, and attributable risk to
consider how stressors could influence the ecological condition of wetlands. An overview of these three
concepts is provided here. Further details on their calculation can be obtained in the NWCA 2011
Technical Report (USEPA 2015, Chapter 9).
Relative extent ranks the stressor indicators in terms of the amount of wetland area affected by a high
level of each stressor indicator evaluated. Relative risk is the probability or likelihood of having poor
biological condition when the magnitude of a stressor indicator is high relative to when it is low. Relative
risk analysis is commonly employed in medicine where it has been used to describe the risk of having a
health problem relative to a potential cause or its indicator. For example, a person who smokes has a
greater risk of developing lung cancer. Often this is presented as a relative risk ratio; for example, a
person who smokes is 15 to 30 times more likely to get or die of lung cancer than someone who does
not (CDC 2015). Similarly, the relative risk value for an ecological stressor measures the likelihood that a
wetland will have poor ecological condition if the wetland has high levels of the stressor rather than if
the wetland had low or moderate levels of the stressor. Finally, calculation of attributable risk provides
an estimate of the proportion of the wetland area in poor condition that could be reduced if the effects
of a particular stressor were eliminated.
It is important to note that while the NPSI was reported with the other indicators of stress in the
previous section, it is not used in the analyses to describe risk. Because relative and attributable risk
specifically relate stressors to condition, and both the NPSI and VMMI use related data, it is not
appropriate to include the NPSI in reporting relative and attributable risk. Although nonnative plant
species likely confer risk to wetland condition (see the wetland area extent estimates for the NPSI in the
previous section), this risk cannot be evaluated using the relative and attributable risk approach.
National results for relative extent, and relative and attributable risk for each stressor indicator are
presented in the following sections of this chapter. Specifics on stressor indicators for each of the NWCA
Aggregated Ecoregions are given in Chapter 4.
Relative Extent and Relative Risk
Relative extent is a way to evaluate how widespread and common a high stressor level for each stressor
is across the wetland area. A stressor with a high relative extent suggests a national concern. Figure 3-6
(left panel) shows the proportion of wetland area in the U.S. with high stressor levels for each of the
stressor indicators. Vegetation removal, surface hardening, and ditching are the most pervasive
stressors across the nation. High levels of vegetation removal and surface hardening stressors are found
for 27% of the wetland area, while 23% of wetland area has high levels of the ditching stressor.
NARS and the NWCA use the concept of relative risk to estimate the severity of stressor effects. Relative
risk is the probability or likelihood of having poor resource condition when a stressor level is high
relative to when the stressor is low or moderate. For the NWCA, biological condition is described by the
VMMI. A relative risk value of 1 indicates that the stressor indicator has no effect on condition. Relative
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Chapter 3 | National Results
risk values greater than 1 suggest that the stressor has a greater impact on biological condition (e.g., the
vegetation removal indicator has a relative risk of 1.9, indicating that the likelihood of having a poor
VMMI score is 90% greater in wetlands with high levels of vegetation removal).
Figure 3-6 (central panel) shows the relative risk, or relative effect, of each stressor on wetland
condition. At the national level, vegetation removal, surface hardening (e.g., soil compaction), ditching,
damming, filling/erosion, and vegetation replacement are highly associated with poor biological
condition in wetlands with relative risk ranges from about 1.5 to 1.6. There does not appear to be a clear
relationship between high soil phosphorus or heavy metal concentrations and poor biological condition.
Relative Extent
High Stressor Levels
Relative Risk
Attributable Risk
Vegetation Removal -
Hardening
Ditching -
Damming
Filling/Erosion
Vegetation
Replacement
Soil Phosphorus
Heavy Metals
27%
27%
10 15 20 25 30 35 0.0
Percent of Area
High Stressor Levels
1.0 1.5
Relative Risk
Attributable Risk
Percent of Area
Figure 3-6. National level estimates for relative extent of stressor indicators when stressor level is high, relative
risk associated with each stressor indicator, and attributable risk for each stressor indicator relative to wetland
biological condition.
Attributable Risk
NWCA uses the calculation of attributable risk to estimate the proportion of wetland area in poor
condition that could be reduced if the effects of a particular stressor indicator were eliminated.
Attributable risk combines relative extent and relative risk into one value to evaluate the impact of a
stressor across the assessed area. The calculation of attributable risk assumes that the stressor causes
poor condition, the effects of the stressor can be reversed, and that the stressor's impact on condition is
independent of other stressors. These assumptions are difficult to meet with survey data like those
collected in the NWCA. Despite these limitations, estimates of attributable risk can provide general
guidance as to what stressors are affecting condition and to what degree (relative to the other stressor
indicators evaluated). This information can provide an indication of how policymakers and resource
managers could prioritize actions and the use of limited resources by stressor, geographic region, and/or
wetland type.
Figure 3-6 (right panel) shows the attributable risk for each of the stressor indicators across the nation.
The stressors are ranked according to their attributable risk. The stressor categories with the highest
attributable risk values are vegetation removal and surface hardening, with 19% and 18%, respectively,
of the wetland area potentially affected by each. This estimate suggests, for example, that if high levels
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Chapter 3 \ National Results
of vegetation removal are eliminated as a stressor, one would expect to see 19% of wetland acres
improve to good or fair biological condition. Ditching has the next highest relative risk, potentially
affecting 12% of the wetland area. It is also important to note that some stressors can have large
relative risk values but small attributable risk estimates because the relative extent is small. For
example, filling/erosion is found at high levels in only 10% of the wetland area. Although the relative risk
number is about 1.6, the attributable risk estimate indicates that nationally only about 6% of wetland
acres may improve to good or fair biological condition by eliminating filling/erosion.
These attributable risk estimates indicate the need to continue efforts to reduce the impact of
vegetation removal, surface hardening, and ditching nationally. Although some stressors, such as
filling/erosion, might not be as widespread nationally, that does not mean that localized management
actions targeting these stressors are not needed.
Microcystin Presence and Risk
Microcystins are one group of naturally occurring toxins produced by various cyanobacteria (blue-green
algae) that are common in surface waters. Microcystins have been detected nationally in lakes and
reservoirs and are considered to be the most commonly occurring class of cyanobacteria toxins
(cyanotoxins). Three main exposure scenarios are of potential concern regarding microcystins and
wetlands: direct ecological impacts on plants and animals, human consumption of exposed organisms,
and direct human exposure through recreational contact. As in other NARS assessments, the microcystin
results reported here focus on risks associated with recreational contact. Information on other exposure
risks is discussed in the NWCA 2011 Technical Report (USEPA 2015, Chapter 10).
Although there are relatively few documented cases of human health effects from exposure to
cyanotoxins through recreational activities, exposure to cyanobacteria or their toxins may produce
allergic like reactions such as skin rashes, eye irritations, respiratory symptoms, and in some cases
gastrointestinal illness, liver and kidney damage, and in rare cases even death. During recreational
activities, exposure for humans may occur through accidental ingestion, inhalation or direct contact.
Cyanotoxins can also be a concern in drinking water.2 In addition to human impacts, livestock, pets and
wildlife are also exposed to cyanotoxins when consuming scum or drinking cyanotoxins-contaminated
water. The probability of adverse recreational health effects for humans due to cyanobacteria and/or
microcystin exposure is frequently assessed based on World Health Organization (WHO) guidance
thresholds (see Table 2-2). Many states have developed harmful algal bloom (HAB) guidance thresholds
in the event of a cyanobacterial bloom and cyanotoxins in recreational waters.
The occurrence of microcystins in wetlands at national and ecoregional scales is shown in Figure 3-7.
This figure presents both the percentage of wetland area and the number of wetland acres where
microcystin is detected, not detected, or unassessed (i.e., no microcystin sample was collected). The
NWCA found that, nationally, 12% of wetland area has detectable concentrations of microcystin.
Microcystin is not detected at 27% of wetland area, nationally, and 61% of wetland area is unassessed.
The large percentage of unassessed wetland area is due to the large number of wetland sites where
water depth was not deep enough for a microcystin sample to be collected. At the ecoregional scale,
NWCA finds that the Interior Plains has the highest percent of wetland area with detectable
2 In June 2015, EPA announced health advisory values for microcystin in drinking water. The Agency is using a non-
regulatory option of health advisories to address the growing public health threat of cyanotoxins in drinking water.
The health advisory values are 0.3 micrograms per liter (u.g/L) for children younger than six and 1.6 ug/L for
children six and older and adults.
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Chapter 3 | National Results
concentrations of microcystin at 34%. This is much larger than the other NWCA Aggregated Ecoregions,
which each have ranges closer to the national estimate.
Microcystin Presence
Percent Area
Microcystin Presence
Area
National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
20 40 60 80 100 0
Percent Area
30,000,000 60,000,000
Area
Not Detected ^B Detected CZZ] Unassessed
Figure 3-7. Estimated occurrence of microcystin in wetlands. Results are presented nationally and by NWCA
Aggregated Ecoregion.
The level of risk associated with recreational exposure to microcystin in wetlands at national and
ecoregional scales is shown in Figure 3-8. This figure presents both the percentage of wetland area and
number of wetland acres in different risk categories (low, moderate, high) based on the WHO
thresholds. Nationally, and across the NWCA Aggregated Ecoregions, NWCA finds very little wetland
area (< 1%) at either moderate or high risk levels. Most wetland area is at low risk levels or could not be
assessed.
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National
Coastal
Plains
Eastern Mtn. &
Upper Midw.
Interior
Plains
West
Miprocystin Risk
Percent Area
39%
40%
61%
60%
34%
I 66%
1= =| 1 43%
1=1-
1=1 1 48%
I=H 1 52%
Microcystin Risk
Area
0 20 40 60 80 100 0
Percent Area
i i I nw Risk I I Moderate Risk •
Figure 3-8. Estimated extent of recreational health risk from exposure to microcystin by risk category (low,
moderate, and high) based on WHO guidelines. Results are presented nationally and by NWCA Aggregated Ecoregion.
30,000,000 60,000,000
Area
High Risk i 1 Unassessed
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Highlight
Alaska's Arctic Wetlands Assessment
Terri Lomax, Alaska Department of Environmental Conservation
In 2011, as part of EPA's National Wetland Condition Assessment (NWCA) the Alaska Department of
Environmental Conservation (DEC) completed a wetland condition assessment in the Arctic Coastal
Plain region of the National Petroleum Reserve-Alaska. Due to Alaska's size and limited
infrastructure statewide surveys are not feasible, leaving regional assessments as a more realistic
option for sampling in Alaska. DEC partnered with the University of Alaska Anchorage and the North
Slope Borough to complete this survey.
Freshwater emergent wetlands are the
dominant wetland type in the region, and
were selected from the National Wetland
Inventory within the sample region. Within
this sample frame 57,188 freshwater
emergent wetland polygons exist, totaling
more than 5 million acres. To relieve
community concerns with potential helicopter
interference of subsistence hunting activities
we created a buffer around high subsistence
use areas and excluded sites in the sample
frame that fell within the buffer. From the
remaining population, 40 random sites were
selected according to NWCA protocols. Alaska's limited infrastructure, small population base, and
the remote nature of most of the state drives the selection of sites in random surveys, typically only
selecting sites with reference or near reference condition. In prior DEC surveys this proved to be
problematic as range of disturbance is needed to understand condition and develop metrics based
on stress. To overcome this we added 10 targeted sites to our survey, these sites with known or
potentially impacted freshwater emergent wetland sites within the sample area.
Wetlands in this region differ significantly from wetlands surveyed in the contiguous United States
and therefore required modifications to national methods. The Arctic Coastal Plain, the land of the
midnight sun and the polar night, is a vast treeless area underlain by continuous permafrost. In
cooperation with EPA, DEC modified the national methods to include non-vascular plant
identification, modified soil methods to account for permafrost conditions, and excluded analysis
requiring short hold times.
Overall, assessment areas averaged 33 cm of water depth and 16% of the area was covered with
surface water. Sites averaged an 89 meter vegetated buffer out of the 100 meters evaluated. The
plant community was comprised of short woody and emergent species. 65% of sites were
dominated by Carex aquatilis, Eriophorum vaginatum was the second most common species
Arctic Wetlands. Photo courtesy of Alaska DEC.
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identified. Other common plants included several species of Salix, Eriophorum russeolum and
angustifolium, and Betula nana, all typical of arctic emergent wetlands. Permafrost was
encountered at all sites, at an average depth of 43 cm.
Results were evaluated for patterns across the landscape, overall, and in targeted verses random
sites. Differences were observed between random verses targeted sites, but otherwise no significant
patterns were observed. The percentage of sites with stressors identified in the buffer and
assessment area was greater in targeted sites, additionally plant and diatom richness was greater at
targeted sites than random sites. Targeted sites were typically adjacent to previous military
installments with one to several meters of fill forming a pad on the tundra. Water chemistry and soil
profiles did not demonstrate significant differences.
As expected, stressors were more often observed in targeted sites and typically involved changes in
the soil (soil compaction, recent fill, and grading). The next most common stressor identified was
off-road vehicle use. Mild to moderately severe stressors were observed in the assessment area of
100% of targeted sites and mild stressors were observed in 37% of random sites. Similar stressors
were observed in the buffer of all targeted and none of the random sites. We are continuing to
evaluate the data in relation to lake, river, stream and coastal surveys in the same region.
The success of our survey is attributed to our partnerships. Working with local tribal governments,
federal and state agencies, and the University was crucial to overcoming numerous challenges.
During field work we experienced freezing weather, gale force winds, equipment malfunctions,
medical emergencies, and major logistical hurdles. In spite of these challenges, we were able to
sample 41 out of the 50 wetlands selected.
To learn more, contact Terri Lomax (terri.lomax@alaska.gov; 907-269-7635), Alaska Department of
Environmental Conservation, or visit: https://dec.alaska.gov/water/wqsar/monitoring/AKMAP.htm
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Chapter 4: Ecoregion and Wetland Type Results
Ecoregions are geographic areas with similar environmental characteristics, such as climate, vegetation,
type of soil, and geology. EPA has defined ecoregions at various scales, from large areas to finer units of
the landscape (Omernik 1987, USEPA 2011a). The EPA ecoregions have been widely used in assessing
resource status, establishing water quality and biological condition criteria, and setting management
goals for resource protection. NARS uses the various levels (scales) of these EPA ecoregions because
they were developed to support decision-making for aquatic resources, and it is important to consider
aquatic and other natural resources within the context of their ecological setting.
Wetlands in an ecoregion tend to have more similar natural characteristics to each other than with
wetlands in other parts of the country. Forested wetlands in the Upper Midwest, for example, share
more similar traits with other forested wetlands in this region than they do with forested wetlands in
the Coastal Plain. Additionally, different wetland types have distinct characteristics that distinguish them
from other wetland types. Wetland types and ecoregions are useful in evaluating and understanding
results describing ecological condition and stress because of these patterns.
Previous NARS studies have combined Level III ecoregions into nine major ecoregion groups in order to
evaluate the data at ecoregional scales. In the NWCA, to ensure enough sample points within a
reporting group to present statistically valid results, it was necessary to combine ecoregions and
wetland types for data analysis (see Chapter 2, How are the NWCA results presented?).
The four NWCA Aggregated Ecoregions (Figure 4-1) are based on a combination of smaller scale EPA
ecoregions:
• Coastal Plains
• Eastern Mountains & Upper Midwest
• Interior Plains
• West
The seven NWCA wetland types were combined into four NWCA Aggregated Wetland Types:
• Estuarine Herbaceous
• Estuarine Woody, which represents both scrub-shrub and forested wetlands.
• Inland Herbaceous, which represents emergent, unconsolidated bottom/aquatic bed, and
farmed wetlands not in crop production.
• Inland Woody, which represents both forested and scrub-shrub wetlands.
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Chapter 4 \ Ecoregion and Wetland Type Results
NWCA Aggregated Ecoregions
_] Coastal Plains
j Eastern Mountains and Upper Midwest
~~] Intonof Plains
I I Wesi
Figure 4-1. The NWCA Aggregated Ecoregions. Chapter 2 of this report and the NWCA 201 I Technical Report
(USEPA 2015) detail the compilation of these four ecoregions.
In this chapter, condition and stress results are reported by each major NWCA ecoregion group and for
NWCA aggregated wetland types:
• Results for each of the four NWCA ecoregions are presented in two ways based on 1) all NWCA
wetland types occurring in a region; and 2) aggregated inland herbaceous and inland woody
wetland types within a region.
• Results for estuarine herbaceous and estuarine woody wetland types are presented in the
Estuarine Wetlands section of this chapter and include all NWCA ecoregions where estuarine
wetlands occur (Coastal Plains, Eastern Mountain and Upper Midwest, and West).
NWCA results should not be extrapolated to an individual state or specific wetland within the ecoregions
because the study is not intended or designed to characterize conditions at these finer scales. A number
of states worked with EPA to design and implement statistically-based assessments at the state scale in
order to characterize the condition of wetland populations within their states. Short highlights
discussing these studies appear throughout the report.
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Chapter 4 | Ecoregion and Wetland Type Results
Coastal Plains Ecoregion
Landscape setting of the ecoregion
The Coastal Plains ecoregion includes the Mississippi Delta
and Gulf Coast, runs north along the Mississippi River to the
Ohio River, and includes Florida and eastern Texas, and the
Atlantic seaboard from Florida to Cape Cod.
The Coastal Plains is relatively flat and much of the area is
less than 500 feet above sea level. Most of the region is
composed of sedimentary rocks or unconsolidated sediments
of marine origin, with some areas made up of younger alluvial
deposits. A large proportion of the natural vegetation is
mixed pine and hardwood forests. Along the western edge of
the region (coastal Texas and Louisiana), post oak savanna and prairie vegetation is more common. The
Mississippi River Valley is dominated by bottomland deciduous forests.
The climate in the Coastal Plains is temperate wet to subtropical, with average annual temperatures
ranging from 50 to 80°F. Average annual precipitation ranges from 30 to 79 inches.
Although many areas had been previously cleared for agricultural purposes, much of the region has
been reforested or is used for lumber and pulpwood production. Agricultural crops, pasture, and
rangeland is found throughout the region, but production of cotton, soybeans, rice, and sugarcane
remains a dominant land use in the Mississippi Valley.
The types of wetlands found throughout the region are
diverse. Tidal salt and brackish marshes and tidal and non-tidal
freshwater marshes are found along the Gulf and Atlantic
coasts. In the most southern part of the region (central Florida
and southward) mangrove swamps are found in association
with coastal marshes. In the interior portions of the Coastal
Plains, bottomland hardwood forests and swamps occur along
rivers, streams, and their headwaters. Other wetlands found
throughout the Coastal Plains region are locally referred to as
flatwoods, pineywoods, pine savannas, pine barrens, flatlands,
and coastal prairies. These wetlands can be dominated by
herbaceous plants, hardwoods, pines, or a mixture of
vegetation. Freshwater bogs, called pocosins, are found from
southern Virginia to northern Florida.
In the Coastal Plains, there are several well-known wetland
complexes, including the Florida Everglades, the Okefenokee
Swamp in southeastern Georgia and northeastern Florida, the
Great Dismal Swamp in southeastern Virginia and northeastern North Carolina, and the Louisiana Delta
(a complex of forested wetlands, freshwater marshes, salt marshes, and shallow coastal lakes).
Swamp in Florida (site NWCA11-1258).
Photo courtesy of University of Florida.
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Chapter 4 \ Ecoregion and Wetland Type Results
Summary of findings
A total of 513 randomly selected sites were sampled in the Coastal Plains ecoregion during the 2011
field season, representing 30,893,305 acres. Of the total number of Coastal Plains sites sampled, 62 are
inland herbaceous wetlands, representing 3,750,551 acres, and 163 are inland woody wetlands,
representing 21,859,265 acres. Estuarine wetlands in the Coastal Plains include 288 sites, representing
5,283,489 acres. Detailed results for estuarine wetland types are reported in the Estuarine Wetlands
section of this chapter.
Biological Condition
For all wetland types assessed in the Coastal Plains (Figure 4-2), 50% of the estimated wetland area is in
good condition; 21% is in fair condition and 29% is in poor condition based on the Vegetation
Multimetric Index (VMMI) (see Chapter 2 for details on the VMMI). The proportion of wetland area in
good (50%), fair (26%), and poor (25%) is similar for inland woody wetlands in this ecoregion. The NWCA
found that the proportion of inland herbaceous wetlands in poor condition, however, is much larger,
59%, than the proportion of inland woody wetlands in poor condition (Figures 4-3 and Figure 4-4).
Indicators of Stress
For all wetland types assessed in the Coastal Plains, vegetation removal, ditching, and surface hardening
are the indicators with the greatest proportion of wetland area at high stressor levels (Figure 4-2).
However, the majority of wetland area throughout the ecoregion has low levels for each of the
stressors. Key findings include:
• Vegetation removal is high for 25% of the wetland area compared to moderate for 21% and low
for 54% of wetland area.
• Hardening levels are high in 23% of wetland area, while 9% and 69% of wetland area have
moderate or low stressor levels, respectively.
• Ditching is high in 21% of the wetland area, moderate in 5%, and low in 74%.
For inland wetland types assessed within the Coastal Plains ecoregion (Figures 4-3 and 4-4), data show:
• More than half of the area assessed for inland herbaceous wetlands has high stressor levels
associated with vegetation removal (61%), hardening (57%), and ditching (52%).
• The most prevalent stressors at high levels for inland woody wetlands are also vegetation
removal (24% of wetland area), hardening (20%), and ditching (16%), but these high stressor
levels are a smaller proportion of wetland area compared to the herbaceous wetlands.
• The extent of high levels of vegetation removal, damming, ditching, hardening, and
filling/erosion stressors are greater in inland herbaceous wetlands than in inland woody
wetlands. Very high and high levels for the nonnative plant stressor indicator are also greater in
herbaceous wetlands.
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Chapter 4 | Ecoregion and Wetland Type Results
Coastal Plains
30.893.304 Acres
20 40 60 80
Percent Area
100 0
MMI
I I Good I I Fairl
Vegetation Stressors
20 40 60
Percent Area
Physical Stressors
I I Lowl I Moderatel
I Low
Moderate^H High
100 0 20 40 60 80 100
Percent Area
Soil Stressors
High I I Lowl I Moderate
^^B Highi 1 Unassessed
Non-Native Rant Species
i i Low i i Moderate
^H High f^B Very High
Figure 4-2. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the Coastal Plains.
Bars show the percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence intervals.
Coastal Plains
Inland Herbaceous Wetlands 3.750.551 Acres
So 1 Phosphorus
H+
0%
Eh
r
H 13%
H 10%
77%
Heavy Metals
1 1 1
3-<
0%
6%
=|— I 10%
84%
Nonnative Plant Species
I 1 —
•IF— i 13%
f-\B%
—I 56%
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
Percent Area Percent Area Percent Area
MMI
I Poor
Fair
Unassessed
Percent Area
Physical Stressors
i i Lowl i Moderate
^H Highi i Unassessed
Vegetation Stressors
I I I nwi i Moderate
§•1 Highi i Unassessed
Soil Stressors
I I Lowl i Moderate
^H Highi I Unassessed
Nonnative Plant Species
i i Lowi i Moderate
^H High^H Very High
Figure 4-3. NWCA survey results for the inland herbaceous wetland type across the Coastal Plains. Bars show
the percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence intervals.
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National Wetland Condition Assessment 2011
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Chapter 4 \ Ecoregion and Wetland Type Results
Coastal Plains
Inland Woody Wetlands 21,859.265 Acres
20 40 60 80
Percent Area
Poor I
Fair
Unassessed
100 0 20 40 60 80
Percent Area
Physical Stressors
i i Lowi i Moderate
•• High! "I Unassessed
Vegetation Stressors
I I I nwi 1 Moderate
^B Highi i Unassessed
100 0 20 40 60 80 100
Percent Area
Soil Stressors
i i Lowi i Moderate
^^H High I I Unassessed
Nonnative Plant Species
i i Lowi i Moderate
^H High^H Very High
Figure 4-4. NWCA 2011 survey results for the inland woody wetland type across the Coastal Plains. Bars show
the percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence intervals.
National Wetland Condition Assessment 2011
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Southeast Wetlands Monitoring and Assessment Intensification Study: North Carolina,
South Carolina, Alabama, and Georgia
Rick Savage and Kristie Gianopulos, N.C. Department of Environment and Natural Resources
Overview: Recognizing that natural ecosystems are not confined within state boundaries, four neighboring
states embarked on an unprecedented collaboration to study the condition of forested wetlands in the
Southeastern United States. North Carolina, South Carolina, Georgia, and Alabama performed a regional
analysis of forested wetlands within the Piedmont and Coastal Plain ecoregions, using both NWCA survey
methodologies and additional indicators of wetland health (i.e., amphibian, macroinvertebrates, and overall
landscape measures). The regional intensification project included 110 forested wetlands across the four
states involved in the study. Although the final analysis has not been completed, preliminary data reveal
differences in condition between the ecoregions, as well as areas of possible concern for amphibian
populations.
Sampling and Protocols: There
were 45 wetland sites sampled in
the Piedmont Region and 65
wetland sites sampled in the
Coastal Plain Region. At each of
these sites, NWCA data were
collected as well as additional
indicators, including for amphibians
and macroinvertebrates. This
intensification study developed a
composite scoring system from
several data indicators gathered at
each location in order to determine
the overall wetland condition at
each site. The preliminary wetland
condition index integrated several
important measurements into one
total, including the following
individual biotic and abiotic
measures: the vegetation mean C;
vegetation invasive species cover,
the Amphibian Quality Assessment
Index (AQAI), macroinvertebrate
diversity, the buffer Landscape
Development Intensity Index (LDI), the Ohio Rapid Assessment Method score, water quality nutrients, and soil
metals information. Mean C is a commonly used metric based on Coefficient of Conservatism values of the
plant species. Species are rated from 0 to 10 based on their fidelity to natural habitat; a high C value indicates
nearly all species occurrences are in pristine habitat and low C values are assigned to weedy species which are
Figure 1. Preliminary composite rankings for forested wetland sites; low rank
numbers indicate best quality and high rank numbers indicate lowest quality,
based on a variety of factors.
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National Wetland Condition Assessment 2011
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Jf*
11
A
Amphibian AOAI
A AQAI 1 to 2 4 {low)
AQAI 251040
A AQAI 4 110 7? (high)
PIEDMONT • ecoregion 45
COASTAL PLAIN - Ecoregloi
Figure 2. Wetland condition based on Amphibian AQAI indicator; low
numbers indicate low species quality.
tolerant of human-caused disturbance.
The LDI scores were developed using
GIS analysis of land uses and their
aerial extent surrounding sampled
wetland points. The AQAI values were
calculated using Coefficient of
Conservatism ratings developed for
amphibian species and an equation
identical to that used commonly for
floristic quality assessments (FQA).
Low AQAI values indicate low species
diversity at a given site, while higher
numbers correspond with increasing
quality.
What They Have Learned: Preliminary
data analysis reveal differences
between the ecoregions and have
identified areas of possible concern for
amphibian populations. Preliminary
composite rankings (Figure 1) for
forested wetland sites within the
region indicate that forested wetlands
in the Southeastern Coastal Plain
(riverine swamp forests) are in better condition than those in the Piedmont ecoregion (bottomland hardwood
forests). This may not be surprising since the Piedmont has been heavily farmed and is more densely
populated.
In addition to the overall composite score, specific measures like the AQAI provide insight into the condition of
wetlands and management implications for amphibian habitat. Amphibians are considered sentinel indicators
because of their sensitivity to environmental stress, making them ideal for regional biomonitoring. While all of
these results are preliminary, the AQAI scores derived from sampling site data are largely consistent with the
overall composite indicator of wetland condition.
Generally, greater numbers of amphibian species were found in
Coastal Plain sites, where unique species counts ranged from 3 to 12
(mean = 4.9). In the Piedmont ecoregion, the number of amphibian
species found at each site ranged from 1 to 7 species (mean = 3.8).
These numbers correspond to AQAI values in the good score (green),
fair (yellow), and poor score (red) categories as seen in Figure 2.
Similar to the findings of the overall composite scoring, AQAI values in
the Piedmont Region were relatively low or poor compared to AQAI
scores for the Coastal Plain wetlands. The marbled salamander is a
species particularly sensitive to anthropogenic disturbances, and is
found mainly in the highest quality wetland sites. Marbled salamander
were found in twice as many Coastal Plain sites (12) as Piedmont sites (6).
Overall, this type of wetland condition information can aid state and regional management decisions about
wetland services such as flood control, water quality filtering, or the identification of restoration needs and
opportunities. When the full analysis is complete, the improved knowledge of wetland condition in the
Southeast region will help state agencies and conservation organizations to target scarce resources toward
improving wetland condition in an efficacious way.
To learn more, contact Rick Savage (rick.savage@ncdenr.gov; 919-707-8792) or Kristie Gianopulos
(kristie.gianopulos@ncdenr.gov; 919-707-8796), N.C. Department of Environment and Natural Resources.
Marbled Salamander (Ambystoma
opacum).
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Chapter 4 | Ecoregion and Wetland Type Results
Eastern Mountains and Upper Midwest
Landscape setting of the ecoregion
The NWCA Eastern Mountains and Upper Midwest ecoregion
combines the Northern Appalachians, Southern Appalachians,
and the Upper Midwest NARS ecoregions. The region includes
portions of Minnesota, Wisconsin, Michigan, northeastern
Ohio, and virtually all of the New England states. It also
includes New York, Pennsylvania, West Virginia, most of
Kentucky, a significant part of Tennessee, as well as portions
of East Coast states interior to the Coastal Plains ecoregion.
The southern part of the ecoregion extends into northeastern
Alabama and the Ouachita Mountains in Arkansas, Missouri,
and Oklahoma.
Dominant landscape features of the Eastern Mountains and Upper Midwest ecoregion include the
Appalachian Mountains and the Great Lakes Basin. Retreating ice during the last glacial period and karst
topography were important in shaping the region's landscape. The northern portion is composed of
glaciated terrain, with expansive plains and hills in the area surrounding the Great Lakes. In some areas
(particularly northern Minnesota), extensive peatlands have formed on glacial lake plains. Most of the
Northern Appalachians was also glaciated, resulting in mountainous or hilly terrain with intermixed
plains. The Southern Appalachian region is also hilly, with wide valleys, plateaus, and irregular plains.
Northern boreal and broadleaf deciduous forests transition to broadleaf and needleleaf forest
communities toward the south.
The climate of the Eastern Mountains and Upper Midwest is characterized by a range of temperatures
and precipitation. Cold winters and relatively short summers with a mean of 20 to 47 inches of
precipitation characterize the areas surrounding the Great Lakes. Moving eastward, the climate is
slightly warmer with increased annual precipitation totals ranging from 35 to 60 inches. Average annual
temperatures range from 39 to 49°F. The southern portion of the ecoregion is both warmer and wetter,
with annual precipitation of about 40 to 80 inches and average annual temperatures ranging from 52 to
59°F.
Forests in the Eastern Mountains and Upper Midwest were extensively cleared in the 18th and 19th
centuries for agricultural and industrial production. Today, much of the area within this ecoregion is
highly populated and major manufacturing, including chemical, steel and power production may be
found in metropolitan areas throughout the ecoregion. However, much of the northern part of the
region remains forested and relatively undeveloped.
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Chapter 4 \ Ecoregion and Wetland Type Results
Wetlands are relatively abundant in the northern portion of the ecoregion, owing to the climate and
glaciated terrain. In contrast, wetlands are not as dominant a landscape feature in the southern portion.
Forested wetlands are the most common type found throughout the ecoregion, and include forested
swamps, bottomland hardwoods, wetflatwoods in
the plains of the Great Lakes, and boreal coniferous
forested bogs. Depressional wetlands, such as small
ponds, kettle depressions, and vernal pools, form in
low-lying areas left from retreating glaciers, areas
with karst topography, and other landscape
characteristics. Freshwater marshes are common
around the Great Lakes and other water bodies
throughout the ecoregion, while salt marshes may be
found along the New England coastline.
Forested wetland in New Hampshire (site NWCA11-
2163). Photo courtesy of New Hampshire Department
of Environmental Services.
Well known wetland complexes in the Eastern
Mountains and Upper Midwest include the Boundary
Waters area of Northern Minnesota, Horicon Marsh
in Wisconsin, and Montezuma Swamp in the Finger
Lakes region of New York.
Summary of findings
A total of 152 randomly selected sites were sampled in the Eastern Mountains and Upper Midwest
ecoregion during the 2011 field season, representing 19,956,668 acres. Of the total number of Eastern
Mountains and Upper Midwest sites sampled, 55 are inland herbaceous wetlands, representing
3,762,089 acres, and 83 are inland woody wetlands, representing 16,165,406 acres. Estuarine wetlands
in the Eastern Mountains and Upper Midwest included 14 sites, representing 29,173 acres. Detailed
results for estuarine wetland types are reported in the Estuarine Wetlands section of this chapter.
Biological Condition
For all wetland types assessed in the Eastern Mountains and Upper Midwest (Figure 4-5), 52% of the
estimated wetland area is in good condition; 11% is in fair condition, and 37% is in poor condition based
on the VMMI. Inland herbaceous wetlands have 62% of assessed wetland area in good condition, 17% in
fair condition, and 22% in poor condition (Figure 4-6). Compared to the inland herbaceous wetlands, a
slightly lower proportion of inland woody wetlands are in good and fair condition, 50% and 9%,
respectively, while a greater proportion of inland woody wetlands are in poor condition, 41% (Figure 4-
7).
Indicators of Stress
For all wetland types assessed in the Eastern Mountains and Upper Midwest, surface hardening,
vegetation removal, ditching, and soil phosphorus concentration are the indicators with the greatest
proportion of wetland area at high stressor levels (Figure 4-5). However, the majority of wetland area
throughout the ecoregion had low levels for each of the stressors. Key findings include:
• Hardening has high stressor levels for 22% of wetland area, while 23% and 55% have moderate
or low levels, respectively.
• Vegetation removal stressor levels are high in 17% of wetland area, moderate in 15% of wetland
area, and low in 68% of wetland area.
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Chapter 4 | Ecoregion and Wetland Type Results
• Ditching is high in 15% of the wetland area, moderate in 8%, and low in 77%.
• Soil phosphorus concentrations in this ecoregion are at high stressor levels for 13% of wetland
area, moderate for 22% and low for 63% of wetland area. Soil phosphorus could not be assessed
for 1% of the wetland area due to difficulties collecting soil samples at some sites.
For inland wetland types assessed within the Eastern Mountain and Upper Midwest ecoregion (Figures
4-6 and 4-7), data show:
• The most prevalent stressors at high levels for inland herbaceous wetlands are soil phosphorus
(35% of wetland area), vegetation removal (18%), ditching (14%), hardening (12%), and
damming (12%).
• The most prevalent stressors at high levels for inland woody wetlands are hardening (25% of
wetland area), vegetation removal (17%), and ditching (15%).
• High stressor levels for soil phosphorus are found at a greater proportion of wetland area for
inland herbaceous wetlands (35%) than inland woody wetlands (8%). It should be noted that 8%
of the herbaceous wetlands could not be assessed for soil phosphorus due to difficulties
collecting soil samples at some sites. Less than 1% of woody wetlands were not assessed.
• Hardening is a more prevalent stressor for inland woody wetlands, with 25% of wetland area
having high-stressor levels compared to 12% for inland herbaceous wetlands.
Eastern Mountains and
Upper Midwest
19.956.668 Acres
Vegetation MMI
H52%
37%
Vegetation Removal
68%
Vegetation Replacement
H
81%
I 16%
20 40 60 80
Percent Area
100 0
MMI
I 1 GoodC^l Fair I
Vegetation Stressors
20 40 60 80
Percent Area
Physical Stressors
Poor
I LowC
[ Moderate!
100 0
High
LowC
Moderate!
I High
20 40 60 80
Percent Area
Soil Stressors
I I Low I I Moderate
^•1 Highi i Unassessed
Non-Native Plant Species
l l Low l l Moderate
^H High^H Very High
Figure 4-5. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the Eastern
Mountains and Upper Midwest. Bars show the percentage of wetland area within a condition or stressor class. Error bars
represent 95% confidence intervals.
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Chapter 4 \ Ecoregion and Wetland Type Results
Eastern Mountains and
Upper Midwest
Inland Herbaceous Wetlands 3.762,089 Acres
22%
Vegetation Removal
Vegetation MMI
62%
18%
Veoetatkjn Replacement
93%
Damming
15%
Soil Phosphorus
1 42%
35%
Heavy Metals
1 57%
H 35%
I 8%
Nonnative Plant Species
] 59%
20 40 60 80
Percent Area
MMI
Poor I
Fair
Unassessed
100 0 20 40 60 80
Percent Area
Physical Stressors
I Lewi I Moderate
I Highl I Unassessed
100 0
20 40 60 80
Percent Area
Soil Stressors
I I LowC
^m HighC
Moderate
3 Unassessed
Vegetation Stressors
I I Lowl l Moderate
^^B Might 1 Unassessed
Nonnative Plant Species
I Lowl I Moderate
gh^H VeryHigh
Figure 4-6. NWCA 2011 survey results for the inland herbaceous wetland type across the Eastern Mountains
and Upper Midwest. Bars show the percentage of wetland area within a condition or stressor class. Error bars represent
95% confidence intervals.
Eastern Mountains and
Upper Midwest
Inland Woody Wetlands 16.165.406 Acres
Vegetation MMI
50%
41%
Vegetation Removal
I 1 1 66%
Vegetation Replacement
78%
18%
Nonnative Plant Species
% 78%
0 20 40 60 80 100 0
Percent Area
20 40 60 80 100 0
20 40
80 100
I Good I I Fair
I Poorf I Unassessed
MMI
Vegetation Stressors
i i I nwi i Moderate
^H Highi i Unassessed
Percent Area
Physical Stressors
i i Lowi i Moderate
^^1 Highl 1 Unassessed
Percent Area
Soil Stressors
I I Lowl l Moderate
^H Highl i Unassessed
Nonnative Plant Species
I- —i Lowl I Moderate
^H High^H VeryHigh
Figure 4-7. NWCA 2011 survey results for the inland woody wetland type across the Eastern Mountains and
Upper Midwest. Bars show the percentage of wetland area within a condition or stressor class. Error bars represent 95%
confidence intervals.
National Wetland Condition Assessment 2011
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Highlight
Establishing a Baseline for Ohio's Valuable Wetland Resources: A National Wetland
Condition Assessment Intensification
Brian Gara, Ohio EPA
Objectives: According to previous estimates, Ohio has lost approximately 90% of its original, pre-
settlement wetland habitat (Dahl 1990). The main goal of this intensification project was to perform a
statewide survey to determine the current ecological condition of wetlands in Ohio that will serve as a
baseline for future studies of this valuable and diminishing resource. A randomly-selected sample of 50
wetlands were studied between 2011 and 2014 to generate the data necessary to determine condition
and to:
(1) Compare and contrast the results NWCA 2011 with results generated from Ohio's Level 1, 2, and 3
wetland assessment methodologies.
(2) Identify differences in how NWCA and Ohio
field methods assess wetland conditions that
will help inform monitoring protocols for future
state and national wetland condition
assessments.
(3) Develop a plan to consistently repeat this
statewide analysis on a regular schedule to
illustrate long-term trends in both wetland
quantity and quality in Ohio.
Protocols and Methods Used: Eleven wetland
sites were sampled in Ohio for the 2011 NWCA,
following the national NWCA protocols. An
additional 39 wetland sites were sampled over
the course of four field seasons (2011-2014)
using the national protocols and other wetland
methodologies previously developed by Ohio
EPA. Because the sample design is area-
weighted, a large proportion of the sites
included in Ohio's intensification study are
located in the northeastern part of the state,
where a majority of the remaining wetland
area is contained (Figure 1). The other
assessment methodologies included the Ohio
Rapid Assessment Method for Wetlands
(ORAM), a simplified soil sampling protocol,
and expanded identification and collection of
all unique bryophyte species found within
NWCA vegetation plots to calculate metrics for bryophytes. From these data, an ORAM score, a
• NWCA Sues | | County Boundaries
• Ohio Intensification Sites
Figure 1. All Ohio NWCA and intensification sites included in
the study.
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Vegetation Index of Biotic Integrity (VIBI), and a recently developed vegetation analysis called the VIBI-
Floristic Quality (VIBI-FQ), were calculated for each site. The VIBI-FQ is a simplified analysis of vegetation
based on two equally-weighted metrics calculated for diversity and dominance (Gara 2013). Ohio utilized
proposed bryophyte metrics in order to explore the utility of bryophyte taxonomic group systems as a
potential measure of ecological condition. The metrics include (1) the proposed Moss Quality Assessment
Index (Moss QAI); (2) the number of bryophyte species; and (3) the number of bryophyte genera.
What They Found: The 2011-2014
intensification project provided a unique
opportunity to survey a random sample of
wetlands in Ohio. Using the data
collected, Ohio has completed ORAM,
VIBI and VIBI-FQ assessments, which all
suggest that Ohio wetland resources are
in generally good ecological condition.
Both VIBI and VIBI-FQ assessments
resulted in approximately half of the
wetlands within the "Excellent" or "Good"
ecological condition ranges, while the
ORAM assessment resulted in over half of
wetlands within that upper range (Table
1). This is higher than expected, given the
amount of wetland loss experienced
historically.
Wetland
Condition
"Poor"
"Fair"
"Good"
"Excellent"
ORAM
7(14%)
15 (30%)
17 (34%)
11 (27%)
VIBI
11 (22%)
14 (28%)
7 (14%)
18 (36%)
VIBI-
FQ
8(16%)
16
(32%)
16
(32%)
8(16%)
Table 1. ORAM, VIBI, and VIBI-FQ score for all Ohio NWCA
intensification wetlands, based upon unweighted data and by
approximate ecological condition ranges which correspond to
Ohio's wetland anti-degradation categories.
Scatterpbt of VIBI-FQ vs ORAM: Ohio NWCA Intensification (2011-2014)
(N = 50 [11 NWCA Sites + 39 Ohio Intensification Sites])
This study further allowed for the comparison of VIBI-FQ with results from both ORAM and VIBI for all 50
sites. VIBI-FQ is shown to be highly correlated to both the level 2 (ORAM) and level 3 (VIBI) assessments
that have been part of the Ohio EPA wetland regulatory program for more than 10 years (Figure 2, Figure
3). Ohio EPA is considering making this new tool a preferred assessment technique for monitoring certain
wetland restoration projects.
The bryophyte metrics have been calculated for all 50 surveyed sites, and preliminary results have
shown a strong
statistical correlation
between the overall
diversity of bryophytes
present and the
ecological condition of
the wetland vascular
plant community.
Developing a
bryophyte index of
biotic integrity could be
extremely beneficial to
the state wetland
regulatory program
because most
bryophytes are present
year-round, unlike
most other indicators
100-
90-
80-
70-
60-
50-
40-
30-
20-
10-
0-
10
20
30
40
50
ORAM
60
70
SO
90 100
Figure 2. VIBI-FQ vs. ORAM.
for detailed biological
National Wetland Condition Assessment 2011
October 2015
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Scatterptot of VIBI-FQ vs VIBI: Ohio NWCA Intensification (2011-2014)
(M = 50 111 NWCA Sites + 39 Ohio Intensification Sites])
100-
90-
80-
70
60-
50-
40-
30-
20-
10-
0-
10
20
30
40
50
VIBI
60
70
80
90
100
Figures. VIBI-FQ vs. VIBI.
assessments. Ohio is still
analyzing the soils data,
with plans to compare
results to those from the
NWCA; additionally, state-
specific protocol results
will be compared with
those generated from
NWCA's USA-RAM, VMMI,
buffer stressors, etc.
The Ohio intensification of
the NWCA has proven to
be a valuable first step
toward characterizing the
state's remaining wetland
resources. Several "lessons
learned" will allow Ohio to
streamline field protocols
when conducting future
state surveys, and they have been considered in the context of future NWCA protocol revisions. Ohio
hopes to replicate this probabilistic wetland survey on a regular basis in order to track temporal trends in
both wetland quality and quantity, preferably in conjunction with future cycles of NWCA.
To learn more, contact Brian Gara (brian.gara@epa.ohio.gov; 614-836-8787), Ohio EPA, Division of
Surface Water, Wetland Ecology Group.
References:
Dahl, Thomas E. Wetlands losses in the United States, 1780's to 1980's. Report to the Congress. No. PB-
91-169284/XAB. National Wetlands Inventory, St. Petersburg, FL (USA), 1990.
Gara, Brian. 2013. The Vegetation Index of Biotic Integrity "Floristic Quality" (VIBI-FQ). Ohio EPA
Technical Report WET/2013-2. Ohio Environmental Protection Agency, Wetland Ecology Group,
Division of Surface Water, Columbus, Ohio.
Ohio Statewide Imagery Program (OSIP). 2006-2007. Ohio Office of Information Technology, Ohio
Geographically Referenced Information Program (OGRIP). http://ogrip.oit.ohio.gov/.
Soil Survey Staff, Natural Resources Conservation Service (NRCS), U.S. Department of Agriculture. Soil
surveys for each Ohio County available online from
http://soildatamart.nrcs.usda.gov/Survey.aspx?State=OH [Accessed 2009].
U. S. Fish and Wildlife Service. 2010. National Wetlands Inventory for Ohio. U.S. Department of the
Interior, Fish and Wildlife Service, Washington, D.C. http://www.fws.gov/wetlans/.
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National Wetland Condition Assessment 2011
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Highlight
Minnesota's Intensification Project: NWCA Intensification Survey Helps Reveal
Important Regional Variation in Minnesota
Michael Bourdaghs, Minnesota Pollution Control Agency
Minnesota is known as the "land of 10,000 lakes," but wetlands also cover 10.62 million acres of the
state (Kloiber and Norris 2013). By any measure it is a water rich state, however, surface water resources
(and the pressures they face) do not occur evenly throughout.
As with many other states, a variety of landscapes occur in Minnesota, with three widely recognized
ecoregions present. As described by Omernik level II ecoregions they are (Figure 1):
• Mixed Wood Shield: Covering the northeast and
north-central areas of the state, the Mixed Wood
Shield is characterized by a mix of conifer and
hardwood forests. Wetlands are extensive and
agricultural and urban development is very low
compared to the rest of the state, with forestry and
mining as top industries.
• Mixed Wood Plains: This ecoregion occupies a central
transitional zone between the drier/warmer former
prairies to the south and west and the wetter/cooler
northern forests. Historically, much of the ecoregion
was covered by hardwood forests. Currently,
agricultural development is widespread and the
majority of Minnesota's population is concentrated
here.
• Temperate Prairies: Once covered by tallgrass prairie,
oak savanna, and aspen parkland, the Temperate
Prairies ecoregion is now predominantly used for
agricultural production.
•I Mixed Wood Shield
: I Mixed Wood Plains
] Temperate Prairies
Figure 1. Omernik Level II ecoregions in Minnesota.
Across the state, approximately 50% of pre-settlement wetlands remain. However, development and
wetland drainage history vary by ecoregion. Most of the pre-settlement wetlands remain in the Mixed
Wood Shield, with counties in the ecoregion retaining 92% of wetland acreage on average (Anderson and
Craig 1984). Remaining wetland acreage is much lower in the Mixed Wood Plains, with counties
averaging 40%. Wetland losses are even greater in the Temperate Prairies, where on average only 5% of
each county's pre-settlement wetlands remain.
The Minnesota Pollution Control Agency took the opportunity to conduct an intensification survey in
conjunction with the NWCA. Considering the known variation in development, drainage history, and
wetland quantity between ecoregions, Minnesota chose a sampling approach that reduced field sampling
National Wetland Condition Assessment 2011
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Wetland Vegetation Condition
| Exceptional ||Good Fair H
Target Wetland Population
Extent Estimate
Wetland Acres 9,679,441
95%CL(Acre5) (+/-) 421,388
Wetland Acres 7,241,813
95% CL (Acres) (+/-) 180,315
33.6%
% of statewide
% of statewide
wetland extent
20 40 60
% Wetlands
80
830,135
-/-) 93,703
4.3%
Figure 2. Wetland vegetation condition in Minnesota (statewide and by ecoregion).
at individual sites and focused on vegetation condition. This allowed them to increase the number of
sites sampled and achieve a representative sample for each of the ecoregions.
Statewide, wetland vegetation condition was high overall (Figure 2), with an estimated 49% of wetlands
assessed as Exceptional and another 18% in Good condition. Correspondingly, degraded vegetation
conditions were low with 23% assessed as Fair and only 10% in Poor condition. These are encouraging
October 2015
National Wetland Condition Assessment 2011
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results. The clear majority of Minnesota's wetlands have either no detectable or only minor impacts to
their vegetation.
The ecoregion results, however, reveal a disparity of vegetation conditions (Figure 2) that correspond
with the broad patterns of human development. Wetland vegetation condition in the largely intact
Mixed Wood Shield was very high, with an estimated 64% in Excellent condition. Conversely, in the
heavily developed Mixed Wood Plains and Temperate Prairies, vegetation was predominately degraded-
about 80% of wetlands were assessed as Fair or Poor.
The predominant stress indicator in these two ecoregions was non-native invasive plant species that can
tolerate higher degrees of human impacts, out-compete native species, and produce persistent litter
thereby altering native plant communities and driving out native species (Galatowitsch 2012). The most
widespread non-native invasives were Reed canary grass (Phalaris arundinacea) and the invasive Cattails
(Typha angustifolia and Typhaxglauca). High non-native cover was strongly associated with all types of
stressors estimated in the survey. For example, non-native cover was high at approximately 95% of
wetlands that had at one time been plowed and left to revert back to natural wetland (about 14-16% of
the wetland area in the Mixed Wood Plains and Temperate Prairie ecoregions). However, 9%-12% of the
wetland area had moderate to high non-native species cover when all other stressor categories were low
or absent, suggesting that non-native invasives may also be acting independent of other types of human
impacts.
Approximately 75% of Minnesota's wetlands occur in the Mixed Wood Shield and the high level of
condition found there drives the statewide results, largely masking the degraded conditions in the Mixed
Wood Plains and Temperate Prairies. While estimating overall wetland condition on a statewide basis is a
fundamental scale for monitoring the long term status and trends of wetlands, in Minnesota, the regional
scale provides a much more complete story.
To learn more, contact Michael Bourdaghs (Michael.Bourdaghs@state.mn.us; 651-757-2239), Minnesota
Pollution Control Agency, Surface Water Monitoring Division.
References:
Anderson, J.P. and W.J. Craig. 1984. Growing energy crops on Minnesota's wetlands: The land use
perspective. University of Minnesota, Minneapolis, MN.
Galatowitsch, S.M. 2012. Why invasive species stymie wetland restoration. Society of Wetland
Scientists Research Brief. No. 2012-0001.
Kloiber, S.M. and D.J. Norris. 2013. Status and Trends of Wetlands in Minnesota: Wetland Quantity
Trends from 2006 to 2011. Minnesota Department of Natural Resources, St. Paul, MN.
National Wetland Condition Assessment 2011
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Chapter 4 \ Ecoregion and Wetland Type Results
Interior Plains
Landscape setting of the ecoregion
The NWCA Interior Plains ecoregion combines the Northern
Plains, Temperate Plains, and Southern Plains NARS
ecoregions. The region extends from northern Montana to
southern Texas and from the Rocky Mountains east to
western Ohio.
The terrain consists of smooth and irregular plains
interspersed with tablelands and low hills. The northern
portion has also been shaped by glacial deposits from the last
Ice Age. Great prairie grasslands were once a dominant
feature of this region, but have been replaced by other
vegetation as land was developed for other uses. Mixed prairie and forest communities occur along the
eastern edge of the region.
The climate is generally dry and temperate. Annual precipitation ranges from 10 to 43 inches, with the
eastern Temperate Plains being wetter than the Northern and Southern Plains. Temperatures vary more
widely with average annual temperatures between 45°F and 79°F in the Southern Plains and 36°F and
45°F in the Northern Plains.
Farming and livestock production is an important and dominant economic activity throughout the
region. Mining, petroleum and natural gas production have a long history in the southern portion of the
region and are increasingly prevalent in the north.
Terrain, climate, and land use have influenced the types of wetlands commonly found in the region
today. In the north and central parts of the region, depressional wetlands called prairie potholes are a
prevalent feature of the landscape. Prairie potholes typically have a mix of wetland vegetation, varying
from submerged and floating plants found in areas
with deeper water near the center of the pothole, to
bulrush, cattails, and other marsh plants occurring
along the edge. In the southern parts of the region, a
type of depressional wetland called a playa wetland
(also commonly known as a playa lake) is prevalent.
Prairie potholes and playa wetlands provide
important habitat for migrating waterfowl and other
wildlife by, among other things, providing a source of
water and food in these drier parts of the country.
Prairie potholes and playa wetlands also are
important sources of groundwater recharge. Wet
meadows, marshes, and forested wetlands
associated with major river systems like the Missouri
River are also commonly found within this region.
Prairie pothole sampled in North Dakota (site NWCA11-
ND-5032). Photo courtesy of NDSU.
Well known wetland complexes in the Interior Plains
include the Prairie Pothole Region, the Sandhills and
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Chapter 4 \ Ecoregion and Wetland Type Results
Rainwater Basin in Nebraska, the Cheyenne Bottoms in Kansas, as well as a well-defined region of playas
that includes parts of Nebraska, Colorado, Kansas, Oklahoma, Texas, and New Mexico.
Summary of findings
A total of 156 randomly selected sites were sampled in the Interior Plains during the NWCA 2011 field
season, representing 7,659,166 acres. Of the total number of Interior Plains sites sampled, 115 are
inland herbaceous wetlands, representing 4,598,831 acres, and 41 are inland woody wetlands,
representing 3,060,335 acres.
Biological Condition
For all wetland types assessed in the Interior Plains (Figure 4-8), 44% of the estimated wetland area is in
good condition; 36% is in fair condition, and 19% is in poor condition based on the VMMI. The
proportion of wetland area in good condition for inland herbaceous wetlands is much larger, 60%, than
it is for inland woody wetlands, where only 20% are in good condition (Figures 4-9 and 4-10). The
proportion of woody wetlands in fair condition, however, is much larger, 59%, than it is for herbaceous
wetlands, 21%. The proportion of area in poor condition is similar for both herbaceous (18%) and woody
(21%) wetlands.
Indicators of Stress
For all wetland types assessed in the Interior Plains, vegetation removal, surface hardening, ditching,
and nonnative plants are the indicators with the greatest wetland area at high stressor levels (Figure 4-
8). While the majority of stressors in this ecoregion are at low levels, both vegetation removal and
nonnative plant stressors have a greater proportion of wetland area at high and very high levels than
low. Key findings include:
• Vegetation removal is at high stressor levels in 44% of the wetland area, moderate levels in 14%,
and low levels in 42%.
• Hardening is high in 35% of wetland area, compared to 15% and 49% of wetland area at
moderate or low stressor levels, respectively.
• Ditching stressor levels are high in 28% of the wetland area, moderate in 10%, and low in 62%.
• Damming is at high stressor levels in 26% of the wetland area, at moderate levels in 4%, and at
low levels in 70%.
• The nonnative plant stressor has very high and high stressor levels in 21% and 25% of the
wetland area, respectively, moderate levels in 26% of wetland area, and low levels in 27%.
• Soil phosphorus concentration is at low stressor levels, for most of the wetland area in the
region, 71%. However, it is not assessed for 23% of the area due to difficulties in collecting soil
samples or because some soil samples for this ecoregion were not analyzed using NWCA lab
protocols. Similarly, heavy metal concentrations are at low stressor levels for 61% of wetland
area, but is not assessed for 23% of the area.
For inland wetland types assessed within the Interior Plains ecoregions (Figure 4-9 and 4-10), data show:
• Inland herbaceous wetlands have several indicators at high stressor levels for large proportions
of assessed wetland area. These include hardening (56% of wetland area), vegetation removal
(55%), ditching (41%), and vegetation replacement (30%). In addition, 63% of inland herbaceous
wetlands have high or very high levels for the nonnative plant stressor.
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Chapter 4 | Ecoregion and Wetland Type Results
• The indicators of stress with the largest proportion of wetland area at high stressor levels for
inland woody wetlands are damming (37%) and vegetation removal (28%). Wetland area for
woody wetlands at high or very high levels for the nonnative plant stressor is 20%.
• For most of the stressors measured, a greater proportion of herbaceous wetland area has high
stressor levels relative to the woody wetlands. The exception is the damming stressor, which is
at high levels in 37% of woody wetlands compared to 18% of herbaceous wetlands.
• While the majority of herbaceous wetlands have low stressor levels for soil phosphorus (55% of
wetland area) and heavy metals (60%), it should be noted that 38% of the wetland area was not
assessed due to difficulties in collecting soil samples or because some soil samples for this
ecoregion were not analyzed using NWCA lab protocols.
Interior Plains
7.659.166 Acres
MMI
20 40 60 80 100 0 20 40 60 80
Percent Area Percent Area
Physical Stressors
I Good I 1 Fair I
Poor
LowC
I Moderate!
Vegetation Stressors
I I Low i i Moderate I
High
100 0 20 40 60 80 100
Percent Area
Soil Stressors
High I 1 Low I 1 Moderate
^H Hlghi i Unassessed
Non-Native Plant Species
I Low i i Moderate
High ^H Very High
Figure 4-8. NWCA 2011 survey results for the wetlands (i.e., all target wetland types) across the Interior
Plains. Bars show the percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence
intervals.
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Chapter 4 \ Ecoregion and Wetland Type Results
Interior Plains
Inland Herbaceous Wetlands 4,598,831 Acres
Vegetation MMI
60%
47%
20 40 60 80
Percent Area
100 0
80 100
MMI
I Poor i
Fair
Unassessed
Percent Area
Physical Stressors
I Lowi I Moderate
I Highi i Unassessed
Percent Area
Soil Stressors
LowC
High[
I Moderate
] Unassessed
Vegetation Stressors
I -I I owl I Moderate
^^H H»jhi 1 Unassessed
Nonnative Plant Species
I I Lowi i Moderate
^M •-;:'-•• Very High
Figure 4-9. NWCA 2011 survey results for the inland herbaceous wetland type across the Interior Plains. Bars
show the percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence intervals.
Interior Plains
Inland Woody Wetlands 3,060.335 Acres
0%
0%
0%
0%
Soil Phosphorus
HH
Heavy Metals
I 34%
66%
Nonnative Plant Species
I =] 1 62%
MMI
20 40 60 80
Percent Area
I GoodCZZ] Fair
I Pnnri ~1 Unassessed
100 0 20 40 60 80
Percent Area
Physical Stressors
i i LQWI i Moderate
^H Highi i Unassessed
100 0
20
40
60
80
100
Vegetation Stressors
I I nwi i Moderate
Hinhl I Unassessed
Percent Area
Soil Stressors
Moderate
Unassessed
Nonnative Plant Species
I I Low i i Moderate
^H High^H Very High
Figure 4-10. NWCA 201 I survey results for the inland woody wetland type across the Interior Plains. Bars show
the percentage of wetland area within a condition or stressor classes. Error bars represent 95% confidence intervals.
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Chapter 4 | Ecoregion and Wetland Type Results
West Ecoregion
Landscape setting of the ecoregion
The NWCA West ecoregion combines the Western Mountain
and Xeric NARS ecoregions. The region includes the western
parts of Texas, New Mexico, Colorado, Wyoming, and
Montana to the Pacific Coast.
The West ecoregion is topographically diverse, including large
extensive mountain ranges, plateaus and high-relief
tablelands, lowland plains with hills and low mountains,
isolated mountains, and intermountain basins and valleys.
Coastal mountains are bordered by coastal plains and include
important estuaries along the margins of the Pacific Ocean.
The topographic and climatic diversity of the West ecoregion results in diverse plant communities. In the
drier parts of the region, native vegetation is dominated by grasses and shrubs, with relatively few large
trees. Desert and shrub-steppe ecosystems are found in the rain shadow of large mountain ranges, but
within the mountain ranges, vegetation communities include alpine tundra, mountain meadows, valley
grasslands, shrublands, and hardwood riparian systems. Foothills and mountain ranges are often
dominated by expansive forests.
The climate varies widely across the West ecoregion. In the Xeric region, conditions tend to be hot and
dry with a long summer dry season. Average annual temperatures range from 32 to 75°F. Average
annual precipitation throughout the region ranges from 2 to 40 inches but varies widely both spatially
and temporally. The Western Mountain region tends to be cooler and more humid than the Xeric region,
with average annual temperatures ranging from 32 to 55°F and average annual precipitation ranging
from 16 to 240 inches. At higher elevations, most precipitation falls as snow.
Much of the region is federally-owned land, some of which is used for recreation purposes. Grazing is
widespread and timber production is a leading industry in forested areas. Agricultural production varies
widely across the region with climate—ranging from citrus, subtropical, and tropical fruits to vegetables
and horticultural crops, to irrigated and dry-farmed
grain and forage crops.
Wetlands comprise a relatively small, but important,
proportion of land area in the West, and vary widely
with geography and climate. They support a variety
of habitats, including the salmon fishery, and are key
contributors to water supplies, especially in the drier
regions. In relatively dry basins and valleys, wetlands
are concentrated along rivers, streams, and in
abandoned river channels. Additionally, wet
meadows and emergent marsh complexes are found
in large basins and valleys. Snowmelt- and
groundwater-fed wetlands such as wet meadows,
fens, seeps, and forested wetlands are found in
mountain ranges. Tidal salt and freshwater marshes,
wet meadows and forests are found along the coast.
Wet meadow along riparian corridor in Yellowstone
National Park, WY (site NWCA11-2790). Photo courtesy
of Colorado Natural Heritage Program.
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Chapter 4 \ Ecoregion and Wetland Type Results
Large estuaries, such as the San Francisco Bay and Puget Sound, are familiar to many people, but
extensive wetland complexes are also associated with major rivers and lakes throughout the region
(e.g., the Colorado, Columbia, Sacramento, and Snake Rivers, the Great Salt Lake).
Summary of findings
A total of 146 randomly selected sites were sampled in the West ecoregion during the NWCA 2011 to
characterize the condition of 3,647,060 acres. Of the total number of West sites sampled, 70 are inland
herbaceous wetlands, representing 1,488,139 acres, and 51 are inland woody wetlands, representing
1,985,936 acres. Estuarine wetlands in the West total 25 sites, representing 172,985 acres. Detailed
results for estuarine wetland types are reported in the Estuarine Wetlands section of this chapter.
Biological Condition
For all wetland types assessed in the West (Figure 4-11), 21% of the estimated wetland area is in good
condition; 18% in fair condition, and 61% in poor condition based on the VMMI (see Chapter 2 for
details on the VMMI). Inland herbaceous wetlands have an estimated 25% of wetland area in good
condition, 32% in fair condition, and in 43% poor condition (Figure 4-12). Inland woody wetlands have
an estimated 21% of wetland area in good condition, 8% in fair condition, and 71% in poor condition
(Figure 4-13).
Indicators of Stress
For all wetland types assessed in the West, ditching, nonnative plants, surface hardening, and
vegetation removal are the indicators with the greatest wetland area at high stressor levels (Figure 4-
11). Each of these stressors have a greater proportion of wetland area at high levels than low. Key
findings include:
• Ditching is at high stressor levels for 76% of wetland area, moderate for 1% and low for 22%.
• The nonnative plant stressor is at very high or high stressor levels for 72% of the wetland area,
and at moderate and low levels for 15% and 14%, respectively.
• Hardening stressor levels are high for 70% of wetland area, moderate for 7%, and low for 23%.
• Vegetation removal stressor levels are high for 61% of the wetland area, moderate for 6%, and
low for 33%.
• Damming is at high stressor levels for 32% of wetland area, moderate for 1%, and low for 67%.
For inland wetland types assessed within the West ecoregion (Figures 4-12 and 4-13), data show:
• The indicators of stress with the greatest percent wetland area at high levels for inland
herbaceous wetlands are ditching (78% of wetland area), hardening (70%), damming (61%), and
vegetation removal (47%). High or very high levels for the nonnative plant stressor total 73% of
wetland area.
• The indicators of stress with the greatest percent wetland area at high levels for inland woody
wetlands are vegetation removal (76% of wetland area), ditching (75%), and hardening (75%).
High or very high levels for the nonnative plant stressor total 74% of wetland area.
• Inland herbaceous and woody wetland area have similar percentages of wetland area at high
stressor levels for ditching, hardening, and nonnative plant indicators. Both wetland types also
have large percentages of wetland area at low stressor levels for vegetation replacement,
filling/erosion, and soil phosphorus indicators.
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Chapter 4 | Ecoregion and Wetland Type Results
• Inland woody wetlands have a greater proportion of wetland area at high stressor levels for
vegetation removal, 78%, than inland herbaceous wetlands, which have 47%.
• High stressor levels for damming are found in 61% of inland herbaceous wetland area, but only
10% of inland woody wetland area.
• The majority of inland herbaceous wetlands have low stressor levels for heavy metals (80% of
wetland area), which is greater than the percentage for inland woody wetlands. Among woody
wetlands, only 20% of wetland area have low stressor levels, while 69% have moderate and 4%
have high stressor levels for the heavy metals indicator.
West
3.647.059 Acres
61%
I 2% Vegetation Replacement
1%
20 40 60 80 100 0
Percent Area
MMl
I 1 Good I 1 Fairl
Vegetation Stressors
Poor
20 40 60 80
Percent Area
Physical Stressors
I I Low I I Moderate^H
100 o
20 40 60 80 100
Percent Area
Low
Moderate!
High
Soil Stressors
I High I 1 Low I 1 Moderate
^^H Highi 1 Unassessed
Non-Native Plant Species
I I Low I I Moderate
Figure 4-11. NWCA 201 I survey results for the wetlands (i.e., all target wetland types) across the West. Bars
show the percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence intervals.
October 2015
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Chapter 4 \ Ecoregion and Wetland Type Results
0%
West
Inland Herbaceous Wetlands 1,488,139 Acres
Vegetation MMI
25%
432%
43%
Vegetation Removal
•{ 50%
47%
Vegetation Replacement
E
0%
~^=r-
I 1%
~i=l-
-H 6%
^H6%
Damming
1 1 39%
Ditching
— 1 21%
Hardening
1 24%
Filling/Erosion
1 "l 1
77%
417%
Soil Phosphorus
90%
42%
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
Percent Area Percent Area Percent Area
MMI
I GoodC
I PoorC
] Fair
Unassessed
Physical Stressors
I Lowi i Moderate
I Highl I Unassessed
Vegetation Stressors
Lovui i Moderate
Highi i Unassessed
Soil Slressors
I I Low I I Moderate
^^B Highl I Unassessed
Nonnative Plant Species
i i Low i 1 Moderate
^H High^H Very High
Figure 4-12. NWCA 201 I survey results for the inland herbaceous wetland type across the West. Bars show the
percentage of wetland area within a condition or stressor class (good, fair, and poor. Error bars represent 95% confidence
intervals.
West
Inland Woody Wetlands 1,985,936 Acres
121%
Vegetation MMI
115%
71'X
Vegetation Removal
I 9%
| 76%
Vegetation Replacement
1 2%
98%
0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100
Percent Area Percent Area Percent Area
MMI Physical Stressors
Good I I Fair
^H Poor i i Unassessed
Vegetation Stressors
I I I owl l Moderate
••I Highi 1 Unassessed
I Lowl I Moderate
Highi i Unassessed
Soil Stressors
I I Low i i Moderate
^H Highi i Unassessed
Nonnative Plant Species
I Lowi i Moderate
gh ^^H Very High
Figure 4-13. NWCA 201 I survey results for the inland woody wetland type across the West. Bars show the
percentage of wetland area within a condition or stressor class. Error bars represent 95% confidence intervals.
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Chapter 4 | Ecoregion and Wetland Type Results
Estuarine Wetlands
Landscape setting for estuarine wetlands
Estuarine wetlands occur along the coastal areas of
the conterminous U.S. They can be found in three of
the NWCA Ecoregions: Coastal Plains, Eastern
Mountains and Upper Midwest, and the West.
Estuarine wetlands—tidal systems that are saline or
brackish—may be dominated by herbaceous
emergent vegetation or by shrubs or trees. Estuarine
wetlands occur predominantly along coastal areas of
the Coastal Plains Ecoregion, while fewer estuarine
wetlands occur along the west and northeastern
coasts of the U.S. Because few NWCA 2011 sites
occurred in western and northeastern estuarine
wetlands, results for estuarine wetlands are
presented only by wetland type—estuarine
herbaceous and estuarine woody.
Tidal salt and brackish marshes are found along the
nation's coasts. Shrub/tree dominated wetlands are
often located in high intertidal zones along coasts
where they are exposed to less saltwater and there
are greater influxes of freshwater from the
surrounding landscape. In the most southern part of
the Eastern coast, mangrove swamps are found in
association with coastal marshes.
Summary of findings
Salt marsh in Florida (site NWCA11-3069). Photo
courtesy of University of Florida.
The 327 randomly selected estuarine wetland sites that were sampled in the NWCA represent an
estimated 5,485,646 acres. Estuarine wetlands are reported separately for herbaceous and woody
types. Estuarine herbaceous wetlands (salt marshes) are evaluated based on 258 randomly selected
sites, which represented an estimated 4,987,824 acres. Estuarine woody wetlands (deciduous or
evergreen woody dominated wetlands, mangrove swamps) represent a smaller proportion of the
wetland area, 497,821 acres, based on evaluation of 69 sites.
Biological Condition
Estuarine herbaceous wetlands have an estimated 58% of wetland area in good condition, 17% in fair
condition, and 26% in poor condition (Figure 4-14) based on the VMMI (see Chapter 2 for details).
Estuarine woody wetlands have an estimated 59% of wetland area in good condition, 20% in fair
condition, and 22% in poor condition (Figure 4-15).
Indicators of Stress
Stressor level is generally low for all indicators of stress for both estuarine herbaceous and estuarine
woody wetlands. For the estuarine herbaceous wetlands (Figure 4-14) the indicators of stress with the
greatest estimated wetland area at high stressor levels are ditching (18%), surface hardening (11%), and
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Chapter 4 \ Ecoregion and Wetland Type Results
damming (10%). In addition, high or very high levels for the nonnative plant stressor total 24% of
estuarine herbaceous wetland area. Soil phosphorus stressor levels are low for 37% of herbaceous
wetland area, moderate for 28%, and high for 2%. Soil phosphorus and soil heavy metal stressors are
not assessed for 33% of the wetland area, due to difficulties collecting soil samples at some sites.
In the estuarine woody wetlands (Figure 4-15), the indicators of stress with the greatest estimated
wetland area at high stressor levels are ditching (18% of wetland area) and hardening (13%). The heavy
metals stressor is at low levels for 44% of wetland area, but at moderate levels for 55%. Less than 1% of
estuarine woody wetland area is at high stressor levels for heavy metals.
Estuarine Herbaceous Wetlands 4,987,824 Acres
Vegetation MMI
58%
93%
Vegetation Replacement
97%
0%
Damming
0%
10%
18%
11%
Filling/Erosion
93%
Soil Phosphorus
37%
I 28%
20 40 60 80
Percent Area
MMI
100 0 20 40 60 80
Percent Area
Physical Stressors
Good[
I PoorC
] Fair
Unassessed
LowC
High:
Moderate
] Unassessed
Vegetation Stressors
i i I nwi 1 Moderate
^^H Highi ~1 Unassessed
100 0 20 40 60 80
Percent Area
Soil Stressors
I I Low I I Moderate
^H Highi I Unassessed
Nonnative Plant Species
I I Low I I Moderate
^B High^H Very High
100
Figure 4-14. NWCA 201 I survey results for estuarine herbaceous wetland types across all coastal areas of the
conterminous U.S. Bars show the percentage of wetland area within a condition or stressor class. Error bars represent 95%
confidence intervals.
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Chapter 4 | Ecoregion and Wetland Type Results
Estuarine Woody Wetlands 497,821 Acres
Vegetation MMI
1 1 59°/<
1 1 1 22%
Vegetation Removal
1 1 —
^ 19% 91%
0%
Vegetation Replacement
I 1
0%
Damming
0% 100%
0%
Ditching
I 1 1
JH3% "»%
I I 1 1 8%
Hardening
I 1 1
bd- — 111% 76%
B 1 13%
Filling/Erosion
I 1 1
bd 1 10% 83%
bF— i 7%
Soil Phosphorus
E
_=] 1 13%
^f 1 9%
0%
I 1
I h
0%
0%
-1 1
' 77%
Heavy Metals
1 44%
I55
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Chapter 5 \ Summary and Next Steps
Chapter 5: Summary and Next Steps
Summary of Major Findings and Implications
The NWCA 2011 is the first national assessment of wetland ecological condition. This accomplishment
required an extraordinary amount of effort and cooperation between state, tribal, and federal partners
throughout its design and implementation. During the 2011 field season, more than 50 field crews
sampled 1,179 wetland sites across the country, using standardized protocols to collect information to
characterize wetland condition. Previous wetland monitoring and assessment studies have been
conducted at local and regional scales, or have focused on specific wetland types or ecological
properties, but none have evaluated wetland condition for a full range of wetland types across the
entire country. Thanks to the efforts of the field crews and many other partners, the NWCA collected
the most comprehensive set of biological, physical, and chemical data on wetlands across the U.S. This
national data set will provide valuable and previously unavailable information on the ecological
condition of a broad range of wetlands to policy makers, land managers, and scientists. This includes
important insight on wide-spread stressors impacting wetland biological condition, and the potential
improvement that could be seen nationally by reducing these stressors.
The NWCA 2011 found 48% of wetland area is in good condition, based on the national Vegetation
Multimetric Index (VMMI) developed for NWCA, while 32% of wetland area is in poor condition. Of the
four major ecoregions reported on by NWCA, the West had the lowest percentage of wetland area in
good condition at 21%. The Coastal Plains (50%), Eastern Mountains and Upper Midwest (52%), and
Interior Plains (44%) have similar percentages of area in good condition as the national estimates.
Nationally, vegetation removal, surface hardening (e.g., pavement, soil compaction), and ditching are
the most widespread of the indicators of stress evaluated in NWCA. Vegetation removal and surface
hardening stressor indicators are high for 27% of wetland area, while the ditching stressor is high for
23% of wetland area. NWCA 2011 further found that wetlands with high stressor levels from vegetation
removal and surface hardening are about twice as likely to have poor biological condition as those with
low or moderate levels. Additional analysis that looks at how condition might improve if these two
stressors are reduced, called attributable risk, suggests a possible 20% reduction in wetland area with
poor biological condition if the stressor level was reduced from high to moderate or low.
Stressor levels for both of the soil indicators of chemical stress are low for the majority of wetland area
nationally. However, moderate stressor levels for heavy metals are found in 47% of wetland area in the
West and 31% of wetland area in the Eastern Mountains and Upper Midwest. Soil phosphorous stressor
levels are also moderate or high for 22% and 13% of wetland area, respectively, in the Eastern
Mountains and Upper Midwest.
NWCA conducted the first national study of algal toxins in wetlands. Microcystin, a toxin that can harm
people, pets, and wildlife, was detected in 12% of wetland area nationally. However, based on
recreational exposure risk levels established by the World Health Organization, very little wetland area is
found to be at either moderate or high risk levels.
Nationally, 61% of wetland area has low stressor levels from the nonnative plant indicator, but stressor
levels varied by ecoregion. In the West, the majority of wetland area, 71%, has high or very high stressor
levels from the nonnative plant indicator. In the Interior Plains, nearly half of the wetland area (46%) has
high or very high stressor levels.
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Chapter 5 | Summary and Next Steps
Advancing Wetland Science
The contributions of the NWCA go beyond the development of the first national assessment of wetland
condition. EPA, states, tribes, and other federal agency efforts to implement the NWCA resulted in a
robust national program and contributed to the development and enhancement of state and tribal
wetland monitoring programs. For example, Minnesota used vegetation data from a larger sample set
within the state to identify regional variations in wetland condition and potential stressors (see state
highlight, "Minnesota's Intensification Project: NWCA Intensification Survey Helps Reveal Important
Regional Variation in Minnesota").).
The NWCA 2011 survey led to the first national vegetation multimetric index developed for wetlands.
This index provided an assessment of the biological condition of wetlands nationally, and the methods
and assessment tools can also be used at a regional level. In addition, several indicators of stress based
on readily collected field data were developed and used to evaluate the relationship between common
stressors and biological condition. Research into a number of other potential indicators of wetland
condition was conducted, and while not part of this report, will help inform future scientific studies.
NWCA scientists, for example, attempted to develop indicators of wetland condition based on the
presence, abundance, and diversity of algal species, recognizing their role in wetland ecology. The
difficulty in collecting uniform samples and identifying species presence limited the development of such
an indicator. However, the data collected provides valuable information to scientists to further research
relationships between algal communities and wetland ecosystem health.
Water chemistry has been widely used in monitoring and assessment programs in aquatic habitats.
While the NWCA collected water chemistry data from 631 sites, its use was somewhat limited in the
NWCA 2011 because of the variability in surface water presence, both within a wetland and among
wetland types. Future efforts will focus on protocol improvements that would allow for better and more
complete sampling of wetland surface and/or subsurface water. Additionally, analysis of data collected
in 2011 may reveal relationships between water quality and other measures of wetland condition and
ecosystem function that can be further developed in future studies.
Rapid assessment methods (RAMs) are widely used at state and regional levels to evaluate wetlands and
play a key role in the implementation of many state wetland monitoring and assessment programs. As
part of the NWCA, EPA developed and tested a national rapid assessment method named USA-RAM.
This was an integral component of the methods used in the 2011 survey. Initial analysis of the data
indicates that USA-RAM provided measures of wetland stress and condition that correlated with several
individual metrics from the more intensive assessment methods used in the NWCA. Further research
into the data is needed to fully understand how the rapid assessment methods work across regions and
wetland types and to verify and refine USA-RAM. Many states are conducting their own field
assessments of the USA-RAM protocols, and adapting these protocols to meet state-specific wetland
assessment and management needs.
Microbes play an essential role in the breakdown of organic carbon compounds in soils. Their activity is
of particular interest in wetland soils, which have the capacity to store (or sequester) large amounts of
carbon. Carbon storage or release occurs through microbial respiration and is affected by a number of
factors including hydrology, climatic conditions, and the microbial community. Amid growing concerns
regarding greenhouse gases and climate change, scientists are interested in better understanding the
factors that affect carbon cycling in wetlands and their role in the global carbon cycle. As part of the
NWCA 2011, soil samples from 936 wetland sites across the U.S. were analyzed for microbial enzyme
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Chapter 5 \ Summary and Next Steps
activity and respiration. By analyzing the specific types of enzymes present and their relative proportions
in the soil, researchers hope to identify nutrient imbalances in the wetland that may limit microbial
growth. These data will also be used to assess the impact of other factors, such as water and soil
chemistry, land use and related anthropogenic stressors, and atmospheric deposition of nutrients, on
microbial growth. Scientists also hope to use this information to estimate rates of carbon decomposition
and how changes in environmental factors might change microbial communities and decomposition
rates.
As part of NWCA 2011, analysts measured carbon concentrations in the soil, which provides important
information on the amount of carbon that is stored in wetland soils. This is helpful as scientists work to
understand carbon cycling in various wetland types and regions. For instance, scientists will be using soil
data collected for NWCA 2011 to inform the development of baseline estimates of carbon storage in
coastal wetlands as they work to include coastal wetlands into the U.S. Greenhouse Gas Emissions and
Sinks Inventory under the Intergovernmental Panel on Climate Change. This report is prepared annually
by the EPA and cooperating agencies to track greenhouse gas emissions and sinks associated with
anthropogenic activities and land uses. Coastal wetlands (i.e., tidal marshes, mangroves, and sea
grasses) have an important role in greenhouse gas cycling, however they have not yet been included in
the inventory.
NWCA is an initial step in our endeavors to assess wetland condition. As the first survey of its kind, the
2011 study identified biological, chemical, and physical indicators of condition and stress for wetlands
and developed appropriate metrics to assess ecological condition at national and regional scales. The
indicators measured provide new information regarding the health of wetlands nationally, and on
relationships between indicators of ecosystem stress or disturbance and wetland condition. Subsequent
studies and research by EPA, states, and other partners will continue to build upon the knowledge
resulting from the NWCA and allow us to further explore and evaluate the condition of wetlands at
multiple scales. We will be better able to answer important policy and management questions about the
overall health of this critical resource, and design effective strategies to fulfill the objectives of the CWA.
Next Steps: Preparing for the 2016 Assessment
Plans are underway for the NWCA 2016. NWCA scientists are using the findings of the 2011 survey to
guide preparations for the next round of the national assessment. NWCA methods will be further
refined and developed with the goal of increasingly effective and efficient assessment of national
wetland condition.
As an example, a number of different physical, chemical, and biological measures indicative of soil
quality were collected as part of the 2011 survey and were used to indicate potential stressors. Soils are
an important component of wetland ecosystems and the NWCA is interested in further exploring how
these indicators could be used to make assessments about soil health in wetlands. Using both the data
collected and the insights of research scientists and 2011 field crews, the NWCA is working to develop
new methods and further refine existing protocols that will assess the condition of wetland soils and link
soil properties to other measures of wetland health.
The NWCA would not have been possible without the assistance and collaboration of hundreds of
dedicated scientists working for state, federal, and tribal agencies and universities across the country.
These scientists helped plan and design the survey, select indicators, develop and pilot assessment
protocols, train field crews, conduct sampling, track samples, review data for quality control, analyze
data, and review and write up the findings. Future wetland surveys will continue to rely on this close
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Chapter 5 | Summary and Next Steps
collaboration between EPA and its partners, as we further develop our abilities to study and assess
wetlands at multiple scales. We will also continue to build upon the considerable baseline of information
on wetland condition and work to ensure its use in evaluating our progress in protecting and restoring
the quality of our nation's wetlands.
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The U.S. Fish and Wildlife Service's Wetlands Status and Trends Program
Mitch Bergeson, U.S. Fish and Wildlife Service
The U. S. Fish and Wildlife Service (FWS) is the principal Federal agency that provides information to the
public on the extent and status (quantity and type) of the Nation's wetlands. The Wetlands Status and
Trends (S&T) component has had a history of success in providing scientific information to resource
managers and decision makers about wetlands resource trends. The scientific integrity of the Wetlands
S&T study is unchallenged as it represents the most comprehensive and contemporary effort to track
wetlands acreage on a national scale. The information in the National Wetlands S&T Report and the
NWCA Report will complement each other providing the most comprehensive nation-wide picture of
wetland resources.
In 1986, the Emergency Wetlands Resources Act (Public Law 99-645) was enacted to promote the
conservation of our Nation's wetlands. Congress recognized that wetlands are nationally significant
resources and that these resources have been affected by human activities. Under the provisions of this
Act, Section 401 requires the FWS to conduct wetland S&T studies of the Nation's wetlands at periodic
intervals. Reports on the S&T of wetland area were produced by the FWS in 1983/84,1990,1991, 2000,
2006, 2008, 2011 and 2013.
The goal of Wetlands Status and Trends is to provide the Nation with current scientifically valid
information on the status and extent of wetland, riparian and related aquatic resources and
monitor trends of these resources over time.
The S&T studies have provided the nation with information on wetland quantity. The FWS worked closely
with the EPA in preparation for the NWCA study which was designed to address the quality of wetlands
across the nation. This partnership arose because the FWS's Wetlands S&T data set offered one of the
best starting points for a probabilistic national wetlands sampling design. This sample design included a
population of stratified random sample plots across the nation that contained wetlands defined with
Cowardin et al. (1979) wetland classes. These two studies will prove to be invaluable tools by providing
resource managers, agencies and the public with information on both quantity and quality of wetlands of
the Nation.
Wetland Definition and Classification: The FWS uses the Cowardin et al. (1979) definition of wetland. This
definition is the standard for the agency and is the national standard for wetland mapping, monitoring, and
data reporting as determined by the Federal Geographic Data Committee and is separate from the
definition of a wetland found in Section 404 of the CWA regulatory program. The Cowardin et al. definition
of wetlands is described below:
Wetlands are lands transitional between terrestrial and aquatic systems where the water table is
usually at or near the surface or the land is covered by shallow water.
For purposes of this classification wetlands must have one or more of the following three attributes:
(1) at least periodically, the land supports predominantly hydrophytes, (2) the substrate is
predominantly undrained hydric soil, and (3) the substrate is non-soil and is saturated with water or
covered by shallow water at some time during the growing season of each year.
National Wetland Condition Assessment 2011
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As noted in this definition, plant community composition, soil morphology, and site wetness (hydrology)
are the principal indicators of whether a site is a wetland for ecological purposes. Site wetness (i.e., the
presence of water) while central to the concept of wetland, is often the most difficult indicator to assess
accurately because it is more dynamic (temporally variable) than plant community composition or soil
properties. Plants and soil tend to reflect the prevailing degree of wetness at a site over time. For this
reason, they frequently are excellent indicators of relative wetness, and this is why they are listed first as
indicators of wetlands.
Ephemeral waters, which are not recognized as a wetland type, and certain types of "farmed wetlands"
as defined by the Food Security Act and that do not coincide with the Cowardin et al. definition were not
included in this study. The definition and classification of wetland types are consistent between every
S&T study conducted by the FWS and the focus of reporting is on the Nation's wetlands regardless of
ownership. Federal, state, and local regulatory agencies with jurisdiction over wetlands may define and
describe wetlands in a different manner than that used in the Wetland S&T studies.
Wetland Classification Applications: The FWS has made adaptations to the Cowardin classification
system to accommodate the use of remotely sensed imagery as the primary data source. For example,
water chemistry, water depth, substrate size and type and even some differences in vegetative species
cannot always be reliably ascertained from imagery. Image analysts must rely primarily on physical or
spectral characteristics evident on high altitude imagery, in conjunction with collateral data, to make
decisions regarding wetland classification and deepwater determinations3.
The delineation of wetlands and deepwater habitat features through image analysis forms the
foundation for deriving all subsequent products and data results. The wetlands are interpreted from the
image by photo interpreters using key concepts of tone, size, shape, texture, pattern, shadow, location
and association. The FWS makes no attempt to adapt or apply the products of these techniques to
regulatory or legal authorities regarding wetland boundary determinations, jurisdiction or land
ownership, but rather uses the information to assist in making trends estimates characterizing wetland
habitats.
Study Design: The S&T studies were designed to be a quantitative measure of the areal extent of all
wetlands in the conterminous U.S. The approach used is a stratified random sampling of plots. These are
examined, with the use of remotely sensed data in combination with field work, to determine wetland
change.
To monitor changes in wetland area, the 48 conterminous U.S. are stratified or divided by state
boundaries and 37 physiographical subdivisions described by Hammond (1970) and shown in Figure 1.
Zone 36 was added by the FWS to include coastal wetlands and nearshore features. In 2008, Zone 37 was
added to intensify the coastal wetlands along the Pacific coast of conterminous U.S.
To permit even spatial coverage of the sample and to allow results to be computed easily by sets of
states, the 37 physiographic regions formed by the Hammond subdivisions and the coastal zone stratum
are intersected with state boundaries to form 220 subdivisions or strata. An example of this stratification
approach and the way it relates to sampling frequency is shown for Georgia (Figure 2).
Within the physiographic strata described above, weighted, stratified sample plots are randomly
allocated in proportion to the amount of wetland acreage expected to occur within each stratum. Each
sample area is a plot 2 miles (3.218 km) on a side or 4 square miles of area equaling 2,560 acres (1,036
ha). The study includes all wetlands regardless of land ownership.
3Analysis of imagery is often supplemented with limited field work and ground observations.
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National Wetland Condition Assessment 2011
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29 F-ad-Ceniral Dim and LaKo-Mo Hats
30 Eastern Manor Upland* and Basins
Hiyhlo'Kls
32 AdfrnndMft.Nmv Fnglantl Highland*
33 Lower New tngiand
M Gulf-Atlantic Rolling Plain
Gull-Atlantic Coastal F-|at»
CoaelalZone
37
[2| Puget-Willameito Lowland
H Cascade Kiamatti Sierra Nevada Ranges
, * | Central Valley of California
I 5 | Columbia Basin
Syiuo Mountain*
HA'Tifiy-Owyhtse Broken tends
9 | Ba*ln and Range Area
HI Northern Rocky Mountain*
10 Snake River Lowland
H MiOrilo Rocky Mountains
• Wyoming-Big Horn Bairn.
1_3 Colorado Rivet Plaleau*
14 Upp«rr Cila Mountains
[.15: Nuith-Cenlial I ake-5vwiriHi-MtnHin* Plains
JBI Upp*i Missouri Basin Broken Land*
J17J Southern Rocky Mountains
H Rocky Mountain Piedmont
IB High Plains
20 Stockton-B«teor«» Escarpment
Dttou-MmnMou Drm and Lake-bed Flan
22 Nebraska S»nO Hill)
West Central Rolling Milts
Mid-conlineni Plain* and r--v.-arpm*nr*
Southwest Wisconsin Hina
Middl* Weslem Upland Plain
Ozark-Ouocrtita HtgDlnnds
Lower Mis»n*pp. Alluvial F'lam
Figure 1. Physiographic regions of the conterminous U.S. as used for stratification in the Wetlands S&T study
(adapted from Hammond 1970).
The advantages to this design are that it was developed by an interagency group of spatial sampling
experts specifically to monitor wetland changes. It can be used to monitor conversions between
ecologically different wetland types, as well as, measure wetland gains and losses.
All habitats, including wetlands, uplands and deepwater, were mapped in each plot using imagery at two
different dates. The dates of imagery were selected based on availability of imagery closest to the start
and end dates of the sample period for each study. All wetland change was also recorded whether it was
considered the result of either natural change, such as the natural succession of emergent wetlands to
shrub wetlands, or human induced change. The analysis of this data provides accurate estimates of
wetland acreage or status at the start and end of the sample period and also provides estimates of
observed changes over time by wetland type.
Data from S&T studies provide important long-term trend information about specific changes and the
overall status of wetland quantity in the U.S. The FWS has documented this information by producing six
national reports. With the release of the EPA's NWCA report the nation will have documented
information on the quality and condition of these same wetlands. These reports, used in conjunction, will
provide Federal and State agencies, the scientific community and conservation groups information on
both quantity and quality of the Nation's wetlands to assist in planning, decision making and wetland
policy formulation and assessment.
To learn more, contact Mitch Bergeson (mitch_bergeson@fws.gov, 608-238-9333 ext 112), U.S. Fish and
Wildlife Service
National Wetland Condition Assessment 2011
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References:
Cowardin, L.M, V. Carter, F.C. Golet and E.T. LaRoe. 1979. Classification of wetlands and deepwater
habitats of the United States. Department of the Interior. U.S. Fish and Wildlife Service, Washington,
D.C. 131 p.
Dahl, I.E. 1990. Wetlands losses in
the United States 1780s to
1980s. Department of the
Interior, U.S. Fish and Wildlife
Service, Washington, D.C. 21 p.
Dahl, I.E. and C.E. Johnson. 1991.
Status and trends of wetlands in
the conterminous United States,
mid-1970s to mid-1980s. U.S.
Department of the Interior. U.S.
Fish and Wildlife Service,
Washington, D.C. 28 p.
Dahl, I.E. 2000. Status and trends of
wetlands in conterminous
United States 1986 to 1997. U.S.
Department of the Interior, Fish
and Wildlife Service,
Washington, D.C. 82 p.
Dahl, I.E. 2006. Status and trends of
wetlands in the conterminous
United States 1998 to 2004. U.S.
Department of the Interior, Fish
and Wildlife Service, Washington, D.C. 112 p.
Figure 2. Physiographic strata in Georgia.
Dahl, I.E. 2011. Status and trends of wetlands in the conterminous United States 2004 to 2011. U.S.
Department of the Interior, Fish and Wildlife Service, Washington, D.C. 108 p.
Dahl I.E. and S.M. Stedman. 2013. Status and trends of wetlands in the coastal watersheds of the
Conterminous United States 2004 to 2009. U.S. Department of the Interior, Fish and Wildlife Service
and National Oceanic and Atmospheric Administration, National Marine Fisheries Service. 46 p.
Frayer, W.E., T.J. Monahan, D.C. Bowden, and F.A. Graybill. 1983. Status and trends of wetlands and
deepwater habitats in the conterminous United States, 1950'sto 1970's. Colorado State University,
Fort Collins, CO. 31 p.
Hammond, E.H. 1970. Physical subdivisions of the United States of America. In: U.S. Geological
Survey. National Atlas of the United States of America. Department of the Interior, Washington,
D.C. 61 p.
Stedman, S.M. and I.E. Dahl. 2008. Status and trends of wetlands in the coastal watersheds of the
Eastern United States 1998 to 2004. National Oceanic and Atmospheric Administration, National
Marine Fisheries Service and U.S. Department of the Interior, Fish and Wildlife Service. 32 p.
Tiner, R.W. Jr. 1984. Wetlands of the United States: Current status and recent trends. Department of
the Interior. U.S. Fish and Wildlife Service. Washington, D.C. 59 p.
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National Wetland Condition Assessment 2011
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Glossary of Terms
Anthropogenic: Made by people or resulting from human activities. Usually used in the context of
environmental impacts that are a result of human activities.
Assessment Area: A 0.5 hectare area that represents the wetland sampling point where data were
collected for the NWCA.
Attributable Risk: An estimate of the proportion of the population in poor biological condition that could
be reduced if the effects of a particular stressor were eliminated.
Buffer: A defined area immediately adjacent to and surrounding the NWCA Assessment Area, extending
100 meters from the Assessment Area.
Coefficient of Conservatism (C-value): An assigned value describing the tendency of an individual plant
species to occur in disturbed versus pristine conditions. Values are state or regionally specific and scaled
from 0 (widespread, generalist species that thrive under disturbed conditions) to 10 (occur in specific
habitats that are minimally disturbed^.
Condition: The ecological state of a wetland. The NWCA used indicators of condition, such as the
Vegetation Multimetric Index, to describe ecological condition.
Conterminous United States: The United States exclusive of Alaska and Hawaii.
Cowardin Classification System: A national wetland classification system developed by the U.S. Fish and
Wildlife Service (FWS) to describe ecological units with similar natural attributes and provide uniform
concepts and terminology for describing and mapping wetlands and deepwater habitats. The units are
arranged in a hierarchal system to aid resource management decisions.
Cowardin Definition of a Wetland: Lands transitional between terrestrial and aquatic systems where the
water table is usually at or near the surface or the land is covered by shallow water. Wetlands
categorized using the Cowardin System must have one or more of the following three attributes: (1) at
least periodically, the land supports predominantly hydrophytes (i.e., plants that have adapted to living
in saturated conditions); (2) the substrate is predominantly undrained hydric soils; and (3) the substrate
is non-soil and is saturated with water or covered by shallow water at some time during the growing
season of each year. This biologically-based definition is used by the NWCA to define the target
population or group of wetlands of the survey.
Damming Stressors: Indicators of stressors that cause hydrologic alterations in a wetland by impounding
or impeding water flow from or within the wetland. Stress was measured based on observations of
features or activities that could restrict water flow from a site, such as dikes, dams, berms, or railroad
beds.
Ditching Stressors: Indicators of stressors that cause hydrologic alterations in a wetland by draining
water within the wetland. Stress was measured based on observations of features or activities that
potentially drain water from a site, such as ditches, corrugated pipe, excavation, or dredging.
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Glossary of Terms
Ecoregion: Geographical areas that are similar in climate, vegetation, soil type, and geology. Water
resources within a particular ecoregion have similar natural characteristics and similar responses to
stressors.
Ecosystem services: The direct and indirect benefits that people, society, and the economy receive
through the goods and services provided by nature.
Estuarine Ecosystem: As defined by the Cowardin system, deep water tidal habitats and adjacent tidal
wetlands that are usually semi-enclosed by land but have open, partly obstructed, or sporadic access to
the open ocean, and in which ocean water is at least occasionally diluted by freshwater runoff from the
land.
Eutrophication: The enrichment of water bodies by inorganic plant nutrients (e.g., nitrogen,
phosphorus). It may occur naturally but can also be the result of human activity (e.g., fertilizer runoff,
sewage discharge).
Filling/Erosion Stressors: Indicators of stressors that cause hydrologic alterations in a wetland by
removing or depositing soil or sediment. Stress was measured based on observations of features caused
by erosion or deposition, such as soil loss, root exposure, fill/spoil banks, or freshly deposited sediment.
Floristic Quality Assessment Index (FQAI): A two metric calculation that captures information about plant
community composition based upon the total number of unique plant species at a given site, known as
species richness (diversity), and the tolerance of each species to human-mediated disturbance. One of
four metrics included in the Vegetation Multimetric Index.
Geomorphology: The science and study of landforms on the Earth's surface, their evolution over time,
and the interpretation of landforms as a record of geologic history.
Hardening Stressors: Indicators of stressors that cause hydrologic alterations in a wetland by prohibiting
or restricting the movement of water or air into or through the soil. Stress was measured based on
observations of activities that result in surface hardening or compaction, such as parking lots, suburban
residential development, or roads.
Heavy Metal Index: Indicator of stressors that can cause elevated heavy metal concentrations in wetland
soils. The index evaluated concentrations of 12 heavy metals associated with anthropogenic activities
relative to their natural background concentrations in soils.
Hydrogeomorphic (HGM) Classification System: A wetland classification system developed by the U.S.
Army Corps of Engineers that describes and categorizes wetlands based on geomorphic setting
(landscape location), water source(s), and hydrodynamics.
Hydrodynamics: The movement of groundwater and surface water.
Hydrology: The movement, distribution, and physical and chemical characteristics of surface and
subsurface water.
Hydrophytes: Plants that have adapted to living in saturated conditions.
Indicators of Condition: Physical, chemical, and biological factors that describe the ecological condition
of a wetland. The NWCA uses a Vegetation Multimetric Index as a biological indicator of condition.
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Glossary of Terms
Index: A combination of metrics used to generate a single score evaluating the condition or prevalence
of stressors at a site.
Indicators of Stress (Stressors): Physical, chemical, and biological factors that can result from, and
therefore, can be used to identify stressors or anthropogenic activities that have impacted wetland
condition.
Least-disturbed: A disturbance class used to describe sites that represent the best available physical,
chemical, and biological habitat conditions in the current state of the landscape within an NWCA
Reporting Group; represents approximately 15-25% of the sites within a Reporting Group and used as
Reference Condition for the purposes of the NWCA Survey.
Metric: An individual measure of a particular property used to evaluate condition or stressors at an
individual site.
Microcystin: A potentially toxic substance produced by cyanobacteria (a group of microbes also called
blue-green algae).
Monocot: One of two groups of flowering plants characterized by seedlings that have one seed-leaf (e.g.,
grasses, sedges, rushes, lilies, irises, and orchids).
Most-disturbed: A disturbance class used to describe sites that have the worst physical, chemical, and
biological habitat condition in the current state of the landscape within an NWCA Reporting Group;
represents approximately 20-30% of the sites within a Reporting Group.
Native Plant Species: Plant taxa that are indigenous to the state in which they occur.
Nonnative Plant Species: Plant taxa that are indigenous or native to areas outside of the U.S., but not
indigenous to the location of occurrence (introduced), or species that are indigenous or native to some
areas or states in the conterminous U.S., but not indigenous to the location of occurrence (adventive).
Nonnative Plant Stressor Indicator (NPSI): Indicator of stress caused by the presence of nonnative plants
in a wetland. The Index is comprised of three metrics: Relative Cover of Nonnative Species, Richness of
Nonnative Species, and Relative Frequency of Occurrence of Nonnative Species.
Number of Plant Species Tolerant to Disturbance: The number of plant species at the sampling location
with a Coefficient of Conservatism (C-value) indicating a relatively high tolerance for disturbance. One of
four metrics included in the Vegetation Multimetric Index.
Nutrients: Mineral substances that are absorbed by the roots of plants for nourishment. These
substances (e.g., nitrogen, phosphorus) are essential to life, but in excess concentrations can over-
stimulate the growth of algae and other plants in water. Excess nutrients in aquatic resources can come
from agricultural and urban runoff, leaking septic systems, sewage discharges, and similar sources.
NWCA Aggregated Ecoregions: Refers to the four ecoregions (Coastal Plains, Eastern Mountain and
Upper Midwest, Interior Plains, and West) used for NWCA analysis and reporting. The Aggregated
Ecoregions are combinations of nine aggregated ecoregions used in other NARS studies.
NWCA Aggregated Wetland Types: Refers to the four general wetland types (Estuarine Herbaceous;
Estuarine Woody; Inland Herbaceous; and Inland Woody) used for NWCA analysis and reporting. The
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Glossary of Terms
Aggregated Wetland Types are combinations of Cowardin Wetland Types that were part of the NWCA
target population.
Palustrine Ecosystem: As defined by the Cowardin system, includes all nontidal wetlands dominated by
trees, shrubs, persistent emergent, emergent mosses or lichens, and all such wetlands that occur in tidal
areas where salinity due to ocean-derived salts is below 0.05%. It also includes wetlands lacking such
vegetation, but with all of the following four characteristics: (1) area less than 8 hectares (20 acres); (2)
active wave-formed or bedrock shoreline features lacking; (3) water depth in the deepest part of basin
less than 2 meters at low water; and (4) salinity due to ocean-derived salts less than 0.05%.
Population Estimates: An approximation (reported as a percent of the total area or number of acres) of
the entire group of wetlands in the conterminous U.S. that were the target of the study. The NWCA
focus is on wetlands as groups or populations, rather than individual wetlands.
Probability Based Design: A type of random sampling technique in which every element of the
population has a known probability of being selected for sampling.
Reference Condition: The least-disturbed condition available in an ecological region; determined based
on specific criteria and used as a benchmark for comparison with other sample sites in the region.
Relative Cover of Native Monocot Species: The proportion of the sampling location covered by native
monocot species in relation to all plant species present. One of four metrics included in the Vegetation
Multimetric Index.
Relative Cover ofNonnative Species: The proportion of the sampling location covered by nonnative
plants relative to all plant species present. One of three metrics included in the Nonnative Plant Stressor
Index (NPSI).
Relative Extent (Stressor Extent): An estimate (by percent of the resource or relative ranking of
occurrence) of how spatially common a Stressor is based on the population design.
Relative Frequency of Occurrence ofNonnative Species: The occurrence of nonnative plant species at a
site compared to the total number of species. One of three metrics included in the Nonnative Plant
Stressor Index (NPSI).
Relative Importance of Native Plant Species: A measurement of the proportion of the sampling location
covered by native plants relative to all plants present (i.e., relative cover) and the occurrence of native
plant species at a site compared to the total number of species (i.e., relative frequency). One of four
metrics included in the Vegetation Multimetric Index.
Relative Risk: The probability or likelihood of having poor ecological condition when the magnitude of a
stress indicator is high relative to when it is low. This is often presented as a relative risk ratio.
Richness ofNonnative Species: The number of nonnative plant species at the sampling location. One of
three metrics included in the Nonnative Plant Stressor Index (NPSI).
So/7 Phosphorus: An essential plant nutrient. However, high concentrations, due to runoff from
agricultural and urban runoff, sewage discharges, leaking sewer systems, and other sources, can lead to
eutrophication in wetlands and other water bodies. For the NWCA, the concentration of total
phosphorus in the soil was used as an indicator of stressors that cause elevated soil phosphorus
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Glossary of Terms
concentrations. Soil phosphorus concentrations were assessed relative to a threshold set using the
reference site distribution approach.
Stressors: Factors, activities, or land uses that adversely affect, and therefore degrade, aquatic
ecosystems. The NWCA measures stress using chemical, physical, and biological indicators (e.g., high soil
phosphorus concentrations, ditches, relative cover of nonnative plants).
Vegetation Multimetric Index (VMMI): A national indicator of biological condition developed for the
NWCA based on plant species composition (presence and abundance) at sampling locations and plant
species traits. It combines four metrics: a Floristic Quality Assessment Index (FQAI), Relative Importance
of Native Plant Species, Number of Plant Species Tolerant to Disturbance, and Relative Cover of Native
Monocot Species.
Vegetation Removal Stressors: Indicators of stressors that result in losses, removals, or damage of the
vegetation community in a wetland. Stress was measured based on observations of activities that result
in vegetation removal, such as mowing, shrub cutting, herbicide use, intensive grazing, and recently
burned forest.
Vegetation Replacement Stressors: Indicators of stressors that result in changes to the plant species
present in a wetland. Stress was measured based on observations of activities or land uses that would
alter the composition of the plant community, such as tree plantations, nursery, golf courses, lawns,
parks, row crops, pasture, hay fields, or rangeland.
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List of Abbreviations and Acronyms
Ag Silver
Cd Cadmium
cm Centimeter
Co Cobalt
Cr Chromium
Cu Copper
C-value Coefficient of Conservatism
CWA Clean Water Act
EPA U.S. Environmental Protection Agency
°F degree Fahrenheit
FQAI Floristic Quality Assessment Index
FWS U. S. Fish and Wildlife Service
GRTS Generalized Random Tessellation Stratified
GIS Geographic Information System
ha Hectare
HAB Harmful Algal Bloom
HGM Hydrogeomorphic Class
kg Kilogram
L Liter
m Meter
mg Milligram
MMI Multimetric Index
NARS National Aquatic Resource Survey
Ni Nickel
NPSI Nonnative Plant Stressor Indicator
NRCS Natural Resources Conservation Service
NWCA National Wetland Condition Assessment
ORD Office of Research and Development
ORISE Oak Ridge Institute for Science and Education
OW Off ice of Water
P Phosphorus
Pb Lead
RAM Rapid Assessment Method
Sb Antimony
S&T Status and Trends
Sn Tin
spp Multiple species
u.g microgram
USA-RAM U.S.A. Rapid Assessment Method
USDA U.S. Department of Agriculture
V Vanadium
VMMI Vegetation Multimetric Index
W Tungsten
WHO World Health Organization
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Zn
Zinc
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