Status and trends of wetlands in the conterminous United States 1998-2004

              U.S. Fish & Wildlife Service

Status and Trends of

Wetlands in the Conterminous

United States 1998 to 2004

Inside front cover

Status and Trends of

Wetlands in the Conterminous

United States 1998 to 2004

T. E. Dahl

U.S. Fish and Wildlife Service

Fisheries and Habitat Conservation

Washington, D.C.

Opposite page: Louisiana, 2005.

Previous, title page: Freshwater wetland

in the southeast U.S., 2005.

Acknowledgments

Many agencies, organizations,

and individuals contributed their

time, energy, and expertise to the

completion of this report. The author

would like to specifically recognize

the following individuals for their

contributions. From the Fish and

Wildlife Service:

Dr. Benjamin Tuggle, John Cooper,

Herb Bergquist, Jim Dick, Jonathan

Hall , Bill Pearson, Becky Stanley ,

Dr. Mamie Parker, Everett Wilson,

Jill Parker, Robin Nims Elliott.

From the U.S. Geological Survey:

Greg Allord, Dave McCulloch, Mitch

Bergeson, Jane Harner,

Liz Ciganovich, Marta Anderson,

Dick Vraga, Tim Saultz, Mike

Duncan, Ron Keeler and the

staff of the Advanced Systems

Center. From the National Park

Service–Cumberland Island

National Seashore: Ginger Cox,

Ron Crawford and George Lewis.

From the Interagency Field Team:

Sally Benjamin, USDA–Farm

Services Agency; Patricia Delgado,

NOAA, National Marine Fisheries

Service; Dr. Jeff Goebel and Daryl

Lund, USDA–Natural Resources

Conservation Service; David Olsen,

U.S. Army Corps of Engineers; and

Myra Price, U.S. Environmental

Protection Agency.

Peer review of the manuscript was

provided by the following technical

experts: Ms. Peg Bostwick, Michigan

Dept. of Environmental Quality,

Lansing, MI; Dr. Ken Burham,

Statistician, Department of Fishery

and Wildlife Biology, Colorado State

University, Fort Collins, CO; Mr.

Retired.

Current affiliation: NOAA, National Marine

Fisheries Service.

Marvin Hubbell, U.S. Army Corps of

Engineers, Rock Island, IL;

Mr. William Knapp, Deputy Science

Advisor, U.S. Fish and Wildlife

Service, Arlington, VA; Ms. Janet

Morlan, Oregon Dept. of State Lands,

Salem, OR; Dr. N. Scott Urquhart

Research Scientist, Department of

Statistics, Colorado State University,

Fort Collins, CO; Mr. Joel Wagner,

Hydrologist, National Park Service,

Denver, CO; Dr. Dennis Whigham,

Senior Scientist, Smithsonian

Environmental Research Center,

Edgewater, MD; Dr. Joy Zedler,

Professor of Botany and Aldo

Leopold Chair in Restoration

Ecology, University of Wisconsin,

Madison, WI.

This report is the culmination

of technical collaboration and

partnerships. A more complete listing

of some of the cooperators appears at

the end of this report.

Publication design and layout of the

report were done by the Cartography

and Publishing Program, U.S.

Geological Survey, Madison,

Wisconsin.

Photographs are by Thomas Dahl

unless otherwise noted.

This report should be cited as follows:

Dahl, T.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 pp.

Tundra swans (Cygnus columbianus) and other waterfowl congregate in the freshwater marshes along

the upper Mississippi River. Photo courtesy of FWS.

Funding for this study was

provided by the following

agencies:

Environmental Protection Agency

Department of Agriculture

Farm Services Administration

Natural Resources Conservation Service

Department of Commerce

National Marine Fisheries Service

Department of the Army

Army Corps of Engineers

Department of Interior

Fish and Wildlife Service

The Council of Environmental Quality has

coordinated these interagency efforts.

A freshwater emergent wetland in Nebraska, 2005.

Preface

Secretary, Department of the Interior

On Earth Day 2004, President Bush

unveiled a new policy for our nation’s

wetlands. Moving beyond “no net

loss” of wetlands, the President

challenged the nation to increase the

quantity as well as quality of these

important resources, and set a goal

of restoring, improving and

protecting more than 3 million

acres in five years.

The President recognized that a

continuous effort to track progress

toward achieving the various aspects

of the Administration’s new policies

would be important. The Fish and

Wildlife Service was in a unique

position to provide the nation with

sound scientific information

assessing trends in the quantity of

wetland gains and losses. As part of

that same 2004 Earth Day message,

the President directed the Service

to accelerate the completion of this

study and report the results.

This is the Administration’s report

to Congress that provides the nation

with scientific and statistical results

on progress made toward our

national wetlands acreage goals.

I am pleased to report that the

nation is making excellent progress

in meeting these wetland goals. For

the first time net wetland gains,

achieved through the contributions

of restoration and creation activities,

surpassed net wetland losses.

This is the result of a multitude of

governmental, corporate and private

partnerships working together to

secure and conserve our wetland

resources for future generations.

This report does not draw

conclusions regarding trends in

the quality of the nation’s wetlands.

The Status and Trends Study collects

data on wetland acreage gains and

losses, as it has for the past 50 years.

However, it is timely to examine

the quality, function, and condition

of such wetland acreage. Such an

examination will be undertaken

by agencies participating in the

President’s Wetlands Initiative.

U.S. Customary to Metric

inches (in.) x 25.40 = millimeters (mm)

inches (in.) x 2.54 = centimeters (cm)

feet (ft) x 0.30 = meters (m)

miles (mi) x 1.61 = kilometers (km)

nautical miles (nmi) x 1.85 = kilometers (km)

square feet (ft2) x 0.09 = square meters (m2)

square miles (mi2) x 2.59 = square kilometers (km2)

acres (A) x 0.40 = hectares (ha)

Fahrenheit degrees (F) → 0.56 (F - 32) = Celsius degrees (C)

Metric to U.S. Customary

millimeters (mm) x 0.04 = inches (in.)

centimeters (cm) x 0.39 = feet (ft)

meters (m) x 3.28 = feet (ft)

kilometers (km) x 0.62 = miles (mi)

square meters (m2) x 10.76 = square feet (ft2)

square kilometers (km2) x 0.39 = square miles (mi2)

hectares (ha) x 2.47 = acres (A)

Celsius degrees (C) → 1.8 (C) + 32) = Fahrenheit degrees (F)

General Disclaimer

Conversion Table

The use of trade, product, industry or firm names or products in this report is for informative

purposes only and does not constitute an endorsement by the U.S. Government or the Fish and

Wildlife Service.

Contents

Preface......................................................................................................................................................................... 7

Executive Summary.................................................................................................................................................15

Introduction.............................................................................................................................................................. 19

Study Design and Procedures................................................................................................................................21

Study Objectives................................................................................................................................................21

Sampling Design................................................................................................................................................ 24

Types and Dates of Imagery............................................................................................................................26

Technological Advances....................................................................................................................................30

Methods of Data Collection and Image Analysis...........................................................................................30

Wetland Change Detection............................................................................................................................... 31

Field Verification................................................................................................................................................ 3

Quality Control................................................................................................................................................... 34

Statistical Analysis............................................................................................................................................36

Limitations.......................................................................................................................................................... 37

Attribution of Wetland Losses.........................................................................................................................39

Results and Discussion............................................................................................................................................43

Status of the Nation’s Wetlands.......................................................................................................................43

Attribution of Wetland Gain and Loss.............................................................................................................47

Intertidal Estuarine and Marine Wetland Resources...................................................................................48

Marine and Estuarine Beaches, Tidal Bars, Flats and Shoals.....................................................................50

Estuarine Emergent Wetlands........................................................................................................................52

Estuarine Shrub Wetlands...............................................................................................................................5

Wetland Values for Fish and Wildlife–insert–Wetlands and Fish...............................................................57

Freshwater Wetland Resources.......................................................................................................................61

Freshwater Lakes and Reservoirs...................................................................................................................78

Terminology and Tracking Wetland Gains......................................................................................................78

Wetland Restoration and Creation on Conservation Lands................................................................................81

Wetland Restoration–insert–Restoration on the Upper Mississippi River.........................................82

Wetland Restoration–insert–Restoring Iowa’s Prairie Marshes..........................................................85

Monitoring Wetland Quantity and Quality­—

Beyond No-Net-Loss............................................................89

Minnesota’s Comprehensive Wetland Assessment and Monitoring Strategy....................................90

Summary................................................................................................................................................................... 93

References Cited...................................................................................................................................................... 95

Acknowledgement of Cooperators.........................................................................................................................98

Appendix A: Definitoins of habitat categories used in this study.....................................................................101

Appendix B: Hammond (1970) physiographic regions of the United States...................................................105

Appendix C: Wetland change from 1998 to 2004.................................................................................................106

Appendix D: Representative Wetland Restoration Programs and Activities.................................................109

10

List of Figures

Figure 1. A cypress (Taxodium distichum) wetland near the White River, Arkansas, 2005.........................19

Figure 2. A gallery of wetland images....................................................................................................................20

Figure 3. Open water lakes, such as this reservoir were classified as deepwater habitats

if they exceeded 20 acres (8 ha). Piney Run Lake, Maryland, 2005...................................................................2

Figure 4. Coastal wetlands offshore from the mainland include salt marsh

(estuarine emergent) (A), shoals (B), tidal flats (C) and bars.............................................................................24

Figure 5. Physiographic subdivisions of North Carolina and sample plot distribution as used

in this study...............................................................................................................................................................25

Figure 6. High resolution, infrared Ikonos satellite image of bogs (A), lakes (B) and wetlands (C)

of northern Wisconsin, spring 2005........................................................................................................................26

Figure 7. Early spring 2005 Ikonos satellite image of Michigan. Leaf-off condition

made recognition of wetland features easier.........................................................................................................27

Figure 8. Mean date of imagery used by state......................................................................................................28

Figure 9. True color NAIP photographs scale show farmland (A), forest (B), wetlands (C)

and lakes (D) in Indiana, 2003................................................................................................................................29

Figure 10. A small wetland basin estimated to have been about seven square meters...................................30

Figure 1. Change detection involved a comparison of plots at two different times (T1 and T2)..................31

Figure 12. A true color aerial photograph shows a new drainage network

(indicated by red arrow) and provides visual evidence of wetland loss.............................................................32

Figure 13. Lands in transition from one land use category to another pose unique challenges

for image analysts....................................................................................................................................................32

Figure 14. Field verification was completed at sites in the 35 states as shown on the map............................3

Figure 15. Topographic maps in digital raster graphics format were used as auxillary

information and for quality control........................................................................................................................35

Figure 16. Digital wetlands status and trends data were viewed combined with contemporary

georeferenced color infrared imagery of the study areas....................................................................................35

Figure 17. The Pacific coastline..............................................................................................................................37

Figure 18 A and B. Commercial rice fields where water was pumped to flood the rice crop.........................38

Figure 19 A and B. Examples of agricultural land use........................................................................................39

Figure 20. Trees planted in rows with uniform crown height (A) and block clear cuts [blue-green

feature in center (B)] were indicators of managed forest plantations..............................................................40

Figure 21. Urban wetlands (shown as dark blue-black) outside of a shopping mall are

surrounded by high density urban development. New Jersey, 2003, color infrared photograph...................41

Figure 2. Wetland area compared to the total land area of the conterminous United States, 2004............43

Figure 23. Salt marsh along the Ecofina River, Florida .....................................................................................45

Figure 24. Percentage of estimated estuarine and freshwater wetland area and covertypes, 2004..............45

Figure 25. A freshwater wetland in the southeastern United States 2005........................................................46

Figure 26. Average annual net loss and gain estimates for the conterminous

United States, 1954 to 2004.....................................................................................................................................46

11

Figure 27. Wetlands gained or lost from upland categories and deepwater, 1998 to 2004..............................47

Figure 28. Composition of marine and estuarine intertidal wetlands, 2004......................................................48

Figure 29. Estimated percent loss of intertidal estuarine and marine wetlands to

deepwater and development, 1998 to 2004.............................................................................................................49

Figure 30. Non-vegetated tidal flats grade into sparsely vegetated beach ridges. These areas

are important for a variety of birds, sea turtles and other marine life..............................................................50

Figure 31. Intertidal marine beaches provide important habitat for shorebirds.............................................51

Figure 32. The black necked stilt (Himantopus mexicanus) inhabits mud flats, pools,

back water beaches and brackish ponds of saltwater marshes among other wetland habitats......................51

Figure 3. New shoals and sand bars are continually forming in shallow water areas.

This image shows a new feature (brightest white areas) off the coast of Virginia, 2004.................................51

Figure 34. High altitude infrared photograph of salt marsh (darker mottles), coastal Georgia, 2004..........52

Figure 35. Estuarine emergent losses as observed in this study along the Atlantic and Gulf of Mexico.

Inset shows close up of Louisiana where most losses occurred between 1998 and 2004.................................53

Figure 36. Pelican Island, Florida, the nation’s first National Wildlife Refuge is located in

the Indian River Lagoon, a biologically diverse estuary of mangrove islands, salt marsh,

and maritime hammocks.........................................................................................................................................5

Figure 37 A–C. Long-term trends in A) all intertidal wetlands, B) estuarine vegetated wetlands and

C) estuarine non-vegetated wetlands, 1950s to 2004............................................................................................56

Figure 38. Approximate density and distribution of freshwater wetland acreage gains indentified

in the samples of this study.....................................................................................................................................62

Figure 39. A tile drained wetland basin has been restored. Ohio, 2005.............................................................62

Figure 40. Wetland restoration (freshwater emergent) on land previously classified

as upland “other.”.....................................................................................................................................................63

Figure 41. Wetland restoration attributed to agricultural conservation programs in the

upper midwest, 2004................................................................................................................................................64

Figure 42. A restored wetland basin.......................................................................................................................65

Figure 43 A and B. Private efforts to restore wetlands also contributed to the national acreage

base in this study. A) western Minnesota, 2004; B) Stone Lake,

Wisconsin, 2005.........................................................................................................................................................65

Figure 4. Example of wetland loss. Fill being placed into a wetland pond in Ohio, 2005..............................6

Figure 45. An emergent wetland in rural Pennsylvania, 2005, in the process of being filled.

Both examples in Figures 46 and 47 were attributed to Rural Development...................................................6

Figure 46. Areas experiencing wetland loss due to development, 1998 to 2004...............................................67

Figure 47. Development in rapidly growing area of south Florida....................................................................68

Figure 48. Trends in the estimated annual loss rate of freshwater vegetated

wetland area, 1974 to 2004......................................................................................................................................69

Figure 49. A mitigation banking site. As wetlands were converted elsewhere, cells of the

mitigation bank were flooded to create replacement wetland. 2004..................................................................69

Figure 50. Estimated percent loss of forested wetlands to the various upland land use

categories between 1998 and 2004..........................................................................................................................70

Figure 51. Forested wetland. Alabama, 2005. Photo courtesy of South Dakota State University.................70

Figure 52. A freshwater wetland dominated by the woody shrub False Indigo (Amorpha fruticosa).........71

Figure 53. Long-term trends in freshwater forested and shrub wetlands, 1950s to 2004..............................71

Opposite page: Freshwater wetlands of the Yosemite Valley, California.

12

Figure 54. This field has been squared off by agricultural drainage (surface ditch indicated

with red arrow). New Jersey, 2003..........................................................................................................................72

Figure 5. Subtle wetland drainage practices in the prairie pothole region of South Dakota........................73

Figure 56. Long-term trends in freshwater emergent wetlands, 1954 to 2004................................................73

Figure 57. A freshwater pond in central Kansas is starting to support emergent vegetation, 2005.............74

Figure 58. Number and approximate location of new freshwater ponds

created between 1998 and 2004..............................................................................................................................75

Figure 59. A newly created open water pond as part of a golf course. Maryland, 2005..................................75

Figure 62 A–D. Different ponds have been constructed for different purposes throughout

the United States......................................................................................................................................................76

Figure 61. Color infrared aerial photograph of new development in south Florida. Ponds and small

residential lakes (shown as dark blue) are surrounded by new housing...........................................................7

Figure 62. Commercial cranberry operations had created several

open water ponds (dark blue areas)........................................................................................................................7

Figure 63. Long-term trends in freshwater pond acreage, 1954 to 2004...........................................................7

Figure 64A and B. Freshwater lakes provide wildlife and fish habitat as well as opportunities for

recreation and education.........................................................................................................................................78

Figure 65. Created wetland on an area that was upland (dry land)...................................................................79

Figure 6. A wetland restoration (reestablishment). This former wetland basin had been completely

drained and reclassified as upland.........................................................................................................................79

Figure 67. “Improved” wetland or wetland enhancement—hydrology has been restored to

an existing albeit degraded wetland.......................................................................................................................79

Figure 68 . Wetland protection or preservation—included pre-existing wetland acres either

owned or leased long-term by a federal agency....................................................................................................79

Figure 69. A system of federal lands including National Wildlife Refuges and

Wetland Management Districts are restoring and enhancing wetland acres...................................................81

Table 1. Wetland, deepwater, and upland categories used to conduct

wetland status and trends studies..........................................................................................................................23

Table 2. Change in wetland area for selected wetland and deepwater categories, 1998 to 2004 ...................4

Table 3. Changes to estuarine and marine wetlands, 1998 to 2004.....................................................................49

Table 4. Contrasting different estimates of wetland loss in Louisiana..............................................................54

Table 5. Changes in freshwater wetland area between 1998 and 2004..............................................................61

Table 6. Contrasting the Fish and Wildlife Service’s Wetlands Status and Trends with the Council on

Environmental Quality report (2005) on federal efforts to track wetland gains..............................................80

List of Tables

13

14

Executive Summary

The first statistical wetlands status

and trends report (Frayer et al.

1983) estimated the rate of wetland

loss between the mid 1950s and the

mid 1970s at 458,000 acres (185,400

ha) per year. There have been

dramatic changes since that era

when wetlands were largely thought

of as a hindrance to development.

The first indications of those

changes came from the Fish and

Wildlife Service’s updated status

and trends report (Dahl and Johnson

1991) covering the mid 1970s to the

mid 1980s. The estimated rate of

wetland loss had declined to 290,000

acres (117,400 ha) per year.

In 2000, the Fish and Wildlife

Service produced the third

national status and trends report

documenting changes that occurred

between 1986 and 1997. Findings

from that report indicated the

annual loss rate was 58,500 acres

(23,700 ha), an eighty percent

reduction in the average annual rate

of wetland loss.

On Earth Day 2004, President Bush

announced a wetlands initiative that

established a federal policy beyond

“no net loss” of wetlands. The policy

seeks to attain an overall increase

in the quality and quantity of

wetlands. The President set a goal of

restoring, improving and protecting

more than 3 million acres (1.2

million ha) in five years. To continue

tracking wetland acreage trends, the

President further directed the Fish

and Wildlife Service to complete

an updated wetlands status and

trends study in 2005. This latest

report provides the nation with

scientific and statistical results on

the progress that has been made

toward achieving national wetland

quantity goals. This report does not

assess the quality or condition of

the nation’s wetlands. The Status

and Trends Study collects data on

wetland acreage gains and losses,

For over half a century the Fish

and Wildlife Service has been

monitoring wetland trends of the

nation. In 1956, the first report on

wetland status and classification

provided indications that wetland

habitat for migratory waterfowl had

experienced substantial declines

(Shaw and Fredine 1956).

Over the intervening 51 years,

the Fish and Wildlife Service has

implemented a scientifically based

process to periodically measure

wetland status and trends in the

conterminous United States. The

Fish and Wildlife Service’s Wetlands

Status and Trends study was

developed specifically for monitoring

the nation’s wetland area using a

single, consistent definition and

study protocol. The Fish and Wildlife

Service has specialized knowledge

of wetland habitats, classification,

and ecological changes and has used

that capability to conduct a series

of wetland monitoring studies that

document the status and trends of

our nation’s wetlands. This report is

the latest in that series of scientific

studies.

Data collected for the 1998 to 2004

Status and Trends Report has led to

the conclusion that for the first time

net wetland gains, acquired through

the contributions of restoration and

creation activities, surpassed net

wetland losses. There was a net gain

of 191,750 wetland acres (77,630

ha) nationwide which equates to an

average annual net gain of 32,000

acres (12,900 ha).

The efforts to monitor wetland

status and trends that are described

in this report have been enhanced

by the multi-agency involvement in

the study’s design, data collection,

verification, and peer review of the

findings. Interagency funding was

essential to the successful and timely

completion of the study.

A freshwater forested wetland of the

Great Lakes region, 2005.

15

as it has for the past 50 years.

However, it is timely to examine

the quality, function, and condition

of such wetland acreage. Such an

examination will be undertaken

by agencies participating in the

President’s Wetlands Initiative.

This study measured wetland

trends in the conterminous United

States between 1998 and 2004. The

estimates of estuarine emergent

area were made prior to Hurricanes

Katrina and Rita during the summer

of 2005. The Cowardin et al. (1979)

wetland definition was used to

describe wetland types. By design,

intertidal wetlands of the Pacific

coast, reefs and submerged aquatic

vegetation were excluded from this

study.

An interagency group of statisticians

developed the design for the national

status and trends study. The study

design consisted of 4,682 randomly

selected sample plots. Each plot is

four square miles (2,560 acres or

1,040 ha) in area. These plots were

examined, with the use of recent

remotely sensed data in combination

with field work, to determine

wetland change. Field verification

was completed for 1,504 (32 percent)

of the sample plots distributed in 35

states. Representatives from four

states and seven federal agencies

participated in field reconnaissance

trips.

Estimates were made of wetland

area by wetland type and changes

over time.

National Status

and Trends

This study found that there were

an estimated 107.7 million acres

(43.6 million ha) of wetlands in the

conterminous United States in 2004.

Ninety-five percent of the wetlands

were freshwater wetlands and five

percent were estuarine or marine

wetlands.

In the estuarine system, estuarine

emergents dominated, making up

an estimated 73 percent (almost 3.9

million acres or 1.6 million ha) of

all estuarine and marine wetlands.

Estuarine shrub wetlands made

up 13 percent of the area and non-vegetated

saltwater wetlands 14

percent.

In the freshwater system, forested

wetlands made up 51 percent of

the total area, the single largest

freshwater category. Freshwater

emergents made up an estimated

25.5 percent of the total area, shrub

wetlands 17 percent and freshwater

ponds 6.5 percent.

Wetland area increased by an

average 32,000 acres (12,900

ha.) annually. The net gain in

wetland area was attributed to

wetlands created, enhanced or

restored through regulatory

and nonregulatory restoration

programs. These gains in wetland

area occurred on active agricultural

lands, inactive agricultural lands,

and other lands. Freshwater wetland

losses to silviculture, urban and

rural development offset some

gains. Urban and rural development

combined accounted for an

estimated 61 percent of the net

freshwater wetlands lost between

1998 and 2004. This study reports

on changes in wetland acreage and

does not provide an assessment of

wetland functions or quality.

Intertidal

Estuarine and

Marine Wetland

Resources

Three major categories of estuarine

and marine wetlands were included

in this study: estuarine intertidal

emergents (salt and brackish water

marshes), estuarine shrub wetlands

(mangrove swamps) and estuarine

and marine intertidal non-vegetated

wetlands. This latter category

included exposed coastal beaches

subject to tidal flooding, shallow

water sand bars, tidal flats, tidally

exposed shoals, and sand spits.

In 2004, it was estimated there

were slightly more than 5.3

million acres (2.15 million ha) of

marine and estuarine wetlands in

the conterminous United States.

Estuarine emergent wetlands

declined by 0.9 percent. The average

annual rate of estuarine emergent

loss was 5,540 acres (2,240 ha). This

rate of loss was consistent with the

rate of salt marsh loss recorded from

1986 to 1997. Most of the losses of

estuarine emergent wetland were

due to loss to deep salt water and

occurred in coastal Louisiana. One

or more of several interrelated

factors may have contributed to

these losses including: deficiencies

in sediment deposition, canals and

artificially created waterways,

wave erosion, land subsidence, and

salt water intrusion causing marsh

disintegration.

There were an estimated 728,540

acres (294,960 ha) of intertidal

non-vegetated wetlands in 2004.

From 1998 to 2004 marine intertidal

beaches declined by 1,870 acres

(760 ha). Intertidal non-vegetated

wetland changes to urban and other

forms of upland development were

statistically insignificant in this

study.

There were an estimated 682,200

acres (276,190 ha) of estuarine shrub

wetland in 2004. This estimate

represented a small gain of about 800

acres (320 ha). The area of estuarine

shrub wetlands has been steady over

the past two decades.

Freshwater

Wetland

Resources

Large shifts between the freshwater

wetland types and uplands took

place between 1998 and 2004.

Freshwater wetland gains resulted

from restorations and the creation of

numerous freshwater ponds.

Agricultural conservation programs

were responsible for most of

the gross wetland restoration.

These gains came from lands in

“agriculture” category as well

as from conservation lands in

16

the “other” land use category.

Agricultural programs that

promoted pond construction

also contributed to the increased

freshwater pond acreage.

Ponds were included as freshwater

wetlands consistent with the

Cowardin et al. definition.

Freshwater pond acreage increased

by almost 700,000 acres (281,500 ha)

from 1998 to 2004, a 12.6 percent

increase in area. This was the

largest percent increase in area,

of any wetland type in this study.

Without the increased pond acreage,

wetland gains would not have

surpassed wetland losses during the

timeframe of this study. The creation

of artificial freshwater ponds has

played a major role in achieving

wetland quantity objectives.

The replacement of vegetated

wetland areas with ponds represents

a change in wetland classification.

Some freshwater ponds would not be

expected to provide the same range

of wetland values and functions as a

vegetated freshwater wetland.

Freshwater forested wetlands

were affected by two processes,

the conversion of forested wetland

to and from other wetland types

through cutting or the maturation of

trees, and loss of forested wetland

where wetland hydrology was

destroyed. Estimates indicated

that the area of freshwater forested

wetland increased. Between 1998

and 2004, forested wetland area

increased by an estimated 548,200

acres (221,950 ha). Most of these

changes came from small trees,

previously classified as wetland

shrubs, maturing and being re-classified

as forest.

Despite the net gains realized from

restoration and creation projects,

human induced wetland losses

continued to affect the trends of

freshwater vegetated wetlands—

especially freshwater emergent

marshes which declined by an

estimated 142,570 acres (57,720

ha). These wetlands are important

to a number of wildlife species.

Contributed inserts to the report

highlight the importance of wetlands

to fish and wildlife.

American avocets (Recurvirostra americana) at Bear River, Migratory Bird Refuge, Utah, a river delta wetland that attracts

hundreds of species of waterfowl and shorebirds. Photo courtesy of the FWS.

17

18

Introduction The mission of the Fish and Wildlife

Service is to conserve, protect, and

enhance fish, wildlife, plants, and

their habitats for the continuing

benefit of the American people. The

Fish and Wildlife Service supports

programs relating to migratory

birds, endangered species, certain

marine mammals, inland sport

fisheries and a system of 545

national wildlife refuges. The Fish

and Wildlife Service communicates

information essential for public

awareness and understanding

of the importance of fish and

wildlife resources and changes in

environmental conditions that can

affect the welfare of Americans.

To this end, the Fish and Wildlife

Service maintains an active role in

monitoring wetland habitats of the

nation.

The importance of wetlands as fish

and wildlife habitat has always been

the primary focus of the Fish and

Wildlife Service’s wetland activities.

Wetlands are transitional from truly

aquatic habitats to upland and as a

result, wetland abundance, type and

quality are directly reflected in the

health and abundance of many fish

and wildlife species.

The Emergency Wetlands Resources

Act (Public Law 99-645) requires

the Fish and Wildlife Service to

produce national wetlands status

and trend reports for the Congress

at ten year intervals. The Fish and

Wildlife Service has responded to

this mandate with national wetlands

status and trends reports in 1983,

1991 and 2000 (Frayer et al. 1983;

Tiner 1984; Dahl and Johnson 1991;

and Dahl 2000).

These wetland status and trend

reports have been used by federal,

state, local and tribal governments

to develop wetland conservation

strategies, measure the efficacy

of existing policies, and validate

comprehensive performance

toward halting loss and regaining

wetlands. Industry, the scientific

community, conservation groups,

decision makers and the public value

this contemporary information for

planning, decision-making, and on-the-

ground management.

Our nation’s wetlands goals have

historically been based on wetland

acreage and the ability to provide a

quantitative measure of the extent

of wetland area as a means to

measure progress toward achieving

the national goal of “no net loss.”

This concept was first formulated

as a national goal by the National

Wetlands Policy Forum (The

Conservation Foundation 1988)

and was later adopted as federal

policy by President George H.W.

Bush. In an effort to monitor the

status and trends in the quantity

and type of our nation’s wetlands, a

series of Fish and Wildlife Service

reports have documented a steadily

declining wetland loss rate. From

the mid 1950s to the mid 1970s, the

nation lost about 458,000 wetland

acres annually. This rate of loss

was substantially reduced to about

59,000 acres annually by 1997.

On Earth Day 2004, President

George W. Bush announced a

wetlands initiative that established a

federal policy beyond “no net loss” of

wetlands. The policy seeks to attain

an overall increase in the quality

and quantity of wetlands and set

a goal of restoring, improving and

protecting more than 3 million acres

(1.2 million ha) in five years (Council

on Environmental Quality 2005). To

continue tracking wetland trends,

the President further directed

the Fish and Wildlife Service to

complete an updated wetlands status

and trends study in 2005—five years

ahead of the mandated legislative

schedule.

This updated report used the

latest technologies in remote

sensing, geospatial analysis and

computerized mapping. The most

recent aerial and satellite imagery

available was analyzed to document

wetland change on 4,682 two-mile

square (5.2 sq. km) sample plots

located throughout the 48 states. It

covers the period from 1998 to 2004,

and provides the most recent and

comprehensive quantitative measure

of the areal extent of all wetlands

in the conterminous United States

regardless of ownership. The study

provides no qualitative assessments

of wetland functions.

Figure 1. A cypress (Taxodium

distichum) wetland near the White

River, Arkansas, 2005.

19

20

Study Objectives

This study was designed to provide

the nation with current, scientifically

valid information on the status

and extent of wetland resources

regardless of ownership and to

measure change in those resources

over time.

Wetland Definition and Classification

The Fish and Wildlife Service

used 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. It is a two-part

definition as indicated below:

Ephemeral waters, which are not

recognized as a wetland type, and

certain types of “farmed wetlands”

as defined by the Food Security

Act were not included in this

study because they do not meet

the Cowardin et al. definition.

The definition and classification of

wetland types have been consistent

in every status and trends study

conducted by the Fish and Wildlife

Service. Habitat category definitions

are given in synoptic form in Table

1. The reader is encouraged to also

review Appendix A, which provides

complete definitions of wetland

types and land use categories used

in this study.

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.

Study Design and Procedures

Figure 2. A gallery of wetland images. From top to bottom left; emergent marsh in Wisconsin, black-crowned night heron

(Nycticorax nycticorax) (FWS), shrub wetland in Michigan (courtesy of St. Mary’s University), Bosque del Apache National

Wildlife Refuge, New Mexico (FWS). From top to bottom right; forested wetland (FWS), Parker River National Wildlife

Refuge, Massachusetts (FWS), freshwater wetland, northern Indiana, 2005, American toad (Bufo americanus) (Isaac

Chellman, USGS).

21

Deepwater Habitats

Wetlands and deepwater habitats are

defined separately by Cowardin et

al. (1979) because the term wetland

does not include deep, permanent

water bodies. Deepwater habitats

are permanently flooded land lying

below the deepwater boundary of

wetlands (Figure 3). Deepwater

habitats include environments where

surface water is permanent and

often deep, so that water, rather

than air, is the principal medium in

which the dominant organisms live,

whether or not they are attached to

the substrate. For the purposes of

conducting status and trends work,

all lacustrine (lake) and riverine

(river) waters were considered

deepwater habitats.

Upland Habitats

An abbreviated upland classification

system patterned after the U. S.

Geological Survey land classification

scheme described by Anderson

et al. (1976), with five generalized

categories, was used to describe

uplands in this study. These

categories are listed in Table 1.

Figure 3. Open water lakes, such as this

reservoir were classified as deepwater

habitats if they exceeded 20 acres (8 ha).

Piney Run Lake, Maryland, 2005.

22

Table 1. Wetland, deepwater, and upland categories used to conduct wetland status and trends studies.

The definitions for each category appear in Appendix A.

Category Common Description

Salt Water Habitats

Marine Subtidal* Open ocean

Marine Intertidal Near shore

Estuarine Subtidal* Open-water/bay bottoms

Estuarine Intertidal Emergents Salt marsh

Estuarine Intertidal Forested/Shrub Mangroves or other estuarine shrubs

Estuarine Unconsolidated Shore Beaches/bars

Estuarine Aquatic Bed Submerged or floating estuarine vegetation

Riverine* (may be tidal or nontidal) River systems

Freshwater Habitats

Palustrine Forested Forested swamps

Palustrine Shrub Shrub wetlands

Palustrine Emergents Inland marshes/wet meadows

Palustrine Unconsolidated Shore Shore beaches/bars

Palustrine Unconsolidated Bottom Open-water ponds

Palustrine Aquatic Bed Floating aquatic/submerged vegetations

Palustrine Farmed Farmed wetland

Lacustrine* Lakes and reservoirs

Uplands

Agriculture Cropland, pasture, managed rangeland

Urban Cities and incorporated developments

Forested Plantations Planted or intensively managed forests, silviculture

Rural Development Non-urban developed areas and infrastructure

Other Uplands (see further explanation in Appendix A) Rural uplands not in any other category; barren lands

*Deepwater habitat

23

Sampling Design

This study measured wetland extent

and change using a statistically

stratified, simple random sampling

design, the foundations of which

are well documented (Dahl 2000;

USFWS 2004b). The sampling

design used for this study was

developed by an interagency

group of spatial sampling experts

specifically to monitor wetland

change. It can be used to monitor

conversions between ecologically

different wetland types, as well as

measure wetland gains and losses.

Sample plots were 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 states

were stratified or divided by state

boundaries and 35 physiographical

subdivisions described by Hammond

(1970) (Appendix B).

Monitoring Wetlands

Stratification of the nation based on

differences in wetland density makes

this study an effective measure of

wetland resources. Some natural

resource assessments stop at county

boundaries or at a point coinciding

with the census line for inhabitable

land area. Doing so may exclude

offshore wetlands, shallow water

embayments or sounds, shoals, sand

bars, tidal flats and reefs (Figure

4). These are important fish and

wildlife habitats.

The Fish and Wildlife Service

included wetlands in coastal areas

by adding a supplemental sampling

stratum along the Atlantic and

Gulf coastal fringes. This stratum

includes the near shore areas of the

coast with its barrier islands, coastal

marshes, exposed tidal flats and

other offshore features not a part of

the landward physiographic zones.

The coastal zone stratum, included

28.2 million acres (11.4 million ha).

At its widest point in southern

Louisiana, this zone extended about

92.6 miles (149 km) from Lake

24

Figure 4. Coastal wetlands offshore from the mainland, include salt marsh (estuarine emergent) (A), shoals (B), tidal flats (C)

and bars. National Aerial Photography Program, color infrared photograph,coastal Louisiana, 2004.

Pontchartrain to the furthest extent

of estuarine wetland resources.

In this area, saltwater was the

overriding influence on biological

systems. The coastal zone in this

study was not synonymous with any

state or federal jurisdictional coastal

zone definitions. The legal definition

of “coastal zone” has been developed

for use in coastal demarcations,

planning, regulatory and

management activities undertaken

by other federal or state agencies.

To permit even spatial coverage

of the sample plots and to allow

results to be computed easily by

sets of states, the 36 physiographic

regions formed by the Hammond

subdivisions and the coastal zone

stratum were 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 North Carolina (Figure 5).

In the physiographic strata

described above, weighted, stratified

sample plots were randomly

allocated in proportion to the amount

of wetland acreage expected to occur

in each stratum. Each sample area

was a surface plot 2.0 miles (3.2

km) on a side or 4.0 square miles

of area equaling 2,560 acres (1,036

ha). The study included all wetlands

regardless of land ownership.

This study re-analyzed the land area

for 4,371 existing sample plots used

for past wetlands status and trends

studies. Three hundred eleven

supplemental sample plots were

added to Ohio, Indiana, Illinois,

Iowa, Missouri, North Dakota,

South Dakota, California, Oklahoma

and Texas. Augmentation was done

to provide more finite measurement

and equitable spatial coverage of

plots, since loss rates had been

declining historically. This brought

the total number of sample plots

used in this study to 4,682.

25

Figure 5. Physiographic subdivisions of North Carolina and sample plot distribution as used in this study.

Sample Plot Location

Dry

Wet

Gulf-Atlantic Rolling Plain

Appalachian

Highlands

Gulf-Atlantic Coastal Flats

Coastal

Zone

Types and Dates

of Imagery

Image analysts relied primarily

on observable physical or spectral

characteristics evident on high

altitude imagery, in conjunction with

collateral data, to make decisions

regarding wetland classification and

deepwater determinations .

3Analysis of imagery was supplemented

with substantial field work and ground

observations.

Figure 6. High resolution, infrared Ikonos satellite image of bogs (A), lakes (B) and wetlands (C) of northern Wisconsin, spring

2005. Image courtesy of Space Imaging Corp.

Remote sensing techniques to detect

and monitor wetlands in the United

States and Canada have been used

successfully by a number academic

researchers and governmental

agencies (Dechka et al. 2002;

Watmough et al. 2002; Tiner 1996;

National Research Council 1995;

Patience and Klemas 1993; Lillesand

and Kiefer 1987; Aldrich 1979). The

use of remotely sensed data, either

from aircraft or satellite, is a cost

effective way to conduct surveys

over expansive areas (Dahl 1990a).

The Fish and Wildlife Service has

used remote sensing techniques to

determine the biological extent of

wetlands for the past 30 years. To

monitor wetland change, only high

quality imagery was acquired and

used.

26

This study used multiple sources

of recent imagery and direct on-the-

ground observations to record

wetland changes. To recognize and

classify wetland vegetation, color

infrared imagery was preferred

(Figure 6). Experienced wetland

interpreters have found color

infrared to be superior to other

imagery types for recognition and

classification of wetland vegetation

types (USFWS 2004b).

Figure 7. Early spring 2005 Ikonos satellite image of Michigan. Leaf-off condition made recognition of wetland features easier.

These old oxbows or swales (indicated by red arrows) can be masked by heavy tree canopy later in the growing season. Image

courtesy of Space Imaging Corp.

Wherever possible, leaf-off (early

spring or late fall) imagery was

used. Imagery obtained when

vegetation was dormant allowed

for better identification of wetland

boundaries, areas covered by water,

drainage patterns, separation of

coniferous from deciduous forest,

and classification of some understory

vegetation (Tiner 1996). There are

distinct advantages to using leaf-off

imagery to detect the extent of

forested wetlands. Leaf off imagery

enhances the visual evidence of

hydrologic conditions such as

saturation, flooding, or ponding

(Figure 7). This imagery, combined

with collateral data including soil

surveys, topographic maps, and

wetland maps were used to identify

and delineate the areal extent of

wetlands.

27

Figure 8. Mean date of imagery used by state.

In 2004, recent aerial photographic

coverage for large portions of the

country was not available. Multiple

sources of satellite imagery in

combination with recently acquired

digital photography were used

to complete this study. Satellite

imagery made up about 45 percent

of the source material used for

this analysis. Advantages included

higher resolution digital imagery

that was acquired close to the target

reporting date. The mean dates

of the imagery used, by state, are

shown in Figure 8.

Satellite imagery was supplemented

with National Agriculture Imagery

Program (NAIP) imagery acquired

during the agricultural growing

season (Figure 9). NAIP imagery

made up about 30 percent of the

source imagery. (For technical

specifications of NAIP imagery

see www.apfo.usda.gov/NAIP/ .)

The remaining imagery needed to

complete the study was acquired

through various sources of high

resolution aerial photography.

28

2003

2004

2005

California

Oregon

Idaho

Montana

Wyoming

Nevada

Utah

Colorado

North Dakota

South Dakota

Nebraska

Kansas Missouri

Illinois

Wisconsin

Michigan

Indiana

Ohio

Kentucky

Virginia

Florida

South

Carolina

Georgia

North

Carolina

Pennsylvania

New Jersey

New Hampshire

Maryland

Delaware

Connecticut

Massachusetts

Vermont Maine

New York

Rhode Island

West

Virginia

Tennessee

Mississippi

Alabama

Arkansas

Louisiana

Texas

Iowa

Minnesota

Oklahoma

New Mexico

Arizona

Washington

Figure 9. True color NAIP photographs show

farmland (A), forest (B) and wetlands (C) above, and

newly-created ponds in a housing development (D) at

right. Indiana, 2003.

29

Figure 10. A small wetland basin estimated to have been about seven square meters. Some

wetlands this size were detectable using high resolution imagery.

Technological

Advances

Technological advances in the

quality of remotely sensed

imagery, computerized mapping

techniques, and modernization of

data management systems enhanced

the ability to capture more detailed

and timely information about the

nation’s wetlands. The use of these

technologies greatly improved the

administration, access, management

and integration of the spatial

data. Such advances required

modernization of procedural

techniques for image interpretation,

data capture and operational

management. Some of the data

modernization process involved

development of customized software

tools to execute tasks specific to

wetland attribution, provide logic

checking functions and verification

of the digital status and trends data.

These procedural updates were

incorporated into a revised technical

procedures and protocols manual

(USFWS 2004b).

Methods of Data

Collection and

Image Analysis

The delineation of wetlands through

image analysis forms the foundation

for deriving all subsequent products

and results. Consequently, a

great deal of emphasis has been

placed on the quality of the image

interpretation. The Fish and

Wildlife Service makes no attempt

to adapt or apply the products of

these techniques to regulatory or

legal authorities regarding wetland

boundary determinations or to

jurisdiction or land ownership, but

rather the information was used to

assist in making trend estimates

characterizing wetland habitats.

General information on photo

interpretation techniques is

provided by various authors (Avery

1968; Lillesand and Kiefer 1987;

Philipson 1996). Specific protocols

used for image interpretation of

wetlands are documented in the

Status and Trends technical manual

(USFWS 2004b).

Wetlands were identified based on

vegetation, visible hydrology and

geography. Delineations on the

sample plots reflected ecological

change or changes in land use that

influenced the size, distribution or

classification of wetland habitats.

The minimum targeted delineation

unit for wetland was one acre

(0.40 ha). The actual smallest size

of wetland features delineated

was about 0.005 acres (0.002 ha).

However, not all features this size,

or smaller, were detected (Figure

10).

30

Wetland Change

Detection

Remotely sensed imagery was the

primary data for wetland change

detection. It was used in conjunction

with reliable collateral data such

as topographic maps, coastal

navigation charts, soils information,

and historical imagery or studies.

Field verification also played an

important role and was used to

address questions regarding image

interpretation, land use classification

and attribution of wetland gains or

losses.

For each sample plot, the extent

of change among all wetland types

between the two dates of imagery

was used to estimate the total area

of each wetland type (Figure 11)

and the changes in wetland area and

type between the two dates. The

changes were recorded in categories

that can be considered the result

of either natural change, such as

the natural succession of emergent

wetlands to shrub wetlands, or

human induced change. Areas of

sample plots that were identified

in the initial era as wetland but are

no longer wetland were placed into

five land use categories (agriculture,

upland forested plantations,

upland areas of rural development,

upland urban landscapes and other

miscellaneous lands) based upon

the land use evident on the most

recent imagery. The outputs from

this analysis were change matrices

that provided estimates of wetland

area by type and observed changes

Figure 11. Change detection involved a comparison of plots at two different times (T1 and T2).

over time. Rigorous quality control

inspections were built into the

interpretation, data collection and

analysis processes.

Difficulties in determining wetland

change can be related to timing

or quality of the imagery (Dahl

2004). Imagery acquired at the

time of abnormal hydrologic

conditions, such as flooding or

drought, can make determination

of wetland change challenging.

In these instances field work was

required to assist image analysts

in making appropriate wetlands

determinations.

Misinterpretation of wetland loss or

gain could result from factors such

as farming of wetlands during dry

cycles, drought conditions, excess

T1 T2

6 years

31

surface water or flooding. False

changes were avoided by observing

visual evidence of a change in

land management practices. This

included the presence of new

drainage ditches (Figure 12),

canals or other man-made water

courses, evidence of dredging, spoil

deposition or fills, impoundments or

excavations, structures, pavement or

hardened surfaces, in addition to the

lack of any hydrology, vegetation or

soil indicators indicative of wetland.

Some land use practices can also

affect wetland change detection.

Disturbed sites often had ambiguous

remotes sensing indicators.

Disturbed areas were indicative

of lands in transition from one

Figure 13. Lands in transition from

one land use category to another pose

unique challenges for image analysts.

Field inspection of this site indicated

the area was under construction as part

of a highway project.

land use to another (Figure 13).

Upon field inspection, these areas

often had altered hydrology,

soils or vegetation making

wetland classification and change

determination more difficult. In

these instances, field inspection of

the wetland site and surrounding

area provided additional

information.

Figure 12. A true color aerial

photograph shows a new drainage

network (indicated by red arrow)

and provides visual evidence of

wetland loss. Lack of wetland

vegetation, surface water or soil

saturation further indicates that

this wetland had been effectively

drained.

32

Field

Verification

Field verification was completed

for 1,504 (32 percent) of the sample

plots distributed in 35 States

(Figure 14). This constituted

the largest field verification

effort undertaken for a status

and trends report. Field work

was done primarily as a quality

control measure to verify that

plot delineations were correct.

Verification involved field visits to a

cross section of wetland types and

geographic settings, and to plots

with different image types, scales

and dates. Field work was not done

in some western states because of

the remote location (limited access)

of sample plots. Of the 1,504 sample

plots reviewed in the field, 720 used

satellite imagery and 784 used high

altitude aerial photography. All

field verification work took place

between March and September,

2005 . Representatives from four

states and seven federal agencies

participated in field reconnaissance

trips. In rare instances, field work

was used to update sample plots

based on observations of on-the-ground

conditions.

4 Results of field verification work indicated

no discernable differences in the size or

classification of wetlands delineated using

either satellite imagery or the high altitude

photography. Errors of wetland omission

were two percent based on occurrence

but less than one percent based on area

(omitted wetlands were generally small <

1.0 acre or 2.47 ha). Errors of inclusion of

upland were less than one percent in both

occurrence and area. There was no difference

regionally, between states or data analysts

in the number of errors found based on

field inspections, although not all plots were

included in the field analysis.

Figure 14. Field verification was completed at sites in 35 states shown on the map.

33

States not field verified

States field verified

California

Oregon

Idaho

Montana

Wyoming

Nevada

Utah

Colorado

North Dakota

South Dakota

Nebraska

Kansas Missouri

Illinois

Wisconsin

Michigan

Indiana

Ohio

Kentucky

Virginia

Florida

South

Carolina

Georgia

North

Carolina

Pennsylvania

New Jersey

New Hampshire

Maryland

Delaware

Connecticut

Massachusetts

Vermont Maine

New York

Rhode Island

West

Virginia

Tennessee

Mississippi

Alabama

Arkansas

Louisiana

Texas

Iowa

Minnesota

Oklahoma

New Mexico

Arizona

Washington

Quality Control

To ensure the reliability of wetland

status and trends data, the Fish

and Wildlife Service adhered to

established quality assurance and

quality control measures for data

collection, analysis, verification and

reporting. Some of the major quality

control steps included:

Plot Location and Positional

Accuracy

Status and trends sample plots were

permanently fixed georeferenced

areas used to monitor land use and

cover type changes. The same plot

population has been re-analyzed

for each status and trends report

cycle. The plot coordinates were

positioned precisely using a system

of redundant backup locators on

prints produced from a geographic

information system, topographic

maps (Figure 15), other maps

used for collateral information and

the aerial imagery. Plot outlines

were computer generated for the

correct spatial coordinates, size and

projection (Figure 16).

Quality Control of Interpreted Images

This study used well established,

time-tested, fully documented data

collection conventions (USFWS

1994a; 1994b; 2004b). It employed

a small cadre of highly skilled and

experienced personnel for image

interpretation and processing.

All interpreted imagery was

reviewed by a technical expert in

ecological change detection. The

reviewing analyst adhered to all

standards, quality requirements and

technical specifications and reviewed

100 percent of the work.

Data Verification

All digital data files were subjected

to rigorous quality control

inspections. Digital data verification

included quality control checks

that addressed the geospatial

correctness, digital integrity and

some cartographic aspects of

the data. These steps took place

following the review and qualitative

acceptance of the ecological data.

Implementation of quality checks

ensured that the data conformed to

the specified criteria, thus achieving

the project objectives.

Quality Assurance of Digital Data

Files

There were tremendous advantages

in using newer technologies to store

and analyze the geographic data.

The geospatial analysis capability

built into this study provided a

complete digital database to better

assist analysis of wetland change

information.

All digital data files were subjected

to rigorous quality control

inspections. Automated checking

modules incorporated in the

geographic information system

(Arc/GIS) were used to correct

digital artifacts including polygon

topology. Additional customized

data inspections were made to

ensure that the changes indicated

at the image interpretation stage

were properly executed. Digital file

quality control reviews also provided

confirmation of plot location,

stratum assignment, and total land

or water area sampled.

A customized digital data

verification software package

designed specifically for status

and trends work was used. It

checked for improbable changes

that may represent errors in the

image interpretation. The software

considered the length of time

between update cycles, identified

certain unrealistic cover-type

changes such open water ponds

changing to forested wetland, and

other types of potential errors in the

digital data.

34

Figure 15. Topographic maps in digital

raster graphics format were used as

auxilliary information and for quality

control.

Figure 16. Digital wetlands status and trends data were viewed combined with contemporary georeferenced color infrared

imagery of the study areas.

35

Statistical

Analysis

The wetland status and trends

study was based on a scientific

probability sample of the surface

area of the 48 conterminous States.

The area sampled was about 1.93

billion acres (0.8 billion ha), and

the sampling did not discriminate

based on land ownership. The study

used a stratified, simple random

sampling design. About 754,000

possible sample plots comprised

the total population. Given this

population, the sampling design was

stratified by use of the 36 physical

subdivisions described in the “Study

Design” section. This stratification

scheme had ecological, statistical,

and practical advantages. The

study design was well suited for

determining wetland acreage trends

because the 36 divisions of the

United States coincide with factors

that effect wetland distribution

and abundance. Once stratified,

the land subdivisions represented

large areas where the samples were

distributed to obtain an even spatial

representation of plots. The final

stratification, based on intersecting

physiographic land types with state

boundaries, guaranteed an improved

spatial random sample of plots.

Geographic information system

software organized the information

about the 4,682 random sample

plots. An important design feature

crucial to understanding the

technical aspects of this study is

that a grid of full-sized square plots

can be overlaid on any stratum to

define the population of sampling

units for that stratum. However, at

the stratum boundaries some plots

were “split” across the boundary

and thus, were not a full 2,560 acres

(1,036 ha). In sampling theory, plot

size is an auxiliary variable that is

known for all sampled plots and

whose total is known over every

stratum. All sampling units (plots) in

a stratum were given equal selection

probabilities regardless of their

size. In the data analysis phase, the

adjustments were made for varying

plot sizes by use of ratio estimation

theory. For any wetland type, the

proportion of its area in the sample

of plots in a stratum was an unbiased

estimator of the unknown proportion

of that type in that stratum.

Inference about total wetland

acreage by wetland type or for all

wetlands in any stratum began with

the ratio (r) of the relevant total

acreage observed in the sample (Ty),

for that stratum divided by the total

area of the sample (Tx). Thus, y

was measured in each sample plot;

r = Ty/Tx, and the estimated total

acreage of the relevant wetland type

in the stratum was A x r. The sum

of these estimated totals over all

strata provided the national estimate

for the wetland type in question.

Uncertainty, which was measured

as sampling variance of an estimate,

was estimated based on the variation

among the sample proportions in a

stratum (the estimation of sample

variation is highly technical and

not presented here). The sampling

variation of the national total was

the sum of the sampling variance

over all strata. These methods are

standard for ratio estimation in

association with a stratified random

sampling design (Sarndal et al. 1992;

Thompson 1992).

By use of this statistical procedure,

the sample plot data were expanded

to specific physiographic regions,

by wetland type, and statistical

estimates were generated for the 48

conterminous States. The reliability

of each estimate generated is

expressed as the percent coefficient

of variation (% C.V.) associated with

that estimate. Percent coefficient of

variation was expressed as (standard

deviation/mean) x (100). The percent

coefficient of variation indicates that

there was a 95 percent probability

that an estimate was within the

indicated percentage range of the

true value.

Procedural Error

Procedural or measurement errors

occur in the data collection phase of

any study and must be considered.

Procedural error is related to the

ability to accurately recognize

and classify wetlands both from

multiple sources of imagery and

on-the-ground evaluations. Types of

procedural errors may have included

missed wetlands, inclusion of

upland as wetland, misclassification

of wetlands or misinterpretation

of data collection protocols. The

amount of introduced procedural

error is usually a function of the

quality of the data collection

conventions; the number, variability,

training and experience of data

collection personnel; and the rigor

of any quality control or quality

assurance measures.

Rigorous quality control reviews

and redundant inspections were

incorporated into the data collection

and data entry processes to help

reduce the level of procedural error.

Estimated procedural error ranged

from 3 to 5 percent of the true values

when all quality assurance measures

had been completed.

36

Limitations

The identification of wetland

habitats through image analysis

forms the basis for wetland status

and trends data results. Because of

the limitations of aerial imagery as

the primary data source to detect

some wetlands, the Fish and Wildlife

Service excludes certain wetland

types from its monitoring efforts.

These limitations included the

inability to detect small areas;

inability to accurately map or

monitor certain types of wetlands

such as sea grasses (Orth et

al. 1990), submerged aquatic

vegetation, or submerged reefs

(Dahl 2005); and inability to

consistently identify certain forested

wetlands (Tiner 1990).

Other habitats intentionally

excluded from this study include:

Estuarine wetlands of the Pacific

coast—Unlike the broad expanses

of emergent wetlands along the

Gulf and Atlantic coasts, the

estuarine wetlands of California,

Oregon and Washington occur in

discontinuous patches (Figure

17). Their patchy distribution

precludes establishment of a coastal

stratum similar to that of the Gulf

and Atlantic coast wetlands and

no statistically valid data could be

obtained through establishment of a

Pacific coastal stratum. Therefore,

consistent with past studies, this

study did not sample Pacific coast

estuarine wetlands such as those

in San Francisco Bay, California;

Coos Bay, Oregon; or Puget Sound,

Washington.

Figure 17. The Pacific coastline, Three Arch Rocks National Wildlife Refuge, Oregon. Photo courtesy of FWS.

37

Figures 18A and B. Commercial rice

fields where water was pumped to flood

the rice crop. These fields were drained

when they were in upland crop rotation.

Central Arkansas, 2005.

Commercial Rice—Throughout

the southeastern United States and

in California, rice (Oryza sativa)

is planted on drained hydric soils

and on upland soils. When rice was

being grown, the land was flooded

and the area functioned as wetland

(Figures 18A and B). In years when

rice was not grown, the same fields

were used to grow other crops (e.g.,

corn, soybeans, cotton). Commercial

rice lands were identified primarily

in California, Arkansas, Louisiana,

Mississippi and Texas. These

cultivated rice fields were not able

to support hydrophytic vegetation.

Consequently, the Fish and Wildlife

Service did not include these lands in

the base wetland acreage estimates.

38

A

B

Agricultural activity was shown by

distinctive geometric field and road

patterns on the landscape and/or

by tracks produced by livestock or

mechanized equipment. Agricultural

land uses included horticultural

crops, row and close grown crops,

hayland, pastureland, native

pastures and range land and farm

infrastructures (Figure 19A and B).

Examples of agricultural activities in

each land use include:

Horticultural crops consisted of

orchard fruits (limes, grapefruit,

oranges, other citrus, apples,

peaches and like species). Also

included were nuts such as almonds,

pecans and walnuts; vineyards

including grapes and hops; bush-fruit

such as blueberries; berries such

as strawberries or raspberries; and

commercial flower and fern growing

operations.

Attribution of

Wetland Losses

The process of identifying or

attributing cause for wetland losses

or gains has been investigated by

both the Fish and Wildlife Service

and Natural Resources Conservation

Service. In 1998 and 1999, the

Natural Resources Conservation

Service and the Fish and Wildlife

Service made a concerted effort

to develop a uniform approach to

attribute wetland losses and gains

to their causes. The categories used

to determine the causes of wetland

losses and gains are described below.

Agriculture

The definition of agriculture

followed Anderson et al. (1976)

and included land used primarily

for production of food and fiber.

Row and Close Grown Crops

included field corn, sugar cane,

sweet corn, sorghum, soybeans,

cotton, peanuts, tobacco, sugar

beets, potatoes, and truck crops

such as melons, beets, cauliflower,

pumpkins, tomatoes, sunflower and

watermelon. Close grown crops also

included wheat, oats, barley, sod,

ryegrass, and similar graminoids.

Hayland and pastureland included

grass, legumes, summer fallow and

grazed native grassland.

Other farmland included

farmsteads and ranch headquarters,

commercial feedlots, greenhouses,

hog facilities, nurseries and poultry

facilities.

Figure 19A and B. Examples of agricultural land use include both

this rangeland in western Nebraska, 2005 (A), and row crops such

as this cornfield in the midwest, 2004 (B).

39

A

B

Forested Plantations

Forested plantations consisted

of planted and managed forest

stands and included planted pines,

Christmas tree farms, clear cuts and

other managed forest stands. These

were identified by the following

remote sensing indicators: 1) trees

planted in rows or blocks; 2) forested

blocks growing with uniform crown

heights; or 3) logging activity and

use patterns (Figure 20).

Figure 20. Trees planted in rows with uniform crown height (A) and block clear cuts [blue-green feature in center (B) were

indicators of managed forest plantations. Color infrared Ikonos satellite image, Virginia 2004. Courtesy of Space Imaging Corp.

Rural Development

Rural developments occurred in

rural and suburban settings outside

distinct cities and towns. They were

characterized by non intensive land

use and sparse building density.

Typically, a rural development was

a crossroads community that had a

corner gas station and a convenience

store and was surrounded by

sparse residential housing.

Scattered suburban communities

located outside of a major urban

centers were also included in this

category as were some industrial

and commercial complexes;

isolated transportation, power,

and communication facilities; strip

mines; quarries; and recreational

areas such as golf courses.

Major highways through rural

development areas were included in

the rural development category.

40

Urban Development

Urban land consisted of areas of

intensive use in which much of the

land was covered by structures

(high building density as shown in

Figure 21). Urbanized areas were

cities and towns that provided

goods and services through a

central business district. Services

such as banking, medical and legal

office buildings, supermarkets and

department stores made up the

business center of a city. Commercial

strip developments along main

transportation routes, shopping

centers, contiguous dense residential

areas, industrial and commercial

complexes, transportation, power

and communication facilities, city

parks, ball fields and golf courses

were included in the urban category.

Other Land Uses

Other Land Use was composed

of uplands not characterized by

the previous categories. Typically

these lands included native prairie,

unmanaged or non patterned upland

forests, conservation lands, scrub

lands, and barren land. Lands in

transition between different uses

were also in this category.

Transitional lands were lands in

transition from one land use to

another. They generally occurred

in large acreage blocks of 40

acres (16 ha) or more. They were

characterized by the lack of any

remote sensor information that

would enable the interpreter to

reliably predict future use. The

transitional phase occurred when

wetlands were drained, ditched,

filled or when the vegetation had

been removed and the area was

temporarily bare.

Interagency field evaluations were

conducted to test these definitions

on the wetland status and trends

plots to attribute wetland losses or

gains. Field evaluation of these plots

resulted in no disagreement among

agency representatives with how the

Fish and Wildlife Service attributed

wetland losses or gains as to cause.

Figure 21. Urban wetlands (shown as dark blue-black) outside of a shopping mall are surrounded by high density urban

development. New Jersey, 2003, color infrared photograph.

41

A freshwater wetland, Reelfoot Lake, Tennessee, 2005.

42

Results and Discussion

Status of the Nation’s Wetlands

There were an estimated 107.7

million acres (43.6 million ha) of

wetlands in the conterminous

United States in 2004 . (The

coefficient of variation of the

national estimate was 2.7

percent. ) Wetlands composed

5.5 percent of the surface area

of the conterminous United

States (Figure 22). An estimated

95 percent of all wetlands were

freshwater and five percent were

in estuarine or marine systems.

This overall distribution of

wetlands by area and type had not

changed from the previous era.

5 This estimate reflects a 2.0 percent

adjustment to the national wetland acreage

base. This adjustment is within the 3

percent coefficient of variation associated

with this estimation.

6 95 percent confidence interval

Figure 22. Wetland area compared to the total land area of the

conterminous United States, 2004.

Data for the 1998 to 2004 study

period are presented in a change

matrix and shown in Appendix C.

For ease of use, those data have

been summarized and presented in

Table 2.

Within the estuarine system,

estuarine emergent (salt marsh—

Figure 23) dominated, making up

an estimated 73 percent (almost 3.9

million acres or 1.6 million ha) of

all estuarine and marine wetlands.

Estuarine shrub wetlands made

up 13 percent of the area and non-vegetated

saltwater wetlands 14

percent (Figure 24).

Among freshwater wetlands (Figure

25), freshwater forested wetlands

made up the single largest category

(51 percent). Freshwater emergent

wetland made up an estimated 25.5

percent of the total area, shrub

wetlands 17 percent and freshwater

ponds 6.5 percent.

43

Upland

93.5%

Total Land Area

Deepwater*

1%

Wetland

5.5%

*Excludes area of the

Great Lakes

Table 2. Change in wetland area for selected wetland and deepwater categories, 1998 to 2004. The coefficient of

variation (CV) for each entry (expressed as a percentage) is given in parentheses.

Area, In Thousands of Acres

Wetland/Deepwater Category Estimated Area,

1998

Estimated Area,

2004

Change,

1998–2004

Change

(In Percent)

Marine 130.4

(20.2)

128.6

(20.5)

–-1/9

(68.7) –1.4

Estuarine Intertidal Non-Vegetated1 594.1

(10.7)

600.0

(10.3)

5.9

* 1.0

Estuarine Intertidal Vegetated2 4,604.2

(4.0)

4,571.7

(4.0)

–32.4

(32.7) –0.7

All Intertidal Wetlands 5,328.7

(3.8)

5,300.3

(3.8)

–28.4

(48.6) –0.5

Freshwater Non-Vegetated3 5,918.7

(3.7)

6,633.9

(3.5)

715.3

(12.8) 12.1

Freshwater Ponds4 5,534,3

(3.7)

6,229.6

(3.5)

695.4

(13.1) 12.6

Freshwater Vegetated5 96,414.9

(3.0)

95,819.8

(3.0)

–495.1

(35.0) –0.5

Freshwater Emergent 26,289.6

(8.0)

26,147.0

(8.0)

–142.6

* –0.5

Freshwater Forested 51,483.1

(2.8)

52,031.4

(2.8)

548.2

(56.1) 1.1

Freshwater Shrub 18,542.2

(4.1)

17,641.4

(4.3)

–900.8

(34.2) –4.9

All Freshwater Wetlands 102,233.6

(2.9)

102,453.8

(2.8)

220.2

(77.3) 0.2

All Wetlands 107,562.3

(2.7)

107,754.0

(2.7)

191.8

(89.1) 0.2

Deepwater Habitats

Lacustrine5 16,610.5

(10.4)

16,773.4

(10.2)

162.9

(76.2) 1.0

Riverine 6,765.5

(9.1)

6,813.3

(9.1)

47.7

(68.8) 0.7

Estuarine Subtitdal 17.680.5

(2.2)

17.717.8

(2.2)

37.3

(40.8) 0.2

All Deepwater Habitats 41,046.6

(4.6)

41,304.5

(4.5)

247.9

(51.7) 0.6

All Wetlands and Deepwater Habitats1,2 148,618.8

(2.4)

149,058.5

(2.4)

439.7

(31.3) 0.3

*Statistically unreliable.

1 Includes the categories: Estuarine Intertidal Aquatic Bed and Estuarine Intertidal Unconsolidated Shore.

2 Includes the categories: Estuarine Intertidal Emergent and Estuarine Intertidal Shrub.

3 Includes the categories: Palustrine Aquatic Bed, Palustrine Unconsolidated Bottom and Palustrine Unconsolidated Shore.

4 Includes the categories: Palustrine Aquatic Bed, Palustrine Unconsolidated Bottom.

5 Includes the categories: Palustrine Emergent, Palustrine Forested and Palustrine Shrub.

6 Does non include the open-water area of the Great Lakes.

Percent coefficient of variation was expressed as (standard deviation/mean) x 100.

44

Figure 24. Percentage of

estimated estuarine and

freshwater wetland area and

covertypes, 2004.

Figure 23. Salt marsh along the Ecofina

River, Florida.

Figure 25. A freshwater wetland in the

southeastern United States, 2005.

Estuarine Wetlands

Total Wetlands

Freshwater

95%

Estuarine

5%

Emergents

73%*

Flats/Beaches

14%

Shrubs

13%

Freshwater Wetlands

Forested

51%

Emergents

25.5%*

Shrubs

17%

Ponds

6.5%

*Denotes change from

previous era

45

National Trends, 1998 to 2004

Between 1998 and 2004 there was

an estimated net gain (Table 3) in

wetlands of 191,750 acres (77,630

ha). This equated to an average

annual net gain of about 32,000

acres (12,900 ha) as seen in Figure

26. These estimates have led to the

conclusion that wetland area gains

achieved through restoration and

creation have outdistanced losses.

These data indicate a net gain in

acreage but this report does not

draw conclusions regarding trends

in quality of the nation’s wetlands

7 There are statistical uncertainties associated

with this estimate. The coefficient of variation

expressed as a percentage is 89.1 percent for

the net gain estimate.

Intertidal wetlands declined by

an estimated 28,416 ac (11,500 ha)

from 1998 to 2004. This was an

average annual loss of about 4,740

acres (1,920 ha). The majority of

these losses (94 percent) were to

deepwater bay bottoms or open

ocean.

Almost all net gains of wetland

observed between 1998 and 2004

were in freshwater wetland types.

The estimated net gain in freshwater

wetland area between 1998 and 2004

was 220,200 acres (89,140 ha) as

Figure 26. Average annual net loss and gain estimates for the conterminous United States, 1954 to 2004. Sources: Frayer et al.

1983; Dahl and Johnson 1991; Dahl 2000; and this study.

seen in Table 2. Forested wetlands

experienced a net gain. This can

be explained by the maturation of

wetland shrubs to forested wetlands.

There was also a substantial increase

in the number of open water ponds.

Pond area increased by an estimated

12.6 percent over this study period.

46

100,000

0

-100,000

-200,000

-300,000

-400,000

-500,000

Gains

+32,000

Losses

-58,550

-290,000

-458,000

1950s–1970s 1970s–1980s 1980s–1990s

Acres

1998–2004

Attribution of

Wetland Gain

and Loss

Figure 27 depicts the categories

that contributed wetland gains and

those responsible for wetland losses

over the course of this study. A net

gain in wetland area was attributed

to conversion of agricultural lands

or former agricultural lands that

had been idled in combination

with wetland restorations from

conservation lands in the “other”

land use category.

Some freshwater wetland

losses attributed to urban, rural

development and silviculture offset

some of the gains. An estimated

88,960 acres (36,000 ha) or 39

percent of the wetland losses, were

lost to urban developments, 51,440

acres (20,800 ha), 22 percent were

lost to rural development and

18,000 acres (7,300 ha), 8 percent

of wetlands were lost through

drainage or filling for silviculture.

These losses were all the result of

actions that destroyed the wetland

hydrology. An additional 70,100

acres (28,400 ha), or 31 percent

of the wetland area lost between

1998 and 2004 became deepwater

habitats.

There were net gains from the

“other” lands category and from

Agriculture as a result of wetland

restoration and conservation

programs. An estimated 70,700

wetland acres (28,600 ha) came from

agricultural lands and 349,600 acres

(141,500 ha) from “other” uplands.

These gains represented 17 percent

of the net wetland gains from

Agriculture and 83 percent from

“other” uplands. Since the “other”

uplands category includes lands in

transition some of these wetlands

may be subject to loss over time.

Representative wetland restoration

programs are listed in Appendix D.

Using the study definitions for

the causes of wetland losses and

gains, it was determined that urban

development and rural development

accounted for an estimated 140,400

acres (56,840 ha) or 61 percent of

wetland loss over the course of this

study.

Figure 27. Wetlands gained or lost from upland categories and deepwater, 1998 to 2004.

47

Deepwater

-70,100

Urban

-88,960

Rural

Development

-51,440

Land Use Category

Silviculture

-18,000

Agriculture

+70,770

Other

+349,600

0

20

-20

-40

-60

-80

-90

40

60

80

400,000

Acres (in Thousands)

Gains

Losses

Intertidal

Estuarine and

Marine Wetland

Resources

Three major categories of estuarine

and marine wetlands were included

in this study: estuarine intertidal

emergents (salt and brackish water

marshes), estuarine shrub wetlands

(mangrove swamps or mangles and

other salt tolerant woody species)

and estuarine and marine intertidal

non-vegetated wetlands. This latter

category included exposed coastal

beaches subject to tidal flooding,

shallow water sand bars, tidal flats,

tidally exposed shoals and sand

spits.

The vegetated components of the

estuarine and marine systems

are among the most biologically

productive aquatic ecosystems in

the world (Kennish 2004). Wetlands

along the nation’s coastline have

provided valuable resources and

supported large sections of the

nation’s economy (USEPA 2004).

Wetlands have also provided

opportunities for recreation and

supported commercially valuable

fish and crustacean populations.

Estuarine and wetland dependent

Figure 28. Composition of marine and estuarine intertidal wetlands, 2004.

fish and shellfish species accounted

for about 75 percent of the total

annual seafood harvest in the United

States (Weber 1995). In the Gulf of

Mexico, coastal waters attracted

millions of sport fishermen and

beach users as tourism in the Gulf

coast states contributed over $20

billion to the nation’s economy

(USEPA 1999). The importance

of both estuarine and freshwater

wetlands to fish populations, and

sport and commercial fishing

cannot be overemphasized. This

link between wetlands and aquatic

species includes ecological processes

that are important for maintaining

food webs, land and water

interactions, and environmental

quality. Wetland loss and its effect

on fish populations are among the

many issues forcing a re-evaluation

of activities on the landscape (NOAA

2001).

Estuarine and marine wetlands

have been particularly susceptible

to the various stressors resulting

from rapid population growth and

development within the coastal

watersheds nationwide (Kennish

8 The importance of wetlands to fish

populations is discussed in the insert section

“Wetlands and Fish.”

2004). From the 1950s to 1970s,

estuarine wetlands were dredged

and filled extensively for residential

and commercial development and

for navigation (Hefner 1986). To

help conserve the nation’s valuable

coastal resources, numerous

measures have been taken to protect

estuarine and marine resources.

Since the mid 1970s, many of the

nation’s shoreline habitats have

been protected either by regulation

or public ownership. These

mechanisms, in combination with

outreach and educational efforts,

have been responsible for reducing

intertidal wetlands losses in Florida

(Dahl 2005).

This study estimated that in 2004

there were slightly more than 5.3

million acres (2.1 million ha) of

marine and estuarine wetlands in

the conterminous United States.

Eighty six percent of that total area

was vegetated wetland (Figure 28).

Collectively, intertidal wetlands

declined by an estimated 28,416

ac (11,580 ha) between 1998 and

2004. Estuarine vegetated wetlands

declined by an estimated 32,400

acres (13,120 ha) between 1998

and 2004. Estuarine non-vegetated

wetlands experienced a net gain of

an estimated 4,000 ac (1,620 ha);

marine intertidal shorelines declined

by 1,900 ac (770 ha).

48

All Intertidal Wetlands

Estuarine Vegetated Wetlands

Vegetated

86%

Non-vegetated

14%

Emergents

85%

Shrubs

15%

Table 3. Changes to estuarine and marine wetlands, 1998 to 2004. The coefficient of variation (CV) for each entry

(expressed as a percentage) is given in parentheses.

Area, In Thousands of Acres

Wetland Category Estimated Area,

1998

Estimated Area,

2004

Gain or Loss,

1998–2004

Change

(In Percent)

Area (as Percent)

of All Intertidal

Wetland, 2004

Marine Intertidal 130.4

(20.2)

128.6

(20.5)

–1.9

(68.7) –1.4 2.4

Estuarine Unconsolidated Shore 563.2

(10.8)

567.5

(10.4)

4.3

* 10.7

Estuarine Aquatic Bed 30.8

(27.1)

32.4

(26.0)

1.6

(63.6) 0.6

Marine and Estuarine Intertidal

Non-Vegetated

724.5

(9.8)

728.5

(9.5)

4.0

* 0.5 13.7

Estuarine Emergent 3,922.8

(4.2)

3,889.5

(4.2)

–33.2

(31.8) 73.4

Estuarine Shrub 681.4

(12.5)

682.2

(12.5)

0.8

* 12.9

Estuarine Intertidal Vegetated1 4,604.2

(4.0)

4,571.7

(4.0)

–32.4

(32.6) –0.7 86.3

Changes in Coastal Deepwater area, 1998–2004

Estuarine Subtitdal 17,680.5

(2.2)

17,717.8

(2.2)

37.3

(40.8) — —

*Statistically unreliable.

1 Includes the categories: Estuarine Emergent and Estuarine Shrub.

Excludes marine and estuarine wetlands of California, Oregon and Washington.

Percent coefficient of variation was expressed as (standard deviation/mean) x (100).

open saltwater systems (Figure 29).

This was due to natural and man-induced

activities such as dredging,

water control, and commercial and

recreational boat traffic . The losses

of estuarine emergents exceeded the

total net loss of all other intertidal

estuarine and marine wetlands

combined.

9 Losses reported here were prior to the

hurricanes of 2005. The Fish and Wildlife

Service is preparing to conduct follow-up

studies to reassess wetland changes along the

Gulf Coast.

The changes that occurred between

1998 and 2004 in estuarine and

marine wetlands are shown in Table

3. The largest acreage change was

an estimated net loss of 33,230 acres

(13,450 ha) of estuarine emergent

wetland. The greatest percent

change was a decline of 1.4 percent

of marine intertidal wetland.

The overriding factor in the decline

of estuarine and marine wetlands

was loss of emergent salt marsh to

Figure 29. Estimated percent

loss of intertidal estuarine and

marine wetlands to deepwater and

development, 1998 to 2004.

49

Deepwater

93%

Development

7%

Marine and

Estuarine

Beaches, Tidal

Bars, Flats and

Shoals

Sand, mud or rock beaches, bars

and shoals along the interface

with tidal saltwater composed the

non-vegetated intertidal wetlands

(Figure 30). These areas were

subject to dramatic changes

resulting from coastal storms,

hurricanes, tidal surge, sea level

rise, sediment deposition or various

forms of artificial manipulation

during this study period.

Ecologically, these wetlands are

important to a variety of fish and

wildlife species. Open sandy beach

Figure 30 . Non-vegetated tidal flats grade into sparsely vegetated beach ridges. These areas are important

for a variety of birds, sea turtles and other marine life. Florida, 2000.

habitats are particularly important

to nesting, foraging and loafing

waterbirds (Kushlan et al. 2002)

(Figure 31 and 32). The green sea

turtle (Chelonia mydas) and the

loggerhead sea turtle (Caretta

caretta) also use sandy beaches

for nesting sites. Shallow water

coastal flats are important for

sport fish such as the sand sea

trout (Cynoscion arenarius),

bonefish (Albuta vulpes), and snook

(Centropomus undecimalis).

There were an estimated 728,540

acres (294,960 ha) of intertidal non-vegetated

wetlands in 2004. This

study found that from 1998 to 2004

(Table 4) marine intertidal beaches

declined by 1,900 acres (770 ha),

a 1.4 percent decline. This was

very similar to the rate of decline

observed from 1986 to 1997, when

marine beaches declined 1.7 percent.

Estuarine bars, flats and shoals

(Figure 33) increased in area over

the same timeframe. There was an

estimated increase of 4,300 acres

(1,740 ha). This increase was largely

at the expense of estuarine emergent

salt marsh which was sloughed into

deeper water bays and sounds. Land

subsidence, saltwater intrusion and

coastal erosion processes may have

contributed to these changes.

Intertidal non-vegetated wetland

changes to urban and other forms

of upland development were not

statistically significant.

50

Figure 31. Intertidal marine beaches provide important

habitat for shorebirds. These types of wetlands declined by

1.4 percent between 1998 and 2004. Coastal Louisiana, 2005.

Photo by J. Harner, USGS. Figure 32. The black-necked stilt

(Himantopus mexicanus) inhabits mud

flats, pools, back water beaches, brackish

ponds of saltwater marshes and other

wetland habitats. Photo courtesy of FWS.

Figure 33. New shoals and sand bars are continually forming in shallow water areas. This image shows a new feature

(brightest white areas) off from the coast of Virginia, 2004.

51

Estuarine

Emergent

Wetlands

Estuarine emergent wetlands

(synonymous with the term “salt

marsh”) were found close to the

shoreline and were associated with

estuaries, lagoons, embayments,

sounds and coastal barriers

(Figure 34). Salinities ranged from

hypersaline to oligohaline (Cowardin

et al. 1979). The coastal plain of

the southeastern Atlantic and Gulf

States supported expansive areas

of intertidal estuarine wetlands,

particularly emergent salt marsh.

These marshes support diverse

animal life and are extremely

productive and ecologically

important features on the coastal

landscape. The abundance and

distribution of individual species

of both animals and plants are

influenced by physical conditions

including salinity, water depth,

tidal fluctuation and temperature

variations (Chabreck 1988).

There were an estimated 3,889,500

acres (1,574,700 ha) of estuarine

emergent salt marsh wetland in

2004.

Estuarine emergent wetland

declined by 33,230 acres (13,450

ha) between 1998 and 2004. This

represented a loss of 0.9 percent

of this wetland type. The average

annual rate of estuarine emergent

loss was 5,540 acres (2,240 ha). This

rate of loss was consistent with the

rate of salt marsh loss recorded from

1986 to 1997 (Dahl 2000). Urban and

rural development activities, and

the conversion of wetlands to other

upland land uses, accounted for an

estimated loss of 1,732 acres (700 ha)

or about 3.0 percent of all losses of

estuarine emergent wetland. Most

of the losses of estuarine emergent

wetland were due to loss to deep

salt water and occurred in coastal

Louisiana (Figure 35).

Numerous restoration and

rehabilitation projects have been

undertaken in Louisiana as part

of the Coastal Wetlands Planning,

Protection and Restoration Act of

1990, to begin the process of slowing

the rate of wetland loss in that

region (Zinn and Copeland 2002).

Despite these efforts, the rate of

estuarine wetland loss has remained

constant since the mid 1980s.

Projects undertaken in Louisiana

may have restored functional value

of some wetlands. Other restoration

efforts might have been directed

toward freshwater wetlands

elsewhere within “coastal” proximity

but outside of the estuarine and

marine systems.

Figure 34. High altitude infrared photograph of salt marsh (darker mottles) offshore from coastal Georgia, 2004.

52

Estuarine Emergent Wetland Loss

0–25 Acres

26–75 Acres

76–150 Acres

151–300 Acres

Texas

Texas

Louisiana

Louisiana

Mississippi

Mississippi

Alabama

Florida

Georgia

South Carolina

North Carolina

Virginia

Maryland

Delaware

New Jersey

Connecticut

Massachusetts

Vermont

New Hampshire Maine

Rhode

Island

Pennsylvania

New York

Figure 35. Estuarine emergent losses as observed in this study

along the Atlantic and Gulf of Mexico. Inset shows close up of

Louisiana where most losses occurred between 1998 and 2004.

53

Estimates of wetland loss from

this study were contrasted with

other estimates of wetland loss

in Louisiana as seen in Table 4.

Geographic dissimilarities and

terminology differences including

“coastal” versus “estuarine,”

“wetland” versus “land loss,” and

temporal differences accounted for

some of the discrepancies. It is clear

that there has been confusion over

the region included (where), types

of wetland and/or upland included

in the estimates (what) and the

timeframe of when losses occurred

(when). This study measured

changes in marine and estuarine

wetlands from 1998 to 2004 as

described earlier.

One or more of several interrelated

factors may have contributed to

the loss of estuarine emergent

wetland, including: deficiencies in

sediment deposition, canals and

artificially created waterways,

wave erosion, land subsidence, and

salt water intrusion causing marsh

disintegration. In recognizing that

human activities have affected

wetlands in Louisiana, Williams et

al. (1995) cited an extensive system

of dredged canals and flood-control

structures constructed to facilitate

hydrocarbon exploration and

production as well as commercial

and recreational boat traffic that had

enabled salt water to intrude from

the Gulf of Mexico as major factors

in wetland loss.

Coastal storms often have had a

role in destabilizing salt marsh

substrates by washing away

sediment with wind driven

floodwaters (Chabreck 1988).

Estimates of estuarine emergent

area reported here, were made

prior to Hurricane Katrina and Rita

during the summer of 2005. These

storm events may have further

exacerbated vegetated marsh losses

by creating open water pockets or

lakes to replace vegetated wetlands

in St. Bernard and Plaquemines

Parishes, Louisiana (USGS 2005b).

Estuarine emergent wetlands have

been restored elsewhere in the

country. An estimated 2,540 acres

were reclaimed from freshwater

wetlands through projects such as

the Dande Meadows Salt Marsh

Project in Massachusetts. This

project restored natural salt marsh

that had been converted into a

freshwater hayfield during colonial

times (Coastal America 2003). Small

to moderate scale projects have

been undertaken within the National

Estuarine Research Reserve System

as well. There, the focus has been on

restoring salt marsh and seagrass

beds where ecological functions have

declined (Kennish 2004).

Table 4. Contrasting different estimates of wetland loss in Louisiana.

Habitat Description Estimated Loss Rate

Normalized1 Loss

Rate (Hectares per

Year)

Source

Coastal marsh 50 acres/day 7,390 ha Moorman (2005)

Ducks Unlimited Southern Region

Coast and wetlands 25 sq. mi./yr 6,480 ha Louisiana State University (2005)

Wetlands of coastal

Louisiana

50 sq. mi./yr 12,960 ha Louisiana Geological Survey and EPA (1987)

Louisiana’s wetlands 75 sq. km/yr 7,500 ha Williams (1995)

USGS—Marine and Coastal Geology Program

Louisiana’s wetlands 16,000 to 25,000 acres/yr 6,480 to 10,120 ha National Marine Fisheries Service (www.nmfs.noaa.

gov/habitat)(2005)

Coastal land 25 to 35 sq. mi/yr 6,480 to 9,070 ha Tulane University (2004)

Marsh 40 sq. mi./yr 10,360 ha USGS, National Wetland Research Center (2005)

Estuarine and Marine

emergent wetland

5,500 acres/yr 2,240 ha This Study

1Scaled to 365 days and expressed as hectares.

Conversion factors:

Square mile = 640 acres

Hectare = 2.47 acres

Square kilometer = 247 acres

54

Estuarine Shrub

Wetlands

Among the most notable components

of the estuarine shrub wetland

category are mangrove swamps.

The geographic extent of mangroves

has been influenced by cold

temperatures, hurricanes, and

human induced stressors (Spalding

et al. 1997). Florida has always been

the primary location of mangrove

wetlands in the United States.

Mangrove species are uniquely

adapted to saline environments

and ecologically mangroves have

supported a diversity of wildlife

(Odum and McIvor 1990). Mangrove

communities and surrounding

waters of south Florida support

more than 220 species of fish, 24

species of reptiles and amphibians,

18 mammals and 181 bird species

(U.S. Fish and Wildlife Service 1996)

(Figure 36).

Mitsch and Gosselink (1993)

indicated that the northern-most

extent of black mangrove (Avicennia

geminans) occurred at about 30

degrees N. latitude. Although

scattered stands of mangrove shrubs

have been found along the north

coast of the Gulf of Mexico (Odum

and McIvor 1990), these wetlands

have been exposed to freezing

temperatures that greatly reduced

their number and distribution.

Estuarine shrub wetlands may have

included woody species other than

mangroves. Other salt-tolerant

or invasive woody plants in these

northern wetlands included false

willow (Baccharis angustifolia),

saltbush (Baccharis halimifolia),

buttonwood (Conocarpus erectus),

bay cedar (Suriana maritina)

and Brazilian pepper (Schinus

terebinthifolius).

There were an estimated 682,200

acres (276,190 ha) of estuarine shrub

wetland in 2004. This estimate

represented a gain of about 800

acres (320 ha). Most of this gain

came from areas formerly classified

as estuarine emergent wetland.

The acreage estimates of estuarine

shrub wetlands have been steady or

increased slightly over the past two

decades.

The long term trend in all intertidal

wetlands, estuarine vegetated and

estuarine non-vegetated categories

is shown in Figure 37 A-C. Estuarine

vegetated wetlands have continued

to decline over time as losses to the

estuarine emergent category have

overshadowed the small gains to

estuarine shrub wetlands.

Figure 36. Pelican Island, Florida, the nation’s first National Wildlife Refuge is located in the Indian River Lagoon, a

biologically diverse estuary of mangrove islands, salt marsh, and maritime hammocks. Photo courtesy of the FWS.

55

Figure37 A–C. Long-term trends in A) all intertidal wetlands, B) estuarine vegetated wetlands and C) estuarine non-vegetated

wetlands, 1950s to 2004.

56

5,000

5,200

5,400

5,600

5,800

6,000

6,200

Acres (in Thousands)

B. Estuarine Vegetated Wetlands

4,200

4,400

4,600

4,800

5,000

5,200

1950s 1970s 1980s 1998 2004

Acres (in Thousands)

C. Estuarine Non-vegetated Wetlands

0

200

400

600

800

1,000

1950s 1970s 1980s 1998 2004

Acres (in Thousands)

A. All Intertidal Wetlands

6,000

5,500

5,399

5,329

5,300

1950s 1970s 1980s 1998 2004

4,604

4,572

4,623

4,854

5,000

594 594 600

678

741

Wetland Values for Fish and Wildlife

Wetlands and Fish

Formed in 1922, The Izaak Walton League is one

of the nation’s oldest conservation organizations

to address deteriorating conditions of America’s top

fishing streams. The League is named for the 17th-century

English angler-conservationist who wrote the

literary classic “The Compleat Angler.” Since 1992,

the League has been restoring wetlands and streams,

establishing wildlife refuges and parks, and teaching

outdoor ethics to outdoor enthusiasts, sportsmen

and conservationists. League members recognize

the importance of wetlands and the role they play

in supporting fish species and angling opportunities

throughout the United States.

Fish and seafood provide the largest source of protein

for people across the world. The worldwide fish harvest

has surpassed cattle production and poultry farming

as the primary source of animal protein (FAO 1987).

The United States consumes more than 4 billion tons of

fish and shellfish every year—an average of 16 pounds

per person (National Marine Fisheries Service 2004).

Additionally, about 34 million people in the United

States fish for recreation (USFWS 2001).

America’s coastal and freshwater fish populations are

currently facing an unprecedented decline. Since 1900,

123 aquatic freshwater species have become extinct

in North America. Of the 822 native freshwater fish

species in the United States, 39 percent are at risk

of extinction (Fisheries and Water Resources Policy

Committee 2004) and 72 percent of freshwater mussels

are imperiled (USFWS 2004a). Additionally, the world’s

catch of ocean fish has been steadily falling since 1989,

with 13 of the 17 most productive fisheries currently

facing steep declines. Several factors have contributed

to this decline, including over-fishing and pollution.

However, the rate at which America’s fish populations

are plummeting is largely due to the loss and alteration

of their aquatic habitats.

At one time, the conterminous United States contained

more than 220 million acres of wetland habitat.

Although government programs, conservation

organizations, and private individuals are slowing

wetland loss and restoring degraded wetlands, the total

wetland acreage in the lower 48 states has declined to

the current 107 million acres. The nation’s wetlands are

vital to fish health. Wetlands provide an essential link

in the life cycle of 75 percent of the fish and shellfish

commercially harvested in the United States, and up

to 90 percent of the recreational fish catch. Wetlands

provide clean water, a consistent food supply, shelter,

and nursery areas for both marine and freshwater

species. Salmon, winter flounder, and largemouth bass,

among others, depend on healthy wetlands.

Largemouth bass (Micropterus salmoides) is the most popular game fish in the

United States. Shallow marshes at the edges of lakes and floodplain wetlands of

large, slow moving rivers are favorite habitats for the largemouth bass. Stocking

largemouth in smaller ponds and recreational lakes has been a common sport

fishery management practice in many states. Image courtesy of FWS.

57

By providing essential habitat and other benefits to fish

populations, wetlands play a crucial role in maintaining

the long-term health of our aquatic resources and

contribute to economic prosperity. Sport fishing is

responsible for a multi-million dollar industry that

supports television shows, magazines, fishing clubs

and organizations, tackle and boat manufacturing and

fishing tournaments held nationwide. In total, wetland-dependent

species make up 71 percent of the commercial

and recreational fisheries, supporting an industry that

contributes $111 billion annually to our national economy

and employs two million people (Fisheries and Water

Resources Policy Committee 2004).

How Wetlands Support Healthy Fish Populations

Clean Water

Wetlands have been termed “nature’s kidneys” because

they filter and purify our streams, rivers and waterways.

Wetlands slow down

moving water, allowing

sediments suspended in

the water to gradually

settle to the ground.

Cattails (Typha spp.)

and other ermergent and

submergent vegetation

help remove dangerous

heavy metals, like

copper and arsenic,

from the water column.

Other pollutants, like

lead, mercury and

pesticides, are trapped

by soil particles and are

gradually broken down

by microbes. Wetland

plants and microorganisms

also filter out and absorb

excess nutrients that

can result from fertilizer

application, manure, and

municipal sewage. When large amounts of nitrogen

and phosphorus enter our waterways, a massive

overgrowth of algae can occur, depleting dissolved

oxygen levels and stressing fish populations. Wetlands

can remove more than half of the phosphorous and 75

percent of the nitrogen out of the incoming water flow

(U.S. Environmental Protection Agency 1993) This

natural filtering ability reduces the negative impacts

of agricultural and municipal run-off, and it lessesns

the need to implement costly technological solutions.

For example, if half of all the existing wetlands were

destroyed, it would cost over $62 billion per year to

upgrade sewage treatment plants to handle all the extra

pollution (Environmental Defense Fund and World

Wildlife Fund 1992) Some types of wetlands are so good

at this filtration function that environmental managers

construct similar artificial wetlands to treat storm water

and wastewater near urban centers.

58

Sockeye salmon (Oncorhynchus nerka) spend their life in open sea, but return

to freshwater streams to spawn. These fish support one of the most important

commercial fisheries on the Pacific coast. Image courtesy of FWS.

Northern Pike (Esox lucius) and Muskellunge (Esox

masquinongy) are found in heavily vegetated wetlands

in the shallow waters along the edges of lakes and

large rivers. These are some of North America’s most

important freshwater game fish species. Image courtesy

of FWS.

Food Production

The diverse conditions found in wetlands allow

many different types of organisms, some with

highly specialized adaptations, to co-exist within a

small area. This wide range of species is supported

by the extraordinary rates of plant productivity

that characterize most wetland habitats. Some fish

species benefit directly by feeding on plant parts,

while other fish eat the small insects and crustaceans

that live on plants. Some fish prefer wetland plant

material that forms the detritus found on the bottom

of aquatic habitats. Wetlands indirectly nourish the

entire aquatic system when this rich organic matter is

washed downstream, where it benefits fish living many

miles away in the open ocean. Menhaden (Brevoortia

tyrannus), for example, rely upon detritus for a full

third of their diet, even though they live far from the

wetlands where it is produced.

Spawning and Nursery Areas

Fish eggs and young fish have different needs. Some fish

live in other habitats as adults and return to wetlands

to lay their eggs. Defenseless and immobile eggs can

be hidden from predators by underwater vegetation.

Wetland plants and detritus provide a surface for some

fish to attach their eggs. When the eggs hatch, the

vegetation becomes both a protective cover and a food

source. Young fish dart into the wetland vegetation to

hide, while the juvenile stages of bay scallops, hard

clams, and some other shellfish cling to salt marsh

vegetation and seagrasses for several weeks before

settling on the bottom. Most shrimp harvested in the

Gulf of Mexico depend on salt marshes for nurseries, yet

this latest study reports that these salt marsh wetlands

continued to decline by over 33,000 acres (13,450 ha)

between 1998 and 2004.

Refuge

Both adult and juvenile fish use wetlands to hide from

predators. Thick plant growth can visually confuse

predators and disguise small fish. Juvenile muskellunge,

northern pike and other and mottled colored fish can

hide by blending in with surrounding aquatic vegetation.

Dense vegetation and shallow water prevent many

pelagic predators from entering coastal marshes and

freshwater wetlands fringing lakes and rivers. Anchovies

(Engraulis mordax), juvenile snook (Centropomus

undecimalis), and juvenile spotted seatrout (Cynoscion

nebulosus) dart into the intertwining root systems of

mangrove wetlands to escape larger predators. The

root systems of trees and shrubs in floodplain wetlands

allow stream banks to hang over the water, providing

protective habitat for Chinook salmon (Oncorhynchus

tshawytscha), cutthroat trout (Oncorhynchus clarki),

and other fish.

Fish also use wetlands to seek refuge from changes in

water level, velocity, or bad weather. Coho salmon rely

on the calmer waters of forested wetlands adjacent to

streams to escape fast currents during winter floods.

Wetland plants help maintain appropriate levels of

oxygen in the water and keep temperatures cool for

aquatic life.

59

Rainbow trout, Onchorhynchus mykiss.

Image courtesy of FWS.

Black Crappie (Pomoxis nigromaculatus) and White Crappie (Pomoxis

annularis) use submerged vegetation and brush as spawning habitats. Image

courtesy of FWS.

Management and conservation for all aquatic resources

are a shared responsibility. Agencies, organizations and

individuals must continue to be involved in wetlands

and fisheries conservation activities to protect these

important resources.

Leah Miller and Suzanne Zanelli, Izaak

Walton League of America

www.iwla.org

Some of the information in this article was taken from the

publication Wetlands and Fish: Catch the Link, produced by

the Izaak Walton League and the National Marine Fisheries

Service. You can download this publication at http://www.

nmfs.noaa.gov/habitat/habitatconservation/publications/

hcpub.htm

6600

Brook trout, Salvelinus fontinalis

Image courtesy of FWS.

Photos courtesy of FWS.

Freshwater

Wetland

Resources

Freshwater, or palustrine, wetlands

included forested wetlands,

freshwater emergents, shrubs, and

freshwater ponds less than 20 acres

(8 ha). Freshwater wetlands have

been known by many common names

such as swamp, bog, fen, marsh,

swale, oxbow and wet meadow.

Ninety five percent of all wetland

area in the conterminous United

States was freshwater. In 2004, there

were an estimated 102.5 million

acres (41.5 million ha) of freshwater

wetlands. Table 5 summarized the

changes in freshwater wetlands

between 1998 and 2004.

Gains and Losses in Freshwater

Wetlands

There have been large shifts

between the freshwater wetland

types and uplands. Most wetland

loss (e.g. drainage, fills) and wetland

creation and restoration that

occurred between 1998 and 2004

involved some type of freshwater

wetland.

All net gains in wetland area took

place in freshwater systems. Overall,

the estimated net gain in freshwater

wetland area between 1998 and 2004

was 220,200 acres (89,140 ha).

Freshwater wetland gains resulted

from wetland restorations and the

creation of numerous freshwater

ponds (Figure 38). The status of

freshwater ponds is discussed later

in this section.

Wetland Restoration—Between

1987 and 1990, programs to restore

wetlands under the 1985 Food

Security Act added about 90,000

acres (36,400 ha) to the nation’s

wetland base (Dahl and Johnson

1991). Between 1986 and 1997, there

was a net gain of wetland from

“other” uplands of about 180,000

acres (72,900 ha) (Dahl, 2000).

During those previous study periods

wetland restoration and creation was

not sufficient to overcome wetland

losses. From 1986 to 1997, there was

a deficit between freshwater wetland

losses and gains of about 630,000

acres (255,100 ha). This was due to

freshwater wetland conversion to

upland land uses (Dahl 2000).

The federal government works

cooperatively with landowners,

states, tribes and communities

through a number of programs to

achieve restoration, protection and

improvement (see Appendix D). One

of the primary wetland restoration

programs of the Fish and Wildlife

Service is the Partners for Fish and

Wildlife Program. This program has

been available to private landowners

and has provided both technical

and financial assistance to restore

wetlands and other fish and wildlife

habitats. Examples of restoration

projects include restoring wetlands,

planting native trees and grasses,

removal of exotics, prescribed

burning, reconstruction of stream

habitat and reestablishment of fish

passageways (www.fws.gov/partners

2005).

Another restoration program of

the Fish and Wildlife Service is

the North American Waterfowl

Management Plan (NAWMP),

a public-private approach to

managing waterfowl populations.

Cooperation and coordination with

partners and stakeholders is key

to implementation of NAWMP

Table 5 Changes in freshwater wetland area between 1998 and 2004. The coefficient of variation (CV) for each entry

(expressed as a percentage) is given in parentheses.

Area, in Thousands of Acres

Freshwater Wetland Category Estimated Area,

1998

Estimated Area,

2004

Change,

1998–2004

Change

(in Percent)

Freshwater Emergent 26,289.6

(8.0)

26, 147.0

(8.0)

–142.6

*

–0.5

Freshwater Forested 51,483.1

(2.8)

52,031.4

(2.8)

548.2

(56.1)

1.1

Freshwater Shrub 18,542.2

(4.1)

17.641.4

(4.3)

–900.8

(34.2)

–4.9

Freshwater Vegetated Wetlands 96,314.9

(3.0)

95,819.8

(3.0)

–495.1

(35.0)

–0.5

Ponds1 5,534.3

(3.7)

6,229.6

(3.5)

695.4

(13.1)

12.6

Miscellaneous Types2 384.4

(16.3)

404.3

(15.6)

19.9

(54.2)

5.2

Freshwater Non-Vegetated 5,918.7

(3.7)

6,633.9

(3.5)

715.3

(12.8)

12.1

All Freshwater Wetlands 102,233.6

(2.9)

102,453.7

(2.8)

220.2

(77.3)

0.2

* Statistically unreliable.

1Includes the categories: Palustrine Aquatic Bed and Palustrine Unconsolidated Bottom.

2Palustrine Unconsolidated Shore.

Percent coefficient of variation was expressed as (standard deviation/mean) x (100).

61

Figure 38. Approximate density and distribution of freshwater wetland gains identified in the samples of this study.

Figure 39. A tile drained wetland basin has been restored. Ohio, 2005.

62

Wetland Gain

0–50 Acres

51–100 Acres

101–250 Acres

251–600 Acres

Figure 40. Wetland

restoration (freshwater

emergent) on land

previously classified as

upland “other.” Indiana,

2005. Photo by

M. Bergeson.

and to successfully protect and

conserve waterfowl through

habitat protection, restoration,

and enhancement. The habitat

objectives of NAWMP identify

key waterfowl habitat areas and

call for their conservation and

protection. Working with partners

and cooperators NAWMP seeks

to enhance, protect and restore

wetlands that contribute to those

waterfowl habitat objectives.

Over the past decade, many agencies

and organizations have been actively

involved in wetland restoration,

enhancement or creation. Many

beneficial projects have been

completed by federal, state, local

and private organizations and

citizens. Some of these projects

have involved removal of invasive

species in wetlands, restoration

of hydrology to partially drained

habitats, selective plantings and

reestablishment of vegetation,

improved wetland quality and other

habitat improvement activities.

These wetland enhancement

projects have not contributed area

gains to the wetland base and were

not part of this study.

An estimated 564,300 acres (228,460

ha) of wetlands were restored on

agricultural lands between 1998

and 2004. However, the loss of

wetlands to agricultural land use

was responsible for an estimated

488,200 acres (197,650 ha) during the

same period. The net gain of about

76,100 acres ( 30,800 ha) did not tell

the entire story of wetland restored

or created from agricultural

land. As lands became enrolled

in retirement or conservation

programs, they were subsequently

re-classified to the upland “other”

land use category (e.g. there were no

identifiable land use characteristics).

Thus, some areas attributed to

wetland restoration were actually

conversions of upland agricultural

land to the upland “other” category.

Replacement of wetland with a

structure (house or office building)

or development resulting from urban

or suburban infrastructure (roads

and bridges), usually constituted

an irreversible loss (Ainslie 2002).

It follows that most restoration and

creation of freshwater wetlands

would have to come from the

agricultural sector or undeveloped

lands classified as “other.” The

“other” lands category also included

many conservation lands such

as undeveloped land on National

Wildlife Refuges, in state game

management areas or preserves,

idle lands or land in retirement

programs planted to permanent

cover, as well as national and state

park lands (Figure 40). This trend

of gaining wetland acres from the

“other” land use category was seen

in the previous era study where

180,000 acres (72,900 ha) of “other”

land was converted to wetland (Dahl

2000).

63

The Council on Environmental

Quality (2005) provided an

assessment of wetland restoration

and creation by federal programs

that showed 58 percent of

the acreage was attributed to

agricultural conservation and

technical assistance programs and

about 32 percent was attributed

to other federal initiatives such as

those completed on conservation

lands.

The National Resources Inventory

conducted by the U.S. Department

of Agriculture estimated a total net

change of 263,000 acres (106,470

ha) in freshwater and estuarine

wetlands on nonfederal land from

Figure 41. Wetland restoration attributed to agricultural conservation programs in the upper midwest, 2004. The wetland can be

seen in the center with light green and white vegetation, darker irregular shape is surface water with vegetation.

1997 to 2003 (USDA—NRCS 2004).

Despite subtle differences and

nuances between that study and

this study and different timeframes,

there was general agreement

between the studies with regard to

wetland trends due to agriculture.

Agricultural conservation programs