July 10th USGCRP Seminar on "Wetland Losses in the United States: Scope, Causes, Impacts, and Future Prospects"
tsocci at usgcrp.gov
Mon Jul 7 13:00:13 EDT 1997
U.S. Global Change Research Program Seminar Series
Wetland Losses in the United States:
Scope, Causes, Impacts, and Future Prospects
>From an historical perspective, what percentage of natural wetlands in the
U.S. have been lost or significantly altered? What portion of wetland
changes have been due to natural forces and what portion due to the direct
and indirect consequences of human activities, including climate change?
What are the implications of wetland losses in terms of the health and
availability of natural resources and ecosystem services to humans and
other species? What is the outlook for the future?
Thursday, July 10, 1997, 3:15-4:45 PM
Rayburn House Office Bldg., Room B369, Washington, DC
Dr. Rosina Bierbaum, Assistant Director for the Environment, White House
Office of Science and Technology Policy, Washington, DC
Dr. Mark Schaefer, Deputy Assistant Secretary for Water and Science, U.S.
Department of the Interior, Washington, DC
Dr. Virginia Burkett, Chief, Forest Ecology Branch, National Wetlands
Research Center, U.S. Geological Survey, Department of the Interior,
America's Wetland Resource
>From an ecological and societal perspective, wetlands are among the most
important natural habitats in the United States. Their importance stems
from aesthetic values like a sense of open space. Wetlands also serve as
ecologically important habitat and spawning grounds for a multitude of fish
and wildlife species. From a societal perspective, wetlands are even more
important for the economic value they provide in the form of sustainable
fisheries, natural flood control, groundwater cleansing and replenishment,
natural cleansing of agricultural and urban runoff, and countless other
services and functions.
Historically, wetlands occupied 11 percent of the surface area of the lower
48 states just 200 years ago. Today they cover about 5 percent of the
surface area. Data from the Fish and Wildlife Service's National Wetlands
Inventory also indicate that interior wetland water regimes are more
numerous than coastal wetlands, although both are uniquely important from
an ecological and social or resource perspective. In its first wetland
report to Congress in 1982, the National Wetlands Inventory (NWI) found
that 9.2 million acres of wetlands had been lost nationwide between the
1950s and 1970s. The average annual net loss rate during this time was
458,000 acres annually; 87% of that loss was due to agriculture. In its
second report to Congress in 1991, NWI reported that 2.6 million wetland
acres were lost nationwide between the 1970s and 1980s. The net loss rate
over this interval of time was 290,000 acres annually; agriculture remained
the single largest reason for the loss. In its most recent analysis, NWI
found that the rate of wetland loss continues to decline.
Various federal laws and policies dating from the mid-1800s have encouraged
and facilitated wetland loss. Only in the past 30 years have there been
serious efforts on the part of government to curtail the net annual wetland
loss rate. In recent years, a concerted effort has been directed at
wetland restoration as part of a national goal of "No Net Loss" of wetland
resources. In most instances, resource managers have been successful in
restoring water to the land, but have only been successful about half the
time in replacing all the functions and services provided by the original
Coastal Wetlands and Global Climate Change
The potential impacts of climate change on wetlands are of great practical
concern. Among the coastal areas of greatest risk in the United States are
those low-lying coastal habitats that are easily eroded and which occur
along the northern Gulf of Mexico and southern Atlantic coasts of the U.S.
These coastal wetlands are especially vulnerable to direct, large-scale
impacts of climate change, primarily because of their sensitivity to sea
Observational records indicate that sea level has already risen between 10
and 25 cm globally, over the past 100 years. In addition, the
Intergovernmental Panel on Climate Change (1995) has projected a sea level
rise of 15-95 cm as a consequence of global warming. Sea level rise will
also increase the depth of coastal waters and increase inland and upstream
salinity intrusion, both of which affect fresh and brackish-water wetlands.
While the influence of global warming on the frequency and intensity of
storm events is uncertain, sea-level rise alone has the potential for
increasing the severity of storm surges, particularly in areas where
coastal habitats and barrier shorelines are rapidly deteriorating. These
direct consequences of global-and regional-scale changes will increase the
vulnerability of coastal wetlands (including mangrove and salt marshes)
which are already heavily impacted by human activities.
Predicted changes in sea level will also dramatically alter the community
composition and aerial coverage of submerged aquatic seagrass beds. Field
studies off the coasts of Mississippi and Louisiana have shown, for
example, that barrier island overwash events are a major determinant
of seagrass community composition in the Chandeleur Sound, which
contains some of the largest grassbeds in the Gulf region. Because different
species of seagrass support different organisms, changes in the
composition of seagrasses will be felt at every level of the food web,
which includes shellfish, finfish, waterfowl (particularly redhead ducks,
which depend almost entirely on seagrasses for their winter diet), and people.
Farther inland, salinity intrusion becomes more important than disturbance
in controlling the species in submerged grassbeds. Some species have a higher
tolerance to salt water and will quickly outcompete those that are salt
intolerant. Other species may be completely eliminated, or may possibly
be displaced inland depending on the rate at which sea level rises.
Most of the southeastern coastal zone is highly developed, however, and the
inland migration of seagrassses and salt marshes will be prevented in many
areas by the existing infrastructure of roads, seawalls, and other human
Analyses of sites in five coastal states indicate that many marshes and
mangrove ecosystems receive adequate mineral sediments to produce enough
organic sediment and root material to remain above sea level at the present
rate of sea level rise (1-2 mm per year globally). However, three of the
twelve wetlands studied were not keeping pace with the current rate of
sea-level rise. If sea-level rise accelerates, some additional sites would
also begin to slowly deteriorate and submerge. In some areas, the sinking
or subsidence of the marsh system, coupled with human development, is the
major cause of wetland loss.
In Florida, Louisiana, and South Carolina, submergence and/or salt water
intrusion have been implicated in the decline in productivity, and death, of
certain coastal forests. However, restoration of salinity-impacted baldcypress
swamps, for example, may be possible by cultivating more salt-tolerant
strains of baldcypress. Studies in Texas have also shown that changes in
global climate would affect bottomland hardwood forests and other forests
of the coastal plain by possibly influencing patterns of disturbances, such as
fires or storms, and by altering the regional moisture balance. Such
changes would affect resources in both preserved and commercial forests of
the coastal plain.
Model simulations of the combined influence of sea level rise, storms, and
floods suggest that large areas of the southeastern United States could be
converted from coastal marsh to open water, and from forest to marsh.
Hurricane model simulations also suggest that if hurricanes or the effects of
hurricanes become more intense over the next century, wetland community
structure and composition would be altered. For example, historical
simulations suggest that the occurrence of major hurricanes is the most
important factor controlling mangrove community dynamics.
Dr. Mark Schaefer is presently the Deputy Assistant Secretary for Water and
Science at the U.S. Department of the Interior, where he works on policy
issues related to the work of the U.S. Geological Survey and the Bureau of
Reclamation. From 1993 to 1995, he served as Assistant Director for
Environment in the White House Office of Science and Technology Policy,
where he was responsible for a variety of domestic environmental science,
technology, and education issues. In this capacity he led the
Administration's initiative to develop a national environmental technology
strategy, an 18-month effort to achieve a broad national consensus on
approaches to advancing the development, commercialization, and application
of these technologies. He has also served as co-leader of an
Administration effort to interact with the private sector and the states to
develop a national blueprint for environmental education. In addition, he
worked on a range of regulatory science issues, chairing the Risk
Assessment Subcommittee of the Committee on the Environment and Natural
Resources, a group charged with better coordinating approaches to
evaluating risk within the federal government.
Dr. Schaefer previously served for three years as Senior Staff Associate
and Director of the Washington Office of the Carnegie Commission on
Science, Technology, and Government, where he contributed to a number of
studies related to environmental and science policy. He was a staff member
at the then-Congressional Office of Technology Assessment (OTA) from
1987-1989, first as a Congressional Science Fellow and then as project
director of OTA's study of the effects of toxic substances on the nervous
system. For five years beginning in 1988, he taught an environmental
policy seminar for Stanford University's "Stanford in Washington" program.
A biologist by training, he received a B.A. degree from the University of
Washington, and a Ph.D. degree from Stanford University. After completing
his undergraduate degree in 1977, he worked for five years in the U.S.
Environmental Protection Agency's Office of Research and Development.
Dr. Virginia Burkett is Chief of the Forest Ecology Branch at the National
Wetlands Research Center (NWRC) of the Department of the Interior, where
she has worked since1990. She supervises a team of forest scientists,
ecologists and computer modelers who conduct research related to the
ecology, management and restoration of forested wetlands. Her expertise
includes wetland forest ecology and restoration, coastal wetland ecology,
coastal management and wildlife/fisheries management. Her current
research involves bottomland hardwood regeneration in frequently flooded
sites of the Mississippi River floodplain. Dr. Burkett also coordinates NWRC's
Global Change Research Program. Prior to her work at NWRC, she served
as Secretary/Director of the Louisiana Department of Wildlife and Fisheries
(1988-90), having previously served as Deputy Director (1984-85). Prior
to those appointments, she directed the Louisiana Coastal Zone Management
Program and served as Assistant Director of the Louisiana Geological Survey
for 5 years.
Dr. Burkett has been appointed to several boards and commissions during her
22-year career, including the Louisiana Forestry Commission, the Gulf of
Mexico Fishery Management Council, the Gulf States Marine Fisheries Commission,
and the Louisiana Seafood Marketing Board. She was elected Vice President
of the Southeastern Association of Fish and Wildlife Agencies in 1989. During
1988-1990, she co-chaired the Louisiana Oil Spill Task Force and chaired the
Louisiana Artificial Reef Council. From 1991-93, she was chairman of the 130-
member Consortium for Research on Southern Forested Wetlands. She is a
member of the Board of Directors of the Louisiana Wildlife Federation, and
also currently holds a Visiting Professorship at Stephen F. Austin State
University, where she teaches a course on professionalism and ethics.
Dr. Burkett received her master's degree in botany from Northwestern State
University (1975) and her doctoral degree in forestry (D.F.) from Stephen
F. Austin State University (1996).
The Next Seminar is scheduled for Monday, September 15, 1997
Planned Topic: Model Projections of the Climate Response to the Long-Term
Buildup of CO2
For more information please contact:
Anthony D. Socci, Ph.D., U.S. Global Change Research Program Office, Code
YS-1, 300 E St., SW, Washington, DC 20546 Telephone: (202) 358-1532; Fax:
(202) 358-4103 E-Mail: TSOCCI at USGCRP.GOV.
Additional information on the U.S. Global Change Research Program (USGCRP)
and this Seminar Series is available on the USGCRP Home Page at:
http://www.usgcrp.gov. Normally these seminars are held on the second
Monday of each month.
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