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Case Study

Pintail duck photo by Peter LaTourette

Chesapeake Bay and
Assateague Island

Rising Seas, Changing Climate

When Captain John Smith and his crew
sailed up Chesapeake Bay on the mid-
Atlantic coast in 1608, they passed a large,
low-lying island in the upper middle
reaches of the bay, about 34 nautical miles
south of today's Baltimore. Poplar Island, as
it became known, covered more than 1,400
acres in Smith's time. The island eventually
supported a small town, and later—in the
1930s and 1940s—an exclusive retreat for
politicians, including Presidents Franklin D.
Roosevelt and Harry Truman.

If Captain Smith could repeat his
Chesapeake voyage today, he might be
surprised to see what remains of Poplar
Island. Instead of the substantial body of
land he encountered in 1608, Poplar Island
now consists of a small group of islets that
together measure less than 5 acres. Dead
trees rise from the water to mark where
land stood only a few years before.

Rising seas and heavy erosion have flooded
and eaten away more than 99.5 percent of
Poplar Island during the past 150 years.

With the shoreline retreating by more than
13 feet annually, the island's remnants
would have vanished under the sea by the
year 2000 if it weren't for a $427 million
restoration program launched in 1998 by a
coalition of federal, state, and
nongovernmental agencies.

Poplar island's story is not unique. The
University of Maryland's Laboratory for
Coastal Research found that at least 13
islands in Chesapeake Bay have
disappeared entirely since the region was
first described and mapped by Europeans.
Many more islands are in danger of
drowning as the sea continues to rise. Even
Captain Smith's namesake island near the
mouth of the Potomac, which is large
enough to support three small towns and a
population of close to 400 people, has lost
some 30 percent of its land since 1850.
The formerly wooded tract is now a group
of low-lying, mostly marshy islands, if
scientists' predictions are accurate, Smith
Island will be lost to the sea during the

Global warming could have a major
impact on the region's bird life, including
migratory waterfowl that overwinter in
Chesapeake Bay.

Sea level rise might cause Assateague
Island to become narrower and move
landward.

PRO^°

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Case Study — Chesapeake Bay and Assateague Island

next century, along with a way of life for
its watermen and crabpickers.

Why is the sea rising ? Global warming
causes water at the surface of the ocean to
expand and adds sizable quantities of
freshwater runoff from melting glaciers
and ice sheets. In areas where the land is
sinking due to changes in the Earth's crust,
the effects of rising seas are even more
pronounced. In the Chesapeake Bay area,
scientists believe global warming accounts
for about 6 inches of the sea level rise that
has occurred in the past 100 years. Natural
geologic subsidence of land, possibly
exacerbated by the compaction of
sediments as people withdraw excessive
amounts of groundwater, may have
contributed another 6 inches to sea level in
the past century. The region's sea level as
recorded by tide gauges is now more than
a foot higher than it was in 1890.

EPA estimates that with additional global
warming and continued subsidence, sea
level in the Chesapeake Bay area probably
will rise another 8 inches by 2025, 13
inches by 2050, and 27 inches by 2100,
compared with the level in 1990. Such a
rate of sea level rise would be
approximately double that of the preceding
century. There is even a small risk—a 5
percent chance based on current computer
models—that the sea will rise as much as
44 inches by 2100.

For the past 5,000 years, the average rate
of sea level rise in Chesapeake Bay was
approximately 3 feet per 1,000 years.
During the 21st century, global warming
could cause the bay's level to rise at a rate
closer to 3 feet per 700 years.

Marshes and
Beaches at Risk

Rapid sea level rise could be devastating
for most of Chesapeake Bay's islands,
marshes, and beaches. The loss of these
habitats in turn would affect birds, fish,
terrapins, and other wildlife. The future
Chesapeake Bay might lose some of its
charm for the thousands of kayakers,
boaters, anglers, windsurfers, and birders
who spend time on and around the bay
each year.

Salt marshes can keep up with moderate
increases in sea level but may be drowned
if the sea rises faster than sediments and
peat can build up the marsh. In low-lying

areas like the Eastern Shore or Virginia's
Back Bay National Wildlife Refuge, new
marsh develops naturally as rising seas
flood the land. Similarly, beaches are able
to migrate inland. But many Eastern Shore
residents are armoring their property
against the sea by building sea walls,
bulkheads (retaining walls), and
revetments (rocks piled along the shore).
These structures prevent marshes and
beaches from moving inland as the sea
rises. Since 1980, Chesapeake Bay
residents have built bulkheads and
revetments along 350 miles of shoreline. If
this trend continues, many of the bay's
beaches and marshes will be lost, squeezed
between the rising tide and the armored
shore.

Captain Smith might be thoroughly
astonished by a sail through Chesapeake
Bay in the year 2100. He would hardly
recognize the landscape before him. If
present trends continue, the "many isles"
described in his writings will have
vanished, along with most of the marshes
and beaches.

"We are once again at the threshold, as we were in the
1970s, facing the decline of the Chesapeake Bay."

— Sarah J. Taylor-Rogers, Assistant Secretary,

Maryland Department of Natural Resources, October 18, 1996

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Case Study — Chesapeake Bay and Assateague Island

Chesapeake Bay
Region

~ Some of the areas that
could be flooded at high
tide if global warming
causes sea level to rise
2 feet by 2100.

LJ Areas that might be inun-
dated over a period of sev-
eral centuries.

The indicated areas account not
only for the effects of global
warming, but also for other
effects such as tidal variations
and land subsidence.

Other Changes In Store

The loss of marshes, beaches, and islands
are only some of the potential impacts of
global warming in the Chesapeake Bay
region. Other changes also are possible,
including warmer temperatures, increases
in precipitation, more frequent and more
damaging floods from coastal storms,
lower oxygen levels in the bay, and lower
water quality. Not all of the changes may
be harmful: for example, an increase in
rainfall could bolster the region's
freshwater supply. Scientists cannot
predict future climate or its effects with
certainty, but the best research available
today suggests that global warming could
have significant impacts on the mid-
Atlantic region.

The diverse habitats of Chesapeake Bay
and its surrounding watershed —including
underwater grass beds, salt marshes,
forested wetlands, and upland forests-
provide homes for more than 2,700 species
of animals and plants. Many of these
habitats will be affected by climate change.

During the past 100 years, the average
temperature in the mid-Atlantic region has
risen by nearly 1 °F, and precipitation has
increased by up to 10 percent. Compared
with today's temperatures, climate models
project that the region's climate may
become approximately 2°F warmer by

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Case Study — Chesapeake Bay and Assateague Island

2030, with an additional 3°F to 8°F average
temperature increase by the end of the 21st
century. Models project that precipitation in
the region also will increase during the next
100 years.

More precipitation might bring more
freshwater and nutrient runoff into
Chesapeake Bay, which may reduce the
bay's salinity and the amount of oxygen
available for fish and other aquatic life.
High nutrient levels can lead to algal
blooms, reducing the water's clarity and
the amount of light available to
submerged aquatic vegetation. Excess
nutrients also stimulate the growth of
algae on the leaf blades of submerged
vegetation, further reducing the amount
of light available to the plants for growth.

What is Global Warming?

The Earth's climate has changed in the past, and will continue to change naturally in the future. Ice ages,
long warm periods, and short-term fluctuations in temperature and precipitation are all elements of
the global climate's natural variability.

Today, the average global temperature is rising. Is that natural? Some of the temperature increase can
be explained by natural factors. But many scientists believe that a portion of the warming trend may be
caused by humans. Human activities are creating a buildup of greenhouse gases—primarily carbon
dioxide, methane, and nitrous oxide—in the atmosphere.The heat-trapping property of these gases is
undisputed. Although scientists do not know exactly how the Earth's climate responds to increases in
greenhouse gases, they do know that the current warming trend is consistent with changes that would
be expected from the increase in greenhouse gases.

Scientists generally believe that the burning of fossil fuels and other human activities are the primary
reason for the increased concentration of carbon dioxide in the atmosphere. Fossil fuels burned to run
cars and trucks, heat homes and businesses, and power factories are responsible for almost 99 percent
of U.S. anthropogenic carbon dioxide emissions and about 20 percent of our nitrous oxide emissions.
Of the carbon dioxide emissions, industrial activity accounted for 33 percent in 1997. Personal and
commercial transportation accounted for 30 percent, and residential and commercial energy use
accounted for 19 and 16 percent, respectively. Increased agriculture, deforestation, landfills, industrial
production, and mining also contribute a significant share of carbon dioxide, methane, and other
greenhouse gas emissions.

Average global temperatures at the Earth's surface have increased 0.6-1.2°F since the late 19th century.
The 10 warmest years in the 20th century all occurred in the last 15 years. Snow cover in the northern
hemisphere,floating ice in the Arctic Ocean, and the areas covered by mountain glaciers have all
decreased. Globally, sea level has risen 4-10 inches during the past century. Worldwide precipitation
over land has increased by about 1 percent, and the frequency of extreme rainfall events has increased
throughout much of the United States.

Although it is impossible to predict future changes in climate with certainty, many scientists believe
that the continued addition of greenhouse gases to the atmosphere is likely to raise the Earth's average
temperature by several degrees in the next 100 years. Rising global temperatures are expected to raise
sea level and change precipitation and other local climate conditions. Changing regional climate could
alter forests, crop yields, and water supplies. It also could threaten human health and harm birds, fish,
and many types of ecosystems.

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Case Study — Chesapeake Bay and Assateague Island

Finally, high nutrient levels in the bay may
be linked to outbreaks of the toxic
organism Pfiesteria, which some scientists
believe killed many bay fish in 1997.

Oysters also may suffer if bay waters
become fresher. The enormous volume of
freshwater that entered Chesapeake Bay
from Tropical Storm Agnes in 1972 killed
an estimated 2 million bushels of market-
size oysters and eliminated most oyster
larvae in the bay.

On the other hand, sea level rise may cause
water in the bay to become saltier,
encouraging the spread of oyster diseases.
Warmer water temperatures, especially in
winter, are also linked to oyster diseases.
The oyster diseases MSX and Dermo are
caused by warm-water parasites.

Chesapeake Bay has very low levels of
dissolved oxygen, due in part to the heavy
load of nutrients from agricultural runoff
and municipal wastewater treatment
discharges in the freshwater that flows
into the bay. The low oxygen levels make
life difficult for fish and other aquatic
animals. Global warming may make it even
harder for them to survive. For each
degree Fahrenheit that the bay's water
warms, the capacity of water to dissolve
oxygen decreases by about 1.1 percent.
Higher water temperatures also raise the
metabolic rates—and hence the oxygen

requirements —of cold-blooded aquatic
animals, such as invertebrates and fish.

Warmer waters could be harmful for
Chesapeake Bay species that are at the
southern end of their range, such as the
soft clam. But warming also could help
warm-water species at the northern end of
their range survive by reducing the
severity of cold snaps during winter.

Higher sea levels would allow storm surges
to penetrate farther inland than they do
today, placing more structures and people
at risk.

Finally, the impacts of climate change will
come on top of the many stresses that
already affect plants and animals in
Chesapeake Bay, such as excess sediment
and nutrients, overharvesting, toxic
pollutants, and habitat loss from land
development by humans.

What Can Be Done?

To address the threat of climate change,
first we have to understand the risks.

Many scientists are analyzing the potential
impacts of climate change in the
Chesapeake Bay region. Their findings will
help identify the areas of risk to people,
animals, and plants in the bay, Assateague

Island, and other important ecosystems in
the area.

Efforts to restore the bay, such as the
federal-state Chesapeake Bay Program, can
help reduce current stresses on life in the
bay and make natural ecosystems more
resilient to some impacts of climate change.

The Maryland and Virginia state
governments could help coastal areas
adapt to rising sea levels by enacting plans
indicating the areas that will be protected
and those that will be abandoned to the
sea. Some areas may require regulations to
prohibit revetments or bulkheads, specify
erosion-based setback rules for new
construction, or require buildings to be
moved landward as the sea rises. Other
areas may need structural protection,
landfill, or beach nourishment.

Prevention of human-induced climate
change also is an important strategy. Some
global warming probably will occur no
matter what we do, because some of it is
natural. But also, humans have become
dependent on fossil fuels. The burning of
fossil fuels emits greenhouse gases, which
may remain in the atmosphere for years,
decades, or even centuries, exacerbating
the natural warming. But we as individuals
can take action now to reduce our own
consumption of fossil fuels by improving
energy efficiency and using alternative

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energy sources. (See "Searching for
Solutions" and "What People Can Do" on
pages 8 and 9.)

Assateague Island

Assateague Island stretches along the
Atlantic coast of the Delmarva Peninsula,
between Chesapeake Bay and the ocean.
Assateague is one of many barrier islands
that rim the eastern coast of the United
States. Barriers are narrow islands that run
parallel to the continental shoreline, with a
protected bay lying between the island and
the shore. The bay shores of barrier islands
typically are lined with salt marshes.

Like other barrier islands, Assateague is
constantly changing shape and
geographical position. At one time, it lay
far seaward of where it is today.

Large undeveloped barrier islands like
Assateague are likely to narrow and "roll"
landward during the next century. Sea
level rise and storms will cause Assateague
Island to erode until it becomes narrow
enough for storms to push sand over onto
the bay side. Like a rug being rolled up, the
island will remain above sea level and roll
gradually toward the land.

The bays on the landward side of the
island —Sinepuxent and Chincoteague
Bays—will expand inland as the sea rises,
flooding the coastal plain. The future
Assateague Island and its bays may look
generally similar to what we see today, but
they will be farther inland. The birds and
other wildlife that attract so many visitors
to Assateague National Seashore and
Chincoteague National Wildlife Refuge
should still find good habitat conditions as
the island migrates landward. However,
many of today's popular visitor sites, such
as the wildlife loop road that encircles
Snow Goose Pond at Chincoteague refuge,
eventually will disappear.

Some barrier islands may not be as lucky as
Assateague: If the sea level rises too
quickly, islands can break up and drown in
place. The Isles Dernieres barrier chain
along the Louisiana coast was once a single
island. Storm erosion and a relative sea
level rise of three feet per century broke
Isle Dernier into five smaller islands that
are expected to be completely submerged

by the year 2020. Due to the rapidly
subsiding land along Louisiana's coast, the
sea level relative to the land level is rising
faster than in other parts of the country.

The northern end of Assateague may be
more vulnerable to sea level rise than the
rest of the island, as it has been sand-
starved for many decades by jetties at
Ocean City Inlet that trap the sand.
Personnel at Assateague National Seashore
are working with the U.S. Army Corps of
Engineers and the State of Maryland to
create a system that will restore sand
transport to northern Assateague.

Condominiums, hotels, shops, and other
coastal development on barrier islands will
become increasingly at risk of flooding and
storm damage as the sea rises. Ocean City,
Maryland, is built on the lower end of
Fenwick Island, which is just north of
Assateague. For the past 10 years, Ocean
City has had to bring in sand to replenish its
eroding beach. The beach needs replenishing
more frequently now than it did only a few
years ago because of increased erosion, and

"Assateague Island National Seashore is one of the most dynamic
environments administered by the National Park Service."

— Robert Dolan, Bruce Hayden, Jeffrey Heywood,

Atlas of Environmental Dynamics,

Assateague Island National Seashore, October 1977

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Case Study — Chesapeake Bay and Assateague Island

sea level rise could double the rate of erosion
in the next 30 years.

A powerful northeaster that hit the mid-
Atlantic coast in early March 1962 caused
an estimated $7.5 million in property
damage to Ocean City. A similar storm
today would cause hundreds of millions of
dollars in damage because the island has
become densely developed over the past
20 years. Future storms may cause even
more harm because storm surges and waves
will be superimposed on higher sea levels.

Blackwater National
Wildlife Refuge

Blackwater National Wildlife Refuge, on
the eastern shore of Chesapeake Bay near
Cambridge, Maryland, has the largest
concentration of nesting bald eagles on the
east coast north of Florida. The wetlands
of the wildlife refuge are vital for
migratory waterfowl and shorebirds, and
also are important for flood control and
maintaining water quality.

Blackwater is one of Chesapeake Bay's
most popular sites for birders, attracting
thousands of visitors annually.

Since 1938, one-third of the marsh at
Blackwater has disappeared due to a

combination of sea level rise and
overgrazing by nutria, large non-native
beaver-like rodents that dig canals through
the marsh and eat the vegetation. More
than 5,000 acres of marsh have been lost,
and most of the remaining wetlands are
projected to disappear within 30 years.

As the sea rises, inundation by seawater of
lowland habitats surrounding the marshes
could result in the disappearance of habitat
for migratory birds and other species, such
as the endangered Delmarva fox squirrel.
Similar impacts could occur at Back Bay
National Wildlife Refuge, south of Virginia
Beach, which contains extensive marshlands.

Waterfowl and Other Birds

Chesapeake Bay is used by nearly 1 million
ducks, geese, and swans in the winter
months, and by thousands more during
migration seasons. The bay also provides
important habitat for a variety of other
resident and migratory birds, including the
osprey, bald eagle, six coloniaIly nesting
waders (such as the great blue heron and
snowy egret), and dozens of shorebird
species. Chesapeake Bay's abundant bird
life and its proximity to major urban
centers make it a very popular destination
for birders. But in the future, global
warming could make the bay a much less

attractive place for some species of
waterfowl and other birds.

Wintering populations of many ducks have
declined in recent decades, some quite
dramatically. Overwintering Northern
pintails, for example, declined from an
average of about 40,400 birds from
1950-1959 to only 2,600 birds in
1985-1999. Other species, such as the
Canada goose, snow goose, and Brant,
have become more abundant.

Researchers believe that the population
changes are related to impacts on food
resources in and around Chesapeake Bay.
In particular, degradation of bay water
quality caused by heavy nutrient and
sediment runoff has reduced submerged
aquatic vegetation, a prime waterfowl
food, throughout much of the bay. Geese
and swans respond by switching to other
foods, such as waste corn in agricultural
fields. But species that rely on submerged
aquatic vegetation, such as the Northern
pintail, redhead, and American widgeon,
have practically disappeared from the bay.

Global warming could exacerbate these
problems if increases in precipitation lead
to greater nutrient and sediment runoff,
and if water temperatures become warmer.
Sea level rise and coastal development
could eliminate many of the marshes and
other shallow water habitats that ducks use

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in winter—reducing the wildlife that
attract many people to the area.

In addition, global warming is expected to
affect the prairie pothole region of the
north-central United States and south-
central Canada, where 50-80 percent of
North America's ducks and other
waterfowi nest. The shallow prairie
wetlands are vulnerable to drought, and
computer models indicate that global
warming is likely to bring stronger and
more frequent droughts to the prairie
pothole region.

Many ducks that overwinter in Chesapeake
Bay nest in the prairie pothole region,
including mallards, Northern pintails,
American widgeons, canvasbacks, redheads,
lesser scaups, common goldeneyes, ruddy
ducks, and buffleheads. Virtually all of the
canvasbacks that winter in Chesapeake Bay
nest in the prairie pothole region.

Chesapeake and Delaware Bays harbor the
largest concentrations of migratory
shorebirds in the western hemisphere. The
loss of bay islands, marshes, and beaches
will eliminate important shorebird habitats
and will directly affect shorebird
populations.

Changes in climate may affect inland birds as
well. According to one research study, global
warming could cause the Baltimore oriole to

shift its range northward out of Maryland.
There might be no more Baltimore orioles in
Baltimore by the year 2100.

Searching for Solutions

To address the threat of global warming,
Maryland, Virginia, and the other mid-
Atlantic states could improve the health and
resiliency of natural ecosystems, prepare for
a changing climate and rising sea level,
and/or work to limit future global warming
by reducing greenhouse gas emissions.

The Chesapeake Bay Program, a federal-
state effort launched in 1983, responds to
the problems of nutrient enrichment,
population growth, coastal development,
habitat loss and degradation, and toxic
substances. In addition, the program's
Scientific and Technical Advisory
Committee launched Chesapeake Futures,
a team of experts looking at issues related
to the bay of 2030. By working to improve
the health of the ecosystem, the
Chesapeake Bay Program may help make
the bay and its wildlife more resilient to
the future impacts of climate change.

In addition, the Federal Agencies Chesa-
peake Ecosystem Unified Plan (FACEUP)
was established in 1998 to help protect the

Chesapeake Bay region. FACEUP added
50 new commitments, such as increased
support to the states for research on
Pfiesteria.

Island and beach restoration programs also
can help mitigate the effects of climate
change and sea level rise. The Poplar Island
restoration project, led by the U.S. Army
Corps of Engineers, is designed to
reconstruct the island to its approximate
size in 1847 (1,100 acres) using
uncontaminated dredged material from
Baltimore Harbor and the Channels Federal
Navigation project. The restoration wiil
create new habitat for wildlife, including

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Case Study — Chesapeake Bay and Assateague Island

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What People Can Do

marshes, uplands, small ponds, and
wooded areas. The first phase of the 20-
year project, which included constructing
640 acres of dikes and a breakwater, was
completed in 1999.

Slowing Climate Change

Today, action is occurring at every level to
reduce, avoid, and better understand the
risks associated with global warming.

Many cities and states across the country
have prepared greenhouse gas inventories,
and many are pursuing programs and
policies that will result in reductions of
greenhouse gas emissions.

At the national level, the federal
government is working in partnership with

We all add greenhouse gases to the atmosphere whenever we use energy from fossil fuels. Residential
energy use accounted for 19 percent of overall C02 emissions from the combustion of fossil fuels in
1997, and motor vehicle use accounted for approximately 20 percent. Here are a few actions that
people can take to reduce their emissions.

Use mass transit, carpool with friends, or ride a bike whenever possible.

When it's time to replace the family vehicle, consider one that gets more miles per gallon than your
present vehicle.

If you have a small boat for fishing and recreation, run it with "human power" when possible.

When it's time to replace an appliance, look for the Energy Star® label identifying
energy-efficient models.

When buying or building a new house, an Energy Star model gives greater quality and comfort as
well as lower monthly costs. For more information, go to the Energy Star Homes web site,
www.epa.gov/homes.

¦	Buy products that feature reusable, recyclable, or reduced packaging to save the energy required to
manufacture new containers and reduce greenhouse gas emissions from landfills.

Encourage your company to join EPA programs such as Energy Star Buildings™ and Waste Wi$e
recycling programs, and to buy office equipment with the Energy Star label.

Plant trees, which absorb carbon dioxide from the air.

¦	Educate others. Let friends and family know about these practical, energy-saving steps they can
take to save money while protecting the environment.

Encourage scientific research and public discussion on global warming and solutions such as
energy efficiency and alternative energy.

businesses, states, and localities to address
global warming while also strengthening
the economy. In addition, the U.S. Global

Change Research Program coordinates the
world's most extensive research effort on
climate change.

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For More Information

The U.S. Environmental Protection
Agency's global warming site includes
detailed information on climate change,
impacts, and actions.

www.e pa .gov/g lobalwarming/

¦ A 50-page handbook, Vanishing Lands:
Sea Level, Society, and Chesapeake Bay,
is available free of charge from the
U.S. Fish and Wildlife Service.

Call 41 0-573-4562 to order a copy.
A videocassette of the award-winning
Vanishing Lands documentary film is
available from the University of
Maryland's Laboratory for Coastal
Research. For prices and information on
ordering, visit the laboratory's web site.

The Chesapeake Bay Program's web
site offers a wealth of information on
the current and future status of
Chesapeake Bay.

www.chesapeakebay.net/

The Poplar Island Restoration Project web
site provides an overview and updates on
progress in restoring the island.

www.fws.gov/r9dhcbfa/success.htm

EPA's state-specific climate change fact
sheets include information on potential
impacts in the mid-Atlantic states.

www.e pa .gov/g lobalwarming/
impacts/stateimp/

¦ The latest U.S. National Assessment of
Climate Variability and Change gives a
detailed report on the potential effects of
global warming in the United States.

www.nacc.usgcrp.gov/

www.geog.umd.edu/coastal/
index.html

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