VANISHING LANDS: Sea Level, Society and
Chesapeake Bay
Review by Nancy C. Wilson
Sea level in the Chesapeake Bay has been rising and falling for
the last several million years, changing by as much as 300 feet
as massive glaciers advanced and retreated across North America.
The changes continue today, strongly correlated with global temperatures.
A recently published handbook, "Vanishing Lands: Sea Level, Society
and Chesapeake Bay," documents the forces that have changed the
shape and depth of the Bay in the past and the frighening implications
for the future. Colorful diagrams and maps and striking photographs
show such features as the drowning of Poplar Island and the penetration
of salt water into upland corn fields.
The handbook accompanies an award-winning documentary film, "Vanishing
Lands," produced by Stephen Leatherman, Director of the University
of Maryland's Coastal Research Laboratory. It was written by Leatherman
and a colleague at the Lab in collaboration with three members
of the Chesapeake Bay Office of the US Fish and Wildlife Service.
At just under 50 pages and written in an informative but not too
technical style, it is appropriate for Bay residents, schools
throughout the State of Maryland, and - as the Bay is a microcosm
of sea level rise impacts worldwide-is an excellent resource for
an international audience.
Land disappears slowly with erosion and submergence; society as
a whole has ignored sea level rise and these impacts on the Chesapeake
Bay. The effects of coastal storms, waves and tides are far more
noticeable. The gradual process of sea level rise is not yet a
concern to most elected officials and the public and as a result
long-term planning has not yet occurred.
In the short term, engineering and technological solutions to
sea level rise such as bulkheads and breakwaters have looked economically
feasible. But these are expensive erosion control measures which
when summed over the whole Bay area, aggravate rather than ameliorate
the sea level rise problem. And bulkheads will do nothing to stop
submergence from higher water levels. Meanwhile, greenhouse gas
concentrations increase, temperatures are higher, beaches are
eroding, wetlands are being lost, population is expanding and
coastal ecosystems are suffering damage. Sea level is predicted
to rise three feet during the next century.
Until the 1600s the Bay watershed was covered with lush vegetation,
roots held the soil and canopies of dense leaves tempered the
wind and rain. The history of discernible human impact on the
watershed began some 300 or 400 years ago when the first wave
of European colonists cleared 20 percent of the land. By mid-nineteenth
century thousands of acres of oak forest were cleared for corn
and tobacco. Eventually these fields were depleted and abandoned;
millions of tons of soil no longer held by roots or protected
by foliage washed into the Bay. Buildup of silt became such a
problem that the county seat at Joppatown on the Gunpowder River
was moved to Baltimore.
Sediments from the early agricultural erosion settled as mud flats
on sandy shores, marsh grasses took root and new wetlands were
created. At present, however, soil conservation restricts erosion,
and dams accumulate sediment in reservoirs behind barriers. More
land is disappearing than being created.
Coastal land loss now is a major issue as more and more people
move closer to the water's edge. Sea level rise has accelerated
and in the future may slightly exceed today's rate. Demand for
water to serve the growing population leads to drilling of deeper
wells, failure of the aquifers, and subsidence.
The cost of preventing loss of land along the shores is high.
Historic towns and the ports of Annapolis and Baltimore have been
fortified with bulkheads and revetments. But the primary response
on the Eastern Shore has been submergence of upland areas and
the drowning of marshes.
The real hope for the future is development of new marshes. But
Eastern Shore residents see the penetration of brackish water
plants as the loss of good agricultural land. It is true that
the shrinking of arable land reduces the yield of corn and other
crops. However, the authors argue, there is ample agriculture
space available elsewhere and "defensive measures such as bulkheads
are not justified because of the high cost of protecting low-lying
land."
Residents of the islands of the Chesapeake Bay discovered the
hopelessness of fighting rising seas when their lands were overcome
by salinization, erosion and submergence, and they retreated to
the mainland. The handbook lists 13 islands which have been lost
completely - the most recent was Sharps which drowned in 1962
- and seven more have lost from 20 to 90 percent of their acreage.
The largest island, Smith, which had more than 11,000 acres in
1849, was down to 7,800 in 1987. The population has dropped from
800 in 1910 to 400 today.
If we want to save the precious values of the Chesapeake Bay,
there are two complementary avenues we can follow: 1) prevent
the continuing buildup of greenhouse gases, and 2) "prepare civilization
for the accelerated rise in sea level." The first route requires
the measures familiar to those who are concerned with climate
change such as reforestation, reducing energy consumption and
promoting energy efficient technologies, and most important, curbing
population growth.
The second route will require a completely new way of designing
and planning the land we occupy as a society. "Without commitment
to responsible long-term planning, society will be burdened forever
with the slow destruction of shore front homes and coastal infrastructure."
This extremely difficult approach involves protecting higher ground
if feasible or retreating from eroding and submerging shores to
allow the marshes to migrate landward. Unless long-term planning
includes zoning, open space and buffers, society will have to
pay for continual losses of very valuable and expensive waterfront
real estate.
One catastrophic coastal storm will alert everyone to the cost.
There have been about 15 major hurricanes, tropical and extratropical
storms since 1915, with storm surges - the most dangerous part
of a hurricane - swelling from two to more than seven feet. During
these storms, larger waves break closer to shore, greatly increasing
erosion and property destruction. "Warmer ocean temperatures,"
the handbook warns, "may boost hurricane intensity and perhaps
frequency."
Governments, industry and private citizens may help by reestablishing
fringe marshes with riprap, and restoring natural habitats through
various programs such as the Wetlands Reserve, Partners for Wildlife,
Waterfowl Habitat Improvement. Extreme drawing down from aquifers
is recognized as a problem in the handbook and was brought out
as an important factor in the Chesapeake Bay Conference. Excessive
groundwater withdrawal has caused land subsidence, and exploration
of new ways to obtain water could be a very constructive measure,
although the handbook does not mention it as a specific mitigating
factor,
Each decision must be backed with information, education and
research, "made in the ethics of sound conscience." Limitations
and incentives may be established by legislation." All responses
to sea level rise," the handbook concludes, "must be decided
for the good of society and the long-term health and vitality
of the Chesapeake Bay."
(The handbook is available free from the U.S. Fish and Wildlife
Service, 410/573-4562. A teacher's guide is forthcoming
from the same source.
To order a videocassette of the film, "Vanishing Lands,"
send check or money order - $32.95 for personal use, $72.95
for institutions - to University of Maryland Foundation, c/o
Laboratory for Coastal Research,1113 LeFrak Hall, University
of Maryland, College Park, MD 20742.)
