What are Wetlands?
Wetlands are unique and varied ecosystems. An old farm
adage, “too thick to drink and too thin to plow,” gives a
hint both of the nature of wetlands and the lack of value
attributed to them in the past. But thanks to the work of
scientists and conservationists, we now know how to
define wetlands and understand the important functions
they provide.
The Great Lakes Basin is fortunate to contain a diversity
of wetland types ranging from broad expanses of coastal
marsh to small isolated bogs. Although each wetland is
unique, they share three interrelated characteristics:
1) The presence of water at or near the land surface for a
long enough portion of the year to influence the type of
vegetation that can grow there;
2) The presence of plants adapted to living in soils
saturated with water (hydrophytic – or water-loving –
vegetation); and
3) The presence of distinctive soil types which develop
under saturated conditions (hydric soils).
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Credit: Wisconsin Wetlands Association |
Marsh
When people hear the term wetland, they most commonly
think of a marsh. Marsh is a term that represents a
broad array of wetlands that are dominated by grass-like
vegetation such as rushes, sedges, and cattails. They are
wet areas that can be periodically covered by standing or
slow-moving water and are usually associated with
ponds, rivers, streams, inland lakes, and the Great Lakes.
Swamp
Swamps provide very important habitat for a wide
array of wildlife throughout the year. Swamp is simply
the technical term for a wooded wetland. The soils in
swamps are usually rich in nutrients and are generally
saturated periodically at some point during the
growing season.
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Credit: USFWS |
Bogs and Fens
Although different in their water chemistry and source,
bogs and fens are often grouped into a broad category
called northern peatlands. Bogs are isolated from ground
and surface water and contain acidic waters. Fens receive
water that has passed through mineral soils rich in
limestone and therefore contain somewhat alkaline
waters. Both bogs and fens contain plants that are
uniquely adapted to their water chemistry and occur as
thick peat deposits in old lake basins or as blankets of
peat across the landscape.
Why are Wetlands Important?
Historically, wetlands were seen as areas that were better
drained or filled. In a classic example of “you don’t know
what you’ve got ‘til it’s gone,” we have come to
understand wetlands as ecologically important and complex
systems only after many wetlands have been lost.
Billions of dollars are spent each year in the Great Lakes
Basin on hunting, fishing, birdwatching, hiking, and
camping activities that rely directly on the creatures that
call wetlands home.
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Credit: Wyman Meinzer/USFWS |
Wetlands Provide Fish and Wildlife Habitat
Wetlands provide critical habitat for fish and wildlife.
Nearly all fish in the Great Lakes Basin directly rely on
wetlands for spawning, feeding, or taking cover.
Waterfowl and other birds, and a wide range of mammals
forage, reproduce, and find shelter in wetlands. More
than one-third of all threatened or endangered animal
species in North America depend on wetland areas.
Wetlands Protect Water Quality
Wetlands act as living filters that remove pollutants,
nutrients, and sediments from surface water and ground
water. By protecting water quality, wetlands keep our
lakes, streams, and ground water healthy and support the
wide range of uses that rely on clean water.
Wetlands Contribute to our Water Supply
Wetlands are usually found where the ground water
table reaches or is close to the land surface. They are
often sites of springs or seeps where ground water is
discharged and are very important for providing high
quality water for our lakes and streams. Because
wetlands store water and release it slowly, they play an
important role in maintaining flow in streams. In addition, some wetlands are found where water seeps
back into the earth and recharges ground water,
providing a source of clean drinking water. The water
recharge potential of a wetland varies according to a
variety of factors, including wetland type, geographic
location, subsurface geology, soil type, and amount of
precipitation.
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Credit: Ryan Hagerty/USFWS |
Wetlands Protect Shorelines and Control Erosion
In their natural condition, wetlands associated with rivers
and lakes function as a barrier to erosion. The root
systems of wetland plants stabilize soil at the water’s
edge and enhance soil accumulation at the shoreline.
Wetland vegetation along shorelines reduces erosion by
dampening wave action and slowing the speed of
water currents. When wetland and shoreline vegetation
is removed, efforts to control erosion and sedimentation
can be expensive and usually result in further
degradation of fish and wildlife habitat.
Wetlands Protect Us from Floods
Wetlands act as sponges, temporarily storing flood
waters and releasing them slowly, thus reducing flood
peaks and protecting downstream property owners from
flood damage. Wetlands and adjacent floodplains often
form natural floodways that convey flood waters from
upland to downstream points. These functions become
increasingly important in urban areas where development
has increased the rate and volume of stormwater
runoff. Each year, many communities that have suffered
extensive wetland loss experience severe flooding.
Wetlands Contribute to Food and Fiber Production
In addition to the revenue generated from wetlands by
hunting, fishing, and trapping wildlife, wetlands provide a
variety of natural products including blueberries,
cranberries, and wild rice. Wetland grasses are hayed in
many places for winter livestock feed. Forested
wetlands, such as cedar swamps, can provide sustainable
yields of valuable timber if harvested with careful
management and planning. However, commercial
activities, such as peat mining, logging, livestock grazing,
and cranberry cultivation can severely degrade wetlands
and a majority of their functions if not conducted on a
small scale with the utmost of care.
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Credit: Wisconsin Wetlands Association |
Education and Research
Wetlands serve as wonderful outdoor classrooms,
providing excellent opportunities for discovery and
living examples of nearly all ecological principles.
Boardwalks and observation platforms have been
constructed in many wetlands across the Great Lakes
Basin to facilitate educational activities.
A Valuable, Yet Threatened, Resource
Although the functions that wetlands provide make
them our most valuable landforms, the United States and
Canada have lost alarming amounts of wetland habitats.
According to a study by the U.S. Fish and Wildlife Service,
the lower 48 states have lost over 53% of their original
wetlands. Great Lakes states and the province of Ontario
have fared worse – it’s estimated that only 30% of the
original wetlands remain in the Great Lakes Basin.
There have been no comprehensive studies to document
and assess the overall ecosystem impacts of these
significant wetland losses. However, one needs only to
consider the increases in flood damage, the degraded or
impaired lakes and rivers, the number of threatened and
endangered species, and myriad other indicators of poor
ecosystem health to get an idea of the impacts.
To this day, wetlands continue to be degraded or
converted to other uses. Each year, government agencies
receive dredging and filling permit or zoning applications
to authorize activities that degrade wetlands in the
Great Lakes Basin. The vast majority of these permits or
zoning applications are issued. On top of this intense
pressure, there are numerous other activities that
degrade wetlands with little or no regulatory
oversight, including drainage projects, polluting wetlands
with contaminated runoff, and land clearing and logging.
These continued threats to Great Lakes wetlands
underscore the critical importance of citizen
involvement in protecting them.
Prepared in February 2004 by Tip of the Mitt Watershed Council for Freshwater Future,
a project of the Tip of the Mitt Watershed Council. Funding provided by E.P.A. Great Lakes Grants Program, National Fish
and Wildlife Foundation, and U.S. Environmental Protection Agency.
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