Wetlands
The definitive website on plants & horticulture
There is clear water up to your ankles
and a dragonfly zips past your head as you watch some ducks fly off
the water - welcome to the soggy world of the wetland!
Wetlands are difficult to define
because of their great variation in size and location. The most
important features of wetlands are: Waterlogged soils or soils
covered with a shallow layer of water (permanently or seasonally),
unique types of soil, and distinctive plants adapted to
water-saturated soils. Marshes, bogs, swamps, vleis and sponges are
examples of wetlands. |
Wetland Basics | Ponds
| Streams
| Bogs and Fens
Marshes
| Pollution | Wetlands
Wetlands
WHY ARE
WETLANDS IMPORTANT?
* Flood
busters:
Wetlands associated with streams and
rivers slow floodwaters by acting as giant, shallow bowls. Water
flowing into these bowls loses speed and spreads out. Plants in the
wetland play an important role in holding back the water. The
wetland acts as a sponge as much of the flood water is then stored
in the wetland and is slowly released to downstream areas, instead
of it all rushing to the sea within a few days. This greatly reduces
flood damage, particularly erosion, and ensures a more steady supply
of water throughout the year.
*
Filters:
Wetlands improve water quality as they
are very good natural filters, trapping sediments, nutrients (e.g.
nitrogen and phosphorus), and even pathogenic (disease-causing)
bacteria. In addition, pollutants such as heavy metals (e.g.
mercury, lead) and pesticides, may be trapped by chemical and
biological processes. In other words, the water leaving the wetland
is cleaner than the water entering it.
*
Wetlands and wildlife:
Wetlands are filters
where sediments and nutrients accumulate, so many plants grow there,
e.g. bulrushes, grasses, reeds, waterlilies, sedges and trees. The
plants, in turn, provide food and a place for attachment and shelter
for many creatures. There is more life, hectare for hectare, in a
healthy wetland than in almost any other habitat. These productive
places support huge numbers of insects, fish, birds and other
animals. Some animals are completely dependant on wetlands, whilst
others use wetlands for only part of their lives. The wetlands
of the United States are of international importance as they are
the breeding destination for many migratory wading
birds.
* People
and wetlands:
Wetlands have been
used for centuries as grazing for domestic stock, and as a source of
reeds used for thatching, hut construction and basket weaving. They
are provide fishing, hunting and the opportunity to observe
wildlife, especially birds. Wetlands are appreciated for their
beauty as open spaces and also for their educational value.
| Wetlands are classified by the
U.S.D.I. Fish and Wildlife Service in a comprehensive
hierarchical method that includes five systems and many
subsystems and classes. The method is explained in the
Classification of Wetlands and Deepwater Habitats of the
United States (Cowardin 1979). This classification method
includes the marine system and the estuarine system which are
ocean based systems and beyond the scope of this document. The
other systems are the riverine, lacustrine and palustrine
systems. The riverine system includes freshwater wetlands
associated with stream channels, while the lacustrine system
includes wetlands associated with lakes larger than 20 acres.
The palustrine system includes freshwater wetlands not
associated with stream channels, wetlands associated with
lakes of less than 20 acres and other wetlands bounded by
uplands. Most forested wetlands are in the palustrine
system. |
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| Wetlands can be more simply classified into
three broad categories of wetland types, based on the growth
form of plants: (1) marshes, where mostly nonwoody plants such
as grasses, sedges, rushes, and bullrushes grow; (2) shrub
wetlands, where low?growing, multi?stemmed woody plants such
as swamp azalea, highbush blueberry and sweet pepperbush
occur; and (3) forested wetlands, often called swamps or
wooded wetlands, where trees are the dominant plants. |
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However, these classification systems may be less than
ideal for the purposes of this publication. Information more
useful for protecting and enhancing the values of forested
wetlands may be based on a knowledge of soils, hydrology and
plant and animal communities present. General information of
this type will be presented on the following pages for
forested wetlands and other types of wetlands most often
encountered in association with forest management operations
in the Northeastern Area.
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| David Welsch /
U.S. Forest Service |
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1999 -
All Rights Reserved