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



* 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. p09pic1

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. 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.

Joe Emerick

David Welsch / U.S. Forest Service

Joe Emerick