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What are wetlands?

Tree Talk: Here’s a look at the four different kinds of wetlands and what they do for the environment.

Fredric Miller

February 23, 2023

3 Min Read
Vibrant view of green trees in forest

Historically, wetlands were very common in Illinois, before many were converted into farmland and urban development. Those wetlands served a purpose and provided ecosystem services.

According to U.S. EPA, a wetland is an area where water covers the soil or is present either at or near the surface of the soil all year or for varying periods of time during the year, including during the growing season. More simply put, a wetland is a transitional ecosystem between land and water.

The chronic saturated soils promote development of hydric or wetland soils. Wetlands vary widely because of regional and local differences in soils, topography, climate, hydrology, water chemistry, vegetation and other factors. Wetlands may be found from the tundra to the tropics and on every continent except Antarctica.

In wetlands, water saturation is the dominant factor. The hydrology of the area largely determines soil development and the types of plants and animals that live in or on the soil, which may consist of both aquatic and terrestrial organisms. Soil water saturation promotes the growth of hydrophytic plants such as bald cypress, duckweed, water lily, pickerel weed, cattails, wooly sedge, soft-stem bulrush, royal fern and water horsetail, just to mention a few.

Wetland wildlife includes waterfowl like ducks and geese, kingfishers, sandpipers, and a wide variety of fish. Common wetland mammal residents are otters and beavers.

4 kinds of wetlands

Not all wetlands are created equal. There are generally four different types of wetlands:

Marshes. Like the Everglades, marshes are wetlands that are frequently or continually inundated with water and consist of soft-stemmed vegetation.

Swamps. Swamps are similar to marshes but are dominated by woody plants, and water levels may fluctuate annually. A good example is the Cache River swamp in southern Illinois.

Bogs. This unique type of wetland consists of spongy peat deposits, is fed by precipitation and has acidic water.

Fens. Fens are similar to bogs but are fed by groundwater and are not as acidic.

So why are wetlands so important? Wetlands provide unique habitat for a variety of plants and animals, but equally and even more important, they act as a huge filter by trapping pollutants such as phosphorus and heavy metals in their soils. They fix nitrogen for easier plant uptake and help trap and break down bacteria from livestock production.

Studies have shown that water entering a wetland is much “cleaner” when it exits the wetland. Additionally, wetlands help with modifying climate change by storing carbon — at the rate of 50 times more than rainforests. They do this by reducing gases, reducing costs associated with water treatment and storing carbon in sediments.

As you can see, wetlands provide numerous very important ecosystem benefits, and where possible, we should strive to preserve them.

For more information on wetlands and their preservation, contact your local Extension office or soil conservation service.

Miller is a horticulture professor at Joliet Junior College in Joliet, Ill., and a senior research scientist in entomology at The Morton Arboretum in Lisle, Ill. Email your tree questions to him at [email protected].

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Land Management
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