Swamps, marshes, bogs, and fens–most people believe these words all refer to the same thing. But most people would be wrong. All four are different types of wetland (a habitat that is characterized by standing water or high water saturation), and each differ from each other in unique ways. Read on to learn how to differentiate between these types of wetlands, and why this matters.
Swamps are often the category of wetland people are most familiar with. Or, it just may be the name that most people associate with wetlands of any kind. According to the Wisconsin Wetland Association, “a swamp is any wetland that is dominated by woody vegetation (trees and/or shrubs)”. Swamps can be of the coniferous variety or of the deciduous, hardwood variety, depending on the type of trees that dominate the landscape. Common trees that are found in swamps include tamarack pines, northern white cedar, black ash, red maple, and birch trees. The soil in a swamp is saturated with water during the growing season, with standing water present occasionally throughout the year.
On the other hand, marshes are often saturated with water year-round. Shallow marshes may only have standing water during the spring and summer from rain and snowmelt, but deeper marshes may be fed by both groundwater and surface water and therefore have standing water year round. One of the main identifying characteristics of marshes is the plant matter. The vegetation that makes up a marsh is soft-stemmed plants, such as cattails, bulrushes, and bur-reeds. Because of this, marshes provide critical habitat for many species of migratory birds in Wisconsin and Minnesota.
Marsh at Crex Meadows State Wildlife Area
Photo Credit: Katrina Schlicker, Wild Rivers Conservancy
Yet another type of wetland that is present in Minnesota and Wisconsin are bogs. According to the EPA, bogs “are characterized by spongy peat deposits, acidic waters and a floor covered by a thick carpet of sphagnum moss”. Because of their high acidity levels, bogs are very low in nutrients and therefore are home to many unique species that can tolerate the extreme conditions. For instance, carnivorous plants, such as the purple pitcher plant, are often are found in bogs because they can’t get their nutrients from the soil and instead get it from the insects they ingest.
Purple Pitcher Plant (Sarracenia purpurea)
Fens are often compared to bogs. However, the main distinguishing factor of a fen is that their main water source is drainage from mineral-rich groundwater. Fens are ecologically important because they are home to many different species of rare plants. For instance, in Minnesota, the state endangered Hairy fimbry is known to only be found in two locations, and both locations are calcareous fens. Additionally, Minnesota’s state flower, the showy lady slipper, is often found in fens.
Why Does this Matter?
As you already may have gathered, wetlands are a truly unique and essential ecosystem type. Wetlands provide habitat for many unique species and therefore promote biodiversity. Marshes, for instance, are critical for migratory birds such as sandhill cranes and Canada geese because they provide food and shelter during their annual migration. Additionally, fens provide the correct conditions for many rare plant species, including sedges and rushes.
Another reason why wetlands are important is because they prevent extreme flooding events by absorbing precipitation. By providing a space where rainwater can go, wetlands keep water from spilling into our cities and towns, and therefore also prevent destruction from erosion. Additionally, wetlands act as water filters by trapping pollutants from runoff, such as phosphorus and heavy metals.
And, in a day and age where climate change is more impactful than ever, wetlands are valuable because they are known to absorb carbon. According to WWF, wetlands “...can store 50 times more carbon than rain forests, helping to keep the heat-trapping gas that contributes to climate change out of the atmosphere”. Wetlands do this by trapping organic debris in the sediment below the surface of the water.
Therefore, it is of the utmost importance to protect the wetlands we have left in order to be able to enjoy them for generations to come.
For more information on wetlands and wetland protection, check out these resources: