Type 3 Wetlands: Shallow Marshes

wetland restorationwetland types
Written By Kristin Shardlow

Although commonplace, a shallow marsh is a highly regarded ecosystem that supports diverse wildlife and provides essential services for people and ecosystems alike.

Understanding Shallow Marshes

One of the most familiar of all types of wetlands, shallow marshes are prevalent throughout the Midwest. The inland, or non-tidal, shallow marsh exists by filling in shallow lake basins or sloughs and often borders Type 4: Deep marshes, Lakes or River Backwaters. Overall, shallow marshes are wetter than Type 1 (Seasonally Flooded Wetlands) and Type 2 (Wet Meadows), as the soils in shallow marshes are waterlogged and are covered with roughly 6 inches of standing water for most of the year. Shallow marshes can have permanently and semi-permanently flooded areas, and include the subtype prairie potholes within their classification. 

Looking at shallow marshes, one can begin to identify a mix of both terrestrial and aquatic vegetation. Due to the higher likelihood of standing water and increased species diversity, Type 3 Wetlands typically have stricter regulations that protect them from degradation.

Characteristics specific to Type 3 Wetlands

Soil Profile: Shallow marshes are composed of mostly mineral and organic soils that have undergone gleying (a soil formation process that occurs under waterlogged, anaerobic conditions which cause iron compounds to be reduced or removed). As a result, the soils of shallow marshes often display blue, green, gray colorations.

Vegetation: Varying types of emergent and submergent species are found within a shallow marsh ecosystem. Common wetland species such as broad-leaf cattail, rushes, sedges, bur-reeds, smartweeds, arrowhead and duckweed are also prevalent in shallow marshes. At the deepest points within a shallow marsh, aquatic plants like bladderwort and pondweed species can be identified as well. 

Fauna: Many migratory birds rely on shallow marshes for habitat and sources of food. With standing water being more consistently available, shallow marshes also support more amphibian and reptile species. Songbirds like the red-winged blackbird and mammals like the muskrat call shallow marshes home as well.

Functions & Benefits

The functions and characteristics of a shallow marsh wetland provide valuable ecological services to the areas they exist within. Shallow marshes also offer interesting opportunities for the people that interact with them. Listed below are just some of the of the many benefits of shallow marsh wetlands:

Flood Mitigation & Erosion Control: Type 3 wetlands reduce the likelihood of flood damage by slowing and storing runoff during heavy precipitation events. Capturing run-off in a sponge-like manner, shallow marshes prevent erosion and protect shoreline habitat in surrounding areas.

Water Quality & Infiltration: The vegetation of shallow marshes, and their ability to retain surges of water, allows for water in other ecosystems to properly infiltrate through the soil. This percolation recharges the groundwater table and filters any accumulated sediments and pollutants in the water. By retaining and gradually dispersing water, shallow marshes serve to maintain overall water quality.

Habitat & Species Diversity: The unique blend of aquatic and terrestrial features offered by marshland can supply a variety of habitats for multiple species, including those that are recognized as threatened or rare. Spanning from pollinators to birds and mammals, a shallow marsh is one of the most diverse habitats that exists today.

Economic & Recreational Value: Aside from the immense value they add to the environment, shallow marshes support desirable human activities as well. Hunting and trapping is popular in shallow marsh wetlands due to the richness of its biodiversity, most notably in terms of waterfowl abundance. Shallow marshes are also excellent places of recreation, offering picturesque areas for kayaking and canoeing.

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Mitigation Partners, Inc. Founders Dax Dickson & Tory Christensen

Kristin Shardlow
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Type 2 Wetlands: Wet Meadows
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Type 4 Wetlands: Deep Marshes