Wetlands

There are many types of wetlands in Minnesota, each with widely varying characteristics. Some wetlands are dry for much of the year; others are almost always covered by several feet of water. Some wetlands have grasses and sedges, shrubs, or trees. They may be small confined basins or extend for hundreds of miles.

It is estimated that Minnesota has lost about 50 percent of its original wetland acreage.

Benefits of wetlands

Erosion control: Wetland vegetation reduces wave damage along lakes and stream banks.
Flood control: Wetlands can slow and retain runoff water, reducing the frequency of flooding along streams and rivers.
Groundwater recharge and discharge: Some wetlands recharge groundwater by holding surface water and allowing it to slowly filter into the groundwater reserves. Some wetlands are discharge areas; they receive groundwater even during dry periods, and help maintain flows in nearby rivers and streams.
Water quality: Wetlands protect the water quality of downstream lakes, streams and rivers by removing pollutants.
Rare species habitat: 43 percent of threatened or endangered species in the U.S. live in or depend on wetlands.
Recreation: Wetlands area a great place to canoe, hunt, fish or watch wildlife.
Economic value: Wetlands provide economic commodities such as wild rice and bait fish.

Bogs

Bogs, or peatlands, are wetlands with soils made of peat. Peat is the partially decomposed remains of plants. Northcentral Minnesota has among the most extensive peatlands in the lower 48 states.

Soil/hydrology: Peat soil, with the water table at or near the soil surface year-round.
Vegetation: Woody, herbaceous, or both supporting a spongy covering of moss. Typical plants are shrubs, sphagnum mosses, sedges, leatherleaf, Labrador tea, cranberry, and cottongrass; may also include stunted black spruce and tamarack.
Common sites: Mostly on shallow glacial lake basins and depressions, flat terrains and along sluggish streams.
Visit: Lake Bemidji and Hayes Lake state parks and the Big Bog State Recreation Area.
Classifications:
- Circular 39: Type 8
- NWI (Cowardin) Symbols: PF02, 4, and 7B; PSS2, 3, 4, and 7B
- Eggers and Reed: Bogs
- Native Plant Community Classification: APn, FPn, FPs, FPw, OPn

Marshes

Shallow and deep marshes are familiar wetlands to Minnesotans. These water-filled basins, with a mix of open water and emergent and submergent vegetation, provide food and resting areas for migratory birds and many species of wildlife. In southern Minnesota these wetlands are often called prairie potholes.

Shallow marshes

Soil/Hydrology: Organic or mineral soil, usually waterlogged and often covered with 6-inches or more of water.
Vegetation: Grasses; bulrush; spikerush; and marsh plants such as cattail, arrowhead, pickerelweed and smartweed.
Common sites: May fill shallow lake basins or sloughs; may border deep marshes, lakes and river backwaters on landward side.
Classifications:
- Circular 39: Type 3
- NWI (Cowardin) Symbols: PEMC and F, PSSH, PUBA and C
- Eggers and Reed: Shallow Marsh
- Native Plant Community Classification: MRn, Mru, MRs

Deep marsh

Soil/Hydrology: Organic or mineral soil, inundated in most years with six inches to three feet of water.
Vegetation: Cattail, reed, bulrush, spikerush and wild rice. Open areas may have pondweed, naiad, coontail, watermilfoil, waterweed, duckweed, waterlily and spatterdock.
Common sites: May fill shallow lake basins, potholes, limestone sinks and sloughs. May border open water in lakes and river backwaters.
Classifications:
- Circular 39: Type 4
- NWI (Cowardin) Symbols: L2ABF, L2EMF and G, L2US, PABF and G, PEMG and H, PUBB and F
- Eggers and Reed: Deep Marsh
- Native Plant Community Classification: MRn, Mru, MRs

Shallow open water

This wetland type includes shallow ponds, lakes and reservoirs. Due to their value for wildlife, many of these wetlands are specially designated and managed under the DNR's Shallow Lakes Program.

Soil/Hydrology: Organic or mineral soil, usually with 3- to 10-foot deep water.
Vegetation: Fringe of emergent and floating leaf vegetation similar to marshes; submergent vegetation such as pondweed, naiad, coontail and watermilfoil.
Common sites: Shallow lake basins and may border large open water basins.
Classifications:
- Circular 39: Type 5
- NWI (Cowardin) Symbols: L1; L2ABG and H; L2EMA, B, and H; L2RS; L2UB; PABH; PUBG and H
- Eggers and Reed: Shallow Open Water
- Native Plant Community Classification: Portions may be MRn, Mru, MRs; open water areas are not classified under this system

Swamps

Shrub and wooded swamp wetlands are found along the edges of lakes, rivers and streams, and in glacial lake basins. Shrub swamps are common throughout the state.

Shrub swamp

Soil/Hydrology: Organic or mineral soil. The water table is at or near the surface and may be covered with as much as six inches of water.
Vegetation: Includes alder, willow and dogwood.
Common sites: Along sluggish streams, drainage depressions and occasionally on floodplains.
Classifications:
- Circular 39: Type 6
- NWI (Cowardin) Symbols: PSSA, C, F, and G; PSS1, 5, and 6B
- Eggers and Reed: Shrub-Carr, Alder Thicket
- Native Plant Community Classification: FPn73, WMn82, WMs83, WMp73

Wooded swamp

Soil/Hydrology: Organic or mineral soil. The water table is at or near the surface during much of the growing season and may be covered with as much as one foot of water for shorter periods.
Vegetation: Hardwood and coniferous swamps with tamarack, northern white cedar, black spruce, balsam fir, balsam poplar, red maple and black ash. Deciduous sites frequently support beds of duckweed and smartweed.
Common sites: Shallow ancient lake basins, old riverine oxbows, flat terrains, and along sluggish streams.
Visit: The black ash and black spruce forests in Scenic, Wild River and Lac qui Parle state parks.
Classifications:
- Circular 39: Type 7
- NWI (Cowardin) Symbols: PFO1, 5, and 6B; PFOC and F
- Eggers and Reed: Hardwood Swamps, Coniferous
- Native Plant Community Classification: WFn, WFs, WFw, FPn, FPs, FPw

Wet meadows (including calcareous fens)

These wetlands are characterized by low-growing grass, sedge or rush communities with various broad-leaved plants. They include wet prairies and calcareous fens and may be found along the borders of streams, lakes and marshes, in small depressions, and in extensive flats on glacial lake beds.

Calcareous fens are a rare type of wet meadow support by constant upwelling groundwater rich in calcium carbonate. With their specialized hydrology and chemistry, they often support rare plant species. Calcareous fens receive special protection under the Minnesota Wetland Conservation Act.

Wet meadow/wet prairie

Soil/Hydrology: Organic or mineral soil, saturated or nearly saturated during most of the spring and summer; usually without standing water.
Vegetation: Grasses, sedges, rushes and broad-leaved plants.
Common sites: May fill shallow basins, sloughs, or farmland sags. May border shallow marshes on the landward side of glacial lake beds.
Classifications:
- Circular 39: Type 2
- NWI (Cowardin) Symbols: PEMB
- Eggers and Reed: Sedge Meadow, Fresh (Wet) Meadow, Wet to Wet-Mesic Prairie, Calcareous Fen
- Native Plant Community Classification: WMn, WMs, WMp, OPp91

Calcareous fens

Soil/Hydrology: Non-acidic, sedge-derived peat; nearly always saturated due to constant, upwelling groundwater; scattered small pools and rivulets present.
Vegetation: Grasses, sedges, rushes, shrubs and board-leaved plants; many rare species.
Common sites: Calcareous fens are found along the beach ridges of Glacial Lake Agassiz in northwest Minnesota, at the base of river terraces along the Minnesota River Valley, and in the karst region of southeast Minnesota.
Classifications:
- Circular 39: Type 2
- NWI (Cowardin) Symbols: PEMB, PSSB
- Eggers and Reed: Calcareous Fen
- Native Plant Community Classification: OPp93, OPn93

Seasonally flooded wetlands

These wetlands generally contain water for relatively short periods, primarily in spring or after heavy rains. They include small, shallow basins supporting annual plants and floodplain forests. Because they are dry for much of the year, seasonally flooded wetlands are often farmed. They are valuable food sources in the spring for migrating waterfowl and shorebirds. When left intact, these wetlands provide breeding habitat for amphibians. Floodplain forests help protect and maintain the water quality of their associated rivers and streams. These wetlands are found throughout Minnesota.

Seasonally flooded basins

Soil/Hydrology: Generally mineral soils, usually well-drained during much of the year but waterlogged or inundated during variable seasonal periods, especially in the spring.
Vegetation: Grasses, sedges and annual plants such as smartweeds, beggar ticks and wild millet.
Common sites: Upland depressions
Classifications:
- Circular 39: Type 1
- NWI (Cowardin) Symbols: PEMA, PUS
- Eggers and Reed: Seasonally Flooded Basins
- Native Plant Community Classification: WMs92, WMp73

Floodplain forests

Soil/Hydrology: Generally mineral soils, usually well-drained during much of the year but waterlogged or inundated during variable seasonal periods, especially in the spring.
Vegetation: Flood-tolerant tree species such as silver maple, cottonwood and American elm; often sparse understory but includes jewelweed, clearweed and nettles.
Common sites: Along rivers and streams.
Classifications:
- Circular 39: Type 1
- NWI (Cowardin) Symbols: PFOA
- Eggers and Reed: Floodplain Forest
- Native Plant Community Classification: FFn, FFs

Wetland classification methods

Over the years, classification methods have been developed to categorize and describe wetland types.

Cowardin: The Cowardin system is the classification system used by the National Wetland Inventory to describe wetlands and ecologically related deep water habitats. It is a hierarchical classification organized into ecological systems, classes, and subclasses. The class and subclass levels are primarily based on plant community or substrate. The system also provides information on water regime and a variety of other special cases.
- Classification of Wetlands and Deepwater Habitats of the United States
Circular 39: Circular 39 is an older classification system developed primarily for the inventory and classification of waterfowl habitat. Wetlands are classified based on the frequency and depth of inundation as well as vegetation community. This classification system has 20 different wetland types; eight of these types are present in Minnesota. This classification is referenced in a number of Minnesota statutes.
- Wetlands of the United States - Circular 39
Eggers and Reed Wetland Plant Communities: This classification system is based on the Wetland Plants and Plant Communities of Minnesota and Wisconsin. Wetlands are categorized into 15 plant communities.
- Wetland plants and plant communities of Minnesota and Wisconsin
Hydrogeomorphic (HGM): The hydrogeomorphic system classifies wetlands not based on their plant communities, but rather based on their geomorphic setting (i.e. landscape position), water source, and hydrodynamics. It was originally developed to help evaluate wetland functions. There are six HGM wetland classes in Minnesota, but there can be many subclasses.
- A Hydrogeomorphic Classification for Wetlands
Landscape, Landform, Water Flow Path, Waterbody Type (LLWW): This classification system is an adaptation of HGM for GIS wetland inventory and assessment. The LLWW classification system is used to perform watershed-based preliminary assessments of wetland function.
- Dichotomous Keys and Mapping Codes for Wetland LLWW Descriptors
Native Plant Community Classification: Developed by the DNR, the NPC classification addresses both wetland and upland native plant communities. It also includes detailed descriptions of the various types of wetland plant communities found in Minnesota.
- Minnesota's Native Plant Communities

Wetland publications

The Wetlands Program is also responsible for the development of statewide comprehensive wetlands management plan. The Minnesota Wetlands Conservation Plan sets directions for managing and regulating the state's wetlands and examines the way to consolidate the many different existing wetland programs. Other program documents include the Minnesota Wetland Mitigation Banking Study, the Action Planning Workbook, a Memorandum of Agreement for Implementation of the Minnesota Wetlands Conservation Plan and Wetland Guidance for the Anoka Sandplain.

Calcareous Fens

Program contacts

Jennie Skancke, Wetlands Program Coordinator, 651-259-5721.