National Water Summary- Resources 237 Wetland Resources

M innesota is famous for its many lakes; in the State, of Natural Resources, l 984), although estimates range from about however, cover more than three times the area of lakes. About one­ 5.2 million acres (Anderson and Craig, 1984) to about 7.2 million fifth of Minnesota is wetland. These wetlands provide numerous acres (Minnesota Department of Natural Resources, 1978) and de­ benefits to the people and wi ldlife of the State. Wetlands provide pend on the definition chosen for organic soil and on data compila­ control by temporarily retaining stormwater runoff, and they tion methods. Palustrine wetlands on mineral soil cover about 3.5 reduce erosion of lakeshores and streambanks. Wetlands improve million acres (Anderson and Craig, 1984). The total acreage.of downstream water quality by capturing suspended particulates, dis­ palustrine wetlands in Minnesota, both peatlands and mineral-soil solved nutrients, and contaminants such as heavy metals and agri­ wetlands, is thus about 9.5 million acres. cultural pesticides. Wetlands provide essential habitat for waterfowl, Peatlands can be categorized as either fe ns or . Sometimes furbearers, and other wildlife (Carter and others, 1979). Minnesota's the word "" is informally applied to peatlands in general, but wetlands also are especially valuable for their vegetation. Many of most peatlands in Minnesota are more properly called . Fens the State's rarest plant species and most distinctive plant communi­ are peatlands that receive nutrients from ground water or runoff that ties are found only in wetlands (Coffin and Pfannmuller, 1988). has contacted mineral soil. Fens exist statewide but are more com­ Probably the rarest type of wetland in the State is a type of peatland mon in the north, where conditions are more favorable for peat ac­ called a calcareous (fig. I). cumulation. There are many different types of fens, corresponding to the wide range of possible hydrologic, climatic, and nutrient con­ TYPES AN D DIST RI BUTION ditions. Open fens (persistent-emergent wetlands) in the conifer­ hardwood forest zone (fig. 2B) commonly have sedge-dominated Wetlands are lands transitional between terrestrial and deep­ communities. -forest fens (forested or scrub-shrub wetlands) water habitats where the water table usually is at or near the land in this zone typically are covered by larch, black spruce, or north­ surface or the land is covered by shallow water (Cowardin and oth­ ern white cedar, with an understory of low shrubs, sedges, and ers, 1979). The di stribution of wetlands and deepwater habitats in mosses (Glaser, 1992; Minnesota Department of Natural Resources, Minnesota is shown in figure 2A; only wetlands are discussed herein. 1993). Fens in the prairie and deciduous forest-woodland zones Wetlands can be vegetated or nonvegetated and are classified typically have a scattered cover of shrubs such as willow and dog­ on the basis of their hydrology, vegetation, and substrate. In this sum­ wood and a continuous ground cover of various sedges, grasses, and mary, wetlands are classified according to the system proposed by forbs (scrub-shrub or persistent-emergent wetlands). A rare type of Cowardin and others (1979), which is used by the U.S. Fish and these fens is a calcareous fen (fig. l ), which receives upwelling Wildlife Service (FWS) to map and inventory the Nation's wetlands. ground water rich in calcium carbonate. At the most general level of the classification system, wetlands are Bogs are peatlands that receive nutrients only from precipita­ grouped into fi ve ecological systems: Palustrine, Lacustrine, Riv­ tion and windblown dust. Consequently, bog water has low nutrient erine, Estuarine, and Marine. The Palustrine System includes only concentrations, and a continuous mat of sphagnum moss acidifies wetlands, whereas the other systems comprise wetlands and the water (Gorham and others, 1985). Bogs have a low diversity of deepwater habitats. Wetlands of the systems that occur in Minne­ species because few plants are adapted to these low-nutrient, acid sota are described below. conditions (Glaser and others, 198 1; Glaser, 1992). Bogs in Min­ nesota typically are peat mounds covered by black spruce with an System Wetland description understory of broad-leaved evergreen shrubs and sphagnum moss (forested wetlands). Some bogs have a stunted tree and shrub com­ Palustrine ...... Wetlands in which vegetation is predominantly trees (forested w etlands); shrubs (scrub-shrub munity (scrub-scrub wetland) near the center. Nonforested patches wetlands); persistent or non persistent emergent, of bog dominated by sedge (persistent-emergent wetlands) are less erect, rooted, herbaceous plants (persistent- and common but can occur where the peat is too wet for black spruce nonpersistent-emergent wetlands); or sub­ mersed and (or) floating plants (aquatic beds). Also, intermittently to permanently flooded open-water bodies of less than 20 acres in which water is less than 6.6 feet deep. Lacustrine ...... Wetlands within an intermittently to permanently flooded lake or reservoir. Vegetation, when pres­ ent, is predominantly nonpersistent emergent plants (nonpersistent-emergent wetlands), or submersed and (or) floating plants (aquatic beds), or both. Riverine ...... Wetlands within a channel. Vegetation, when pres- ent, is same as in the Lacustrine System.

Most Minnesota wetlands are categorized as palustrine because they have vegetation that remains standing all year. Most of these wetlands have an organic soil and are thus peatlands. A simplified definition of organic soil is one with an upper layer of partly de­ Figure 1. Sioux Nation Fen. This type of wetland, composed plant material (peat) at least 12 inches (Wright and oth­ a patterned calcareous fen, is rare in Minnesota. ers, 1992) to 16 inches (Cowardin and others, 1979) thick. Peat lands (Photograph by James E. Almendinger, U.S. Geo­ cover about 6 million acres in Minnesota (Minnesota Department logical Survey.) 238 National Water Summary-Wetland Resources: STATE SUMMARIES

VEGETATION ZONES

A . Conifer-hardwood forest zone

B. Deciduous forest woodland zone C. Prairie zone C C PHYSIOGRAPHY

A. Flat terrain (glacial-lake plains and outwash plains)

B. Rolling to hilly terrain (mostly glacial-till plains and end moraines)

C. Dissected terrain (areas not covered by most recent glacial advance) C

. I\.. .. .f I .=r

(\

A

WETLAN DS AND DEEPWATER HABITATS Distribution of wetlands and deepwater habitats- This map shows the approximate distribution of large wetlands in the State. Because of limitations of scale and source material, some wetlands are not shown

• Predominantly wetland

Predominantly deepwater habitat ,. •. .. ,. . . . .· . ~ Area typified by a high density of small wetlands .·· .·t ... . -... \ .:.~. I ~ .·. ~ ~ :· C - ,., · . L • .: . ' , ,. } .~"-'"\. 0 25 50 MILES J..: \,: • .? ·• j ~ -(,,I 0 25 50 KILOMETERS 1_·~ ·-~~ ""\. t; t - ~~_L __ ......

Figure 2. Wetland distribution and related biotic and physical features in Minnesota. A, Distribution of wetlands and deepwater habitats. 8, Vegetation zones. C, Physiography. (Sources: A, TE. Dahl, U.S. Fish and Wildlife Service, unpub. data, 1991. 8, Minnesota Department of Natural Resources, 1993. C, Adapted from Wright, 1972.) National Water Summary-Wetland Resources: MINNESOTA 239 to grow, or where fire has removed the black spruce (Glaser, 1992: HYDROLOGIC SETTING Minnesota Department of Natural Resources, 1993). Palustrine wetlands on mineral soil are present statewide. In The hydrology of wetlands is determined by climate, vegeta­ the western and southern parts of Minnesota, these wetlands com­ tion, physiography, and geology. Climate determines the net mois­ monly are called prairie potholes. These shallow depressions may ture supply, which is the difference between input of have open water near the center surrounded by emergent or and loss by evaporation and plant transpiration. Physiography and (persistent emergent wetland) in which broad-leaved geology influences not only the movement of water on and below sedges, grasses, and bulrushes predominate. In the eastern and the land surface but also the dissolved mineral content of the water. northern parts of Minnesota, palustrine wetlands on mineral soil Differences in climate across Minnesota cause differences in commonly are (forested or scrub-shrub wetlands) in which vegetation and moisture supply. Average annual temperature, which either hardwood or conifer trees or shrubs predominate (Minnesota influences evaporation and transpiration, ranges from about 36 °F Department of Natural Resources, 1993). (degrees Fahrenheit) in the north to about 46 °Fin the south (Baker Lacustrine and riverine wetlands commonly have beds of non­ and Strub, 1965). Average annual precipitation ranges from about persistent-emergent, submersed, or floating aquatic plants. Most of 20 inches in the west to about 30 inches in the east (Baker and oth­ the 3 million acres of Minnesota lakes are in the central and north­ ers, 1967). These climatic gradients contribute to a diagonal zona­ eastern parts of the State. Probably the best known lacustrine wet­ tion of major vegetation types and effective moisture, from the lands are wild rice beds (nonpersistent-emergent wetlands), which warm, dry prairie zone in the south and west to the cool, moist occupy about 150,000 to 200,000 acres of shallow lakes (John conifer-hardwood forest zone in the northeast (fig. 28). Peatlands Persell, Minnesota Chippewa Tribe, written commun., 1993). are more common in the conifer-hardwood forest zone than else­ where in Minnesota, because the relatively cool and wet conditions help preserve the peat. A Seasonal and year-to-year changes in climate cause changes in the moisture supply. Some prairie potholes receive different amounts UPGRAOtENT OOWNGRAOtENT of snowmelt runoff and ground-water inputs from year to year and PALUSTRINE WETlAJIIO consequently change from shallow emergent to open-wa­ Area of Aree of ter persisting for several years (Eisenlohr and others, 1972; ground-water diec:harge ground-water recharge LaBaugh and others, 1987). hinders peal accumulation because drying allows rapid microbial decomposition of the peat and makes it susceptible to fire. Peatlands consequently tend to be more common in the northeastern part of the State, which usually escapes severe drought (Borchert and Yaeger, 1968). Physiography (fig. 2C ) influences surface-water drainage and, consequently, wetland type and distribution. The last glacial advance ---- Glacial drift did not cover the extreme southeastern and southwestern corners of the State. Wetlands are less common in these older areas because the naturally dissected terrain has few basins remaining. Most ter­ 500FEET rains in the State, however, were formed during the last glacial ad­ VERTICAL SCALE EXAGGERATEO vance. Glacial-till plains and end moraines are gently rolling to hilly terrains that cover much of the State. The low infiltration capacity B of the clayey soil of these terrains in west-central and southern Bluff Mi nnesota enhances overland runoff, which can collect in prairie potholes. The Alexandria Moraine area (fig. 2C) coincides with the PALUSTAINE WETLANOS statewide diagonal climate-vegetation ronation and forms the core ~lcareous Fen of a region with a high density of wetlands intermixed with uplands RIVERINE WETLANO (fig. 2A). Glacial-lake plains and outwash plains are relatively flat terrains where large peatlands can develop if the water table is high and the moisture supply is sufficiently large and constant. The lack of large peatlands on the western part of the Glacial Lake Agassiz area (fig. 2C) may be caused by the moisture supply being insuffi­ cient or variable. Geology affects ground-water flow and chemistry. Ground­ Bedrock water discharge occurs where ground water seeps out of an aquifer into the wetland; ground-water recharge occurs where water from 1000 FEET the wetland percolates into an aquifer (fig. 3/\.). Wetlands in the State

VERTICAL SCALE EXAGGERATEO commonly receive ground-water discharge, the amount and qual­ ity of which can affect the vegetation. Some prairie potholes are sites EXPLANA TtON of naturally focused ground-water recharge, where overland runoff from the surrounding upland basin collects in the pothole before -- Ground-water flow ~iftJ Bulrush percolating into the surficial aquifer (LaBaugh and others, 1987). ----- Water table tlt11Htl Grass The influence of hydrology, particularly ground-water hydrol­ Cattail NIAi Sedge ogy, on wetlands is demonstrated by two examples. The first example * is the Red Lake peatland in northwestern Minnesota. This peatland ~(/ Spike Rush is a complex of fens and bogs with distinctive shapes and internal Figure 3. Hydrologic interaction between wetlands and ground patterns related to slight differences in water chemistry and flow water. A, Conceptual ground-water discharge and recharge in a (Heinselman, 1963; Glaser and others, 1981; Glaser, 1992). Fens wetland. 8, Conceptual ground-water flow under a calcareous fen develop where upwelling ground water reaches the peatland surface in the Valley. and flows laterally through the upper layer of fibrous peat. A pat- 240 National Water Summary-Wetland Resources: STATE SUMMARIES

terned fen someti mes develops in which the vegetation structure the western boundary of the Red Lake peatland is apparently con­ forms alternating ridges and troughs oriented at right angles to the trolled by the climatic moisture supply, the peatland might be di­ direction of this slow surface flow. T he ridges and troughs may be minished by warmer and drier climates resulting from natural cli­ IO to 50 feet wide (Heinselman, 1963), with the ridges occupied by mate cycles or, hypothetically, human-induced global warming. Such low shrubs and the troughs by sedges or pools. The vast fens of the drier climates also could desiccate shallow prairie potholes, as in Red Lake peatland provide the regional setting atop which bogs can the past. develop. Bogs in the Red Lake peatland have formed on peat mounds raised above the influence of upwelling ground water (Siegel and CON SERVATION Glaser, 1987; Glaser, 1992; Siegel. 1992). The flow of ft:n water around the bogs can cause them to have a streamlined shape, Many government agencies and private organizations partici­ rounded on the upgradient margin and extended to a long tail on pate in in Minnesota. The most active agen­ the downgradient margin. cies and organizations and some of their activities are listed in table The second example of the influence of ground-water hydrol­ I. ogy on wetlands is calcareous fens (fig. 3B), which are rare in Min­ Federal wetland activities.-Developrnent activities in Min­ nesota. Calcareous fens typically have significant amounts of up­ nesota wetlands are regulated by several Federal statutory prohibi­ welling ground water rich in calcium carbonate and surface slopes tions and incentives that are intended to slow wetland losses. Some that drain excess water (Curtis. 1971; Eggers and Recd, 1987; of the more important of these are contained in the 1899 Rivers and Thompson and others, 1992). These wetlands can be found in the Harbors Act; the 1972 Clean Water Act and amendments; the 1985 Minnesota River Valley on terraces at the base of the bluffs that form Food Security Act: the 1990 Food, Agriculture, Conservation. and the valley wall. The high water table in the bluffs provides the nec­ essary hydraulic pressure to force ground water to upwell at the fen. The fens generally lie above flood stages of the Minnesota River Table 1. Selected w etland-related activities of government and slope toward the river, protecting against inundation from the agenc ies and private o rganizations in Minnesota, 1993 river and providing drainage of excess water from the fen. As much !Source: Class1f1cat1on of activities is generalized from information provided as 25 feet of peat can accumulate over the zone of upwelling ground by agencies and organizations. • . agency or organization participates in wetland-related activity; , agency or organization does not participate in water. Calcareous fens are sensitive not only to activities such as wetland-related activity. MAN, management; REG, re gulation; R&C, res­ ditching or filling but also to more subtle causes of degradation. For toration and creation; LAN. land acqui s1t1on; R&D, research and data col­ example, pumping nearby wells could lower the natural hydraulic lection: D&I, delineation and inventory! pressures under the fen and reduce the amount of upwelling ground water, and changing the land use in the ground-water recharge area upgradient from the fen could change both the quantity and quality Agency or organization of the water available to the fen. Calcareous fens demonstrate that FEDERAL simply protecting the area of the wetland itself is not enough to Department of Agriculture ensure that the wetland will remain undamaged. Consolidated Farm Service Agency ...... ·- • Forest Service ...... • • • • • Natural Resources Conservation Service ...... • • • TRENDS Department of Commerce National Oceanic and Atmospheric Most changes in Minnesota wetlands during the last 150 years Administration ...... • have been caused by human activities. Estimates of wetland acre­ Department of Defense ages before settlement of the area by Europeans in the mid-l 800's Army Corps of Engineers ...... • • • • • Department of the Interior range from about 15 to 18 million acres; as much as one-half (by Fish and Wildlife Service ...... • • • • • area) of Minnesota's original wetlands might have been lost since Geological Survey ...... • presettlement times (Anderson and Craig, 1984; Tiner. 1984; Dahl, National Biological Service ...... • 1990). Most of the wetland loss has been the result of drainage for National Park Service ...... • • • • agriculture. By the early l 980's, more than 70 percent of Minnesota's Environmental Protection Agency ...... • • STATE originally poorly drained mineral soils in the prairie zone had been Board of Water and Soil Resources ...... • • • drained (Anderson and Craig. 1984). The loss of wetlands in the Department of Military Affairs ...... • • • • • largely agricultural basin of the Minnesota River may cause in­ Department of Natural Resources creased flushing of water, nutrients, and soil from the uplands into Division of Fish and Wildlife...... • • • • • the river ecosystem. The northern peatlands also have been affected Division of Forestry ...... • • • by human activities. During the early 1900's, several northern coun­ Division of Minerals ...... • • • • • Division of Waters ...... • • • ties went bankrupt as a result of funding the ditching of peatlands Office of Planning ...... • on the Glacial Lake Agassiz plain. Because of the flat landscape, Department of Transportation ...... • • • • • • lhe ditches were largely ineffective in draining the peatlands; how­ Environmental Quality Board ...... • ever, ditching might have altered peatland vegetation hundreds of Pollution Control Agency ...... • • University of Minnesota ...... • feet from the ditches (Glaser and others, 1981; Bradof, 1992). Small COUNTY AND LOCAL areas of peatland have been mined for horticultural purposes, logged Counties and cities ...... • • • • • for black spruce, or cultivated for specialty crops. The use of peat Soil and water conservation districts ...... • • • as a fuel, however, has not been economical to date (Keirstead, Townships ...... • • 1992). Watershed districts ...... • • • • Wetlands are sensitive to climate change also. About 7,000 SOVEREIGN NATIONS Native American tribes ...... • • • • years ago the water table in parts of Minnesota was as much as 20 PRIVATE ORGANIZATIONS feet lower than at present, and many prairie potholes were probably ...... • • • dry (Digerfeldt and others. 1992). The climate then became increas­ Izaak Walton League ...... • ingly moist, and by 4,500 years ago peat began to form in the rem­ National Audubon Society ...... • • • • nant Glacial Lake Agassiz plain (Glaser and others, 1981). Because The Nature Conservancy ...... • • • • • National Water Summary-Wetland Resources: MINNESOTA 241

Trade Act; the 1986 Emergency Wetlands Resources Act; and the manem easements to some privately owned wetlands and for pub­ 1972 Coastal Zone Management Act. lic education. The law promotes wetland preservation by allowing Section 10 of the Rivers and Harbors Act gives the U.S. Army tax-exempt status for wetlands of high value. The law essentially Corps of Engineers (Corp!>) authority to regulate certain activities fi lls the gap in wetland protection between larger, deepwater habi­ in navigable waters. Regulated activities include diking, deepening, tats, which are already protected by Minnesota statute, and agri­ fi lli ng, excavating, and placing of structures. The related section 404 cultural wetlands that are already covered by the Federal "Swamp­ of the Clean Water Act is the most often-used Federal legislation buster" provisions. The Board of Water and Soil Resources is the protecting wetlands. Under section 404 provisions, the Corps issues State agency responsible for promulgating rules to determine wet­ permits regulating the discharge of dredged or fill material into wet­ land value and to mitigate wetland losses, and local governmental lands. Permits are subject to review and possible veto by the U.S. units are respon~ible for carrying out the rules (table 1). Also in­ Environmental Protection Agency (EPA), and the FWS has review and cluded in the legislation are provisions to prohibit degradation of advisory roles. Section 40 I of the Clean Water Act grants to States calcareous fens and to protect about 150,000 acres of ecologicall y and eligible Indian Tribes the authority to approve, apply conditions significant peatlands. to, or deny section 404 permit applications on the basis of a pro­ The Department of Natural Resources has a variety of respon­ posed activity's probable effects on the water quality of a wetland. sibilities concerning wetlands and administers about 5.3 million Most farming, ranching, and silviculture activities are not sub­ acres of State land, almost one-half of which may be wetlands, in ject to section 404 regulation. However, the "Swampbuster" provi­ addition to about 3 million acres of lakes. The Department's Divi­ sion of the 1985 Food Security Act and amendments in the 1990 sion of Waters oversees permit applications for nearly all activities Food, Agriculture, Conservation, and Trade Act discourage (through below the ordinary high-water level in the "protected waters and financial disincentives) the draining, fi lling, or other alteration of wetlands" of the State, which include virtually all water bodies that wetlands for agricultural use. The law allows exemptions from pen­ have open water or nonwoody vegetation, are deeper than about 6 alties in some cases, especially if the farmer agrees to restore the inches, and are larger tllan 10 acres (2.5 acres in incorporated areas). altered wetland or other wetlands that have been converted to agri­ The Department's Division of Fish an

U.S. Geological Survey Water-Supply Paper 2425