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University of Minnesota Extension

Preserving wetlands

Quick facts

  • Wetlands are identified by vegetation, soil and hydrology.
  • There are many regulations that govern wetlands.
  • Many creatures depend on wetland fringes that border lakes and streams for nesting and food.

  • Wetlands provide flood control, reduce flood damage and improve water quality by filtering nutrients and pollutants.

  • Wetlands recharge and discharge ground water.

Why wetlands are important

Wetlands have many important roles, some very obvious, others less so. Many creatures, such as amphibians and migratory birds, depend on wetland fringes that border lakes and streams for nesting and food.

A not-so-obvious benefit of wetlands is flood control. Wetlands hold storm water and release it gradually, reducing flood damage and improving water quality by filtering nutrients and some pollutants. Wetlands also have aesthetic benefits and recharge and discharge ground water.

What is a wetland?

The term "wetland" is used to describe a wide variety of wet environments found in Minnesota. A wetland can range from a slight depression that holds water only after spring runoff to a forested swamp with saturated peat soils.

Most people probably would describe a wetland as a small body of open water with cattails on the fringe. Lakes and streams are generally not wetlands, but may be bordered by wetlands. How then do we know what is and what is not a wetland?

Wetland areas are identified on site using vegetation, soils and hydrology. The hardest part of defining a wetland is locating the boundary between the wetland and upland. This is called wetland delineation. When any of the above three criteria are no longer present, legally, you are out of a wetland and into the upland area.

How to identify wetlands

Since there are many laws today protecting wetlands, it's important to identify wetlands and define their boundaries. There are some clues that are helpful in determining wetland or non-wetland areas. 

Water usually determines soil color and influences the vegetation found on a site. Therefore, vegetation, soils and hydrologic (water) factors must all be present in legal identification of a wetland. In undisturbed sites, vegetation is the most easily identifiable criterion and can be useful in wetland observations. Soils and hydrologic factors are more complex.

1. Vegetation

Wetland areas are usually dominated by vegetation that competes well or survives in wet conditions. In fact, some plants are almost always found in wetlands! These "obligate" wetland plants are good indicators of the existence of a wetland.

If you see the following obligate wetland plants, you are looking at a wetland:

  • Bog rosemary
  • Swamp milkweed
  • Bog birch
  • Sundew
  • Cotton-grass
  • Sand bar willow
  • Black willow
  • Skunk-cabbage
  • Labrador tea
  • Sphagnum moss
  • Bulrush
  • Wild rice
  • Cattail

The following plants are usually found in wet areas and are fairly good indicators of the presence of a wetland. If any of these are found in the area of interest, investigate further to determine if it's a wetland:

  • Red-osier dogwood
  • Black spruce
  • Larch (tamarack)
  • Speckled alder
  • Northern white cedar
  • Black ash

2. Soils

Soil development is also affected by water. In Minnesota, two major soil types develop in wet conditions. One is organic soils, or peat. The second is mineral soils that don't drain well because of low land, ground water seepage or a slowly permeable soil layer (e.g., clay, bedrock, or hardpan). These are both called hydric soils.

Organic soils or peat

Organic soils develop in depressions and consist of plant remains that do not decompose because soil is saturated. Organic soils can range in thickness from 2 to 30 feet. Plant parts are often still visible in many organic (peat) soils.

Mineral soils

Mineral soils that are saturated much of the time become dull-colored or gleyed. Gleyed soils are neutral gray and occasionally greenish or bluish gray.

Mineral soils saturated for short periods develop spots or blotches of different colors. These spots are called mottles and can be a sign of hydric or wetland soils.

3. Hydrology

Hydrology is the third criterion used in describing a wetland. Hydrology refers to the presence or flow of water through the site. Some wetlands are relatively dry during drier times of the year (such as late summer). Often, aerial photographs, talking with neighbors and visual evidence are used to determine wetland hydrology.

Best management practices for wetlands

Avoid, minimize and replace are the watchwords for wetland protection.

  • Avoid wetlands whenever possible.
  • If you must disturb a wetland area, minimize disruption of the soil, vegetation and hydrology.
  • A final alternative when a wetland is lost is mitigation by replacing it elsewhere.

Even very small wetland areas can help protect water quality. Following simple practices such as these on your property can help maintain the integrity and effectiveness of wetlands:

  • Use docks or boardwalks to cross a wetland rather than filling.
  • Lay out access paths along high ground, even if it means a longer walk to the shore.
  • Preserve existing drainageways and never divert water to or from wetland areas.

Wetland replacement

If avoidance is not possible, replacement of an impacted wetland area or paying into a "wetland bank" are two alternatives. Both replacement and banking programs are coordinated with your local governmental unit (LGU).

Replacing an impacted wetland area with a wetland elsewhere on the landscape is ordinarily accomplished by:

  • Restoring a wetland that was previously drained. Plugging an existing tile or building a dike is usually required to restore a wetland.
  • Created wetlands are also generally acceptable for wetland replacement. Created wetlands can be achieved by shaping abandoned gravel pits or excavating upland areas.

Wetland banking

Wetland banking allows someone proposing a project to buy credits from a "bank" of wetlands that have been restored or created elsewhere. The bank of wetlands must first be established so that credit will be available for withdrawal. Payment for wetland bank credit acres will depend on many factors, including the cost of land in your area and the cost of creating or restoring wetlands.

Regulation of wetlands

Due to the loss of many wetlands, the Federal government and Minnesota have established regulations to protect remaining wetlands. Some local governments also regulate wetlands. Since wetlands themselves are so very complex, it follows that the laws protecting them are also complex.


Reviewed in 2018

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