Frequently Asked Questions

What kinds of wetlands exist?

"Wetlands" is a general term for a large variety of terrain types including freshwater marshes, bogs, fens, ponds, prairie potholes, swamp forests, shrub swamps, vernal pools, and wet meadows. The precise definitions can vary from one source to another; the following definitions are based primarily on those published by the United States Environmental Protection Agency's Office of Wetlands, Oceans, and Water, and supplemented by other sources.

Bogs

Bogs are characterized by spongy peat deposits, acidic waters, and a floor covered by a thick carpet of sphagnum moss. Precipitation is the primary—or even sole—source of water, resulting in scant nutrients for plant growth. Bogs usually form either when sphagnum moss fills a lake or pond or when sphagnum moss blankets dry land and prevents water from leaving the surface. A thick layer of acidic peat deposits builds up over time. Bogs serve an important ecological function in preventing downstream flooding by absorbing precipitation.

There are two subtypes of bogs—northern bogs and pocosins.

Northern bogs are generally associated with low temperatures and short growing seasons where ample precipitation and high humidity cause excessive moisture to accumulate. Northern bogs often form in old glacial lakes. They may have either considerable amounts of open water surrounded by floating vegetation or vegetation may have completely filled the lake (terrestrialization). The sphagnum peats of northern bogs cause especially acidic waters, so the ecosystem has very specialized and unique flora and fauna called acidophiles that can grow in these conditions. In addition to the characteristic sphagnum moss, bogs support a number of species such as cotton grass, cranberry, blueberry, pine, Labrador tea, and tamarack. Moose, deer, and lynx are a few of the animals that can be found in northern bogs. The greater sandhill crane, the sora rail, and the great gray owl depend on bogs for survival.

The word pocosin comes from the Algonquin Native American word for "swamp on a hill". Pocosins range in size from less than an acre to several thousand acres. Pocosins are found in broad, flat, upland areas far from large streams, and rain provides most of their water. There is normally no standing water, but a shallow water table leaves the nutrient-poor, acidic soil saturated for much of the year. The soil is a mixture of peat and sand containing large amounts of charcoal from periodic burnings. These natural fires occur because pocosins periodically become very dry in the spring or summer. The fires are ecologically important because they increase the diversity of shrub types in pocosins. The most common plants are evergreen trees (loblolly bay, red bay, and sweet bay), and evergreen shrubs (titi, fetterbush, and zenobia).

Habitat is the most valuable function of pocosins, sheltering plants and animals, including endangered species like the red-cockaded woodpecker. Some pocosins are very large and difficult to develop, so they remain largely undisturbed. As a result, they are a haven for species adapted to living in unaltered forests. The slow movement of water through the dense organic matter in pocosins removes excess nutrients deposited by rainwater. The same organic matter also acidifies the water. This very pure water is slowly released to estuaries, where it helps to maintain the proper salinity, nutrients, and acidity, which helps to maintain healthy fish populations.

Fens

Fens are peat-forming wetlands that receive nutrients from sources other than precipitation, such as groundwater movement and run-off. Fens differ from bogs because they are less acidic and have higher nutrient levels, thus supporting a more diverse plant and animal community. These systems are often covered by grasses, sedges, rushes, and wildflowers. Some fens are characterized by parallel ridges of vegetation separated by less productive hollows. The ridges of these patterned fens form perpendicular to the downslope direction of water movement. In some cases, peat may build up and separate the fen from its groundwater supply, changing the fen into a bog.

Fens are most frequently found in the northern hemisphere. They are generally associated with low temperatures and short growing seasons, where ample precipitation and high humidity cause excessive moisture to accumulate. Fens prevent or reduce the risk of floods, improve water quality, and provide habitat for unique plant and animal communities. Up to 10,000 years are required to form a fen naturally.

Marshes

Marshes are frequently or continually inundated with water and characterized by emergent soft-stemmed vegetation adapted to saturated soil conditions. There are many different kinds of marshes, ranging from the prairie potholes to the Everglades, coastal to inland, freshwater to saltwater. All types receive most of their water from surface water, but many marshes are also fed by groundwater. Nutrients are plentiful and the pH is usually neutral leading to an abundance of plant and animal life.

The U.S. Environmental Protection Agency frequently divides marshes into tidal and non-tidal categories.

Non-tidal marshes are the most prevalent and widely distributed wetlands in North America. They are mostly freshwater marshes, although some are brackish or alkaline. They frequently occur along streams in poorly drained depressions, and in the shallow water along the boundaries of lakes, ponds, and rivers. Water levels in these wetlands generally vary from a few inches to two or three feet, and some marshes, like prairie potholes, may periodically dry out completely. Non-tidal marshes mitigate flood damage and filter excess nutrients from surface runoff. Prairie potholes, playa lakes, vernal pools, and wet meadows are all examples of non-tidal marshes.

A non-tidal marsh can be recognized by its characteristic soils, vegetation, and wildlife. Highly organic, mineral rich soils of sand, silt, and clay underlie these wetlands. Due to their high levels of nutrients, freshwater marshes are one of the most productive ecosystems on earth, with a disproportionally large diversity of life. They sustain a vast array of plant communities that in turn support a wide variety of wildlife within this vital wetland ecosystem. Lily pads, cattails, reeds, and bulrushes provide excellent habitat for waterfowl and other small mammals, such as red-winged blackbirds, great blue herons, otters, and muskrats.

Tidal marshes can be found along protected coastlines in middle and high latitudes worldwide. Some are freshwater marshes, others are brackish (somewhat salty), and still others are saline (salty), but they are all influenced by the motion of ocean tides. Tidal marshes are normally categorized into two distinct zones, the lower or intertidal marsh and the upper or high marsh. In saline tidal marshes, the lower marsh is normally covered and exposed daily by the tide. It is predominantly covered by the tall form of smooth cordgrass (Spartina alterniflora). The saline marsh is covered by water only sporadically, and is characterized by short smooth cordgrass, spike grass, and black grass (Juncus gerardii). Saline marshes support a highly specialized set of life adapted for saline conditions. Brackish and freshwater tidal marshes are also associated with specific plants and animals, but they tend to have a greater variety of plant life than saline marshes.

Tidal marshes serve many important functions. They buffer stormy seas, slow shoreline erosion, and are able to absorb excess nutrients before they reach the oceans and estuaries. (High concentrations of nutrients can cause oxygen levels low enough to harm wildlife, such as the "Dead Zone" in the Gulf of Mexico.) Tidal marshes also provide vital food and habitat for clams, crabs, and juvenile fish, as well as offering shelter and nesting sites for several species of migratory waterfowl.

Swamps

A swamp is any wetland dominated by woody plants. Swamps are characterized by saturated soils during the growing season, and standing water during certain times of the year. Swamps serve vital roles in flood protection and nutrient removal. The highly organic soils of swamps form a thick, black, nutrient-rich environment for the growth of water-tolerant trees. Floodplain forests are especially high in productivity and species diversity because of the rich deposits of alluvial soil from floods. Plants, birds, fish, and invertebrates such as freshwater shrimp, crayfish, and clams require the habitats provided by swamps. Many rare species, such as the endangered American crocodile depend on these ecosystems as well. Many upland creatures depend on the abundance of food found in the lowland swamps, and valuable timber can be sustainably harvested to provide building materials for people.

Swamps may be divided into two major classes according to vegetation: shrub swamps and forested swamps. Forested swamps and shrub swamps are often found adjacent to one another.

Forested swamps (or swamp forests) are often inundated with floodwater from nearby rivers and streams. They are occasionally covered by very slowly moving or standing water. In very dry years they may represent the only shallow water for miles. Their presence is critical to the survival of wetland-dependent species like wood ducks (Aix sponsa), river otters (Lutra canadensis), and cottonmouth snakes (Agkistrodon piscivorus). Some of the common species of trees found in these wetlands are red maple (Acer rubrum) and pin oak (Quercus palustris) in the northern United States, overcup oak (Quercus lyrata) and cypress (Taxodium spp.) in the South, willows (Salix spp.) and western hemlock (Tsuga sp.) in the Northwest, Atlantic white cedar (Chamaecyparis thyoides), and tupelo (Nyssa aquatica). Bottomland hardwood swamp is a name commonly given to forested swamps along the sluggish rivers in the southeast and south central United States.

Shrub swamps are dominated by shrubby vegetation such as buttonbush, willow, dogwood (Cornus sp.), smooth alder, and swamp rose (Rosa palustris). The soil is often water-logged for much of the year, and covered at times by as much as a few feet of water because this type of swamp is found along slow moving streams and in floodplains. Mangrove swamps are a type of shrub swamp dominated by mangroves.

Our 70.11 acre (283,735 square meter) wetlands park is a forested swamp, but lacks sufficient large and dense trees to qualify for the "bottomland hardwood swamp" subset. Although most swamps are found in coastal regions and along inland rivers and streams, Restoration Park is an example of a swamp that forms in inland depressions.

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