Content adapted with permission from the Indiana Department of Natural Resources, a partner in the Natural Heritage of Indiana project. More Indiana WETlands information about can be found here.
What is a Wetland?
Swamps, marshes, bogs, fens, sloughs, and bottomlands - we have many names for wetlands, but what makes a wetland a wetland? A single, comprehensive, universally accepted definition does not exist which concisely and accurately defines all wetlands. Because wetlands have diverse mixes of vegetation, from tidal marshes on the Atlantic and Pacific Coasts to bottomland hardwood forests along the Patoka River, varying degrees of water, from cypress swamps in Posey County to wet prairie in Lake County, and exist in many parts of the landscape, such as isolated pothole wetlands in Steuben County to backwater wetlands along the Wabash River, one definition could not possibly fit all wetlands.
All wetlands do have some common traits, which help answer the question - what is a wetland. In general, wetlands are areas where water covers the soil, or is present either at or near the surface of the soil for part or all of the year, including the growing season for plants. Wetlands are in-between places, which lie between deep water in lakes and streams and dry land. Wetlands support an array of plants and animals which have adapted to life in saturated or flooded conditions. Wetlands have soils which differ from soils in dry areas, exhibiting characteristics that show the soil developed in saturated conditions. Wetlands can be identified by these basic indicators: vegetation, hydrology and soils. All three characteristics must be present during some portion of the growing season for an area to be a jurisdictional wetland - a wetland protected by the Clean Water Act.
For the purpose of regulation under the Clean Water Act, the U.S. Army Corps of Engineers (Corps) defines wetlands as:
Those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.
Listed below are descriptions of these indicators, which further explain the definition of wetlands.
In the United States, near 5,000 different plants may live in wetlands. These plants, known as hydrophytic vegetation, are listed in regional publications of the U.S. Fish and Wildlife Service. For example, cattails, bulrushes, sphagnum moss, bald cypress, willows, sedges, rushes, arrowheads and lily pads usually occur in wetlands. Plants which grow in wetlands also exhibit certain physical qualities, such as shallow root systems, swollen trunks, or roots found growing from the plant stem or trunk above the soil surface.
Approximately 2,000 named soils in the United States occur in wetlands. Such soils, called hydric soils, have characteristics that show they developed in conditions where the presence of water has limited soil oxygen for long periods during the growing season. If the Natural Resources Conservation Service (NRCS) has listed the soil in your area as hydric, the area might be a wetland. Hydric soil indicators include:
- Soil consists predominantly of decomposed plant material (peats or mucks).
- Soil has a thick layer of decomposing plant material on the surface.
- Soil has a bluish gray or gray color below the surface, or the major color of the soil at this depth is dark (brownish black or black) and dull.
- Soil has the odor of rotten eggs.
- Soil is sandy and has a layer of decomposing plant material at the soil surface.
- Soil is sandy and has dark stains or dark streaks of organic material in the upper layer below the soil surface.
Some wetlands are hard to recognize because they are dry during part of the year. Wetland hydrology refers to the presence of water at or above the soil surface for a sufficient period of the year to significantly influence the plant types and soils that occur in the area. Although the most reliable evidence of wetland hydrology may be provided by gauging station or groundwater well data, such information is limited for most areas and, when available, requires analysis by trained individuals. Thus, we observe most hydrologic indicators during field inspection. Most do not reveal either the frequency, timing, or duration of flooding or the soils saturation. However, the following indicators provide some evidence of the periodic presence of flooding or soil saturation:
- Standing or flowing water is observed on the area during the growing season.
- Soil is waterlogged during the growing season.
- Water marks are present on trees or other erect objects. Such marks show that water periodically covers the area to the depth shown on the objects.
- Drift lines, which are small piles of debris oriented in the direction of water movement through an area, are present. These often occur along contours and represent the approximate extent of flooding in an area.
- Thin layers of sediments are deposited on leaves or other objects.
Following content adapted with permission from IUPUI, a partner in the Natural Heritage of Indiana project. More information about IUPUI's Center for Earth and Environmental Science can be found here.
Importance of Wetlands, Wetland Loss, and Wetland Restoration
Wetlands are part of our natural heritage. They provide many vital physical, ecological, and economic functions and benefits. These benefits and functions can generally be classified as water resource related, biological and ecological, aesthetic, educational, recreational and economic. Wetlands are living museums, where the dynamics of ecological systems can be observed and taught. They are incredibly diverse habitats. About 900 species of vertebrate animals require wetlands at some time in their lives. Wetlands provide the principal habitat for virtually all species of waterfowl nationwide, and also for many other birds, mammals and reptiles. In Indiana, 11 species of waterfowl use wetlands for nesting and 28 species use wetlands as migration / wintering habitat. Nationwide, nearly 35 percent of all rare and endangered animal species depend on wetlands for survival, although wetlands constitute only 5 percent of the nation's land. More than 60 wetland-dependent animal species are listed as endangered, threatened, or of special concern in Indiana. A great variety of plants thrive in wetlands and many are wholly dependent on wetland habitats. Because so many wetlands have been lost or degraded, there are more than 120 species of wetland plants in Indiana that are endangered, threatened or rare. People additionally utilize wetlands for activities such as bird watching, hiking, and nature study. A 1996 survey by the U.S. Fish and Wildlife Service suggests that Indiana wetland habitats generate more than a million user days of nonconsumptive recreation each year.
Despite our recognition of the importance and value of wetlands, they are now relatively rare ecosystems in Indiana's landscape. Statewide analysis by the Natural Resources Conservation Service and Indiana Department of Natural Resources concluded there were approximately 5.6 million acres of wetlands in Indiana circa the 1780’s representing 24% of the state’s surface area. Surveys completed 100 years later during the 1980’s concluded that there are 813,000 wetland acres accounting for only 3.5% of the surface area of the state. These estimates indicate that Indiana has lost 85% of its wetlands and ranks 4th (tied with Missouri) among the 50 states in proportion of wetland acreage lost. The vast majority of the 85% of the wetlands lost was due to drainage for agricultural purposes. Wetland soils are nutrient rich and valued for growing agricultural crops.
Wetland restoration is the process of returning an impacted wetland to a more natural state. Wetlands in Indiana are many times restored by removing the subsurface agricultural tile drainage networks installed by earlier farmers. These networks move water from the wetland through the underground system to an outfall point, such as a creek or artificial ditch. In addition to restoring the natural water flow to a wetland, many times native wetland plants need to be re-established and the invasive exotic plant species need to be removed. The restoration of wetlands increases habitat diversity by providing the plants and structure native animals rely upon for survival and breeding. Wetlands additionally enhance water quality and curb flooding by acting as natural sponges that capture excess water and filter contaminants. As a result, wetland restorations improve the ecological function of creeks and rivers as they flow into larger water bodies such as reservoirs, lakes, and oceans.