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Guidance Document Summary
| U.S. Fish and Wildlife Service’s Wetland Classification System |
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Cowardin, L.M., V. Carter, F.C. Golet, and E.T. LaRoe. 1979. Classification of wetlands and deepwater habitats of the United States. FWS/OBS-79/31. U.S. Fish and Wildlife Service, Office of Biological Services, Washington, D.C.
Click here to access the reference online |
| Classification system |
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This classification (Cowardin et al. 1979) is used for the National Wetland Inventory (NWI) database. Another classification, “Wetland Landscape Position, Landform, Water Flow Path, and Waterbody Type Descriptors (LLWW)” (Tiner 2003a), was developed to enhance the NWI database by adding descriptors for use in watershed-based wetland characterizations and preliminary assessment of wetland functions. There is some overlap with these classifications; however, LLWW may be used with or without referring to Cowardin et al.
Several methods use this classifcation including “Casco Bay Watershed Wetlands Characterization Method” (Hertz and Sartoris 2001), "Habitat Evaluation Procedure" (USFWS 1980), "Remotely-Sensed Indicators for Monitoring Condition of Natural Habitat in Watersheds" (Tiner 2004), and "Wetland Evaluation Technique - WET" (Adamus et al. 1987), and "Watershed-Based Preliminary Assessment of Wetland Functions - W-PAWF" (Tiner 2003b). |
John Cooper
Fish and Wildlife Service
Chief, Branch of Habitat Assessment
4401 North Fairfax Drive
Room 400
Arlington, VA 22203
Phone: 703-358-2161
Email: wetlands@fws.gov
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| Ralph Tiner and Candy Bartoldus (01/21/05) |
| Ralph Tiner (02/11/05) |
| Document Content (brief statements used as search criteria) |
| Description of one classification scheme (e.g., Cowardin et al. 1979) |
| Not applicable |
| Not applicable |
The U.S. Fish and Wildlife Service’s (FWS) Wetland Classification System was developed for use in conducting an inventory of the Nation’s wetlands and deepwater habitats. It describes and arranges ecological taxa in a system useful to resource managers and provides standard units (and terminology) for mapping. This system has been widely used since its publication, especially for producing NWI maps and digital geospatial data, reporting on the results of various inventories (e.g., Tiner 1985, 1989; Tiner and Burke 1995), wetland status and trends in the United States (e.g., Frayer et al. 1983, Dahl 2000), and individual states and localities (see examples in Tiner 1999, 2002, 2004). The classification system was adopted as the Federal standard for reporting on wetland status and trends by the Federal Geographic Data Committee. It can be used for on-the-ground classification and for inventories based on remote sensing.
The FWS classification system follows a hierarchical approach progressing from Systems and Subsystems at the general levels, to Classes, Subclasses, and Dominance Types. The System is described as “a complex of wetlands and deepwater habitat that share the influence of similar hydrologic, geomorphologic, chemical, or biological factors.” Five Systems are represented (see below). Each System is subdivided into Subsystems based on duration of flooding or water depth (see definitions in key words), except the Palustrine System which has no Subsystems.
Systems:
Marine
Estuarine
Lacustrine
Riverine
Palustrine
Subsystems:
Subtidal (Marine and Estuarine systems)
Intertidal (Marine and Estuarine systems)
Tidal (Riverine systems)
Lower Perennial (Riverine systems)
Upper perennial (Riverine systems)
Intermittent (Riverine systems)
Limnetic (Lacustrine systems)
Littoral (Lacustrine systems)
The Class is the highest taxonomic unit below Subsystem, followed by Subclass, and Dominance Types. The Class describes the general appearance of the habitat in terms of the dominant vegetative life form (e.g., trees, shrubs, emergents) or the predominant substrate where less than 30 percent vegetative cover is present. Subclasses are based on finer distinctions of the same (e.g., emergents can be described as persistent or non-persistent). Dominance Type is determined based on dominant plant or animal species (e.g., Spartina alterniflora is a common Dominance Type for an Estuarine Intertidal Persistent Emergent Wetland). Modifiers can be applied at the Class and lower levels to describe water regime (hydrology), water chemistry (pH and salinity), soil type (organic vs. mineral), and human influences (e.g., excavated, impounded, diked, partly drained, farmed, artificial). When there is a need to recognize regional differences, the Bailey's ecoregions and coastal biophysical regions (e.g., Acadian and Virginian) can also be used.
The classification system is open-ended, meaning that other descriptors can be added to the lower level of the system. For example, in mapping wetlands, the Service has added “Beaver” as a modifier to highlight wetlands modified by beaver activity.
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Estuarine:
deepwater tidal habitats and adjacent tidal wetlands that are usually semi-enclosed by land but have open, partially obstructed, or sporadic access to the ocean and in which ocean water is at least occasionally diluted by freshwater runoff from the land.
Intermittent:
the channel contains flowing water for only part of the year.
Intertidal:
the substrate alternately exposed and flooded by tides; includes the associated splash zone.
Lacustrine:
wetlands and deepwater habitats with all the following characteristics: (1) situated in a topographic depression or a dammed river channel; (2) lacking trees, shrubs, persistent emergents, emergent mosses or lichens with greater than 30 percent areal coverage; and (3) total area exceeds 8 ha (20 acres). Similar wetland and deepwater habitats totaling less than 8 ha are also included in the Lacustrine System if an active wave-formed or bedrock shoreline feature makes up all or part of the boundary, or if the water depth in the deepest part of the basin exceeds 2 m (6.6 feet) at low water.
Limnetic:
all deepwater habitats within the Lacustrine system; typically beyond a water depth of 2 m at mean low water.
Littoral:
all wetland habitats in the Lacustrine system. Extends from the shoreward boundary of the system to a depth of 2 m (6.6 feet) below low water or to the maximum extent of nonpersistent emergents, whichever is deeper.
Lower Perennial:
water flows downstream throughout the year; the gradient is low and water velocity is often slow and there is no tidal influence.
Marine:
open ocean overlying the continental shelf and its associated high-energy coastline.
Palustrine:
all nontidal wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens, and similar wetlands that occur in tidal areas where salinity due to ocean derived salts is below 0.5 parts per thousand. It also includes wetlands lacking such vegetation, but with all of the following four characteristics: (1) area less than 8 ha (20 acres); (2) active wave-formed or bedrock shoreline features lacking; (3) water depth in the deepest part of basin less then 2 m at low water; and (4) salinity due to ocean-derived salts less than 0.5 percent.
Riverine:
wetland and deepwater habitats contained within a channel of a river or stream, with two exceptions: (1) wetlands dominated by trees, shrubs, persistent emergents, emergent mosses, or lichens, and (2) habitats with water containing ocean-derived salts in excess of 0.5 parts per thousand.
Subtidal:
the substrate continuously submerged.
Tidal:
water flow is bi-directional at least seasonally due to tidal influence.
Upper perennial:
water flows downstream throughout the year; the gradient is high and velocity of the water fast and there is no tidal influence.
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| To provide classification of wetlands and deepwater habitats in the United States for use in inventory, mapping, and trends analyses (based on aerial photointerpretation). Also to provide uniformity in concepts and terminology for wetland classification across the country. This classification is based on vegetation, substrate, hydrology, and water chemistry. |
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This classification was developed for the purpose of conducting basic inventories of wetlands and deepwater habitats. Products include maps, digital data, reports on the results of wetland inventories, and wetland trends analyses (e.g., Dahl 2000). These can be obtained at the U.S. Fish and Wildlife National Wetlands Inventory website (http://wetlands.fws.gov/ ) or through Fish and Wildlife Service Regional Offices. Examples of inventory reports include state wetland inventory reports for New Jersey, Rhode Island, and Maryland (Tiner 1985, 1989, and Tiner and Burke 1995).
The maps/digital data form the basis for conducting both site specific and landscape-level assessment of wetland function. More detailed classification may be required when using the data for landscape-level assessment of wetland condition/function. Additional attributes can be added by applying the “Wetland Landscape Position, Landform, Water Flow Path, and Waterbody Type Descriptors” (LLWW) (Tiner 2003a). Examples of this additional classification are described in the method reviews of “Watershed-based Preliminary Assessment of Wetland Functions” (W-PAWF) (Tiner 2003b). |
| Sample Data Sheet Availability |
| Not available online. |
| Terrestrial | Riparian |
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| Not applicable | Not applicable | | Nontidal Wetland | Tidal Wetland |
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| Non-vegetated, Vegetated | Non-vegetated, Vegetated | | Nontidal Open Water | Tidal Open Water |
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| Intermittent & ephemeral streams, Non-wadeable rivers & streams, Standing water bodies (e.g., lakes, ponds & reservoirs), Urban drainages, Wadeable rivers & streams | Other tidal open water, Tidal rivers & streams | | Other Habitats |
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| Peatland, Reef, Seagrass beds, Submerged aquatic bed (non-tidal) |
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| No. This document is not designed to address several habitat types within a watershed context. |
| Wetlands and deepwater habitats of the United States. |
| Use of Classification for Describing Habitat Functions |
| Yes. |
| Yes, in its basic form, the classification provides a set of wetland types that can be correlated to habitat functions. The most specific correlations could probably be made when wetlands are classified to Dominance Type. Otherwise only general correlations can be made. When this classification is enhanced for landscape position, landform, water flow path, and waterbody type, a multitude of functions can be evaluated. General functions include: surface water detention, streamflow maintenance, coastal storm surge detention, nutrient transformation, sediment and other particulate retention, shoreline stabilization, fish/shellfish habitat, waterfowl/waterbird habitat, other wildlife habitat, and conservation of biodiversity. |
| Cowardin et al. provides a system to describe many types of wetlands that can yield useful information for general habitat assessments. If one classifies down to the most detailed level in the classification hierarchy - dominance type - specific plant communities are recognized that can easily be related to habitat for various fish and wildlife species. At lower levels such as system, class, subclass, and water regime, one can draw many correlations to these species also. For example, estuarine emergent wetlands regularly flooded are “low salt marshes” that are important for fish, nutrient export, shoreline stabilization, habitat for clapper rail (depending on geographic location), etc. Specific wetland types like Atlantic white cedar swamps, Phragmites marshes, ericaceous shrub bogs, larch (in the North) and bald cypress (in the South) that can be recognized on NWI maps by unique codes (e.g., PFO4Eg, E2EM5P or PEM5A, PSS3Ba, PFO2B, and PFO2F or PFO2E, respectively). These types of wetlands can then be correlated with known functions of these swamps. Moreover, in certain areas, the NWI codes can be related to other types such as PFO4E, PFO4/1C, PFO4/1A equate to Pitch Pine swamps (or mixtures with deciduous trees) in the NJ Pine Barrens and to Loblolly Pine swamps on the Delmarva Peninsula, as long as there are not multiple species possessing that life form that dominate wetlands. It is therefore more difficult to translate PFO1 codes to red maple swamps, since there are numerous other dominant broad-leaved deciduous trees inhabiting the swamps. |
| All regions of the United States. |
- Alaska (AK)
- Atlantic (Puerto Rico, Virgin Islands)
- Intermountain (AZ, CO, MT, NM, OK, TX, UT, WY)
- Midwest (AR, IA, IL, IN, KS, MI, MN, MO, ND, NE, OH, SD, WI)
- National Capital (DC, DE, MD, VA)
- Northeast (CT, MA, ME, NH, NJ, NY, PA, RI, VT, WV)
- Pacific (Hawaii, Guam, American Samoa)
- Pacific West (CA, ID, NV, OR, WA)
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| No modification or additional data collection needed |
| General Categories Addressed |
- Habitat (e.g., habitat suitability, biological integrity)
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Dahl, T. 2000. Status and trends of wetlands in the conterminous United States 1866 to 1997. U.S. Fish and Wildlife Service, U.S. Department of the Interior, Washington, D.C.
http://wetlands.fws.gov/
Frayer, W.E., T.J. Monahan, D.C. Bowden, and F.A. Graybill. 1983. Status and trends of wetlands and deepwater habitat in the conterminous United States, 1950s to 1970s. Department of Forest and Wood Sciences, Colorado State University, Fort Collins, CO.
Tiner, R.W. 1985. Wetlands of New Jersey. U.S. Fish and Wildlife Service, Newton Corner, MA.
Tiner, R.W. 1989. Wetlands of Rhode Island. U.S. Fish and Wildlife Service, Newton Corner, MA.
Tiner, R.W. 1999. Wetland indicators: A guide to wetland identification, delineation, classification, and mapping. Lewis Publishers, Boca Raton, FL.
Tiner, R.W. 2002. Enhancing wetlands inventory data for watershed-based wetland characterizations and preliminary assessment of wetland functions. Pages 17-39 in R.W. Tiner (compiler). Watershed-based wetland planning and evaluation. A collection of papers from the Wetland Millennium Event (August 6-12; Quebec City, Quebec, Canada). Distributed by the Association of State Wetland Managers, Inc., Berne, NY.
http://www.aswm.org/propub/pubs/pdf/tiner_2002_wshed.pdf
Tiner, R.W. 2003a. Dichotomous keys and mapping codes for wetland landscape position, landform, water flow path, and waterbody type descriptors. Northeast Region, U.S. Fish and Wildlife Service, Hadley, MA.
http://library.fws.gov/wetlands/dichotomouskeys0903.pdf
Tiner, R.W. 2004. Remotely sensed indicators for monitoring the general condition for "natural" habitat in watersheds. An application for Delaware's Nanticoke River watershed. Ecological Indicators 4: 227-243.
http://wetlands.fws.gov/Pubs_Reports/EcologicalIndicatorsTiner.pdf
Tiner, R.W. and D.G. Burke. 1995. Wetlands of Maryland. U.S. Fish and Wildlife Service, Hadley, MA and Maryland Dept. of Natural Resources, Annapolis, MD.
U.S. Fish and Wildlife (n.d.). National Wetlands Inventory. U.S. Fish and Wildlife website http://wetlands.fws.gov/
http://wetlands.fws.gov/
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| No additional comments. |
| Authors' comments not available. |
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This NBII site is maintained and hosted by the Center for Biological Informatics of the U.S. Geological Survey
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