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GREIFSWALD MEETING 1998

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Classification of Wetlands and Deepwater Habitats of the United States⁽¹⁾

Proposed on 26 March, 1998, to the IMCG Greifswald Workshop

by

Ronald Hofstetter

Department of Biology

University of Miami, Coral Gables, FL USA

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(1) Cowardin, L.M., Carter, V., Golet, F.C., & LaRoe, E.T. 1979. Classification of Wetlands and Deepwater Habitats of the United States. U.S. Gov't. Printing Office, Washington, D.C. 103 pp. [Note: This classification system is for both WETLANDS and DEEPWATER HABITATS]

«Deepwater habitats are permanently flooded lands lying below the deepwater boundary [2 m water depth] of wetlands.»

p.3

This system has been adopted by the National Resource Inventory and the National Wetland Inventory. The Wetlands Subcommittee of the Federal Geographic Data Committee in 1995 proposed the establishment of the «Cowardin Classification System» (Cowardin, et al., 1979) as the Wetlands Standard for the Federal Geographic Data Committee.

Following is an overview of that part of the Cowardin, et al., 1979, system for classifying wetlands:

«to impose boundaries on natural ecosystems for the purpose of inventory, evaluation, and management».

Cowardin, et al. 1979, p. 3

1 «to describe ecological units that have certain homogeneous natural attributes»;

2 «to arrange these units in a system that will aid decisions about resource management»;

3 «to furnish units for inventory and mapping»; and

4 «to provide uniformity in concepts and terminology throughout the United States.»

Cowardin, et al. 1979, p. 2

«Wetlands must have one or more of the following three attributes»:

1. «at least periodically, the land supports predominantly hydrophytes»,

2. «the substrate is predominantly undrained hydric soil», and

3. «the substrate is nonsoil and is saturated with water or covered by shallow water at some time during the growing season of each year».

Cowardin, et al. 1979, p. 3

«Wetlands are lands transitional between terrestrial and aquatic systems where the water table is usually at or near the surface or the land is covered by shallow water.»

Cowardin, et al. 1979, p. 3

The definition of «jurisdictional wetland» of the U.S. Environmental Protection Agency, U.S. Department of Agriculture and U.S. Army Corps of Engineers requires all three attributes:

1. hydrophytic vegetation (under normal conditions)

2. hydric soils, and

3. wetland hydrology.

«There is no single, correct, indisputable, ecological sound definition for wetlands, primarily because of the diversity of wetlands and because the demarcation between dry and wet environments lies along a continuum.»

Cowardin, et al. 1979, p. 3

• «boundary between land with predominantly hydrophytic cover and land with pre-dominantly mesophytic or xerophytic cover»,

• «boundary between soil that is predominantly hydric and soil that is predominantly nonhydric»,

«boundary between land that is flooded or saturated at some time each year and land that is not».

Cowardin, et al. 1979, p. 3

• «depth of 2 m. below low water» or

• «deep-water edge [of emergents, shrubs, or trees] beyond this [2 m.] depth at any time» for fresh-water habitats;

«elevation of extreme low water of spring tide» for marine and estuarine habitats.

Cowardin, et al. 1979, p. 4

Hierarchical, Divisive:

• System (5 Total, 5 Wetland)
• Subsystem (10 Total, 8 Wetland)
• Class (11 Wetland) + Modifiers
• Subclass
• Dominance Type

Each «System» contains those «habitats that share the influence of similar hydrologic, geo-morphologic, chemical, or biological factors».

• Marine (M)
• Estuarine (E)
• Riverine (R)
• Lacustrine (L)
• Palustrine (P)

Cowardin, et al. 1979, p. 4

«Water regimes are determined primarily by the ebb and flow of oceanic tides. Salinities exceed 30 o/oo with little or no dilution except outside the mouths of estuaries».

Cowardin, et al. 1979, p. 4

• «the landward limit of tidal inundation, including the splash zone from breaking waves»,
• «the seaward limit of wetland emergents, trees, or shrubs»; or
• «the seaward limit of the Estuarine System, where this limit is determined by factors other than vegetation».

Cowardin, et al. 1979, p. 4

«{Deepwater tidal habitats and adjacent} tidal wetlands that are usually semienclosed by land but have open, partly obstructed, or sporadic access to open ocean, and in which ocean water is at least occasionally diluted by freshwater runoff from the land».

Cowardin, et al. 1979, p. 4, 8

• «upstream and landward to where ocean-derived salts measure less than 0.5 o/oo during the period of average annual low flow»,
• «to an imaginary line closing the mouth of a river, bay, or sound»;
• «to the seaward limit of wetland emergents, shrubs, or trees where they are not included [above]».

Cowardin, et al. 1979, p. 4, 8

• «All wetlands {and deepwater habitats} contained within a channel, 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 o/oo».

Cowardin, et al. 1979, p. 9-10

• «bounded on the landward side by upland, by the channel bank (including natural and man-made levees)»,
• outer edge of «wetland dominated by trees, shrubs, persistent emergents, emergent mosses, or lichens»,
• at upstream edge where «tributary streams originate, or where the channel leaves a lake», but includes springs discharging into a channel.

Cowardin, et al. 1979, p. 9-10

«Wetlands with all of 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 % areal coverage; and
• (3) total area exceeds 8 ha.»

Cowardin, et al. 1979, p. 11-12

• «uplands or by wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens», and
• where «the extension of the Lacustrine shoreline forms the Riverine-Lacustrine boundary».

Cowardin, et al. 1979, p. 11-12

«all non-tidal wetlands dominated by trees, shrubs, persistent emergents, emergent mosses or lichens, and all such wetlands that occur in tidal areas where salinity due to ocean-derived salts is below 0.5 o/oo», and wetlands lacking vegetation, but having all of the following characteristics:

• (1) area less than 8 ha,
• (2) active wave-formed or bedrock shoreline features lacking,
• (3) water depth in the deepest part of basin less than 2 m at low water, and
• (4) salinity due to ocean-derived salts less than 0.5 o/oo.

bounded by upland and/or by any of the other four Systems.

Cowardin, et al. 1979, p. 12

CLASS «describes the general appearance of the habitat in terms of either the dominant life form of the vegetation or the physiography and composition of the substrate -- features that can be recognized without the aid of detailed environmental measurements.»

Cowardin, et al. 1979, p. 12-13

1. Life Forms - «because they are relatively easy to distinguish, do not change distribution rapidly, and have traditionally been used as criteria for classification of wetlands».

&endash; «not require extensive biological knowledge to distinguish between various life forms» and

«life forms are easily recognizable on a great variety of remote sensing products».

Cowardin, et al. 1979, p. 13

2. Vegetation Cover - «30% Rule»:

If vegetation covers 30% or more of the substrate, Classes are distinguished on the basis of the life form of the plants that constitute the uppermost layer of vegetation that has a minimal areal coverage of 30%

Cowardin, et al. 1979, p. 13

Subsystems: 1. Subtidal, 2. Intertidal.

&endash; Classes of both Subsystems:

• »Aquatic Bed (AB)
• » Reef (RF)
• » Rocky Shore (RS)
• » Unconsolidated Shore (US)

Cowardin, et al. 1979, p. 5

Subsystems: 1. Subtidal, 2. Intertidal.

&endash; Classes in Intertidal Subsystem:

• » Aquatic Bed (AB)
• » Reef (RF)
• » Stream Bed (SB)
• » Rocky Shore (RS)
• » Unconsolidated Shore (US)
• » Emergent Wetland (EM)
• » Scrub-Shrub Wetland (SS)
• »Forested Wetland (FO)

p. 5

Subsystems: 1. Tidal, 2. Lower Perennial, 3. Upper Perennial, 4. Intermittent, 5. Unknown Perennial.

Classes of Subsystems with wetlands:

• » Rock Bottom (RB)
• »Unconsolidated Bottom (UB)
• » Aquatic Bed (AB)
• » Rocky Shore (RS)
• » Unconsolidated Shore (US)
• » Emergent Wetland * (EM)

p. 5

Subsystems: 1. Limnetic, 2. Littoral.

Classes of the Littoral Subsystem:

• »Rocky Bottom (RB)
• » Unconsolidated Bottom (UB)
• » Aquatic Bed (AB)
• » Rocky Shore (RS)
• » Unconsolidated Shore (US)
• » Emergent Wetland * (EM)

Cowardin, et al. 1979, p. 5

Subsystems: none.

Classes:

• » Forested Wetland (FO)
• » Scrub-Shrub Wetland (SS)
• » Emergent Wetland (EM)
• » Moss-Lichen Wetland (ML)
• »Aquatic Bed (AB)
• » Rock Bottom (RB)
• » Unconsolidated Bottom (UB)

p. 5

Subclasses are based on «finer differences [than in Class] in life forms» and «are named on the basis of the predominant life form».

[e.g., Broad-leaved Deciduous (1), Narrow-leaved Deciduous (2), Broad-leaved Evergreen (3), Narrow-leaved Evergreen (4), Dead (5), Deciduous (6), Evergreen (7)]

Cowardin, et al. 1979, p. 14

Water Regime Modifiers:

Tidal: Subtidal (L), Irregularly Exposed (M), Regularly Flooded (N), Irregularly Flooded (P), Seasonally Flooded (R), Unknown (U). Nontidal: H. Permanently Flooded (H), Intermittently Exposed (G), Semipermanently Flooded (F), Saturated (B), Temporarily Flooded (A), Inter-mittently Flooded (J), Artificially Flooded (K), Unknown (U).

Cowardin, et al. 1979, p. 23-24

Water Chemistry Modifiers:

• &endash; Coastal Halinity: Hyperhaline (1), Euhaline (2), Mixohaline (3), Polyhaline (4), Mesohaline (5), Fresh (0)
• &endash; Inland Salinity: Hypersaline (7), Eusaline (8), Mixosaline (9), Fresh (0)
• &endash; pH: Acid (a), Circumneutral (t), Alkaline (l)

Cowardin, et al. 1979, p. 24

Soil Modifiers:

• &endash; Mineral (n)
• &endash; Organic (g)

Cowardin, et al. 1979, p. 25

Special Modifiers [man-made or -modified]:

• &endash;Excavated (x)
• &endash; Impounded/Diked (h)
• &endash; Partly Drained/Ditched (d)
• &endash; Farmed (f)
• &endash; Artificial (r)
• &endash; Beaver (b)
• Spoil (s)

Cowardin, et al. 1979, p. 25-26

«Some Modifiers are an integral part of this system and their use is essential; others are used only for detailed applications or for special purposes»;

• «Modifiers are never used with Systems or Subsystems»;

«However, at least one Water Regime Modifier, one Water Chemistry Modifier, and one Soil Modifier must be used at the Class level and at all lower levels».

Cowardin, et al. 1979, p. 29

No classification system can be universal and perfect to every user. The following comments reflect my personal views about the suitability of the classification system of Cowardin, et al., 1979, to the classification of global mires for conservation purposes.

Advantages of this system:

• · many similarities to the Ramsar wetland classification system,
• · convenient groupings by physiognomic similarity,
• · every community can be identified and coded,
• · widely applicable to broad range of community types,
• · adaptable to include new community types,
• · produces a manageable number of mappable entities,
• · avoids problems of existing wetland terms by not involving these terms,
• · little expertise or experience needed for classification at least to class.

Disadvantages of this system:

• · classifies wetland communities, not wetlands (although community codes could be chained together to reflect the entire wetland);
• · information (e.g., salinity), other than simple visual, is necessary to separate communities at the System level (the highest level);
• · natural, seasonal or year-to-year changes (e.g., in salinity) can cause changes in classification at the highest level, the System level;
• · there is a non-intuitive lack of parallel structure, e.g., permanent emergent vegetation occurs only in Palustrine & Estuarine, not in Lacustrine or Riverine;
• · differentiates only at the lowest level between communities whose genesis and character are very different (e.g., forested [ombrogenous] bog and cedar [geogenous] swamp);
• · cumbersome - communities described by codes in which characters are not always intuitive; codes not suitable for verbal communication;
• · little information provided about critical controlling factors (e.g., hydrology, soil types, topography);
• · places much emphasis on vegetation, but does not use terminology in describing plant assemblages common in Europe and other parts of the world;
• · identification at the Class level requires information (e.g., leaf persistence) that may not be available at one site visit;
• · no guidance on how to use taxa in the field (later provided by the National Wetland Inventory & the COE 1987 Wetland Delineation Manual - obligate & facultative taxa); much effort would be needed to identify additional species for global application;
• · depends on the estimate of «cover», a very subjective parameter;
• · at the highest levels of the system, general geographic location is more important than patterns of genesis and sets of controlling factors;
• · necessary list of consistent hydric soil characteristics is lacking (such a list would have to be expanded to address global conditions);
• · provides little information on soil conditions (sediment/sedentate type and depth, degree of decomposition, etc.);
• · water regime modifiers are poorly defined;
• · does not now provide the degree of distinction among wetland types that many European mire conservationists desire.

I conclude that - while the wetland classification system of Cowardin, et al., 1979, has some significant advantages - it can not be easily adapted to provide the details and distinctions desired by the many of the IMCG members for purposes of classifying global mires for conservation.