Wetlands and Deepwater Habitats Findings

State of Oregon & National
1997 National Resources Inventory Results
(Revised December 2000)

See Wetlands Topic List for detailed results.

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Definitions and Background

The National Resources Inventory (NRI) uses an abbreviated version of the Cowardin et. al. (1979) wetland and deepwater habitat classification system. The Cowardin system has been officially adopted by the U.S. Fish and Wildlife Service (FWS), is recognized by the Federal Geographic Data Committee, and is widely used to develop wetland data bases. The system was developed by Lewis M. Cowardin of the U.S. Fish and Wildlife Service (FWS) and others.

The FWS also conducts a wetlands inventory program, the Wetlands Status and Trends study. At the present time, results from these two wetland inventory programs are not directly comparable. Differences in the programs include areas of coverage, sampling design, and statistical methodology. The NRI estimates are for water areas and non-federal lands only. FWS wetland estimates include water areas, non-federal lands, and federal lands.

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

Deepwater habitats are permanently flooded lands lying in deeper water than wetlands. All open water areas in which the mean water depth exceeds 6.6 feet in nontidal areas are included in deepwater habitat.

The five major systems within the Cowardin classification are Estuarine, Lacustrine, Marine, Palustrine, and Riverine. In general terms, these include:

Estuarine - Deepwater tidal habitats and adjacent tidal wetlands.

Lacustrine – Wetlands and deepwater habitats with open water exceeding 20 acres or more than 6.6 feet deep.

Marine – Open ocean and its associated high-energy coastline.

Palustrine – All nontidal wetlands dominated by trees, shrubs, and other persistent wetland plants. This system also includes water bodies less than 20 acres which are less than 6.6 feet in depth at low water.

Riverine - All open water wetland and deepwater habitats contained in a channel.

For references and a more detailed discussion of the Cowardin wetland and deepwater habitat classification system, see Wetland Definitions.

Oregon 1997 Wetland and Deepwater Habitat Estimates

The NRI results indicate that Palustrine wetlands were the most common type in 1997 on Oregon’s federal and non-federal water areas and non-federal lands, totaling nearly 1.4 million acres.

Oregon 1997 Wetland and Deepwater Habitat Estimates. For water areas and non-federal lands only.
Cowardin Type	Acres	Percent
Palustrine	1,390,900	59.6%
Lacustrine	557,600	23.9%
Estuarine Deepwater, Riverine, and Marine	359,400	15.4%
Estuarine Wetland	25,400	1.1%
Total Acres	2,333,300	100.0%

Chart for 1997 Acres by Cowardin System (11 KB)
Table for 1997 Acres by Cowardin System (7 KB)

Text Version of 1997 Acres by Cowardin System.

Details for 1997 Acres by Cowardin System.

Oregon 1997 Palustrine and Estuarine Wetland Estimates by Land Cover/Use

The NRI results indicate that more than half of Oregon’s Palustrine and Estuarine wetlands in 1997 occurred on cropland, pastureland, or Conservation Reserve Program (CRP) land. These wetland types are often the focus of wetland conservation activities.

Oregon 1997 Palustrine and Estuarine Wetland Estimates by Land Cover/Use
Land Cover/Use	Acres	Percent
Cropland, Pastureland, and CRP Land	772,300	54.5%
Rangeland	275,700	19.5%
Forestland	186,500	13.2%
Other Rural Land	161,900	11.4%
Water Areas	15,200	1.1%
Developed Land	4,700	0.3%
Total Acres	1,416,300	100.0%

Chart for 1997 Palustrine & Estuarine Wetlands by Land Cover/Use (14 KB)
Table for 1997 Palustrine & Estuarine Wetlands by Land Cover/Use (6 KB)

Text Version of 1997 Palustrine & Estuarine Wetlands by Land Cover/Use.

Details for 1997 Palustrine & Estuarine Wetlands by Land Cover/Use.

Palustrine and Estuarine Wetland Losses and Gains Between 1992 and 1997

Between 1992 and 1997, for Palustrine and Estuarine wetlands, there was an estimated gross loss of 506,000 acres and an estimated gross gain of 343,200 acres in the United States. The result of these fluctuations was a net loss of 162,800 acres of wetlands. This is an estimated annual rate of 32,560 acres of Palustrine and Estuarine wetlands lost per year during this 5 year period. When the estimates are examined by NRCS geographic regions, the southeast region had the largest net loss and the west region had the only net gain.

Estimated Palustrine and Estuarine Wetland Losses and Gains in the United States Between 1992 and 1997
NRCS Region	Gross Losses	Gross Gains	Net Change
East	- 57,600	15,400	- 42,200
Southeast	- 216,900	110,500	- 106,400
South Central	- 84,100	78,400	- 5,700
Midwest	- 74,200	48,400	- 25,800
Northern Plains	- 37,000	34,300	- 2,700
West	- 36,200	56,200	+ 20,000
Total	- 506,000	343,200	- 162,800

Gross Loss and Gross Gain

Chart for Palustrine & Estuarine Wetland Losses and Gains (10 KB)
Table for Palustrine & Estuarine Wetland Losses and Gains (7 KB)

Text Version of Palustrine & Estuarine Wetland Losses and Gains.

Details for Palustrine & Estuarine Wetland Losses and Gains.

Net Change

Chart for Palustrine & Estuarine Wetland Net Change (21 KB)
Table for Palustrine & Estuarine Wetland Net Change (7 KB)

Text Version of Palustrine & Estuarine Wetland Net Change.

Details for Palustrine & Estuarine Wetland Net Change.

Classification of Palustrine and Estuarine Wetland Losses Between 1992 and 1997

NRI estimates of Palustrine and Estuarine wetland losses were attributed to one of the following categories:

Development - Loss occurring on land cover/use category of urban and built-up or rural transportation.

Agriculture - Loss occurring on land cover/use category of cropland, pastureland, CRP land, farmsteads or other farmland.

Silviculture - Loss occurring on forestland.

Miscellaneous - Loss occurring on all other land cover/use categories; including mined land, rangeland, and other barren lands. Natural variations in climatic cycles and hydrology are responsible for the majority of these losses in this category.

NRI results for the United States indicate 49% of the Palustrine and Estuarine wetland losses were to development, followed by agriculture (26%), miscellaneous (13%), and silviculture (12%). In the NRCS West Region, the highest loss category was agriculture (33%), followed by development (29%), miscellaneous (28%), and silviculture (10%).

Classification of Palustrine and Estuarine Wetland Losses Between 1992 and 1997
Loss Category	United States Totals (Acres)	Percent in United States	NRCS West Region (Acres)	Percent in West Region
Development	- 247,500	49%	- 10,400	29%
Agriculture	- 133,800	26%	- 11,800	33%
Miscellaneous	- 64,600	13%	- 10,200	28%
Silviculture	- 60,100	12%	- 3,800	10%
Gross Loss Total Acres	- 506,000	100%	- 36,200	100%