Wetland Functions
General Effects on Stream Flow
General Effects on Flooding
General Functions of Estuarine Wetlands
General Functions of Riparian Wetlands
Habitat Provided by Prairie Potholes
Relationship Between Wetlands and Fish Harvest
Rare Species Associated with Wetlands
Passive Wetland Use
Resource Harvest from Wetlands
Difficulty with Wetland Evaluations
Wetland Evaluation Methods
HEP Method Output
HMG Wetland Classification
Replacement Evaluation
Wetland Alterations
Historical Wetland Loss - Iowa / California
Historical Wetland Loss - Coastal
Coastal Wetland Conversions
Palestrine Wetland Loss / Gain
Non-federal Wetland Losses 1982-1987
Wetland Loss in U.S.
Total Wetland Loss
Wetland Conversians
Trend of Drained Agricultural Land
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ABIOTIC

Flood Mitigation
Storm Abatement
Aquifer Recharge
Water Quality

Nutrient Retention
Sediment Trapping

Bank Stabilization

BIOTIC

Wildlife Habitat
Aquatic Habitat
Downstream /In-Basin Food Chain Support

HUMAN

Active Recreation
Passive Recreation
Resource Harvests

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FUNCTIONS OF RIPARIAN WETLANDS

 

Fig 15-6. Illustration of several of the potential wetland values for riparian wetlands during a) flood season ; b) dry season.( Mitsch et al., 1979).

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THREATENED AND ENDANGERED SPECIES ASSOCIATED WITH WETLANDS

 

TAXON	NUMBER SPECIES ENDANGERED	NUMBER SPECIES THREATENED	% U.S. TOTAL THREATENED OR ENDANGERED
PLANT	17	12	28
MAMMALS	7	-	20
BIRDS	16	1	68
REPTILES	6	1	63
AMPHIBIANS	5	1	75
MUSSELS	20	-	66
FISH	26	6	48
INSECTS	1	4	38
TOTAL	98	98

Fig 15-3. Niering 1988, from USDI, FWS, 1986.

 

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Difficulty with Wetland Evaluations

 

Multiple Values

Public Values vs. Commercial

Values in Relation to Uplands (Mosaic)

Long-Term

Biased by Society



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Wetland Evaluation Methods

 

Habitat Evaluation Procedure (HEP) - U.S. Fish and Wildlife Service

Wetland Evaluation Technique (WET) - Federal Highway Administration

Hydrogeomorphic Approach (HGM) - U.S. Army Corps of Engineers

Economic Approach

-willingness to pay

-replacement costs



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HEP Method Output

 

		Furure with Project Plan "A"b	Furure with Project plan "B"c	Furure without Project
Species	Baseline Condition	50 yrs 100yrs	50 yrs 100yrs	50 yrs 100yrs
		Terrestrial
Racoon	0.7	0.5..................0.6	0.8.................0.8	0.7.................0.9
Beaver	0.7	0.2..................0.2	0.4.................0.3	0.6.................0.4
Swamp Rabbit	0.7	0.2..................0.2	0.8.................0.8	0.7.................0.4
Green Heron	0.9	0.2..................0.1	0.8.................0.9	0.9.................1.0
Mallard	0.8	0.3..................0.2	1.0.................0.9	0.9.................1.0
Wood Duck	0.8	0.3..................0.2	0.9.................1.0	1.0.................1.0
Prothonotary Warbler	0.8	0.3..................0.1	0.6.................0.7	0.8.................0.9
Snapping Turtle	0.8	0.4..................0.2	0.8.................0.7	0.8.................0.9
Bullfrog	0.9	0.3..................0.3	0.8.................0.9	1.0.................1.0
Total Terrestrial HSI	7.1	2.7..................2.1	6.9.................7.0	7.4.................7.5
Mean Terrestrial HSI	0.8	0.3..................0.2	0.8.................0.8	0.8.................0.8
		Aquatic
Channel Catfish	0.3	0.3..................0.4	0.4.................0.4	0.4.................0.4
Largemouth Bass	0.4	0.2..................0.3	0.7.................0.8	0.4.................0.4
Total Aquatic HSI	0.7	0.5..................0.7	1.1.................1.2	0.8.................0.8
Mean Aquatic HSI	0.4	0.3..................0.4	0.6.................0.6	0.4.................0.4

Fig.15-5. Comparison of the Impact of Two Management Plans and a No-management Control in a Cypress-Gum Swamp.*

*` Numbers in the tables are habitat suitability index (HSI) values, which have a maximum value of 1 for an optimal habitat.

b` Chanelization of water and clearing of swamp for agriculture development with a loss of 324 ha of wetland.

c` Construction of levees around swamp for flood control with no loss of wetland area.

Source: Schamberger et al., 1979.

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Replacement Evaluation

Societal Support	Replacement Technologies
Peat accumulation Accumulating and storing matter(peat)	Artificial fertilizers Redraining ditches
Hydrologic Function   Maintaining Drinking Water Quality Maintaining ground water level Maintaining surface water level Moderation of water flows	Water transport Pipeline to distant source Well driling Saltwater filtering Dams for Irrigation Pumping water to dam Irrigation pipes and mavhines Water transport for domestic animals Regulate gauge Pumpuin water to streams
Biogeochemical Functions   Process sewage, cleaning nutrients and chemicals Maintaing drinking water quality Filter to coastal waters	Mechanical sewage treatment Sewage transport Sewage treatment plant Clear-cutting ditches and streams Water quality inspections Water purification plant Silos for manure from domestic animals Nitrogen filtering Water transport Nitrogen reduction in sewage
Food Chain Functions Providing food for humans and domestic animals Providing cover Sustaining anadromous trout populations Sustaining other fish species and wetland dependent floura and fauna Species diversity; storehouse for genetic material Bird watching, sport fishing, boating, and other recreational values Aesthetic and spiritual values	Agricultural production Import of food Roofing materials Releases of hatchery raised fish Farmed salmon Work by non profit organizations Replacements not possible

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Wetland Alterations

Water Level

draining

channeling

construction of dams

filling

water extraction

highway construction

Nutrient Level

sewage

agricultural runoff

sediments

Man Made Disturbances

discharge of toxic substances

acid mine drainage

mineral extraction (phosphates, gravel, sand)

peat extraction

Natural Disturbances

subsidence

drought

hurricanes

erosion

biotic effects - "eat-outs"

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Trend of Drained Agriculture Land

Fig. 16-3. Trend of drained farmland in the U.S. from 1900 to 1980 (Gosselink and Maltby, 1990, based on data from Office of Technology Assessment, 1984)

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Historical Wetland Loss

Fig.30. Historical losses of wetlands in Iowa and California.(from Bishop 1981 and U.S. Fish and Wildlife Service 1977).

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Historical Wetland Loss - Coastal

Fig 31.Rate of coastal wetland loss in the conterminous U.S. (from Gosselink and Bauman 1990). Estimates include both estuarine and tidal freshwater wetland losses.

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Coastal Wetland Conversions

Fig 6. Fate of converted estuarine emergent(coastal) wetlands, min-1970's to mid-1980's.

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Palestrine Wetland Loss / Gain

Fig.7. Palustrine wetland gains and losses, mid-1970's to mid-1980's.

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Non-Federal Wetland Loss 1982- 1987

Table 2. NRI-based estimates of wetland area in 1982 and 1987 (in 100's of ha)

Region	Total Area '82*....................'87*	Area lost........gained	Retained(%)	Net Change (1987-1982)	Change(%)
West	2628.3.........2476.7	157.3........5.7	94.0	-151.6	-5.77
Midwest	10347.3......10314.0	51.6........18.3	99.5	-33.3	-0.32
Southwest	14983.7......14847.6	140.2........4.1	99.1	-136.1	-0.91
Northeast	5531.8..........5489.6	43.8..........1.6	99.2	-42.2	-0.76
Total	33491.1......33127.9	393.9......29.7	98.8	-363.2	-1.08

 

*Wetlands that were involved in a transfer of ownership between federal and nonfederal land are not included in these estimates.

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Wetland Loss in U.S.

Fig 1.States that lost more than 50% of their wetlands between the 1780's and mid-1980's (listed states shaded)(after Dahl 1990)

State	% Lost	State	% Lost
Alabama	50	Maryland	73
Arkansas	72	Michigan	50
California	91	Mississippi	59
Colorado	50	Missouri	87
Connecticut	74	Nevada	52
Deleware	54	New York	60
Idaho	56	Ohio	90
Illinois	85	Oklahoma	67
Indiana	87	Pennsylvania	56
Iowa	89	Tennessee	59
Kentucky	81	Texas	52

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Total Wetland Loss

Fig 27. Original and remaining acreages of wetlands in the counterminous U.S. (from Roe and Ayres 1954; Frayer,et al., 1983).

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Wetland Conversions

Uses	1950-1970	1970-1980	1980-1990
Agriculture	87%	54%	37%
Urban	8	5	48
Open Water/Barren	-	-	15
Forest	-	-	-
Other	5	41	-

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