What are wetlands?• The U.S. Fish and Wildlife Service defines wetlands as the “…

lands transitional between terrestrial and aquatic systems where the water table is usually at or near the land surface or the land is covered by shallow water.” (Cowardin et al., 1979)

• Wetlands must have all of the following characteristics:

– Hydrology—presence and duration of water– Hydric soil—poorly drained and with evidence of low or

fluctuating oxygen– Hydrophytic vegetation—dominance of vegetation adapted to

saturated soil conditions

Wetland Functions

The physical, chemical, and biological interactions within wetlands are often referred to as wetland functions

Water filtration and purification Trapping sediments and contaminants Flood control and stream flow regulation Erosion reduction Habitat for aquatic and terrestrial plants and animals

Wetland Hydrology

• Area is inundated or saturated to the surface for at least 5% of the growing season in most years– Growing season is based on soil temperature and

is determined for regions by the USDA– Most years = 51 out of 100 years

Wetlands are NOT always wet!Wetlands are NOT always wet!

Hydric Soil• A soil that is saturated, flooded, or ponded

long enough during the growing season to develop anaerobic conditions in the root zone– Tend to be dark in color and have mottles of iron

staining

Function of Hydric Soils

• Transformation of various elements in hydric soils– Denitrification – NO3

- N2

– Converts sulfates (SO4-2) into sulfides (H2S) and insoluble

complexes with phosphate and metal ions –removes sulfates caused by anthropogenic activities

– Sequesters C – decomposition of organic material

Hydrophytic Vegetation• Plant species that are adapted

for life in saturated soils– Anaerobic soil conditions– Soggy or waterlogged soils

• Require adaptations for better support

• Require adaptations for gas exchange

• Hydrophytes are plants growing in water or on substrates that are periodically deficient in oxygen

Hydrophytes• Plants classified by tendency to occur in wetlands

– Obligate: Almost always occur in wetlands (>99%)– Facultative Wetland: Usually occur in wetlands (67-99%)– Facultative: Equally likely to occur in wetlands or non-wetlands (33-

67%)– Facultative Upland: Usually occur in non-wetland (67-99%) but

occasionally in wetlands (1-33%)– Upland: Almost always occur in non-wetlands (>99%)

Function of Wetland Biota• Plants reduce the erosive potential of peak flows

stabilize shorelines and levees

• Produce an abundance of detritus consumption by commercially important vertebrates and invertebrates.

Wetland Biota

• Large volume of biomass – commercially important plants and animals– 95% of the harvested fish and shellfish species are

wetland dependent– Wetland timber – about 22 million ha

Plant and Animal Communities Wetlands in the United States support

about 5,000 plant species 190 species of amphibians 80% of America’s bird population

Provide critical habitat Wetlands occupy 3.5% of the land area large

amount of habitat yet a small amount of habitat

Water Storage Wetlands are reservoirs for rainwater and runoff

– storm abatement (coastal) – flood mitigation (riparian)

Moderate stream flows Reduce peak water flows Maintain flow during low water

Help prevent flooding by temporarily storing water Recharge groundwater

Water QualityWater Filtration or Purification Remove nutrients, pesticides, metals, and

bacteria from surface waters where they are absorbed, consumed or broken down by plants, animals, and chemical processes within the wetland

Wetlands are the earth’s kidneys Limit eutrophication and pollution of water

bodies

Particulate Removal

Filter out sediments and particles suspended in runoff water

Sediments typically contain adsorbed nutrients and metals

Limits siltation Reduces Habitat Impacts

Geologic Function of Wetlands

• Anaerobic conditions exceptional preservation qualities– Store pollen, fossils, and human artifacts– Animals from the last Ice Age were discovered in

bogs.

• Used to reconstruct paleoclimates, animal evolution, and vegetation type

Kinds of Wetlands

• Bog – peat-accumulating with no inflows or outflows; supports mosses

• Bottomland – lowlands along streams and rivers

• Fen – ground-water fed; peat accumulating

• Marsh – frequently inundated; emergent herbaceous vegetation

• Mire – peat-accumulating (Europe)• Moor – peat-accumulating (Europe)• Muskeg – Large expanses of

peatlands or bogs (Canada/Alaska)• Peatland – any wetland that

accumulates decaying plant matter

• Playa – marshlike ponds similar to potholes (southwest U.S.)

• Pothole – shallow, marshlike pond; found in Dakotas and Canada

• Reedswamp – marsh dominated by common reed (Europe)

• Slough – swamp or shallow lake system

• Swamp – wetland dominated by trees or shrubs

• Vernal Pool – shallow, intermittently flooded wet meadow

• Wet Meadow – grassland with waterlogged soil near the surface – without water for most of year

• Wet Prairie – similar to marsh but water levels intermediate between marsh and wet meadow

Vary based on geographic location, language, etc.

Source: Mitsch and Gosselink, 1993.

Rookery Bay National Estuarine Research Reserve – Salt MarshRookery Bay National Estuarine Research Reserve – Salt Marsh

Mangrove Swamp – Everglades National Park – Estuarine WetlandMangrove Swamp – Everglades National Park – Estuarine Wetland

Ritchey Woods Natural Area – Riparian WetlandRitchey Woods Natural Area – Riparian Wetland

Point Pelee National Park – Ontario, Canada - LacustrinePoint Pelee National Park – Ontario, Canada - Lacustrine

Western US - Palustrine Wetland – in topographic lowWestern US - Palustrine Wetland – in topographic low

Ritchey Woods Natural Area – Forested WetlandRitchey Woods Natural Area – Forested Wetland

Photo: Marion Jackson

Photo: http://www.epa.gov/owow/wetlands/types/vernal.html