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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)

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what are wetlands
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
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
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!

hydric soil
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
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
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
  • 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
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
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
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
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 quality water filtration or purification
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
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
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

Kinds of Wetlands

Vary based on geographic location, language, etc.

Source: Mitsch and Gosselink, 1993.