Wetland Science
Wetland scientists examine:
- biology
- characteristic plants and
animals, microorganisms
of different wetland types
- vulnerability to disturbance
- adaptations to
wetland conditions
- flooding,
low oxygen
levels
- chemistry
- chemicals characteristic of wetland
conditions
- low or no oxygen
- pH
- nitrogen and phosphorus
cycling
- sulfur cycling
- iron and manganese
transformations under
different oxygen levels
-geology
- soil formation processes
- geochemistry
- organic matter content
-hydrology – water cycle
- sources, chemistry
Mineral soils
Organic soils
Defining wetlands
What features characterize a wetland?
-lowland areas
- might be transitional between terrestrial
and aquatic habitats
- can occupy isolated basin
- covered with shallow, temporary or intermittent
waters
- water might be present at the surface,
or within root zone
- soils often rich in organic matter,
anoxic (no/low oxygen)
- possess plants adapted to wet conditions
Diversity of wetland types
- makes defining/describing specific wetlands
difficult
- freshwater wetlands
- forested swamps, blackwater and
whitewater floodplain swamps,
cypress, hardwood-dominated,
bay swamps, shrub bogs, hydric hammock,
fen,
- marshes, bog, depression marsh, marl
prairie, wet prairie, potholes, playa
- coastal wetlands
- mangroves, salt marsh (Juncus-or
Spartina-dominated),
tidal freshwater marshes
For instance, in Florida
freshwater – 4 main categories of wetlands
- seepage wetlands
- floodplain wetlands
- basin wetlands
- 15 different types
- wet flatlands – 4 types
marine/estuarine – tidal marsh & tidal swamp
21 different types of wetlands – defined by
Florida Natural Areas Inventory (FNAI)
- used in wetland delineation, conservation
Defining Wetlands
- definitions/terminology of different types vary from
vaque -> very specific
- not all wetlands have same properties
- still young, developing field with much to learn
- function/roles
- diversity/habitat – regional variation
- natural variation through time
- resilience to disturbance
- multidisciplinary approach to scientific study
biology, chemistry, geology
- management/protection requires sound
science
- value system
- land for development – residential, commercial
- agricultural, etc.
- natural areas
- habitat/biodiversity protection
–> balance not easy to achieve
-wetland restoration – works for some
wetlands, not always the best
solution
-many different types, many definitions, some
confusing (contradictory?)
-older classification - simplistic, didn’t emphasize
unique qualities
-laws for regulation, protection
-> requires clearer classification
- scientific input important
- clarification of different categories
- management
- protection
Features of Wetland
1) water, at surface or root zone - shallow
- depth and duration of flooding - variable
- some continually flooded, others briefly
or with minimal flooding
- water levels can vary within a wetland,
shifting apparent ‘boundaries’ seasonally
or annually
2) ecotone (transition zone) between open water and
terrestrial systems – applies to many wetlands
- margins - share properties of both
- some scientists do not recognize wetland as
distinct ecosystem
3) defined by specific plant types
- animals, plants and microorganisms vary
- some tolerant of wet and dry conditions,
others require wet conditions
- indicator taxa - might not always be easy to
define
4) variable in size
- few acres -> large tracts
5) range from coastal -> inland
structure and function vary from wetland to
wetland
6) human impact varies depending on location
- rural - agricultural impact – non-point
sources of nutrients
- urban – pollution (often point source)
modified watershed & hydrology
result of variation-> one good definition doesn’t exist!
Why definitions needed?
- wetland scientists - need definition that
helps promote wetland study/differentiation
- flexible, but clear
- classification
- research
- inventory plants and animals
- wetland managers/regulators
- laws/regulations
- need definition with clear language,
legally binding
Scientific definitions
- Wetland definitions are lacking from most
contemporary ecology textbooks
- Limnology texts often include some definition:
ex. Dodson, 2005
“..characterized by soil saturated with water,
but with standing water less than 1 m deep,
often with extensive areas of floating or emergent
vegetation. Wetlands are also called marshes or
carrs. Swamps have trees standing in water.
Wetlands can be lentic or lotic.”
Scientific definitions
1)U.S. Fish and Wildlife Service - Circular 39, 1956
The term wetlands refers to lowlands covered with
shallow and sometimes temporary or intermittent
waters. They are referred to by such names as
marshes, swamps, bogs, wet meadows, potholes,
sloughs, and river-overflow lands.
Shallow lakes and ponds, usually with emergent
vegetation as a conspicuous feature, are included
in this definition, but the permanent waters of
streams, reservoirs, and deep lakes are not
included. Neither are water areas that are so
temporary as to have little or no effect on the
development of moist-soil vegetation.
- early definition, but useful
Later definition – 1979
Wetlands are lands transitional between
terrestrial and aquatic systems where the water
table is usually at or near the surface or that
land is covered by shallow water....
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 non-soil and is saturated
with water or covered by shallow water at
some time during the growing season of each
year.
introduced important concepts
- hydrophytes - plants adapted to wet
conditions
- hydric soils - soils formed during conditions
of saturation, flooding, or ponding long
enough during the growing season to
develop anaerobic conditions in the upper
part.
- general, flexible, comprehensive definition
- includes plants, soils, hydrology
- easier for scientists to use than managers
- does promotes classification, inventory
2) U.S. National Academy of Sciences - 1990s
-National Research Council Committee
- scientific review of past definitions
- regional variation
- scientific ability to analyze wetland properties
“A wetland is an ecosystem that depends on
constant or recurrent, shallow inundation or
saturation at or near the surface of the substrate.
The minimum essential characteristics of a
wetland are recurrent, sustained inundation or
saturation at or near the surface, and the
presence of physical, chemical, and biological
features reflective of recurrent, sustained
inundation or saturation. Common diagnostic
features of wetlands are hydric soils and
hydrophytic vegetation.
These features will be present except where
specific physiochemical, biotic, or anthropogenic
factors have removed them or prevented their
development.”
- most comprehensive definition
- common diagnostic features
– broader, more flexible than
previous definitions
3) International definition
- International Union for the Conservation of Nature
and Natural Resources – 1971
Ramsar Convention Definition
Areas of marsh, fen, peatland or water, whether
natural or artificial, permanent or temporary,
with water that is static or flowing, fresh,
brackish, or salt including areas of marine water,
the depth of which at low tide does not exceed
6 meters.
- includes a lot left out by U.S.
- river and coastal zones
- depth greater than most definitions
-advantage - included habitat used by migratory
birds
Legal definitions
- 1970's U.S. Army Corps of Engineers
- Clean Water Act
“dredge and fill” program
U.S. Natural Resources Conservation Service
‘Swampbuster’ provision - Food Security Act
-both designed for wetland protection
1)U.S. Army Corps of Engineers - 1984 definition
“The term wetlands means those areas that are
inundated or saturated by surface or ground
water at a frequency and duration sufficient to
support, and under normal circumstances do
support, a prevalence of vegetation typically
adapted for life in saturated soil conditions.
Wetlands generally include swamps, marshes,
bogs and similar areas.”
-Controversial - debated in courts
-has had rewording over the years
- clarify vegetation covered
Wetlands - considered part of the waters of U.S.
- since 1975, regulated by U.S. Army Corps of
Engineers
- review/regulated dredge-and-fill permits
- some citizens/companies have bypassed
permit process by destroying aquatic
plants
- included groundwater-supported wetlands
2) Food Security Act Definition - 1995
-wetlands in agricultural areas received protection in
1985
“ The term “wetland” except when such term is part
of the term “converted wetland” means land that A) has a predominance of hydric soils;
B) is inundated or saturated by surface or
groundwater at a frequency and duration sufficient
to support a prevalence of hydrophytic vegetation
typically adapted for life in saturated soil
conditions; and
C) under normal circumstances does support a
prevalence of such vegetation.
For purposes of this Act and any other Act, this
term shall not include lands in Alaska identified as
having high potential for agricultural development
which have a predominance of permafrost soils.”
-hydric soils - key component
- excludes Alaska - not science-based, but
political – allows development of wetland
areas in Alaska
Jurisdictional wetlands - legally defined wetlands
in U.S. under the jurisdiction of the Clean Water Act
(Section 404), or the swampbuster provision of
Food Security Act
- both definitions emphasize different things
- Corps - plants determine wetland presence
-designed for quick use to determine
jurisdiction
- FSA - hydric soils
- excludes non-hydric soils, and Alaska
-many wetlands recognized by scientists may fit into
legal definitions, not all- ex. riparian wetlands
Goal - delineate wetlands and boundaries
- ease, quick assessment
- clear, comprehensive
- user-friendly
- standard protocols for identifying wetlands
plants or soils (wetland delineation)
Florida Statutes
Chapter 62-340, Florida Administrative Code,
Delineation of the Landward extent of Wetlands and
Surface Waters, subsection
373.019(17)
“Wetlands means those areas that are inundated or saturated by
surface water or ground water at a frequency and a duration
sufficient to support, and under normal circumstances do support,
a prevalence of vegetation typically adapted for line in saturated
soils. Soils present in wetlands generally are classified as hydric
or alluvial, or possess characteristics that are associated with
reducing soil conditions. The prevalent vegetation in wetlands
generally consists of facultative or obligate hydrophytic
Macrophytes that are typically adapted to areas having soil
conditions described above. These species, due to morphological,
physiological, or reproductive adaptations, have the ability to
grow, reproduce or persist in aquatic environments or anaerobic
soil conditions. Florida wetlands generally include swamps,
marshes, bayheads, bogs, cypress domes, strands, sloughs,
wet prairies, riverine swamps and marshes, mangrove swamps
and other similar areas. Florida wetlands generally do not include
longleaf or slash pine flatwoods with an understory dominated
by saw palmetto.”
one definition - probably not possible nor practical
considering the objectives differ depending on
user.
-ecological, inventory purposes
-U.S. Fish and Wildlife Service definition most
accepted
- regulatory - U.S. Army Corps of Engineers definition