Wetlands
What is a wetland?
•
There are three characteristics that describe a
wetland:
1. Hydrology
– There must be water at or near the surface of the
land for a designated amount of time.
2. Soils
– Must be hydric or saturated with water to create an
anaerobic (oxygen-free environment).
3. Plants
– Must be “wetland plants,” meaning that they require
lots of water and the anaerobic conditions that the
hydric soil creates. (Smith & Smith, 2001)
Two of the most common wetlands
Marshes
• Wetlands that have lots of herbaceous plants.
• Also called “wet grasslands”
Swamps
• Wetlands that are forested by large trees.
Two components of hydrology
1. Physical
Characteristics
–
Precipitation, surface
and subsurface flow,
direction, chemistry,
and kinetic energy of
the water.
2. Hydroperiod
–
Duration, frequency,
depth, and flood
season
Hydrology
• Basin Wetlands
(lakes and ponds)
– Physical: Water flow
is vertical
(precipitation)
– Hydroperiod: Long
with floods during
periods of high rainfall.
Hydrology
• Riverine Wetlands
(periodically flooded
banks of rivers and
streams)
– Physical: Water flow
is both vertical and
horizontal
(precipitation and
stream/river flow)
– Hydroperiod: Have
short periods of
flooding with
stream/river flow.
Hydrology
• Fringe Wetlands
(along coastal areas of
large lakes and oceans)
– Physical: Water flow
is both vertical and
horizontal
(precipitation and tidal
flow)
– Hydroperiod: May be
short and regular. Is
not seasonal like basin
wetlands.
Soils
• Soil- a mixture of mineral particles, air,
water, bedrock, living and decaying
organisms.
• There are literally thousands of different
soils that can serve as great indicators
within an ecosystem. Although each type
of soil is made of three basic components,
(sand, clay, and silt) they can be classified
based on the amount of each.
Where do soils come from?
– Soils form as a result of bedrock being broken down
into smaller particles.
• Bedrock is the igneous, metamorphic, and
sedimentary rock that is in the lithosphere of the
earth (the section of earth closest to the
surface).
– It may take hundreds or thousands of years to form
10cm of soil.
– Animals, insects, and plant roots can also help break
down bedrock and introduce air into soils.
• Other organic matter, such as dead organisms,
also contributes to the soil composition.
Three types of soils
1. Sandy soils
– Contain mineral grains ranging from .052mm in diameter.
2. Silt soils
– Soils that have grains ranging from .002.05mm in diameter.
3. Clay soils
– Contain mineral grains smaller than .002mm
in diameter.
Soil Properties
• Sandy soils
– Has good drainage
and aeration
– Does not store water
well
– Is not suitable for most
plants
Soil Properties
• Silt Soils
– Soils made from
minerals
– Granule sizes are
between sandy and
clay.
– Also known as “rock
flour” or “stone dust”
when produced by
glaciers
Soil Properties
• Clay soils
• Hold water very well
• Do not drain water
easily
• Do not have space for
air
• Is not suitable for
most plants
Soil Properties
• Loam soils
• Soils that contain an
equal amount of sand,
silt, and clay are called
Loam Soils
• The mixture of sand, clay
and silt make loam soils
an optimal place for
plants to grow.
• Are able to hold water
and air.
Soil Profiles
• Soil profiles are
cross-sections of soil
that extends from the
surface to the
bedrock. It is usually
broken into layers
called “horizons”.
– Horizon O- Topsoil
– Horizon A- Subsoil
– Horizon B- Partially
weathered bedrock
– Horizon C- Bedrock
Wetland Plants
• Plants in wetlands are categorized according to their
ability to grow in water or hydric soils.
– Obligate wetland plants
• These plants are found in wetlands 99% of the time.
– Facultative wetland plants
• Usually live in wetlands (67-99%) but are sometimes found in nonwetlands
– Facultative plants
• Are found in wetlands (34-66%) and uplands
– Facultative upland plants
• Usually live in non-wetlands (67-99%) but are sometimes found in
wetlands
– Obligate upland plants
• These plants are found in uplands 99% of the time.
Native vs. Exotic
• If a plant is native to a particular area, then it is
originally from that area (prior to European
settlement).
– Native plants provide food and habitat for native animals.
Without this, the native animals may be forced to migrate
to areas.
– Native plants also keep local genes viable and in the
gene pool.
Native vs. Exotic
• Exotic plants were not originally in the area and
have been carried to the area in some way.
– Exotic plants can become invasive where they dominate
the ecosystem preventing opportunities for growth for the
native plants.
– Exotic plants also out grow native plants because they
have no native predators.
– Invasive exotic species are the second leading cause of
native species extinction (habitat loss being number
one).
Why are wetlands important?
• Wetlands serve many roles in our ecosystems.
A few of these roles are:
– Filtering water (removes things like pollutants and
sediment)
– Protect uplands from floods by temporarily storing
some of the water
– Provide sources of food
– Wildlife habitats
– Creates healthier watersheds by removing particles
from runoff before it reaches the streams.
– Prevent erosion when on banks of streams, rivers,
and lakes
What happens when wetlands are
destroyed?
• Destruction of wetlands can cause many
problems such as:
– Increased floods
– Water quality problems
– Population decrease in plants and animals
that live in wetlands
Can builders destroy wetlands?
• Section 401and 404 of the Clean Water
Act require developers that are going to
destroy a wetland to do three things:
– Avoid changing wetlands when possible
– When a wetland is impossible to avoid, they
must do as little damage as possible.
– If a wetland is destroyed, they must rebuild a
wetland in another place unless they pay into
a special fund to restore streams and
wetlands.
How can wetlands be restored?
• If a section of wetland is destroyed,
environmental firms will help rebuild a
wetland in another area. The U.S. Army
Corps decide how much wetland must be
rebuilt based on the quality of wetland that
is being destroyed. Once the amount is
determined, an environmental company
will begin restoration by completing (but is
not limited to) the following components:
How can wetlands be restored?
Continued
• If developers do not pay into the fund, they must find an area to
create a wetland.
– This area can be a degraded existing wetland or could be an area
where a wetland would be appropriate.
• They will plant vegetation that is appropriate for wetlands.
• They must make sure that the hydrology is consistent with a wetland
by making sure that the system can hold water.
• If hydric soils are not present, CAE will create a system where they
will develop over time.
• Excavate soil
• Dig a basin within a flood plain creating an area that can hold water.
Water can be retained in an area by creating dams.