When we think of wetlands, our mind may paint a picture of a swampy area with open water, and maybe a heron or alligator. Despite common perception, not all wetlands are the same. — These watery features come in all shapes, sizes, and locations along with a unique system of processes and purpose.
Wetlands are diverse and the difference between dry and wet environment lies along a gradient. Therfore, there cannot be one perfect definition to represent what a wetland is. Scientists have developed criteria to identify wetlands and aid in assessment, inventory, and management .
Figure 1. An example used by scientists to start the process for wetland delineation.
the gradient or degree of flooding or soil saturation across a landscape .
plants adapted to grow in water or in a soil that is occasionally oxygen deficient due to saturation by water .
soils that are sufficiently wet in the upper root zone and may develop anaerobic (oxygen lacking) conditions during the length of at least 1-2 growing seasons .
As seen below in Figure 2 and 3; some wetlands are flooded year-round while other water levels fluctuate. The wetland hydrology differs depending on location and the geography of the landscape.
Figure 2: A simplified example of a wetland water gradient dependent on elevation and tidal ranges.
You may not live close to a coastal marsh, but many water sources eventually connect to a wetland on the coast, making the streams, lakes, and swamps in your backyard an important link to the larger watershed. That’s why it’s important to support, respect, and appreciate the water systems and land of everyday life. CWPPRAprojects restore and protect these systems to support the livelihood and cultures of Louisiana and to protect the land we value so dearly.
In next week’s edition of Wetland Wednesday, we’ll look at how scientist use vegetation and soils to classify wetlands!
The recent cold weather in Louisiana may have been the end of the road for some plants as temperatures dipped into the teens and stayed below freezing for full days. The hibiscus in your garden may have survived because you gave it extra insulation, but what about marsh plants? Louisiana salt marshes are home to black mangroves (Avicennia germinans), but this represents the very northernmost part of their range. Of the three mangrove species found in the continental United States [red (Rhizophora mangle), black, and white (Laguncularia racemosa)], black mangroves are the most cold-hardy, but they are still sensitive to winter weather- they generally cannot establish above 28° N and S latitude because winters are too cold (a sliver of the Birdsfoot Delta is below 29° N, so we really are at their limit).
The three mangrove species are also different in their tolerances for other environmental conditions: red mangroves establish in the intertidal zone, while black and white mangroves are found at higher elevations, and white mangroves can colonize areas with little to no soil. In Florida where all three species occur, mangrove zones can be defined from the water extending inland and up in elevation .
Black mangroves are an important component of Louisiana salt marshes, providing habitat to a variety of species. The complex root systems trap and collect sediment, limiting erosion and maintaining land. Juvenile invertebrates and fish find shelter among the roots, while seabird chicks, such as brown pelicans and roseate spoonbills, are protected from high water events and predators up in the branches.
CWPPRA projects that nourish barrier islands and create new marsh habitat help maintain black mangrove populations by providing new land for the plants to colonize; in turn, the mangroves help the new land persist in the face of wind and wave energy.
Marshes within the Hog Bayou Watershed mapping unit are
stressed due to limited freshwater input and seasonal salinity
spikes exacerbated by construction of the Mermentau Ship
Channel. Other contributors to land loss in the area are
subsidence, compaction, and erosion of organic soils.
Currently, the project area is characterized as large, open
water with degraded areas of wetland vegetation and low
organic production. The dredging of the Mermentau Ship
Channel increased tidal amplitude and salt water intrusion
into the watershed.
The goal of the project is to create new wetland habitat,
restore degraded marsh, and reduce wave erosion of organic
soils. The project would promote the expansion of emergent
marsh and submerged aquatic vegetation throughout the
project area. Material dredged from the Gulf of Mexico will
be used to create and nourish approximately 420 acres of
marsh. Smooth cordgrass will be planted throughout the
area. To help facilitate estuarine fisheries access, constructed
retention levees will be degraded and approximately 11,756
linear feet of tidal creeks will be constructed.
The project is located in planning Region 4, Mermentau
Basin in Cameron Parish within the Hog Bayou Watershed
Coast 2050 Mapping Unit. The mapping unit is bordered by
Lower Mud Lake to the west, the Gulf of Mexico to the
south, Rockefeller Refuge to the east, and Louisiana
Highway 82 to the north.
This project is on Priority Project List (PPL) 23.
The South Grand Chenier Marsh Creation – Baker Tract sponsors include:
This area is undergoing shoreline erosion, interior wetland
loss, overwash, and breakup. The Gulf shoreline erosion rate
has doubled from 1988 to 2006. Project area marshes also
are being eroded at -11.8 ft/yr between 2003 to 2006 as well
as being converted to open water from internal breakup.
Restoration would expand the Gulf shoreline structural
integrity and associated protection by tying into two recently
constructed projects to the east and address one of the
remaining reaches of the Barataria/Plaquemines shoreline.
The design includes fill for a beach and dune plus 20-years
of advanced maintenance fill, as well as fill for marsh
creation/nourishment. The location of the type and amount
of sediment needed to construct this project already has been
identified under the East Grand Terre Project that is presently
under construction. Approximately 127 acres of beach/dune
fill would be constructed and approximately 259 acres of
marsh creation/nourishment would be constructed. Intensive
dune plantings would be conducted by seeding and installing
approved nursery stock. About half of the
marsh platform would be planted with cordgrass and
portions of the dune, swale, and marsh would be planted
with appropriate woody species. Containment dikes would
be breached no later than year three to allow tidal exchange
with the created marsh.
The project is located in Region 2, within the Barataria Basin
portion of Plaquemines Parish.
This project is on Project Priority List(PPL) 19.
The Cheniere Ronquille Barrier Island Restoration project sponsors include:
The coastal restoration community has long recognized the benefits of vegetative plantings in restoration. Many marsh creation and most terracing projects require plantings to insure success. Coastal shoreline plantings have also proven to be very effective and some have demonstrated the ability to not only stop shoreline erosion but to facilitate accretion, the process of increasing sediments. Recent hurricane events have exposed a need to have a mechanism in place where large-scale planting efforts can be deployed in a timely manner to specifically targeted areas of need, anywhere along the coast. Although the CWPPRA program can fund specific large-scale planting projects, the normal program cycle for individual projects can delay needed restoration plantings for a number of years.
The goals of this project are to facilitate a consistent and responsive planting effort in coastal Louisiana that is flexible enough to routinely plant on a large scale and be able to rapidly respond to critical areas of need following storm or other damaging events. This project set up an advisory panel consisting of representatives from various state and federal agencies who would assist in the selection of projects for funding. The project also set up a mechanism by which project nominations would be submitted for consideration. The equivalent of 90 acres of interior marsh and 40,000 linear feet of coastal shoreline will be planted per year over a 10 year period to effectively create/protect a total of 779 net acres of marsh over the 20-year project life.
The project features are located in the coastal zone of Louisiana.
This project is on Priority Project List (PPL) 20.
The Coastwide Vegetative Planting project sponsors include:
Louisiana’s shorelines are eroding at a drastic pace, some at rates up to 50 feet per year. The fertile but fragile soils found in the wetlands are susceptible to wave energy. As land is lost, water bodies merge together, which can increase wave fetch and shoreline erosion. Behind these shorelines lie communities, highways, and infrastructure that are at risk of washing away.
Various techniques to defend the coastline have been tested and applied under CWPPRA. Rock revetments, oyster reefs, concrete panels, and other fabricated materials have been constructed along otherwise unstable shorelines to abate wave energy and reduce erosion. These structures are designed to break waves, and they often trap waterborne sediments behind the structures that, over time, can become new land.
Through the course of the CWPPRA program, advancements have been made in shoreline structures that have helped maintain natural processes while providing critical protection. Such advancements have included using lighter-weight materials that require less maintenance and can be constructed on organic sediments. Other advancements include low-relief structures that are designed to trap sediments and natural breakwaters such as reefs that can self-maintain and support other ecological functions. Other natural shoreline protection measures include vegetative plantings, whose roots help secure soils and can promote accretion. These projects are implemented with consideration for minimizing impacts to the surrounding environment. Although some shoreline structures may look foreign in a natural landscape, they are necessary features that physically protect communities and hold wetlands in place by mitigating the harsh forces that move to destroy them.
Invasive species (harmful non-native species) are one of the most significant drivers of global change. Consequently, they can have substantial impacts on the economy, infrastructure, and humans. Society must address invasive species as a priority, which is exactly what National Invasive Species Awareness Week intends to do. The objective of National Invasive Species Awareness Week is to bring attention to the impacts, prevention, and management of invasive species – and all those who are working toward healthy, biodiverse ecosystems.
Wetlands provide benefits ranging from water filtration to storm surge protection; however, wetlands have become vulnerable to invasive species. Known as major contributors to wetland and coastal habitat loss, invasive species also threaten native species, including endangered species that rely exclusively on the wetlands for survival. The foreign animals that have been recognized as invasive to coastal wetlands include Asian carp, wild boar, island apple snails, and nutria. Invasive plant species include Chinese tallow, common reed, and purple loosestrife. Invasive animal and plant species have altered the health of wetlands by out-competing native species for food and natural resources, often without any natural predator or control to halt the resulting aggressive spread through an area. CWPPRA strives to protect wetlands by constructing methods to diminish the invasive threat and restore native species’ dominance and health within the wetlands.
For a full list of Invasive species in Louisiana, click here.
The invasive plant, giant Salvinia, was first observed in Chenier Plain marshes in 2009. Since then it has spread throughout most of the Louisiana Chenier Plain marshes. This plant can stack up above the water surface to as much as 6 to 12 inches. Under such conditions, oxygen exchange is greatly reduced, and decay of shaded Salvinia can easily cause anoxic conditions in affected areas. As a result, habitat quality of badly infested areas is severely degraded, and may affect many species typical of fresh marshes, including many species of management concern (alligator snapping turtle, mottled duck [including critical brood rearing habitat], wintering migratory waterfowl, black rail, king rail, little blue heron, whooping crane, and peregrine falcon).
LSU Ag. Center has a pond in Jeanerette, La. which is capable of producing weevil-infested Salvinia, but LSU does not have funding to operate a weevil production facility here. Costs associated with this project consists primarily of supplies and one part-time position to operate the pond, coordinate public weevil harvests, keep records of release locations, monitor Salvinia problem areas, assist landowners in conducting weevil release, relay infested Salvinia to new locations, and conduct public outreach to promote the program.
The Louisiana Salvinia Weevil Propagation Facility project is located coastwide.
This project was approved for Phase I, Phase II, and Operation in January 2017.
This project is on Priority Project List (PPL) 26.
The Louisiana Salvinia Weevil Propagation Facility project sponsors include:
Frequently included in the visionary imagery of Louisiana’s swamp landscape is gray, vine-like vegetation commonly seen draped on cypress branches. Thought to be a moss, Spanish moss is actually a bromeliad related to pineapples and succulent house plants in the same taxonomic family. Similarly, Spanish moss is not native to Spain, as is commonly thought; it is, however, native to South America and the Caribbean and grows from Texas to Virginia in the U.S. Inclined to moist areas, an ideal habitat for Spanish moss is a tree residing in a tropical swampland. Spanish moss is a rootless epiphyte—although Spanish moss is located on tree branches, it does not obtain food or water from the supporting tree as a parasite would. Spanish moss spreads and propagates from fragments known as festoons which are carried by wind or birds and initiate growth after landing in suitable conditions. An abundance of wetland wildlife utilize Spanish moss for survival needs, such as birds building nests and spiders and frogs hiding from predators.
Plants of the wetlands are generally known to be highly dependent upon specific conditions, such as salinity, proximity to water, and vegetation type.
While some plants are able to adapt to condition alterations, other species do not overcome change as well. However, a major threat to all wetland vegetation is hydrilla.
Hydrilla is a non-native, invasive aquatic plant that has staked its claim by out-competing native plants and obstructing waterways. Hydrilla is a submerged, perennial plant that prefers freshwater, but can tolerate up to 7% salinity. This aggressive plant is known for clogging waterways, impeding natural flow, affecting human use such as fishing and seafood harvest, and clogging intakes and municipal drinking water supplies. Hydrilla can take over an area quickly as a result of its ability to multiply rapidly using four different strategies. Regrowth of stem fragments containing at least one node into a new plant, tubers on rhizomes producing new tubers, leaf turions that settle into sediment and form a new plant, and seed dispersal are all methods of reproduction for hydrilla. Hydrilla can out-compete native plants by its ability to tolerate low and high nutrient conditions in addition to growing in low light environments. Hydrilla is also successful in out-competing other plants by growing at a rate of one inch per day until reaching the water’s surface, followed by branching out to form a mat of vegetation which blocks light to other plants.
In order to control the growth of hydrilla, salvinia weevils have been released into severely affected areas. The salvinia weevil lives exclusively on hydrilla as a food source, thus reducing growth rates to allow control of the plant. The Coastal Wetlands Planning, Protection, and Restoration Act is currently researching the best, most beneficial method of controlling and eradicating invasive plant species.