But Who Ate All the Oysters?
Scientists on Dauphin Island in the U.S. state of Alabama have built breakwaters using millions of oyster shells. They hope that algae, worms, barnacles, fish, and shellfish will colonize the shells, creating a unique type of living shoreline. Dauphin Island was seriously damaged by Hurricane Gustav in 2008, and engineers hope the oyster breakwaters will reduce the impact of future storms in the area.
A living shoreline is a way of managing coastal areas to protect, restore, or enhance the habitat. This is done through the placement of plants, stone, sand, and other materials. Living shorelines do not interrupt natural relationships between land, wetlands, and bodies of water.
Wetlands around the world have been damaged by dredging (digging). Most dredging is done to develop urban areas or expand ports. Dredging and drying a wetland can create more land for homes, businesses, or agriculture. Dredging a wetland near a harbor can allow more ships to dock, increasing the economic activity of the area. Dredging a harbor can also deepen the port, which allows larger ships, with more cargo, to dock.
Wetlands play an important natural role in coastal ecosystems. They prevent erosion of the land. Plants and trees anchor the soil and prevent it from washing out to sea. A wetland barrier between developed inland regions and the coast can protect fertile soil for agriculture, as well as development and recreation.
Wetlands also protect coastal areas from powerful storm surges. Storm surges are the waves that follow a hurricane or typhoon as it makes landfall. Storm surges can be more than a meter (three feet) tall. Hurricane Katrina, which devastated the U.S. city of New Orleans, Louisiana, in 2005, had a storm surge of about 7.5 meters (25 feet). Wetlands, with their spongy soil, absorb the energy and water of a storm surge. They also slow the surge. This protects homes, businesses, and agricultural areas.
Wetland habitats help clean waterways. Oysters, for instance, live in coastal wetlands and bays. Oysters are filter feeders. As they absorb nutrients from the water, they also absorb runoff and pollutants.
Wetlands also provide a habitat for a wide variety of organisms. Some organisms are commercially important to people, such as fish or crabs. Others play an important role in the coastal food web, such as seagrass, snails, or wading birds.
When people develop coastlines, they often protect the shoreline—and their property—by constructing rock, wood, or plastic seawalls. A seawall is a large, sturdy structure built to prevent erosion and damage from ocean waves. It extends, sometimes for kilometers, along a shoreline.
Constructing a seawall usually involves removing coastal vegetation such as seagrass, mangrove trees, and cattails. Without these plants, the biodiversity of the region shrinks. Insects, snails, and shrimp no longer have a reliable source of food. Birds and fish that prey on the insects or snails migrate elsewhere. The population of larger predators, such as muskrats or alligators, may fall sharply.
Living shorelines protect against erosion without removing vegetation or damaging coastal ecosystems. Unlike seawalls, living shorelines can adjust their height and width to the season or weather. They can expand during wet seasons and reduce their fertility during dry seasons. Living shorelines can be constructed by individuals, communities, or the government.
Goose Creek Tidal Wetlands Bank in the U.S. city of Chesapeake, Virginia, is a 4.2-hectare (10.4-acre) wetland. It was created by the Virginia Department of Transportation in 1982. That year, the department planned to build a new highway. The Goose Creek Tidal Wetlands were created to make up for wetland losses that would occur during highway construction. The government planted five species of salt marsh plants in the area. These plants were mostly reeds and cordgrass. The government then protected the wetlands from development.
Attracted by the new salt marsh, coastal species migrated to Goose Creek. Scientists have now identified 21 species of fish, including bass and anchovy, using the marsh. Invertebrates, such as shrimp and clams, are also part of the wetland ecosystem.
Types of Living Shorelines
There are many types of living shorelines. The type depends on the reason for creating it and the type of ecosystem involved.
Sometimes, living shorelines are built along recreational beaches to prevent erosion of sand and preserve the beach. This type of living shoreline may involve simply adding sand to the beach. It may also involve planting beachgrass to stabilize the sand, or building stone breakwaters. Breakwaters are structures placed offshore to reduce the power of incoming waves. This protects the beach from erosion. Breakwaters have the added benefit of creating calm water for swimming.
A living shoreline may be created along a river for recreational and commercial use. This type of living shoreline may include adding large rocks to the river bank. Frogs, insects, and plants live around river rocks. Moss and grasses help anchor sediment to the river bank. Stable river banks help reduce flooding and create a healthy river environment, allowing for sport fishing and expanded freshwater fisheries.
Some coastal communities create living shorelines to support or expand ecosystems that are already in place. Fringe marshes are an example of this type of living shoreline. Fringe marshes expand the natural ecosystem of a tidal marsh or swamp.
Creating fringe marshes may involve planting marsh grasses on the existing shoreline. The existing shoreline may also be expanded by creating sandbars or coastal area. Then, plants such as cattails, mosses, and sedges are planted. These attract insects. Larger predators such as birds may follow, building their nests among the plants and creating a healthy wetland habitat.
Many living shorelines include permanent support structures. These include:
- revetments: sloping structures placed directly on the shoreline. Revetments are usually made of riprap, a collection of large rocks or concrete fragments. Revetments are heavy “armor” for the shoreline.
- breakwaters: freestanding structures made of stone, sand, or other material placed offshore to reduce the power of incoming waves.
- sills: similar to breakwaters, but placed closer to shore.
- spurs: similar to breakwaters and sills, but attached to the shoreline or another structure.
- groins: large structures that extend straight out from the shoreline. Unlike seawalls, groins are perpendicular to the shore. Groins are usually made of concrete, wood, or rock. They often look like piers, and people can walk or even fish on them. Groins are usually built in groups, designed to protect the groin fields, or shoreline between them.
Term Part of Speech Definition Encyclopedic Entry agriculture Noun
the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).
Encyclopedic Entry: agriculture anchor Verb
to hold firmly in place.
small food fish.
type of popular game fish, found in both ocean and freshwater environments.
body of water partially surrounded by land, usually with a wide mouth to a larger body of water.
Encyclopedic Entry: bay biodiversity Noun
all the different kinds of living organisms within a given area.
Encyclopedic Entry: biodiversity breakwater Noun
a manmade wall rising from the sea floor that protects a harbor or beach from the force of waves.
goods carried by a ship, plane, or other vehicle.
edge of land along the sea or other large body of water.
Encyclopedic Entry: coast concrete Noun
hard building material made from mixing cement with rock and water.
construction or preparation of land for housing, industry, or agriculture.
to bring and secure a ship or boat to a space or facility.
to remove sand, silt, or other material from the bottom of a body of water.
having to do with money.
community and interactions of living and nonliving things in an area.
Encyclopedic Entry: ecosystem enhance Verb
to add to or increase in worth.
act in which earth is worn away, often by water, wind, or ice.
Encyclopedic Entry: erosion expand Verb
able to produce crops or sustain agriculture.
filter feeder Noun
aquatic animal that strains nutrients from water.
industry or occupation of harvesting fish, either in the wild or through aquaculture.
overflow of a body of water onto land.
Encyclopedic Entry: flood food web Noun
all related food chains in an ecosystem. Also called a food cycle.
Encyclopedic Entry: food web freshwater Noun
water that is not salty.
fringe marsh Noun
wetland area between a swamp or tidal marsh and dry land.
large structure that extends out from a shoreline, built to prevent erosion.
groin field Noun
area of protected shoreline between groins, or large structures that extend from the shoreline.
environment where an organism lives throughout the year or for shorter periods of time.
Encyclopedic Entry: habitat harbor Noun
part of a body of water deep enough for ships to dock.
Encyclopedic Entry: harbor hectare Noun
unit of measure equal to 2.47 acres, or 10,000 square meters.
large public road.
tropical storm with wind speeds of at least 119 kilometers (74 miles) per hour. Hurricanes are the same thing as typhoons, but usually located in the Atlantic Ocean region.
animal without a spine.
living shoreline Noun
method of creating coastal land by using stones and marine grasses to trap soil, sand, and mud.
Encyclopedic Entry: living shoreline mangrove Noun
type of tree or shrub with long, thick roots that grows in salty water.
to move from one place or activity to another.
tiny plant usually found in moist, shady areas.
substance an organism needs for energy, growth, and life.
Encyclopedic Entry: nutrient oyster Noun
type of marine animal (mollusk).
constant or lasting forever.
at a right angle to something.
platform built from the shore and extending over water.
organism that produces its own food through photosynthesis and whose cells have walls.
chemical or other substance that harms a natural resource.
place on a body of water where ships can tie up or dock and load and unload cargo.
Encyclopedic Entry: port predator Noun
animal that hunts other animals for food.
animal that is hunted and eaten by other animals.
having to do with activities done for enjoyment.
grass with tall, strong stalks that grows in marshy ecosystems.
to return something to its former status or quality.
structure placed directly on a river bank or shoreline to prevent erosion.
blocks of broken or uncut stone or concrete, placed along river banks or coastal areas to prevent erosion.
river bank Noun
raised edges of land on the side of a river.
overflow of fluid from a farm or industrial factory.
Encyclopedic Entry: runoff salt marsh Noun
coastal wetland that is flooded with seawater, often by tides.
small, loose grains of disintegrated rocks.
underwater or low-lying mound of sand formed by tides, waves, or currents.
type of plant that grows in the ocean.
barrier built to protect a beach or shoreline from erosion. Also called a bulkhead.
grass-like plant native to wetlands.
freestanding structures made of stone, sand, or other material placed close offshore to reduce the power of incoming waves.
top layer of the Earth's surface where plants can grow.
able to absorb and hold liquid.
sport fishing Noun
catching fish for competition or recreation.
structure made of stone, sand, or other material to reduce the power of incoming waves, connected to a coastline or other structure.
storm surge Noun
abnormal rise in sea level accompanying a hurricane or other intense storm. Also called a storm tide.
Encyclopedic Entry: storm surge support structure Noun
material that helps a natural or manmade object perform a function.
land permanently saturated with water and sometimes covered with it.
Encyclopedic Entry: swamp tidal marsh Noun
wetland that is regularly flooded by ocean tides.
movement of people or goods from one place to another.
tropical storm with wind speeds of at least 74 miles (119 kilometers) per hour. Typhoons are the same thing as hurricanes, but usually located in the Pacific or Indian Ocean region.
urban area Noun
developed, densely populated area where most inhabitants have nonagricultural jobs.
Encyclopedic Entry: urban area vegetation Noun
all the plant life of a specific place.
body of water that serves as a route for transportation.
moving swell on the surface of water.
state of the atmosphere, including temperature, atmospheric pressure, wind, humidity, precipitation, and cloudiness.
Encyclopedic Entry: weather wetland Noun
area of land covered by shallow water or saturated by water.
Encyclopedic Entry: wetland