Encyclopedic Entry

Aquatic plants are an essential part of most living shorelines.

Photograph by James P. Blair

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

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.

 

Protection

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.

 

Vocabulary

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.

anchovy

Noun

small food fish.

bass

Noun

type of popular game fish, found in both ocean and freshwater environments.

bay

Noun

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.

cargo

Noun

goods carried by a ship, plane, or other vehicle.

cattail

Noun

aquatic plant.

coast

Noun

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.

cordgrass

Noun

aquatic plant.

devastate

Verb

to destroy.

development

Noun

construction or preparation of land for housing, industry, or agriculture.

dock

Verb

to bring and secure a ship or boat to a space or facility.

dredge

Verb

to remove sand, silt, or other material from the bottom of a body of water.

economic

Adjective

having to do with money.

ecosystem

Noun

community and interactions of living and nonliving things in an area.

Encyclopedic Entry: ecosystem

enhance

Verb

to add to or increase in worth.

erosion

Noun

act in which earth is worn away, often by water, wind, or ice.

Encyclopedic Entry: erosion

expand

Verb

to grow.

fertile

Adjective

able to produce crops or sustain agriculture.

filter feeder

Noun

aquatic animal that strains nutrients from water.

fishery

Noun

industry or occupation of harvesting fish, either in the wild or through aquaculture.

flood

Noun

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.

groin

Noun

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.

habitat

Noun

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.

highway

Noun

large public road.

hurricane

Noun

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.

invertebrate

Noun

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.

migrate

Verb

to move from one place or activity to another.

moss

Noun

tiny plant usually found in moist, shady areas.

nutrient

Noun

substance an organism needs for energy, growth, and life.

Encyclopedic Entry: nutrient

oyster

Noun

type of marine animal (mollusk).

permanent

Adjective

constant or lasting forever.

perpendicular

Noun

at a right angle to something.

pier

Noun

platform built from the shore and extending over water.

plant

Noun

organism that produces its own food through photosynthesis and whose cells have walls.

pollutant

Noun

chemical or other substance that harms a natural resource.

port

Noun

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.

prey

Noun

animal that is hunted and eaten by other animals.

recreational

Adjective

having to do with activities done for enjoyment.

reed

Noun

grass with tall, strong stalks that grows in marshy ecosystems.

restore

Verb

to return something to its former status or quality.

revetment

Noun

structure placed directly on a river bank or shoreline to prevent erosion.

riprap

Noun

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.

runoff

Noun

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.

sand

Noun

small, loose grains of disintegrated rocks.

sandbar

Noun

underwater or low-lying mound of sand formed by tides, waves, or currents.

seagrass

Noun

type of plant that grows in the ocean.

seawall

Noun

barrier built to protect a beach or shoreline from erosion. Also called a bulkhead.

sedge

Noun

grass-like plant native to wetlands.

sill

Noun

freestanding structures made of stone, sand, or other material placed close offshore to reduce the power of incoming waves.

soil

Noun

top layer of the Earth's surface where plants can grow.

spongy

Adjective

able to absorb and hold liquid.

sport fishing

Noun

catching fish for competition or recreation.

spur

Noun

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.

swamp

Noun

land permanently saturated with water and sometimes covered with it.

Encyclopedic Entry: swamp

tidal marsh

Noun

wetland that is regularly flooded by ocean tides.

transportation

Noun

movement of people or goods from one place to another.

typhoon

Noun

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.

waterway

Noun

body of water that serves as a route for transportation.

wave

Noun

moving swell on the surface of water.

weather

Noun

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

Credits

Media Credits

The audio, illustrations, photos, and videos are credited beneath the media asset, except for promotional images, which generally link to another page that contains the media credit. The Rights Holder for media is the person or group credited.

Writers

Kim Rutledge
Melissa McDaniel
Diane Boudreau
Tara Ramroop
Santani Teng
Erin Sprout
Hilary Costa
Hilary Hall
Jeff Hunt

Illustrators

Tim Gunther
Mary Crooks, National Geographic Society

Editors

Kara West
Jeannie Evers

Educator Reviewer

Nancy Wynne

Producer

Caryl-Sue, National Geographic Society

Sources

Dunn, Margery G. (Editor). (1989, 1993). "Exploring Your World: The Adventure of Geography." Washington, D.C.: National Geographic Society.

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