Mangroves

Coastal mangrove forest in the area of the Sandy Island Oyster Bay Marine Protected Area (SIOBMPA) at Carriacou, Grenada. Sandy Island Oyster Bay Marine Protected Area, designed with the support of the Conservancy, was officially launched by Grenada in July 2010. The new reserve is one of three new marine protected areas the country will launch to help improve the management of the country’s marine resources and protect coastlines from errosion . Grenada and St. Vincent and the Grenadines are located at the Southern end of the Lesser Antilles. Photo Credit :Marjo Aho

Mangroves grow in the upper inter-tidal zone and are found predominantly in the warm coastal areas from the tropics to some warm temperate regions, where they can form extensive forests. Mangroves are highly productive ecosystems, especially in areas where freshwater from rivers or rainfall enhances growth. They provide critical coastal protection from waves and storms, habitat or nursery areas for fish and shellfish and support the lives and livelihoods of millions of people world-wide through the provision of food, timber and fuelwood.

While large areas of mangroves are being lost through coastal development and the expansion of aquaculture, several studies have shown that mangroves are natural coastal engineers. The following reports are available for download and show that around the globe, mangroves reduce wind swell and waves (click to download, reduce storm surge along coasts (click to download), and that mangrove surfaces are rising at similar rates to sea level rise (click to download) in a number of locations.

For more resources (reports on mangroves) visit the Coastal Resilience Resource Library on the Conservation Gateway

Coral Reefs

 

Limestone islands surround a sheltered lagoon where hard corals grow within centimeters of the low tide line. Wayag, Raja Ampat, Papua, Indonesia, Pacific Ocean. Photo credit: © Ethan Daniels

 

Coral reefs, shellfish reefs and some other hard physical structures built by corals, molluscs, worms or even algae, act like physical breakwaters, dampening the power and force of waves. Reefs face growing threats yet there is opportunity to guide adaptation and hazard mitigation investments towards reef restoration to strengthen this first line of coastal defense.

Coral reefs alone provide substantial protection against natural hazards by reducing the strength of waves. Experts estimate that approximately 100 million or more people around the world benefits from healthy coral reefs.  Studies show that coral reefs can provide comparable protection against harmful waves as artificial breakwaters (such as sea walls).  

For more resources (reports and journal articles) on coral reefs visit the Coastal Resilience Resource Library on the Conservation Gateway.

For more information about coral reef resilience, visit the Reef Resilience Network.

 

 

Oyster Reefs

 

TNC’s oyster reef restoration work along Jeremy Island in South Carolina. Photo credit: © Clay Bolt/TNC

TNC’s oyster reef restoration work along Jeremy Island in South Carolina. Photo credit: Clay Bolt

Oysters are filter feeders – they filter suspended particles (sediments, algae) out of the water column, leading to increased water clarity. Increasing water quality can enable more sea grass to grow providing more juvenile fish and crab habitat. Healthy oyster reefs filtering coastal waters could decreases number of harmful algae blooms, and associated fish kills and beach closures.

Oysters provide substrate in an otherwise flat world – oysters grow in 3-D reef structures that provide habitat for many other species including recreational and commercial fish, create nursery habitat for fish and crabs and can provide small animals shelter from larger predators. Reefs provide attachment points for other colonizing species which can be important food sources for fish, shrimp, and crabs.

Shellfish reefs are natural breakwaters that can stabilize shorelines, help to build wetlands, reducing runoff and the amount of suspended sediment in the water column, thus
increasing water quality.

For more resources (reports and journal articles) on the value of services provided to humans by oyster reefs visit the Oyster Goals Project on the Conservation Gateway.

Saltmarshes

Spoonbills and Woodstorks in saltmarsh wetlands, an important feeding ground for many coastal birds. Ossabaw Island, GA Photo credit: Kathy Knight

Spoonbills and Woodstorks in saltmarsh wetlands, an important feeding ground for many coastal birds. Ossabaw Island, GA Photo credit: Kathy Knight

Saltmarshes are widespread over vast stretches of low-energy coastlines and sheltered bays and estuaries. They are increasingly being described as important buffers between land and sea – binding sediments and reducing wave action.

For more resources (reports and journal articles) on salt marshes visit the Coastal Resilience Resource Library on the Conservation Gateway.

Seagrasses

Seagrasses are subtidal plants that can build large meadows. Their role in coastal protection is not always so well understood, but they appear to reduce sediment suspension and in some places they create deep tightly matted soils – capturing sediments and raising the elevation of the sea bed.
For more resources (reports and journal articles) on seagrasses visit the Coastal Resilience Resource Library on the Conservation Gateway.

Healthy Seagrass Bed in the Exuma Cays Land and Sea Park, Bahamas. The Nature Conservancy works closely with partners such as the Bahamas National Trust and the government of the Bahamas to protect the marine habitat of the Exuma Cays and achieve the goal for the long term protection of national parks through the Caribbean Challenge. PHOTO CREDIT: © Jeff Yonover