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Oyster breakwater reefs support climate adaptation

Bangladesh Kutubdia Island, located on the southeast coast of Bangladesh

Oyster breakwater reefs promote adjacent mudflat stability and salt marsh growth in a monsoon-dominated subtropical coast. 

On Kutubdia Island off the coast of Bangladesh, three oyster reefs were constructed on tidal mud flats using precast concrete rings. These reefs were deployed parallel to the coastline to serve as wave-break structures by attenuating wave energy. The concrete rings were first allowed to be colonized by oyster larvae and other marine organisms such as barnacles, sea anemones and gastropods for two years, before being deployed to their final location. The intervention primarily addresses the challenges of disaster risk reduction and climate change adaptation by dissipating wave energy and acting as breakwaters for tidal water. This intervention showed that breakwater oyster reefs can help reduce erosion, trap suspended sediment, and support seaward saltmarsh expansion, demonstrating their potential as a credible nature-based solution for protecting subtropical coastlines.

Case effectiveness on

Climate change

Mitigation: Not reported
Adaptation: Positive

According to a peer-reviewed study, oyster breakwater reefs were found to reduce disaster risk and contribute to climate change adaptation through attenuating wave energy and reducing coastal erosion. For tidal water levels between 0.5–1.0 meters, the reefs dissipated wave energy effectively and acted as breakwaters. For water levels less than 0.5 meters, waves were completely blocked by the vertical relief of the reefs. Furthermore, the study found that erosion was reduced by 54% in sites with the oyster breakwater reefs, compared to control sites. Lastly, a significant seaward salt marsh expansion was reportedly observed at the intervention site, whereas the salt marsh seaward margin retreated at the control sites.

Ecosystem health

Ecological effect: Positive

In addition to their potential for stabilizing tidal mud flats, oyster breakwater reefs are also useful for restoring or enhancing other ecosystems such as salt marshes, as evidenced in this case by the reported seaward salt marsh expansion, likely offering favorable conditions and habitat for coastal marine organisms.

Socioeconomic outcomes

We are currently working on adding the case effectiveness on socioeconomics.