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Nature-based Solutions

Coral Reef Systems and Seagrasses as Coastal Defense

The effects of natural hazards have become more prominent due to climate change. If not mitigated, it could result in disasters in the communities affected by it. Ecosystem-based Disaster Risk Reduction (Eco-DRR) is a means of preventing these disasters by utilizing a more sustainable approach that entails the restoration and conservation of the ecosystem to serve as protection against the impacts of climate change. An example of this is the use of coral reef systems and seagrasses as wave breakers and natural coastal defense mechanism [4].

Climate Adaptation Effectiveness

In order to determine the effectivity of Eco-DRR, wave model simulations were conducted on a coastal environment with an extensive reef system. In one scenario, monsoonal winds and storm conditions were simulated. As sea level rise is projected to continue in the incoming years, a scenario was also simulated to determine how the reef systems help in preventing disasters. In both simulations, it was observed that the reef systems significantly dissipated the wave energy which lessened the amount of water coming onto the coast [6]. Aside from coral reefs, seagrasses and mangroves also had similar effects to the wave energy [1][2].

Climate Hazards

  • Sea Level Rise
  • Tropical Cyclone


  • Barangay Bagacay and Barangay Rizal Municipality of Sorsogon, Sorsogon, Region V (Bicol Region)

Adaptation Sectors

  • Biodiversity
  • Coastal Areas
  • Disaster Risk Reduction
  • Ecosystem-Based Approaches
  • Marine and Fisheries

CCET Instuments

  • Action Delivery

Target Group based on Vulnerability

Basic Sectors:
  • Artisanal Fisherfolk
  • Children
  • Farmers and Landless Rural Workers
  • Indigenous Peoples
  • Persons with Disabilities
  • Senior Citizens
  • Women
  • Workers in the Informal Sector
  • Youth and Students


Economic / Financial Effectiveness

The information below shows the costs in utilizing defenses for coastal protection. In comparison to the engineering measures presented, coral reef restoration projects are a much cheaper means of coastal protection. The lifespan of seawalls and breakwaters are highly variable and dependent on the coastal environment, materials used, exposure to waves, and the design [1][5][6]. Seawall: USD 3.3- 18M per kilometer Breakwaters: USD 456-188,817 per meter Coral reef restoration: USD 20-155,000 per meter Coral reef restoration projects would also incur lower maintenance cost because the organism is capable of self-repair. However, reef restoration is relatively new and is suggested to be studied further [1].

Technical Feasibility

Reef systems provide a long-term solution for coastal protection if managed properly. As it is low cost and very effective, efforts are recommended to be channeled to the protection, restoration, and management of these coastal ecosystems. If resources are available, it is suggested that seawalls and other artificial structures be built to add protection against stronger and higher waves. This will add reinforcement to the primary protection provided by the reef systems [6].

Social Acceptability

Eco-DRR projects utilizing coral reefs, seagrass meadows, and mangrove forests are widely accepted as means for coastal defense and wave protection [6].

Environmental Impact
Mid (+)

The presence of coral reefs and seagrasses in coastal areas reduce soil erosion by limiting the strength of nearshore currents which promote the stability of the shoreline. Stable shorelines allow for mangroves to propagate, supplementing the coastal protection provided by the corals and seagrasses. All of these organisms also promote biodiversity by becoming habitat and temporary nurseries for other aquatic organisms [2]. Seawalls, on the other hand, could increase the rates of coastal erosion by inhibiting the natural transport of sediments on the shoreline. Components of the seawalls could also be eroded, introducing foreign material to the seas. Continuous erosion of the material would lead to the collapse of these structures [6].

Mitigation co-benefit

Seagrass and mangroves help mitigate climate change by absorbing large amounts of carbon dioxide from the atmosphere. Coral reefs and seagreasses often occur together in the tropics and it was found out that coral reefs aid in the ability of seagrasses to take in carbon input by acting as a barrier from erosion [3].


coral reefs, sea grasses, mangroves, seawalls, protection, strong waves, ecosystem-based disaster risk reduction


[1] Ferrario, F., Beck, M., Storlazzi, C., Micheli, F., Shepard, C., and Airoldi, L. (2014). The effectiveness of coral reefs for coastal hazard risk reduction and adaptation. Nature Communications, 5 (3794), pp. 1-9.
[2] Guannel, G., Arkema, K., Ruggiero, P., and Verutes, G. (2016). The Power of Three: Coral Reefs, Seagrasses and Mangroves Protect Coastal Regions and Increase Their Resilience. PLoS ONE 11(7).
[3] Guerra-Vargas, L,A., Gillis, L.G., and Mancera-Pineda, J.E. (2020) Stronger Together: Do Coral Reefs Enhance Seagrass Meadows “Blue Carbon” Potential? Front. Mar. Sci. 7.
[4] International Union for Conservation of Nature (IUCN). Eco-DRR: What are IUCN's solutions?
[5] University of Liverpool. Curbing the cruel sea. Published on: July 2009.
[6] Villanoy, C., David, L., Cabrera, O., Atrigenio, M., Siringan, F., Aliño, P., and Villaluz, M. (2012). Coral reef ecosystems protect shore from high-energy waves under climate change scenarios. Climatic Change, 112 (2), pp. 493-505.