Constructed Reefs / Living Breakwaters

  Living Breakwaters by SCAPE Landscape Architecture, Staten Island, NYC. Photo from Arch Daily.

Coral reefs support approximately one-quarter of marine biodiversity but also the livelihoods of tens of millions of people in coastal areas and more specifically are a crucial life support system for small island nations (Albright & Cooley, 2019. Constructed reefs have some of the same benefits, though take a long time to evolve. 

Constructed reefs, or artificial reefs and living breakwaters are innovative coastal engineering solutions designed to enhance coastal protection by altering wave forces, promote biodiversity, and support sustainable coastal management. They are located near or off shore where damage to existing reefs may exist. These kind of human-constructed reefs mimic natural reef habitats but are human-made structures on the ocean floor. Constructed reef may be completly submerged, while breakwaters can be above the surface of the water. 

Constructed reefs can be made from a variety of materials, including concrete, steel, rock, and recycled materials like sunken ships. Living breakwaters enhance coastal resilience while promoting biodiversity. Unlike traditional hard structures, such as seawalls, living breakwaters incorporate natural materials and living organisms. Both provide substrate for marine organisms to colonize, creating complex habitats that support biodiversity. They can help restore degraded habitats, such as coral reefs and oyster beds, by providing attachment surfaces for coral larvae and juvenile shellfish. Living breakwaters incorporate structures that emulate natural rock pools. See also: Living seawalls and biodiversity tiles.

Constructed reefs and living breakwaters, varying in design and positioning, play a pivotal role in mitigating wave energy and safeguarding shorelines against erosion and storm-induced harm. Similar to their natural counterparts, these engineered structures contribute to beach and coastal infrastructure stabilization by dissipating incoming wave energy. This reduction is achieved by intercepting waves before they reach the shore, thereby shielding beaches, dunes, and coastal infrastructure from erosive forces. Additionally, these reefs foster sheltered environments conducive to sediment accumulation, facilitating beach formation and maintenance over time.

With this, heavier storms have meant the degradation of the reefs due to erosion and damage caused by the high wave energy in the waters. The constructed reef can help restore the ecosystem and provide benefits to local people including food, income, recreation, coastal protection, cultural settings, and multiple other ecosystem services (Hoegh-Guldberg, O et al 2017).

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Name of NbS

Constructed Reefs / Living Breakwaters

Type of NbS

Engineered interventions; Hybrid living/engineered interventions

Location

Marine environments

Case Study

MARS-assisted reef restoration system (Great Barrier reef)

Living Breakwaters by SCAPE Landscape Architecture, Staten Island, NYC. Image from Dezeen.

Relationship to Indigenous knowledge

Constructed reefs or breakwaters do not seem to have precedence in Indigenous practice in Te Moananui Oceania. However, for local and Indigenous communities in Te Moananui Oceania, the ocean is ubiquitous and a fundamental part of cultural identity and livelihood (UNESCAP, 2019). Traditional ecological knowledge provides insights into the intricate dynamics of coastal ecosystems. Various types of traditional fish weirs and traps, fishponds and mariculture gardens, and some rock walls and terraces are evidence of traditional marine structures.

Florida Limestone Reef deployed off Mexico Beach, Florida, USA. Photo by Reefmaker.
Artificial Reef deployment Gulf of Mexico by Reefmaker. Photo by Reefmaker.
Climate change benefits
  • Changes in phenology
  • Coastal erosion
  • Coastal inundation and storm surge
  • Increased temperatures
  • Loss of food production
  • Ocean acidification
  • Sea level rise

Constructed reefs and breakwaters act as barriers that absorb and dissipate wave energy, thereby reducing the erosive forces on coastlines. By minimizing erosion, these structures help protect coastal habitats, infrastructure, and communities from the impacts of sea-level rise, storm surges, and increased storm intensity associated with climate change.

Healthy reef ecosystems sequester carbon dioxide from the atmosphere, helping to mitigate climate change by reducing greenhouse gas concentrations in the atmosphere. Coastal habitats such as mangroves, seagrass beds, and salt marshes are important blue carbon ecosystems that store large amounts of carbon in soil and biomass. Constructed reefs and breakwaters can help protect these coastal habitats from erosion and degradation, preserving their carbon sequestration potential. By safeguarding blue carbon ecosystems, these structures contribute to climate change mitigation efforts and support biodiversity conservation. 

Constructed reefs that mimic natural reef habitats provide shelter and habitat for marine organisms, including calcifying organisms such as corals, mollusks, and crustaceans. By restoring habitat for these organisms, constructed reefs can indirectly support their populations and contribute to maintaining biodiversity in the face of ocean acidification.

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Societal / socio-cultural benefits
  • Disaster risk reduction
  • Food security

Coral reefs play a crucial role in ecosystems, serving not only as sources of food for humans but also as vital protection against the rising threat of storm surges (Hoegh-Guldberg et al. 2017). Constructed reefs and breakwaters creating buffer zones that absorb and redirect wave energy, thereby reducing the risk of flooding and property damage during extreme weather events (Becker et al. 2018). By fortifying coastal defenses, these structures facilitate community adaptation to climate change, enhancing their ability to withstand future impacts.

Constructed reefs serve as habitats for diverse animal and coral species, providing essential resources such as food and medicine to local communities. This symbiotic relationship between ecosystems and humans underscores the multifaceted benefits of these structures in supporting both environmental and societal well-being.

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Ecological and biodiversity benefits
  • Disturbance prevention
  • education and knowledge
  • food production
  • habitat provision
  • medicinal resources

Coral reefs provide rich biodiversity, valuable ecosystem services and links to economic benefits. Constructed reefs, particularly those designed to mimic natural reef habitats, can serve as important sites for reef habitat restoration and biodiversity conservation over time. 

In studies comparing the ecological benefits of natural and artificial reefs, data illustrates that the density of the biomass and fish abundance on the artificial structures tends to be higher compared to that found in natural reef ecosystems (Bohnsack & Sutherland, 1985). Artificial reefs concentrate fish in areas as they are attracted to the algae and invertebrates that attach themselves to the structures (Becker et al. 2018).

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Reef star structure. Image by Mars coral reef restoration (2021)
Living Breakwaters by SCAPE Landscape Architecture, Staten Island, NYC. Photo from Dezeen.

Technical requirements

The successful implementation of constructed reefs and breakwaters demands specialised expertise spanning coastal engineering, marine ecology, and habitat restoration. Key technical considerations include the use of durable materials capable of withstanding wave action and currents. Constructed reefs and breakwaters can be damaged by storms, which are becoming more intense with climate change. This has destroyed reefs through corrosion in as little as 4 years in the past (Bohnsack & Sutherland, 1985).

Additionally, integration with natural systems is essential to ensure long-term sustainability, allowing the reefs to function effectively without extensive human intervention. Regular maintenance is crucial to monitor reef health and structural integrity, ensuring ongoing effectiveness in providing habitat and coastal protection.

Expanding the deployment of constructed reefs to additional locations further amplifies their benefits. By increasing coverage across a broader geographic area, more marine species can benefit from the additional habitat, while coastal communities gain enhanced protection against erosion and storm damage.

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Issues and Barriers

In Te Moananui Oceania, the adoption of constructed reefs and breakwaters encounters multifaceted challenges and barriers. One prominent issue is the scarcity of financial resources and funding avenues allocated to coastal protection initiatives amidst competing priorities. Navigating the intricate web of regulatory frameworks may pose another hurdle. Negotiating this bureaucratic landscape can be arduous, characterised by prolonged processes and escalated costs.

Alterations to water flow patterns, sediment transport dynamics, and habitat disruption are potential consequences of constructed reefs and breakwaters. Addressing these impacts requires comprehensive assessments and mitigation strategies to safeguard marine ecosystems and ecological balance.

Cultural apprehensions and community resistance further complicate matters. Opposition may arise due to apprehensions about impacts on traditional fishing grounds, cultural heritage sites, or scenic landscapes. Indigenous communities may express cultural objections rooted in ancestral ties to the land and sea, necessitating inclusive engagement and participatory decision-making processes to build consensus. 

Lastly, uncertainties surrounding climate change exacerbate the challenges. The long-term efficacy of constructed reefs and breakwaters in mitigating climate-related risks, such as sea-level rise and changing storm patterns, remains uncertain.

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Opportunities

By creating artificial habitats and enhancing existing ones, constructed reefs and breakwaters support marine biodiversity, restore degraded ecosystems, and preserve threatened species. Moreover, they stimulate economic growth by attracting tourists and recreational activities, enhancing fisheries productivity, and supporting aquaculture ventures.

Culturally, these initiatives provide avenues for community engagement, Indigenous knowledge integration, and cultural revitalisation, strengthening connections between coastal communities and their marine environments.

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Nassau, Bahamas. Photo by Mark Yokoyama
Artificial reef. Photo by PickPik

Financial case

By promoting ecosystem health and resilience, constructed reefs and breakwaters contribute to sustainable development and long-term economic prosperity in Te Moananui Oceania. While the initial investment in constructing reefs and breakwaters may be significant, the substantial economic returns, coupled with the social, cultural, and environmental benefits they provide, justify their cost-effectiveness for coastal management and climate resilience. Economic benefits are provided through fisheries, tourism and coastal protection (Raj et al. 2020).

Constructed reefs are often a cost-effective system to disperse and reduce wave energy attenuation compared to above-land structures (Beck et al., 2018). These structures offer long-term cost savings by mitigating the impacts of coastal erosion, storm surges, and sea-level rise, reducing the need for costly infrastructure repairs and emergency response measures. By stabilising shorelines and protecting coastal infrastructure, constructed reefs and breakwaters help safeguard valuable assets, including buildings, roads, and utilities, thereby minimising potential economic losses due to property damage and business disruption. 

They create sheltered areas where fish can feed, spawn, and seek refuge from predators, ultimately increasing fishery yields and supporting coastal economies (Becker et al. 2018).

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Constructed break water. Photo by Evelyn Simak.
Breakwater. Photo by Pok Rie.
References
  • Albright, R., & Cooley, S. (2019). A review of interventions proposed to abate impacts of ocean acidification on coral reefs. Regional Studies in Marine Science29, 100612.
  • Beck, M. W., Losada, I. J., Menéndez, P., Reguero, B. G., Díaz-Simal, P., & Fernández, F. (2018). The global flood protection savings provided by coral reefs. Nature communications9(1), 1-9.
  • Becker, A., Taylor, M. D., Folpp, H., & Lowry, M. B. (2018). Managing the development of artificial reef systems: The need for quantitative goals. Fish and Fisheries19(4), 740-752.
  • Bohnsack, J. A., & Sutherland, D. L. (1985). Artificial reef research: a review with recommendations for future priorities. Bulletin of marine science37(1), 11-39.
  • Hoegh-Guldberg, O., Poloczanska, E. S., Skirving, W., & Dove, S. (2017). Coral reef ecosystems under climate change and ocean acidification. Frontiers in Marine Science4, 158.
  • UNESCAP (2019). Ocean Cities Regional Policy Guide. Bangkok: UNESCAP.

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