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Scrap-heaps and coral-reefs: The challenges of artificial reef restoration

Author: Jones, E. M.

During a trip to Indonesia last year, I encountered my first artificial reef. It came as a stark contrast to my previous, cossetted experiences of ‘typical’ reef ecosystems. Established 5 years prior to my visit, the artificial reef looked like the aftermath of a battlefield. I snorkeled above rows of twisted metal pylons, cinder blocks laced with chicken wire, and branching corals cable-tied to meshed bricks. This reef consisted of the hardiest corals, some barely attached to their blocks, and very low diversity of fish to tend them. Rabbit fish dominated the artificial, descending on mats of gelatinous algae in feeding frenzies. A few tiny reef fish sheltered in the branching corals, diminutive splashes of color against a backdrop of dull green and brown. I could not help but leave that artificial reef site feeling disappointed and concerned. Was this just a one-off example of a struggling restoration site, or was this one of many? What is the current state of coral reef restoration and is it working?


The primary method that gave rise to reef restoration has its origins in ship wrecks (Roberts 2012). Wrecks are popular for both recreational divers and fishers (Brickhill et al. 2005). However, wrecks are not permanent and they eventually break down into nothing (Goreau & Hilbertz 2012). Even the famous Titanic is disintegrating away and is predicted to be reduced to scattered debris soon (Salazar & Little 2017).

A shipwreck colonized by reef organisms. Obtained from: https://goo.gl/L8shJ4


Nevertheless, it was during the 70s and 80s that artificial reefs began receiving greater attention for recreational use (Bohnsack et al. 1985). This was due to the way fish aggregate around them, similarly to wrecks (Bohnsack et al. 1985). To this end, artificial reefs also became regarded as restoration for over-dredged areas and as mediation for heavily degraded reefs (Rinkevich 2005). However, anything from household appliances to retired military tanks are dropped into the water for restoration purposes and this method is often hit-or-miss (Outdoor Alabama 2009; Na et al. 2016). For example, the Osborne Reef restoration effort was implemented in the early 1970s for a degraded coral reef on the coast of Fort Lauderdale, Florida. Nearly 2 million rubber tires were bound together and released as an artificial reef. The tires broke free of bindings during a storm and ended up scattering along the coast. This ended up damaging the degraded reef further, resulting in the need for wide-scale tire removal which far exceeded costs for the original Osborne Reef restoration project (Cabral & Primeau 2015). While recreating a three-dimensional environment is necessary for coral reef restoration, there must be a better way forward than using such items to restore reefs.

Currently coral reef restoration has evolved to include transplants and coral attachments on a hard substrate with the hope that the coral will grow, attract other species and create a functioning environment (Bowden-Kerby 2001; Rinkevich 2005). However, attaching corals to cinder blocks is often not effective in such a complicated and sensitive marine ecosystem (Baums 2008). For example, often crustose coralline algae need to grow on a substrate which then promotes coral recruitment (Goreau & Hilbertz 2012). Likewise, some species of coral, typically branching corals, grow better than others and therefore are often the ‘go-to’ species for restoration (Lindahl 2003; Johnson et al. 2011). Success can exist in the short term due to the fast growth rates and hardy nature of branching corals (Shafir et al. 2006). However, using one type of coral may arguably result in an inferior ecosystem that is low in biodiversity and resilience (Pearson 1981).

Alternatively, a recent technological advancement in restoration has been gaining ground in the form of ‘biorocks’ (van Treeck & Schuhmacher 1999). Sending weak electrical pulses through metal domes imitates growth of coralline algae, through a method called ‘electrolysis’ can facilitate coral growth (Goreau & Hilbertz 2012). These ‘electrolysis’-based restoration projects are gaining popularity and use world-wide and has seen higher growth rates and survival of coral (Goreau & Hilbertz 2005). Therefore, perhaps it is not all bad news for coral reef restoration; there are some existing projects that have seen success. However, again, it seems to be a hit-or-miss situation with coral recruitment. Some are successful, yet some fail to restore any coral but branching species where plate and massive coral often struggle to survive (Rinkevich 2005; Johnson et al. 2011). However, the water column contains an important and often overlooked factor that has a profound effect on successful coral reef restoration; the water itself.

An electric biorock facilitating coral growth. Obtained from: https://goo.gl/s0lqgL

Currents have a large part to play in coral reef ecosystem function. They bring in nutrients, recruits, and they bring in offshore pollution (Connell 2007). Restoration must consider all aspects of coral reef ecosystems which might have detrimental impacts on future success (De’ath & Fabricius 2010). This is because coral reefs are susceptible to pollution as it can smother the coral, prevent photosynthesis and facilitate algal growth over the coral (Wiedenmann et al. 2013). Pollution from offshore currents has a part to play in the decline in coral cover and bleaching mortality (Glynn 1993). And this is where it comes to a stalemate. If reef restoration is to see more success, the entire ecosystem needs to be considered (Mumby & Steneck 2008). A reef may be irrevocably doomed due to the external environment, no matter how many biorocks are submerged. Therefore, this is the challenge for reef restoration, one that involves going beyond the placement of coral reef gardens.

Many studies have shown that it is not enough to place some concrete blocks and wires in the water, leave them at the degraded site and then return in five or ten years and expect to see a successful project. Restoration projects may be unsuccessful if they consist of inadequate infrastructure or if more widespread issues such as pollution and climate change degrade them anyway. It is difficult to predict what I would see if I returned to explore that restoration site twenty years from now. I want to see it succeed. Maybe it will not be the idyllic coral ecosystems I had once envisioned, but restored enough to survive. I just hope I will not see a dull world of slime-coated metal pylons like bones jutting from the sea floor where once a restoration project struggled and failed. However, there is still hope for coral reef restoration. It just deserves greater planning, careful implementation, and new technology formatted to suit coral reef ecosystems.


Baums, I. B. (2008). A restoration genetics guide for coral reef conservation. Molecular ecology, 17(12), 2796-2811.

Bohnsack, J. A., & Sutherland, D. L. (1985). Artificial reef research: a review with recommendations for future priorities. Bulletin of marine science, 37(1), 11-39.

Bowden-Kerby, A. (2001). Low-tech coral reef restoration methods modeled after natural fragmentation processes. Bulletin of Marine Science, 69(2), 915-931.

Brickhill, M. J., Lee, S. Y., & Connolly, R. M. (2005). Fishes associated with artificial reefs: attributing changes to attraction or production using novel approaches. Journal of Fish Biology, 67(sB), 53-71.

Cabral, R., & Primeau, R. (2015). Reef Re-creation.

Connell, S. D. (2007). Water quality and the loss of coral reefs and kelp forests: alternative states and the influence of fishing. Marine ecology. Oxford University Press, Melbourne, 556-568.

De’ath, G., & Fabricius, K. (2010). Water quality as a regional driver of coral biodiversity and macroalgae on the Great Barrier Reef. Ecological Applications, 20(3), 840-850.

Glynn, P. W. (1993). Coral reef bleaching: ecological perspectives. Coral reefs, 12(1), 1-17.

Goreau, T. J., & Hilbertz, W. (2005). Marine ecosystem restoration: costs and benefits for coral reefs. World resource review, 17(3), 375-409.

Goreau, T. J., & Hilbertz, W. (2012). Reef Restoration using seawater electrolysis in Jamaica. Innovative Methods of Marine Ecosystem Restoration, CRC Press, Boca Raton, 35-45.

Johnson, M. E., Lustic, C., Bartels, E., Baums, I. B., Gilliam, D. S., Larson, E. A., … & Schopmeyer, S. (2011). Caribbean Acropora restoration guide: best practices for propagation and population enhancement.

Lindahl, U. (2003). Coral reef rehabilitation through transplantation of staghorn corals: effects of artificial stabilization and mechanical damages. Coral reefs, 22(3), 217-223.

Mumby, P. J., & Steneck, R. S. (2008). Coral reef management and conservation in light of rapidly evolving ecological paradigms. Trends in ecology & evolution, 23(10), 555-563.

Na, W. B., Kim, D., & Woo, J. (2016). Artificial reef management–a decommissioning review. 2016 Structures World Congress (Structures16).

Outdoor Alabama’s: Alabama’s Artificial Reefs A Fishing Information Guide (2009). Marine Resources Division. goo.gl/4iqgOn (accessed March 27, 2017)

Rinkevich, B. (2005). Conservation of coral reefs through active restoration measures: recent approaches and last decade progress. Environmental Science & Technology, 39(12), 4333-4342.

Rinkevich, B. (2005). Conservation of coral reefs through active restoration measures: recent approaches and last decade progress. Environmental Science & Technology, 39(12), 4333-4342.

Roberts, C. (2012). Ocean of life. Penguin UK.

Salazar, M., & Little, B. (2017) Review: Rusticle Formation on the RMS Titanic and the Potential Influence of Oceanography. Journal of Maritime Archaeology, 1-8.

Shafir, S., Van Rijn, J., & Rinkevich, B. (2006). Steps in the construction of underwater coral nursery, an essential component in reef restoration acts. Marine Biology, 149(3), 679-687.

van Treeck, P., & Schuhmacher, H. (1999). Artificial reefs created by electrolysis and coral transplantation: an approach ensuring the compatibility of environmental protection and diving tourism. Estuarine, Coastal and Shelf Science, 49, 75-81.

Wiedenmann, J., D’Angelo, C., Smith, E. G., Hunt, A. N., Legiret, F. E., Postle, A. D., & Achterberg, E. P. (2013). Nutrient enrichment can increase the susceptibility of reef corals to bleaching. Nature Climate Change, 3(2), 160-164.


Restoring resilience: Can restoring coasts with ecosystem-based solutions protect social-ecological systems from the impacts of climate change?

By Anni Brumby

Victoria University of Wellington



The destruction of hurricane Katrina in New Orleans in 2005 (Photo 1), extreme flooding on the east coast of Australia in 2007, and last year, my local train station in Porirua completely underwater. Welcome to the stormy and wet world of global climate change.

Photo 1. Two men paddle in high water in New Orleans after Hurricane Katrina. Getty Images.

Many of the threats caused by climate change are especially severe in coastal and low lying areas (Nicholls et al., 2007). This is a major concern, as coasts all over the planet are densely populated. Coastal areas less than 10 metres above sea level cover only 2% of the Earth’s surface, but contain 13% of the world’s urban population (McGranahan, Balk, & Anderson, 2007). Often coasts are highly modified for human purposes, and crucial for economic stability (Martínez et al., 2007).

The observed and predicted coastal hazards include sea level rise and the resulting inundation; erosion and salinization of land (Gornitz, 1991); increased precipitation intensity and run-off; and storm flooding (Nicholls & Lowe, 2004). Climate change will also increase the frequency and intensity of weather extremes, such as hurricanes (Emanuel, 2005; Seabloom, Ruggiero, Hacker, Mull, & Zarnetske, 2013).

The existence of Homo sapiens rely on ecosystem services – “the benefits people obtain from ecosystems” (Millennium Ecosystem Assessment, 2005, p. 1), such as food production, raw materials, waste treatment, disturbance and climate regulation, water supply and regulation…The list goes on. Coastal ecosystems contribute 77% of global ecosystem-services value (Martínez et al., 2007), thus any coastal threats affect have major impacts for humans both economically and socially.

It is unlikely that we can stop global warming (Peters et al., 2013), but is there any way to mitigate the risks? Even if we cannot prevent the sea levels from rising or storms raging, maybe we can protect our coastal ecosystems and cities by restoring resilience in social-ecological systems with ecosystem based defence strategies.


Concept of resilience

Resilience was first introduced as an ecological concept by Holling in 1973, the idea mainly referring to dynamic ecosystems that can persist in the face of disturbances. High ecological resilience is closely linked to high biodiversity of ecosystems (e.g. Oliver et al., 2015; Worm et al., 2006). As people are increasingly seen as an integral part of the biophysical world (Egan, Hjerpe & Abrams, 2011), our current understanding of resilience now also includes the human dimension. According to one definition, resilience is the capacity of social-ecological system to sustain a desired set of ecosystem services in the face of disturbance and ongoing evolution and change (Biggs et al., 2012, p. 423).


From human-engineered to ecosystem based defences

For a long time, coastal hazard prevention relied solely on so called  “hard solutions”, such as building of sea walls and dykes (Slobbe et al., 2013). Recently there has been a shift towards “softer” approaches. These so called ecosystem-based adaptation or defence strategies aim to conserve or restore naturally resilient coastal ecosystems, such as marshes and mangroves, in order to protect human population from natural hazards (Temmerman et al., 2013). Restoring shores for protection is not a new idea, but it has gained momentum in recent years. Many volunteer groups are focused on restoring coastal ecosystems, such as the Dune Restoration Trust in New Zealand. Globally, the influential Nature Conservancy funds a project called Coastal Resilience, which aims to reduce coastal risks to communities with nature-based solutions (Coastal Resilience, 2016).

Restoring dune vegetation can help reduce erosion, while increasing and maintaining the resilience of coastal zones (Silva, Martínez, Odériz, Mendoza, & Feagin, 2016). Coastal ecosystems, for example forested wetlands and marshes, can play a significant role in reducing the influence of waves (Fig. 1) and floods (Danielsen et al., 2005; Hey & Philippi, 1995; Mitsch & Gosselink, 2000; Seabloom et al., 2013). In southeast India coastal zones with intact mangrove forests and tree shelterbelts were significantly less affected by the catastrophic Boxing Day tsunami in 2004, than the areas where coastal vegetation had been removed (Danielsen et al., 2005). Coastal vegetation can also buffer gradual phenomena such as sea-level rise or tidal changes (Feagin et al., 2009).


Figure 1. A simple figure showing how the wave impact is reduced in healthy coastal habitats due to the buffering effect of different coastal ecosystems, such as marshes. The Nature Conservancy.

One of the benefits of ecosystem-based strategies compared to traditional human-engineered solutions is that they are more cost-efficient. For example, investment of US$1.1 million on mangrove restoration to protect rice fields in coastal Vietnam has been estimated to save US$7.3 million per year in dyke maintenance (Reid & Huq, 2005). In addition, almost 8,000 local families have been able to improve their livelihoods and thus their resilience by harvesting marine products in the replanted mangrove areas (Reid & Huq, 2005).

It has been argued that healthy natural ecosystems are more effective than man-made structures in coastal protection (Costanza, Mitsch, & Day, 2006). For example, the devastating effects of the 2005 flood in New Orleans could partially have been avoided, if the wetlands surrounding the city had not been modified by humans, thus preventing the delta system absorbing changes in water flows (Costanza et al., 2006). The problem is, due to anthropogenic stressors, not many coastal habitats are healthy or in a natural state. This is something that restoration aims to change, but to really make a difference, we have a long road ahead.



Significant mitigation of greenhouse gas emissions is the most crucial action that can be taken to reduce the effects of climate change, but we also need to adapt to the predicted changes by increasing ecosystem management methods sensitive to resilience (Tompkins & Adger, 2004). Traditionally, ecological restoration is based on the idea that we want to return something to its former condition. But ecosystems are not stable or static, never have been, and never will be (Willis & Birks, 2006). The increased risk of climate change induced coastal hazards possesses a major challenge to New Zealand economically, socially and environmentally. We have approximately 18,200 kilometres of shoreline, and one of the highest coast to land area ratios in the world. Most of New Zealand’s towns and cities, including our capital city Wellington, are located by the sea. In order to survive, we need to embrace ecosystem-based solutions and aim to restore for resilience.



Biggs, R., Schluter, M., Biggs, D., Bohensky, E. L., BurnSilver, S., Cundill, G., . . . West, P. C. (2012). Toward Principles for Enhancing the Resilience of Ecosystem Services. In A. Gadgil & D. M. Liverman (Eds.), Annual Review of Environment and Resources, Vol 37 (Vol. 37, pp. 421-+). Palo Alto: Annual Reviews

Coastal resilience. (2016). http://coastalresilience.org/ [Accessed on 22 April 2016].

Costanza, R., Mitsch, W. J., & Day, J. W. (2006). A new vision for New Orleans and the Mississippi delta: applying ecological economics and ecological engineering. Frontiers in Ecology and the Environment, 4(9), 465-472. doi:10.1890/1540-9295(2006)4[465:ANVFNO]2.0.CO;2

Danielsen, F., Sørensen, M. K., Olwig, M. F., Selvam, V., Parish, F., Burgess, N. D., . . . Suryadiputra, N. (2005). The Asian Tsunami: A Protective Role for Coastal Vegetation. Science, 310(5748), 643-643.  Retrieved from http://science.sciencemag.org/content/310/5748/643.abstract

Egan, D., Hjerpe, E. E., & Abrams, J. (2011). Why people matter in ecological restoration. In Human Dimensions of Ecological Restoration (pp. 1-19). Island Press/Center for Resource Economics

Emanuel, K. (2005). Increasing destructiveness of tropical cyclones over the past 30 years. Nature, 436(7051), 686-688. doi:http://www.nature.com/nature/journal/v436/n7051/suppinfo/nature03906_S1.html

Feagin, R. A., Lozada-Bernard, S. M., Ravens, T. M., Möller, I., Yeager, K. M., & Baird, A. H. (2009). Does vegetation prevent wave erosion of salt marsh edges? Proceedings of the National Academy of Sciences, 106(25), 10109-10113.

Gornitz, V. (1991). Global coastal hazards from future sea level rise. Palaeogeography, Palaeoclimatology. Palaeoecology 89(4): 379–398

Hey, D. L., & Philippi, N. S. (1995). Flood Reduction through Wetland Restoration: The Upper Mississippi River Basin as a Case History. Restoration Ecology, 3(1), 4-17. doi:10.1111/j.1526-100X.1995.tb00070.x

Holling, C. S. (1973). Resilience and Stability of Ecological Systems. Annual Review of Ecology and Systematics, 4, 1-23.  Retrieved from http://www.jstor.org.helicon.vuw.ac.nz/stable/2096802

Martínez, M. L., Intralawan, A., Vázquez, G., Pérez-Maqueo, O., Sutton, P., & Landgrave, R. (2007). The coasts of our world: Ecological, economic and social importance. Ecological Economics, 63(2–3), 254-272. doi:http://dx.doi.org/10.1016/j.ecolecon.2006.10.022

McGranahan, G., Balk, D., & Anderson, B. (2007). The rising tide: assessing the risks of climate change and human settlements in low elevation coastal zones. Environment and urbanization, 19(1), 17-37.

Millennium Ecosystem Assessment. (2005). Ecosystems and Human Well-being: Biodiversity Synthesis. World Resources Institute, Washington, DC

Mitsch, W. J., & Gosselink, J. G. (2000). The value of wetlands: importance of scale and landscape setting. Ecological Economics, 35(1), 25-33. doi:http://dx.doi.org/10.1016/S0921-8009(00)00165-8

Nicholls, R. J., & Lowe, J. A. (2004). Benefits of mitigation of climate change for coastal areas. Global Environmental Change, 14(3), 229-244. doi:http://dx.doi.org/10.1016/j.gloenvcha.2004.04.005

Nicholls, R.J., P.P. Wong, V.R. Burkett, J.O. Codignotto, J.E. Hay, R.F. McLean, S. Ragoonaden and C.D. Woodroffe. (2007). Coastal systems and low-lying areas. Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, M.L. Parry, O.F. Canziani, J.P. Palutikof, P.J. van der Linden and C.E. Hanson, Eds., Cambridge University Press, Cambridge, UK, 315-356.

Oliver, T. H., Heard, M. S., Isaac, N. J., Roy, D. B., Procter, D., Eigenbrod, F., . . . Petchey, O. L. (2015). Biodiversity and resilience of ecosystem functions. Trends in Ecology & Evolution, 30(11), 673-684.

Peters, G. P., Andrew, R. M., Boden, T., Canadell, J. G., Ciais, P., Le Quere, C., . . . Wilson, C. (2013). The challenge to keep global warming below 2 [deg]C. Nature Clim. Change, 3(1), 4-6. doi:http://www.nature.com/nclimate/journal/v3/n1/abs/nclimate1783.html#supplementary-information

Reid, H., & Huq, S. (2005). Climate change-biodiversity and livelihood impacts. Tropical forests and adaptation to climate change, 57.

Seabloom, E. W., Ruggiero, P., Hacker, S. D., Mull, J., & Zarnetske, P. (2013). Invasive grasses, climate change, and exposure to storm-wave overtopping in coastal dune ecosystems. Global Change Biology, 19(3), 824-832. doi:10.1111/gcb.12078

Silva, R., Martínez, M. L., Odériz, I., Mendoza, E., & Feagin, R. A. (2016). Response of vegetated dune–beach systems to storm conditions. Coastal Engineering, 109, 53-62. doi:http://dx.doi.org/10.1016/j.coastaleng.2015.12.007

Slobbe, E., Vriend, H. J., Aarninkhof, S., Lulofs, K., Vries, M., & Dircke, P. (2013). Building with Nature: in search of resilient storm surge protection strategies. Natural Hazards, 66(3), 1461-1480. doi:10.1007/s11069-013-0612-3

Temmerman, S., Meire, P., Bouma, T. J., Herman, P. M. J., Ysebaert, T., & De Vriend, H. J. (2013). Ecosystem-based coastal defence in the face of global change. Nature, 504(7478), 79-83. doi:10.1038/nature12859

Tompkins, E. L., & Adger, W. N. (2004). Does Adaptive Management of Natural Resources Enhance Resilience to Climate Change? Ecology and Society, 9(2).  Retrieved from http://www.ecologyandsociety.org/vol9/iss2/art10/

Willis, K. J., & Birks, H. J. B. (2006). What is natural? The need for a long-term perspective in biodiversity conservation. Science, 314(5803), 1261-1265.

Worm, B., Barbier, E.B., Beaumont, N., Duffy, J.E., Folke, C., Halpern, B.S., Jackson, J.B., Lotze, H.K., Micheli, F., Palumbi, S.R. and Sala, E., (2006). Impacts of biodiversity loss on ocean ecosystem services. Science, 314(5800), pp.787-790.