Artificial Reefs: History, Environmental Impact, and the Attraction vs. Production Debate

Artificial reefs are human-created underwater structures primarily designed to attract marine life, prevent erosion, and, in recent years, support the local tourist industry by promoting diving or surfing spots. Such creations can take many forms; traditionally, they were created by employing construction debris and rubble. More recently, artificial reefs have also been made by scuttling old oil rigs and ships.

The practice is older than one might assume. Reports of artificial reefs blocking harbor entrances with construction material date back to the third century BCE during the First Punic War between Rome and Carthage. Less employed in maritime warfare and more to promote aquaculture, it was the Pacific that over the last millennium saw the creation of artificial catchments created out of debris or volcanic rock emerging to harvest kelp in Japan or fish and shellfish in the Philippines and the Hawaiian Islands. By the early nineteenth century, off the coast of the United States, logs were employed to attract schools of fish. The surplus, sinking, and subsequent dumping of military vehicles and naval vessels during and following the world wars led to such structures’ intentional and unintentional creation. In the following decades, the upsides and downsides of artificial reefs became more apparent.

By the end of the 1950s, as the dangers of overfishing, coastal erosion, and increasing damage to natural reefs became evident, the practice of reef restoration and creation spread worldwide. Some sources even derive the proliferation of these artificial phenomena from observations around large-scale battles in the Pacific following the Second World War. The congregation of fish around the sunken hulls invited local divers and fishermen, such as Japanese sunken ships in Chuuk Lagoon in Micronesia, inviting experiments in other areas. The practice also revealed a significant process of trial and error. Initial dumping of surplus material to avoid landfills, most prominently automotive tires, created more harm than benefits. The best example constitutes the expansion of the Osborne Reef off Fort Lauderdale. Initially constructed with concrete blocks, authorities decided to employ two million used tires for its expansion, hoping to combine recycling with creating or expanding artificial reefs. Many tires were loosely strung together through nylon or steel bands with little foresight on potential biomatter attachment or displacement by hurricanes. When tires became unfastened, they not only started to appear on beaches outside of Florida but also turned into projectiles, causing damage to existing natural reefs. Decades-long costly cleaning efforts involving armed forces resulted from such disasters. Additional environmental dangers emanated from the scuttling of ships and platforms where improperly prepared wrecks leaked toxins and remaining fossil fuels.

With over fifty years of experience, an overall assessment of artificial reefs reveals positive and negative impacts on the world’s oceans. On the positive side, artificial reefs absorb the growing pressures on natural resources from overfishing, expanding tourism, river spills, and general coastal erosion. Carefully engineered and controlled artificial reefs can add to existing natural ones and increase the absorption of greenhouse gases, so-called carbon sinks, around the globe. The need to monitor human-made structures also produces scientific research and associated employment. Careless dumping of rubble, rubber, or poorly recycled vehicles, as illustrated by the Osborne Reef, can cause much more harm than good by creating additional strains on an already-impacted ocean environment.

In addition, experts still debate the impact of such formation on fish populations. While only some individuals would contest that artificial reefs succeed in attracting fish and other marine species, some reports are less optimistic about the potential of encouraging the newcomers to propagate. Unlike natural reefs, the resulting attraction-versus-production arguments split experts on the basis that artificial structures can attract many different fish species but do not provide environments to encourage reproduction. To make matters worse, since the area around artificial reefs is often less protected from fishermen, the high concentration of certain fish species on these structures could result in additional overfishing. In other words, artificial reefs could concentrate endangered marine life in a location that is easier for commercial or recreational fishermen to access. An assessment of the attraction-versus-production debate remains difficult given that both sides rely on projection models and that more exact quantifiable data is difficult to obtain and hinges upon many different biological and sociological factors. A slow-emerging consensus, however, suggests that while newer artificial structures attract marine species as they age, attract more biomass, and start to resemble their natural counterpart, their usefulness as breeding environments (i.e., production) is increasing.

No matter whether artificial reefs are erected close to natural reefs or as stand-alone structures, their effectiveness and potential devastation on local marine environments demand constant monitoring and careful management. Rainer F. Buschmann

FURTHER READING:D’itri, Frank M. ed. 1985. Artificial Reefs: Marine and Freshwater Applications. Boca Raton, FL: CRS Press.

Bracho-Villaviencio, Carolina, Helena Matthews-Cascon, and Sergio Rossi. 2023. “Artificial Reefs Around the World: A Review of the State of the Art and a Meta-Analysis of its Effectiveness for the Restoration of Marine Ecosystems. Environments 10 (7). https://doi.org/10.3390/environ ments10070121. Accessed January 22, 2024.

Seaman, William. 2000. Artificial Reef Evaluation: With Applications to Natural Marine Habitats. Boca Raton, FL: CRS Press.