Sunken Worlds: The Past and Future of Human-Made Reefs in Marine Conservation

Abstract

Structures submerged in the sea by humans over millennia provide hard and longstanding evidence of anthropogenic influence in the marine environment. Many of these human-made reefs (HMRs) may provide opportunities for conservation despite having been created for different purposes such as fishing or tourism. In the middle of controversy around the costs and benefits of HMRs, a broad analysis of biodiversity and social values is necessary to assess conservation potential. This requires reframing HMRs as social–ecological systems, moving beyond comparisons with natural coral or rocky reefs to consider their roles as ecosystems in their own right; creating frameworks to track their type, number, size, units, location, characteristics, origins, social uses, and associated biodiversity locally and worldwide; and applying systematic assessment of conservation benefits in relation to stated conservation intentions. This integrative approach can catalyze learning, identify conservation opportunities, and inform positive management of HMRs into the future.

Global kelp forest restoration: past lessons, present status, and future directions

“…(5) Artificial reefs Artificial reefs are another common approach although they are used more often in afforestation than in restoration projects. While they are often not well documented, artificial reefs have an extensive history, and the materials used range from rocks, tram cars (Carlisle et al, 1964), bombs and ships (Tickell et al, 2019), to materials designed to enhance algal growth (Fujita et al, 2017). As discussed above, if artificial reefs are placed in habitats that did not contain kelp (e.g.…”

“…on a sandy substratum, as is common), the approach is considered afforestation as opposed to true habitat restoration. The use of artificial reefs for afforestation is common in Japan and Korea (Lee et al ., 2017) but faces greater resistance elsewhere (l'vfeier, 1989; Tickell et al ., 2019).…”

“…Most projects outside of Japan relied on wild harvest of kelp plants, whereas in Japan culture or breeding programs provided source plants, likely linked to the fact that Japan is one of the largest producers of seaweed in the world (Nayar & Bott, 2014) and can adapt seaweed farming technology. Similarly, it appears much more common for projects to deploy artificial substrates in Japan (Tokuda et al ., 1994), a practice that while also common in Korea, is often opposed in other countries (Thierry, 1988; Tickell, Sáenz‐Arroyo & Milner‐Gulland, 2019). The Japanese coastline is heavily urbanised and artificial reefs are often used to offset these developments.…”

Habitat type and environmental conditions influence the age and growth of a temperate marine damselfish

“…Estimates of total reproductive-energy output (i.e., combining fecundity, egg size, egg energy content) per spawn scaled hyperallometrically with body size for Garibaldi and other demersal spawning damselfish species, and therefore larger mothers contribute disproportionately to population replenishment (Barneche et al, 2018). The amount of human-built structures in the marine environment is expected to increase in the coming decades with the continued expansion of marine infrastructure associated with activities such as port construction, marine aquaculture, sea level rise adaptation, and marine renewable energy development (Tickell et al, 2019;Bugnot et al, 2020), and with the growing interest to design artificial reefs for reef habitat restoration and mitigation (e.g., Pondella et al, 2006;Reed et al, 2006;Pondella et al, 2018;Komyakova et al, 2019) and/or for fisheries enhancement (e.g., Polovina and Sakai, 1989;Santos et al, 2011;Roa-Ureta et al, 2019). Fish life history studies that compare ecological performance across habitat types, such as this one, are essential to inform the design and assessment of these future reefing projects.…”

Offshore Wind Farm Artificial Reefs Affect Ecosystem Structure and Functioning: A Synthesis

“…Artificial reefs are man-made structures (i.e., hard substrates) deliberately placed in the sea to mimic characteristics of natural reefs. The term "artificial reef " has been in the literature since the 1930s (Bohnsack and Sutherland, 1985), but structures aimed at promoting fisheries and aquaculture have been around for at least 5,000 years (Tickell et al, 2019). The most common purpose for deploying artificial reefs has been to improve biodiversity, particularly with respect to fishery species (Bohnsack and Sutherland, 1985).…”