In This Article Expand or collapse the "in this article" section Ocean Sprawl

  • Introduction
  • General Overviews
  • Environmental Impacts of Ocean Sprawl
  • The Future of Ocean Sprawl

Ecology Ocean Sprawl
Louise Firth
  • LAST REVIEWED: 23 November 2021
  • LAST MODIFIED: 23 November 2021
  • DOI: 10.1093/obo/9780199830060-0237


Ocean sprawl is the proliferation of engineered artificial structures in coastal and offshore marine environments. These include ship hulls; infrastructure associated with land reclamation and urbanization (e.g., seawalls, bridges, floating docks); fisheries (artificial reefs, aquaculture installations); coastal defence structures (e.g., breakwaters, groynes); resource extraction (oil and gas rigs, renewable energy devices); and shipwrecks. Only fixed permanent and semipermanent structures are considered here and ship hulls are not included. Single structures can scale up with dramatic consequences for the local environment. Extreme examples of this include: the “New Great Wall” of China—seawalls enclosing coastal wetlands covering 60 percent of the total length of the Chinese coastline; “The World”, Dubai—an archipelago of over three hundred artificial islands constructed in the shape of a world map; and the “Steel Archipelago,” which describes more than four thousand oil and gas structures in the Gulf of Mexico. The placement of these fixed artificial structures modifies the local physical and chemical environment with cascading impacts on the composition, functioning, and service provision of surrounding species, habitats, and ecosystems. These structures also provide novel habitat which can offer surface for attachment, food, and protection for myriad marine species. They can act as fish aggregating devices, attracting fishing and other human activities. These structures may also have wide-reaching impacts through acting as barriers or conduits to ecological connectivity—the movement of organisms, materials, and energy between habitat units within seascapes. An improved understanding of the biological communities associated with artificial structures, coupled with the global drive for sustainable development, is driving an explosion of research into the design of multifunctional structures with built-in secondary ecological or socioeconomic benefits. Results to date have been promising but greater integration of the fields of ecology, engineering, and social sciences is necessary to better connect theory and practice in this emerging discipline.

General Overviews

The term “Ocean Sprawl” was first introduced by Carlos Duarte and collaborators in 2013. Duarte, et al. 2013 proposes that the proliferation of artificial structures associated with shipping, aquaculture, coastal protection, and other coastal industries provided habitat for benthic jellyfish polyps and may be an important driver of global increases in jellyfish blooms. The authors provide estimates of the annual growth rates and metric tons of a range of different activities that were responsible for ocean sprawl. Since then, Firth, et al. 2016 has provided a comprehensive descriptive review of a wide range of artificial structures in both coastal and offshore environments. Bugnot, et al. 2021 provides an inventory and forecast of the extent of ocean sprawl. This comprehensive assessment considers coastal structures such as ports, coastal defenses, land-reclamation areas, tunnels and bridges, artificial islands, recreational marinas, and artificial reefs, in addition to offshore structures such as hydrocarbon mining and associated pipelines, renewables, and power and telecoms cables. In recognition of the habitat potential of artificial structures, Keith, et al. 2020 includes a number of marine artificial structure types (submerged artificial structures, marine aquafarms, artificial shores) in the IUCN Global Ecosystem Typology 2.0. Gentry, et al. 2017 provides a major review of artificial structures associated with aquaculture; Lima, et al. 2019 reviews artificial reefs; Parente, et al. 2006 reviews oil and gas platforms; and Sengupta, et al. 2018 reviews urban coastal land reclamation. Eurosion 2004 provides a major large-scale regional assessment of the extent and nature of artificial and natural shorelines available for Europe, and National Oceanic and Atmospheric Administration (NOAA) 2012 does the same for the United States.

  • Bugnot, A. B., M. Mayer-Pinto, L. Airoldi, et al. 2021. Current and projected global extent of marine built structures. Nature Sustainability 4:33–41.

    DOI: 10.1038/s41893-020-00595-1

    The most up-to-date and complete assessment of the extent of ocean sprawl globally. Estimates are provided of the present (2018) and predicted (2028) area of physical footprint and modification of surrounding seascapes by different structure types. All original data sources are provided.

  • Duarte, C. M., K. A. Pitt, C. H. Lucas, et al. 2013. Is global ocean sprawl a cause of jellyfish blooms? Frontiers in Ecology and the Environment 11.2:91–97.

    DOI: 10.1890/110246

    This empirical paper coined the term “ocean sprawl.” It provides evidence that jellyfish larvae settle in large numbers on coastal artificial structures waters and develop into dense concentrations of jellyfish-producing polyps. The authors propose that ocean sprawl may be an important driver of the global increase in jellyfish blooms.

  • EUROSION. 2004. A European initiative for sustainable coastal erosion management. Reports Online.

    The Eurosion Project quantified the extent of erosion risk along the entire European coastline. Outputs include a final report, a geographic information system (GIS) database, and a Shoreline Management Guide. The reports include an inventory of coastal types (e.g., percent artificial coastline per country and percent natural features such as hard or soft rock, beach, and muddy coast) per country. All reports are available in English and French.

  • Firth, L. B., A. M. Knights, D. Bridger, et al. 2016. Ocean sprawl: Challenges and opportunities for biodiversity management in a changing world. Oceanography and Marine Biology: An Annual Review 54:189–262.

    This paper is a descriptive review of the extent of ocean sprawl with a comprehensive reference list of resources for the various types of ocean sprawl.

  • Gentry, R. R., H. E. Froehlich, D. Grimm, et al. 2017. Mapping the global potential for marine aquaculture. Nature Ecology & Evolution 1.9:1317–1324.

    DOI: 10.1038/s41559-017-0257-9

    This paper is a global analysis of coastal areas that are suitable for the development of aquaculture. The main paper provides some useful overview maps of regions suitable for finfish and bivalve aquaculture but importantly the supplementary material provides a breakdown of information by country (159 countries).

  • Keith, D. A., J. R. Ferrer-Paris, E. Nicholson, and R. T. Kingsford, eds. 2020. The IUCN Global Ecosystem Typology 2.0: Descriptive profiles for biomes and ecosystem functional groups. Gland, Switzerland: IUCN.

    This hierarchical classification system includes three artificial ecosystem functional groups within two anthropogenic biomes within marine and marine-terrestrial realms. For each ecosystem functional group, a description of the ecological traits, key ecological drivers, global distribution, and major references are given.

  • Lima, J. S., I. R. Zalmon, and M. Love. 2019. Overview and trends of ecological and socioeconomic research on artificial reefs. Marine Environmental Research 145:81–96.

    DOI: 10.1016/j.marenvres.2019.01.010

    This paper is a comprehensive global review of artificial reef research that included 620 studies from 1962 to 2018. The paper includes useful global maps and summary tables of the types of artificial reef studies by country, decade, and specific research focus.

  • National Oceanic and Atmospheric Administration (NOAA). 2012. NOAA’s State of the Coast.

    The State of the Coast website was launched by the United States National Oceanic and Atmospheric Administration in 2010. It contains quick facts and detailed statistics on communities, economy, ecology, and climate. When accessed in 2015, the website provided details of the relative percentage of the coastline of each coastal state that was artificial.

  • Parente, V., D. Ferreira, E. M. dos Santos, and E. Luczynski. 2006. Offshore decommissioning issues: Deductibility and transferability. Energy Policy 34.15:1992–2001.

    DOI: 10.1016/j.enpol.2005.02.008

    This paper provides a global overview and map of the distribution of offshore oil and gas structures.

  • Sengupta, D., R. Chen, and M. E. Meadows. 2018. Building beyond land: An overview of coastal land reclamation in 16 global megacities. Applied Geography 90:229–238.

    DOI: 10.1016/j.apgeog.2017.12.015

    This paper used remote sensing to evaluate the changing spatial extent of seaward land expansion of sixteen coastal megacities spanning all continents between the mid-1980s to 2018.

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