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. 2022 Nov 1;11(1):35.
doi: 10.1186/s13750-022-00285-9.

Evidence for the effects of decommissioning man-made structures on marine ecosystems globally: a systematic map

Anaëlle J Lemasson  1 , Paul J Somerfield  2 , Michaela Schratzberger  3 , Caroline Louise McNeill  2 , Joana Nunes  2 , Christine Pascoe  2 , Stephen C L Watson  2 , Murray S A Thompson  3 , Elena Couce  3 , Antony M Knights  4
Affiliations

Evidence for the effects of decommissioning man-made structures on marine ecosystems globally: a systematic map

Anaëlle J Lemasson et al. Environ Evid. .

Erratum in

Abstract

Background: Many marine man-made structures (MMS), such as oil and gas platforms or offshore wind turbines, are nearing their 'end-of-life' and require decommissioning. Limited understanding of MMS decommissioning effects currently restricts the consideration of alternative management possibilities, often leaving complete removal as the only option in certain parts of the world. This evidence-base describes the ecosystem effects of marine MMS whilst in place and following cessation of operations, with a view to informing decision-making related to their potential decommissioning.

Method: The protocol used to create this map was published a priori. Systematic searches of published, literature in English were conducted using three bibliographic databases, ten specialist organisational websites or repositories, and one search engine, up to early 2021. A total of 15,697 unique articles were identified as potentially relevant to our research questions, of which 2,230 were screened at the full-text level. Of that subset, 860 articles met all pre-defined eligibility criteria. A further 119 articles were identified through "snowballing" of references from literature reviews. The final database consists of 979 articles. For each article included, metadata were extracted for key variables of interest and coded into a database.

Review findings: The vast majority of eligible articles related to the presence of MMS (96.2%), while just 5.8% considered decommissioning. Overall, articles mainly considered artificial reefs (51.5% of all articles) but increasingly oil and gas (22%), shipwrecks (15.1%) and offshore wind (13.1%). Studies were distributed globally, but the majority focused on the United States, single countries within Europe, Australia, Brazil, China, and Israel; 25 studies spanned multiple countries. Consequently, the bulk of the studies focused on the North Atlantic (incl. Gulf of Mexico, North Sea, and Mediterranean Sea) and North Pacific Oceans. A further 12 studies had a global scope. Studies in majority reported on fish (53%) and invertebrates (41%), and were disproportionately focused on biological (81%) and ecological (48%) impacts. Physico-chemical (13%), habitat (7%), socio-cultural (7%), economic (4%) and functional (8%) outcomes have received less attention. The number of decommissioning studies has been increasing since ca. 2012 but remains noticeably low. Studies mostly focus on oil and gas infrastructures in the USA (Gulf of Mexico) and Northern Europe (North Sea), covering 9 different decommissioning options.

Conclusions: This systematic map, the first of its kind, reveals a substantial body of peer-reviewed evidence relating to the presence of MMS in the sea and their impacts, but with considerable bias toward biological and ecological outcomes over abiotic and socio-economic outcomes. The map reveals extremely limited direct evidence of decommissioning effects, likely driven at least in part by international policy preventing consideration of a range of decommissioning options beyond complete removal. Despite evidence of MMS impacts continuing to grow exponentially since the early 1970s, this map reveals key gaps in evidence to support best practice in developing decommissioning options that consider environmental, social and economic effects. Relevant evidence is required to generate greater understanding in those areas and ensure decommissioning options deliver optimal ecosystem outcomes.

Keywords: Artificial reefs; Marine renewable energy; North sea; Offshore wind; Oil and gas; Reefing; Repurposing; Synthesis.

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Conflict of interest statement

The authors declare having no competing interests.

Figures

Fig. 1
Fig. 1
ROSES flow diagram detailing the systematic mapping process
Fig. 2
Fig. 2
Count of articles over time for all MMS types (dotted line) and grouped by MMS type (coloured solid lines). Top: all MMS types and years. Bottom: close-up for the years 2000–2021 for selected MMS (oil and gas (O&G), offshore wind farms (OWF), and artificial reefs (AR)). Please note that the year 2021 was incomplete as searches ended in February 2021
Fig. 3
Fig. 3
Count of articles by MMS type. MREI: Marine renewable energy installation. MMS: Man-made structure. Data labels at end of bars are percentages of total articles (N = 979), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles, and percentages may add up to more than 100% as some articles contains studies spanning multiple MMS types
Fig. 4
Fig. 4
Geographical distribution of articles (by country), grouped by MMS type (excluding 25 ‘global or multiple countries’ studies not mapped here). The size of the pie chart is scaled relative to the number of articles associated with each country. Refer to Table 3 for details on the number of articles for each country
Fig. 5
Fig. 5
Geographical distribution of articles (by sea area), grouped by MMS type (excluding 12 ‘global’ studies and 2 ‘unclear or unspecified’ studies not mapped here). Sea areas represented: North Pacific Ocean, South Pacific Ocean, Arctic Ocean, North Atlantic Ocean (excl. Mediterranean Sea, excl. Baltic Sea), Baltic Sea, Mediterranean Sea, South Atlantic Ocean, Indian Ocean, Equatorial Pacific. Note that no studies were found for the Southern Ocean. The size of the pie chart is not scaled relative to the number of articles associated with each sea area. Refer to Table 4 for more details on the geographical spread of studies, by sea areas and sub-areas
Fig. 6
Fig. 6
Count of articles by Population—level 1 category. Data labels at end of bars are percentages of total articles (N = 979), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles, and percentages may add up to more than 100% as some articles contains studies spanning multiple Population categories
Fig. 7
Fig. 7
Count of articles by Population—level 2 categories. Data labels at end of bars are percentages of total articles (N = 979), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles (N = 979), and percentages may add up to more than 100%, as some articles contains studies spanning multiple Population—level 2 categories (e.g.: studies on both Fish and Invertebrates)
Fig. 8
Fig. 8
Count of articles by Outcome—level 1 category. Data labels at end of bars are percentages of total articles (N = 979), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles, and percentages may add up to more than 100% as some articles contains studies spanning multiple Outcome categories
Fig. 9
Fig. 9
Number of articles published per year on the effects of marine MMS, showing both all-Exposure types combined (black line) and articles specifically on decommissioning (orange line). Insert: Close-up for the years 1989–2021 on the number of articles on decommissioning of MMS. Please note the difference in vertical scale between the two graphs. Please note that the year 2021 was incomplete as searches ended in February
Fig. 10
Fig. 10
Count of articles on decommissioning by MMS type. NB: The total count of articles may be greater than the number of unique articles (N = 57), and percentages may add up to more than 100%, as some studies investigated more than one category of MMS
Fig. 11
Fig. 11
Count of articles on decommissioning grouped by decommissioning exposure option. Data labels at end of bars are percentages of total articles (N = 57), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles, and percentages may add up to more than 100%, as some studies investigated more than one option
Fig. 12
Fig. 12
Geographical distribution of articles on decommissioning (by sea area), grouped by MMS type (N = 57). Sea areas represented: North Pacific Ocean, North Atlantic Ocean (excl. Mediterranean Sea, excl. Baltic Sea), Mediterranean Sea,, South Atlantic Ocean, Indian Ocean, Equatorial Pacific. Note that no studies were found for the Arctic Ocean, the Baltic Sea, the Equatorial Atlantic, the South Pacific Ocean, and the Southern Ocean. The size of the pie chart is not scaled relative to the number of articles associated with each sea area. Refer to Table 11 for more details on the geographical spread of studies, by sea areas and sub-areas
Fig. 13
Fig. 13
Count of articles on decommissioning by Population—level 1 category. Data labels at end of bars are percentages of total articles (N = 57), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles, and percentages may add up to more than 100%, as some articles contains studies spanning multiple Population categories
Fig. 14
Fig. 14
Count of articles on decommissioning by Population—level 2 category. Data labels at end of bars are percentages of total articles (N = 57), followed by exact counts. NB: The total count of articles may be greater than the number of unique articles, and percentages may add up to more than 100%, as some articles contains studies spanning multiple Population—level 2 categories (e.g.: studies on both Fish and Invertebrates). Categories with a count of zero are based on categories found in other (non-decommissioning) articles included in the map
Fig. 15
Fig. 15
Count of articles on decommissioning by Outcome—level 1 category. Data labels at end of bars are percentages of total articles (N = 57), followed by exact counts. Percentages may add up to more than 100% as some articles contains studies spanning multiple Outcome categories
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