GBR Coral Restoration
GBR Coral Restoration
Best Practice Coral Restoration for the Great Barrier Reef

CORAL RESTORATION DATABASE

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Background

Coral reef ecosystems have suffered an unprecedented loss of habitat-forming hard corals in recent decades. While marine conservation has historically focused on passive habitat protection, demand for and interest in active restoration has been growing in recent decades. However, a disconnect between coral restoration practitioners, coral reef managers and scientists has resulted in a disjointed field where it is difficult to gain an overview of existing knowledge. To mitigate this, we synthesised the available knowledge of coral restoration methods in a review paper, incorporating data from the peer-reviewed scientific literature, complemented with grey literature and a survey of coral restoration practitioners.

In this review we describe coral restoration projects throughout the tropics, with a surprising diversity of coral species and morphologies used. While few projects report on ecological success, we present substantial evidence of the abilities to grow corals at smaller scales. We further describe common problems and issues that have plagued the field, and provide suggestions and recommendations for future coral restoration projects worldwide. This review presents the most comprehensive summary of active coral restoration methods to date, and we hope it will be a valuable resource for coral reef scientists worldwide.

However, we are also committed to ensure that the information gathered in this review reaches further than just traditional scientific academia, and are therefore dedicated to open access publication and data sharing. For this reason we have produced an interactive online data visualisation which interrogates the database underpinning the review. We have also made all of our data available from Dryad Data repository. Combined, these three outputs (review, database and visualisation) establish a baseline of the current state of knowledge of global restoration approaches, to inform future research directions and improve restoration on coral reefs. 

Access them here:

Note that the review and database are still undergoing peer-review. We will update these links as soon as they are available online.


 METHODS

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 Methods

We assembled case studies and descriptions of coral restoration methods from four sources: 1) the primary literature (i.e. published peer-reviewed scientific literature), 2) grey literature (e.g. scientific reports and technical summaries from experts in the field), 3) online descriptions (e.g. blogs and online videos describing projects), and 4) an online survey targeting restoration practitioners. We included only those case studies which actively conducted coral restoration (i.e. at least one stage of scleractinian coral life-history was involved). This excludes indirect coral restoration projects, such as disturbance mitigation (e.g. predator removal, disease control etc.) and passive restoration interventions (e.g. enforcement of control against dynamite fishing or water quality improvement). It also excludes many artificial reefs, in particular if the aim was fisheries enhancement (i.e. fish aggregation devices), and if corals were not included in the method. To the best of our abilities, we avoided duplication of case studies across the four separate sources, so that each case in our review and database represents a separate project.

Defining restoration

The Society for Ecological Restoration International Science & Policy Working Group defines restoration as “the process of assisting the recovery of an ecosystem that has been degraded, damaged, or destroyed”. Further, “restoration attempts to return an ecosystem to its historic trajectory”. Restoration projects ideally require no attendance once they are mature. Currently for coral reefs, the term restoration is used to encompass both ‘restoration’ and ‘rehabilitation’; with the latter emphasising “the reparation of ecosystem processes, productivity and services…” without meaning a return to pre-existing biotic conditions, and often requiring some attendance. A restored ecosystem“contains sufficient biotic and abiotic resources to continue its development without further assistance or subsidy”.

 These definitions highlight one of the fundamental disconnects between the field of ecological restoration, developed largely in the terrestrial realm, and coral restoration. The International Principles and Standards for the Practice of Ecological Restoration promote the use of a reference ecosystem as a model or target used to assess progress toward restoration of a local ecosystem. While recovery of endangered species (e.g. the Acropora sp.) does not fit this view of ecological restoration it has driven the development of one important technique used in coral reef restoration and is included in this review. The confounding of the aims of a project and monitoring to document successful endangered species recovery versus coral reef restoration is one source of confusion that complicates a review of the field.

Restoration can be passive or active, whereby passive restoration (also ‘natural regeneration’ or ‘indirect restoration’) “relies on increases in individuals, without direct planting or seeding, after the removal of causal factors alone”, while active restoration(also ’direct restoration’, and often shortened to just ‘restoration’) relies on reintroductions or augmentations. Broadly speaking, these two types of restoration also correspond to the level of degradation sustained by the environment, where passive restoration can be applied to sites with less damage, and active restoration is considered necessary in areas where unassisted natural recovery is unlikely. Finally, an intervention is the action undertaken to achieve restoration, such as substratum amendment, exotics control, habitat conditioning, reintroductions”. 

 OUTCOMES

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A summary of the main techniques covered in the review and the average survival reported in those projects. Figure taken from review [citation]

A summary of the main techniques covered in the review and the average survival reported in those projects. Figure taken from review [citation]

Conclusions 

  1. On average, survival in restored corals is relatively high. All coral genera with sufficient replication from which to draw conclusions (>10 studies listing that genus) report an average survival between 60-70%.

  2. Differences in survival and growth are largely species and/or location specific, so the selection of specific methods should be tailored to the local conditions, costs, availability of materials, and to the specific objectives of each project.

  3. Projects are overall small and short, however substantial scaling up is required for restoration to be a useful tool in supporting the persistence of reefs in the future. While there is ample evidence detailing how to successfully grow corals at smaller scales, few interventions demonstrate a capacity to be scaled up much beyond one hectare. Notable exceptions include methods which propagate sexually derived coral larvae.

  4. To date, coral restoration has been plagued by the same common problems as ecological restoration in other ecosystems. Mitigating these will be crucial to successfully scale up projects, and to retain public trust in restoration as a tool for resilience based management.

    • Lack of clear objectives - There is a clear mismatch between the stated objectives of projects, and the design of projects and monitoring of outcomes. Poorly articulated or overinflated objectives risk alienating the general public and scientists, by over-promising and under-delivering. Social and economic objectives have inherent value and do not need to be disguised with ecological objectives.

    • Lack of appropriate monitoring - A large proportion of projects do not monitor metrics relevant to their stated objectives, or do not continue monitoring for long enough to provide meaningful estimates of success. Further, there is a clear need for standardisation in the metrics that are used, to allow comparisons between projects.

    • Lack of appropriate reporting - The outcomes of a large proportion of projects are not documented, which restricts knowledge-sharing and adaptive learning. While we attempted to access some of the unreported projects through our survey, it is clear we have only scratched the surface of existing knowledge.

    • Poorly designed projects - An effect of inadequate monitoring and reporting is that projects are poorly suited to their specific area and conditions. Improved knowledge-sharing and development of best practice coral restoration guidelines aims to mitigate this problem.

Note that the review and database are still undergoing peer-review. We will update these links as soon as they are available online.

Citation:

If you end up using data from these three sources, please cite as follows:

Database and visualisation: Boström-Einarsson L, Daniella C, Nathan C, Hein M, Smith A, McLeod IM. (2019). Data from: Coral restoration - A systematic review of successes, failures and future directions. Dryad Digital Repository. doi:10.5061/dryad.p6r3816

Review: Boström-Einarsson L, Babcock RC, Bayraktarov E, Daniella C, Nathan C, Ferse SCA, Harrison P, Hein M, Shaver E, Smith A, Stewart-Sinclair PJ, Vardi T, McLeod IM. (2019). Coral restoration - A systematic review of successes, failures and future directions. Journal Name, Issue, DOI

Note that the review and database are still undergoing peer-review. We will update these references as soon as they are available online.