What is Currently Being Done?
While marine conservation has historically focused on passive habitat protection, demand for and interest in active restoration has been growing. To gain an overview of existing knowledge and restoration projects to date, Boström-Einarsson and colleaguesref assembled and synthesized lessons learned from 329 case studies and descriptions of coral restoration projects around the world from peer-reviewed scientific literature, grey literature, online descriptions, and an online survey of restoration practitioners. This review establishes a baseline of the current state of knowledge of coral reef restoration approaches and identifies areas for improvements for the field.
Below is a visualization you can use to scroll through the findings of this review.
Click on the tabs below to see a summary of findings and recommendations.
Results of the review include ref:
- 10 coral restoration intervention types were identified, with direct transplantation and coral gardening being the most common methods. Other interventions included: artificial reefs, substrate enhancement with electricity, substrate stabilization (4%), algae removal, larval enhancement, and micro-fragmentation.
- Restoration projects are occurring in 52 countries around the world. The majority of projects were conducted in the USA, Philippines, Thailand and Indonesia (together representing 40% of projects).
- Coral restoration case studies are dominated by short-term projects, with the median length of 12months and 66% of projects reporting monitoring for 18 months or less.
- Most projects are relatively small in spatial scale, with a median size of restored area of 500
- A diverse range of species are being restored, with 221 different species from 89 genera. Most restoration projects (65% of studies) focused on fast-growing branching corals, and the top five species (22% of studies) were Acropora cervicornis, Pocillopora damicornis, Stylophora pistillata, Porites cylindrica and Acropora palmata.
Conclusions from the review include ref:
- On average, short-term 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%.
- 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 specific objectives of each project.
- 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 (or 10,000 square meters). Notable exceptions include methods which propagate sexually derived coral larvae.
Below is a list of common problems and recommendations for restoration projects ref. Mitigating these problems will help scale up restoration and maximize its potential use within resilience-based management frameworks.
- Develop clear goals and opens in a new windowobjectives – Many projects have a mismatch between stated goals or objectives and the design of projects and monitoring of outcomes. Poorly articulated or overinflated objectives risk alienating stakeholder groups, by over-promising and under-delivering. Social and economic objectives have inherent value and do not need to be disguised with ecological objectives.
- Conduct appropriate monitoring – A large proportion of projects do not monitor metrics relevant to their stated goals and objectives, and/or do not continue monitoring for long enough to provide meaningful estimates of success. Use standardized metrics where possible to allow comparisons between projects.
- Report project results – The outcomes of a large proportion of projects are not documented, which restricts knowledge-sharing and adaptive learning. It is important to share successes as well as failures, so others can learn from your experiences and do not repeatedly try methods that are not successful.
- Carefully plan and design your project – Due to inadequate monitoring and reporting, projects often use methods that are poorly suited to their specific area and conditions. Improved knowledge-sharing and development of best practice coral restoration guidelines aim to mitigate this problem.
The results of this study are highlighted in the infographic below.