Coral reefs make up one of the most biodiverse and productive ecosystems on earth, covering an area of almost 300,000 km² and home to around one-third of all marine life. Reefs support people and the environment on a global scale, protecting against the effects of climate change while providing for the millions of people whose livelihoods depend on the fishing and tourism industry.
Image Credit: Andrey Armyagov/Shutterstock.com
Unfortunately, coral reefs worldwide are declining at an alarming rate due to the impacts of pollution, overfishing, and climate change – to the extent that 90% of reefs are projected to die by 2050.
What is Causing Coral Reef Decline?
Corals work in combination with algae called zooxanthellae to feed the reef. It is these algae living inside the coral tissue that are responsible for a reef’s striking colors.
The coral and algae exist in a fragile balance that is sensitive to fluctuations in water temperature, salinity, and pollution. Increases in the ocean surface temperature as a result of climate change can disrupt this balance, forcing the corals to expel the zooxanthellae and turn completely white.
When this ‘bleaching’ occurs, the corals do not die immediately. However, the longer they remain without the algae, the more susceptible to the impacts of environmental stressors such as storms and disease they become. These disturbances can further decrease the reef’s health and eventually result in loss of coral cover across large areas.
Why Does Ocean Acidification Occur?
Increasing levels of carbon dioxide in the ocean lower its pH, making it more acidic. This ocean acidification prevents corals from absorbing the calcium carbonate they require to maintain their skeletons, which can then dissolve. Without action being taken to reduce carbon dioxide emissions, ocean acidification will eventually become too intense and widespread for corals to survive.
The collapse of reef systems would result in a huge loss of marine biodiversity, unhealthy oceans, and economic disaster, particularly for people in developing countries.
Many conservation interventions are underway across the globe to respond to coral reef bleaching and degradation.
In addition to strategic reef conservation and restoration projects to enhance the long-term resilience of the reefs, some organizations are supporting efforts to reduce greenhouse gas emissions and limit the global temperature increase to less than 2 °C by the end of the 21st century.
Coral Reef Restoration Techniques
A wide range of coral reef restoration techniques and methods are available, many of them easy and cheap to construct and maintain. Generally, these techniques fall under two main types of restoration – active and passive.
Active restoration involves increasing coral abundance, biodiversity, and health to enhance a reef’s resilience and ability to recover from environmental stressors. Ideally, this type of restoration is carried out following passive restoration, which involves the creation of marine protected areas.
Some of the most commonly used coral reef restoration methods include:
Structural restoration – the construction of artificial reefs and the relocation of dead coral heads or rocks to increase the availability of reef structures for corals and other reef organisms to grow on.
Biological restoration – increasing the number of corals living in areas where structures are already available by rehabilitating broken coral fragments and planting living corals.
Physical restoration – improving the health, growth rates, and reproductive ability of corals by floating corals in mid-water and using mineral accretion devices to alter the water chemistry (such as pH) around reef structures.
The UN Decade on Ecosystem Restoration
In response to the critical need to reverse the degradation of ecosystems and recover biodiversity across the world, the United Nations (UN) announced the period 2021 to 2030 as the “UN Decade on Ecosystem Restoration.”
The International Coral Reef Initiative (ICRF) – a global partnership of governments and organizations that strives to preserve coral reefs – says:
“Coral reef restoration targets should be included in commitments made to the UN Decade on Ecosystem Restoration. Coral reef restoration efforts are now implemented in at least 56 countries around the world.”
3D-Printed Reef Tiles
The ICRF also points out that coral reef restoration is not a short-term fix for coral reef decline. Ecosystem restoration interventions need to be planned and funded as long-term strategies that can be applied over at least 10-20 years.
One such effort is the development of 3D-printed artificial reef tiles by archiREEF – a spin-out company from Hong Kong University that combines expertise in marine biology with 3D printing technologies to create artificial habitats for threatened marine life.
archiREEF says the ocean-friendly tiles use biomimicry to enhance the survival and growth of reefs and are four times more effective at keeping corals alive than conventional restoration methods.
Weighing just 10 kg, the 3D-printed reef tiles are designed to maximize modularity and scalability. They are produced using a computational algorithm that enables the generation of thousands of unique tiles that are adaptable to the particular corals that require protection.
3D printed tiles help revive coral beds in Hong Kong coastal waters
Video Credit: South China Morning Post/YouTube.com
Other Successful Reef Restoration Efforts
Other examples of successful projects include interventions launched by the Coral Restoration Foundation, which works to support the natural recovery of reefs by implementing large-scale cultivation, out-planting, and monitoring of diverse, reef-building corals.
The foundation developed a method for out-planting two species of reef-building coral – staghorn and elkhorn – and has so far planted more than 66,000 of these onto the Florida Reef Tract.
Another initiative is the Reef Restoration and Adaptation Program (RRAP), which brings together experts from the Australian Institute of Marine Science, the Great Barrier Reef Foundation, CSIRO, the University of Queensland, QUT, South Cross University, and James cook University in one of the world’s greatest efforts to help reefs survive climate change.
The RRAP’s Research and Development Program is a 10-year research initiative aiming to test innovative and cost-effective interventions to maintain the resilience and critical functions of the Great Barrier Reef.
“While RRAP is initially focused on developing technology and solutions to help the Great Barrier Reef, these solutions could also be applied to other reefs in Australia and around the world,” says the collaborative.
Future Challenges Faced in Reef Restoration
The ICRI says the challenges faced in coral reef restoration include a lack of integration with threat and disturbance abatement strategies, limited spatial scale for effective implementation, insufficient monitoring of effectiveness, and a lack of long-term stakeholder engagement.
The initiative’s recommendations for planning reef restoration projects over the next 10 years include the following:
- Incorporate threat and disturbance abatement strategies
- Include projections of climate change impacts and site vulnerabilities
- Consider disease prevalence, the physical integrity of reefs, and the connectivity of key species when choosing sites and methods
- Engage stakeholders and maximize socio-economic advantages for local communities
- Monitor projects to enable adaptive management and improved communication of outcomes.
References and Further Reading
Coral Bleaching and Reef Degradation. Conservation in a Changing Climate 2021. Available at: https://climatechange.lta.org/climate-impacts/coral-reef-degradation/
What Causes Reef Degradation? Reef Life foundation 2020. Available at: https://www.reeflifefoundation.org/post/what-causes-reef-degradation
Introduction to Coral Restoration. New Heaven Reef Conservation Program 2016. Available at: https://newheavenreefconservation.org/learning-resources/explore-topics/reef-restoration-methods
A global partnership for the preservation of the world’s coral reefs and associated ecosystems. International Coral Reef Initiative (ICRI) 2021. Available at: https://www.icriforum.org/
Coral Reef Restoration as a Strategy to Improve Ecosystem Services. ICRI 2020. Available at:https://www.icriforum.org/wp-content/uploads/2021/01/Hein-et-al.-2020_UNEP-report-1.pdf
Preventing, Halting and Reversing the Degradation of Ecosystems Worldwide. United Nations Decade on Ecosystem Restoration 2021 – 2030. Available at: https://www.decadeonrestoration.org/
Building Dynamic Ocean Ecosystems with Eco-engineering Technologies. archiREEF 2021. Available at: https://archireef.co/
Welcome to the Biggest Coral Reef Restoration Effort on the Planet. Coral Restoration Foundation 2020. Available at: https://www.coralrestoration.org/
Reef Restoration and Adaptation Program. Available at: https://gbrrestoration.org/
Coral Reef Restoration as a Strategy to Improve Ecosystem Services. Policy Brief. ICRI 2021. Available at: https://www.icriforum.org/wp-content/uploads/2021/01/Policy-brief.pdf