Is there a future for Coral Reefs?

27 April 2023

Written by: Ariane Kaploun, ,

An article written in collaboration with:

Christelle Castet, Head of Science

Ana Pachon, Marketing and Communications manager

Amélie Bonifacj, Marketing and Communications officer

Coral reefs provide enormous economic and protective benefits, estimated at up to USD 1.1 billion per year. 1 billion people are highly dependent on coral reefs for food, coastal protection, and income. Ocean warming and acidification, lasting unsustainable practices, pollution, increased hurricane frequency… the list of threats to coral reefs seems endless.

What is really happening regarding coral threats? And how can we act?

Coral reefs are facing increased pressure due to acute climate events

Human induced climate change increases the intensity and frequency of extreme climate events across the world, impacting both people and ecosystems. Amongst these extreme events, tropical cyclones are one of the most destructive, causing more than half of the total damage attributed to billion-dollar climate disasters since 1980 in the US alone (1).

Coral reefs are on the front line as hurricanes generate a strong swell that breaks the reef’s limestone structure. This, in turn, generates fragments which leads to cloudy waters. As sediment settles on the coral, it causes the colony’s death – or necrosis. This phenomenon leads to a loss of 17% (2) of coral cover one year on average after a hurricane in the Caribbean.

This growing threat for reefs is illustrated by recent storms Ian and Lisa, which formed at the end of September and October 2022. These two events occurred at the end of the Atlantic hurricane season (3), which usually runs from June to November. Both were unique, with Ian being the fourth strongest (4),  hurricane on record to reach west Florida and Lisa being the first hurricane,  to make landfall in Belize during November since 1942 (5).

These hurricanes had a significant impact on the coasts where they made landfall. Ian destroyed several manmade reefs that were part of ongoing restoration programs throughout southwest Florida,  aiming at restoring the 90% loss (6) of corals the area had seen over recent decades. Lisa also damaged several natural reefs including some of a marine protected area in the region. 

Research projects focused on studying reef resilience to hurricane damages, such as Project Reefense, which uses giant pools to simulate storm surge on artificial reefs, are paving the way for innovation in artificial reef structures. These structures aim to help corals grow more robustly and reduce the damages caused by hurricanes. Multiple studies have demonstrated the capacity of coral reefs to reduce coastal flooding, making it essential to maintain and develop these ecosystems with structures that can be strengthened with human assistance.

Chronic and rapide warming: a real challenge for reef adaptation strategies


Changes in tropical cyclones under a +2°C global warming

Figure 1: Changes in tropical cyclones under a +2°C global warming: total frequency, frequency of the most intense tropical cyclones (of category 4 and 5), intensity, and rainfall (7).

Unfortunately, hurricanes are not the only expression of the climate threat to coral reefs. Two other major concerns are marine heat waves and acidification, both of which amplified by climate change and causing a cascade of adverse effects on marine ecosystems.

Indeed, ocean temperature is a vital component of the Earth’s climate system. Over recent decades, increasing frequency, intensity, and duration of marine heat waves have been observed and directly linked to climate change. This trend has been recorded in all major ocean basins, impacting all oceans and a range of species throughout the ecosystems (8).

According to an IPCC special report (9), a 1.5°C increase in ocean temperatures over the next 100 years could cause the disappearance of 70 % to 90 % of the world’s coral reefs. An increase of 2°C could induce a complete loss.


Summary of prominent recent marine heat waves

Figure 2: Summary of prominent recent marine heat waves, International MHW working group (10)

Additionally, oceans absorb around 25% of global carbon emissions – as emissions increase, so does carbon absorption. This massive absorption disrupts the natural chemical balance of water, causing it to become more acidic. Above a certain threshold, reefs cease to grow, and further acidification dissolves the calcium carbonate that constitutes the structure of the reef. Already, ocean acidity has increased by 30% (12) compared to pre-industrial times.

Both marine heatwaves and ocean acidification cause coral bleaching, when corals eject microalgae in an attempt to limit damage (13) from excess oxygen production and coral tissue damage. This phenomenon reduces the coral’s resiliency, and often leads to coral death. In 2016, bleaching affected 90% of the Great Barrier Reef in Australia (14)


Aerial surveys of the widespread and severe bleaching of Australia’s Great Barrier Reef

Figure 3: Aerial surveys of the widespread and severe bleaching of Australia’s Great Barrier Reef (11)

Ocean acidification is one of the nine planetary boundaries that regulates the stability of Earth’s ecosystems and allows humans to continue to develop and survive on this planet. Crossing critical thresholds in each boundary creates large-scale and potentially irreversible changes. For ocean acidification, this boundary is 80% pre-industrial aragonite saturation. (15)

Another direct consequence of acidification is the proliferation of invasive species harmful to coral reefs. For example, crown-of-thorn starfish – a coral-eating starfish whose reproduction seems to accelerate with acid water – is responsible for nearly half (16) of the Great Barrier Reef’s decline between 1985-2012.

The challenge lies in the speed of change that does not allow reefs to adapt quickly enough to these accelerating chronic phenomena. However, it’s important to remember that the evolution of the biosphere is a wonderful proof of nature’s adaptation and that no artificial structure will be able to adapt as efficiently as living structures. Therefore, reefs need a helping hand to keep pace. Examples of coral nurseries testing the temperature resistance of different species and replanting only the most resilient are becoming more common. By contributing to these efforts, we can help reefs adapt to the effects of climate change.

Reversing a negative trend: limiting unsustainable human activities

As most corals are situated in coastal areas, they are directly impacted by pollution and hurtful practices produced by human activities, whether it is pesticides leaking from cultivated lands, plastics and waste from hotels, industrialized aquaculture with its chemical intrants, or destructive fishing methods such as dynamite fishing.

In the famous Coral Triangle situated in Southeast Asia, a potent combination of plastic pollution and overfishing is altering reef dynamics and death rates of corals skyrocket: corals are suffocating or being punctured and deprived of sunlight and nutrients. In the region, it is estimated than 95% of reefs are endangered. (8)

Coral reefs have developed over billions of years to be resilient, yet as their living environment is becoming inhospitable due to human actions. Protecting and rebuilding these natural systems will protect human livelihoods and economies as the climate changes.

According to the Marine Conservation Institute, only 8,1% of the world’s oceans is covered by some form of marine protection (16). With the global objective to protect 30% of the ocean by 2030 – reinforced by the COP15 targets, the deployment of efficient Marine Protected Areas (MPAs) is a solution that should accelerate coral reefs protection and install more regulation. 

Marine Protected Area Zones all over the world

Figure 4: Marine Protected Area Zones all over the world (17)

Marine Protected Areas can address the triple nexus of biodiversity, climate, and social challenges with the purpose of reducing damages from unsustainable activities and pollution, as well as encouraging long-term sustainable practices and economic activities that benefit local communities.

Learn more about: COP 15 and the historic agreement to protect biodiversity and accelerate coral protection.

After almost two weeks of negotiations in Montreal, representatives of 188 governments approved a set of measures and targets to protect biodiversity. These measures are encapsulated in the conference’s culminating agreement, the Global Biodiversity Framework (GBF). The GBF sets out 23 targets to achieve by 2030, along with four overarching goals:

  • End human caused extinction of threatened species and slow the extinction rate of all species tenfold by 2050.
  • Sustainable use and management of biodiversity to ensure ecosystem services are available and valued by future generations.
  • Equitable sharing of monetary and non-monetary benefits derived from genetic resources.
  • Provide adequate access and resources so that all parties involved in GBF can implement the framework, including closing the biodiversity finance gap of USD 700 billion annually.

What actions can we take to protect coral reefs?

Limiting global warming is an obvious priority to maintain coral reefs in the long term. It is worth reminding once again that reducing CO2 emissions directly affects the climate and impacts coral survival.

Encourage science and data to accelerate restoration

Active restoration techniques are currently under development to make restoration programs more effective. For instance, coral nurseries provide the possibility to test the reaction of different coral species to increased temperature, and to replant reefs with heat-resistant species – improving reef resiliency. New techniques, such as artificial reefs with sustainable components, electrified water tables, and underwater tree-like structures are also being developed and tested all over the world to facilitate coral restoration.

In 2010, the Oli cyclone devastated the reefs surrounding Moorea in French Polynesia. These reefs had already been weakened by the predator crown-of-thorn starfish, and the proportion of hard coral had dropped from 50% to near 0%. However today, parts of these reefs have now been restored by introducing new coral larvae and remodeling the dead skeletons with pieces of surviving coral tissue (18).

Coral restoration

Figure 5: Okinawa artificial coral reef (image source: Picasa)

Finally, data (from satellites, buoys, sensors, etc.) and innovative research such as e-DNA make it possible to develop monitoring tools that anticipate pending threats and facilitate a quick reaction from conservationists to limit the damage.

De-risk the investment in coral reefs protection and MPAs

One of the recurring challenges in financing nature conservation is the lack of a tangible return on investment. However, coral reefs and marine protected areas (MPAs) can generate revenue and be perceived as bankable investments. This financial return primarily comes from the leisure industry, with entrance fees charged to tourism stakeholders such as diving centers, recreational fishing companies, and hotels, as well as coastal industries benefitting from a healthy reef, such as professional fisheries and aquaculture. Encouraging a sustainable local economy around MPAs through eco-tourism or sustainable coastal activities can generate alternative jobs and engage local communities in reef protection efforts.

Efficient protective programs need financing to succeed in managing the area. If sustainable finance encounters a significant acceleration, the risks (perceived or real) for financiers to invest in nature-based projects remain high: lack of revenues, lack of transparency, lack of scalability and replicability… And lack of trust between these two domains that have been considered far from each other for years.

Risk-transfer solutions like insurance are a convincing way to secure investment and support coral reef resiliency as climate change progresses. Although still a nascent area, examples of nature-based insurance solutions have been growing in recent years. These solutions provide financial compensation or reimbursement against losses derived from damage to a natural asset – such as mangroves, coral reefs, forests, or other natural structures – based on predetermined risks coverage limits, allowing natural assets to be treated like engineered assets.

Organizations such as the MarFund or Blue Finance are now using parametric insurance to trigger fast community-led restorations in the Mesoamerican reef after hurricanes.  Quick response helps fix damaged reefs, redeveloping their resiliency before the next storm event. This ensures that climate disasters do not wipe out the millions invested in reef protection.

Additionally, the use of parametric strategies offers the possibility to go even further. With a climate-risk index insurance, the pay-out can also cover the business interruption of related activities contributing to the ecosystem’s protection, creating a combined interest between local livelihoods and a restored reef.

Learn more about: The importance of coral reefs for humanity and biodiversity

Previously the prerogative of economists, the science of calculating the value of natural ecosystems is increasingly considered an efficient means to convince decision-makers about the importance of protecting natural resources. While turning an ecosystem into an asset with an economic value might lack poetry, the exercise with corals is very revealing: tourism, fishery, flood risk-reduction capacity … the benefits are exponential.

Coral reefs are estimated to provide ecosystem services worth USD 6 trillion annually and support 1 billion people across the globe. This partially comes from the fact that they are some of the most diverse marine ecosystems – they support 25% of all marine species. Additionally, their high diversity plays a critical role in medical research and development.

In terms of flood protection, healthy reefs reduce the destructive power of waves by 97 % (2) and provide over 600 million people with coastal protection against floods. Coastal flooding already causes damages in excess of USD 40 billion a year, and this is expected to increase to USD 1 trillion by 2050. On a global scale, if reefs disappeared, damage from 100-year storm events would increase by 91% and cost USD 272 billion. (19)

Healthy coral reefs are also critical for food supply and provide an average (20) of 15 tons of fish per square kilometer. This supports the livelihood of 6 million fishers and provides food for nearly 1 billion people.  

Furthermore, tourism associated with reefs adds USD 36 billion (21) annually to the global economy and supports millions of jobs. Out of the 96 countries (22) that have a reef tourism industry, 23 rely on the industry for over 15% of their GDP.

With 10% of the world’s population living within 100 kilometers of a coral reef – 75% of which are from developing countries, protecting them is critical.

For more information, contact Ariane Kaploun, ,

View references
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  3. National Oceanic and Atmospheric Administration (NOAA). (n.d.). Tropical Cyclone Climatology.  
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  15. Earth Has Crossed Several “Planetary Boundaries,” Thresholds of Human-Induced Environmental Changes. (2015, January 15). Scripps Institution of Oceanography.  
  16. Great Barrier Reef has lost half of its coral in the last 27 years. (2012, October 12). ScienceDaily.  
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  18. Cyclone Oli deals major blow to French Polynesia’s coral reefs. (2010, March 10). ScienceDaily.  
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